Influence of Artificial Aging on Microstructures and Properties of Plane Contact Type Cu/Al Terminal Connectors

Plane contact type Cu/Al terminal connectors were produced through an ultrasonic dip soldering technique. Microstructure evolution and its effect on the bonding strength and electrical property of the connectors were studied after the connectors aged at 150 ℃ for times till 720 h. The results showed that during aging the connectors, an intermetallic (IMC) layer of Cu6Sn5 and Cu3Sn was formed at the interface between the Cu terminal and the Sn-Pb alloy solder. Meanwhile, a Pb-rich layer in the Sn-Pb solder adjacent to the IMC layer was also formed. The IMC layer followed a parabolic growth kinetics with a growth rate constant, k=3.5×10-17 m2/s. Compared with the connectors without aging, the shear strength of the connectors aged at 150 ℃ for 720 h decreased about 20%. The fracture of the connectors also changed from the toughness fracture through the Sn-Pb solder to the brittle fracture through the Pb-rich layer. Moreover, the electrical resistivity of the connectors also increased obviously after aging.