The Study Of The Temperature Field On Precision Micro Drilling Of Printed Circuit Board

As the basic connector of electronic products,the performance requirements of PCB are increasing with the development of science and technology,as well as the upgrade of products.The drilling quality of PCB directly affects the performance of PCB,and the change of heat conduction,heat dissipation,drilling temperature on drilling of PCB are the key breakthrough to improve the drilling quality,which will also become the research direction that can not be ignored in the industry.Therefore,based on the current research status and development trend,the temperature field model of PCB drilling was established firstly,and then the characteristics of drilling force were studied based on the heat analysis.Finally,the temperature field of PCB drilling was experimented and simulated.In the study of theoretical modeling,the drilling temperature field model of copper foil and epoxy fiber glass cloth were established based on the heat source method,and the thermal conductivity,density and specific heat capacity of the epoxy fiberglass cloth composite were analyzed.Then the PCB drilling temperature field model was established by combining the heat source method and the difference method in numerical analysis.In the study of drilling force characteristics,the force measuring platform was built to measure the thrust force and torque of copper foil,epoxy fiberglass cloth and PCB under different drilling conditions,then the collected signal was denoised by using the method of the cumulative average processing principle of time domain signal period,and the processing results showed that the method could effectively improve the signal to noise ratio.After that,the characteristics of the drilling force was analyzed.The results showed that the thrust force and torque increased with the increase of the feed speed,and the thrust force decreased with the increase of the spindle speed,but the decreasing trend gradually slowed down,while the torque would increase first and then decrease as the spindle speed kept increasing.The larger the diameter of the tool,the greater the thrust force and torque were.In addition,for different material,the thrust force of the copper foil was significantly higher than that of the PCB and the epoxy fiberglass cloth.Among them,the thrust force of epoxy fiberglass cloth was the smallest.However,the torque among them was opposite.Then,based on the experimentalresults,an empirical model of thrust force and torque were established by using empirical formulas.Finally,the heat released during the drilling process was calculated by the principle of energy conservation.In the aspect of temperature field experiment and simulation,the infrared temperature measurement platform was built to analyze the temperature variation.The results showed that the drilling temperature of PCB increased first and then decreased with the increase of feed,while increased with the increase of spindle speed and tool diameter.For different materials,the results were also very different due to the difference in thermal conductivity.The temperature of the epoxy fiberglass cloth was significantly higher than the surface temperature of the copper foil and PCB.Then,based on the measured temperature results,the heat distribution coefficient of the copper foil and the epoxy fiberglass cloth was obtained by using the genetic algorithm.In addition,the calculated theoretical temperature and the actual temperature of PCB were through comparison and analysis.The results showed that the theoretical of the mathematical model and the measured values of the PCB temperature were highly consistent.The absolute errors were close,and the relative errors were within 15%.Finally,the temperature field of PCB drilling was simulated and analyzed.The simulation results showed that the PCB drilling temperature was concentrically distributed,the closer to the center of the hole,the higher the temperature was,and the temperature gradually increased along the depth of the drilling hole,which further verified the rationality and correctness of PCB temperature field model.