Laser Drilling of Thru Mold Vias (TMVs) for FOWLP Application

Present study focuses on high aspect ratio Thru Mold Via (TMV) fabrication using nanosecond laser drill tool. Epoxy mold compound (EMC) with 25um filler size is used to demonstrate 50um diameter TMV. Smaller via size with increase in high I/O count and thinner packages are key platforms for system in package (SIP) and package on package (PoP) applications. A UV laser source is employed to ablate both resins and silica fillers and at the same time stop, on a 6um thin copper substrate. Extensive DOE has been conducted with the proper combination of laser power, energy, and frequency, TMV with an almost vertical side wall profile achieved with clean opening, residue free via bottom and without any delamination of inter layer dielectrics. Achieved TMV diameters are in the range of 50 +/- 2 um and via side wall angle around 88 +/- 1 degrees. Dielectric patterning structures are employed for wafer alignment during drilling process and at the same time these same patterns are used for TMV positioning.