Gold thermosonic wire bonding of aluminum pads located on thick polyimide films has been studied. Bond pull and bond shear studies indicated that the weld between the wire and pad was very poor, resulting in unacceptable failure strengths and failure modes. The incorporation of a thin Ti layer between the aluminum and polyimide was found to improve the weld quality and reliability dramatically. This improvement is attributed to the increased bond pad rigidity in the presence of Ti, which allows for a more efficient transfer of the ultrasonic energy to the wire/pad interface.<<ETX>>