Effect of Rapid Thermal Fatigue on Microstructure and Properties of Sn3.0Ag0.5Cu/Cu Solder Bumps

Abstract

With the size of the solder joint continues to decrease and the continuous development of high-power devices, Pb-free solder joints have experienced rapid and significant temperature different in electronic packaging. Sn3.0Ag0.5Cu solder bumps with three (φ3.7mm, φ4.3mm and φ4.7mm) size were used to conduct rapid and traditional thermal shock test, microstructure and property of solder bumps were investigated. With the application of electromagnetic induced heating and cooling circulation system, the solder bumps were rapidly heated and cooled. The results showed that the shear strength of different solder bumps size had the same change tendency after rapid thermal shock. After reflow, the shear strength of solder bumps was the highest. The shear strength of solder bumps was decreased linearly after rapid thermal shock test. Minimum shear strength almost took place at 5500 cycles in all solder bumps. With the increase of the solder ball size, the shear strength of solder bumps was 23.53 MPa, 19.08 MPa, 18.52 Mpa after 5500 rapid thermal shock cycles, the shear strength was reduced by 38.98%, 51.52% and 50.09% respectively. After rapid thermal fatigue, the shear strength had a significant downward trend than traditional thermal fatigue. After 1500 rapid thermal shock cycles, surface cracks and internal cracks of solder bumps were found. The surface of solder bumps was no cracks after traditional thermal shock. Internal cracks of solder bumps were found after 5500 traditional thermal shock cycles.