Search Results for ionisers

Are your Ionisers working correctly?

The best way to keep electrostatic sensitive devices (ESDs) from damage is to ground all conductive objects and remove insulators from your ESD Protected Area (EPA). This is not always possible because some insulators are “process-essential” and are necessary to build or assemble the finished product. The only way to control charges on these necessary non-conductive items is the use of ionisation systems.
However, if an ioniser is out of balance, instead of neutralising charges, it will produce primarily positive or negative ions. This results in placing an electrostatic charge on items that are not grounded, potentially discharging and causing ESD damage to nearby sensitive items.
It is therefore essential to regularly clean ionisers and verify their functionality. Below we have put together a list of tasks that need to be performed with ionisers on a regular basis.

Maintenance
All ionization devices will require periodic maintenance for proper operation. Maintenance intervals for ionizers vary widely depending on the type of ionization equipment and use environment. Critical clean room uses will generally require more frequent attention. It is important to set-up a routine schedule for ionizer service. Routine service is typically required to meet quality audit requirements.” (User Guide CLC/TR 61340-5-2 clause 4.7.6.7 Maintenance and cleaning)
EIA-625, recommends checking ionisers every 6 months, but this may not be suitable for many programs particularly since an out-of-balance may exist for months before it is checked again. EN 61340-5-1 clause 5.2.4 Compliance Verification Plan  states: “Process monitoring (measurements) shall be conducted in accordance with a compliance verification plan that identifies the technical requirements to be verified, the measurement limits and the frequency at which those verifications shall occur.
Under normal conditions, an ioniser will attract dirt and dust (especially on the emitter points). To maintain optimum neutralisation efficiency and operation, cleaning should be performed on a regular basis.

1. Case
Wipe the case with a soft cloth and deionised water. Fully squeeze the wiping cloth or sponge to remove any excess liquid. If a stronger cleaning solution is required, dab a soft cloth with mixture of isopropyl alcohol and deionised water (70% IPA and 30% DI water).

2. Emitter Points
The emitter points should be cleaned using specific emitter point cleaners or a swab dampened with Isopropyl alcohol. Below are general instructions on how to clean emitter points. However, each unit is slightly different so always refer to the ioniser’s manual.

  • Turn the unit OFF and unplug the power cord.
  • Open the top screen by loosening the screw and swinging the grill to one side.
  • Clean the emitter points using an emitter point cleaner or a swab dampened with Isopropyl alcohol.
  • Re-attach the top screen.
  • Plug in the power cord and turn the unit ON.

Verify the performance of the ioniser by using a charged plate monitor or ionisation test kit (see below).

Cleaning of Emitter Points using SCS 9110-NO as an exampleCleaning of Emitter Points using SCS 9110-NO as an example

With normal handling, the emitter points should not require replacement during the life of the unit.

Verification
EN 61340-4-7 provides test methods and procedures for evaluating and selecting air ionisation equipment. It is recommended to measure the offset voltage and discharge times, clean the unit, including emitter points and air filters if present, offset the voltage to zero (if adjustable), and then repeat offset voltage and discharge time testing. Should the unit not meet offset voltage specifications or minimum established discharge time limits, further service is required. Manufacturers should provide details on service procedures and typical service intervals.
Most companies will assign a number or otherwise identify each ioniser and setup a Compliance Verification / Maintenance / Calibration schedule. If the ionisers all test good, the data can justify lengthening the calibration period. If ionisers require adjustment, the calibration period should be shortened.

Verification should be performed in accordance with EN 61340-4-7.
Below are general instructions on how to verify your ioniser’s offset voltage and discharge time. Always refer to the User Guide accompanying your charge plate monitor or ionisation test kit for proper operation and setup.

1. Testing Ioniser Offset Voltage:
The required limit per EN 61340-5-1 is less than ± 35 volts. Check your ioniser’s operating manual or consult with the ioniser manufacturer to determine what the offset voltage should be for your ioniser.

Charge Plate Monitor (CPM)

  • Position the ioniser and charge plate monitor as shown below.
  • Set the CPM to Decay/Offset mode.
  • Set the CPM to decay and offset voltage mode with a starting charge at either + or – 1 KV and a stopping charge at either + or -100 Volts.
  • Start the decay/offset test sequence on the CPM. This will take a few seconds.
  • Record the decay time, and offset voltage as displayed on the CPM.

Positioning your Charge Plate Monitor for Overhead and Benchtop Ionisers

Ionisation Test Kit

  • Zero the charge plate by touching it with a grounded object. This can either be the finger of a grounded person or some other item which is connected to electrical ground. In either case, zeroing the charge plate should make the display on the field meter read zero.
  • Hold the meter approximately one foot (30.5 cm) in front of the ioniser.
  • Monitor the display. The value displayed is the offset balance of the ioniser, which is the difference between the number of positive and negative ions being emitted.

Auditing ionisation equipment with the Digital Static Field Meter and Conductive PlateAuditing ionisation equipment with the Digital Static Field Meter and Conductive Plate

2. Testing Ioniser Discharge Time:
The required limit per EN 61340-5-1 is “(1 000 V to 100 V and –1 000 V to –100 V) < 20 s or user defined”. Please refer to the ioniser’s operating manual or consult with the ioniser manufacturer to determine what this discharge time should be.

Charge Plate Monitor (CPM)

  • Set the CPM to Decay/Offset mode.
  • Set the CPM to decay and offset voltage mode with a starting charge at either + or – 1 KV and a stopping charge at either + or -100 Volts.
  • Start the decay/offset test sequence on the CPM. This will take a few seconds.
  • Record the decay time, and offset voltage as displayed on the CPM.

Ionisation Test Kit

  • After charging the plate of the ionisation test kit, hold the field meter approximately one foot (30.5 cm) away from the ioniser.
  • Monitor the display of the meter to see how quickly the 1.1 kV charge is dissipated to 0.1 kV.
  • The speed at which this occurs (the discharge time) indicates how well the ioniser is operating.
  • Repeat this procedure for both a positively and a negatively charged plate.

Some ionisers offer adjustment options (e.g. trim pots) which allow modification of the offset voltage.
However, if your ioniser is out of balance (and cannot be adjusted) or if the discharge time is out of specification, the ioniser will require service/repair by an authorised company.

Conclusion
Ionisation is one of the best methods of removing charges from insulators and as a result plays an important role in controlling ESD.
Remember though: ionisers require periodic cleaning of emitter pins and verifying of the offset voltage and discharge time. Otherwise, instead of neutralising charges, the ioniser will primarily produce positive or negative ions. The ioniser will therefore place an electrostatic charge on items that are not grounded, potentially discharging and causing ESD damage to nearby sensitive items.

How does Ionisation fit into an ESD Control Programme?

Setting up an ESD-safe workstation is often more challenging than it first appears. There are many methods of controlling ElectroStatic Discharge (ESD), and typically, it requires a combination of these to curb all static problems. Unfortunately, there is no single method that will fill all requirements.

Wrist straps and work surface mats are probably the most familiar to everyone, draining charges from operators as well as from the product being worked on. But what if the static charge in question is on an insulator? Electronic products, by nature, will normally consist of conductors and insulators. Insulators at the workstation can be found on the product itself, tools being used, tapes for masking, even circuit boards. A static charge on an insulator cannot be drained by grounding, as you could with a conductive material.

Ionisation
To effectively remove charges from insulators, we need to make the surrounding air more conductive. We have all seen a balloon cling to a wall because of a static charge, and we know that, after a period of time, it will drop. That is because the air is somewhat conductive and the charge eventually drains off. The problem with this concept is that it takes too long. The more conductive the air is, the faster the charge will be neutralised.

A balloon “stuck” on a wall by static charge.A balloon “stuck” on a wall by static charge.

The method most frequently used to increase the conductivity of the air is ionisation.
Ionisers are useful in preventing electrostatic charge generation, ElectroStatic Discharge, ElectroStatic Attraction, as well as preventing equipment latch-up. EN 61340-5-1 clause 5.3.4.2 Insulators states: “If the measured electrostatic field or surface potential exceeds the stated limits, ionization or other charge mitigating techniques shall be used.

How do Ionisers work?
Most ESD workstations will have some insulators (e.g. product plastic housing) or isolated conductors (e.g. PCB board components not in contact with ESD worksurface) that cannot be removed or replaced. These should be controlled using ionisation.

