ESD Association

5 Common Mistakes in ESD Control & How to Avoid Them

Image scsstaticcontrol July 26, 2018 1

Many companies implement an ElectroStatic Discharge (ESD) Control Program with the aim of improving their operations. Effective ESD control can be a key to improving:

Productivity
Quality
Customer Satisfaction

Problems arise when an organization invests in ESD protective products and/or equipment and then misuses them. Misuse of ESD protective products and/or equipment wastes invested money and can also be causing more harm than good. Today’s blog post will highlight some of the major issues we have come across and how you can avoid or fix them.

About ESD Control and ESD Protection

Remember that for a successful ESD control program, 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.

Just like viruses or bacteria that can infect the human body, ESD can be a hidden threat unable to be detected by human eyes. Hidden viral/bacterial threats in hospitals are controlled by extensive contamination control procedures and protective measures such as sterilization. The same principles apply to ESD control: you should never handle, assemble or repair electronic assemblies without taking adequate protective measures against ESD.

Common Mistakes in ESD Control

1. Ionizers are poorly maintained or out-of-balance

If an ionizer is out of balance, instead of neutralizing 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.

Remember to clean emitter pins and filters using appropriate tools. Create a regular maintenance schedule which will extend the lifespan of your ionizers tremendously.

Consider using ionizers with “Clean Me” and//or “Balance” alarms. These will alert you when maintenance is required.

“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.”

[ESD TR20.20 Handbook Ionization clause 15.8 Maintenance / Cleaning]

If you would like to learn more about how ionizers work and what type of ionizer will work best for your application, check out this post for detailed coverage.

2. ESD Garments are Ungrounded

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. However, without proper electrical bonds to a grounding system they are not grounded!

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

“After verifying that the garment has electrical conductivity through all panels, the garment should be electrically bonded to the grounding system of the wearer so as not to act as a floating conductor.

This can be accomplished by several means:

Ground the garment to the body through a wrist strap-direct connection with an adapter.
Ground the garment through conductive wrist or heel cuffs in direct contact with the skin of a grounded operator.
Ground the garment through a typical separate ground cord, directly attached to an identified groundable point on the garment.
Garments should be worn with the front properly snapped or buttoned to avoid exposure of possible charge on personal clothing worn under the garment.”

[ESD TR20.20 Handbook Garments clause 19.4 Proper Use]

ESD clothing loses their ESD properties over time. It is therefore an important part of the ESD Control Program to incorporate periodic checks (see #3 below) of ESD garments.

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

3. No Compliance Verification Plan / Not Checking ESD Control Products

Companies can invest thousands of dollars in purchasing and installing ESD control products but then waste their investment by never checking their ESD items. This results in ESD equipment that is out of specification. Without the tools in place to check their ESD items, companies may have no idea if they are actually working correctly. Remember: ESD products (like any other product) are subject to wear and tear, and other errors when workstations get moved, ground cords get disconnected…etc. The list goes on.

When investing in ESD control products, make sure you also establish a Compliance Verification Plan. This ensures that:

ESD equipment is checked periodically
Necessary test equipment is available

“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.”[ANSI/ESD clause 7.4 Compliance verification plan]

We provide detailed instructions on how to create a Compliance Verification Plan in this post.

4. Improperly Re-Using Shielding Bags / 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.

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.

ESD shielding packaging is to be used particularly when transporting or storing ESD sensitive items outside an ESD Protected Area.

“Transportation of ESDS items outside an ESD Protected Area (hereafter referred to as “EPA”) requires enclosure in static protective materials, although the type of material depends on the situation and destination. Inside an EPA, low charging and static dissipative materials may provide adequate protection. Outside an EPA, low charging and static discharge shielding materials are recommended. While these materials are not discussed in

the document, it is important to recognize the differences in their application. For more clarification see ANSI/ESD S541. “

[ANSI/ESD Foreword]

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

5. Using Household Cleaners on ESD Matting

The use of standard household cleaners on ESD matting can put an ESD Control Program at risk and damage the ESD properties of items. Many household cleaners contain silicone or other insulative contaminants which create that lovely shine you get when wiping surfaces in your home. The problem is that silicone and other chemical contaminates can create an insulative layer which reduces the grounding performance of the mat.

