QFN器件在湿热环境中的界面裂纹分析

Analysis of the interface crack for QFN devices in hygro-thermal ambient

因吸潮而引起的界面破裂是塑封电子器件失效的一个重要原因。通过吸潮实验、无铅回流焊环境实验和湿热老化实验研究了QFN塑封器件内部界面裂纹情况。结果表明,未吸潮的器件经历无铅回流焊后很少产生裂纹,吸潮器件在吸潮期间未产生裂纹,但经历无铅回流焊后器件产生裂纹的几率达100%;裂纹在芯片、芯片粘结材料(DA)和塑封材料(EMC)的交界处的破坏程度最大;产生的裂纹的位置和扩展方向与结合材料的特性、结合界面的强度紧密相关。

The interface crack caused by the moisture absorption is an important reason for plastic packaging electronic devices failure. The interface cracks in the QFN plastic packaging devices were studied through moisture absorption experiments, lead-free reflow soldering experiments, hygro-thermal aging experiments and scanning electron microscopy examination. The results show that there are seldom cracks in the devices without moisture absorption after the lead-free reflow soldering, but all of the moisture absorption devices are cracked after the lead-free reflow soldering but no crack during the moisture absorption process; the juncture of chip, die adhesive （DA） material and epoxy molding compound （EMC） material has the greatest damage; the position and the growing direction of cracks are closely related to the characteristic of the bonding materials and the intensity of the bonding interface.