Influence of Bonding Temperature and Applied Load on the Bonding Integrity and Optical Performance of Face-Down Bonded Ridge-Waveguide Lasers

The effects of bonding temperature and applied load on the mechanical integrity of 80Au-20Sn solder joints and the optical performance of laser diodes (LDs) are presented. Insufficient solder wetting at 280°C and poor joint integrity at an applied load below 0.196 MPa resulted in solder failure during die shear test. As the bonding temperature and applied load increased, the joint integrity and the optical performance improved. Shear testing further showed fracture in the LD due to the high mechanical strength of 80Au-20Sn solder and good adhesion properties of the solder joint. Microstructure studies showed good metallurgical stability with little interfacial intermetallic compound (IMC) formed. However, beyond an applied load of 0.523 MPa, the LD performances degraded due to modification of the bandgap energy in the active region. From our experimentation, a bonding window with good bonding integrity and high optical performance was, nevertheless, achieved.