Drilling characteristics of entry board and the influence on PCB micro drilling process

In this paper, the drilling characteristics of aluminum (Al) entry boards, resin coated Al entry boards, and phenolic resin entry boards were investigated. The chip removal, chip morphology, thrust force, and drilling temperature were measured and analyzed. The cutting characteristics among those materials were compared. In addition, the influence of alloy materials on thrust force of entry boards was analyzed. The results demonstrated four efficacy of entry boards, including chip removal, heat dissipation, buffering, and location. The function of location and buffering were mainly reflected in the beginning of drilling. Effect of chip removal and heat dissipation were related to material of entry board. The resin coated Al entry board performed better than aluminum entry board in buffer and chip removal. Moreover the influence of coating resin and its thickness on drilling process of entry board was obvious. Chips of aluminum entry board were easy to wrapping the drill bit than that of resin coated Al entry board. Thermal deformation of coating resin can increase the curl of aluminum chip, thus contributing to the chip removal. The effect of alloy material on thrust force was significant. The increase of coating resin thickness can enhance the buffer effect on thrust force in some degree. The heat dissipation of MVC resin coated Al entry board in PCB drilling was the best.