How Much Protection Is Enough? Print E-mail
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Written by The ESD Association   
Tuesday, 29 January 2013 19:23

Five questions to ask concerning ESD protection.

One of the most frequently asked questions in static control is straightforward and basic: “How much protection is enough?”The question is usually triggered by the need to make certain choices: “If I have wrist straps, do I need ESD flooring? Do I really need ionization? What about garments and footwear?” The protection issue is further impacted by financial considerations. The question may seem rather simple, but the answer is not.

Actually, there are two answers – answers that most ESD managers don’t want to hear: “Enough to do the job,” and “It depends.” The issue is not a simple black-and-white situation, as much as we might like it to be.

The ESD Association’s ESD control program standard, ANSI/ESD S20.20, goes a long way toward providing program requirements for protecting devices and assemblies that are sensitive to 100V human body model (HBM) discharges. But, the document recognizes that ESD control programs require tailoring for specific needs and applications. Therefore, the standard provides a number of options.

To discover how much protection is enough, it is always necessary to evaluate your manufacturing environment to understand possible static control problems. For example, it is important to ask a few simple but key questions:

1. What is the ESD sensitivity of the devices and assemblies that are handled? Products that are sensitive to 100V HBM discharges require different protection than those that are sensitive to 4,000V HBM discharges. S20.20 principles will allow management of >100V HBM susceptible parts.  For processes where more sensitive (<100V HBM) items are handled, suggestions are offered in the ESD TR20.20 Handbook.

2. What is the value of the final product, and what are the company’s annual losses to ESD? The degree of protection is directly influenced by product cost and product losses. Returned product or product complaints can be expensive and cause loss of business, so it is important to put the costs of returns and complaints into perspective as related to your business objectives. Proper static control measures almost always have payback measured in terms of days or weeks rather than months or years. Your operation may benefit in major ways and get very fast payback from implementing necessary static control measures.

3. What is the risk of inadequate protection? Find out whether your quality and inspection system is adequate to prevent damaged parts from being shipped. Is it less expensive to prevent damage or to discard damaged parts? You could be risking current and future business if you ship damaged products. Minimum procedures are always necessary for any manufacturing process where static electricity can cause problems. Elimination of minimum procedures will most certainly show that damage or problems will return.

4. Which areas and processes provide the greatest ESD exposure to our products? Discover where the potential problem areas exist in your operation – truly a key to determining how much protection is enough.

If your manufacturing process is primarily automated assembly, and you are not experiencing significant problems in the manufacturing area, protective flooring in this area may not be warranted. If, however, you are experiencing significant problems in your rework area, then concentrate your efforts there. Problems may occur due to personnel handling products while seated at workstations; the solution is to implement wrist straps and protective worksurfaces. If you also experience damage from highly mobile personnel as they move through the area, add protective flooring and footwear to reduce body voltage generation and the risk of ESD damage. If the source of the problem is created by electrostatic fields from insulators in the area, topical antistats or ionizers also may be needed, along with a rigorous improvement of procedures.

5. Do you need to audit and evaluate your efforts? You may find that the additional static control material or procedure did not solve your ESD problems. Or, you may find that changes in the area increased your ESD exposure. Hopefully, the corrections made will greatly improve the situation, but periodic auditing or evaluation of your processes is the best way to monitor the results. For certification to industry standards such as ANSI/ESDA S20.20 or the IEC equivalent in 61340-5-1, it is necessary to show continued compliance verification. This means that the ESD control processes in your facility must be regularly reviewed to ensure that every aspect of the control program is working as intended.

How much protection is enough? The answer lies in knowing and understanding your processes and facility in order to develop and implement a program that meets your specific needs.

This column is written by The ESD Association (esda.org); This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

Last Updated on Wednesday, 30 January 2013 17:26
 

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