Preparation of tin diffusion coatings on copper

AbstractProcesses have been developed to produce single-phase copper–tin coatings of either the terminal solid solution or the Cu3Sn (e) intermetallic compound on a copper substrate by a method not involving electrolytic codeposit ion. A ‘precoating’ was deposited which consisted generally of one or more pairs of alternate 1 μ thick electroplated layers of tin and copper. Heat treatments were chosen to promote diffusion between molten tin and solid copper. The preferred technique was to use a copper top layer as part of the precoating to prevent dewetting of the tin. The alternate-layer method significantly reduced the time required to produce 10 μm coatings of Cu3Sn by partitioning the tin into several separate diffusion systems.