Why Are There Few Three-layer Boards in PCB

1. The process is the same

It can be manufactured in a PCB factory. A four-layer board is generally used to press a copper foil on each side of a CORE, and a copper foil is pressed on one side of a three-layer board for testing. In terms of process flow, they must be pressed together.

2. The price is the same

The difference in process cost between the two is that there is one more copper foil and bonding layer for the four-layer board. The cost difference is not big. When the board factory quotes, generally 3-4 layers are quoted as a grade, and the quotation is based on an even number (of course, more than multiple layers) ), for example, if you design a 5-layer board, the other party will quote according to the price of a 6-layer board, that is to say, the price you design for a 3-layer board is the same as your price for a 4-layer board.

3. Stable process

In the PCB process technology, the four-layer board is better controlled than the three-layer board, mainly in terms of symmetry, the warping degree of the four-layer board can be controlled below 0.7% (IPC600 standard), but when the size of the three-layer board is large, The warpage will exceed this standard, which will affect the reliability of the SMT patch and the entire product, so generally designers do not design odd-numbered layers. Layers are designed as 6 layers, and 7 layers are designed as 8-layer boards.