Investigating copper wire bonding technology in Chip-on-Board applications

In our experiment, the possibility of forming copper wire bonds in Chip-on-Board (COB) applications was investigated. In the experiment, such surface finishes were studied and compared which are common in printed circuit board based COB applications and can be bonded with wire bonding technologies. These finishes were immersion silver (ImAg), electroless nickel / immersion gold (ENIG) and electroless nickel / electroless palladium / immersion gold (ENEPIG). On each type of surface finish, copper wires with two diameters (33 and 300 μm) were bonded with a TPT Ultrasonic bonder. The wire bonds then characterized by optical inspections and mechanical measurements which are detailed in the paper.