Category Archives: ESD Information

Webinar: Wrist Straps and ESD Control

DescoEurope-Webinar_2020-05-28-Banner

Desco Europe manufactures a variety of wrist straps made from various materials. Knowing how these wrist straps work and differ from each other is vital for any ESD Control Plan.

This webinar will include the following about Wrist Straps:

  • How they work
  • Performance advantages
  • Testing and monitoring options
  • Q and A with our experts

WHEN: Thursday May 28, 2020 at 10am BST

Click HERE to register.

Webinar: Ionisation in Electronics Production

DescoEurope-Webinar_2020-05-21-Banner

A complete static control programme must deal with isolated conductors and insulating materials that cannot be grounded. This is where ionisation plays a key role.

This webinar will include the following:

  • Industry Requirements for Ionisation
  • Understanding Ionisation
  • Products and Applications
  • Q and A with our experts

WHEN: Thursday May 21, 2020 at 10am BST

Click HERE to register.

 

Webinar: Requirements for an ESD Work Surface

DescoEurope-Webinar_2020-05-14-BannerESD Work Surfaces are a key part of all ESD Control Plans. Any surface that an “exposed” ESD Susceptible Device is placed upon can be considered an ESD Work Surface. Yet, with a variety of different materials available for differing applications, how do you choose the right surface for you?

This webinar will include the following:

  • Industry Standards
  • Types and Functionality
  • Grounding
  • Testing Methods
  • Maintenance
  • Q and A with our experts

WHEN: Thursday May 14, 2020 at 10am BST

Click HERE to register.

Webinar: Selecting A Personnel Grounding Tester

DescoEurope-Webinar_2020-05-07-BannerThe testing of wrist straps, foot grounders, and other personnel grounding devices is a vital part of any ESD Control Plan. Yet, with a variety of testers available for differing applications, how do you know which personnel grounding tester is right for your application?

This webinar will include the following:

  • Importance of Periodic Touch Testers in ESD control programs
  • Preferred testers for different applications
  • Q and A with our experts

WHEN: Thursday May 7, 2020 at 10am BST

Click HERE to register.

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.

 

 

Want to know more about Desco Europe and ESD Control? Sign-up to our flyers below:Sign-Up

 

 

 

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

Increase your Return on Investment with a successful ESD Control Programme

It is now well-known that electronic devices and systems can be damaged by exposure to high electric fields as well as by direct electrostatic discharges. Many companies implement an ElectroStatic Discharge (ESD) Control Programme with the aim of improving their operations. Effective ESD control can be a key to improving:

  • Productivity,
  • Quality and
  • Customer satisfaction.

A successful ESD Control Programme can also save you money which we want to focus on in today’s post.

Types of ESD Damage
There are two types of ESD damage:
1) catastrophic failure and
2) latent defects.

While catastrophic failures cause an ESD sensitive item to be damaged permanently, latent defects only partially degrade an ESD sensitive item that is exposed to an ESD event. It may continue to perform its intended function and may not be detected by normal inspection. However, intermittent or permanent failures may occur later. Even if an ESD sensitive component has quite a high withstand voltage and no catastrophic failure has been caused, latent defects may still make your life miserable.

Types of ESD DamageTypes of ESD Damage

A catastrophic failure of an electronic component can be the least costly type of ESD damage as it may be detected and repaired at an early manufacturing stage.
Latent damage caused by ESD is potentially costlier since damage occurs that cannot be felt, seen or detected through normal inspection procedures. Latent defects can be very expensive as the product passes all inspection steps and the product is completed and shipped. Latent defects can severely impact the reputation of a company’s product. Intermittent failures after shipping a product can be frustrating, particularly when the customer returns a product, reporting a problem which the factory again fails to detect. It consequently passes inspection and the product is returned to the customer with the problem unresolved.

Implementing an ESD Control Programme
A prerequisite of ESD control is the accurate and consistent identification of ESD susceptible items. Some companies assume that all electronic components are ESD susceptible. However, others write their ESD control plan based on the device and item susceptibility or withstand voltage of the most sensitive components used in the facility. A general rule is to treat any device or component that is received in ESD packaging as an ESD susceptible item.

