Deposition of solder for micro-joining on M.E.M.S. components by means of magnetron sputtering

Micro electro-mechanical systems (M.E.M.S.) are used in many different technical areas, e.g. automotive control, information technology, biomedical or environmental application. Due to an increasing miniaturisation of components and devices and a great variety of materials, the M.E.M.S. has become very interesting. To mount different materials like ceramics, plastics or metals to hybrid M.E.M.S., sophisticated joining technologies have to be developed. The assembly and mounting of micro-components can be performed by a low temperature joining process, e.g. transient liquid phase bonding (TLP) or low temperature active compound joining. For these joining techniques, a solder system has to be deposited on the M.E.M.S. components locally. The TLP solder system is a composition of a thin film layer with a high melting point (e.g. Cu, Ni and Ag) and a second thin film with a low melting point (e.g. Sn, In and In–Bi). The deposition of a low temperature active compound solder system recommends an ingenious field of process parameters because of the multiplicity of solder elements, their stoichiometry and distribution within the deposited film. The deposition process can be carried out by the magnetron sputter ion plating (MSIP) PVD technique by adapting process parameters like discharge power, total gas pressure, substrate bias, or substrate heating, to obtain a defined film constitution. This paper presents the first results of solder deposition on different M.E.M.S. materials like silicon and glass, for the TLP joining process. The microstructure, morphology, and bond strength of the deposited solder layers are discussed in the context of deposition parameters.