Ionisers create great numbers of positively and negatively charged ions. Fans help the ions flow over the work area. If there is a static charge present on an item in the work area, it will be reduced and neutralised by attracting opposite polarity charges from the air.
Ionisation can neutralise static charges on an insulator in a matter of seconds, thereby reducing their potential to cause ESD damage.

Electronic enclosures are process-essential insulatorsElectronic enclosures are process-essential insulators.

The charged ions created by an ioniser will:

  • neutralise charges on process required insulators,
  • neutralise charges on non-essential insulators,
  • neutralise isolated conductors and
  • minimise triboelectric charging.

How does Ionisation fit into an ESD Control Programme?
Ionisation is just one component of your ESD Control Programme. Before utilising ionisation, you should follow the fundamental principles of ESD Control:

  • Ground all conductors (including people) using conventional grounding methods (e.g. wrist straps or footwear/flooring system).
  • Remove all insulators, e.g. coffee cups, food wrappers etc.

“Air ionization is not a replacement for grounding methods. It is one component of a complete static control program. Ionizers are used when it is not possible to properly ground everything and as backup to other static control methods. In clean rooms, air ionization may be one of the few methods of static control available.” (User Guide CLC/TR 61340-5-2 clause 4.7.6 Ionization)

  • Ionisers can be critical to reduce induction charging caused by process necessary insulators
  • Ionisers can be critical in eliminating charges on isolated conductors like devices on PCBs
  • Ionisation can reduce ElectroStatic Attraction (ESA) and charged particles clinging and contaminating products.

The SCS Ioniser 9110-NO in use.The SCS Ioniser 9110-NO in use.

It is recommended to use ionisers with feedback mechanisms, so you’re notified if the offset voltage is out of balance.
Ionisers should be pieces of equipment that have serial numbers and are included in the company’s maintenance and calibration schedules. This is particularly critical to ensure that the offset voltage or balance is within acceptable limits. Otherwise, instead of neutralising charges the out of balance ioniser will charge insulators and isolated conductors. The user, depending on the value and function of their products, must determine the appropriate frequency of maintenance and calibration.

Summary
The best way to keep electrostatic sensitive devices (ESDs) from damage is to ground all conductive objects and remove insulators. This is not always possible because some insulators are “process-essential” and are necessary to build or assemble the finished product. The only way to control charges on these necessary non-conductive items is the use of ionisation systems. Applications include:

  • eliminating charges on process essential insulators,
  • neutralising workstations where ESDS are handled,
  • removing charged particulates to create a static free work area.

For more information and to select the right ioniser for your application, check out our Ioniser Selection Guide.

Internet of Things (IoT) in ESD Control

In today’s connected world, we are surrounded by home monitoring networks, fitness trackers and other smart systems. They all use an IoT platform to keep us up to-date with the current temperature in our house or the number of steps we have taken in a day. Is there a way to use this incredibly smart technology to improve ESD Control? Let’s take a look!

1. Internet of Things (IoT)
The Internet of Things (IoT):

  • Connects “things” in the physical world to the internet using sensors.
  • Collects data for these “things” via sensors.
  • Analyses the collected data and provides a deeper insight into the “things”.

This is a very broad and vague definition but then IoT is used everywhere today – from medical devices to vehicles, homes etc.
The Internet of Things (IoT) is the network of physical devices, vehicles, home appliances, and other items embedded with electronics, software, sensors, actuators, and connectivity which enables these things to connect and exchange data, creating opportunities for more direct integration of the physical world into computer-based systems, resulting in efficiency improvements, economic benefits, and reduced human exertions.” [Source]

The history of IoTThe history of IoT [Source]

The Industrial Internet of Things (IIoT) applies specifically to manufacturing and industrial processes.
It has slightly different requirements compared to consumer IoT products but the principle is the same: smart machines (incorporating various sensors) accurately and consistently capture and analyse real-time data allowing companies to pick-up problems as soon as (or even before) they appear.

2. Industry 4.0
IoT helped push the 3rd industrial revolution (machine automation) one step further. “Cyber Physical Systems (CPS) dominate the manufacturing floor, linking real objects with information processing, and virtual objects via the internet. The goal is to converge Operational Technology (OT) and Information Technology (IT).” [Source]
The 4th industrial revolution is also referred to as “Industry 4.0”. “At the very core Industry 4.0 includes the (partial) transfer of autonomy and autonomous decisions to cyber-physical systems and machines, leveraging information systems”. [Source]

Industry-4.0-shutterstock_524444866_pk_cutIndustry 4.0 as fourth industrial revolution [Source]

So, how can companies use the power of IoT and create accessible, real-time feedback on the status of their ESD Control Protected Area (EPA) and ESD control items?

3. IoT in ESD Control
ESD damages can be extremely costly – especially when it comes to latent defects that are not detected until the damaged component is installed in a customer’s system. Conventional ESD control programmes incorporate periodic verification checks of ESD control products to detect any issues that could result in ESD events and ESD damage. The problem is that ESD control products (and the EPA as a whole) are not constantly monitored.
Take an ioniser for example: if a company uses ionisation to handle process-essential insulators, the ionisers need to be fully reliable at all times. If an ioniser passes one check but is found to be out of balance at the next, the company faces a huge problem: nobody knows WHEN exactly the ioniser failed or if contributed to a charged insulator potentially causing ESD damage.
The Industry 4.0 IoT platform will be a game changer when it comes to creating a reliable and dependable ESD control programme. Sensors collecting vital ESD information like field voltage, Electromagnetic Interference (EMI), temperature, humidity etc. in an EPA will help detect potential threats in real-time allowing supervisors to take action even before an ESD threat occurs. Here is a (by no means exhaustive) list of advantages, IoT can bring to ESD Control:

Collecting Data
The day in an EPA can be busy. Taking the time to capture and record measurements of ionisers, wrist straps, work surfaces, automated processes etc. can be disruptive and is prone to errors. IoT allows data to be collected automatically without any input from users. This helps to increase the accuracy of data and allows operators and supervisors more time focusing on their actual jobs.

SmartLogwithUnitSmartLog Pro®: the SMART Access Control System – more information

Analysing Data
Supervisors have all the essential data in one place right in front of them and are able to make informed decisions; they can provide feedback and give suggestions in case of an ESD emergency. IoT allows to pinpoint areas of concern and prevent ESD events.

24/7 Monitoring
IoT continuously monitors processes and provides a real-time picture of them – no manual checks required. If a potential threat is detected, warnings will show-up immediately. There is no need to worry about potentially damaging sensitive devices because the next scheduled check of ionisers, wrist straps etc. has not been completed yet.

Cutting Costs
The number one reason for adapting an ESD control programme is to reduce costs by:

  • Enhancing quality and productivity,
  • Increasing reliability,
  • Improving customer satisfaction,
  • Lowering repair, rework and field service costs and
  • Reducing material, labour and overhead costs.

IoT pushes all of the above even further

  • Reduced workload for operators: Data is collected remotely without any input from users. Operators are not disrupted in their day-to-day activities.
  • Reduced workload for supervisors: Supervisors don’t have to collect and analyse data from personnel testers, field meters, monitors etc. The system does it for them and will highlight any issues.
  • Further increases in productivity and cost reductions: An ESD Programme can be managed better and with fewer resources.

SMT-Line-LayoutStatic Management Program (SMP): the next generation of ESD Process Control – more information

4. Conclusion
IoT will no doubt change ESD control and the way EPAs are monitored. Quantifiable data allows companies to see trends, become more proactive and improve the efficiency of their ESD process control system. IoT will support organisations’ efforts to make more dependable products, improve yields, increase automation and provide a measurable return on investment. Not only will this benefit users and supervisors, but the company as a whole.

 

 

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Resources:
Bill McCabe: Quick History of the Internet of Things..
Margaret Rouce: industrial internet of things (IIoT)
Michelle Lam: ESD Control in the World of IoT
Ian Wright: What Is Industry 4.0, Anyway?
Pascal Kriesche: Humans vs. machines – who will manage the factory of the future?
Industry 4.0: the fourth industrial revolution – guide to Industrie 4.0

Controlling ESD/EOS during the Soldering Process

When the tip of a soldering iron comes into direct electrical contact with the pins of a sensitive component, there is a danger of voltage and/or current signal transfer between:

  • the grounded iron tip and the grounded PC board,
  • the ungrounded iron tip and the grounded PC board,
  • the grounded iron tip and the ungrounded PC board.

This can cause Electrical Overstress (EOS) and Electrostatic Discharge (ESD).

