Interface Fracture Toughness Assessment of Solder Joints Using Double Cantilever Beam Test

Abstract

In the current work, a test scheme to evaluate solder joint interface fracture toughness using double cantilever beam (DCB) test has been successfully demonstrated. The obtained results, in terms of critical energy release rate, predict the joint failure based on the principle of fracture mechanics. The results can be used as a materials property in the reliability design of various types of solder-ball joined packages. DCB specimens made of 99.9 wt% copper were selected in the current work. Eutectic Sn-37Pb and lead-free Sn-3.5Ag-0.5Cu solders were used to join two pieces of the copper beams with controlled solder thickness. The test record showed steady propagation of the crack along the solder / copper interface, which verifies the viability of such a testing scheme. Interface fracture toughness for as-joined, extensively-reflowed and thermally aged samples has been measured. Both the reflow treatment and the thermal aging lead to degradation of the solder joint fracture resistance. Reflow treatment was more damaging as it induces much faster interface reaction. Fractographic analysis established that the fracture has a mixed micromechanism of dimple and cleavage. The dimples are formed as a result of the separation between the hard intermetallic compound (IMC) particles and the soft solder material, while the cleavage is formed by the brittle split of the IMCs. When the IMC thickness is increased due to extended interface reaction, the proportion of IMC cleavage failure increases, and this was reflected in the decrease of the critical energy release rate.

Comparison of solder joint fracture behavior in Arcan and DCB specimens

“…For example, DCB specimens were used to measure the mode I critical strain energy release rate, G Ic , of 1 mm thick Sn-37Pb and SAC305 solders forming continuous joints between two copper substrates with cross-sections of 5 Â 5 mm [1]. The cross-head speed was 1 mm/min with a moment arm of 20 mm from the loading pins to the start of the solder which was tapered to form a chevron notch for crack initiation.…”

Characteristics of Cracking Failure in Microbump Joints for 3D Chip-on-Chip Interconnections under Drop Impact

“…is the fracture toughness of the solder, and Γ i is the fracture toughness of Ni 3 Sn 4 IMC. In this paper, the maximum fracture toughness of solder SAC305 is set to be 295 N/m, which is measured by Loo [16]. To be able to directly compare the fracture toughness values of the Ni-Sn-IMC interface from the various existing research, the fracture toughness is converted into a critical stress intensity factor.…”

Evaluation of interfacial toughness function in mixed mode loading

“…Many methods have been proposed to evaluate the interfacial fracture criteria such as the peeling test [1,2], the four-point bending test [3], the sandwiched cantilever test [4] and the double cantilever beam test [5]. However, the mentioned methods can not control the mix of loading, and only can calibrate the interfacial fracture criteria at pure mode I and some combinations of mode I and mode II.…”