Gold wire bonding onto flexible polymeric substrates

Copper clad polymeric materials were examined as potential substrates for wire bonded chip-on-flex circuits. New thermoplastic flex and a PTFE/woven glass substrate were evaluated along with polyimides using high temperature copper laminate adhesives and adhesiveless constructions. Initial wire bond pull tests indicated all the materials were suitable for high temperature gold wire bonding. Similarly, conventional glob top encapsulants were found to adhere to each of the thirteen substrates tested; experimental UV curable glob top materials were found to adhere well to polyester and PTFE substrates, but not to polyimides or polyether imides.