2022-02-18
Why is there no three-layer board in PCB?
Will there be any friends who have ever wondered why there is no three-layer PCB in the PCB? Today, I will answer it for you!
1. The same process
It can be manufactured in a PCB factory. Under normal circumstances, a copper foil is pressed on both sides of the four-layer core, and a copper foil is pressed on one side of the three-layer core. In terms of process flow, stamping is necessary.
2. Same price
The difference in the cost of the two processes is that the four-layer board has an extra layer of copper foil and an adhesive layer, and the cost difference is not large. When quoting from the sheet metal factory, generally 3-4 layers are quoted as a grade, and the quotation is defined by an even number (of course, more than multiple layers). For example, if you design a five-layer board, the other party will quote the price of a six-layer board, that is, the price of the three-layer board you designed is the same as the price of the four-layer board you designed.
3. Process stability
In the PCB process, the four-layer board is easier to control than the three-layer board. Mainly in terms of symmetry, the warpage of the four-layer board can be controlled below 0.7% (ipc600 standard). However, when the size of the three-layer board is larger, the warpage will exceed this standard, which will affect the reliability of the SMT patch and the entire product. Therefore, ordinary designers do not design odd-numbered layers. Even if the odd-numbered layers realize their functions, they will be designed as pseudo-even layers, that is, 5 layers are designed as 6 layers, and 7 layers are designed as 8 layers.
This is why there is no three-layer board for pcb! Hope it can give you some reference!
