超声作用下Ni/Sn/Ni钎焊界面金属间化合物的演变

对比研究了超声作用和无超声作用下Ni/Sn/Ni钎焊界面金属间化合物的形成和演变规律。结果表明,无超声作用时,Ni/Ni_3Sn_4界面较为平直且致密,而Sn/Ni_3Sn_4界面被液态Sn钎料逐渐溶解而呈扇贝状,并且有少量Ni_3Sn_4分布在焊缝中。其次,界面金属间化合物(intermetallic compound, IMC)层厚度与时间呈抛物线关系,Ni_3Sn_4的生长受体扩散的控制。超声作用下,声空蚀作用使得界面Ni_3Sn_4发生溶解而形成很多沟槽,甚至在界面IMC的局部区域出现了"neck"状连接,重新为母材Ni原子向钎料的溶解打开了通道,在声流的辅助作用下促进母材的溶解。随着超声时间的增加,声空化作用将界面"neck"状连接的细长的Ni_3Sn_4晶粒打碎而进入焊缝,使得界面IMC逐渐减薄。进入焊缝的Ni_3Sn_4进一步在空化作用下溶解和破碎,最终大量细小的Ni_3Sn_4均匀分布在焊缝中。

IMC growth at Ni/liquid Sn interface under ultrasonic treatment

The paper investigated the formation and evolution of intermetallic compound at the interface of Ni/Sn with and without USV. Without ultrasonic treatment, the IMC layer are plain and compact at the interface of Ni/Ni₃Sn₄. Towards the solder side, Sn tends to wet and penetrate the grain boundaries to form the scallop-type Ni₃Sn₄. Moreover, intermetallic grains grow with a 1/2 power dependence on time, the growth was controlled by the bulk diffusion. With ultrasonic treatment, acoustic cavitation causes the interfacial Ni₃Sn₄to dissolve and forms many grooves, even forms is reopened and ultrasonic streaming promotes this dissolution. With prolong of ultrasonic time, elongated Ni₃Sn₄grains which was "neck" connection are broken up by the ultrasonic cavitation and fall into the liquid solder. Interfacial IMC was gradually reduction. The Ni₃Sn₄ grains falling into the liquid are further dissolved and broken by ultrasonic cavitation. Finally many fine Ni₃Sn₄ grains are evenly distributed in the joint.