SnPb钎料熔滴与Au/Ni/Cu焊盘的反应过程

Interfacial reaction between molten 63Sn37Pb droplet and Au/Ni/Cu pad

研究了熔融的SnPb钎料由固定高度滴落到Au/Ni/Cu焊盘上的温度变化过程和界面反应情况。结果表明:对钎料熔滴到达焊盘瞬时的接触温度,熔滴初始温度是其主要影响因素,而高度变化对其影响不大。钎料与焊盘界面产生的金属间化合物形态受钎料熔滴初始温度影响很大。随着滴落钎料初始温度的提高,界面层由Au层基本不反应,变为形成了连续层状AuSn2及针状AuSn4。当初始温度升高到450℃时,AuSn2完全转化为AuSn4,棒状AuSn4生长极为明显,在离界面不远的钎料里发现细小的AuSn4。由计算推出界面反应的时间约为6～7ms,在如此短的时间内,发生Au的溶解和Au Sn化合物的形成,其原因在于Au在熔融钎料中溶解速度随温度变化的特殊性。

Temperature variation of solder droplet, interfacial reaction between molten SnPb droplet and Au/Ni/Cu pad were investigated. The 63Sn37Pb solder ball was heated to the specific temperature above melting point and then dropped to the pad from a certain height. The results show that the instantaneous temperature of solder droplet when it reached the pad is mainly determined by the initial temperature. The morphology of intermetallic compounds is strongly influenced by initial temperature of solder droplet. With the increasing initial temperature, a continuous AuSn_2 and needle-like AuSn_4 formed at the interface. When the temperature reached 450 ℃, all AuSn_2 converted into AuSn_4. Rod-like AuSn_4 grew strongly, some tiny AuSn_4 distributed inside the solder near the interface. The interfacial reaction time is about 6～7 ms, during which Au is quickly dissolved into molten solder forming Au-Sn intermetallic compounds. This process attributed to the discontinuity in the dependence of the dissolution rate of gold on temperature in molten eutectic SnPb solder.