Blind Via Hole in Multi-layer AFRP Printed Wiring Boards by Build-Up Process

In the printed wiring board manufacturing sector, methods have been developed to improve the circuit packaging density. The multi-layer printed wiring board manufacturing process is receiving particular attention. In the current manufacture of these boards, the method frequently used is to laminate the core with insulating resin, namely a build-up process. Etching is generally used to form the holes connecting the circuits of these boards. However, a problem has emerged in that the strength of the substrate decreases due to the insulating resin part as the multi-layers are progressively formed. Thus, it becomes necessary to use FRP for the insulation layer part. Since it is very difficult to etch composites, lasers have been proposed for a new way to drill holes in such materials. By appropriate adjustment of the laser penetration energy, the holes are drilled only in the insulation part, and a technique is proposed to stop the holes using the copper foil forming the circuit. AFRP has been considered a suitable FRP for such laser processing. In the present study, attempts were made to experimentally produce multi-layer boards using AFRP and GFRP for the build-up insulation layer, and the characteristics of blind via holes drilling with a small power laser were investigated.