Design Of The Temperature Monitoring And Controlling System For Diode Laser Soldering Spots

In the field of laser soldering, traditional reflowing soldering and wave solderingtechnologies have been unable to adapt the assembling needs of increasing integration ofmicroelectronic components.That studying new soldering method for componentspackaging on printed circuit boards becomes an urgent problems to be solved.Laser soldering could produce a high quality solder joints of chip pins on the highdensity substrate from its characteristics of localized heating and the rapid rise and fall intemperature of processing regions. In the soldering process, solder temperature is a keyfactor to affect the microstructure and mechanical properties of welding heads.General temperature controller which works by PID control law is manually adjustedPID parameters by experienced engineering staff. However, the circuit precision wouldvary with the change of environment, which leads to limit the range of applications oftemperature controller. To overcome this shortcoming and improve the stability andaccuracy, two typicalself-tuning methods of PID parameters are studied by MATLABsimulation in this paper.Aiming at the newly developed25W semiconductor laser brazing machine whichemits single laser beam, a digital temperature control system is designed for monitoringand controlling temperature of solder joints of where chip pins locate in. The systemexports analog current to control the operating current of the laser power supply moduleby single-chip computer.the negative feedback technology is used to get stable outputcurrent for controlling output light power of laser within the power supply. The contactlessinfrared radiation sensor which is applied to measure the temperature and collecting data.In this paper, Basing on looking up lots of the domestic and international overview ondevelopment of laser soldering temperature control system, a scheme which centres on theintegral separation digital PID algorithm and current-series feedback amplification circuitis desingned. The experiment results indicate that the response time is very short and thesoldering temperature reaches setting value, the steady state error is only0.6℃.