Research on Cold Working Method of Ultraviolet Laser

At present, with the development of electronic products in the direction of portability and miniaturization, the demand for miniaturization of circuit boards is increasing. For example, modern cell phone and digital camera circuit boards have approximately 1200 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 and smaller. Small vias, in order to effectively ensure the electrical connection between layers and the fixation of external devices, when designing high-speed and high-density PCBs, designers hope that the PCB vias are as small as possible, which not only leaves more wiring. space, and the smaller the via is, the more suitable it is for high-speed circuits. In this way, high-speed connection between the surface mount device 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 characterized by high-density interconnection technology. Today, microvias generally account for 30%-40% of the cost of a PCB board. 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. Currently, industry requirements for micro via devices are only 30-40 microns. In addition, because the current research and development cycle for electronic products is getting shorter and shorter, in order to meet the fast and single requirements of the circuit board in the development stage, the designer requires the equipment to have the functions of punching, circuit pattern engraving and cutting. Now, foreign laser micro-hole equipment with these functions is very expensive.

In industrial production, there are two main applications of laser micro-holes:

1. Using an infrared laser: A substance that heats and evaporates the surface of a material to remove the material, commonly known as heat treatment. Mainly with CO2 (wavelength 10.6 microns) or Nd:YAG laser (wavelength 1.064 microns).

2. Ultraviolet laser: The molecular bond of the substance is directly broken, so that the molecule and the substance are separated. This process does not generate high heat, so it is called cold working. UV-YAG laser (355nm.266nm.213nm) is mainly used in UV-YAG laser. At present, infrared laser thermal processing technology has been widely used, but there are still many researches on ultraviolet laser cold processing methods. Given the many advantages of UV lasers, many companies around the world use UV lasers.