Study on Effects of Solder Fluxes on Catastrophic Mirror Damages During Laser Diode Packaging

Solder fluxes have been commonly used in die bonding of high-power semiconductor lasers via indium solder. In this paper, the effects of some fluxes, with respect to reflow duration and cleaning solvent residues on the catastrophic mirror damage (CMD), are investigated. Scanning electron microscopy with an energy dispersive X-ray indicates that an increment of the sites of CMDs, size, and quality, obtained by increasing the reflow duration, depends on the type of the used flux. Fourier transform infrared spectroscopy confirms that nearly no contamination of the flux exists after the cleaning process. X-ray photoelectron spectroscopy analysis revealed that the flux or flux cleaning solvent residues could not be the main source of carbon or carbon compounds on the surface and, hence, the CMDs attributed to them. Finally, indium packaging of a diode laser by means of these rosin fluxes shows that RA flux has the best die bonding quality among other fluxes.