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PCB007-Aug2021

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98 PCB007 MAGAZINE I AUGUST 2021 Filling Copper in Laser Drilled Through-holes Complete void-free fill was not only achieved in the mechanically drilled through-holes but also in laser drilled through-holes. 200 µm thick laser drilled panels with electroless seed layer were used for evaluation. 200 µm thick core with 100 µm diameter through-holes e laser drilled panels used for evaluation had 200 µm thick electroless seed layer. e di- ameter of the through-holes was 90–100 µm at the top and bottom while the center was 55– 65 µm. e plating was carried out for a total time of 78 minutes with the time for bridging at 16 minutes and that for filling at 62 minutes. e bridging was performed for 5 µm and fill was carried out for 20 µm. Void-free fill was achieved in the through-holes as shown in the cross-section picture (Figure 11). Figure 9: Process capability: Filling a wide range of through-hole diameters and panel thicknesses. Figure 10: X-Ray image of 400 µm thick x 200 µm diameter through-holes. Figure 11. 200 µm thick panel: 90–100 µm diameter filled through-hole.

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