How long the circuit board is stored depends on the surface treatment. Gold and electroplated gold are the longest. They can be stored for two or three years under constant temperature and humidity conditions. Followed by tin spraying and oxidation resistance. Especially for anti-oxidation, it is best to wire it immediately after getting the board, and it can be stored for the shortest time. About 3 months. Boards that have been in stock for a long time must be baked before going online, otherwise they will easily burst during reflow soldering.
Definition of storage time of four-layer circuit board:
The quality of the four-layer circuit board is defined in IPC. The surface process is anti-oxidation. If the vacuum package is not opened, it will be used within half a year, and the vacuum package will be removed within 24 hours, and the temperature and humidity are controlled. Under the environment, the board should be used within one year after unpacking, and the film should be pasted within a week after it is opened. The temperature and humidity should also be controlled. The gold board is equivalent to the tin board, but the control process is stricter than the tin board.
Four-layer circuit board refers to the PCB Printed Circuit Board is made of four-layer glass fiber. Usually SDRAM uses a four-layer board. Although it will increase the cost of the circuit board, it can avoid noise interference.
Since the printed circuit board is not a general terminal product, the definition of the name is slightly confusing. For example, the motherboard for personal computers is called the main board, and cannot be directly called the circuit board. Although there are circuit boards in the main board, They are not the same, so when evaluating the industry, the two are related but not the same. Another example: because there are integrated circuit components mounted on the circuit board, the news media call it an IC board, but in fact it is not equivalent to a printed circuit board. We usually say that the printed circuit board refers to the bare board-that is, the circuit board without upper components.