Patrick McGowan – Page 2 – Ground Zero Electrostatics Blog

26 Feb

Can ESD Wax be applied to bring back dissipative properties?

Q: Into our manufacturing area we have a dissipative floor installed, some areas has lost the dissipative properties, we are using ESD wax to correct those areas.

We are not having good results, we measure point to point and point to ground and these areas still measure insulative, my question is:
The ESD wax only works in floors with dissipative properties, or could it be applied on areas where the floor has lost the dissipation properties?”

A: Thanks for contacting us. This is one of those questions that I like to pounce on, because it brings up many current misconceptions in the ESD flooring industry. I’m going to answer your question about using chemicals to perhaps patch up certain areas in your flooring system, but I’m going to reach beyond that question and give a comparison of the ESD flooring system vs an otherwise non-ESD flooring system with an ESD sealer applied to it. We supply both options here, by the way. I hope you find what you need here and that this response helps guide you in your application.
Read More →

04 Feb

How to measure ohms of ESD Chair back rest

Q: Hi, I am a fresh ESD engineer. I need to perform a testing on ESD chair by using 5 pound Megohmmeter. I encountered a problem when I was trying to test on the backrest and rear of backrest. The backrest is a vertical plate, how to put a 5 pound electrode perpendicular to that surface? Even ANSI/ESD STM 12.1 2006 also not mentioned clearly about the testing on the backrest. Can I hold the 5 pound electrode by my hands so that it is contact with surface of the backrest? Or is there any other proper way?”

A: Hello, I understand your frustration with some of these tests.

It sounds like you’ve got all the proper testing equipment and you’re following the best procedures for this. The main concern is to see that the seat, seat back and arms are making good contact to the personnel, that personnel is wearing the proper clothing so as to enable the combination of personnel to chair to esd flooring system to electrical ground are enabling the tribocharge to recombine to earth. If you have an ESD chair that includes a static conductive/dissipative seat, back, arms, casters, etc. we can make these resistance measurements to the chair’s groundable point, to a plate sitting underneath a caster, and ultimately, all the way across the floor to earth ground.
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26 Jan

What is the importance of using ESD Footwear on ESD Floor?

Q. What is the importance of having the personnel within an EPA to wear ESD footwear on an ESD Flooring system?

A. Thanks for the inquiry. It was good speaking with you earlier. You had stated that you had concerns about the grounding of your flooring system and my first question to you was about the use of ESD footwear. I believe that you had stated that not everyone was using esd footwear.

You pose a situation here that needs to be addressed as a top priority at all levels of ESD Awareness for every client that we come into contact with. I don’t mean to over-simplify this but I am seeing a common trend in the ESD industry; your ESD system is only as strong as the weakest link in the chain. Another way to say this is; If you buy a Plasma TV, it needs to come with a power cord and you need to plug that in. Read More →

19 Dec

Frequency of testing ESD Technical Elements in an EPA

Q: We have a number of carts, racks, and chairs in the clean room. When we do our weekly, monthly and semi-annual checks for ESD and grounding, do we do a statistical sample or do we check all of each item. Is there a standard that explains this?

A: You ask a very valid question and it just so happens that I received a similar question on this not long ago.

I wish there was one and only one ESD Bible that’s all inclusive and complete; from design to audit. The ESD Association has the ANSI/ESD S20.20-2007 document which gives us guidelines in establishing an ESD control program. But as far as a standard explaining when to audit each and every ESD technical element, I have yet to find a good source. The tables contained within 20.20 will give you “required limits” for various technical elements, but not a frequency of when to audit or test these systems. Between JEDEC Standard 625-A Table 2 of page 9 and other sources, I’ve put together these recommendations, but it’s up to you to implement them and tailor them to your unique processes; Read More →

05 Dec

What is Static Electricity?

Q: What is Static Electricity?

