TWI Industrial Member Report Summary 417/1990
S T Riches
Ni-Cr strain gauges are used extensively on pressure transducers. Interconnections to the strain gauges are normally made by Au plating the Ni-Cr thin film metallisation which is then thermosonic or thermocompression bonded with Au wire (typically 25-33µm diameter). There is interest in bonding directly to the Ni-Cr thin film metallisation, thereby eliminating the Au plating process. There is a corresponding desire to eliminate the Au plating operation from the external connections so that wire bonding can take place to unplated Cu on printed circuit board material.
This report investigated the feasibility of ultrasonic wire bonding of (25µm diameter) Au, Al-1%Si and Cu wire to Ni-Cr thin film metallisations on glass. Data on the consistency and reliability of Al-1%Si ultrasonic wedge bonds to Ni-Cr thin film metallisations on glass and Cu tracks on printed circuit board are presented.