Category Archives: Floor Mats and Accessories
Static discharges can be noticed when you touch an object of different electrical potential such as a door knob, and a bolt of electricity flows from your charged body to the door knob. This flow of electricity is actually a result of the stored static charge that is being rapidly transferred to the knob. This discharge that can be felt as well as seen, is commonly referred to as an electrostatic discharge, or “ESD”.
The generated static charges are a potentially costly occurrence for office and factory employers. You will learn in today’s post how they can easily be controlled with different types of floor material.
Static Charge Generation from Flooring
When a person walks across a floor, a triboelectric charge builds up in the body due to the friction between the shoes and floor material. The simple separation of two surfaces (such as a person walking across a floor with soles contracting and separating from the floor) can cause a transfer of electrons resulting in one surface being positively and the other one negatively charged, resulting in static charges.
Generating Charges by walking across carpet
It is not necessarily the static charge generated in the body that does the damage as much as it is the difference in potential that creates an electrostatic discharge.
The problem with ESD
The generation of a static charge can pose quite a problem for environments that contain sensitive equipment or components that are vulnerable to static damage, such as electronics manufacturing, repair facilities and medical facilities, including computer rooms and clean rooms.
Controlling the damage and costs caused by ESD is usually the main concern that drives a company to implement a static control programme. The costs involved with static damage not only include the immediate cost of the damaged component, but the contributing cost of diagnostic, repair and labour that is needed to replace or fix the component. In many cases the labour involved can far exceed the component cost.
There are several options available on the market ranging from coatings (floor finish or paint) to coverings (vinyl or rubber). The choice of material depends on the mechanical and optical properties required as well as the available budget.
In general, floor coverings will last longer (10 years or more) than a floor coating. They are more durable and have a specific resistance to ground that remains constant over time.
Types of Floor Coverings – click here for more information
Coatings are easier to apply and repair and their initial cost is considerably lower. Coatings are usually applied to existing floors and often serve to convert a conventional floor into an ESD floor. However, regular maintenance is required as coatings will lose their ESD properties over time.
1. Floor Coatings
- Antistatic Coating:
Conventional carpets can be treated with an Antistatic Coating or other treatment. It is required that the treatment be replenished on the carpet as it wears away due to foot traffic.
ESD carpet is available but proper maintenance is very important.
- ESD Floor Finish:
Existing hard surfaces (e.g. concrete, sealed or painted wood, linoleum, asphalt) can be treated with ESD Floor Finish to eliminate the need for ESD control flooring. Repeat applications are required periodically to keep ESD properties within specification.
- ESD Paint:
Paint is ideal for providing a cost effective static-free environment and is very effective as a static control floor coating for electronics manufacturing, assembly and storage. It controls dissipation of static electricity and provides path to ground.
2. Floor Coverings:
Floor coverings will have either “conductive” or “dissipative” electrical properties:
- Conductive materials have a resistance to ground (RG) of greater than 1 x 103 ohms but less than 1 x 105
- Dissipative materials have a resistance to ground (RG) of greater than 1 x 105 ohms but less than 1 x 1012
It is recommended to use conductive flooring material; EN 61340-5-1 requires ESD flooring to be less than 1 x 109 ohms (RG). The same standard requires a person/footwear/flooring to be less than 3.5 x 107 ohms (resistance in series of operator plus footwear plus floor). Remember that floors get dirty which can raise floor resistance. Therefore, it is good to start off with a floor that is conductive (less than 1 x 106 ohms). So even if the resistance increases, you’re within the required limits of the ESD Standard.
ESD control carpets are made with static dissipative yarn and only require that the yarn be kept clean and free of insulative dirt, dust and spray cleaners.
Types of matting range from vinyl to rubber and anti-fatigue matting.
Vinyl is generally cheaper and provides high resistance to many chemicals. Rubber on the other hand is more durable and can withstand extreme hot and cold temperatures. Anti-fatigue matting (AFM Series) is designed to provide comfort for personnel that must stand or walk for long periods.
