Ensure Reliability in High-Density Rigid Flex PCBs
For high-density rigid flex PCBs, there are a few design rules that should be followed to ensure reliability. These include designing for structural integrity, avoiding stress concentration points, and conducting a mechanical stress analysis to identify potential problem areas. Also, ensuring proper signal integrity, impedance control, and ground plane placement is important for a robust design. Finally, a thorough visual inspection and adherence to quality standards can help prevent manufacturing defects that may impact the performance of the rigid-flex circuit.
Unlike traditional PCBs that require connectors and cables to connect separate boards or sections, rigid flex circuits combine the best of both worlds by integrating rigid and flexible sections into one structure. This significantly reduces the number of interconnect points and enhances reliability by minimizing the chance of intermittent failures or electrical discontinuities. In addition, rigid-flex PCBs are able to accommodate a variety of components, including connectors and ICs.
However, the use of multiple flexible sections in a PCB can introduce bending and stress to the system, leading to a decrease in durability and reliability. To counteract these issues, designers should ensure that all of the flex sections are anchored with plating and anchoring stubs to support their structure. In addition, all traces should be spaced apart to avoid I-beaming and stress that can cause copper breakage.
How to Ensure Reliability in High-Density Rigid Flex PCBs
Another way to improve the reliability of a high-density rigid-flex circuit is by using stiffeners. By adding rigid dielectric material to a flex section, it can be made much more durable and can even help protect the underlying copper layers from solder. Stiffeners should be placed at critical sections, such as where a flex section is connected to a rigid section or where a rigid-flex connection point is needed.
Other design tips that can improve the reliability of a rigid-flex circuit include stagger traces and routing them perpendicular to the overall bend radius. This will minimize stress that can damage copper traces and cause signal loss. It is also a good idea to avoid routing vias in areas that are prone to mechanical stress and keep the distance between rigid and flex sections as short as possible.
Rigid-flex circuits require special consideration when deciding how to support SMT component pads, as these must be designed for the bending environment. SMT pads have a lower tolerance to mechanical stress, so it is a good idea to use plated anchoring stubs and reduced coverlay access openings to prevent bending at the pad contact area. Also, pad sizes must be sized larger for a high-reliability flex circuit to allow sufficient room for solder fillet formation and strong bonding.
In addition, a rigorous Design for Manufacturability review should be conducted to identify potential issues and resolve them before sending the design for production. Lastly, working with a manufacturer that offers design and engineering support to optimize rigid-flex PCBs will help to ensure that your final product is reliable and durable. Choosing a supplier that can offer wholesale options will give you access to high-quality and cost-effective rigid-flex PCBs that will meet the performance requirements of your next electronic device.