Laser microsoldering of tape‐automated bonding leads using an Nd:YAG laser end‐pumped by a laser diode bar with gradient index lens array coupling

Abstract

A laser soldering of tape‐automated bonding (TAB) leads is tried with a diode‐pumped Nd:YAG laser. A 15‐W laser diode bar, a multistripe monolithic laser diode array, is used to end‐pump Nd:YAG. Twelve beams emitted from 12 stripes, center‐to‐center spaced 800 μm, of a 1‐cm linear diode array were collimated by a lens array of width 1 cm, consisting of 12 gradient‐index (GRIN) lenses with 800‐μm width, to pump the Nd:YAG facet. The maximum Nd:YAG output power at 1064 nm of 6.3 W is obtained in cw operation. The Nd:YAG laser beam is focused to a spot with a FWHM diameter of 112×37 μm. A TAB device with 215‐μm‐width leads, center‐to‐center spaced 430 μm, is successfully soldered by 98‐ms irradiation of the laser power of 5.8 W/lead. Soldering is tried with a fiber‐coupled Nd:YAG output as well. © 1996 Society of Photo−Optical Instrumentation Engineers.