In the simplest version, a printed circuit board is a dielectric plate with a system of conductive patterns on its surface, designed to power electronic components. There are several types of PCBs, differing in the number of conductive layers and the type of insulating material.
The main applications of 355 nm nanosecond solid state lasers in PCB manufacturing are cutting (depaneling), structuring and drilling blind holes for mounting components. UV allows a wide range of PCB materials to be handled, from standard materials such as FR4 and similar resin substrates, ceramics to flexible PCB materials including polyamide.
The need to obtain blind holes of small diameter due to the increase in the density of printed circuit boards has led to the active use of lasers. The method of mechanical drilling and CO2 laser drilling is applicable to obtain holes of large diameter. The drilling process involves removing a few tens of micrometers of insulator to gain access to the copper conductive layer. The difficulty of drilling holes with a diameter of 50-60 microns by CO2 radiation is associated with the rigidity of focusing and a large amount of melt. In contrast, ultraviolet photoablation provides a hole without melt and traces of carbonization.
355 nm nanosecond solid state lasers are used to isolate finished devices from a PCB panel. The traditional method is to use a mechanical milling bit. However, manufacturers are striving to increase the throughput of the process and reduce the cost of consumables. CO2 lasers are suitable for the separation task, but cause charring of the cut surface. This is unacceptable: carbon can be conductive and absorb moisture, resulting in device failure. In addition, carbon compounds are aromatic, which is unacceptable for applications where the product will be close to the user's face, such as mobile phones, headsets, and the like. The "cold ablation" mechanism of UV exposure minimizes the appearance of burrs, charring, and the negative effects associated with thermal stress.
