| 90W diode-laser soldering system was developed. It possesses characters of short laser wavelength, continuous/pulse output mode, long laser life and small spot diameter (200μm), which it is the first one in our country as diode-laser soldering system.Experiments with Sn-Ag-Cu lead-free solder and Sn-Pb solder were carried out on pure Cu substrate using newly developed 90W diode-laser soldering system, the regulations of the wetting properties of different solders on pure Cu substrate were studied with different laser output currents and the characteristics of microstructures of micro-joints were also analyzed. Compared with microstructures of micro-joints soldered with different solders by means of diode-laser soldering system and IR reflow soldering system, it was found that there is an optimum current value on the tensile strength of micro-joints soldered with diode-laser soldering system. The microstructures of the joints soldered with the optimum current value are homogeneous, the crystal grains of joints are fine, no defect exists in the joints and the mechanical properties are the best when the joints soldered with optimum current value of diode-laser output.Quad flat pack devices(QFP) and layer ceramic resistor components(RN) were soldered using diode-laser soldering system (with different laser output currents) and IR reflow soldering system respectively. Mechanical properties and microstructures of soldered joints were studied and the relationships between mechanical properties and microstructures of soldered joints were also analyzed. Results indicate that mechanical properties and microstructures of soldered joints were changed greatly with different laser output currents, the more homogeneous the eutectic network structures and Ag3Sn compounds distribute in soldered joints, the better the mechanical properties are. In a certain range of laser output current, microstructures of soldered joints with laser soldering system are finer obviously than that soldered with IR... |
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