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.

“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.”

[ESD TR20.20 Handbook Worksurfaces clause 10.5 Maintenance]

Conclusion

There are many more issues we see when setting foot into EPAs and the above list is by no means complete. These are the most common issues we’ve found when assessing EPAs.

It is important to train all personnel using ESD products and/or equipment to follow proper ESD control programs, and maintenance procedures to avoid common ESD control mistakes. Basic ESD control principles should be followed for an ESD control program to be successful:

Ground conductors.
Remove, convert or neutralize insulators with ionizers.
Shield ESD sensitive items when stored or transported outside the EPA.

What mistakes do you commonly see when walking through an EPA? Let us know what you commonly see in the comments and your solutions for fixing them!

For more information on how to get your ESD control program off the ground and create an EPA, check this post.

5 Tips For Using ESD Shielding Bags

Image scsstaticcontrol May 17, 2018 0

In a previous post we learnt how to select the correct ESD bag for your application, we want to focus on the next step: how to correctly use your ESD bag. We’ll use shielding bags as an example as they are the most commonly used ESD bags. However, the below can be applied to all types of ESD bags.

There are a few “dos and do-nots” you should keep in mind to ensure you get the most from your ESD bags. Nothing is worse than investing in all the right equipment and then using it incorrectly rendering all your efforts void. So, on that note, we have comprised a list of 5 tips for you on how to most efficiently use your shielding bags.

5 Tips On Efficient Use of Shielding Bags With ESD Sensitive Items:

1. Enclose Your ESD Sensitive Item with a Shielding Bag

Shielding bags should be large enough to enclose the entire product within. The shielding bag should be closed with a label or tape. Alternatively, you can use a zipper-style shielding bag. Following this advice ensures a continuous Faraday Cage is created which provides electrostatic shielding. This is the only way to ensure ESD sensitive devices placed inside the shielding bag are protected. If you are unfamiliar with the term “Faraday Cage”, scroll to the bottom of this page – we’ve included a more detailed explanation at the end of the post.

Enclose_Shielding_Bags — *Enclose your ESD sensitive item*

Please do not staple your shielding bag. The staple punctures the shielding layers and will provide a conductive path from the outside of the shielding bag to the inside. Charges outside the shielding bag could potentially charge or discharge to ESD sensitive components inside the shielding bag.

If you’re unsure as to what the correct size is for your application, catch-up on this post which will provide all the required information.

2. Remove Charges from Shielding Bags

When receiving an ESD sensitive device enclosed in a shielding bag, make sure you place the closed shielding bag on an ESD worksurface before removing the product. This will eliminate any charge that might have accumulated on the surface of the shielding bag.

3. Do Not Overuse Shielding Bags

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.

Dont_overuse_shielding_bags — *Don’t overuse shielding bags*

4. Shielding Bags Are Not A Working Surface

Do not use a shielding bag as an ESD worksurface. Although a shielding bag is safe to use around ESD susceptible products, it is not intended to be a worksurface for product. When working on ESD sensitive devices, do so using ESD worksurfaces that are grounded correctly.

*Don’t use shielding bags as your ESD worksurface*

5. A Shielding Bag Is Not A “Potholder” Or “Glove”

Do not use a shielding bag as an “ESD potholder” or “ESD glove”. This type of use offers no ESD protection to the product.

If you need to handle ESD sensitive devices, make sure you are properly grounded using wrist straps or heel grounders.

Shielding_Bags_are_no-Gloves — *Shielding bags are no “ESD glove” or “ESD potholder”*

Some of you may have read through this post and have stumbled across the term “Faraday Cage” as you have not come across it before. We’ve also mentioned it before when talking about storing and transporting ESD sensitive items. However, we’ve never actually explained what a Faraday Cage is – so let’s rectify that!

What Is A “Faraday Cage” Or “Faraday Shield”?

A Faraday Cage or Faraday shield is an enclosure formed by conducting material or by a mesh of conductive material. Such an enclosure blocks external static and non-static electric fields. Faraday Cages are named after the English scientist Michael Faraday, who invented them in 1836.

