"plating selection for electrical contact spring"
Question:
"I have a zinc plated spring that is being used as an battery contact. The solderability of the zinc plating is very poor requiring flux and a tinning process in order to solder the spring to a pc board. I'm looking for alternatives to the flux and tinning operation. Is stripping the zinc plate and tin lead plating the spring a viable option? I'm concerned about the durability of a tin lead plating since the electrical connection relies solely on the mechanical contact between the spring and a nickel plated contact plate."
Answer:
The lack of solderability of the zinc-plated spring is probably to due poor wetability of the zinc. Regarding the alternative to strip the zinc and recoat with tin-lead, you do not provide sufficient information regarding your "durability" concerns to properly answer. I am assuming that the spring base metal is a high tensile strength carbon or low alloy steel. If so, stripping should be done with caution not to introduce hydrogen into the metal, which could promote hydrogen embrittlement.