Effects of materials properties of epoxy molding films (EMFs) on fan-out panel-level packages (FOPLPs) characteristics

Abstract

Fan-Out Packages (FOPs) technology is actively researched because it enables high Input / Output (I/O) pads density, thin package, and cost reduction. Epoxy Molding Compound (EMC) materials play a major role in implementing FOPs. EMC acts as a substrate and also protects the chips from the outside. Recently Epoxy Molding Films (EMFs) have been introduced because EMFs are advantageous for large-area molding and can solve planarization problem. However, there are many problems before using at FOPs such as voids, delamination, warpage, and die shift. Voids and delamination occur when moldability is bad. Coefficient of Thermal Expansion (CTE) mismatch between the EMFs and the chips induces thermo-mechanical stress resulting in a warpage during the molding process. Furthermore, die shift from their original position can be also found by warpage, resin flow, and curing shrinkage. Therefore, EMFs materials properties and their effects on FOPs characteristics should be investigated.

In this study, thermo-mechanical properties of EMFs were optimized by epoxy formulation to improve FOPs characteristics. Epoxy, silica contents, curing agent, and additives (coupling agent, carbon black) were investigated to produce low CTE and high Glass Transition Temperature (Tg) properties. Then, multiple $10 mm \times 10 mm \times 200 \mum$ chips were molded with the size of $100 mm \times 100 mm$ using $400 \mum$ thick EMFs. The chip to chip distance could be reduced from 12 mm to 5.7 mm without voids and delamination. The warpage of EMFs were measured using 3 Dimensional - Digital Image Correlation (3D - DIC) method, and the effects of process conditions on the warpage of EMFs were also evaluated. And the die shift after molding was quantitatively measured assessed by optical microscopy. Finally, thermal cycle and $85^circ C$/ 85 % RH tests were performed to evaluate the FOPs using optimized EMFs