When talking about ESD Classifications a little while ago, we identified a “class 0” item as withstanding discharges of less than 250 volts.

The introduction of ANSI/ESD S20.20 states: “This standard covers the requirements necessary to design, establish, implement and maintain an Electrostatic Discharge (ESD) Control Program for activities that manufacture, process, assemble, install, package, label, service, test, inspect or otherwise handle electrical or electronic parts, assemblies and equipment susceptible to damage by electrostatic discharges greater than or equal to 100 volts Human Body Model (HBM) and 200 volts Charged Device Model (CDM).”

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

Introduction

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

What is a “Class 0” device?

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

*Ultra-sensitive devices are extremely common*

Before Updating Your ESD Program

“Class 0” refers to a wide range of items and there are a few things you should remember before making any changes to your existing ESD program:

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

Tips for handling “Class 0” Items

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

One thing to note: The best approach to stay ahead of the game is taking proactive actions. It is critical to figure out how to protect your components from ESD damage before you receive them. If actions are taken after components are received, the components are susceptible to receiving ESD damage.

1. Improve Grounding

Inside an EPA, all conductors (including people) are grounded. Now you’re probably thinking: “But I’ve already grounded my operators and worksurfaces. What else is there left to do?”. Firstly, well done for properly grounding the ‘objects’ in your EPA. The next step is to adjust and improve your current program to allow for even better protection. Here are some suggestions:

Personnel:

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

*Full coverage foot grounders are recommended when handling ultra-sensitive devices*

Worksurfaces:

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

Other:

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

2. Minimize Charge Generation

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

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

Personnel: Use low-charging floor finish
Surfaces: Use low-charging topical antistatic treatments

Both types of ESD products create a low tribocharging coating which allows charges to drain off when grounded. The antistatic properties will reduce triboelectric voltage to under 200 volts.

3. Remove Insulators

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

Replace regular production supplies and fixtures with dissipative, low charging versions, e.g. ESD dissipative brushes, ESD dispensers, ESD tape, ESD Chairs etc.
Shield charges on clothing by using ESD smocks.

*Use ESD safe accessories whenever possible*

If an insulator is absolutely necessary for production and cannot be removed from the EPA, you could consider a topical treatment which will reduce triboelectric charges.

Is this not an option, then move on to tip #4.

4. Use Ionization

First, ionization is not a cure-all. We’ve learnt that ionizers neutralize charges on an insulator.

However, that does not mean that you can just have any insulator in your EPA because the ionizer will “just fix it”. No, in this instance, prevention is generally a better option than the cure. So, your priority should ALWAYS be to remove non-process essential insulators from your EPA – see tip #3. If this is not possible – then ionization becomes essential.

Ionization:

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

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

5. Increase ESD Training and Awareness

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

*ESD Training is a vital part of every successful ESD Control Program*

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

6. Create an enhanced Compliance Verification Plan

We talked in a previous post about compliance verification, what it is and how to create a plan that complies with the ESD standard. So, if you already followed our steps and have a plan in place, here are a few tips to improve your compliance verification plan:

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

Conclusion

“Class 0” items require additional measures of ESD protection due to their sensitivity to ESD damage. The best way to protect these ultra-sensitive components is to increase ESD protective redundancies and periodic verifications to all ESD Control technical elements.

To decrease the probability of ESD damage while handling ultra-sensitive items, additional precautions are required. This includes additional and/or more stringent technical requirements for ESD control products, increasing redundancies, and more frequent periodic verifications or audits.

Additionally, ESD control process systems should be evaluated as to their performance as a system. It is important to understand how the technical elements in use perform relative to the sensitivity of the devices being handled. Thus, tailoring the process to handle the more sensitive parts. For example: If the footwear/flooring allows a person’s body voltage to reach 80 volts and a 50 withstand voltage item gets introduced into the process, you must either allow only handling via wrist straps or would have to find a way to modify the footwear/flooring performance to get peak voltages below the 50 volt threshold.

