I have had cracked solder joints in my '86 300E, my '93 Volvo 940, and all my Volvo 240's. The common thread was that the parts were by Bosch or at least had the Bosch name on them. My son's Jaguar had Bosch electronics as well as Lucas and these had problems too.
I tend to agree with the folks who blame wave soldering on boards without the two sided holes. There may also be a problem with the composition of the solder. Also heat and mechanical stress are likely causes since the most common cracked solder joints I have found are connections which carry high current and/or which support the heavy relay coils.
The problem isn't just with Bosch and car electronics, however. I recently bought a Kenwood TS440SAT ham transceiver. This quit working after a few days and I found the problem to be a cracked solder joint. The part it was connecting was a very small transistor so the weight on the solder joint was negligible nor did the solder joint carry much current. The unit was not subject to vibration so that could not have been the cause. The transceiver was Japanese made about 15 years ago and cost around $1500 new so it should have been well made. I suspect that very small temperature changes working, over a long time, on a weak solder alloy was responsible for the crack. The crack was concentric to the transistor lead.
I don't know if the new, lead free, solders will be better or worse in regards to this cracking. I do know the new solders are harder to work with. I have bought a lifetime supply of the old lead/tin alloy solder. At my age a lifetime supply isn't all that much.
11-30-2007, 01:08 PM
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