Building power electronics can be tricky business.If the product was designed correctly (thermal management, load margins, etc) we find premature field failures are due to ESD damage.An electrostatic charge will build up in the body. If not drained off properly, the human body will discard thousands of volts into a semiconductor device. A ‘snap’ is about 5,000 volts.Under a microscope the pn junction looks like it has bomb craters in it.This weakens the device because a good chuck of the junction is blown away.Less material is in place to handle current flow.Certain materials will hold a charge like Kraft (brown) boxes and polyester clothing.Special conductive tote boxes must be used to protect pc boards when they go from one department to another.The entire plant must be protected and grounded properly. Benches, assembly equipment, etc.Our floor has a special dissipative coating that must be stripped and reapplied every year.Some places use expensive tile from 3M that does the same job.The operators where special heel straps that discard any charge the body creates when moving.Once the circuit board is encased, MOV’s or other surge absorber devices are used protect the inputs.Not saying that is the problem here but I recommend BCB ask any electronic supplier for a ESD plan.
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