Q. Is a copper flash required between a gold plate and beryllium copper (BeCu) base material? I’ve been told it promotes better adhesion than gold over BeCu base material, but would like to know the technical reasoning behind this. Note, my application does not allow a nickel strike. —W.D.
A. As you know, beryllium copper alloys are not the easiest materials to plate. The surface of the base material must be thoroughly cleaned to remove copper oxides and other impurities that are present on the surface. Assuming you clean the surface properly, you can plate directly on the beryllium copper alloy. However, there is another problem that is somewhat more subtle and will cause the plate to not adhere to the surface in a satisfactory manner. This particular problem has to do with copper migrating into the gold layer and forming compounds on the surface between the copper alloy and the gold. These compounds tend to reduce the adhesion of the gold to the base material and discolor the gold layer. This is one reason why a barrier layer such as nickel is plated on the base material. Using a copper layer on the BeCu base material will not solve this problem.
As far as using another material as a barrier layer, an alloy plate with the trade name Albaloy is sometimes used to replace the nickel. Albaloy (also called tri-metal alloy or white bronze) is a tin-zinc-copper alloy with properties similar to nickel.