Influence of reflow and thermal aging on the shear strength and fracture behavior of Sn-3.5Ag solder/Cu joints

Abstract

The mechanical behavior of Sn-rich solder/Cu joints is highly sensitive to processing variables such as solder reflow time, cooling rate, and subsequent thermal aging. In this article, we focus on the lap shear behavior of Sn-3.5Ag/Cu joints as a function of solder yield strength and intermetallic thickness. Experimental results showed that the shear strength of the solder joints is primarily controlled by the mechanical properties of the solder, and not the intermetallic thickness. The thickness of intermetallic, however, controlled the fracture mode of the solder joints. At intermetallic thicknesses greater than 20 m, brittle fracture between Cu 6 Sn 5 and Cu 3 Sn was the most common failure mechanism. Finite-element simulations were carried out to evaluate the effect of solder properties and of intermetallic thickness and morphology on lap shear behavior. The finite-element simulations corroborated the experimental findings, i.e., that increased solder strength results in increased joint strength. The simulations also showed that thicker intermetallics, especially of nodular morphology, yielded higher local plastic shear strain and work hardening rate.

Microstructure and mechanical behavior of novel rare earth-containing Pb-Free solders

“…The joint was assembled with the aid of a reflow fixture, to minimize misalignment and maintain a consistent joint solder thickness of approximately 500 mm. 25 The entire assembly was heated on a hot plate and held at 120°C for 20 min. to allow excess flux to vaporize.…”

Incorporation of Interfacial Intermetallic Morphology in Fracture Mechanism Map for Sn-Ag-Cu Solder Joints

“…4,12,15 These strain concentrations arise due to misfit strains induced via elastic-plastic mismatch between the solder and the IMC layer. 10,12,13 In addition, strain localization within the solder immediately adjacent to and parallel to the interface can cause stress concentrations in the scallops, enhancing the propensity for IMC fracture.…”

Simulation Analysis and Experimental Study on Strength Optimization of a Plug‐In Oil Hose Joint

“…Deng et al focused on the lap shear behavior of Sn-3.5Ag/Cu joints as a function of solder yield strength and intermetallic thickness. eir experimental results showed that the shear strength of the solder joints is primarily controlled by the mechanical properties of the solder and not by the intermetallic thickness [14]. Lee and Lee investigated composite lead-free solders fabricated by adding between 0.5 and 3 wt.% of Ni particles in situ to Sn-3.5 wt.% Ag lead-free solder and found that the single lap shear strength of the joints increases with increasing Ni addition in the as-reflowed condition but decreases with increasing storage time in the aged specimens [15].…”