Gold-to-gold TAB ILB with a laser

A new method for bonding gold plated TAB leads to gold bumps is presented. This method uses a frequency doubled Nd:YAG laser which provides energy in both the visible (0.533 μm) and near IR (1.064 μm) spectra. This combination of wavelengths overcomes the difficulty of bonding gold with only 1.064 μm radiation where 98% of the radiation is reflected. In the method presented in this paper, 0.533-μm radiation, of which 25-50% is absorbed by gold, is used to heat the gold which becomes more absorptive to the 1.064-μm radiation that is used to form the bond. Bonding experiments were conducted and samples were exposed to environmental testing. While there were initial bond failures, 85% of the bonds did not degrade during environmental exposure indicating the potential for the process