What Is An Example of Faraday Cage Effect?

An impressive demonstration of the Faraday Cage effect is that of an aircraft being struck by lightning. This happens frequently but does not harm the plane or passengers. The metal body of the aircraft protects the interior. For the same reason, a car may be a safe place during a thunderstorm.

How Is A Faraday Cage Effect Used In ESD Protection?

In ESD Protection, the Faraday Cage effect causes charges to be conducted around the outside surface of the conductor. Since similar charges repel, charges will rest on the exterior and ESD sensitive items on the inside will be ‘safe’.

Examples of ESD control products that provide a Faraday Cage or shielding include Metal-In and Metal-Out Shielding bags.

When Is ESD Shielding Packaging Used?

ESD shielding packaging is to be used particularly when transporting or storing ESD sensitive items outside an ESD Protected Area.

ESD Packaging Standards For Outside An EPA

Per Packaging Standard ANSI/ESD S541 clause 6.2 Outside an EPA “Transportation of sensitive products outside of an EPA shall require packaging that provides:

Low charge generation.
Dissipative or conductive materials for intimate contact.
A structure that provides electrostatic discharge shielding.“

Additional ESD Definitions

Other helpful ESD related definitions from the ESD Association Glossary ESD ADV1.0 include:

Faraday Cage: “A conductive enclosure that attenuates a stationary electrostatic field.”
Electrostatic discharge (ESD) shield: “A barrier or enclosure that limits the passage of current and attenuates an electromagnetic field resulting from an electrostatic discharge.”
Electrostatic shield: “A barrier or enclosure that limits the penetration of an electrostatic field.”

So, hopefully we’ve clarified a few things today when it comes to the “shielding” property by explaining the phenomenon of the “Faraday Cage”. Don’t forget to implement our tips when it comes to using your ESD bags!

Human Body Model vs. Charged Device Model

Image scsstaticcontrol August 24, 2017 0

As reviewed previously, an Electrostatic Discharge is a rapid, spontaneous transfer of an electrostatic charge induced by a high electrostatic field through a spark between two bodies at different electrostatic potentials as they approach or are separated from one another.

The ESD Association characterizes three models of discharge, Human Body Model (HBM), Charged Device Model (CDM) and Machine Model (MM). Each model is intended to follow specific discharge properties such as the rise and fall times of the discharge current waveform.

Today, we will discuss HBM and CDM.

Human Body Model (HBM) simulates a person becoming charged and discharging from a bare finger to ground through the circuit under test. Humans are considered a primary source of ESD and HBM can be used to describe an ESD event due to the combination of the capacitance of a human body and resistance of skin touching a sensitive component. Typically, you need to pay better attention to personnel grounding to eliminate HBM.

Per ESD Handbook ESD TR20.20-2016 section 3.4.1 Human Body Model (HBM)

HBM has been in use for over 100 years. It was first defined to allow measurement and evaluation of explosion hazards for underground mining operations. There are a few different test standards describing the HBM for military and commercial applications, but the differences are in the application of the test, calibration of the system, and other ancillary items. The waveform, as defined by the human body resistance and capacitance, is virtually identical among all the test standards. The most widely used standard is ANSI/ESDA/JEDEC JS-001. The HBM test standard uses a stressing circuit which charges a 100 pF capacitor to a known voltage and discharges through a 1500-ohm resistor as shown in Figure 3. The simulators are verified by measuring various features of the current waveform, some of which are shown in Figure 4. Full details for tester qualification and waveform verification are described in ANSI/ESDA/JEDEC JS-001.

Charged Device Model (CDM) simulates an integrated circuit becoming charged and discharging to a grounded metal surface. CDM can be used to describe an ESD event due to an integrated circuit that is suspended on a vacuum pick and then placed on a metal surface during assembly.

Manual operation and handling is much less likely these days as operations have become more automated. CDM is the most pragmatic discharge model in automated production today. Anytime a sensitive device is lifted from a tray and transported it is most likely generating a charge.

