细间距器件无铅焊点力学性能和断口形貌分析

分别采取红外再流焊和激光再流焊焊接细间距器件，研究了SnPb，SnAgCu和SnAg三种钎料在不同焊接热源下焊点的力学性能。结果表明，激光再流焊对应焊点的力学性能优于红外再流焊，该现象在使用SnAg钎料的情况下尤为显著，同时无铅焊点优于传统的SnPb焊点。对焊点断口形貌进行研究，发现激光焊接的条件下，焊点断口韧窝较多、较深，断口的撕裂棱朝固定的方向延伸，而红外热源焊接的条件下，断口韧窝较少，较浅，两种情况下焊点韧窝开裂均为穿晶开裂。

Investigation of mechanical property and fracture morphology of lead-free soldered joints of fine pitch devices

Soldering experiments of fine pitch devices were carried out using diode-laser soldering sy stem and IR reflow soldering with SnPb, SnAgCu, SnAg, and the tensile strengths of soldered joints were measured by Micro-joints Tester.The results indicate that mechanical properties of fine pitch devices soldered joints with laser soldering system is better than that of fine pitch devices soldered joints with IR reflow soldering method, especially for SnAg soldered joints, and the mechanical properties of lead-free soldered joints is also better than that of Sn-Pb solder.The characteristics of fracture morphology of micro-joints were also analyzed by SEM.It is found that the fracture mechanism of micro-joints soldered with laser soldering system is toughness fracture, and mangled edges appear in a fixed direction.While the fracture morphology of micro-joints soldered with IR reflow soldering method has less and lower dimples than that with diode-laser soldering system.Both the dimple crack mechanisms under the wow soldering methods belong to transgranular crack.