Considerations when using Flooring Materials
EN 61340-5-1 requires that all conductors in an ESD protected area, including personnel, must be grounded. This includes ESD flooring; it must be electrically connected and attached to a known ground. The Desco Europe floor mat ground cord 231265 is just one option for grounding floor matting.
2. Periodic Verification
All ESD control items (including ESD flooring) have to be tested:
- Prior to installation to qualify product for listing in user’s ESD control plan.
- During initial installation.
- For periodic checks of installed products as part of EN 61340-5-1 clause 5.2.4 Compliance verification plan.
Measuring Surface Resistance of ESD Floor Matting – click here for more information
A surface resistance meter can be used to verify compliance of the ESD floor with the ESD standard.
3. Person/Footwear/Flooring System
ESD flooring does not ensure protection from ESD damage unless operators walking across the ESD floor wear ESD footwear, either ESD shoes or ESD foot grounders.
ESD foot grounders are designed to reliably contact grounded ESD flooring and provide a continuous path-to-ground by removing electrostatic charges from personnel. They are easy to install and can be used on standard shoes by placing the grounding tab in the shoe under the foot.
Foot grounders must be worn on both feet to maintain the integrity of the body-to-ground connection Wearing a foot grounder on each foot ensures contact with ground via the ESD floor even when one foot is lifted off the floor. This will more reliably remove static charges generated by human movement.
Desco Europe offer a number of different foot grounder types for your requirements.
Static charges can easily be controlled with different types of floor material which vary in their properties, cost and durability. The best static control systems are not only the ones that protect sensitive components and equipment but are: A) at hand and readily available, B) easily maintained. Floor coverings are long lasting and maintain their ESD properties over time, while existing floors can be economically converted for use in an ESD control program using various types of coatings.
Remember that all ESD control items such as flooring, personnel grounding and specialty equipment should be grounded and tested periodically to verify all components are within specification.
Not sure which ESD flooring is right for you? Request a free ESD Survey at your facility by one of our knowledgeable representatives to evaluate your ESD programme and answer any ESD questions!
Let’s face it: nobody likes ‘change’! We all like our little routines and feel comfortable with what we know.
BUT: without ‘change’, everything would stay the same; ultimately humanity would stagnate and die. So, let’s think of ‘change’ as an opportunity: to improve, to progress, to be better! That’s exactly the reason behind the latest major change to the ESD Standard: ensuring your ESD Programme is the best one yet and protects your ESD sensitive devices 110%.
You will have learnt by now that a fundamental principle of ESD control is to ground conductors including people at ESD protected workstations. Wrist straps are the first line of defence against ESD. A wrist strap is the most common personnel grounding device and is required for sitting operators.
A Flooring / Footwear system is an alternative for personnel grounding for standing or mobile workers. You will know that ESD footwear must be used in conjunction with an ESD floor and needs to be worn on both feet. But did you know that the latest ESD Standard now requires an Operator Walking Test and conformance to Operator Resistance Measurements?
The importance of the Walking Test
- The Walking Test is necessary to qualify the Footwear / Flooring personnel grounding system for certification to EN 61340-5-1.
- The Walking Test can provide records to prove that the Footwear / Flooring personnel grounding system used as a static control method is providing the performance expected.
- The Walking Test is also used when testing samples for qualification of a Footwear / Flooring personnel grounding system or on an existing installed floor when evaluating a change in footwear or flooring maintenance.
Performing the Walking Test
The Walking Test is completed with a device which measures the human body voltage generated while walking. There are different units on the market: some of them will display the results on the unit itself; others connect to a computer and use software to analyse the data.
All units work in the same way though:
- You wear your ESD footwear.
- You hold a small probe (more like a rod) connected to the meter measuring your body voltage.
- While holding the probe, you walk across your ESD floor.
- You record the results and either calculate the average of the 5 highest peaks or let the software (supplied with some units) do the calculation for you.
Results of the Walking Test
The Walking Test simulates a real-world working environment with operators walking through an ESD Protected Area. The results will show the effectiveness of a Footwear / Flooring system to remove charges from the operator through the floor to ground. If the system is working properly, no more than 100 Volts will be generated on the body.
