ESD Systems - Questions And Answers

I have a problem I hope you can help me with. I work for a Company that manufactures flow measurement equipment. One of our products, a 4-20mA loop powered transmitter board, utilizes the Burr-BrownXTR101 transmitter chip. This chip is an ESD susceptible device. Recently, the company we contracted to manufacture our circuit boards for us, sent a shipment of circuit boards which were compromised due to improper packing procedures. The ESD protective bags were not closed and the circuit boards were falling out into the unsafe environment of the shipping carton. I rejected these boards and returned them to the manufacturer. The manufacturer re-packaged these same boards, (this time observing proper ESD packaging procedures), and shipped them back to us. They then told our purchasing department they had "TESTED" the boards and "ALL" were good! Now, I understand that "ALL" the boards may, in fact, though unlikely, work flawlessly. However, in the 12+ years I have worked in the field of electronics, I have never heard of a test that can predict a latent failure, other than tearing the chip carrier apart and visually inspecting it under a microscope! Have I missed something? Has someone discovered some new technology that can be used to test suspect ESD sensitive devices that I'm not aware of? - Anonymous

You are correct. I know of no new or old technology available to easily and non-destructively detect any level of a latent ESD or EOS failure before it becomes catastrophic. Until a ‘tricorder-type’ device is invented, I suspect this will be true for many years to follow. (One exception may be some deviation of an X-Ray machine, but then you have to be familiar with the architecture of the device you are viewing among other safety considerations.) Another thought: There are chip testers [such as those made by Teradyne] that put a specific chip through several tests. If each chip were analyzed this way with specific current and voltage signals recorded right after being manufactured and then compared to the same data after a discrepancy is suspected, you might see a slight deviation signaling a possible problem in one or more of the signals (assuming the tests were done under identical conditions).

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