BGA无铅焊点在跌落冲击载荷下的失效模式与机理

通过PCB组件跌落试验,探究了BGA封装的失效模式和失效机理;分析了焊球中裂纹的产生机理及扩展特点.结果表明,BGA封装失效的主要原因是焊球裂纹和PCB结构性断裂.焊球裂纹主要有两种,分别位于焊球顶部和根部,且产生机理不同.焊球顶部由于重力导致局部钎料不足而使焊球与阻焊膜之间产生间隙,进而形成裂纹;焊球根部则是由于残留助焊剂与焊球和阻焊膜之间存在间隙,在载荷作用下形成裂纹.裂纹的扩展与裂纹源的初始位置、方向及应力情况有关,焊盘与焊球的相对位置对裂纹的扩展有重要影响.

Failure mode and mechanism of BGA lead-free solder joints under drop-impact load

The failure mode and mechanism of BGA packages were explored by drop tests of PCB packages. Furthermore, the initiation mechanism and expanding features of cracks were analyzed in this work. Results showed that, cracks in the solder joints and structural fractures of PCB are the main reasons that cause the failure of BGA packages. There are two main kinds of cracks in solder joints which distribute on the joint top and bottom, and the initiation mechanism of them are different. Micro gaps between the solder joint and solder resist film that caused by gravity contribute to the cracks on the top. Cracks on the bottom are caused by the gaps on both sides of the remained solder flux that existed between the solder joint and the solder resist film under drop-impact load. The expanding of cracks has a relationship with the original location, orientation and stress conditions of the crack sources. Relative position of solder joint and pad also have important influence on the expanding of cracks.