For any Footwear / Flooring system, EN 61340-5-1 requires:
- the resistance from body to ground to be <109 ohms AND
- the body voltage to be < 100 Volts (average of 5 highest peaks).
Remember that the Walking Test must be performed on ALL ESD floors using ANY ESD footwear you may be using. So, if you have 2 EPAs with different flooring and use 2 different types of footwear (e.g. shoes, foot grounders), you need to perform a total of 4 tests to cover all possible options.
Also, if you make any changes to your footwear or flooring (e.g. you change suppliers for your foot grounders or ESD floor cleaner), the Walking Test needs to be repeated to ensure compliance with the ESD Standard.
If you require further information on the changes to the ESD Standard or need the Walking Test performed in your facility, get in touch.
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.
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 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.
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.
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.
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:
The Personnel Grounding Checklist
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.
We’ve previously learned that the simple separation of two surfaces can cause a transfer of electrons resulting in one surface being positively and the other negatively charged. A person walking across a floor and soles contracting & separating from the floor is such an example. The resulting static charges that generate are an annoying and costly occurrence for office and factory employees. The thing is, they can easily be controlled with existing carpets and tiled floors. Learn how in today’s post.
What is Static Electricity?
Static electricity is an electrical charge that is at rest – as opposed to electricity in motion or current electricity. Static charges can be generated by either friction or induction. Typical examples are the Wimshurst machine that uses friction and the Van de Graaff generator using electrostatic induction.
How is Static Electricity generated?
The most common generation of static charge is the triboelectric charge or the friction electricity developed when rubbing together and then separating two masses. For example, when two blocks are rubbed together and then separated, a triboelectric charge is developed on each block. The two blocks will have opposite polarities; one will be negatively charged and the other will be positively charged. Other examples include:
- Unwinding a roll of tape
- Gas or liquid moving through a hose or pipe
- A person walking across a floor and soles contacting & separating from the floor.
Charge Generation: Unwinding a Roll of Tape
Static Charge Generation from flooring
When a person walks across a carpeted or tiled floor, a triboelectric charge builds up in the body due to the friction between the shoes and floor material. The more you generate, the greater the voltage potential developing in the body – you are basically acting as a capacitor.
Everyone’s capacitance to hold charges is different. However, a sure sign of static presence is hair standing on end or static discharge sparks. Static discharges can be noticed when you touch an object of lower electrical potential such as a door knob, and a bolt of electricity flows from your charged body to the door knob. This flow of electricity is actually a result of the stored static charge that is being rapidly discharged to the lower potential object.
This discharge that can be felt as well as seen, is commonly referred to as an electrostatic discharge, or “ESD”.
Generating Charges by walking across carpet
It is not necessarily the static charge generated in the body that does the damage as much as it is the difference in potential that creates an electrostatic discharge. The ESD event can be felt at the human sensation threshold of 3000 volts. If one feels or sees the static shock, it is a minimum of 3000 volts. The potential static charge that can develop from walking on tiled floors is greater than 15,000 volts, while carpeted floors can generate in excess of 30,000 volts.
The problem with ESD
The generation of a static charge can pose quite a problem for environments that contain sensitive equipment or components that are vulnerable to static damage, such as electronic manufacturing, repair facilities or medical facilities including computer rooms and clean rooms.
Controlling the damage and costs caused by ESD is usually the main concern that drives a company to implement a static control programme. The costs involved with static damage not only include the immediate cost of the damaged component but the contributing cost of diagnostic and repair labour that is needed to replace or fix the component. In most cases, the labour involved will far exceed the component cost. If the damaged component performs enough to pass Quality Control (QC), it is called a soft failure as opposed to a hard failure when it does not pass the QC. It is far more expensive for a soft failure occurring at the manufacturer which then leads to a hard failure in the field which escalates product returns and field service cost.
As with any type of control, there are several levels of protection. The method for choosing the necessary degree of ESD protection starts with defining your static sensitivity for electronic components. The ESD Association defines different classes of sensitivity for the HBM (Human Body model) and CDM (Charged Device Model).