What is EOS and why is it important to detect?
EOS is the exposure of a component or PCB board to a current and/or voltage outside its operational range. This absolute maximum rating (AMR) differs from one device to the next and needs to be provided by the manufacturer of each component used during the soldering process. EOS can cause damage, malfunction or accelerated aging in sensitive devices.

ESD can be generated if a component and a board have different potentials and the voltage transfers from one to the other. When such an event happens, the component goes through EOS. ESD can influence EOS, but EOS can also be influenced by other signals.
Many people are familiar with Electrostatic Discharge (ESD) which is caused by the spontaneous discharge between two materials that are at different levels of ElectroStatic potential. Once electrostatic potential between the two materials is balanced, the ESD event will stop.
An EOS event on the other hand is created by voltage and/or current spikes when operating equipment; it can therefore last “as long as the originating signal exists”. [Source] The potentially never-ending stimulus of EOS is what makes it such a big concern in the electronics industry. Even though the voltage levels are generally much lower compared to an ESD event, applying this smaller voltage combined with a larger peak current over a long period of time will cause significant damage.
The high temperatures during an EOS event (created by the high current) can lead to visible EOS damage.

For more information on EOS and the differences to ESD, check-out this post.

Sources of EOS during the Soldering Process
When soldering components, it’s the tip of the soldering iron that comes into contact with the potentially sensitive device. Therefore, many people assume the soldering tip is the cause of ESD/EOS. However, the soldering iron and its tip are just some of the components used at a workbench. Other components on the bench like tweezers, wiring, test equipment, etc. can also be sources of ESD/EOS as they come into contact with the component or board:

  • Loss of Ground
    The tip of an ungrounded soldering iron can accumulate a voltage of up to ½ of the iron’s supply voltage. It can be caused within the soldering iron itself or in power outlets.
  • Noise on Ground
    If a noise signal exists on ground, the tip of the solder iron will carry noise, too. These high-frequency signals, or electromagnetic interference (EMI), are disturbances that affect an electrical circuit, due to either electromagnetic induction or electromagnetic radiation emitted from an external source.
  • Noise on Power Lines
    Noise not only generates via ground but in power lines, too. Transformers and power supplies that convert voltages to 24V are the main culprit. They regularly carry high-frequency spikes which end up on the tip of the soldering iron.
  • Power Tools
    Although not technically related to the soldering process itself, it’s worth mentioning that the tips of power tools (e.g. electric screwdrivers) may not be properly grounded during rotation. This can result in high voltage on the tip itself.
  • Missing/Inadequate ESD Protection
    ESD can be a cause of EOS damage. Therefore, it is essential to have proper ESD Protection in place. A voltage on the operator or the PCB board can otherwise lead to an ESD Event and expose the components on the PCB to EOS.

Detecting EOS during the Soldering Process
1. Diagnostic Tools

  • SCS CTM051 Ground Pro Meter
    The SCS CTM051 Ground Pro Meter is a comprehensive instrument that measures ground impedance, AC and DC voltage on the ground as well as the presence of high-frequency noise or electromagnetic interference (EMI) voltage on the ground. It will alert if the soldering iron tip has lost its ground or has EMI voltage induced into the tip from an internal source on the soldering iron or from an EMI noisy ground or power lines.
    SCS CTM051 Ground Pro Meter
  • SCS CTM048 EM Eye – ESD Event Meter
    The SCS CTM048 EM Eye – ESD Event Meter paired with the SCS CTC028 EM Field Sensor is a diagnostic tool for the detection and analysis of ESD events and electromagnetic fields and can identify sources of harmful ESD Events and electromagnetic interference (EMI).
    SCS CTM048 EM Eye – ESD Event Meter

2. EOS Continuous Monitors

  • SCS CTC331-WW Iron Man® Plus Workstation Monitor
    The SCS CTC331-WW Iron Man® Plus Workstation Monitor is a single workstation continuous monitor which continuously monitors the path-to-ground integrity of an operator and conductive/dissipative worksurface and meets ANSI/ESD S20.20.
    The Iron Man® Plus Workstation Monitor is an essential tool when it comes to EOS detection. The unit is capable of detecting EOS on boards and alarms if an overvoltage (±5V or less) from a tool such as a soldering iron or electric screwdriver is applied to a circuit board under assembly.SCS CTC331-WW Iron Man® Plus Workstation Monitor

3. Data Acquisition

  • SCS Static Management Program
    SCS Static Management Program (SMP) continuously monitors the ESD parameters throughout all stages of manufacturing. It captures data from SCS workstation monitors, ground integrity monitors for equipment, ESD event and static voltage continuous monitors and provides real-time data of manufacturing processes. The SCS 770063 EM Aware Monitor, which is part of SMP, can help during the soldering process by monitoring ESD events and change of static voltage that may result in EOS. The EM Aware alarms (visual and audibly) locally and sends data to the database of the SMP system if any of the ESD parameters are detected to be higher than user-defined limits.
    SCS Static Management Program

Eliminating EOS during the Soldering Process
Once the source of EOS is known, there are many things that can be done to prevent it in the first place:

1. Managing Voltage on a PCB board
The only way to handle voltage on a PCB board is through ionisation. An ioniser creates great numbers of positively and negatively charged ions. Fans help the ions flow over the work area. Ionisation can neutralise static charges (or voltage) on a PCB board in a matter of seconds.
For more information on ionisation and how to choose the right type of ioniser for your application, please read these posts.

2. Managing Voltage on an Operator
Static voltage on an operator can be eliminated through proper grounding using a workstation monitor, e.g. WS Aware or Iron Man Plus Monitor. Sitting personnel is required to wear wrist straps. A wrist strap consists of a conductive wristband which provides an electrical connection to skin of an operator, and a coil cord, which is connected to a known ground point at a workbench, a tool or a continuous monitor. While a wrist strap does not prevent generation of voltages, its purpose is to dissipate these voltages to ground as quickly as possible.
Sitting personnel can also use continuous monitors – not only is the operator grounded through the continuous monitor, but they also provides a number of additional advantages:

  • Immediate feedback should a wrist strap fail
  • Monitoring of operators and work stations
  • Detection of split-second failures
  • Elimination of periodic testing

This post provides more details on continuous monitors.
Moving or standing personnel are grounded via a flooring/footwear system. ESD Footwear (e.g. foot grounders) are designed to reliably contact grounded ESD flooring and provide a continuous path-to-ground by removing electrostatic voltages from personnel.

3. Managing Current
One solution is the “re-routing of ground connection and separation of “noisy” ground from a clean one” as “connecting soldering iron and the workbench to the “quiet” ground often result in lower level of transient signals.“. [Source]
This will greatly reduce the high-frequency noise that could cause EOS damage.
If the noise on power lines and ground cannot be reduced manually, then the use of noise filters becomes necessary to reduce the risk of EOS exposure during the soldering process. Utilising these filters suppresses the noise on power lines and will allow the solder iron to use “clean” power only.
In his papers, Vladimir Kraz, explains the set-up of a soldering station using a noise filter in more detail.

Managing CurrentSoldering Iron with Power Line EMI Filter [Source]

Conclusion
During the soldering process, current and voltage spikes between the solder tip and PCB can cause ESD/EOS. Sources are varied:

  • Loss of Ground
  • Noise on Ground
  • Noise on Power Lines
  • Power Tools
  • Missing/Inadequate ESD Protection

Desco Europe offer a number of tools that can detect current, voltage and EMI – all potentially leading to ESD and EOS. Once the source of ESD/EOS is known, the next step is eliminating the source:

  • Managing Voltage on a PCB board using ionisers.
  • Managing Voltage on an operator using workstation monitors or foot grounders.
  • Managing Current using noise filters.
  • Managing voltage on materials at the work bench.
  • Managing ESD generation during specific processes.
  • Managing grounding.

 

 

References:

How to neutralise a charge on an object that cannot be grounded

We have learnt in a previous post that within an ESD Protected Area (EPA) all surfaces, objects, people and ESD Sensitive Devices (ESDs) are kept at the same electrical potential. We achieve this by using only ‘groundable’ materials. But what do you do if you absolutely need an item in your EPA and it cannot be grounded? Don’t sweat, not all hope is lost! There are a couple of options which will allow you to use the item in question. Let us explain…

Conductors and Insulators
In ESD Control, we differentiate conductors and insulators.
Materials that easily transfer electrons are called conductors. Some examples of conductors are metals, carbon and the human body’s sweat layer.

