Comparing the solderability of different SAC0307 composite solder pastes

In the present study, the effect of four oxide ceramics (TiO2, ZnO, ZrO2, and CuO) as reinforcements was investigated on the soldering parameters of the SAC0307 solder alloy. The oxide ceramics were used in nano-powder format. Composite solder pastes were composed by the standard ball milling process of the nano-particles into the SAC0307 solder paste in 0.25wt% weight fraction. The primary particle sizes of the NPs were the following: 21nm - TiO2, <50nm - ZnO, <100nm ZrO2, and <50nm CuO. The NPs were homogeneously mixed into the SAC0307 solder paste by a YX paste mixer with 400rpm for 12 mins. The wettability, shear strength, and microstructure of the composite solder joints were studied and compared. The first investigation was the spreading test to study the wetting properties of the solder alloys (Tab. 1). Test surfaces (50x50mm) were prepared on FR4 substrates with Cu wiring with imm-Ag surface finishing. On each test boards four circular solder deposits were screen printed with 5mm diameter and 125 µm thickness. The solder pastes were reflowed in a vapour phase soldering (VPS) oven. The wetted surface area was measured by an Olympus BX50 optical-microscope. During the second experiment, solder joints were fabricated by SMT on one-layer standard FR4 PCBs with Cu wiring. A DAGE 2400 shear tester has been used to measure the shear force of the solder joints. Metallographic cross-sections were also prepared from the solder joints to compare their microstructures. The metallogrpahic cross-sections were investigated with an FEI Inspect-S50 SEM.The results showed that the ceramic nano-particles did not have a major effect on the wettability of the solder. Shear strength increases were observed at the composite joints, except in the case of ZnO. Generally, Sn grain refinement was found in the Sn-matrix which could be the reason for the shear strength increase.The dataset consists of supplementary SEM micrographs of the cross-sectioned solder joints.