Per ESD Handbook ESD TR20.20-2016 section 3.4.2 Charged Device Model (CDM)

In principle, there are two variations of CDM. The first considers the situation of a device that is charged (through tribocharging) on its package, lead frame, or other conductive paths followed by a rapid discharge to ground through one pin or connector. The second considers the situation of a device which is placed in an electric field due to the presence of a charged object near the device. The device’s electrostatic potential is increased by this field. This process is sometimes referred to as static induction. The device will discharge if it is grounded while still in the electric field. In both cases, the device will discharge, the failure mode will be the same, and the failure type and location will be the same. The most widely used CDM standards use the static induction approach. In CDM simulators, the device is grounded by a pogo pin contacting one pin or lead of the device. The current through the pogo pin can be measured and recorded which is particularly important as the discharge current determines the ESD threshold, a schematic of this is shown in Figure 5.

Experimental results show that the CDM discharge current is very fast, with rise-times measured often below 100 ps with a “pulse width” (full width half-maximum [FWHM]) of less than 500 ps to1 ns, an example waveform with the key parameters is shown in Figure 6. By comparison, the HBM discharge has a typical rise-time of 2 to 10 ns and durations of hundreds of ns. Until 2014, the most commonly used CDM standards were JEDEC JESD22-C101 or ANSI/ESD STM5.3.1. These have now been superseded by ANSI/ESDA/JEDEC JS-002.

So, why does it matter?
Different types of discharge can affect devices in different ways. HBM is a somewhat slow discharge and ranges from 10 to 30 nanoseconds. CDM is a very fast discharge which in turn means the energy has no time to dissipate. The CDM-type damage threshold is often 10 to 20 times lower than the one for an HBM-type discharge. If an HBM-type discharge causes damage at 2000V, it is not uncommon to have the same component damaged by a 100 to 150V CDM event.

Per ESD Handbook ESD TR20.20-2016 section 3.2.1 Threats in Electronic Production Lines
ESD threats in electronics manufacturing can be classified into three major categories:

Charged personnel – When one walks across a floor a static charge accumulates on the body. Simple contact of a finger to a device lead of a sensitive device or assembly which is on a different potential, e.g., grounded, allows the rapid transfer of charge to the device.
Charged (floating) conductor – If conductive elements of production equipment are not reliably connected to ground, these elements may be charged due to triboelectric charging or induction. Then these conductive elements may transfer charge to a device or assembly which is at a different potential.
Charged device/boards – During handling, devices or boards can acquire a static charge through triboelectric charging or can acquire an elevated electrostatic potential in the field of nearby charged objects. In these conditions, contact with ground or another conducting object at a different electrostatic potential will produce a very fast ESD transient.

This categorization is useful in that each category implies a set of ESD controls to be applied in the workplace. ESD threats from personnel are minimized by grounding personnel through the use of wrist straps and/or footwear/flooring systems. Discharges from conductive objects are avoided by assuring that all conductive parts that might contact devices are adequately and reliably grounded. The occurrence of ESD involving charged devices or boards is minimized by a) preventing charge generation (low-charging materials, ionization) or b) by providing low-current “soft landings” using dissipative materials.

Since these preventive measures are seldom perfectly deployed, the overall threat of ESD failure remains and the risk ultimately depends on how well the controls are maintained and the relative sensitivities of the devices being handled.

Taking Action
SCS recommends reviewing your manufacturing process and determining what model is the most relevant for your facility. Are your components handled directly by hand or by a hand tool such as tweezers or a vacuum pick?

Finding the root cause of ESD events is crucial to solving the problem. SCS technology can identify events in areas like SMT line, soldering, printer and repair stations. SCS has instrumentation to identify component sensitivity and measure ESD events as well as ensure compliance within your facility.

The SCS CTM082 ESD Pro Event Indicator has a special CDM filter switch to filter and reject EMI signals that are not caused by CDM discharges. Make sure to set requirements for static voltage and discharge strength within your production environment based on the most sensitive component in production.