ConductorA charged conductor can transfer electrons which allows it to be grounded

Materials that do not easily transfer electrons are called insulators and are by definition non-conductors. Some well-known insulators are common plastics and glass.

InsulatorInsulators will hold the charge and cannot be grounded and “conduct” the charge away

Both, conductors and insulators, may become charged with static electricity and discharge.
Electrostatic charges can effectively be removed from conductors by grounding them. However, the item grounded must be conductive or dissipative. An insulator on the other hand, will hold the charge and cannot be grounded and “conduct” the charge away.

Conductors and Insulators in an EPA
The first two fundamental principles of ESD Control are:

  1. Ground all conductors including people.
  2. Remove all insulators.

To achieve #1, all surfaces, products and people are bonded to Ground. Bonding means linking, usually through a resistance of between 1 and 10 megohms. Wrist straps and work surface mats are some of the most common devices used to remove static charges. Wrist straps drain charges from operators and a properly grounded mat will provide path-to-ground for exposed ESD susceptible devices. Movable items (such as containers and tools) are bonded by virtue of standing on a bonded surface or being held by a bonded person.

However, what if the static charge in question is on something that cannot be grounded, i.e. an insulator? Then #2 of our ESD Control principles will kick in. Per the ESD Standard, “All non-essential insulators and items (plastics and paper), such as coffee cups, food wrappers and personal items shall be removed from the workstation or any operation where unprotected ESDS are handled.
The ESD threat associated with process essential insulators or electrostatic field sources shall be evaluated to ensure that:

  • the electrostatic field at the position where the ESDS are handled shall not exceed 5 000 V/m;

or

  • if the electrostatic potential measured at the surface of the process required insulator exceeds 2 000 V, the item shall be kept a minimum of 30 cm from the ESDS; and
  • if the electrostatic potential measured at the surface of the process required insulator exceeds 125 V, the item shall be kept a minimum of 2,5 cm from the ESDS.”

[IEC 61340-5-1:2016 clause 5.3.4.2 Insulators]

Always keep insulators a minimum of 31cm from ESDS itemsAlways keep insulators a minimum of 31cm from ESDS items

“Process-essential” Insulators
Well, we all know that nothing in life is black and white. It would be easy to just follow the above ‘rules’ and Bob’s your uncle – but unfortunately that’s not always possible. There are situations where said insulator is an item used at the workstation such as a hand tools. They are essential – you cannot just throw them out of the EPA. If you do, the job won’t get done.
So, the question is – how do you ‘remove’ these vital insulators without actually ‘removing’ them from your EPA? There are 2 options you should try first:

1. Replace regular insulative items with an ESD protective version
There are numerous tools and accessories available that are ESD safe – from document handling to cups & dispensers and brushes and waste bins. They are either conductive or dissipative and replace the standard insulative varieties that are generally used at a workbench. For more information on using ESD safe tools and accessories, check this post.

2. Periodically apply a coat of Topical Antistat
The Reztore® Topical Antistat (or similar solution) is for use on non-ESD surfaces. After it has been applied and the surface dries, an antistatic and protective static dissipative coating is left behind. The static dissipative coating will allow charges to drain off when grounded. The antistatic properties will reduce triboelectric voltage to under 200 volts. It therefore gives non-ESD surfaces electrical properties until the hard coat is worn away.

If these two options are not feasible for your application, the insulator is termed “process-essential” and therefore neutralisation using an ioniser should become a necessary part of your ESD control programme.

Neutralisation
Most ESD workstations will have some insulators or isolated conductors that cannot be removed or replaced. These should be addressed with ionisation.
Examples of some common process essential insulators are a PC board substrate, insulative test fixtures and product plastic housings.

Electronic enclosures are process-essential insulators
Electronic enclosures are process-essential insulators

An example of isolated conductors can be conductive traces or components loaded on a PC board that is not in contact with the ESD worksurface.

An ioniser creates great numbers of positively and negatively charged ions. Fans help the ions flow over the work area. Ionisation can neutralise static charges on an insulator in a matter of seconds, thereby reducing their potential to cause ESD damage.
The charged ions created by an ioniser will:

  • neutralise charges on process required insulators,
  • neutralise charges on non- essential insulators,
  • neutralise isolated conductors and
  • minimise triboelectric charging.

Ioniser ExampleInsulators and isolated conductors are common in ESD Sensitive (ESDS) Devices – Ionisers can help

For more information on ionisers and how to choose the right type of ioniser for your application, read this post.

Summary
Insulators, by definition, are non-conductors and therefore cannot be grounded. Insulators can be controlled by doing the following within an EPA:

  • Keep insulators a minimum of 31cm from ESDS items at all times or
  • Replace regular insulative items with an ESD protective version or
  • Periodically apply a coat of Topical Antistat

When none of the above is possible, the insulator is termed “process-essential” and therefore neutralisation using an ioniser should become a necessary part of your ESD control programme.

6 Tips for handling “Class 0” Items

When talking about ESD Classifications a little while ago, we identified a “class 0” item as withstanding discharges of less than 250 volts.
The introduction of IEC 64340-5-1 states “This part of IEC 61340 covers the requirements necessary to design, establish, implement and maintain an electrostatic discharge (ESD) control program for activities that: manufacture, process, assemble, install, package, label, service, test, inspect, transport or otherwise handle electrical or electronic parts, assemblies and equipment susceptible to damage by electrostatic discharges greater than or equal to 100 V human body model (HBM), 200 V charged device model (CDM) and 35 V on isolated conductors.

So, the obvious question is: how do you handle items that are susceptible to voltages of less than 100V? That’s what we’re going to answer in today’s blog post.

Introduction
Years ago, it was common for devices to be vulnerable to voltages greater than 100V. As the need for smaller and faster devices increased, so did their sensitivity to ElectroStatic Discharges as circuit-protection schemes were removed to stay ahead of the market. These new extremely sensitive components are now susceptible to discharges nearing 0V. Obviously, this causes problems for companies handling these devices: while their ESD programme may be in compliance with the ESD Standard, extremely sensitive devices require tighter ESD Control to protect them from ESD failures.

Definition of “Class 0”
Before moving any further, we need to qualify the term “class 0” as there is a lot of confusion out there as to what this term actually means. As stated above, the HBM Model refers to any item with a failure voltage of less than 250V as a “class 0” component. However, in recent times, the term has been used more and more to describe ultra-sensitive devices with failure voltages of less than 100V. Whilst the following tips and tricks really work on any “class 0” item, they are specifically designed to protect extremely sensitive items that withstand discharges of less than 100V.

People are often a major factor in the generation of static chargesUltra-sensitive devices are extremely common these days

Do your homework
Imagine someone (a customer, your boss etc.) is approaching you and demands you to update all internal procedures so your company can handle “class 0” components. Do you know how to handle this request? Or would you be pulling out your hair trying to figure out what needs to be done? As explained further above, “class 0” refers to a wide range of items and there are a few things you should remember before making any changes to your existing ESD programme:

  1. Verify what ESD Model your company/engineers/customers etc. are referring to. As we have learnt in the past, there are different ESD models (HBM, CDM, MM) as well as individual classifications for each model. A lot of people get confused when it comes to citing ESD classifications. In reality, there is only one “class 0” which refers to the human body model (HBM) but it’s always best to check.
  2. Check the specific withstand voltage an individual part is susceptible to. “Class 0” refers to all items that withstand discharges of less than 250V. However, there is a big difference between a failure voltage of 240V or 50V. You need to have detailed ESD sensitivity information available before being able to make decisions on how to improve your existing ESD control programme. This step is actually part of creating a compliance verification plan.
  3. A part’s ESD classification is only of importance until it is ‘merged’ into an assembly. So, the ESD classification of a device only refers to the stand-alone component. Once it goes into another construction, the classification of the whole assembly is likely to change.

Below are 6 tips that will help your company to upgrade your ESD control programme so you can effectively and efficiently handle ultra-sensitive items without risking ESD damage.

One thing to note: proactive actions are critical. There is no point in figuring out how to protect your components from ESD damage AFTER you have received them. Trust us: it’s gonna go wrong! Instead, focus on getting things sorted BEFOREHAND. That’s the best approach to stay ahead of the game.

