In the process watt solution is used and sulphur containing additives (brigther&carriers) are also added. It is known that carrier supply sulphur into coating. but i wonder whether this sulphur is introduced to copper during electroplating. Because the copper with 0.2 mm thickness fracture in brittle manner after plating (not the coating layer; copper it self fracture).

I suspect sulphur causes grain boundary embrittlement. Does it make sense? Is it possible.

Note: Thickness of coating is 4 microns