OSP和Im-Sn镀层对Sn10Sb焊点微观结构和高速剪切性能的影响

Effects of OSP and Im-Sn surface-finished substrates on microstructure and high speed shear performance of Sn10Sb solder joints

Sn10Sb合金具有优良的热疲劳性能和相对较高的断裂强度,在对耐热疲劳有要求的细分市场中已得到广泛应用,但其焊点在不同焊盘镀层下的高速剪切性能仍缺少研究。为此,研究了有机可焊防护剂(OSP)和化学沉锡(Im-Sn)两种镀层对Sn10Sb(Sb的质量分数为10%)焊点在1000 mm/s剪切速率下力学性能的影响。研究结果表明,相比于Sn10Sb块体合金,20~40μm的Sn-Sb化合物均匀分散在β-Sn基体中,而焊点由于熔化和凝固过程中热场不均匀导致Sn-Sb化合物大部分偏聚在表面上、少数聚集在其内部和界面,通过Ansys有限元模拟焊点升降温过程中的热场不均匀分布对该现象进行了解释。此外,利用扫描电子显微镜(SEM)和能量色散X射线光谱仪(EDS)对焊点进行观察,发现两种镀层的焊点都由β-Sn基体、SnSb化合物和Cu6Sn5化合物组成。相比于Sn10Sb/OSP焊点,由于Sn10Sb/Im-Sn焊点基体内部有更多的SnSb化合物形成且界面处的Cu6Sn5层更薄,使得Sn10Sb/Im-Sn焊点的剪切强度更高但是塑性变差,导致其剪切能更低。该研究为了解Sn10Sb焊点的高速变形和断裂提供了理论支撑。

The Sn10Sb alloy,with excellent thermal fatigue properties and relatively high fracture strength,has been widely used in market segments requiring heat fatigue resistance,but the highspeed shear performance of its solder joints under different surface-finished substrates is still lacking in research.The effects of organic solderability preservatives(OSP)and immersion-Sn(Im-Sn)surface-finished substrates on the mechanical properties of Sn10Sb(mass fraction of Sb is 10%)solder joints at shear rate of 1000 mm/s were studied.The results show that compared with Sn10Sb bulk alloy,Sn-Sb compounds of 20-40μm are uniformly dispersed inβ-Sn matrix.Due to the uneven thermal field during melting and solidification,the coarse Sn-Sb compounds with the same size are most isolated on the surface,while a few of them gather in the interior and interface of solder joints,which can be explained by uneven distributed thermal field during heating and cooling process using Ansys finite element simulation.In addition,scanning electron microscope(SEM)and energy dispersive X-ray spectroscopy(EDS)were used to observe the solder joints,and it was found that the solder joints of two kinds of surface-finished substrates were both composed ofβ-Sn matrix,SnSb compounds and Cu6Sn5compounds.Compared with the microstructure of Sn10Sb/OSP solder joints,Sn10Sb/Im-Sn solder joints have more SnSb compounds and the interface Cu6Sn5 is thinner.This leads to higher shear strength but lower ductility of Sn10Sb/Im-Sn solder joints,resulting in lower shear energy.This study provides a theoretical support for the effects of OSP and Im-Sn surface-finished substrates on microstructure and high-speed shear performance of Sn10Sb solder joints.