Microstructure and Shear Strength of Low-Silver SAC/Cu Solder Joints during Aging

Abstract

A new type of low-silver hypoeutectic SAC lead-free solder was prepared, and then hot dip soldering was used to form the joints of copper. The microstructure evolution of IMCs and the variation of shear strength of solder joints were investigated. The results have shown that the thickness of the IMC layer increased over time and the scallop-type IMC became a hump like shape during the aging process. The growth rates of the IMC layer were 0.61 × 10 −14 cm 2 /s, 2.06 × 10 −14 cm 2 /s, 4.83 × 10 −14 cm 2 /s at 348 K, 373 K and 423 K respectively. The shear strength of solder joint fell sharply at rst and then became slow, nally dropped from 40.94 MPa to 29.73 MPa after aging at 423 K for 12 days. Moreover, the fracture mode changed from ductile fracture to local brittle fracture with the increasing of aging time.

Thermal aging effects on the properties of the Cu/(SAC0307 powder + Zn-particles)/Cu joint ultrasonic-assisted soldered at low-temperature

“…During the aging process, the growth rate of IMCs is mainly controlled by the diffusion rate of atoms because the mutual diffusion rate between Cu and solder is lower. The IMCs thickness will be proportional to the square root of the aging time (Gan et al , 2013a, Luo et al , 2016). During the process of aging, the relationship between the IMCs thickness and time is as follows (Zhang et al , 2012): where d is the IMCs thickness,μm; d 0 is the thickness of the IMCs in the as-received joints, μm; K is the growth rate, cm 2 /s; and t is the aging time, s.…”