冷却速度对Sn-Pb钎料合金组织和性能的影响

Effect of Cooling Speed on Microstructure and Mechanical Property of Sn-Pb Solder Alloy

采用扫描电镜和微型拉伸试验机,研究了冷却速度对Sn-Pb钎料合金组织和性能的影响。为了得到不同冷却速度下的Sn-Pb合金,将Sn-Pb合金在300℃下熔化,分别直接在25、50、100和150℃的重油中冷却成固态。研究结果表明:冷却速度越小,Sn-Pb钎料合金的组织越大,当钎料合金在25℃重油中冷却时,钎料合金富Pb相的大小为8.7μm,而当钎料合金在150℃重油中冷却时,钎料合金富Pb相的大小为22.2μm;冷却速度越小钎料合金的强度越高,当钎料合金在25℃重油中冷却时,钎料合金的抗拉强度为26.36 MPa,而当钎料合金在150℃重油中冷却时,钎料合金的抗拉强度为31.84 MPa;钎料合金拉伸断口均表现为韧窝结构,韧窝大小随着冷却速度的降低而逐渐增大。

The effects of cooling speeds on the microstructure and mechanical property of Sn-Pb solder alloy were investigated by scanning electron microscopes and micro tensile tester. To obtain the Sn-Pb solder alloy under different cooling speed, the Sn-Pb solder alloy, which was heated to 300 ℃, is cooled in heavy oil at 25 ℃, 50 ℃, 100 ℃, and 150 ℃. The results show that the larger the cooling speed is, the tinier the microstructure is. When the solder alloy is directly cooled to 25 ℃ from 300 ℃ in heavy oil, the size of Pb-rich phase is 8.7 μm. When it is cooled to 150 ℃ directly in heavy oil, the size of Pb-rich phase is 22.2 μm. The better mechanical property can be obtained in the Sn-Pb solder alloy with a higher cooling temperature. When the solder alloy is directly cooled to 25 ℃ from 300 ℃ in heavy oil, the ultimate tensile strength is 26.36 MPa. However, when it is cooled to 150 ℃ in heavy oil directly, the ultimate tensile strength is 31.84 MPa. There are many dimples on the fracture surface of tensile samples. The size of dimple increases as the cooling temperature rises.