What causes bright acid tin to become “gritty” after soldering? The parts look beautiful after plating but the surface turns gritty after our customer solders the parts. D. E.
You, more than likely, have too much brightener in your acid tin plating bath. The brightener is incorporated into the plated deposit and you get a very attractive finish. When the bright tin is heated and becomes molten the organic material migrates to the surface and hence the gritty like appearance. Try reducing your brightener level in the plating bath and do talk to your chemical vendor about this problem.