BONDING STRESS MEASUREMENTS FROM THE DEGREE OF POLARIZATION OF FACET EMISSION OF ALGAAS SUPERLUMINESCENT DIODES

Mechanical stress induced by bonding AlGaAs superluminescent diodes to Cu, SiC, or diamond heat sinks using 40% Pb-60% Sn or 80% Au-20% Sn solder has been observed using measurements of the degree of polarization of the facet emission at low current levels. Stresses up to 10(9) dyn/cm2 were observed, with the magnitude of the stress dependent on the solder used, and the sign of the stress dependent on the difference in thermal expansion coefficient between the diode and the heat sink. Relaxation of the bonding stress over time was investigated as a function of temperature for each solder. The implications of the relaxation on the interpretation of high-temperature life tests of superluminescent and laser diodes are discussed.