| dc.description.abstract | FR-4, or glass fiber-reinforced electronic-grade epoxy resin, is a crucial material for printed circuit boards (PCBs) due to its excellent electrical insulation, high mechanical strength, elevated heat resistance, chemical stability, and cost-effectiveness. In the context of FR-4 substrate cutting, commonly employed techniques include V-cutting, high-pressure water jet cutting, and diamond wheel cutting. Generally, diamond wheel cutting has been the primary method for FR-4 substrate separation, offering fast cutting and good surface quality. However, with the market demand for smaller, lighter, and more high-functional components, the need for multi-layer and higher density circuit fabrication has become increasingly vital. As line widths and spacings shrink to tens of micrometers or smaller, traditional mechanical diamond wheel cutting methods are showing limitations.
Laser cutting, with advantages such as precision, small kerf, suitability for complex shapes, and no mechanical contact to prevent cutting force-induced damage, is considered a promising technology. However, the mixture of glass fiber and epoxy resin presents challenges for laser cutting. Glass fiber can generate debris, burrs, and cracks during processing, affecting the substrate′s micro-precision and reliability. Additionally, epoxy resin is prone to forming a carbonized layer due to the high thermal effects of laser cutting, influencing the substrate′s resistance and dielectric constant, thereby impacting electrical and signal transmission performance. Post-processing is necessary to remove residual carbonization.
To address issues like debris, burrs, and high thermal effects associated with conventional laser cutting, this study employs ultrafast laser cutting on FR-4 substrates. The aim is to enhance cutting quality by utilizing high instantaneous power and low thermal effects during ultra-short pulse durations. Using a femtosecond laser, the study compares the cutting quality and speed of 0.2 mm and 0.8 mm thick FR-4 substrates cut in both atmospheric and underwater conditions. Results indicate that cutting underwater yields fewer residual debris and lower thermal effects compared to cutting in the atmosphere. Under the parameter set: power 14.99 W, frequency 500 kHz, scan speed 500 mm/s, water level height 2118 μm, and 1250 scans, high-quality cross-sections comparable to mechanical cutting can be achieved. The study also discusses patterned cutting and processing parameters. | en_US |