| abstract |
An electrical interconnection substrate (20) is prepared to receive both wire bonded and soldered connections (60,64,66) by forming a dielectric solder mask (30) over the substrate (20), with openings (36) in the mask (30) to expose the contact pads (22) for which soldered connections are desired. The substrate (20) is exposed to a molten solder alloy (44) in a wave soldering process that dissolves the wire bonding material (28) (preferably gold) from the exposed pads (22) and deposits solder bonding pads (52) in its place. Excess solder is then removed from the substrate, and openings (54) are formed through the solder mask (30) to expose the wire bond contact pads (22'). The selective dissolving of gold bonding layers (28) and their replacement by solder pads (52) prevents the establishment of brittle gold-solder intermetallics, and the deposited solder (52) requires no further heat treatment for correct alloy formation. |