The influencing mechanism of drilling parameters on micro drilling temperature on the basis of calibration of surface emissivity of micro drill bit

Purpose The purpose of this paper is to calibrate the surface emissivity of micro drill bit and to investigate the effect of different drilling parameters on the temperature of micro drill bit in printed circuit board (PCB) micro drilling process. Design/methodology/approach The surface emissivity of micro drill bit was obtained by experiments. Analysis of variance (ANOVA) was applied in this study to analysis the effect of different drilling parameters on the temperature of micro drill bit in PCB micro hole drilling. The most significant influencing factor on micro drill bit temperature was achieved by ANOVA. Findings First, the surface emissivity of cemented carbide rod decreased from 0.4 to 0.32 slowly with temperature in the range of 50-220°C. Second, the most significant influencing factor on the micro drill bit temperature was spindle speed among the drilling parameters including spindle speed, retract rate and infeed rate. Research limitations/implications In this paper, the influence of roughness of black coating, carbide rod and micro drill bit on the surface emissivity calibration and the temperature measurement was not considered. Originality/value A new simple method has been presented to calibrate the surface emissivity of micro drill bit. Through calibrating the surface emissivity of micro drill bit, the temperature of micro drill bit can be measured accurately by infrared thermometry. Analyzing the influences of different drilling parameters on the temperature of micro drill bit, the mechanism of drilling parameters on drilling temperature is achieved. The basis for the selection of drilling parameters to improve the hole quality is enhanced.