ESDS Component Sensitivity Classification
How can you determine the class of sensitivity of the devices within your facility? Look at your product flow through your facility, start at receiving and walk the components or products through until they are at dispatch ready to ship. Chances are, you have several different product flows through your facility. Each flow or loop will have specific components that enter or travel the loop. Make a list of all the sensitive components in each loop and determine the static voltage sensitivity or rating from each of the manufacturers. The lowest voltage sensitivity will dictate the sensitivity class of each loop. The philosophy here is “the chain is only as strong as the weakest link”. Each loop should have the required ESD protection for the most sensitive components that will travel this loop. This will define what class of protection is needed for each loop. You can have different class loops as long as the loops are closed, not allowing other components in. The objective here is to define a static control programme to safeguard your most sensitive component.
ESD control carpet and conventional carpet with antistatic treatments can still generate up to 1,500 volts, far exceeding the class 1 limits for the HBM. These carpets, however, when properly maintained, can provide safe grounding and electrostatic propensity below the class 2 and 3 sensitivity range.
Proper maintenance for ESD control carpets is rather simple but very important. For conventional carpets that are treated with a topical antistat or other treatment, it is required that the treatment is replenished on the carpet as it wears away due to foot traffic. The amount of treatment on the carpet can be determined by testing with a surface resistance meter. The higher the resistance readings of the floor, the lower the amount of static control treatment that is present on the carpet. The level of treatment should be monitored by resistance readings and kept between 1 x 106 and 1 x 1010 ohms. Some ESD floor finishes can be used as a carpet treatment. This requires a simple spray bottle filled with 50/50 mix of ESD control floor finishes and water. Always check with the floor finish manufacturer before use. Application of diluted floor finish usually requires a 1 to 2 spray coat on the carpet depending on the level of resistance you want.
Reztore® Topical Antistat – for more information click here
ESD control carpets are made with static dissipative yarn and only require that the yarn is kept clean and free of insulative dirt, dust and spray cleaners.
ESD control floor tiles can also generate triboelectric charges depending on the construction of the tile. The tile (dissipative or conductive) may have voids between the impregnated conductive sections which allows triboelectric charges to be generated and then drained. This cyclic voltage can be very harmful to sensitive components.
ESD control floor finishes alone can provide both non-triboelectric charging as well as a path to ground. Such floor finishes can be applied on many surfaces including sealed concrete, vinyl tile and especially ESD control tiles. If the ESD control tile is generating triboelectric charges, ESD control floor finish will complement these tiles with its non-triboelectric properties, as well as enhancing the surface’s electrical properties. The ease of maintenance for an ESD control floor finish is another benefit when used on top of any tile floor, especially carbon impregnated conductive tile that may form streaks of black carbon on the surface.
Statguard® Floor Finish – for more information click here
The best static controls are not only the ones that protect sensitive components and equipment but are: A) at hand and readily available, B) easily maintained. For these reasons, carpets and tile floors should not be overlooked as sources for static control. Existing carpet or tile floors can be easily included into an ESD control programme.
The purpose of an ESD protective working surface is to aid in the prevention of damage to ESD sensitive items (ESDS) and assemblies from electrostatic discharge. An ESD protective working surface provides protection in the following two ways:
- Providing a low charging (antistatic) working surface area that will limit static electricity to be generated below potentially damaging levels.
- Removing the electrostatic charge from conductive objects placed on the working surface.
1. Types of ESD working surfaces
ESD protective working surfaces are categorised into two general categories: conductive and dissipative.
A conductive working surface is defined by most documents as a material that has a surface resistance of less than 1 x 104 ohms. Conductive materials are the quickest to ground a charge but they can also cause damage by discharging too rapidly. Conductive materials are usually used as floor mats or flooring products.
A dissipative working surface is defined as being materials having a surface resistance of at least 1 x 104, but less than 1 x 109 ohms. Dissipative materials will dissipate a charge slower and are recommended for handling electronic components. Dissipative materials are usually the preferred choice for bench top working surfaces.