1. Improve Grounding
So, you will already know that inside an EPA, all conductors (including people) are grounded. Now you’re probably thinking: “But I’ve already grounded my operators and worksurfaces. What else is there left to do?”. Firstly, well done for properly grounding the ‘objects’ in your EPA – trust us, that’s not a given! The next step is to tweak things a bit to allow for even better protection. Here are some suggestions:

Personnel:

  • Decrease the wrist strap and ESD footwear upper limit. The ESD Association has test data showing charge on a person is less as the path-to-ground resistance is less.
  • Use continuous monitors and ESD smocks
  • Introduce/increase use of ESD flooring
  • Use sole or full coverage foot grounders (rather than heel grounders)

WorkstationFull coverage foot grounders are recommended when handling ultra-sensitive devices

Worksurfaces:

  • Reduce the required limit for Point-to-Point resistance of 1 x 109 per the ESD Standard to 106 to 108 ohms (see #5). The reason for this reduction is simple: 1 x 109 is too high as it still produces thousands of volts of in electrostatic charges. However, the resistance cannot be too small either as this can lead to a sudden ‘hard discharge’ potentially damaging ESD sensitive components.

Other:

  • Improve grounding of carts, shelves and equipment to Ground
  • Minimise isolated conductors like devices on PCBs

2. Minimise Charge Generation
The best form of control is to minimise charge generation. First of all, you should always use shielding packing products like bags or containers (especially when outside an EPA) as these protect from generating charges in the first place. For more information on choosing the correct type of ESD Packaging, we recommend reading this post.

The next step is to eliminate charges once they are generated – this can be achieved through grounding and ionisation. We’ll cover ionisation in #3 and #4. We’ve already talked about improved grounding in #1. However, for ultra-sensitive components, we also recommend the following:

Both types of ESD products create a low tribocharging coating which allows charges to drain off when grounded. The antistatic properties will reduce triboelectric voltage to under 200 volts.
For more tips on managing charge generation from flooring, check this post.

3. Remove Insulators
When talking about conductors and insulators, we explained that insulators cannot be grounded and can damage nearby sensitive devices with a sudden uncontrolled discharge. It is therefore critical to eliminate ALL insulators that are not required in your EPA: plastic cups, non-ESD brushes, tapes etc. How? Here are a couple of options:

EBP-Bar-for-FlyerUse ESD safe accessories whenever possible

If an insulator is absolutely necessary for production and cannot be removed from the EPA, you could consider a topical treatment which will reduce triboelectric charges.
Is this not an option, then move on to tip #4.

4. Use Ionisation
First of all, ionisation is not a cure-all. We’ve learnt that ionisers neutralise charges on an insulator.
However, that does not mean that you can just have any insulator in your EPA because the ioniser will “just fix it”. No, in this instance, prevention is generally a better option than the cure. So, your priority should ALWAYS be to remove non-process essential insulators from your EPA – see tip #3. If this is not possible – then ionisation becomes essential:

  • Ionisers can be critical to reduce induction charging caused by process necessary insulators
  • Ionisers can be critical in eliminating charges on isolated conductors like devices on PCBs
  • Offset voltage (balance) and discharge times are critical considerations depending on the actual application
  • Ionisation can reduce ElectroStatic Attraction (ESA) and charged particles clinging and contaminating products.

It is recommended to use ionisers with feedback mechanisms so you’re notified if the offset voltage is out of balance.

5. Increase ESD Training and Awareness
ESD Training is a requirement of every ESD Programme. When handling ultra-sensitive devices, it is even more important to remind everyone what pre-cautions are necessary to avoid damage. Regular ‘refreshers’ are a must and it is recommended to verify the effectiveness of the training programme, e.g. through tests. So, who, when and what should be taught? Easy!

Training is an essential part of an ESD Control ProgrammeESD Training is a vital part of every successful ESD Control Programme

  • ESD training needs to be provided to everyone who handles ESD sensitive devices – that includes managers, supervisors, subcontractors, visitors, cleaners and even temporary personnel.
  • Training must be given at the beginning of employment (BEFORE getting anywhere near a sensitive products) and in regular intervals thereafter.
  • Training should be conducted on proper compliance verification procedures and on the proper use of equipment used for verification.

6. Create an enhanced Compliance Verification Plan
We talked in a previous post about compliance verification, what it is and how to create a plan that complies with the ESD standard. So, if you already followed our steps and have a plan in place, you’re probably wondering how you can possibly improve on that? Here are a few tips:

  • Use a computer data collection system for wrist straps and foot grounders testing, e.g. SmartLog Pro™
  • Increase the testing frequency of personnel grounding devices from once per day to every time the operator enters the EPA
  • Use continuous monitors where operators are grounded via wrist straps. Consider computer based monitor data collection system, e.g. SMP. This should include continuous monitoring of the mat Ground.
  • Use Ground continuous monitors, e.g. SCS Ground Master. At a large facility, the most frequent reoccurring violation is the ESD mat ground cord either becoming disconnected from the mat or grounding point. As Ground continuous monitors will only test the fact that the mat is grounded, it is still imperative that the Resistance to Ground of the mat is regularly tested. Remember that the use of improper mat cleaners can raise the mat surface resistance above the upper recommended level of <109
  • Test ionisers more frequently or consider self-monitoring ionisers. Computer based data collection systems are a good alternative, too.
  • Increase the use of a static field meter and nano coulomb testing to verify that automated processes (like auto insertion, tape and reel, etc) are not generating charges above acceptable limits.

Conclusion
The bottom line is: the only way to protect ultra-sensitive components is to increase ESD protective redundancies and periodic verifications to all ESD Control technical elements.
If you handle ultra-sensitive items, to decrease the probability of ESD damage, additional precautions are required including additional and/or more stringent technical requirements for EPA ESD control products, increasing redundancies, and more frequent periodic verifications or audits. Additionally, ESD control process systems should be evaluated as to their performance as a system. You will need to understand how the technical elements in use perform relative to the sensitivity of the devices being handled. Thus, tailoring the process to handle the more sensitive
parts. For example: If the footwear/flooring allows a person’s body voltage to reach say 80 volts and a 50 withstand voltage item gets introduced into the process, you will either have to allow only handling via wrist straps or would have to find a way to modify the footwear/flooring performance to get peak voltages below the 50 volt threshold.

Remember: it is YOUR responsibility to do protect YOUR devices and YOUR reputation. The ESD Standard can only give recommendations and it’ll always be behind current/future developments. As soon as a Standard is published, technology will have progressed. So, if – in order to protect your devices – your company needs to implement methods/procedures that exceed the recommendations of the ESD Standard, so be it.

References:

5 common mistakes in ESD Control & how to avoid them

Many companies implement an ESD Control Programme with the aim of improving their operations. Effective ESD control can be a key to improving:

  • Productivity,
  • Quality and
  • Customer satisfaction.

However, problems arise when an organisation invests in ESD protective products and/or equipment and then misuses them. Not only do these companies waste a lot of money but they could also be causing more harm than good. So, with today’s blog post we want to highlight some of the major issues we have come across and how you can avoid or fix them.

Introduction

Remember that for a successful ESD Control Programme, ESD protection is required throughout the manufacturing process: from goods-in to assembly all the way through to inspection. Anybody who handles electrical or electronic parts, assemblies or equipment that are susceptible to damage by electrostatic discharges should take necessary precautions.

Think of viruses or bacteria that can infect the human body. Just like ESD, they are invisible. Yet, in hospitals the defence against this hidden threat is controlled by extensive contamination control procedures including sterilisation. The same applies to ESD Control: you should never handle, assemble or repair electronic assemblies without taking adequate protective measures against ESD.

Treat ESD like Viruses & Bacteria
Treat ESD like you would Viruses and Bacteria

For an ESD Control Programme to be successful, there is discipline required; basic ESD Control principles should be followed:

  • Ground conductors.
  • Remove, convert or neutralise insulators with ionisers.
  • Shield ESD sensitive items when stored or transported outside the EPA.

For more information on how to get your ESD Control Programme off the ground (no pun intended) and create an EPA, check this post.

Common Mistakes in ESD Control

1. Poorly maintained or out-of-balance Ionisers

If an ioniser is out of balance, instead of neutralising charges, it will produce primarily positive or negative ions. This results in placing an electrostatic charge on items that are not grounded. These could then discharge to nearby sensitive items potentially cause ESD damage.

