Li Yulong, Long Weifeng, Hu Xiaowu, Fu Yanshu
Key Lab of Robot & Welding Automation of Jiangxi Province, Mechanical & Electrical Engineering School, Nanchang University, Nanchang 330031, China.
State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, China.
Materials (Basel). 2018 Jan 6;11(1):84. doi: 10.3390/ma11010084.
In order to accelerate the growth of interfacial intermetallic compound (IMC) layers in a soldering structure, Cu/SAC305/Cu was first ultrasonically spot soldered and then subjected to isothermal aging. Relatively short vibration times, i.e., 400 ms and 800 ms, were used for the ultrasonic soldering. The isothermal aging was conducted at 150 °C for 0, 120, 240, and 360 h. The evolution of microstructure, the IMC layer growth mechanism during aging, and the shear strength of the joints after aging were systemically investigated. Results showed the following. (i) Formation of intermetallic compounds was accelerated by ultrasonic cavitation and streaming effects, the thickness of the interfacial Cu₆Sn₅ layer increased with aging time, and a thin Cu₃Sn layer was identified after aging for 360 h. (ii) The growth of the interfacial IMC layer of the ultrasonically soldered Cu/SAC305/Cu joints followed a linear function of the square root of the aging time, revealing a diffusion-controlled mechanism. (iii) The tensile shear strength of the joint decreased to a small extent with increasing aging time, owing to the combined effects of IMC grain coarsening and the increase of the interfacial IMC. (iv) Finally, although the fracture surfaces and failure locations of the joint soldered with 400 ms and 800 ms vibration times show similar characteristics, they are influenced by the aging time.
为了加速焊接结构中界面金属间化合物（IMC）层的生长，首先对Cu/SAC305/Cu进行超声点焊，然后进行等温时效处理。超声焊接采用相对较短的振动时间，即400 ms和800 ms。等温时效在150℃下进行0、120、240和360 h。系统研究了微观结构的演变、时效过程中IMC层的生长机制以及时效后接头的剪切强度。结果如下：（i）超声空化和流效应加速了金属间化合物的形成，界面Cu₆Sn₅层的厚度随时效时间增加，时效360 h后鉴定出薄的Cu₃Sn层。（ii）超声焊接的Cu/SAC305/Cu接头界面IMC层的生长遵循时效时间平方根的线性函数，揭示了扩散控制机制。（iii）由于IMC晶粒粗化和界面IMC增加的综合作用，接头的拉伸剪切强度随时效时间增加略有下降。（iv）最后，尽管振动时间为400 ms和800 ms的接头的断裂表面和失效位置显示出相似的特征，但它们受时效时间的影响。
