Recent advancements in MCM-L imaging and via generation by laser direct writing

The paper presents some preliminary results and describes the state of a research project that aims at the improvement of the quality of MCM-L circuit boards by the application of UV lasers for the following processes. 1) Pattern generation by direct writing using Nd:YAG (IR, visible or UV) laser. The copper clad laminate is covered by some protective layer, and the pattern is directly written to this layer by material removal (ablation). The pattern of the copper layer is prepared either by wet chemical etching or applying the electroplating-stripping-etching process sequence. 2) Photo-mask exposure by direct writing. In this case a photoresist protective layer is exposed by a UV He-Cd laser, and after developing it is used for the conventional image transfer process. 3) Through board via generation by contour direct writing using frequency multiplied Nd:YAG laser. It means that holes are drilled by moving the well-focused laser beam along their contour. 4) Blind via generation by controlled number of pulses using the same frequency multiplied Nd:YAG laser. In this case the whole area of the via is exposed, and the hole is deepened shot by shot