 Check Remember to clean emitter pins and filters using appropriate tools. Create a regular maintenance schedule which will extend the lifespan of your ionisers tremendously.
Consider using ionisers with “Clean Me” and//or “Balance” alarms. These will alert you when cleaning is required.
 Standard All ionization devices will require periodic maintenance for proper operation. Maintenance intervals for ionizers vary widely depending on the type of ionization equipment and use environment. Critical clean room use will generally require more frequent attention. It is important to set up a routine schedule for ionizer service.”
[CLC TR 61340-5-2 User guide Ionization clause 4.7.6.7 Maintenance and cleaning]

This post covers in detail how ionisers work and what type of ioniser will work best for your application.

2. Ungrounded ESD Garments

We’ve seen it so many times: operators wearing an ESD coat (without appropriate wrist straps and/or footwear/flooring) thinking they are properly grounded. Well, here is some news for you: you are not!

 Check Every ESD garment needs to be electrically bonded to the grounding system of the wearer. Otherwise it just acts as a floating conductor. There are a few options to choose from:
·         Wrist Straps
·         ESD footwear/flooring
·         Hip-to-Cuff grounding
 Standard The ESD risk provided by everyday clothing cannot be easily assessed. The current general view of experts is that the main source of ESD risk may occur where ESDS [ESD sensitive items] can reach high induced voltage due to external fields from the clothing, and subsequently experience a field induced CDM [Charged Device Model] type discharge. So ESD control garments may be of particular benefit where larger ESDS having low CDM withstand voltage are handled, and operators habitually wear everyday clothing that could generate electrostatic high fields.
[CLC TR 61340-5-2 User guide Garments clause 4.7.7.1 Introductory remarks]

Another thing to remember with ESD clothing is that they do lose their ESD properties over time. So make sure you incorporate periodic checks (see #3 below).

If you need more information on ESD coats, we recommend having a look at this post.

3. Not Checking ESD Control Products

A lot of companies waste thousands of pounds by buying and installing ESD Control products but then never check them resulting in ESD equipment that is out of specification. They haven’t got the tools in place to check their ESD items and have no idea if they are actually working correctly. Remember, ESD products (just like any other) are subject to wear and tear, workstations get moved, ground cords get disconnected…. The list goes on.

 Check When investing in ESD Control Products, make sure you also establish a Compliance Verification Plan. This ensures that:
·         ESD equipment is checked periodically and
·         Necessary test equipment is available.
 Standard A compliance verification plan shall be established to ensure the organization’s fulfilment of the requirements of the plan. Process monitoring (measurements) shall be conducted in accordance with a compliance verification plan that identifies the technical requirements to be verified, the measurement limits and the frequency at which those verifications shall occur. The compliance verification plan shall document the test methods used for process monitoring and measurements. If the organization uses different test methods to replace those of this standard, the organization shall be able to show that the results achieved correlate with the referenced standards. Where test methods are devised for testing items not covered in this standard, these shall be adequately documented including corresponding test limits. Compliance verification records shall be established and maintained to provide evidence of conformity to the technical requirements.
The test equipment selected shall be capable of making the measurements defined in the compliance verification plan.

[EN 61340-5-1 clause 5.2.4 Compliance verification plan]

For detailed instructions on how to create a Compliance Verification Plan, have a read through this post.

4. Re-Using Shielding Bags with Holes or Scratches

ESD Shielding Bags are used to store and transport ESD sensitive items. When used properly, they create a Faraday Cage effect which causes charges to be conducted around the outside surface. Since similar charges repel, charges will rest on the exterior and ESD sensitive items on the inside will be ‘safe’. However, if the shielding layer of an ESD Shielding Bag is damaged, ESD sensitive items on the inside will not be protected anymore.

 Check Re-using shielding bags is acceptable as long as there is no damage to the shielding layer. Shielding bags with holes, tears or excessive wrinkles should be discarded.
Use a system of labels to identify when the bag has gone through five (5) handling cycles. When there are five broken labels, the bag is discarded.
 Standard ESD shielding packaging is to be used particularly when transporting or storing ESD sensitive items outside an ESD Protected Area. Per Packaging Standard EN 61340-5-3 clause 5.3 Outside an EPA “Transportation of sensitive products outside of an EPA shall require packaging that provides both:
– dissipative or conductive materials for intimate contact;
– a structure that provides electrostatic discharge shielding.

This post provides further “dos and don’ts” when using ESD Shielding Bags.

5. Using Household Cleaners on ESD Matting

A lot of people use standard household cleaners on their ESD matting not realising how damaging this is to their ESD Programme. Many household cleaners contain silicone which creates that lovely shine you get when wiping surfaces in your home. The problem is that on an ESD working surface mat, that same silicone creates an insulative layer which reduces the grounding performance of the mat.

 Check Don’t spend all this extra money on ESD matting and then coat it with an insulative layer by using household cleaners. There are many specially formulated ESD surface and mat cleaners available on the market. Only clean your ESD working surfaces using those cleaners.
 Standard “Periodic cleaning, following the manufacturer’s recommendations, is required to maintain proper electrical function of all work surfaces. Ensure that the cleaning products used to not leave an electrically insulative residue which is common with some household cleaners that contain silicone.”
[CLC TR 61340-5-2 User guide Work surfaces clause 4.7.1.5 Maintenance]

This post covers everything you need to know about ESD protective working surfaces.

Now – the above list is by no means complete. There are many more issues we see when setting foot into EPAs but we think it’s true to say that these issues are some of the ones we encounter more often.

What issues have you come across before? Leave us a comment below.

Effective ESD Control in a Service or Repair Centre

The best-equipped service bench in your shop can be a real money-maker when set-up properly. It can also be a source of frustration and lost revenue if the threat of ElectroStatic Discharge (ESD) is ignored. Static electricity is nothing new; it’s all around us and always has been. What has changed is the proliferation of semiconductors in almost every consumer product we buy. Couple that with the fact that as device complexity becomes greater, often its static sensitivity increases. Some semiconductor devices may be damaged by as little as 20-30 volts!
A typical scenario might be where an electronic product is brought in for service, properly diagnosed, repaired, only to find a new and perhaps different symptom, necessitating additional repair. Damage from static electricity cannot be ruled out unless the technician understands the ESD problem and has developed methods to keep it in check.

It is important to note that we are addressing the issue of ESD in terms of control, and not elimination. The potential for an ESD event to occur cannot be totally eliminated outside of a laboratory environment, but we can greatly reduce the risk with proper training and equipment. By implementing a good static control program and developing some simple habits, the problem can be effectively controlled.

The Source of the Problem

As mentioned earlier, static is all around us. We occasionally will see or feel it by walking on carpet, touching something or someone and feeling the “zap” of a static discharge. The perception level varies but the static charge is typically 2000-3000 volts before we can feel it. Remembering that the sensitivity of some parts is under 100 volts, it’s easy to see that we might never know that an ESD event has occurred.
Even though carpet may not be used around the service bench, there are many other – subtler – static “generators” frequently found around or on a service bench. The innocent-looking Styrofoam coffee cup can be a tremendous source of static. The simple act of pulling several inches of adhesive tape from a roll can generate several thousand volts of static! Many insulative materials will develop a charge by rubbing them or separating them from another material. This phenomenon is known as “tribocharging” and it occurs often where there are insulative materials present.

Charge Generation Unwinding a Roll of Tape

Sources of Charge Generation: Unwinding a Roll of Tape

People are often a major factor in the generation of static charges. Studies have shown that personnel in a manufacturing environment frequently develop 5000 volts or more just by walking across the floor. Again, this is “tribocharging” produced by the separation of their shoes and the flooring as they walk.
A technician seated at a non-ESD workbench could easily have a 400-500 volt charge on his or her body caused not only by friction or tribocharging but additionally by the constant change in body capacitance that occurs from natural movements. The simple act of lifting both feet off the floor can raise the measured voltage on a person as much as 500-1000 volts.

Setting up a “static safe” Programme

Perhaps the most important factor in a successful static control programme is developing an awareness of the “unseen” problem. One of the best ways to demonstrate the hazard is by using a “static field meter”. Although this is not something a service centre would typically purchase, it often can be borrowed from a local static control product distributor. The visual impact of locating and measuring static charges in excess of 1000 volts will surely get the attention of the sceptics.

Static Field MeterStatic Field Meter – find more information here

Education of Personnel

This is an essential basic ingredient in any effective static control programme. A high level of static awareness must be created and maintained in and around the protected area. Once personnel understand the potential problem, it might help to reinforce this understanding by hanging up a few static control posters in strategic locations. The technician doesn’t need an unprotected person wandering over and touching things on the service bench.
Information on static control and setting up a static-safe workstation is readily available from a variety of sources. Your local electronic parts distributor will often have a variety of ESD Control products and may also have literature from manufacturers on setting up a static-safe area.

