ESD Systems - Questions And Answers

We are using a protective ESD floor wax, heel straps, table mats, and wrist straps. I just wanted to verify the proper configuration of using all these systems in conjunction with one another. Our wrist jacks are grounded to an electrical outlet (no resistor), wrist straps cords have a 1 megohm resistor, table mats have a 1 megohm resistor ground cord that is grounded to the same point as the wrist jacks. Our personnel are wearing 2 heel straps with resistors on an ESD waxed floor. Is this a common set up? I am getting the impression that this may be overkill? We are handling circuit boards and various computer components. Do I need this many resistors? Can there be a disadvantage to this type of set-up? - Anonymous, San Diego, CA,

The ESD control program that you describe is typical of companies’ dealing with Human Body Model ESDS Component Classification Class 0 or less than 250 Withstand Voltage. However, I believe that ESD dissipative floor finish, like Statproof® is a polymer, not a wax which would be insulative. Our Wrist Straps and Foot Grounders are UL listed having a 1 or 2 megohm resistor included. This is not for ESD control, but to protect the user in case of inadvertent contact with electrical line voltage up to 250 volts. Many ESD control programs are driven by meeting the company’s written ESD control plan, or meeting customer or ISO audits. Ideally, however, expenditures for ESD control would be driven by your company’s efforts to improve quality, productivity and customer satisfaction. If you are approaching zero quality defects, you should consider saving money by scaling back ESD control requirements. The primary area where money is wasted or saved involves ESD caused latent defects that wound the electronic component at one stage while passing all inspections, but then subsequently failing at a later assembly stage or even when the product is in the hands of the customer. Particularly, when the product works intermittently, these quality problems can be very annoying, mysterious, and costly.

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