In the design and production process of multi-layer circuit boards, each layer must be symmetrical, and the difference in size may cause distortion. In the production process, four-layer boards are easier to control than three-layer boards. The warpage of the four-layer board can be controlled at 0.7%. It is lower than (IPC600 standard), but when the size of the three-layer board is large, the warpage will exceed this standard, and the warpage beyond this standard will affect subsequent chip production and product quality.
Generally, double-layer PCB circuit board design does not design an odd number of layers. The manufacturing difference between the two is a four-layer board with an extra layer of copper foil and an adhesive layer. There is little difference in cost. When the PCB manufacturer brings 3-4 layers as the level price, the price is defined by even number. For example, if you design a 5-layer board, the other party quotes a price for a 6-layer board. That is to say, the price of the 3rd floor of your design is the same as the price of the 4th floor of your design. So why not choose a four-layer board?
The double-layer PCB circuit board is mainly composed of the following layers: signal layer, internal plane, mechanical layer, mask layer, silk screen layer, and system layer. The signal layer is divided into top layer, middle layer and bottom layer, and is mainly used for assembling various components, or for wiring and soldering.
