回流温度对单板/板级BGA无铅焊点的剪切力学行为影响

采用试验的方法研究回流温度对Sn3.0Ag0.5Cu，Sn0.3Ag0.7Cu，Sn0.3Ag0.7Cu-0.07La-0.05Ce三种无铅钎料在单板结构/板级结构中剪切性能的影响.结果表明，随着回流温度的升高，单板结构中高银焊点的抗剪强度最高且一直增加，低银焊点呈现出先增加后降低的趋势.板级结构中焊点的抗剪强度均随回流温度的升高呈现出先增加后降低的趋势，其中添加稀土元素的低银焊点的抗剪强度最高.两种结构中焊点的至断位移均随回流温度的升高而降低.板级结构中，随着回流温度的升高，高银焊点的断裂模式由韧性断裂向脆性断裂转变，而低银焊点则一直为韧性断裂，其断裂位置向IMC方向移动.

Effect of reflow temperature on the shear behavior of BGA solder joints under veneer structure and board-level structure

The influence of reflow temperature on the shear mechanical properties of three kinds of solders(Sn3.0Ag0.5Cu, Sn0.3Ag0.7Cu and Sn0.3Ag0.7Cu-0.07La-0.05Ce) under veneer structure and board-level structure was studied by shear experiments. Results shown that the shear strength of the high silver solder joints under veneer structure increased with the increase of reflow temperature, while the shear strength of the low silver solder joints under veneer structure increased firstly and then decreased with the increase of reflow temperature. The shear strength of solder joints under board -level structure increased first and then decrease with the increase of reflow temperature, and the shear strength of low silver solder joints with rare earth elements was the highest. The fracture displacement of solder joints under veneer structure and board-level structure decreased with the increase of reflow temperature. The fracture mode of high silver solder joints under board-level structure are changed from ductile fracture to brittle fracture with the increase of reflow temperature. The fracture mode of low silver solder joints under board-level structure always were ductile fractures with the increase of reflow temperature. The fracture position of low silver solder joints under board-level structure shifted to the direction of the IMC with the increase of reflow temperature.