Most people in the industry consider working surfaces to be the second most important part of an ESD Control Programme, with personnel grounding being most important.
2. Grounding Methods for working surfaces
Method 1: Grounding via ground cords
- Vermason recommends using an earth bonding point cord when grounding via ground cords. Most earth bonding point cords will ground an ESD protective working surface and provide banana jacks for two wrist strap grounds.
Earth Bonding Point for each workstation
- An earth bonding point should be installed at each workstation and should be connected directly to a verified electrical system ground or to a verified grounding bus which is connected to the protective earth ground. Only one groundable point should be installed on a working surface.
- Wrist straps should never be grounded through a working surface, as the added resistance of the working surface material will prevent the wrist strap from operating properly.
Proper Grounding of Wrist Straps
Method 2: Grounding via a grounded conductive surface
- This alternate form of grounding should only be employed when using a homogeneous dissipative material with a volume resistance of less than 1 x 108
- The dissipative working surface may be placed on a properly grounded laminate, metal or other conductive surface. The working surface will electrically couple to the grounded surface and may not require a separate ground cord.
- When using this type of grounding method be sure to test that the working surface Rg is less than 1 x 109 ohms, tested per IEC 61340-2-3. Also consider increasing Compliance Verification test frequency.
Alternate Grounding Method via a Grounded Conductive Surface
3. Groundable Point Installation
Before installing a groundable point on your work surface you must first determine whether you will need a male stud or female socket, the type of snap hardware and the desired location.
There are generally 3 types of groundable points available for working surface mats: screw-on snap kits, push & clinch snaps (with prongs) or stud & posts sets (requiring installation using a punch and an anvil).
Snap Kits and Tools
- Determine the position of the grounding snap (one only per mat). Punch a hole through the material with a small Phillips screwdriver or awl.
- Insert the screw through the bottom on the snap fastener, the washer and the material. Affix the assembly with the conical nut supplied with the kit and tighten down the screws.
Installing a screw-on Mat Grounding Snap
Push & clinch snaps:
This snap is designed for use with any type of soft mat material: dissipative, conductive or multi-layered. It is recommended for use with three-layered material, because it provides better contact with the internal conductive layer. It is recommended that before inserting this snap, the mat be punctured with a sharp tool where the snap will be placed.
Centre the prongs on the snap assembly. Apply pressure to the snap until the prongs come through the back of the mat, then clinch over prongs making flat to the mat’s bottom side to secure snap as shown in the below picture.
Installing Push & Clinch Mat Grounding Snap
Stud & post sets:
This type of groundable point must be riveted through bench and floor mats to connect ground cords. A punch and anvil are simple but effective tools to achieve a neat finish with firm materials no more than 4mm thick.
- Punch a 5mm diameter hole at the desired location of the mat.
- Insert the post from underneath and apply the stud over the protruding post on the top side.
- Fit the anvil under the post and place the punch inside the stud and hammer the post (or use an arbor press) until it rolls and a tight assembly is achieved.
Using a Punch and Anvil to install Stud & Post Sets
4. Selection of Common Point & Floor Mat Grounding Systems
- Determine the type of common point grounding system you will use: barrier strip, bus bar, grounding block or common point ground cord. Vermason recommends the use of common point ground cords and earth bonding bars.
- If you determine that you will use ground cords, you must now determine the type of ground cord you will use for your workstation grounds. It is the user’s preference to use a ground cord with or without a current limiting 1 megohm resistor to ground working surfaces or floor mats. Selection of the ground cord is determined by user needs and specifications; the resistor is not for ESD control.
Examples of Grounding Cords
- Earth bonding point bars allow the grounding of multiple operators at one common ground point. They also mount easily under the front edge of a workstation benchtop.
Earth Bonding Point Installation
5. Mat Installation
- For best results, allow the mats to lay flat for about four hours at room temperature before installing. This will give the material time to flatten out from being rolled for shipment.
- Test all workstation grounds for proper resistance to ground.
