09 Apr

Where to place the strap on a heel or sole grounder

Q: Do the heel strap cords need to be placed inside the sock i.e. between skin and sock or can the cord be outside the sock i.e. between sock and shoe? Is this specified in any ESD documentation? If so, which standard?

A: I like this question because I used to always put the strap between my foot (skin) and the sock, aka stuff it into my sock and under my heel.  I later came to find that this wasn’t necessary.

I don’t believe it’s mentioned in any ESDA standards, perhaps in ESD SP9.2-2003 Footwear-Foot Grounders Resistive.  But Foot Grounders are checked on a combo tester hopefully before you enter the EPA and if you pass and get a green light, you’re good to go.  I’m seeing instructions to say the strap is to go “inside the shoe or sock”, so…

MIL-HDBK-263B Section 40.1.1 Personnel ground strap  on page 100 says, “Personnel handling ESDS items should wear a skin-contact wrist, leg or ankle ground strap.”  So this would imply skin contact, but I found it’s not necessary.  If personnel wears cotton socks, the sweat and salt in our body make ESD shoes work, so thusly, the strap can go outside the sock and on the shoe’s conductive insole.  Be sure to lay the strap across the heel and not just across the arch if you do it this way.

So just put the strap between your sock and shoe insole and use your combo tester or test yourself from palm to earth ground and see that you’re reading less than 3.5E7 Ω per ANSI/ESD STM97.1-2006 Floor Materials and Footwear.  If you feel more comfortable putting it between the sock and skin, that’s fine too.

I find it to be more comfortable, convenient, and hygenetically sound to place it between the sock and insole as well.  If there’s any mention of this to this detail elsewhere, it’s unbeknownst to me.

17 Mar

Should ESD shoes, heel grounders be worn outside?

Q: Is it ok to wear ESD shoes or heel, toe, or sole grounders outside?

A: No.  MIL-HDBK-263B Appendix 1 page 101 40.1.2 states, “Conductive shoes, shoe covers, or heel grounders should be used to discharge personnel on conductive floors. These items should only be worn in the ESD protected areas and should be kept clean so that contaminants do not inhibit their conductive interface with the floor.”

So, to protect your investment, for good house keeping and maintenance, longevity of the ESD personal equipment, just don them before going into the EPA and take them off when you leave.

Do this and keep them clean (vacuum inside of shoes weekly and maybe clean outsoles and grounders with soapy water once a week) and you’ll get more wear out of them and they’ll be more effective.

03 Mar

Paperwork in the Electrostatic Discharge Protected Area (EPA)

Q: In our organization, there is a lot of paperwork that accompanies the product. Is this harmful to the product due to static generation? I have measured all the documents surface resistivity and find it to be dissipative in nature. Our production environment humidity is controlled from 40%-60%. I also tried to tribocharge the paper but there is no static voltage generated. The funny thing is when I rub my plastic comb and put it near bits of small paper, the bits get attracted to the comb. So is paper really harmful to the semiconductor products that we manufacture for our customer?

ESD Dissipative / Cleanroom Paper

ESD Dissipative / Cleanroom Paper

A: Hello.  It’s good for you to observe the possible generators of static in an EPA (Electrostatic Discharge Protected Area) and to remove all non-essential insulators and to ground conductors or soft ground them, as the case may be, and to use neutralization on isolated conductors and essential insulators (ionization).  You may notice low static charge potential or voltage on that paper, but what happens when it tribocharges with other materials in the EPA? Read More →

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.
Read More →

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

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

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

    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:

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

ESD Control Area Signs and Posters.

ESD Control Area Poster

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.