Optimization of lead-free wave soldering process for inverter air-conditioner motherboard by DOE

The lead-free wave soldering process of inverter air conditioner motherboard was studied by the method of design of experimental (DOE), and the multiple regression equations of bridging defects corresponding with experimental impact factors were obtained through regression analysis. Results showed that the significance order of experimental factors influencing on “bridging” was as follows: flux flow>orbital inclination angle>spray height> dip tin time> spray speed >preheating temperature. The final optimized combination of process parameters was got: flux flow was 40 ml/min, spray speed was 150 mm/s, spray height was 58 mm, preheating temperature was 100 °C, orbital inclination angle was 6.2 °, and dip tin time was 5 s. Repetitive experimental verification was conducted, and it showed that the defect rate of lead-free wave soldering could be significantly reduced and controlled within 1, 000 PPM using the optimized combination of parameters.