Research On Optimization Of SMT Solder Paste Detection Threshold Parameters

Solder paste printing is the first process in the surface mount production line.Statistical analysis found that 70% of post-welding defects can be traced back to the solder paste printing process.Solder paste inspection is the key to ensuring the quality of solder paste printing.Reasonable setting of threshold parameters is the basic requirement for solder paste inspection.A wider threshold parameter setting will increase the probability of false alarms,leading to more defective products flowing into the subsequent process;a narrow threshold parameter setting will increase the probability of false alarms,leading to unnecessary shutdown detection.The paper focuses on the optimization of solder paste detection threshold parameters,and aims to provide a scientific method for setting the detection threshold parameters of SMT printing process.First,introduce the common defect types of SMT production process and printing process,analyze the relationship between solder paste volume parameters and printing quality,and clarify that solder paste volume parameters are used as key parameters for solder paste inspection.On this basis,the research ideas for the optimization of the volume threshold parameters of the solder paste detection link are determined.Secondly,use the kernel estimation method to estimate the probability density function of the volume sample data of the key characteristics of solder paste printing quality,analyze the time loss difference caused by false positives and false negatives,and establish the time loss model of the false positives and false negatives;the optimization model of solder paste printing detection parameters is established with the volume threshold parameter as the decision variable and the minimum time loss caused by false positives and false negatives as the objective.Finally,the optimization simulation model of solder paste detection parameter volume threshold was established by Plant Simulation software,and the actual threshold,the threshold determined by 3 ? method and the optimized threshold corresponding to less tin missing report rate,less tin false report rate,more tin missing report rate,more tin false report rate and time loss are compared and analyzed;the single-stage and multistage experiments are designed to analyze the influence of threshold parameters on false report,missing report and time loss The law of the influence of environmental factors.