I hate to sound like a broken record but the industry has been placing lead free through-hole parts forever. Now all of a sudden its a problem???
Gold finish, silver, silver paladium, alloy 42, even pure copper. Reliability will be a function of the components you select, its metals composition IN ADDITION to the solder alloy.
Example: I had two identical 20 pin through hole connectors. One was white plastic one black. Every other feature was identical (so I thought). Fillet cracking was observed on the white component. It was never observed on the black component. This product was transitioned from tin/lead to lead free and both part numbers had MILLIONS of placements with no record of fillet cracking (during manufacturing).
Used in tin/lead = no problems. Used in lead free = fillet cracking.
Turns out the problem connector was using a different pin alloy than its cousin. cte mismatch was the root cause.
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