A: Static Electricity can be defined as an electrical charge at rest. ESD is the transfer of static charges between bodies or objects at different electrical potentials. This may be caused by either direct contact or by induction of an electrostatic field. Static Charges are generated when two materials are rubbed together. This term is called Triboelectric Generation or Tribocharging

Factors that Influence Tribocharging:

Intimacy of Contact Speed of Separation
Conductivity of Materials
Triboelectric Series Position
Relative Humidity Read More →

05 Dec

The difference between an ESD Control Program and Plan

Q: I’m having a hard time understanding the difference between an ESD Control “Program” and an ESD Control Program “Plan”… Can someone explain what is required? Do I need two documents, one “Program” and one “Plan”, do I need to develop a single ESD document? I’m not sure what the difference between a program and a plan is.

A: It is my understanding that the program is ANSI/ESD S20.20-2007’s way of providing requirements to establish, implement, and maintain an ESD program.

It is my understanding that the “Plan” is the organization’s scope within that “Program” that conforms to their own internal requirements while evolving with changes to technical elements as time goes by.

05 Dec

ESD Warning Signs/Labels and which one to use

Q: What is the difference between the symbols used in ESD warning signs / labels: yellow hand w/ black background; black hand w/ yellow background; attention; triange/hand with arch; warning; etc. and how do you decide which one to use?

A: As per ANSI/ESD S8.1-1993, there are two types of ESD awareness symbols identified.

The ESD Susceptibility Symbol:

ESD Susceptibility Symbol

Consists of the Triangle, the reaching hand with slash through it.
This means ESD sensitive devices or assemblies are present.
DO NOT TOUCH or Handle Properly.
If the device sensitivity is known, it can be added to the label.

ESD Protective Symbol

ESD Protective Symbol

Consists of the Triangle, the reaching hand and an Arc around the Triangle.
This indicates ESD Protective Material such as chairs, mats, and wrist straps.

Another common ESD symbol for safety would be;

Common Point Ground

Common Point Ground
This symbol looks like a bull’s eye and may be black and yellow.
This represents connecting ESD control materials or equipment to electrical or 3rd wire ground.
You can consult the standard S6.1 from the ESD Association for more on this.

On our website we have various ESD Labels, ESD Warning Signs and ESD Control Area Signs and Posters for your EPA (ESD Protected Area). The labels can be used on bags, boxes, and totes. The Caution Label symbol is still popular and is represented by a circle with three arrows entering into it.

The Attention Labels utilize the ESD Susceptibility Symbol and are represented by four different types:

Small ESD attention labels- Destructible type or tamper-evident and is good for closing small bags containing ESDS components
MIL 129 Label – Also destructible type or tamper-evident label
ESD Attention Label – a label that also allows writing space
Dry Packaging & ESD Susceptible Label

ESD Control Area Signs and Posters.

ESD Control Area Poster

Black on Yellow or Yellow on Black print is just used for ease of reading and the MIL 129 label is the only one that I know that uses a black hand in a yellow triangle instead of a yellow hand in a black triangle.

05 Dec

The difference between Low Static and Static Dissipative

Q: What is the difference between Low static 3.5kv carpeting and static dissipative carpeting? When used on walls is 3.5kv carpeting ok in electronic equipment rooms?

A: When people refer to 3.5 kV carpeting I believe they are referring to the threshold voltage that people can feel as a nuisance static shock. We deal primarily with manufacture, test, assembly, and application environments where the end-user is protecting expensive electronic components, explosives, assemblies, etc. and the threshold for their needs is down to 100 volts and less.

I believe the 3.5 kV carpeting is considered to be somewhat antistatic (resists or has reduced tribocharging abilities) and is treated topically with some temporary chemical. These types of carpet do not satisfy our needs to provide long-term solutions for the commercial, industrial, and even consumer electronics industry.

I’d like to find out more about what you’re using the carpet for. Are you using it on the walls to deaden noise or create some special environment for audio design? If you need some kind of ESD protection, can you find out what your voltage threshold is- or what is the highest acceptable voltage that your environment can tolerate?

