With the rapid development of the mobile phone, electronics, and communications industries, the PCB circuit board industry has continued to grow and grow rapidly, and at the same time, people have become increasingly demanding on the number of layers, weight, precision, materials, colors, and reliability of the PCB. However, due to fierce market price competition, the cost of PCB board materials is also on a rising trend, and more and more manufacturers are monopolizing the market with low prices in order to enhance their core competitiveness. However, behind these ultra-low prices is the reduction of material costs and process manufacturing costs, which makes the PCB prone to cracks (cracks), scratches, (or scratches), and its precision, performance and other comprehensive factors do not meet the standards. It will seriously affect the solderability and reliability of the product. Faced with various PCB circuit boards on the market, there are two ways to distinguish the quality of PCB circuit boards: the first method is to distinguish and judge from the appearance, and the other is to judge from the quality specifications of the PCB itself.