Workstation Grounding

To minimise the threat of an ESD event, we need to bring all components of the system to the same relative potential and keep them that way.

  • Establish an ESD Common Grounding Point, an electrical junction where all ESD grounds are connected to. Usually, a common ground point is connected to ground, preferably equipment ground. If you need help with grounding your workstation, this post might help to clarify a few things.
  • The Service Bench Surface should be covered with a dissipative material. This can be either an ESD-type high-pressure laminate formed as the benchtop surface, or it may be one of the many types of dissipative mats placed upon the benchtop surface. The mats are available in different colours, with different surface textures, and with various cushioning effects. Whichever type is chosen, look for a material with a surface resistivity of 1 x 109 or less, as these materials are sufficiently conductive to discharge objects in less than one second. The ESD laminate or mat must be grounded to the ESD common grounding point to work properly. Frequently, a one Megohm current limiting safety resistor is used in series with the work surface ground. This blog post will provide more information on how to choose and install your ESD working surface.
    Working-Surface-Matting

    Types of Bench Matting – click here for more information
  • A Dissipative Floor Mat may also be used, especially if the technician intends to wear foot-grounding devices. The selection of the floor mat should take into consideration several factors. If anything is to roll on the mat, then a soft, cushion-type mat will probably not work well. If the tech does a lot of standing, then the soft, anti-fatigue type will be much appreciated. Again, the mat should be grounded to the common ground point, with or without the safety resistor as desired. If you require more information as to how you can manage charge generation from flooring, have a look at this previous post.
  • Workstation Tools and Supplies should be selected with ESD in mind. Avoid insulators and plastics where possible on and around the bench. Poly bags and normal adhesive tapes can generate substantial charges, as can plastic cups and glasses. If charge-generating plastics and the like cannot be eliminated, consider using one of the small, low-cost air ionisers available from some manufacturers. It can usually be mounted on the bench to conserve work area, and then aimed at the area where most of the work is being done. The ioniser does not eliminate the need for grounding the working surface or the operator, but it does drain static charges from insulators, which do not lend themselves to grounding. Not sure what tools and accessories to replace? Check out this blog post.

Personnel Grounding

As was mentioned previously, people are great static generators. Simple movements at the bench can easily build up charges as high as 500-1000 volts. Therefore, controlling this charge build-up on the technician is essential. The two best-known methods for draining the charge on a person are wrist straps with ground cords and foot or heel grounds.

  • Wrist Straps are probably the most common item used for personnel grounding. They are comprised of a conductive band or strap that fits snugly on the wrist. The wrist strap is frequently made of an elastic material with a conductive inner surface, or it may be a metallic expandable band similar to that found on a watch. Need more information on wrist straps? We’ve created a Q&A post to answer all questions you may have.
  • Ground Cords are typically made of a highly flexible wire and often are made retractable for additional freedom of movement. There are two safety features that are usually built into the cord, and the user should not attempt to bypass them. The first, and most important, is a current limiting resistor (typically 1 Megohm) which prevents hazardous current from flowing through the cord in the event the wearer inadvertently contacts line voltage. The line voltage may find another path to ground, but the cord is designed to neither increase or reduce shock hazard for voltages under 250 volts. The second safety feature built into most cords is a breakaway connection to allow the user to exit rapidly in an emergency. This is usually accomplished by using a snap connector at the wrist strap end.

    Wrist Band and Grounding Cord – more information

  • Foot/Heel Grounders or ESD Shoes are frequently used where the technician needs more freedom of movement than the wrist strap and cord allows. The heel grounder is often made of a conductive rubber or vinyl and is worn over a standard shoe. It usually has a strap that passes under the heel for good contact and a strap of some type that is laid inside the shoe for contact to the wearer. Heel grounders must be used with some type of conductive or dissipative floor surface to be effective and should be worn on both feet to ensure continuous contact with the floor. Obviously, lifting both feet from the floor while sitting will cause protection to be lost. If you can’t decide between foot/heel grounders or ESD shoes, this comparison may be of help.

Don’t forget to regularly check your personnel grounding items:

Personnel Grounding ChecklistThe Personnel Grounding Checklist

Summary

An effective static control programme doesn’t have to be expensive or complex. The main concept is to minimise the generation of static and to drain it away when it does occur, thereby lessening the chance for an ESD event to happen. The ingredients for an effective ESD program are:

      • Education: to einsure that everyone understands the problem and the proper handling of sensitive devices.
      • Workstation Grounding: through the use of a dissipative working surface material and dissipative flooring materials as required.
      • Personnel Grounding: using wrist straps with ground cords and/or foot-grounding devices.
      • Follow-up to ensure Compliance: all elements of the programme should be checked frequently to determine that they are working effectively.

The ESD “threat” is not likely to go away soon, and it is very likely to become an even greater hazard, as electronic devices continue to increase in complexity and decrease in size. By implementing a static control programme now, you will be prepared for the more sensitive products that will be coming.

How to create a Compliance Verification Plan

Each component in an ESD protected area (EPA) plays a vital part in the fight against electrostatic discharge (ESD). If just one component is not performing correctly, you could harm your ESD sensitive devices potentially costing your company a lot of money. The problem with many ESD protection products is that you can’t always see the damage – think wrist straps! By just looking at a coiled cord, you can’t confirm it’s working correctly; even without any visible damage to the insulation, the conductor on the inside could be broken. This is where periodic verification comes into play.

ESD protected area (EPA) products should be tested:

  1. Prior to installation to qualify product for listing in user’s ESD control plan.
  2. During the initial installation.
  3. For periodic checks of installed products as part of IEC 61340-5-1 Edition 2 2016 clause 5.2.3 Compliance verification plan.

LabCoatsTestingChecking an ESD Lab Coat using a Surface Resistance Tester

A compliance verification plan shall be established to ensure the organization’s fulfilment of the requirements of the plan. Process monitoring (measurements) shall be conducted in accordance with a compliance verification plan that identifies the technical requirements to be verified, the measurement limits and the frequency at which those verifications shall occur. The compliance verification plan shall document the test methods used for process monitoring and measurements. If the organization uses different test methods to replace those of this standard, the organization shall be able to show that the results achieved correlate with the referenced standards. Where test methods are devised for testing items not covered in this standard, these shall be adequately documented including corresponding test limits. Compliance verification records shall be established and maintained to provide evidence of conformity to the technical requirements.
The test equipment selected shall be capable of making the measurements defined in the compliance verification plan.
” [IEC 61340-5-1:2016 clause 5.2.4 Compliance verification plan]

Components of a Verification Plan

As outlined in the User Guide 61340-5-2:2008, each company’s verification plan needs to include:

1. A list of items that are used in the EPA and need to be checked on a regular basis

This would include ESD working surfaces, personnel grounding devices like wrist straps or foot grounders, ionisers etc. It is recommended to create a checklist comprising all ESD control products: this will ensure EPAs are checked consistently at every audit.

2. A schedule specifying what intervals and how each item is checked

The test frequency will depend on a number of things, e.g. how long the item will last, how often it is used or how important it is to the overall ESD control programme.
As an example: wrist straps are chosen by most companies to ground their operators; they are the first line of defence against ESD damage. They are in constant use and are subjected to relentless bending and stretching. Therefore, they are generally checked at the beginning of each shift to ensure they are still working correctly and ESD sensitive items are protected. Ionisers on the other hand are recommended to be checked every 6 months: whilst they are in constant use, they are designed to be; the only actual ‘interaction’ with the user is turning the unit on/off. If however, the ioniser is used in a critical clean room, the test frequency may need to be increased.

222566use
It is recommended that Wrist Straps are checked before each shift

The user guide offers a solution: “Some organizations may want to increase the time between verifications of an ESD control item after it has been in use for a period of time. This is typically done by monitoring the failures of the ESD control item. Once the organization has evidence that there is an acceptable period of time where no failures were found, the time between verifications can be increased. The new verification interval is then monitored. If an unacceptable level of failures is identified, then the verification frequency should revert back to the previous level.” [User Guide 61340-5-2:2008 clause 4.3.3 Verification frequency]
The industry typically uses 2 types of verification to achieve maximum success: visual and measurement verification. As the name suggests, visual verification is used to ensure ESD working surfaces and operators are grounded, ESD flooring is in good shape or wrist straps are checked before handling ESD sensitive items.

