Study on Effect of Tool Wear on Drilled Hole Quality of Printed Circuit Boards

In the current manufacturing of printed circuit boards (PCBs), micro-drills are generally used to make smaller diameter through-holes in PCBs. The purpose of this paper is to clarify the effect of flank wear and margin wear on drilled hole quality. Series of PCBs drilling tests are carried out to investigate hole quality, hole location accuracy and hole wall roughness. The cutting torque and cutting force are measured by Kistler 9329 and 9257B respectively. Detailed observation of drilled hole surface is made by SEM. The hole location accuracy does not get worse with increasing flank wear of drill. On the other hand, the hole location accuracy becomes worse with increasing margin wear of drill. The hole wall roughness when using the margin wear type drill is worse than using the flank wear type drill. In addition the cutting torque when using the margin wear type drill is larger than using the flank wear type drill.