- Lay the mat in position and snap the ground cord to it. Bring the other end of the ground cord to the common ground point (or earth bonding bar) and attach it using the ring terminal (or other termination device). The electrical systems junction box and connecting conduit should also connect to earth protective ground. Tie the ground wire to the bench to keep it out of the way and neat. You may cut and strip the ground wire to a shorter length and attach it with an extra ring terminal if required.
Note: DO NOT DAISY CHAIN. Because of the high resistances inherent to many types of protective surfaces, daisy chaining of these materials can cause the overall resistance to exceed the required limit of EN 61340-5-1.
ESD working surface should never be grounded in series, i.e. daisy chained
- If your kit includes a floor mat, you should duplicate step 2 and attach the floor mat ground to the same ground point as the working surface ground.
- Measure the resistance from the ground snap on the mat to the common ground point. It should read 1 megohm ±20 percent if you are using a ground cord with a resistor, and less than 10 ohms if you are using a ground cord without a resistor.
- If you have a surface resistance or resistance to ground tester available, you may wish to test the resistance to ground from the mat surface. Note: depending upon the accuracy of the instrument you are using, you may get a wide range of results in resistance to ground tests. In order to get the electrical readings specified per EN 61340-2-3, two 2.2kg electrodes are to be used. This will require a megohmmeter with 100 volt open test circuit voltage and two 2.2kg electrodes.
- If you are using a mat kit that includes the wrist strap, install the wrist strap directly to the common point mat ground cord. Again, test the resistance from the backplate of the wrist strap to the common ground point. It should read 1 megohm ± 20 percent.
Adding a Wrist Strap
- Your completed installation of an ESD workstation should comply with one of the electrical diagrams illustrated below.
Proper wiring diagrams for conductive and dissipative ESD workstations
6. Maintenance and Cleaning
For optimum performance, periodic cleaning is required following the manufacturer’s recommendations.
BE SURE YOU TEST ALL GROUNDS AND THE WRIST STRAP FREQUENTLY
Today’s post concludes our 2-part series on periodic verifcation. If you have missed the first part, you can catch-up on it here. As a reminder, it is recommended to regularely check all ESD Protected Area (EPA) products to ensure they are working correctly. After covering working surface matting and wrist straps in last week’s post, we’ll jump right in to discuss the remaining components in your EPA.
A flooring / footwear system is an alternative for personnel grounding for standing or mobile workers. Foot grounders quickly and effectively drain the static charges which collect on personnel during normal, everyday activities. Foot grounders should be used in conjunction with floor surfaces which have a surface resistance of less than 1010 ohms.
As ESD floors get dirty, their resistance increases. For optimum electrical performance, floor matting must be cleaned regularly using an ESD mat cleaner, such as Reztore™ Surface & Mat Cleaner. Do not use cleaners with silicone as silicone build-up will create an insulative film on the surface.
Dissipative floor finish can be used to reduce floor resistance. Periodic verification will identify how often the floor finish needs to be applied. As the layer(s) of dissipative floor finish wear, the resistance measurements will increase. So, after some amount of data collection, a cost effective maintenance schedule can be established.
Testing floor matting
Floor matting can be checked using a resistance meter. Surface resistance meters are designed to measure resistance point-to-point (Rp-p) or surface to ground (Rg) in accordance with EN 61340-5-1 Electrostatics and its test method IEC 61340-2-3.
ESD Shoes or Foot Grounders play an essential part in the flooring/footwear system. For more information on how to ground moving personnel effectively, check this post.
Before handling ESD sensitive devices, visually inspect your ESD footwear for any damage. Just like wrist straps, footwear should be checked while being worn using a wrist strap/footwear tester.
Checking foot grounders using 222567
Records of each test should be kept. Analysis and corrective action should take place when a footwear tester indicates a failure. Footwear needs to be checked daily.
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.
Make sure your ESD shielding bags are un-damaged
It is up to the user to determine if a shielding bag is suitable for re-use or not. The testing of every bag before re-use is not practical. Many companies will discard the shielding bag once used and replace it with a new one. Others will use a system of labels to identify when the bag has gone through five handling cycles:
- Non-reusable labels are used that require the label be broken to open the bag.
