Hybrid Cu particle paste with surface-modified particles for high temperature electronics packaging

Die-attach bonding is a key process to realize high-temperature operation of power semiconductor devices. Ag sintering has been in the forefront of the research in the past decade as a suitable alternative to high temperature solders such as AuSn. However, the high cost of Ag and low electromigration resistance have been deterrants to large scale industrialization. Cu is ~100 times cheaper than Ag and more abundantly available. It is easy to process and recycle and displays mechanical, thermal and electrical properties comparable with Ag. In this contribution, the research is focused on developing Cu sintering as an alternative to Ag sintering. Different sintering pastes have been prepared in-house by combining Cu particles in micro and/or nano-scale with polyethylene glycol 600 (PEG600). The performances of the pastes have been analysed and evaluated under different bonding conditions. Shear strengths of approximately 88MPa has been achieved while working with a combination of surface modified Cu-alloy particles and PEG600 as binder. Surface modifications on the Cu-alloy particles are obtained through a selective etching of the alloying element. Sintering was performed under a bonding pressure of 20MPa, at 275°C, for 30min, under N ₂ . comparison with hybrid Cu particle paste under the same experimental conditions, the result is very promising and better by a factor 2.