Importance

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Abstract

A novel process is provided for the high speed fabrication of flexible printed circuit boards in continuous roll form and at a cost which is substantially less than the cost of existing fabrication processes. A web of substrate material is supplied from a roll and one or both surfaces are sputter coated with a tie-coat of Monel or chrome and a copper seed layer. The tie-coat is typically of a thickness of about 50-300 angstroms, and the copper seed layer has a thickness of about 200-4000 angstroms. Plated through holes are provided for double sided printed circuit boards, the holes being provided by laser or other suitable drilling equipment in an intended pattern on the substrate. A plating mask is provided with a negative image to allow subsequent selective electrodeposition of copper onto the unmasked areas of the substrate surfaces. The web is then passed through a continuous copper plating cell which provides a plate-up of copper on the unmasked areas of the seed layer. The web next undergoes a stripping process for the removable of the plating mask. Thereafter, a soft subtractive etching technique is employed to remove the sputtered layers of Monel and copper. Since the soft etching removes only the thin sputtered metal layer, exceptional line resolution can be achieved in a highly cost effective manner. Moreover, the process is environmentally friendly since smaller amounts of metal are removed in comparison to conventional techniques thereby minimizing the amount of waste to be disposed of.

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First Claim