Many years ago, I worked for a company that made portable computers.  A large service company wanted an add-on module base with more battery power to boost the operating life.  The original computer had gold plated battery contacts.  The battery pack had Ni-plated contacts.  The original battery was removed and the computer set on to the add-on base where its battery contacts mated with Ni-plated contacts in the base.  Nichel has a tendency to oxidize making it hard to solder to, so production decided to change to tin-plated contacts in the base (without testing) and it was cheaper.  It seemed to fix the production problem, but not long afterwards, the computers in the field started randomly resetting themselves.  Everyone thought they knew what the problem was.  The software folks blamed the hardware.  The hardware folks blamed the software.  The sales folks blamed the customer, and the customer was not happy.  To make an already long story, short, it was indeed a hardware problem.  For many years the combination of gold and Ni battery contact worked great.  Gold was soft but didn’t oxidize.  Ni was hard and oxidizes, but the contact pressure overcame that.  When production changed to a softer metal, tin, all that changed.  As the softer metal started to wear, little tin balls started to form.  These tin balls would oxidize and when they came between the gold and remain tin contacts, BINGO, the computer reset.  This process is called “fretting” and very hard to find since any vibration can cause the problem to temporarily go away.  Production switched back to Ni contacts on the base and the problem was solved.  I should note that the problem became industry wide during the 80’s when manufacturers replace gold plated connector with tin plated contacts to reduce cost.  Connector manufacturers finally settled of partial gold plating on all mating surfaces.

I once spent nearly a week troubleshooting what appeared to be a firmware timing problem because a system would randomly reboot. Oscilloscope traces looked good, and logs were unhelpful. Ultimately, we determined that the problem was caused by a slightly worn power connector that would lose contact as the system warmed up. Once replaced, the “software problem” was solved right away. I guess you could say that sometimes the “physical world” of electronics is just as tricky as the “logical world”.

I once spent nearly a week troubleshooting what appeared to be a firmware timing problem because a system would randomly reboot. Oscilloscope traces looked good, and logs were unhelpful. Ultimately, we determined that the problem was caused by a slightly worn power connector that would lose contact as the system warmed up. Once replaced, the “software problem” was solved right away. I guess you could say that sometimes the “physical world” of electronics is just as tricky as the “logical world”.