铝线楔形焊接工艺中铝屑的产生原因研究

Investigation of AL Foreign Matter during AL Wedge Bonding

铝线超声楔形焊接中易产生铝屑,这会使相邻引线搭接而产生风险,从而引起器件短路,造成器件失效。针对该问题,对铝屑产生原因进行研究,发现铝屑主要是来自两方面:一是在完成管脚位置焊接后,焊接工具后移距离的大小会影响切割铝线后线尾在劈刀楔形槽的形状,芯片键合位置处焊接前劈刀楔形槽内线尾直径的不一致(部分区域被拉伸变细)会导致在焊接过程中劈刀的楔形槽前角在变细铝线的坡度上产生纵向的摩擦,从而导致撕裂,形成侧边刺突铝屑;二是不同切刀刀锋设计会影响切槽处的铝屑堆积/撕裂状态,切槽处堆积的铝屑会被粘连到线尾,带有铝屑的线尾被焊接到芯片键合位置,从而造成芯片键合位置焊点的头部产生刺突铝屑。该研究结果可为解决铝屑问题、提高芯片封装的良品率提供理论和实践指导。

AL foreign matter is a common issue during wedge bonding,which has potential risk of short circuit resulting in the failure of device.In this study,the causes of AL foreign matter are investigated,which revealed AL foreign matter was mainly come from two causes.First cause:after the completion of bonding on lead(lead-frame),the moving distance of bonding tool affects the shape of wire tail in the groove of wedge post wire cutting,then the inconsistent diameter of wire tail in wedge groove(the front area of wire tail had been stretched and be thinned)before bonding on die can lead to the longitudinal friction between wire and the front corner of wedge groove on the slope area of thinned AL wire during wedge bonding,which can result in the wire tearing and produced AL blur along the side of Bond spot.Second cause:different cutter blade design affects the state of AL stacking/tearing at the cutting slot,which results in AL blur along the cutting slot,this AL blur can be adhered to the wire tail at the cutting slot,and then this wire tail adhered with AL blur was bonded on die pad and produced AL blur at the head of Bond spot on die pad.These study results can provide theoretical and practical guidance for solving the problem of AL foreign matter and improving the yield of Assembly packaging.