The SCS CTM048-21 EM Eye ESD Event Meter will calculate the event magnitude for HBM and CDM. It also logs the events to a microSD card so they can be downloaded to a PC. Solving ESD problems requires data; a before-and-after analysis of data may now be measured and used to tailor your ESD control program.

The SCS 770063 EM Aware Monitor is ideal for automated equipment and will provide an approximate voltage for the ESD event based on HBM and CDM models. The EM Aware Monitor has Ethernet network connectivity and communicates with our Static Management Program (SMP). All activity is stored into a database for on-going quality control purposes. SMP allows you to pinpoint areas of concern and prevent ESD events. Quantifiable data allows you to see trends, become more proactive and prove the efficiency of your ESD process control system.

11 Steps to an ESD Control Program

Image scsstaticcontrol June 29, 2017 0

If you followed our tips to fight ESD, you will have already identified all ESD sensitive items in your factory. You’re now at a point where you realize that you need to implement ESD Control measures. But where do you start? There is so much information out there and it can be completely overwhelming. But don’t panic – today’s blog post will provide you with a step-by-step guide on how to set-up a suitable ESD Control Plan.

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

Training
Product Qualification
Compliance Verification
Grounding / Equipotential Bonding Systems
Personnel Grounding
ESD Protected Area (EPA) Requirements
Packaging Systems
Marking

The ESD Control Program Plan is the principal document for implementing and verifying the Program. The goal is a fully implemented and integrated Program that conforms to internal quality system requirements. The ESD Control Program Plan shall apply to all applicable facets of the Organization’s work.” [ANSI/ESD S20.20-2014 clause 7.1 ESD Control Program Plan]

“The selection of specific ESD control procedures or materials is at the discretion of the ESD Control Program Plan preparer and should be based on risk assessment and the established ESD sensitivities of parts, assemblies, and equipment.” [ANSI/ESD S20.20-2014 Annex B]

Define what you are trying to protect
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. Per ANSI/ESD S20.20-2014 section 6.1 “The Program shall document the lowest level(s) of device ESD sensitivity that can be handled.” A general rule is to treat any device or component that is received in ESD protective packaging as an ESD susceptible item.

An operator handling an ESD susceptible item
Become familiar with the industry standards for ESD control
A copy of ANSI/ESD S20.20-2014 can be obtained from the ESD Association. It covers the “Development of an Electrostatic Discharge Control Program for Protection of Electrical and Electronic Parts, Assemblies and Equipment (Excluding Electrically Initiated Explosive Devices)” and “provides administrative and technical requirements for establishing, implementing and maintaining an ESD Control Program.”Also, consider purchasing the ESDA’s ESD Handbook ESD TR20.20-2016 for guidance on the implementation of the standard.
Select a grounding or equipotential bonding system
“Grounding / Equipotential Bonding Systems shall be used to ensure that ESDS items, personnel and any other conductors that come into contact with ESDS items are at the same electrical potential.” [ANSI/ESD S20.20-2014 section 8.1 Grounding / Equipotential Bonding Systems]
The elimination of differences in electrostatic charge or potential can be achieved in three different ways:
– Equipment Grounding Conductor
– Auxiliary Ground
– Equipotential Bonding
- Equipment grounding conductor:
  the first and preferred ESD ground is the electrical system’s ground or equipment ground. In this case, the ESD control elements and grounded personnel are connected to the three-wire electrical system equipment ground;
- Grounding using auxiliary ground:
  the second acceptable ESD ground is achieved through the use of an auxiliary ground. This conductor can be a ground rod or stake that is used for grounding the ESD control elements in use at a facility. In order to eliminate differences in potential between protective earth and the auxiliary ground system it is required that the two systems be electrically bonded together with a resistance less than 25 ohms;
- Equipotential bonding:
  in the event that a ground facility is not available, ESD protection can be achieved by connecting all of the ESD control elements together at a common connection point.
Determine the grounding method for operators (Personnel Grounding)
The two options for grounding an operator are:
- a wrist strap or
- footwear / flooring system
Wrist straps must be worn if the operator is seated. We will talk about wrist straps in more detail at a later point. For now, remember to connect the coil cord part of the wrist strap to a Common Point Ground so that any charges the operator may generate can be removed to Ground.

