We are experiencing solder joint failures in a shipboard wire wrap
backplane.  The failed solder joints consist of a gold plated beryllium
copper pin soldered to a solid copper buss bar.  The pin is 0.025"
square.  The buss bar is about 0.062" thick with 0.0469" (round) holes.
The buss bar provides power (5V). All other connections are wire wrap.
The buss bar is bolted to the (aluminum) backplane.  After 6-8 years of
service, electrical opens occur due to solder cracks along the pins.  The
solder joints were formed by induction soldering (we're assuming 63/37
solder). All surfaces have good wetting, but there are some voids.

We are trying to determine if we can meet a 20 year life requirement by
changing design or processes.  What are likely failure mechanisms?
What testing can be done to evaluate life expectancy of similar product?
Is Appendix A of IPC-D-279 applicable?

Thanks,
Ted Jones

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