Wire Bondable and Solderable Gold

In applications where wire bondable and solder-able surface finishes are desirable. R&D has developed a process where a Thin and thick coating of Au can be deposited onto the same side of a board. This is accomplished by first plating a thin coating < 10 micro inches (.000010”) of soft bondable Au over 150 – 300 micro inches of Ni on all circuit features. This Au coating should be kept < 10 micro inches in order to avoid Au embrittlement problems. Once this thin Au layer has been deposited we then will strip the primary resist and apply a new resist compatible with the wire bondable Au chemistry. This resist will be exposed with a second photo tool, which defines only the wire bond pads. It is necessary to allow for up to +-.003” of miss-registration from first image to second image due to accommodate registration tolerances. This can be accomplished through designing the bond pads .006 mils larger in at least one axis, in order to accommodate registration tolerances. Please see the illustration to your right! We then plate 60 micro inches (.000060") minimum soft bondable Au over all exposed pads. This gold layer is kept to 60 micro inches minimum to ensure high pull strengths, and in turn high yields through the manufacturing process.