OPTIMIZATION AND RELIABILITY EVALUATION OF A LASER INNER LEAD BONDINGPROCESS

A series of designed experiments have been performed to determine the process window for laser inner lead bonding (ILB). The parameters stud ied were power, pulse time and lead contact. Bond pull tests were used as the monitor for these evaluations. The results of the experiments have demonstrated that the laser bonding process is very insensitive t o wide variations in the parameters studied. Laser-bonded test devices have been subjected to extended high temperature storage and temperat ure cycle tests and compared to conventional thermo-compression (TC) b onded devices under the same conditions. By comparison to the TC-bonde d devices, laser bonded samples have lower average bond pull failure s trength, but exhibit a more uniform strength distribution and a slower rate of decline in bond pull strength over time in either of the stre ss tests. Catering, which is a bond pull test failure mode that become s increasingly significant over time at test for the TC-bonded devices , is almost totally absent from the laser-bonded samples.