Letter 24023

"Wetting" problems when tin/gold soldering to plated carriers  

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Small kovar carriers plated with nickel then gold sometimes have difficulty in flowing tin/gold solder. These same carriers exhibit a purple color if heated to 350C. Any ideas?
We subcontract our plating to MIL Spec platers but haven't been able to figure out what process guarantees that the solder will wet correctly.

Ed McAvoy
electronics - Camarillo, California