Study On The Influence Mechanism Of Drilling Temperature And Prediction Of Drilling Force In PCB Ultra-high Speed Drilling

Printed circuit board(PCB) is an important part of all kinds of electronic products, and the processing of micro holes is a key step in the production of PCB. With the miniaturization, lightweight, multiple-function and intelligentization of electronic products, the diameters of micro holes on the PCB are getting smaller and smaller, the hole space is also getting smaller and smaller, and the requirements of the quality of drilling and drill life are getting stricter. Therefore, PCB mechanical micro drilling is facing a huge challenge. With the further reduction of the size of the micro drill bit, it is more and more difficult to collect all kinds of signals in the process of micro hole drilling, which is closely related to the quality of the micro holes and the life of the micro drill bit. In this dissertation, the precision measurement of the micro drill bit temperature and the influencing mechanism of drilling temperature and the prediction of drilling force in the process of PCB ultra high speed drilling were studied.In the study of drilling temperature during the process of PCB ultra high speed drilling, because of the small size of PCB micro drill bit, the infrared camera was applied to measure the drilling temperature of the drill point. The surface emissivity of the PCB micro drill bit was calibrated before the drilling temperature measurement by experiment method. Then the drilling temperature of the micro drill bit was measured by infrared camera during the process of PCB ultra high speed drilling. The influencing mechanism of drilling parameters on the drilling temperature of the micro drill bit was studied by experiment. The most significant influencing factor on the micro drill bit temperature was spindle speed, and the second most significant factor was retract rate, and the effect of infeed rate in the selected range was not significant in this dissertation. As for the spindle speed, the spindle speed increased form 110 krpm to 150 krpm, the average temperature of the micro drill bit decreased first and then increased. For retract rate, the retract rate increased from 150mm/s to 350mm/s, the average temperature of the micro drill bit increased first and then decreased.In the study of the drilling force during the process of PCB ultra high speed drilling, a semi-empirical mechanical model for drilling was established based on oblique cutting theory and fiber reinforced composite cutting mechanics model, and the drilling force of two different sizes of PCB micro drill bit at different feed rate was predicted using the method of mechanical model combined with experiments. In the experiment of the drilling force measurement during the process of PCB ultra high speed drilling, the drilling force signals were easy to be affected by the vibration of the machine tool and other noise, thus the measured drilling force signals were processed through the signal processing toolbox(SPTOOL) of MATLAB. The predicted drilling forces were close to the experimental values, and the drilling force relative error of 0.3mm micro drill bit was about 10%, and the drilling force relative error of 0.11 mm micro drill bit was less than 10%. With a high accuracy of prediction, this method can be applied for drilling force prediction in PCB ultra high speed drilling.