- The bag is then resealed with a new label.
- When there are five broken labels, the bag is discarded.
The same principle applies to other ESD packaging, e.g. component shippers.
Ionisers are intended to neutralise static charges on insulators thereby reducing their potential to cause ESD damage. However, poorly maintained ionisers with dirty emitter pins and out-of-balance ionisers can put a charge on ungrounded items.
Remember to clean ioniser emitter pins and filters regularly. You can now even purchase ionisers that will alarm when emitter pins need to be cleaned or the ioniser is out of balance.
Checking ionisers using 50598
The EMIT Ionisation Test Kit 50598 allows the Digital Static Field Meter 50597 to be used to measure the offset voltage (balance) and charge decay of ionisation equipment. The Test Kit also includes a Charger used to place a ±1000V charge on the 50567 Conductive Plate, making it possible to measure the discharge times of air ionisation equipment per ANSI/ESD SP3.3 Periodic Verification of Air Ionizers.
Wrist Strap/Footwear and Resistance Testers etc.
So you check your wrist straps and/or footwear and bench and/or floor matting regularly. But have you remembered the testers themselves? What good do all the checks do, if the testers you use are out-of-spec and show you incorrect results?
Yearly calibration is recommended – many manufacturers offer a calibration service or alternatively you can purchase calibration units from them and perform the calibration yourself.
So there you have it – a list of the most commonly used products in your ESD Protected Area (EPA) that you should check on a regular basis.
Questions for you: Do you have a verfication plan in place? If so, how often do you check your ESD protection products?
The purpose of ESD protective flooring is to aid in the prevention of damage to ESD sensitive items (ESDS) and assemblies from electrostatic discharge.
ESD protected area products should be tested:
- Prior to installation to qualify product for listing in user’s ESD control plan.
- During initial installation.
- For periodic checks of installed products as part of IEC 61340-5-1 Edition 1 2007-08 clause 5.2.3 Compliance verification plan.
Testing the flooring in an ESD protected area
When floors get dirty, their floor resistance can increase. Therefore it is recommended to check ESD flooring regularly using a resistance checker. Vermason Surface Resistance Meters are designed to measure resistance point-to-point (Rp-p) or surface to ground (Rg) in accordance with EN 61340-5-1 Electrostatics and its test method IEC 61340-2-3.
Overview of available Surface Resistance Testers from Vermason:
- Surface Resistivity Checker: 225717 and 225718
- Analogue Surface Resistance Meter: 222637 and 222635
- Surface Resistance Meter: 222643 and 222642
- Low Resistance Tester: 222645
by Rick Cardinale, Bird Electronic
Bird Electronic, founded in 1942 by J. Raymond Bird, soon became a leader in radio frequency instrumentation. Today, Bird also has moved into digital instrumentation test equipment.
With the development of digital instrumentation came the increased need for controls to prevent ESD events. Improving ESD protection has been an ongoing process since the late 1980s. In 1997, the company determined that an automated PCB production line would be installed and that the entire manufacturing area should be protected against ESD.
This decision led to an evaluation of ESD protective flooring. In 1998, 20,000 square feet of conductive floor tile were installed in the main production area. To help brighten the area, white tile was selected. The floor resistance measured less than 1.0 × 10^6 ohms.
A bright, high-gloss appearance was part of the selection criterion for the floor. While the electrical properties were unchanging, by 1999, the floor was starting to dull. It was being maintained like a regular tile floor. No waxes or finishes were used; however, the tile manufacturer did recommend using buffing pads.
After consulting with the tile manufacturer and the installer, maintenance was increased to sweeping clean and damp mopping two times per week and buffing once per month. Monthly floor maintenance was $1,700 per month, a $20,400 annual expenditure.
In late 1999, the maintenance schedule was modified to add more buffing since this was the only way to keep the floor shiny. The floor now was swept and damp mopped weekly and buffed twice per month. The floor was clean and shiny, but the cost went up 41% to $2,400 per month, a $28,800 annual expenditure.
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