低温烧结纳米铜焊膏的制备及其连接性能分析

Preparation and connection performance analysis of solder paste by low-temperature sintering Cu nanoparticles

甲酸处理铜纳米颗粒的方法制备可低温烧结的纳米铜焊膏可用于低温连接大功率器件.首先利用改良后的多元醇法制备平均粒径为30 nm的铜纳米颗粒,然后利用甲酸浸泡去除铜纳米颗粒表面的氧化物,之后将铜纳米颗粒与乙二醇混合后制备固含量为70%的焊膏,并在160~320℃的烧结温度、10 MPa压力、保温5 min的条件下烧结连接DBC陶瓷基板和金属化的SiC芯片.结果表明,通过扫描电镜和透射电镜观察连接接头形貌,烧结接头内部烧结组织粗大,烧结铜层和铜焊盘的界面通过冶金结合紧密连接,形成了拥有高抗剪强度、高导电性的连接接头.

The Cu nanoparticles( Cu NPs) solder paste was applied to connect high-power semiconductor devices at low temperature. The preparation method of the Cu NPs solder paste included the following steps: First,Cu NPs with an average particle size of 30 nm were synthesized by the modified polyol method. Then,the Cu NPs were dispersed in formic acid to remove the surface oxide of Cu NPs. After that,the Cu NPs were mixed with ethylene glycol to prepare solder paste with a solid content of70%. The DBC ceramic substrate and the metallized SiC die was connected by sintering at low temperature from 160 ℃ to 320 ℃for 5 min,and the assist pressure was 10 MPa. The morphology of the joint was investigated by scanning electron microscopy( SEM) and transmission electron microscopy( TEM). The result showed that the connection joints with high shearing strength and conductivity were formed by metallurgical bonding between the sintered Cu NPs layer and Cu pad. Coarse microstructure was formed inside the sintered joint.