New Cu paste with high bonding strength—Nano composite alloy particles synthesized by nanomized method

In the metallization technology for crystalline Si solar cell, it has been required to develop new material with low cost for high-temperature and highly-reliable interconnection. We have developed new method to fabricate fine metal alloy particles with narrow distribution of particle size from 0.5 to 10μm. We called it as Nanomized method. The fine particles are composed of uniform structure dispersed metal alloy in nano-scale level and do not include void in the particle. The metal alloy particles fabricated by conventional atomized method include void inside particle and non-uniformly dispersed alloy components. We confirmed reliability and mechanical strength. We produced bonding material from the mixture of Cu particles and Sn-based alloy particles. The bonding strength of die chip on Al electrode reached 80 MPa as a top data, 50 MPa in average. The bonding strength of Sn-based alloy particle fabricated from conventional atomized method deteriorated less than 8 MPa after 500 hours later at 300 degree C.