MEMS technology on wafer-lever LED packaging

This study demonstrated a newly type technology of a wafer level packaging method for light emitting diode (LED) with aspheric lens and microlens array using microelectromechanical systems (MEMS) technology and transfer molding process. The novel packaging structure includes two components: the silicon-based packaging substrate which is formed with arrayed reflector depression and through-hole interconnects by bulk micromachining and the optical encapsulation with lens configuration that formed by transfer molding in wafer level. By this pattern transfer process, the precise alignment between lens configuration and the reflector of silicon substrate can be achieved and batch process can be realized to reduce the costs. Beside, the packaging element can be used more applications. In the study, the pattern transfer of various lens profiles was also accomplished successfully by using silicone gel as lens mold. The brightness of the packaging elements with single aspheric lens profile and high fill factor microlens array can be increased by 26% and 16%, respectively, in comparison to the case of optical encapsulation with smooth curved surface. Furthermore, the light radiation uniformity was improved effectively through 100% fill factor microlens array. Therefore, the structure can satisfy the requirements of wafer level LED packaging and improve the heat dissipation and light extraction efficiency.