In the process of miniaturization, lightweight and multifunctional development of modern electronic equipment, the flexible board of PCB circuit board plays an increasingly important role. Its material and structural design have a critical impact on the bending performance.
First of all, the material selection of the flexible board of PCB circuit board directly determines its basic bending characteristics. Commonly used flexible board materials include polyimide (PI) and the like. PI has excellent high temperature resistance, chemical stability and mechanical strength. The rigid aromatic ring in its molecular structure gives the material a certain hardness, while the flexible imide bond provides good flexibility, allowing the flexible board to withstand a certain degree of bending without breaking. However, PI materials of different thicknesses and models will vary in bending performance. Thinner PI films are relatively easier to bend, but may sacrifice strength; while thicker PI films have higher strength, but the difficulty of bending will increase. In addition, as the conductive layer of the flexible board, the thickness and ductility of copper foil also affect the bending performance. Thin copper foil is not easy to break when bent, and can better adapt to the deformation of the flexible board, reducing the risk of circuit disconnection caused by copper foil cracking.
Secondly, the structural design of the flexible board of the PCB circuit board is a key link in optimizing the bending performance. For example, in a single-layer flexible board structure, the relative position of the circuit layout and the substrate will affect the bending performance. If the circuit is designed in the neutral layer position close to the flexible substrate, the tensile and compressive stresses on the circuit during the bending process are relatively small, thereby reducing the possibility of circuit breakage. For multi-layer flexible boards, the design of the interlayer structure is more complicated. Reasonable design of the combination of materials of each layer, the thickness ratio and the performance of the interlayer adhesive can enable the flexible board to maintain good bonding between the layers during multiple bending processes and avoid delamination. For example, the use of a soft and strong adhesive can ensure the electrical connection between the layers while adapting to the relative displacement of the layers during bending, thereby improving the overall bending durability.
Furthermore, special structural designs such as the treatment of the bending area have a significant effect on improving the bending performance. In areas where the flexible board needs to be bent frequently, slotting, thinning and other designs can be used. Grooving can reduce the rigidity of the area, making the bending smoother and reducing the stress concentration at the bend; thinning treatment reduces the internal resistance of the material when bending and improves the flexibility of bending. At the same time, rounding the bending area can avoid stress concentration at sharp corners compared to right angles or sharp angles, effectively preventing cracks from being generated and expanding from these parts during the bending process, thereby extending the service life of the flexible board.
Finally, environmental factors also interact with the PCB circuit board flexible board materials and structural design to affect the bending performance. In high temperature environments, the performance of flexible board materials may change, some materials will become soft, and others may experience thermal expansion. At this time, a reasonable structural design can reserve a certain amount of expansion space or use a combination of materials with better high temperature resistance to ensure that the flexible board can still maintain good bending performance in high temperature environments. In a humid environment, the material may absorb moisture and cause performance degradation. Therefore, the setting of a moisture-proof layer or the selection of materials with low water absorption in the structural design needs to be considered to maintain the stable bending performance of the flexible board under different environmental conditions and meet the needs of various complex application scenarios.
