Tensile and Fatigue Behaviors of Aged Cu/Sn-4Ag Solder Joints

Abstract

Tensile properties and stress-controlled fatigue fracture behaviors of Cu/Sn-4Ag solder joints aged at 180°C for different times were systematically investigated. It was found that the tensile strength of the solder joints decreased with increasing aging time and that the fracture mode changed from ductile to brittle. The fatigue life of the solder joints also decreased with increasing aging time. For most of the solder joints, fatigue cracks tended to initiate around the Cu/Cu 6 Sn 5 interfaces due to the strain incompatibility and local strain concentration on a micro-scale, and they then propagated within the solder proximately along the Cu/Cu 6 Sn 5 interfaces. The samples aged for different times or tested under different stress amplitudes had similar fractography morphologies, which consisted mainly of a propagation region, covered by solder, and a final fracture region. Based on the experimental observations above, the corresponding interfacial fatigue failure mechanisms were discussed in terms of different influencing factors.

In situ synthesis of high strength Ag brazing filler metals during induction brazing process

“…For the Ag29Cu28Zn43/316LN joint, the yield strength is about 400 MPa, and the plastic deformation is quite high after yield. Similar tensile curve has been observed in the Sn-Ag/Cu solder, when the yield strength of the Cu substrate is lower than the Sn-4Ag solder [12]. Since the brazing seam is very thin, deformation of the sample is mainly contributed by deformation of the 316LN substrate, indicating that the 316LN stainless steel yields at about 400 MPa.…”

Mechanical properties of intermetallic compounds in solder joints

“…Samples used for tensile tests generally are in sandwich structure as Cu/IMC/solder/IMC/Cu. Shape of the sample can be round bar [22][23][24] or thin rectangular dog-bone [25,26]. Ju Guokui [24] studied the tensile fracture behavior and the intermetallic compounds morphology and composition at the interface of Cu/Sn3.0Ag0.5Cu solder joints after aging at 150 ℃ .…”

“…The morphology of fracture surface changes from dimple-like to cleavage-like surfaces. Lee [26] focused upon the interrelationships of tensile strength, fracture morphology and IMC thickness. IMC thickness and interface roughness have a significant impact on the tensile strength and fracture morphology.…”

“…Properties such as Young's modulus and Hardness are mostly measured, but have a great dispersion [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Tensile strength [22][23][24][25][26][27] and shear strength [28][29][30][31][32][33][34][35] are tested to identify the relationship between those strength and aging times.…”

Micro-mechanical and fracture characteristics of Cu 6 Sn 5 and Cu 3 Sn intermetallic compounds under micro-cantilever bending

“…elastic modulus and coefficient of thermal expansion) with solders and substrates [4,[8][9][10]. With an increasing trend towards miniaturization of microelectronic products, volume ratio of the IMCs in solder joints tends to be higher, which affects their mechanical integrity significantly [11,12].…”