Basics

The immunity to ESD of present-day electronic components and devices has further decreased due to the high sensitivity of ICs.

Electronic devices can be exposed to electrostatic discharge (ESD). The discharge process generates rapid electric and magnetic processes that can impair the function of the electronic devices. Devices are tested for their immunity to ESD using special ESD generators and test setups (EN 61004-2).

The equipment should have passed the emissions scan. It should not be susceptible to this noise. The filter analysis said this was not a problem. The case should be an excellent shield. Why doesn’t this pass?

There are two statements I have heard about electromagnetic interference which are both related and true: EMC is the science and engineering of things that are typically not on the schematic [1], and EMI is often caused by issues of geometry [2]. The first statement speaks to the issues of parasitics, or cross coupling of energy due to magnetic induction or capacitance. The second says that the parasitics can be controlled or reduced if the proper routings and separations are maintained, and that once a degree of understanding about these coupling mechanisms is understood the control of them can be obtained.

To many people, Electrostatic Discharge (ESD) is only experienced as a shock when touching a metal doorknob after walking across a carpeted floor or after sliding across a car seat. However, static electricity and ESD has been a serious industrial problem for centuries. As early as the 1400s, European and Caribbean military forts were using static control procedures and devices trying to prevent inadvertent electrostatic discharge ignition of gunpowder stores.

Editor’s Note: Due to the overwhelming amount of positive feedback from the September 2013 issue of In Compliance (pp. 42-48), a follow-up article with additional lab testing by the author was necessary to respond to an aerospace prime.

Thank you for your informative article on “Pin Holes & Staples Lead to Diminished Performance in Metallized Static Shielding Bags.” Have you considered what happens if there is an ESD discharge to the staple in a bag?

As early as 1985, the author recalls re-occurring discussions of the effects of puncture holes from component leads and stapling of static shielding bags.

In July 2013, the ESD Experts page on LinkedIn® started a discussion by a USA computer manufacturing company that generated participation from end users, suppliers and consultants both here and abroad. In years past, some held opinions that pin holes do not greatly affect static shielding of metallized bags. There is, however, minimal published data to fall back upon regarding this subject matter.