Hello, I would like deposit solder bumps on 100um-by-100um aluminum pads; I also have other exposed metals (Cr, Au) on my chip. I came across a technique where the chip is dipped into a hot solution in which a low melting temperature alloy (Field's metal, Cerrolow 136, etc.) is melted; the metals are selectively deposited on the exposed aluminum pads. These alloys usually contain Bismuth, Indium, Tin and Lead. Does anybody have experience with this? Any ideas on selectivity of deposition onto different materials (Cr, Au)?. Any recipes that I can use? Thanks, Emre -- Mustafa Emre Karagozler Graduate Student Carnegie Mellon University Department of Electrical & Computer Engineering 5000 Forbes Avenue Pittsburgh, PA 15213