China Wholesale Populated Circuit Board Suppliers - 4 Layer FPC+FR4 Rigid Flex PCB – Huihe

Design Rules And Precautions Of Rigid Flex PCB

The design of rigid flex PCB is much more complex than the traditional PCB design, and there are many places to pay attention to. In particular, the rigid flexible transition area, as well as the related wiring, through-hole design, all need to follow the requirements of the corresponding design rules.

1. Through hole position

In the case of dynamic use, especially when the soft plate is often bent, the through holes on the soft plate should be avoided as far as possible, which are easy to be damaged and cracked. However, holes can be drilled in the reinforcement area of the soft board, but the edge line of the reinforcement area should also be avoided. Therefore, in the design of rigid flex PCB, when drilling, it is necessary to avoid a certain distance from the combination area

2. Design of pad and via

When the pad and via meet the electrical requirements, the maximum value will be obtained. The connection between pad and conductor adopts smooth transition line to avoid right angle. The independent pad should be added with toe to strengthen the support function.

3. Wiring design

In the flex area, if there are lines on different layers, try to avoid one line on the top layer and the other line on the bottom layer. In this way, when the flexible board is bent, the stress of the upper and lower layers of copper sheet is not consistent, which is easy to cause mechanical damage to the line. Instead, it should be staggered and the paths should be crossed.

4. Copper laying design

For the flexible bending of reinforced flexible plate, the best structure is mesh structure. But for the impedance control or other applications, the electrical quality of the network structure is not satisfactory. Therefore, the designer needs to make a reasonable judgment on whether to use the network copper sheet or solid copper according to the design requirements.

5. Distance between drilling hole and copper sheet

This distance refers to the distance between a hole and the copper sheet. We call it “hole copper distance”. The material of the flex PCB is different from that of the rigid PCB, so that it is difficult to deal with the too tight hole copper distance. Generally speaking, the standard hole copper distance should be 10mil.

6. Design of rigid flexible combination zone

In the rigid flexible joint area, the flex PCB is best designed to connect with the rigid PCB in the middle of the stack. The flex PCB through-hole in the rigid flexible joint area is considered as buried hole.

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