Hermetic Wafer Level Packaging of LED Modules with Phosphor Ceramic Converter for White Light Applications based on TSV Technology

Abstract

In this work we present the development of a new hermetic wafer level packaging approach for fabrication of white light LEDs with suspended phosphor ceramic converter. In this new architecture, the ceramic converter is not directly attached to the LED chip but part of the package and is arranged with a defined distance to the LED. This enables the heat generated by the light conversion to be dissipated directly via the ceramic converter into the package instead of through the LED itself. The packaging approach relies on through silicon via (TSV) based silicon interposer wafers which are wafer to wafer bonded to silicon frame wafers using AuSn seal rings to form cavity wafers. The frame wafers have through cavities with sloped mirroring side walls to enable an optimal reflection of light out of the cavities and thus a high light efficiency of the mounted LEDs.The LEDs are bonded into the cavities onto the silicon interposer which feeds the electrical contacts to its back side. The cavities with the mounted LEDs are subsequently sealed with the phosphor converter ceramics. The created LED modules are assembled to test boards were the thermal resistance of the package was determined and compared with simulation results.