PWB using mechanically pre-drilled metal Clad film for IVH and build-up PWB with laser via hole for semiconductor package substrate

We developed two types of PWBs (printed wiring boards): HITAVIA type 1 and type 3. HITAVIA type 1 is a multi-layered PWB with IVHs (interstitial via holes) on surface, employing the low flow resin MCF (metal Clad B stage insulation resin film). The technical key point is the lamination of mechanically pre-drilled MCF on the inner core board to prevent the deformation of the pre-drilled hole and void in the insulator of the MCF. We utilized the newly developed high molecular epoxy resin for the base polymer of the insulation resin of MCF, that makes the formation of small drilling holes (0.25 mm diameter) easier. In this process, only a single plating step, after the drilling step of TH (through hole), can interconnect IVHs and THs simultaneously. Utilizing the thin MCF (50 microns insulator) makes the thickness of HITAVIA type 1 thinner than that of conventional PWBs with IVH. We also developed another type of MCF with high glass transition temperature epoxy resin system and special fibrous filler which allows easy formation of IVH (0.10 mm diameter) by laser ablation. The insulator has appropriate resin flow to fill up the inner buried via holes of the core board, thereby maintaining the flatness of the substrate which allows fine line formation. HITAVIA type 3 with this MCF passes the following tests which are required for semiconductor packages such as BGA (Ball grid array). These are: 1000 reliability test cycles as per MIL-107 condition B, and four days of pressure cooker testing (121 °C, 1.2 atm).