Through Mold Via Development Using Laser Drilling Process for 3D Fan-out Wafer Level Package

Microsecond UV laser drilling technology was used to form through mold vias (TMVs) with different aspect ratios, which can be applied to 3D Fan-Out Wafer Level Packaging (FOWLP). A test vehicle was designed to test the electrical continuity of through mold vias with different aspect ratios. The test vehicles consisted of a thick Cu pads electroplated on a substrate, mold compound was molded over the Cu pads and UV laser was used to form the blind vias. A thick Cu metallization was formed over the laser drilled blind vias to complete a daisy chain test structure. Trepanning method was used to created concentric laser paths, along with different Top-hat beams sizes to produce TMVs of different aspect ratios. Electrical continuity test, cross sectional and X-ray were used to verify the TMV daisy chains. The electrical test, cross sectional and X-rays shows good continuity in the TMVs structure.