Filling through holes and blind microvias with copper using reverse pulse plating and insoluble anodes

Abstract

PurposeThe purpose of this paper is to present a summary of development work made in technical centres and on the subsequent customer qualification of copper filled through holes and blind microvias.Design/methodology/approachVarious copper deposition parameters were investigated in a small‐scale production line which was then extended to full‐scale production qualification in a horizontal conveyorised system. Samples of substrates with copper filled through holes were qualified at end‐user facilities.FindingsThe copper plating process may be used to replace an existing production process for printed circuit boards. The proposed system can give a more reliable result in terms of filling and technical capability for the produced substrate. Overall production cost savings are possible.Research limitations/implicationsThe technology is based on a copper plating electrolyte using a redox pair for copper replenishment. The results achieved depend on use of this system and on production equipment which can control the redox system and copper concentration within a tight range.Originality/valueThe paper shows how the use of a horizontal production system with redox copper replenishment can achieve filling of though holes and blind microvias with reduced surface plated copper thickness. Reduction in the use of copper saves both resources and also reduces production costs. The process is proposed as an alternative to existing paste plugging processes, which are both cost and labour intensive.