In the design of modern electronic products, flex and rigid-flex circuit boards (PCBs) are widely used because of their lightweight and flexible characteristics. However, flex circuit boards are easily deformed or damaged by mechanical stress during welding, assembly and long-term use. Therefore, an element that can improve the structural strength and stability of the circuit board is needed, and thus PCB stiffener appears. This time, this paper will carry on an in-depth discussion of PCB stiffeners, including the definition of PCB stiffeners, main functions, applications, advantages, and design points.
PCB Stiffener is a material used to increase the structural rigidity and support strength of flex PCBs and rigid-flex PCBs, which not only helps to improve the mechanical properties of circuit boards, but also enhances the assembly efficiency, making the boards more stable when carrying heavier components. Especially in flex PCBs, it can provide additional mechanical support to avoid deformation or damage to the PCBs during operation, welding and use. Overall, PCB stiffener plays an important role in improving the stability and durability of the circuit boards.
A flex PCB requires a stiffener primarily to enhance mechanical strength and stability. Since the material of a flex PCB is very thin and can be bent and folded, certain key areas often need additional support and protection to maintain integrity during use. It is commonly used in welding areas, connector ports, heavy component areas, and other areas where strength needs to be increased. For example:
After understanding why flex PCBs need stiffeners, let's take a look at parameters of PCB stiffeners.
PCB Stiffener materials are rich, common materials such as FR4, polyimide (PI) and metal materials.
In some specific applications, PCB stiffener busbar is also used, which not only enhances the rigidity of the circuit board, but also can be used to conduct current.
The thickness of PCB stiffener varies with different materials, and the appropriate thickness needs to be selected according to the specific application and support requirements.
Stiffeners of different materials have great differences in performance; please see the following table.This form will help you choose the most suitable stiffeners material.
Some designs require multi-layer PCB stiffeners or a combination of multiple materials, in which case you need to consider several points to ensure the reinforcement effect and the performance of the overall board:
Different materials have different coefficient of thermal expansion (CTE) and will expand or contract at different rates under temperature changes. Therefore, when combining a variety of materials, we should choose materials with similar thermal expansion coefficients, so as to avoid delamination, warping or cracking caused by temperature changes.
The bonding between layers is very important for the multilayer stiffeners. Good interlayer bonding ensures that the reinforced plate remains intact under mechanical stress. Therefore, we recommend the use of a special high-strength adhesive between the multi-layer stiffeners (the heat resistance and anti-aging of the adhesive should meet the requirements of the use of the circuit board).
The number of PCB reinforcement boards is large, and the board will inevitably be thicker. Therefore, for the multi-layer PCB stiffener, we must control the thickness of each layer to ensure that it meets the thickness limit and assembly requirements of the circuit board and can provide sufficient support without affecting the overall flexibility of the flex PCB.
In flex PCB or rigid-flex PCB, weight can affect the bending ability and flexibility of the board. Therefore, in the application of multi-layer stiffeners or to use the board for lightweight applications, you should choose lightweight materials, such as polyimide (PI) or thin FR4.
In a Flex PCB, the position of the stiffener has a significant impact on the overall performance and reliability of the board. Common placement locations include:
Follow the following guidelines to ensure the effective integration and functionality of the reinforcement board:
In summary, the PCB stiffener plays a crucial role in the flex and rigid-flex PCB, which not only enhances the mechanical strength of the circuit board, but also effectively improves its stability and durability. I hope this article can provide you with a clear design reference so that you can better choose and configure the reinforcement board in practical applications. If you have any questions, please feel free to contact us!