The Organization shall prepare an ESD Control Program Plan that addresses each of the requirements of the Program. Those requirements include:

  • training
  • compliance verification
  • grounding / equipotential bonding systems
  • personnel grounding
  • EPA requirements
  • packaging systems
  • marking.” [EN 61340-5-1 clause 5.2.1 ESD control program plan]

Each company has different processes, and so will require a different blend of ESD prevention measures for an optimum ESD control program. It is vital that these measures are selected, based on technical necessity and carefully documented in an ESD control program plan, so that all concerned can be sure of the program requirements.” [EN 61340-5-1 Introduction]

Increasing Return on Investment with an ESD Control Programme
When it comes to reducing quality failures due to ESD, a thorough ESD Control Programme that is followed throughout the receiving, manufacturing, storage and shipping departments, is essential.

Below are two case studies that show what return on investment (ROI) can be achieved from implementing an ESD Control Programme.

1. AT&T
Former ESD Manager Terry O’Malley collected data for their Albuquerque and St. Louis facilities. The graph clearly displays a reduction in return and repair costs of more than 50% after an ESD Control Programme was implemented.

AT&TROI for AT&T (Source)

2.Lucent Technologies
The below overview shows the relationship between the relative cost benefits and compliance to Lucent’s ESD Control Programme. You can expect a typical ROI of 1,000% for a strict ESD Control Pogramme used by Lucent.

Lucent“Cost Benefit and ESD Control Programme Compliance” Relationship for Lucent (Source)

Organisations like AT&T, Motorola, Agilent Technologies and IBM were able to demonstrate the benefits of implementing an ESD Control Programme. In each of these companies, the introduced programme resulted in a substantial return on their original investment. The only way to accurately calculate the return on investment (ROI) from an ESD Control Programme, is to track the return, repair and scrap cost data before and after the introduction.

Even if your company is unable to track detailed data, it is still worth investing in an ESD Control Programme. “A properly implemented ESD program can have an ROI exceeding five to one within six months.” (Source)

Conclusion
As electronic technology advances, electronic circuitry gets progressively smaller. As the size of components is reduced, so is the microscopic spacing of insulators and circuits within them, increasing their sensitivity to ESD. Therefore, the need for proper ESD protection increases every day – not just to protect sensitive devices but also to allow companies to survive, be profitable and grow.
Independent consultants and corporate studies have found that ESD losses can be as high as 10% of annual revenues with an estimated average negative impact of 6.5% of revenues. Based on 1997-2001 production data, the international electronics industry is losing in excess of $84 billion every year. Other than increasing sales, ESD control is the single most profitable opportunity for our industry in today’s economic conditions.” (Source)

A proper ESD control programme will increase profitability of a company by:

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

 

 

 

 

References:
Michael T. Brandt: What does ESD really cost?
Ryne C. Allen: ESD Control and ROI

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:

Is air humidification a necessity for ESD Control?

Have you ever walked across the car park on a bright cold winter’s day only to get zapped by your car’s door handle? Yup, we’ve all been there and it’s commonly known that these ‘zaps’ are much more frequent in cold dry weather. It begs the question: if I don’t get zapped when the air is moist, will using air humidifiers in a manufacturing environment prevent ESD damage of sensitive components? Let’s find out!

Humidity
Humidity describes the amount of water vapour in the air. There are 3 main measurements of humidity with the most common one being the relative humidity (RH). It is expressed in percent and describes “how much humidity there is in the air, compared to how much there could be. Meteorologists often use the relative humidity as a measurement to describe the weather at various places.” [Source]
At 0% the air is completely dry; at 100% it is so moist that mist or dew can form. The optimum relative humidity level is somewhere between 40% and 60%:

  • A lower relative humidity increases charge generation as the environment is drier.
  • If the humidity level is too high, condensation can form on surfaces.

