Estimation of Micro-Hole Shape in Laser Direct Drilling of High Heat Radiation Typed Printed Circuit Boards (Process Monitoring with a High Speed Camera)

Recently, the development of electronic devices, such as smartphones, has meant that printed circuit boards (PCBs) have become complex multi-layer ones to provide both multiple functions and be compact. Blind via holes (BVHs) connecting the layers of the multi-layer board are processed by using a CO2 laser. The many benefits of direct processing by CO2 laser include a lower disconnect of the hole position as a result of the base drilling process in the inner layer circuit pattern. Also, efficiently dissipating heat from components improves the quality of the product as digital home appliances are increasingly compact, lightweight, and thinner. Using PCBs raises the radiation performance by the addition of alumina filler at the insulated layer. However, adding alumina filler means that laser processing is difficult, processing efficiency is reduced, and debris on the surface around the drilled hole increases. We consider what causes the changes in the processing hole by changes in the alumina filler content on the basis of data on drilling phenomena gathered with a high-speed camera. We found that the insulating layer material didn’t effect the diameter of the drill hole per laser spot diameter. The cross-section processing is done in a cone initially, and the truncated cone is then processed. And, we found that the hole depth and processing overhang was reduced, and the amount of scattering increased with the amount of alumina content filler.