Improvement of thickness uniformity in nickel electroforming for the LIGA process

An effective method to improve thickness uniformity in nickel electroformin g for the LIGA process to produce metallic microstructures is described. Th e deposited metal distribution is naturally a concave shape over the whole area of the plating base proved by experiments. The edge thickness of the p lating area is usually twice or higher than the center of the plating area. A secondary cathode (guard ring) was applied to improve the electroform un iformity. The experimental result of a Joule-Thomson micro-cooler proved it s feasibility. The thickness ratio of edge to center of a 500 mu m sample d ecreased from 2.5 to 1.4. The thickness uniformity improvement is achieved without a loss in plating rate in the center of the features. (C) 2000 Else vier Science Ltd. All rights reserved.