超声作用下Ni/Sn/Ni钎焊界面金属间化合物的演变

Intermetallic Compound(IMC)Growth at Ni/Sn/Ni Interface Under Ultrasonic Treatment

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/Ni3Sn4界面较为平直且致密,而Sn/Ni3Sn4界面被液态Sn钎料逐渐溶解而呈扇贝状,并且有少量Ni3Sn4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,Ni3Sn4的生长受体扩散的控制。超声作用下,声空蚀作用使得界面Ni3Sn4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Ni3Sn4晶粒打碎而进入焊缝,使得界面IMC逐渐减薄。进入焊缝的Ni3Sn4进一步在空化作用下溶解和破碎,最终大量细小的Ni3Sn4均匀分布在焊缝中。

The formation and evolution of intermetallic compound(IMC)at the interface of Ni/Sn/Ni with and without ultrasonic wave(USV)were investigated.The results show that without ultrasonic treatment,the IMC layer is 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,and the growth is controlled by the bulk diffusion.With ultrasonic treatment,acoustic cavitation causes the interfacial Ni3Sn4 to dissolve and form many grooves,even forms"neck"connection in the local area of the interfacial IMC.Therefore,the dissolution passage of the Ni atom to the solder is reopened and ultrasonic streaming promotes this dissolution.With the prolonging of ultrasonic time,elongated Ni3Sn4 grains which are of"neck"connection are broken up by the ultrasonic cavitation and fall into the liquid solder.Thus the interfacial IMC is gradually reduced.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.