Solder deposition for transient liquid phase (TLP)-bonding by MSIP-PVD-process

Abstract

In different technical areas micro electro mechanical systems (MEMS) are in use today. The components of these MEMS. consist of various materials, which are joined together. To join materials like ceramics, plastics or metals to a hybrid MEMS. a low temperature joining process, e.g. transient liquid phase (TLP) or an active soft soldering process can be performed. In this article, the TLP solder system is a binary multilayer system of thin films. One of the films had a high (Cu) and the other a low (In) melting point. The layer system was deposited with a magnetron sputter ion plating (MSIP)-PVD-process. In this article, the deposition of the low melting component indium with an active substrate cooling is presented. The substrate temperatures were set and controlled by an additional cooling unit, which was integrated into the sputtering facility. In the performed experiments a substrate temperature range from −40 °C to room temperature was investigated. The effects of these different substrate temperatures to the microstructure and the soldering suitability of the TLP solder systems were investigated by scanning electron microscopy (SEM), nanoindentation and soldering tests. In this article it was shown that Cu–In–TLP solder systems deposited with cooling periods showed an insufficient solder ability due to the Surface roughness. Solder systems deposited at low substrate temperatures set with a cooling unit showed a good solder ability. Also, the layer structure became amorphous, dense and homogenous.