Actual measurements are taken by trained personnel using specially designed equipment to verify proper performance of an ESD control item.

3. The suitable limits for every item used to control ESD damage

IEC 61340-5-1:2016 contains recommendations of acceptable limits for every ESD control item. Following these references reduces the likelihood of 100V (HBM) sensitive devices being damaged by an ESD event.

Please bear in mind that there may be situations where the limits need to be adjusted to meet the company’s requirements.

4. The test methods used to ensure each ESD product meets the set limits

Tables 1 to 3 of IEC 61340-5-1:2016 list the different test methods a company has to follow. If a company uses other test methods or have developed their own test methods, the ESD control programme plan needs to include a statement explaining why referenced standards are not used. The company also needs to show their chosen test methods are suitable and reliable.

It is recommended that written procedures are created for the different test methods. It is the company’s responsibility to ensure anybody performing the tests understands the procedures and follows them accordingly.

5. The equipment used to take measurements specified in the test methods

Every company needs to acquire proper test equipment that complies with the individual test methods specified in Tables 1 to 3 of IEC 61340-5-1:2016. Personnel performing measurements need to be trained on how equipment is used.

222643UseChecking ESD Working Surface using a Surface Resistance Tester

6. A list of employees who will be performing the audits

Part of the verification plan is the choice of internal auditors. A few suggestions for the selection process:

  • Each induvial is required to know the ESD Standard IEC 61340-5-1 AND the company’s individual ESD programme.
  • It is essential that the selected team member recognises the role of the ESD control programme in the company’s overall quality management system.
  • It is recommended that each nominated worker has been trained on performing audits.
  • The designated employee should be familiar with the manufacturing process they are inspecting.

7. How to deal with non-compliance situations

Once an audit has been completed, it is important to keep everyone in the loop and report the findings to the management team. This is particularly vital if “out-of-compliance” issues were uncovered during the audit. It is the responsibility of the ESD coordinator to categorise how severe each non-conformance is; key problems should be dealt with first and management should be notified immediately of significant non-compliance matters.

Results of audits (especially non-compliance findings) are generally presented using charts. Each chart should classify:

  • The total findings of the audit
  • The type of each finding
  • The area that was audited

It is important to note that each company should set targets for a given area and include a trend report. This data can assist in determining if employees follow the outlined ESD control programme and if improvements can be seen over time.

Here is an example of a Verification Plan using ESD flooring for demonstration purposes. A few notes:

  • Our sample company has 2 different areas where ESD floor matting is used: the packaging area and the main EPA.
  • Flooring is not used for grounding personnel handling ESD sensitive items
  • Our sample company has established that the limits outlined in the standard are suitable for their internal requirements.

Bear in mind that ALL your ESD control items need to be included in your verification plan. So if your company uses wrist straps, smocks, chairs, gloves etc. then ALL of them have to be listed as part your ESD control programme.

The impact of relative humidity on ESD

A video making the rounds on Social Media this week highlights a very common problem in ESD Protection: dry air.
The report shows energy minister Simon Bridges walking around his office spraying the floor with water, applying tape to door handles and using an antistatic mat at his desk. The reason? Simple: a new carpet which was installed at the Beehive and the “little tickles” ministers are getting as a result.

SImon Bridges spraying the floor in his office with water
Simon Bridges spraying the floor in his office with water (Source)

Jim Robb who is in charge of maintaining the parliament building provides the following explanation: “We’re in the middle of winter, we’ve got cold polar air, there’s no moisture in it and it’s a very common problem, I’ve been dealing with this for thirty years.”

While the ministers at the Beehive seem to have figured out solutions to avoid the “zap”, we want to show you how you can solve the issue of dry air in your EPA.

Impact of relative humidity on ESD

Just like the ministers in the above report, many people will notice a difference in the ability to generate static electricity when the air gets dryer (the % RH decreases).
Relative humidity (RH) directly affects the ability of a surface to store an electrostatic charge. As RH increases, the time a surface will hold a charge will decrease and the dissipation rate will increase. 

An example: walking across a carpet can yield a charge of 35kV at 10% RH (very dry air) but will drop significantly to 7.5kV at 55% RH. In an electronics manufacturing environment lower humidity may result in lower output from production due to an increase in ESD events during manufacturing processes.

A normal range for humidity in an electronics manufacturing environment is be between 30% RH and 70% RH. Some facilities try to maintain a constant moderate RH (~50%), whereas other environments may want lower % RH due to corrosion susceptibility to humidity sensitive parts.
The recommended humidity range is usually determined by the specifications of the devices and components being assembled. Increasing the humidity in an electronics manufacturing facility can help to reduce ESD events but increased humidity can lead to other unwanted quality issues in sn electronics manufacturing environment such as corrosion, soldering defects and the popcorn effect on moisture sensitive devices.

The popcorn effect
The popcorn effect (Source)

Dealing with dry air in an EPA

While not a replacement for grounding, shielding or ESD working surfaces, ionisation can mitigate ESD events in areas where dry air is normal. For more information on ionisation and the different types of ionisers, we recommend reading these two posts:

In summary, worksurface ionisers (Bench Top and Overhead Ionisers) produce positively and negatively charged ions that are moved to the controlled area with fan driven airflow. Point-of-use air ionisers use compressed gas to combat electrostatic attraction neutralising charges on particles causing contamination or visual defects on products.

Using a point-of-use air ioniserUsing a point-of-use air ioniser

The ESD Standard on Relative Humidity

The ESDA’s TR20.20-2008 discusses RH in a few different places. Some significant statements are listed below.

ESD Handbook ESD TR20.20-2008 section 2.3 Nature of Static Electricity:
The moisture level in the air, or relative humidity in the environment, are important considerations in the liberation and accumulation of static electricity. It is well known that static electricity in the form of static cling and static shocks are more prevalent when the air is dry. Heating interior air in the winter months dries out the already dry air in the higher latitudes. Static charge accumulation is easier on dry materials since moisture on surfaces tends to allow charges to slowly dissipate or recombine.
However, it is impractical to use humidity control alone to provide static control since static charges are developed even at relative humidity levels of 90% and greater. For most situations, 30 to 70% RH is considered the appropriate range. Special areas, such as wafer fabrication, may require lower humidity control for processes that are affected by moisture (e.g., photoresist application). Soldering is known to be affected by high relative humidity conditions (>70%). For areas that have low ambient humidity, ionization is an important consideration to aid in reducing charge accumulation levels and provide neutralization of charges after they are developed but before they can cause difficulties.

ESD Handbook ESD TR20.20-2008 section 5.3.16 Humidity:
Humidity is beneficial in all ESD control program plans. Contact and separation of dry materials generates greater electrostatic charges than moist materials because moisture provides conductivity that helps to dissipate charge. For this reason, ESD effects are most noticeable in the winter since heating systems reduce building environment moisture. Geographic location (desert vs. coastland) is also a major contributor to ambient conditions inside buildings. Any circumstance that results in a low relative humidity will permit a greater accumulation of electrostatic charges. Relative humidity above 30% in ESD protective areas is desirable as long as other adverse conditions are not created as a result of humidity levels. Generally speaking an upper limit of 70% is desirable to prevent corrosive effects on the metal portions of electronic devices and assemblies.
Besides the increasing propensity to generate electrostatic charges on dry materials in general, performance of many ESD protective materials degrade. In fact, when exposed to low humidity conditions, some ESD protective materials become totally ineffective or become sources of electrostatic charges. Therefore, evaluation of ESD control materials should include performance testing in controlled environments at the lowest expected operating relative humidity level. Manufacturers of ESD protective materials should be able to provide performance data in regards to relative humidity. Likewise, materials should be tested in moderate humidity conditions as well to ensure they do not become “too conductive” and present a potential safety hazard to personnel working with substantial voltages. See the Personnel Safety section of this handbook for further guidance in this area.
Humidity control in factories or physically large areas or buildings can be difficult and expensive. In smaller rooms or areas, it may be possible to use portable humidifiers to raise the immediate area humidity. However, in large facilities and factories the environmental systems many need to include steam generation and monitoring equipment to control humidity. This type of equipment is expensive to install and purchase especially in pre-existing facilities. To reduce the total cost impact, companies should consider the need for humidification equipment when planning new facility construction.

ESD TR20.20-2008 can be purchased directly from the ESD Association.

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