How to see the PCB board is good or bad?

With the rapid development of mobile phones, electronics, telecommunications and other industries, the PCB circuit board industry has been growing rapidly. People are demanding more and more layers, weight, precision, material, color and reliability of components.
However, due to the fierce competition in market prices, the cost of PCB board materials is also on the rising trend. More and more manufacturers monopolize the market at low prices in order to enhance their core competitiveness. 
Faced with various PCB boards on the market, there are two ways to distinguish the quality of PCB boards. The first way is to judge from the appearance, and the other way is to judge from the quality specification requirements of PCB boards themselves.
How to judge the PCB circuit board is good or bad:
First: distinguish the quality of PCB from its appearance
Generally, the appearance of PCB circuit board can be analyzed and judged from three aspects.
1. Standard rules for size and thickness.
The thickness of PCB to standard PCB is different. Customers can measure and check according to the thickness and specifications of their products.
2. Light and color.
External circuit boards are covered with ink, circuit boards can play an insulating role, if the color of the board is not bright, less ink, insulation board itself is not good.
3. Weld appearance.
Because there are many PCB parts, if the welding is not good, the parts are easy to fall off the PCB, seriously affecting the welding quality of the PCB, good appearance, careful identification, a strong interface is very important.
Second: High quality PCB circuit boards need to meet the following requirements
1. Require the telephone to be used well after the components are installed, that is, the electrical connection should meet the requirements;
2. Width, thickness and distance of the line meet the requirements, so as to avoid heating, circuit breaking and short circuit of the line.
3. Copper skin is not easy to peel off when exposed to high temperature.
4. Copper surface is not easy to oxidize, which affects the installation speed. It will be damaged soon after oxidation.
5. No additional electromagnetic radiation;
6. The shape is not deformed, so as to avoid the shell deformation and screw hole dislocation after installation. Now it is all mechanized installation. The hole position of circuit board and the distortion error of circuit and design should be within the allowable range.
7. High temperature, high humidity and special environment resistance should also be considered.
8. The mechanical properties of the surface should meet the installation requirements.