An operator using a wrist strap as a grounding method

A footwear / flooring system is an alternative for standing or mobile workers. ESD footwear needs to be worn on both feet and only works as a grounding device if it is used in conjunction with an ESD floor. Just like with wrist straps, a future blog post will clarify the ins and outs of ESD footwear.

An operator using foot grounders on an ESD floor as a personnel grounding method

In some cases, both (wrist strap and foot grounders) will be used.
Establish and identify your ESD Protected Area (EPA)
ESD Control Plans must evolve to keep pace with costs, device sensitivities and the way devices are manufactured. Define the departments and areas to be considered part of the ESD Protected Area. Implement access control devices, signs and floor marking tape to identify and control access to the ESD Protected Area.
Select ESD control items or elements to be used in the EPA based on your manufacturing process
Elements that should be considered include: worksurfaces, flooring, seating, ionization, shelving, mobile equipment (carts) and garments.
Develop a Packaging (Materials Handling & Storage) Plan
When moving ESD susceptible devices outside an ESD protected area, it is necessary for the product to be packaged in an enclosed ESD Shielding Packaging. We will discuss ESD Packaging in more detail in a future blog post. All packaging, if used, should be defined for all steps of product manufacture whether inside or outside the EPA.

An operator packing an ESD sensitive item into a Shielding Bag
Use proper markings for ESD susceptible items, system or packaging
From ANSI/ESD S20.20-2014 section 8.5: “ESDS items, system or packaging marking shall be in accordance with customer contracts, purchase orders, drawing or other documentation. When the contract, purchase order, drawing or other documentation does not define ESDS items, system or packaging marking, the Organization, in developing the ESD Control Program Plan, shall consider the need for marking. If it is determined that marking is required, it shall be documented as part of the ESD Control Program Plan.”
Implement a Compliance Verification Plan
From ANSI/ESD S20.20-2014 section 7.4: “A Compliance Verification Plan shall be established to ensure the Organization’s fulfillment of the technical requirements of the ESD Control Program Plan.”. Our next post will explain in detail how to create and implement a Compliance Verification Plan so stay tuned…
However, developing and implementing an ESD Control Program is only the first step. The second step is to continually review, verify, analyse, evaluate and improve your ESD program:“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 occur. The Compliance Verification Plan shall document the test methods and equipment used for making the measurements. If the test methods used by the Organization differ from any of the standards referenced in this document, then there must be a tailoring statement that is documented as part of the ESD Control Program Plan. 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.” [ANSI/ESD S20.20-2014 section 7.4 Compliance Verification Plan]
Regular program compliance verification and auditing is a key part of a successful ESD Control Program.
Develop a Training Plan
From ANSI/ESD S20.20-2014 section 7.2: “Initial and recurrent ESD awareness and prevention training shall be provided to all personnel who handle or otherwise come into contact with any ESDS items.”
Make the ESD Control Plan part of your internal quality system requirements
A written ESD Control Plan provides the “rules and regulations”, the technical requirements for your ESD Control Program. This should be a controlled document, approved by upper management initially and over time when revisions are made. The written plan should include following:
- Qualified Products List (QPL): a list of ESD control items permitted to be used in the ESD Control Program.
- Compliance Verification Plan: includes periodic checking of ESD control items and calibration of test equipment per manufacturer and industry recommendations.
- Training Plan: an ESD Program is only as good as the use of the products by personnel. When personnel understand the concepts of ESD control, the importance to the company of the ESD Control Program, and the proper use of ESD products, they will implement a better ESD Control Program improving quality, productivity and reliability.

3 Steps to Fight ESD

Image scsstaticcontrol June 2, 2017 3

Happy Friday to everyone! Are you ready for another round of ESD updates? We’ve got a real gem for you today so let’s jump right in.
We’ve so far learned what ESD is and why ESD Protected Areas are so important. In today’s post, we want to arm you with 3 simple tactics to protect your ESD sensitive items. It’s easier than you think!

