New soldering processes and solder systems for hybrid microsystems: developments and applications

One of the promising joining technologies for the assembly of hybrid microsystems is soldering. This technique meets the specific requirements of the microstructures, like a high flexibility concerning materials and geometry and low process temperatures ensuring the function of the joined components. Soldering offers the possibility of joining different materials in an easy way. Regarding the temperature aspects, the soldering processes can be carried out by low temperature to guarantee any damages in the joined components. Two soldering technologies are examined in this study: transient liquid phase (TLP) bonding and active soldering. Active solders based on Sn and different TLP systems have been developed and optimised according to the requests of the microsystems being joined. The application of the solder systems by magnetron sputter physical vapour deposition has been investigated. The deposition temperature has to be lower than the later joining temperature and lower than the melting points of the solder materials. This fact is a great challenge for the PVD process. The presented investigations and results are acquired within the project SFB 440 “Assembly of Hybrid Microsystems”, financed by the “German Research Foundation” (DFG).