As for the problem of poor tin on the tin surface of PCB, the top PCB manufacturer Speeda summarized the following aspects:
1. Source of tin for materials: In order to reduce the cost of material procurement, some PCB factories purchase recycled tin from the industry or supply sources with unstable content. Generally, PCB factories with very low unit price may have such a risk probability. It is suggested that you should be careful when purchasing. The raw materials used by Speeda - one of the top pcb manufacturers, are excellent and you can rest assured.
2. Storage environment and transportation: This is the link between the circuit board factory and the SMT factory. Generally, there is little inventory of circuit board, the inventory requires proper dry and humid storage conditions, and the package should be complete. In the process of transportation, it is required to handle it with care as much as possible. The vacuum packaging is not allowed to be damaged and stored for a long time. The theoretical storage time of tinplate is one month, but the best weldability is within 48 hours. If the storage time is more than one month, it is recommended to return to the circuit board factory to clean and bake the board with special solution. The baking sheet parameters: 150°/1 hour.
3. The inaccurate operation in accordance with the specifications: The circuit industry is extremely strict with the workshop environment and the requirements of staff's standard operation, especially in the circuit board production, which requires chemical reaction environment, so there should be no infiltration of impurities. After the process of plate tin spraying is completed, a series of subsequent operations require employees to wear anti-static gloves, because finger sweat or dirt in direct contact with the surface will cause surface oxidation. If it causes defects, it will be difficult to spot with our naked eyes. It is also irregular and difficult to show in the test and tin experiment.
4. Tin furnace for tin spraying is not cleaned up on time: Timely maintenance of tin furnace is very important, because tin praying is a vertical cycle process, the board surface of circuit board will be under strong pressure. For those boards whose resistance welding is not dry completely and characters are not firm, it will cause impact and fall off, deposit in the furnace. After high temperature evaporation, if not cleaned for too long, will cause surface adhesion.