Charge Generation and ElectroStatic Discharge (ESD)
The simple separation of two surfaces generates an ElectroStatic charge. Examples:

  • Unwinding a roll of tape
  • Gas or liquid moving through a hose or pipe
  • A person walking across a floor with heels and soles contacting and separating from the floor

Generating Charges by walking across a CarpetWalking across a floor generates ElectroStatic charges

The amount of static electricity generated varies and is affected by materials, friction, area of contact and the relative humidity of the environment. A higher charge is generated at low humidity, in a dry environment.
Once an item has generated a charge, it will want to come into balance. If it is in close enough proximity to a second item, there can be a rapid, spontaneous transfer of electrostatic charge. This is called discharge or ElectroStatic Discharge (ESD).

Going back to our earlier example of getting a zap from your car’s door handle:

  1. Charge generation: you walk across the car park with your soles contacting and separating from the floor. A charge is built-up on you.
  2. ElectroStatic Discharge (ESD): you touch the door handle. Charges move from your body to your car until both are balanced out.

Impact of relative humidity on ESD
Many people will notice a difference in the ability to generate static electricity when the air gets dryer (relative humidity decreases). Relative humidity (RH) directly affects the ability of a surface to store an electrostatic charge. “With a humidity level of 40% RH, surface resistance is lowered on floors, carpets, table mats and other areas. … the moisture in the air forms a thin protective “film” on surfaces that serves as a natural conductor to dissipate electric charges. When humidity drops below 40% RH, this protection disappears and normal employee activities lead to objects being charged with static electricity.” [Source]

PCB-Damage

In an electronics manufacturing environment lower humidity may result in lower output from production due to an increase in ESD events during manufacturing processes.

Air Humidification and ESD
Air humidifiers are used to add moisture to the air and are commonly used in drier environments to keep humidity at a constant (optimum) level. Given that a lower humidity level increases the risk of ESD events, the obvious questions are:

  1. Can air humidifiers replace normal ESD Control measures?
  2. Are air humidifiers required for complete ESD protection?

Let’s address both of these questions:

  • Let’s be very clear about one thing here: air humidifiers cannot replace ESD Control measures.As explained further above, ESD is caused by two items that are at a different electrostatic equipotential and want to equalise their charges. Adding moisture to the air using humidifiers will not stop this discharge from happening. The only thing you may achieve is a reduction in the number of ESD events. BUT: they will still happen; just walking across a carpet will generate a charge on an operator. If they then touch an ESD sensitive component, discharge will still occur and may damage the component. No humidifier in the world will prevent this.
    The only way to control electrostatic charges on a person or object is through ESD grounding – this will ensure any charges generated dissipate to earth:

    • Operators need to be grounded using wrist straps or a footwear/flooring system.
    • Surfaces need to grounded using appropriate matting and ground cords.

    For more information on how to create a ESD workstation and how to correctly ground all elements, have a look at this post.

EBP-Bar-for-Flyer

Grounding of an operator using a wrist strap

  • Low air humidity can increase the number of ESD events so it may make sense to keep a factory at a higher humidity level. However, there are many other factors that come into play when choosing the ‘right’ humidity for a manufacturing environment. 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 an electronics manufacturing environment such as corrosion, soldering defects and the popcorn effect on moisture sensitive devices.
    A normal range for humidity in electronics manufacturing is 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.
    And remember: you will not eliminate ESD by using humidifiers and keeping humidity levels at a higher humidity level. You need an ESD Control Programme in place to avoid ESD and associated damages.

Conclusion
A lower relative humidity level increases charge generation as the environment is drier. This will result in more ESD events which can potentially damage sensitive components. The only way to protect sensitive components from ESD damage is by having proper ESD control measures in place and connecting operators, objects and surfaces to ground. This will ensure each element is kept at the same electrical potential and any electrostatic discharge is being removed to ground.
Humidification can help reduce the number of ESD events in an electronics manufacturing environment but at the same time there are other factors (e.g. moisture sensitivity of components) that need to be considered, too.

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