I am in need of some assistance with a problem we are having with soldering some terminals... Basicaly I need to solder thin tabs onto a round metal post (hole through tab) We have been seeing poor quality joints, de-wetting and what looks like some blackening of the posts during this process. Analysis / sectioning of some of the soldered connections shows that some of them have 3-5 microns of silver and some have sub-micron thickness plating. A local specialist reckons that with enough heat we should be able to solder to the brass pin beneath regardless but we are seeing that the more heat applied the worse the joint gets.
Has anybody got decent experience with surface platings ? I need to understand the intermetalics going on and what thickness of plating we should be specifying for our CofC.
You should be able to solder to brass - check with you flux supplier to get their recommendations. The flux you are using may not have enough activation to breakdown the oxides on the brass surface.
A word of caution - brass (copper and zinc alloy) can undergo 'dezincification' if there is no barrier plating between the brass and your solder joint. In some use environments this becomes a latent defect.
Your brass bits supplier should be familiar with this and have a standard process on his books. We'd expect to see a nickel or copper barrier.