Investigation On The Process Of Laser Microvia In The Printed Circuit Board

Laser microvia technology is one of the key technologies of the modern manufacturing of printed circuit board (PCB), which is widely utilized in microvia of PCB. During the process, the material is instantaneously removed by the intense laser which is caused by short-pulse and high peak power laser focusing. In our country, the PCB microvia market is very large, but level of the laser microvia technology is at the initial stage. The investigation of the methods and techniques of microvia for PCB with self-developed CO2 laser, and the effect of laser parameters and optical system on the performance of microvia have been carried out in this paper.Firstly, the characteristics of microvia produced by UV YAG laser, RF CO2 laser and TEA CO2 laser were compared. Secondly, the effect of the laser parameters on the microvia characteristics was studied. Lastly, experimental study of laser microvia PCB with self-developed TEA CO2 laser was carried out. By using inside and outside apertures, expanded system and short lens, high-quality laser beam and smaller focus laser spot were obtained, resulting in microvia with diameter of less than 150um achieved. This is the first time in our country to obtain such small microvia by using TEA CO2 laser. Furthermore, the problems of laser microvia with TEA CO2 laser were analyzed and related solutions were provided.The study results indicate that the optimal design of optical system is very important in the process of laser microvia with TEA CO2 laser. The roles of aperture, expanded beam system and focus lens are different. The outside aperture makes the low mode beam through and image. The expanded beam system expands the laser diameter which induces the tiny laser spot. It is helpful to get microvia with good quality and small diameter by using shorter focus, higher magnification expander and small aperture. The performances of the microvia can be improved and quasi-fundamental mode can be obtained by putting the appropriate aperture into the resonator of TEA CO2 laser.