THE ELECTROLESS COPPER PLATING OF SMALL VIA HOLES

The Build-up method is becoming an important process with the increase in electric wiring density and miniaturization of the hole diameter. Preparation and circulation of plating solutions become difficult in t he via hole with reduction of the hole diameter, so that uniformity of deposits decreases and this leads to lowering the electric reliabilit y between each layer. Therefore the uniformity of electroless copper p lating was investigated using small via holes (20-100 mu m phi, 30-230 mu m depth) prepared on the wiring board Uniform deposits were obtain ed by changing the parameters related to the deposition characteristic s. The possibility of via filling by the electroless copper was also i nvestigated.