应用于功率芯片封装的瞬态液相扩散连接材料与接头可靠性研究进展

Current Research in Transient Liquid Phase Bonding Materials and Joint Reliability for Power Chip Packaging

功率半导体由于其工作电压高、电流大、放热量大等特点,已逐渐向小型化、高致密化发展。新一代宽禁带半导体器件因其优异的性能可以提高工作温度和功率密度,展现出较好的应用前景,这对与之匹配的电力封装材料提出了更高的要求。随着工作温度的不断升高,高温环境下失稳和运行环境不稳定等安全问题亟需解决,对功率半导体芯片封装接头的高温可靠性提出了更高的要求。且由于污染严重的高铅焊料不满足环保要求,高温无铅焊料的研制与对相应连接技术的研究成为当前的研究重点。瞬态液相扩散连接(Transient liquid phase bonding,TLP bonding)技术通过在低温下焊接形成耐高温金属间化合物接头,以满足“低温连接,高温服役”的要求,在新一代功率半导体的耐高温封装方面有良好的应用前景。针对TLP技术的耐高温封装材料有Sn基、In基和Bi基等。目前TLP连接材料主要有片层状、焊膏与焊片三种形态。其中片层状TLP焊料应用最早,且国内外对于其连接机理、接头性能和可靠性已有较为成熟的研究。近些年开发的基于复合粉末的焊膏与焊片形态TLP焊料具有相对较高的反应效率,但仍需大量理论与实验研究来验证其工业应用前景。本文综述了TLP连接用Sn基与In基焊料的特点,重点阐述了不同形态焊料在TLP连接机理、接头微观组织、力学性能与结构可靠性等方面的国内外研究现状及进展,并且认为接头中缺陷问题的研究以及不同服役条件下物相转化机制和接头失效机理的研究对高可靠性接头的制备具有重要意义。

Power semiconductors have gradually developed towards miniaturization and high densification due to their high working voltage,large current and large heat dissipation.The new generation of wide bandgap semiconductor devices can increase the operating temperature and power density,showing a good application prospect,which puts forward higher requirements for matching power packaging materials.With the continuous increase of operating temperature,the safety issues such as instability and unstable operating environment under high temperature need to be solved,which puts forward higher requirements for the high temperature reliability of power chip packaging.The research of lead-free solder and the corresponding joining technology is the focus of current research because high-lead solder is not environmentally friendly.Transient liquid phase bonding(TLP bonding)technology can meet the requirements of“low-temperature bonding and high-temperature ser-vice”by forming high-melting-resistant intermetallic compounds joints at low temperatures,and has good application prospects in high-temperature packaging of the new generation of power semiconductors.The high temperature resistant packaging materials for TLP bonding include Sn-based,In-based and Bi-based,etc.At present,TLP bonding materials mainly have the form of lamination,solder paste and preform.Among them,laminated solder was first applied to TLP bonding,and there have been relatively mature researches on bonding mechanism and joint performance and reliability.In recent years,solder paste and preform based on the composite powder have relatively high reaction efficiency.However,sufficient theoretical and experimental studies are needed to verify its industrial application prospects.The characteristics of Sn-based and In-based solder for TLP bonding are reviewed.The status and progress of TLP bonding mechanism,the microstructure of joints,mechanical properties and structural reliability of different solders are presented.The study for inhibition of defects in the joint,the phase transformation mechanism and failure mechanism of the joint under different service conditions will be significant in the preparation of high-reliability joints.