We offer ESD carpet in broadloom form and in tile form in both static conductive (typically around 2.5e04 or 25,000 ohms to 1e06 or 1 Meg Ohm) and static dissipative (1E06 – 1E09 ohm). As the resistance increases, the generated charge dissipates less rapidly to the point that a charge potential exists somewhere in the system and an ESD event occurs. This ESD event may occur without the end user knowing, but it may damage or destroy sensitive devices. Having a textile with a resistance in the static conductive range will discharge this charge potential more rapidly and work to prevent a charge from getting too high in the first place. Different textiles tribocharge at different rates and increase to different potentials, depending which textiles are making contact with and separating from them. Many carpets perform fairly well compared to other textiles in a humid environment. The humid environment may knock the created voltage down from 10’s of thousands of volts to thousands or hundreds of volts, but not low enough to prevent ESD Sensitive Devices from getting damaged or destroyed.

I hope I’ve touched on some of your questions but need to know more about your current application to help you better.

05 Dec

ESD Compliance: Test the ESD Devices, and test the testers

Q: How does a wrist bandcum footwear ground tester differ from the work station monitor? Can we not use only the work station monitor when it can monitor the worthiness of wrist strap even? And, Can we not check the worthiness of a wrist strap with a normal multimeter

A: I think that I understand your question here. One way or another, a company needs to say what they are going to do in terms of ESD compliance. They need to then do what they say they will do and document it. They need to test the ESD devices. They then need to test the testers. And they need to show records of such in a pass/fail document and to prove that they are committed to quality and do not accept anything into the environment than will lead to a failure.

A wrist strap/footwear tester is proven and tested. It is convenient to monitor and record the compliance to a whole shift of people in a given EPA. But what if someone tests their wrist strap that morning and it fails at 10:25 that morning. They won’t know it failed until later that day.

The advantage of the constant monitor is that it not only alarms the moment it fails but it also forces the user to keep it on (wrist strap) while seated at the ESD workstation. That’s fine. But you need to test the testers periodically. And to document those tests. I hope I understood your question and answered it accordingly.

I suppose you could check the worthiness of a wrist strap with a normal multimeter. I have a device that measures the connection from a connected 4mm, 7mm, or 10mm snap, through the coil cord and 1M Ω resistor, and two conductive cylinders that measure a stretched out wrist strap. With it, I can measure the cuff only, the cuff and cord, or the cord only. It cost me (us) a small fortune. I have a Fluke 123 Industrial Scopemeter and a Fluke 77. They are great meters, up to about 40M Ω or 4.0E7. If you have wrist straps that are conductive enough, then great. Good luck. You may need a Megohmmer.

05 Dec

ESDA Specifications

Q: May I know the standard test procedures and parameters (ie: surface resistivity/surface to or person to ground resistance, decay time or any other parameter if applicable) and recommended values for confirming the worthiness of the following ESD items?

ALL ESD PACKAGING ITEM
ESD FLOOR AND WORK SURFACES
ESD CLOTHINGS
ESD FOOT WEARS
ESD HANDLING ITEM viz., BRUSHES / BINS / PCB RACKS

A: Please consult your copy of ANSI/ESD S20.20-1999 from the ESDA at http://www.esda.org/. It has specific documents for different technical elements. For example, S1.1 for wrist straps, 2.1 for garments, 3.2 for ionization, 4.1 for worksurfaces-resistive characterization, 4.2 for worksurfaces- charge dissipation, 5.1 for Human Body Model, 5.2 for Machine Model, 5.3 for Charged Device Model, 6.1 for grounding, 7.1 for resistive characterization of materials-flooring materials, 8.1 for symbols-ESD awareness, 9.1 for footwear-resistive characterization, 10.1 automated handling, s11.11 surface resistance of static dissipative planar materials, 11.12 for EDS items-volume resistance of…, 11.2 for Triboelectric charge accumulation testing, 11.31 for bags, 12.1 for seating, 13.1 for electrical potential from soldering/desoldering hand tools, STM 97.1 for floor materials and footwear-resistance measurement in combination with a person, and STM 97.2 for floor materials and footwear-voltage measurement on a person just to name a few.

I could spend a lot of time digging up actual values for these specific items that we provide, but I haven’t put anything like that together all in one place. I will work on that and perhaps we can post that info all in one place. But keep in mind. We do not determine the parameters, we merely work to comply with them.