After drilling, the protective material on the surface should be removed so that it can go to next step of copper spurring or conductive film printing, also the residue in the holes should be cleaned completely. Otherwise, it will affect the vacuum sputtering on the surface of ceramic and the adhesion of copper molecules or conductive material in the holes, especially for the DPC process. For thick-film circuits, this process may not be applicable or simple because the holes in thick-film circuits are relatively large.
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