Development of a laser processing technology for high thermal radiation multilayer module

We developed a laser drilling technique using UV laser (lambda=355nm) for epoxy resin that includes aluminum oxide filler at high density to realize a high thermal radiation multilayer module. By studying the laser condition to see what conditions enable the via hole to make good contact with the metal layer, it was found that both laser fluence and a beam diameter had threshold. Here threshold fluence was lower than threshold diameter, so when the diameter was smaller than the threshold, unprocessed aluminum oxide filler remained in the via hole. Hence, when the resin with high density filler was irradiated with a UV laser, while the resin evaporated the aluminum filler with high melting point was hardly processed but rather discharged from the via hole with the gaseous resin. It follows from this that high speed drilling by low laser fluence is possible when the filler size is smaller than the via hole diameter, and we realized a high thermal radiation multilayer substrate at low cost. Applying the developed laser drilling technique, we made inverter modules. Measuring the temperature distribution using IR camera, heat from the power device was diffused to the metal substrate through thermal via holes