Rigid flexible combination board is a method of laminating a flexible circuit substrate and a rigid circuit substrate together, which has both the rigidity of a hard board and the flexibility of a soft board. So, what issues should be paid attention to when making rigid flexible composite boards?

1. The design of rigid flexible composite plates usually changes from rigidity to flexibility, and then to rigidity. The rigid region generally has more layers than the flexible region, and the material is transferred from FR-4 to polyimide in the transition region. When intersection occurs, the overlap between rigid and flexible materials needs to keep the holes away from the transition area to maintain integrity. In addition, many rigid and flexible designs incorporate reinforcing materials such as stainless steel or aluminum to provide additional support for connectors and components.

2. Flexible circuits have bent wires that can affect wiring. Due to possible material stress, it is not possible to place components or vias near the bending line. Even if the components are properly placed, flexible circuits can cause repeated mechanical stress on surface mounted pads and vias. In this case, these pressures can be alleviated by using a through hole coating and supporting the pad with additional coverings.

3. When designing a rigid flexible combination board, it is necessary to consider the electromechanical factors that affect the flexible circuit and the rigid circuit board, and pay attention to the ratio of bending radius to thickness. For flexible circuits, narrowing or increasing the thickness of the curved area increases the likelihood of failure. In this case, it is recommended to maintain the bending radius at least ten times the thickness of the flexible circuit material.

4. Avoid bending the flexible circuit along its exterior or compressing it inside. Increasing the bending angle above 90 ° will increase the tension of the flexible circuit at one point and the pressure at another point.