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 /spl mu/m) and near IR (1.064 /spl mu/m) spectra. This combination of wavelengths overcomes the difficulty of bonding gold with only 1.064 /spl mu/m radiation where 98% of the radiation is reflected. In the method presented in this paper, 0.533-/spl mu/m radiation, of which 25-50% is absorbed by gold, is used to heat the gold which becomes more absorptive to the 1.064-/spl mu/m 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.<
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