Static damage was Re: OT Troubleshooting

The reliance on ESD protection diodes is way over-sold. From EDN Dec,2004; "On a schematic, ESD-protection diodes resemble the diodes engineers sometimes use to limit overshoot and undershoot on a high-speed bus, but with one significant difference: the expected lifetime of the diode. An overshoot-limiting diode is huge compared with its ESD-protection cousin, and, because of its large size, the overshoot-limiting diode can absorb pulse after pulse of high-powered current transients, lasting essentially forever. ESD-protection diodes, on the other hand, are small, have limited strength, and aim to handle only a few events in their lifetime. " At Hughes we conducted (no pun intended) failure analysis on any electronic parts we thought may have been compromised (not just CMOS). The parts were de-capitated and scanned (as stated in the other thread). Equipment shot into space cannot tolerate latent defects, as in those days we didn't have a shuttle that could bring back the close orbit satellites. With the high density sub-mil geometry's in IC's now ESD is a huge problem. A lot of dies have "spark gaps" incorporated into the etch. Below is some typical and high end readings for ESD voltages (source: Fairchild ESD Application Note: AN-248). Person on carpet: 12,000 V (highest reading 39,000 V) Person on Vinyl : 4,000 V (highest reading 13,000 V) Person on workbench: 500 V (highest reading 3,000 V) 16 Pin DIPs in plastic box 3,500 V (highest reading 12,000 V) I think you get the idea. The diodes are normally tested at 400 Volts. After multiple ESD hits the diodes fail open and go to their maker. Best regards, Steven C.