激光加热条件下SnPb共晶钎料与Au/Ni/Cu焊盘界面反应动力学

Reaction kinetics between SnPb eutectic solder and Au/Ni/Cu pad during laser reflow

激光重熔在电子封装领域中SnPb共晶钎料凸点制作方面存在极大的优势.采用扫描电子显微镜(SEM)分析了激光加热条件下SnPb共晶钎料与Au/Ni/Cu焊盘之间的界面反应,探讨了钎料与Au/Ni/Cu界面处金属间化合物的形成机理,并采用数值模拟的方法计算了Au镀层在激光加热过程中向钎料中的溶解与扩散动力学.结果表明:SnPb共晶钎料在激光加热瞬间与Au/Ni/Cu焊盘中的Au发生反应,生成Au-Sn金属间化合物,其形貌和分布与激光输入能量密切相关;随着激光输入能量的增加,Au-Sn化合物由连续层状转变为针状,最后以细小颗粒弥散分布在钎料内部.

Laser reflow is a potential technique in bumping of SnPb eutecti c solder in electronic packaging area.Scanning Electron Microscopy(SEM)was used to analyze the interfacial reaction between63Sn37Pb and Au/Ni /Cu pad durin g laser reflow.In addition,the kinetics of Au layer dissolution and diffusion into the solder during laser heating was modeled numerically to elucidate the fo rmation mechanism of intermetallic phase at the solder/Au pad interface.Results showed that the63Sn37Pb solder reacted with the Au layer in Au/Ni /Cu pad t o form Au-Sn intermetallics soon after the solder was melted by the laser,and the morphology and distri-bution of intermetallic compounds at interface was st rongly influenced by laser input energy.With the increase of laser input ener gy,the Au-Sn intermetallics changed from the continuous layer into needle-lik e particles.Finally,AuSn 4 disappeared at the interface,distributing evenly inside the solder as small particles.