Remember: The ESD Standard gives recommendations that will always be behind current/future developments. As soon as a Standard is published, technology will have progressed. In order to protect your devices and company reputation for reliable devices – it is recommended your company take responsibility to implement methods/procedures that exceed the recommendations of the ESD Standard to fit your sensitive component requirements.

References:

Dave Long: Seven Mandatory Considerations Before Handling Class 0 ESDS Devices
Stephen Halperin, David E Swenson, Craig Zander: The Truth About ESD Class 0
Ron Gibson: What is ESD Class Zero?
-Ing. Hartmut Berndt: Requirements on a Class “0” EPA – Basics, Standards, ESD Equipments and Measurements

People pose the biggest threat to ESD sensitive components. However, when properly trained, operators can become the key weapon in the fight against ESD. Every person coming into contact with ESD sensitive items should be able to prevent ESD related problems before they occur or provide immediate action when they do occur. Today’s blog post will explain in detail the role operators play in ESD Protection and how your company can support them in the fight against ESD.

Introduction
As an employee, the invisible threat of ESD should be of great concern to you. ESD damage can significantly reduce your company’s profitability. This may affect your company’s ability to compete in the marketplace, your profit sharing and even your employment. Everyone likes to take pride in their work, but without proper ESD controls, your best efforts may be destroyed by ElectroStatic discharges that you can neither feel nor see.

motherboard doctors — People are often a major factor in the generation of static charges

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 by just walking across the floor. 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 by 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 ESD 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. No technician needs an unprotected person wandering over and touching things on the service bench.

The invisible enemy
The biggest issue with ElectroStatic discharges is that you can neither see nor feel the threat. Daily life has other examples of hidden enemies where careful procedures must be followed to regularly obtain positive results. One example is sterilization which combats germs and contamination in hospitals.
Damage caused by invisible and undetectable events can be understood by comparing ESD damage to medical contamination of the human body by viruses or bacteria. Although invisible, they can cause severe damage. In hospitals, the defense against this invisible threat is extensive contamination control procedures including sterilization.

A medical team performing an operation — Would you consider having surgery in a contaminated operating room?

We are aware of the benefits of sterilization in medicine. We must develop the same attitude towards ESD control and “sterilize” against its contamination. Just as you would never consider having surgery in a contaminated operating room, you should never handle, assemble or repair electronic assemblies without taking adequate measures against ESD. For the hospital to sterilize most of the instruments is not acceptable; actually, it may waste money. Every single instrument needs to be sterilized. Likewise, it is not acceptable to protect the ESD sensitive items most of the time. Effective ESD control must occur at each and every step where ESDS items are manufactured, processed, assembled, installed, packaged, labelled, serviced, tested, inspected, transported or otherwise handled.
Everyone handling sensitive components should:

“recognize ESD threat
know what equipment to use, and how to use it
know the correct ESD procedures, and work to them
know how to check equipment
know which packaging to use
take corrective actions when required.” [Source]

It is obvious that ESD training of personnel is a prerequisite for a functioning ESD control program.

Training
ESD training needs to be provided to everyone who handles ESD sensitive devices – that includes managers, supervisors, subcontractors, cleaners and even temporary personnel. Training must be given at the beginning of employment (BEFORE getting anywhere near an ESDS) and in regular intervals thereafter.
“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]

ESD training should include:

an introduction to ESD – what it is, what it’s caused by and how to control it
how to handle sensitive devices and what precautions to take when coming into contact with them
how to identify and mark ESD sensitive items
an overview of the ESD Standard.

For operators working in assembly, repair or field service, job specific training will be required, too.
If visitors are entering an EPA, they must possess basic ESD awareness and understand how to use their wrist straps and footwear.

Operator’s safety comes first
One final word of warning: while ESD control is important, it is of secondary importance to employee safety. ElectroStatic charges or static electricity can be everywhere; however, conductors can be effectively grounded and charges removed to ground. A fundamental rule in ESD control is to ground all conductors, including people. BUT: Personnel should not be grounded in situations where they could come into contact with voltage over 250 volts AC.

ESD Training

6 Tips for handling “Class 0” Items