UNDERFILL PROCESS FOR FLIP-CHIP LEDS

摘要

An underfill technique for LEDs uses compression molding to simultaneously encapsulate an array of flip-chip LED dies mounted on a submount wafer. The molding process causes liquid underfill material (or a softened underfill material) to fill the gap between the LED dies and the submount wafer. The underfill material is then hardened, such as by curing. The cured underfill material over the top and sides of the LED dies is removed using microbead blasting. The exposed growth substrate is then removed from all the LED dies by laser lift-off, and the underfill supports the brittle epitaxial layers of each LED die during the lift-off process. The submount wafer is then singulated. This wafer-level processing of many LEDs simultaneously greatly reduces fabrication time, and a wide variety of materials may be used for the underfill since a wide range of viscosities is tolerable.