Study on Cold Processing Method of Ultraviolet Laser

Currently, as electronic products are moving towards portability and miniaturization, the demand for miniaturization of circuit boards is increasing. For example, modern mobile phones and digital camera circuit boards are equipped with about 1,200 interconnects per square centimeter. The key to improving the miniaturization of circuit boards is that the line width is getting narrower and the micro-aperture between different wires is getting smaller. Small vias, in order to effectively ensure the electrical connection between layers and the fixation of external devices, designers hope that the vias of PCBs are as small as possible when designing high-speed and high-density PCBs. This not only leaves more wiring space, but also the smaller the vias, the more suitable they are for high-speed circuits. In this way, high-speed connections between surface-mounted devices and the signal board below can be achieved, and the area can be effectively reduced. PCB (PCB) has gradually formed an accumulation and multi-functionality with high-density interconnection technology as its main feature. Now, microvias generally account for 30%-40% of the cost of PCB boards. The minimum size of conventional mechanical drilling machines is 100 microns, which obviously cannot meet the requirements. It is a new type of laser processing method. At present, the industry's requirements for micro-via equipment are only 30-40 microns. In addition, as the research and development cycle of electronic products is getting shorter and shorter, in order to meet the rapid and single requirements of circuit boards in the development stage, designers require equipment with punching, circuit pattern engraving, and cutting functions. At present, foreign laser micro-via equipment with these functions is very expensive.

In industrial production, there are two main applications of laser microhole drilling:

1. Using infrared laser: heating and evaporating the surface of the material to remove the material, usually called heat treatment. Mainly CO2 (wavelength 10.6 microns) or Nd:YAG laser (wavelength 1.064 microns).

2. Ultraviolet laser: directly breaking the molecular bonds of the material to separate the molecules from the material. This process does not generate high heat, so it is called cold processing. UV-YAG laser (355nm.266nm.213nm) is mainly used for UV-YAG laser. At present, infrared laser thermal processing technology has been widely used, but there are still many studies on cold processing methods of ultraviolet laser. In view of the many advantages of ultraviolet laser, many companies in the world use ultraviolet lasers.