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在Sn-5.0X-1.5Cu-Ni焊料合金中添加10%(质量分数,下同)的Bi,以期降低焊料熔点的同时消除Bi的偏析和合金脆性,研究了浇铸空冷和真空吸铸水冷两种不同冷却速度下无铅焊料合金的微观组织。用X射线衍射分析的方法,按最小二乘法原理,精确测定β-Sn的点阵参数,对Sn-10Bi-5.0X-1.5Cu-Ni合金的固溶度进行了测定;采用光学显微镜、扫描电镜和透视电镜观察合金微观组织和结构;通过DSC分析焊料的熔化和凝固过程;并测试了焊料的润湿性和力学性能。结果表明:随着凝固速度增加,晶格常数进一步增大,Bi在Sn中的固溶度也得到了提高;缓慢冷却的浇铸态合金显微组织中存在着大量的粗大针状Sn-Bi共晶组织,吸铸态合金组织中Bi以细小颗粒状均匀分布在Sn基体,没有偏析相形成,吸铸快冷条件下制备的Sn-10Bi-5.0X-1.5Cu-Ni的熔点为208.96℃,具有优良的润湿性,合金和焊点具有良好的力学性能。
In the Sn-5.0X-1.5Cu-Ni solder alloy 10% (mass fraction, the same below) of Bi, in order to reduce the melting point of the solder while eliminating Bi segregation and alloy brittleness, casting and air-cooled vacuum suction two Microstructure of Lead-free Solder Alloy at Different Cooling Rates. The solid solubility of Sn-10Bi-5.0X-1.5Cu-Ni alloy was measured by X-ray diffraction method and the lattice parameters of β-Sn were measured accurately by the principle of least square method. The microstructure and microstructure of the alloy were observed by SEM and TEM. The melting and solidification process of the solder was analyzed by DSC. The wettability and mechanical properties of the solder were also tested. The results show that as the solidification rate increases, the lattice constant increases further, and the solid solubility of Bi in Sn increases. In the slowly cooled cast alloy, a large amount of coarse Sn-Bi In the as-cast and as-cast alloy, Bi is uniformly distributed in the Sn matrix with fine particles and no segregation phase is formed. The melting point of Sn-10Bi-5.0X-1.5Cu-Ni prepared by rapid cooling is 208.96 ℃, Has excellent wetting, alloys and solder joints have good mechanical properties.