Soldering with solid state and diode lasers: Energy coupling, temperature rise, process window

The increasing number of electrical contacts in automobiles in combination with more complex and miniaturized components leads to higher requirements for the joining technologies. In that context, laser soldering represents a n interesting alternative to conventional techniques. So far, solid state l asers [Nd:yttrium-aluminum-garnet (YAG)] and CO2 lasers have been successfu lly applied in industrial production. Recently, the development of high pow er diode lasers has offered a new laser source for soldering with technolog ical advantages. Absorptivity of laser radiation on metals, generally incre ases with shorter wavelength and, consequently, diode lasers may lead to a higher process efficiency compared to Nd:YAG lasers. The absorptivity of co pper alloys with different surface conditions has been measured at 808 nm ( diode) and 1064 nm (Nd:YAG). When heating up the solder joint, the intensit y distribution of the different laser spots becomes important, too. This ef fect is demonstrated by means of process modeling and temperature measureme nts for a typical joint geometry. For the case of soldering strip-to-strip joints, the effects of the different energy absorption on the process are p ointed out. (C) 2000 Laser Institute of America. [S1042-346X(00)00705-1].