Process Optimization in Transient Liquid Phase Soldering (TLPS) for an Efficient and Economical Production of High Temperature Power electronics

Abstract:
The fulfilment of the goals towards the miniaturisation of devices while increasing the power densities and reducing the losses, requires reliable and cost-effective solutions for the production of power electronic modules. This is associated presently with the integration of wide-bandgap (WBG) semiconductor materials and corresponding design customization. Diffusion soldering particularly Transient Liquid Phase Soldering (TLPS) which is a proven thermally stable die-attach technology has been focused in this contribution. This paper contributes on the feasibility of TLPS as a cost-effective production strategy for high-temperature silicon and WBG power electronics. This contribution also focuses on the usage of Cu-Sn preforms as die-attach material. The optimised temperature profiles by combination of reducing and inert gases for void-free TLPS interconnect are introduced. Three phase rectifier bridge modules were constructed to check the feasibility of TLPS in serial production. The variation of intermetallic phase (IMP) formations in Cu-Sn and Cu-Sn-Ni preforms on bare and Ni-plated copper substrates, thermal treatment temperature and time are discussed. For improved handling of preforms and enhanced IMP formation, cladded Cu-Sn preforms are introduced and their characteristics are investigated. The advantages of process optimisation and its potential for flexibility and mass production are discussed.