电子装联常用焊料极限低温力学性能分析

Analysis of Extreme Low Temperature Mechanical Properties of Common Solder Used in Electronic Assembly

Sn63Pb37、Sn62Pb36Ag2、In50Pb50、Pb88Sn10Ag2焊料在不同温度下进行拉伸试验,应变速率10-3/s。在室温下,Sn62Pb36Ag2焊料的拉伸断裂强度最高,为48.2 MPa。随着温度下降,Sn63Pb37、Sn62Pb36Ag2两种焊料的断裂强度先升高后下降;In50Pb50、Pb88Sn10Ag2两种焊料的拉伸断裂强度则随温度下降一直升高,不存在强度下降的拐点。在-150℃、-196℃,Sn63Pb37和Sn62Pb36Ag2焊料拉伸断裂的应力—应变曲线先后发生显著改变,表明在该温度下其拉伸断裂模式已经转变为脆性断裂,而In50Pb50、Pb88Sn10Ag2焊料在-196℃～室温范围内一直保持为韧性断裂。从试验件断口的扫描电镜照片来看,随着温度下降Sn63Pb37、Sn62Pb36Ag2焊料的断口韧窝逐渐减小,并最终演化为脆性断裂。In50Pb50、Pb88Sn10Ag2的拉伸断口形貌则基本保持不变。

Tensile tests of Sn63Pb37, Sn62Pb36Ag2, In50Pb50 and Pb88Sn10Ag2 were carried out at different temperatures, strain rates is 10-3/s. The tensile fracture strength of Sn62Pb36Ag2 is the highest at room temperature, 48.2 MPa. With the decrease of temperature, the fracture strength of Sn63Pb37 and Sn62Pb36Ag2 first increases and then decreases. The tensile fracture strength of In50Pb50 and Pb88Sn10Ag2 increases with the decrease of temperature, and there is no inflection point for the decrease of strength. The stress-strain curves of tensile fracture of Sn63Pb37 and Sn62Pb36Ag2 have changed significantly at -150 ℃ and -196 ℃, indicating that the tensile fracture mode of Sn63Pb37 and Sn62Pb36Ag2 has changed to brittle fracture at this temperature, while In50Pb50 and Pb88Sn10Ag2 have remained ductile fracture from -196 ℃ to room temperature. The SEM photos of the fracture section of the test piece indicate that the fracture dimples of Sn63Pb37 and Sn62Pb36Ag2 gradually decrease with the decrease of temperature, and eventually evolve into brittle fracture. The tensile fracture morphology of In50Pb50 and Pb88Sn10Ag2 remained basically unchanged.