Sheila Smith asked:

>Hope someone can answer this ... how long will parts plated with tin/lead
>remain solderable using regular tin/lead solder & RMA flux?   These are
>metal parts - copper, brass and aluminum.  Brass & aluminum have nickel
>underplate.  My supplier is telling me 12 months @ normal storage
>conditions but my captive shop guy is saying "no way"...who's right?

Take these precautions into consideration before deciding:

1) tin-lead plating is less protective than tin-lead fused coatings.

It has much more porosity, and the base metal can oxidize more quickly.

2) some tin-lead plating can have solderability issues almost immediately.

Depends on the amount of organics, etc. in the deposition. I have also seen
cases where coatings of tin-lead (out of a fluoroborate bath) looked good
but were actually deposited on a highly passivated copper layer. Upon
reflow, the tin lead showed immediate wetting problems - you can plate
tin-lead on surfaces which would not wet well.

Given these observations, I would lean towards a shorter shelf life if the
tin-lead is not fused (reflowed), and take storage precautions if possible.
You might want some sampling of the fresh parts to see that they have good
wetting characteristics.


regards,



Jerry Cupples
Interphase Corporation
Dallas, TX USA
http://www.iphase.com

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