ESD Protection is a Requirement!
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. Industry experts estimate that average electronics product losses due to static discharge range from 8 to 33%. Others estimate the actual cost of ESD damage to the electronics industry as running into the billions of dollars annually. It is therefore critical to be aware of the most sensitive items being handled in your factory as the need for proper ESD protection increases every day.
Per ESD Handbook ESD TR20.20-2008 section 2.2: “Electronic items continued to become smaller, faster and their susceptibility to static damage increased…all electronic devices required some form of electrostatic control to assure continued operation and product reliability.”

Below you will find 3 simple tips to get ahead of the game.

1. Establish your ESD Protected Area
As a reminder, an ESD Protected Area (EPA) is a defined space within which all surfaces, objects, people and ESD Sensitive Devices (ESDs) are kept at the same potential. That means:

All surfaces, products and people are linked to ground.
Moveable items, such as containers and tools, are bonded by standing on a grounded surface or being held by a grounded operator.
Everything that does not readily dissipate a charge must be excluded from the EPA.

In our last post we talked in detail about how to set-up an ESD Protected Area so if you’re unsure where to start, catch-up with the post here.

Remember that it’s just as important to mark your ESD Protected Area as it is to have it set-up correctly in the first place. If your EPA is not clearly identified, operators will not realize that special pre-cautions are required when entering. You really don’t want an unprotected person wandering over and touching things on the ESD workbench. All your hard work, time and money could be wasted. Make sure you use signs and tape to distinguish your EPA from the rest of your workshop.

Employee working at an ESD Protected Workstation — *An employee working at an ESD Protected Workstation*

Some take-away points for you:

The ESD Protected Area (EPA) should have signage to clearly identify where it is.
All conductors including personnel must be grounded. Operators must either wear wrist straps or footwear in combination with an ESD floor. ESD working surfaces (e.g. mats) are to be grounded.
Wristbands are to be worn snug; the grounding tab of foot grounders must be placed under the foot in the shoe; ESD smocks need to cover all clothing on the torso.
Wrist straps and footwear are to be tested daily. For wrist straps a continuous monitor can be used instead.
Remove all non-essential insulators or neutralize essential insulators with ionizers.
Use packaging with shielding properties to store or transport ESDS outside the EPA.
Only handle unpackaged ESDs in an EPA when grounded.
Periodic checks of installed products (e.g. ESD working surfaces, ESD flooring etc.) are required.
Only trained or escorted people are to be allowed in the EPA.

2. Determine your ESD sensitive items
It is critical to be aware of the most sensitive item being handled in your factory. 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 program to safeguard your most sensitive component.

Per ESD Handbook ESD TR20.20-2008 section 4.1.1 Determining Part ESD Sensitivity “The first step in developing an ESD Control Program plan is to determine the part, assembly or equipment sensitivity level under which the plan is to be developed. The organization can use one of several methods to determine the ESD sensitivity of the products that are to be handled. Some of the various methods are: 1) Assumption that all ESD products have a HBM sensitivity of 100 volts; 2) Actual testing of products using accepted test methods.”
Any ESD sensitive item should be identified with the ESD sensitivity symbol, either on itself or its container. The ESD Sensitivity Symbol (also called Susceptibility or Warning Symbol) identifies items that can be damaged by ESD and should ONLY be unpackaged and handled while grounded at an ESD protected workstation.

3. Train, train train!
No, we’re not talking about railway cars here. What we are referring to is teaching your employees. “Initial and recurrent ESD awareness and prevention training shall be provided to all personnel who handle or otherwise come into contact with any ESDS [ESD sensitive] items. Initial training shall be provided before personnel handle ESDS items. The type and frequency of ESD training for personnel shall be defined in the Training Plan. The Training Plan shall include a requirement for maintaining employee training records and shall document where the records are stored. Training methods and the use of specific techniques are at the Organization’s discretion. The training plan shall include the methods used by the Organization to verify trainee comprehension and training adequacy.” [ANSI/ESD S20.20-2007 section 7.2]

*Training is an essential part of an ESD Control Program*

Perhaps the most important factor in a successful static control program is developing an awareness of the “unseen” problem. 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.
Educating your personnel is therefore an essential basic ingredient in any effective static control program. 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.