Abstract
In the current manufacture of multi-layer printed wiring boards (PWBs), the method frequently used is to laminate the core with insulating resin as build-up layers. Then, micro-via drilling technology using laser has become the dominant method of drilling smaller blind via holes of build-up layer. Cu direct laser drilling attracts attention to a new method in this field. However, there is no reports dealing with Cu direct laser drilling of PWBs. The purpose of the present report is to research the feature of Cu direct laser drilling and establish the method in order to improve hole quality. Following conclusions were obtained : (1) The technique using the infrared thermography was proposed in order to examine the laser absorptance of the surface copper foil. (2) The method of mixing fillers in the build-up layer was effective to improve hole quality by reducing the difference of the laser processing threshold between the copper foil and the build-up layer. (3) The technique was established to estimate the overusing FEM analysis.
