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Copper-Plating the Throughholes of Printed Circuit Boards and Cards

IP.com Disclosure Number: IPCOM000043938D
Original Publication Date: 1984-Oct-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Ruh, WD: AUTHOR

Abstract

A sputter process is described which, by using a frequency in the kHz range, permits the throughhole walls of printed circuit boards to be uniformly coated with a copper seed layer. The printed circuit board is positioned between two copper electrodes having at least the same size as itself. Copper electrode sputtering is effected at a frequency of up to about 50 kHz. Up to that value, the ions are still capable of following the amplitudes of the AC voltage applied. They have sufficient time at each half-wave to effect a complete DC discharge at the respective electrode, so that the copper of the two electrodes is uniformly sputtered. As the copper is sputtered into the throughholes from either side, a very uniform copper layer is sputtered on the hole walls.

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Copper-Plating the Throughholes of Printed Circuit Boards and Cards

A sputter process is described which, by using a frequency in the kHz range, permits the throughhole walls of printed circuit boards to be uniformly coated with a copper seed layer. The printed circuit board is positioned between two copper electrodes having at least the same size as itself. Copper electrode sputtering is effected at a frequency of up to about 50 kHz. Up to that value, the ions are still capable of following the amplitudes of the AC voltage applied. They have sufficient time at each half-wave to effect a complete DC discharge at the respective electrode, so that the copper of the two electrodes is uniformly sputtered. As the copper is sputtered into the throughholes from either side, a very uniform copper layer is sputtered on the hole walls. The electrodes may take the form of plates, punched plates or rods. The described process may also be used to copper-plate the surface of the boards and cards. In such a case, the sputtered copper layer is used as a seed layer for structuring conductors by electroplating processes. Compared with sputtering by means of two magnetrons, between which the board is moved in a vacuum, the described process has a number of advantages. All hole walls are simultaneously and uniformly copper-plated, as the electrodes cover the entire surface of the boards. The copper electrodes are uniformly eroded across their entire surface. The arrangement for impl...