温度冲击下粗铝丝键合强度退化行为研究

Degradation behavior of Al wire bonding strength in thermal shock test

对大功率器件中两种直径(250μm/380μm)铝丝键合强度在温度冲击试验下的退化行为进行了研究,分析了试验后铝丝键合强度的退化情况。设置了不同的工艺参数水平,通过温度冲击试验加速键合点失效,对不同参数水平进行评估。对不同温度冲击试验条件下的退化行为进行比较。采用扫描电子显微镜对试验后脱键点的断口形貌及组织成分进行分析,分析了不同镀金层厚度对键合点强度及可靠性的影响。结果表明,两种直径铝丝均出现键合强度退化现象,厚金焊盘键合强度下降不明显,薄金焊盘在试验后出现大量键合点脱键现象,表现出较差的抗温度冲击能力。

The degradation of Al wire bonding strength in MOSFET devices under thermal shock test was investigated. In the thermal shock test,two kinds of Al wires( 250 μm/380 μm) with different packaging were studied. Degradation behaviors of the Al wire bonds during thermal shock tests were evaluated by measuring tensile stresses and comparing these values with those of the original Al wire bonds. The bonding strength degradation was compared under the different aging test. Metallographic microscope and scan electron microscope( SEM) were used to evaluate Au-Al bonding interface. The influences of the thickness and impurity of the plated gold film on the bonding reliability were investigated under the shock test. Two kinds of Al wires bonding strength were degenerated after the thermal shock test,the degradation of thick gold pad bonding strength was not obvious,some bonded lift-off phenomena occurred in the thin gold pad,which shows poor resistance to the thermal shock.