3D Fan-Out Package Technology with Photosensitive Through Mold Interconnects

Fan-out package technology for realizing high density and high integration is promising for 3D integration. This paper presents an innovative 3D fan-out packaging technology with photosensitive through mold interconnects. This is the first-time demonstration of 3D integration based on fan-out technology using a photosensitive mold compound material to provide high-aspect-ratio and fine-pitch through mold via openings, thereby advanced substrate-free packaging. 10 × 10 mm Si test dies with 100-μm thickness was prepared to confirm feasibility of the 3D integration packaging process. The chip design comprises over 2000 pads with a 200-μm pad pitch. After embedding the test die into a thick photosensitive molding compound, the lithography process conditions for shallow vias on the die and deep visa around the die were evaluated to realize a 3D integration packaging without conventional tall electroplated Cu pillars. The prototype package with photosensitive through mold interconnects shows a decent reliability over a 1000-cycle package-level thermal cycle test, a 1000-h high-temperature storage test, and a 96-h pressure cooker test. Thermal stress simulation has revealed that package warpage with the photosensitive material is small compared with that of a widely used epoxy molding compound for chip first fan-out wafer-level package. This study demonstrates future viability of the fan-out process using a photosensitive molding compound to enhance the versatility of 3D integration, thereby dramatically expanding the application field for fan-out packages.