Flex Rigid PCB
Rigid flex PCBs, also known as rigid flex circuit boards, are hybrid circuits that combine the structural stability of rigid hardboards with flexible copper layers and connectors. They offer a unique combination of strength and flexibility that makes them ideal for a range of applications in which space and weight are critical factors. Rigid flex PCBs are used in medical devices, military missile guidance systems, wearable electronics, vehicle infotainment systems, and more.
While a flex rigid pcb has many advantages, it can be challenging to design and produce. Often, these hybrid circuits have multiple sections of rigid and flexible components that need to be carefully managed. In addition, they must withstand high levels of vibration and temperature. To ensure a successful outcome, designers must adhere to rigorous design rules and work closely with fabricators to make sure the final product meets its intended specifications and performance.
Using a unified CAD platform that’s optimized for rigid-flex design can help simplify this process. Altium Designer, for example, offers a streamlined, rules-driven design interface that’s easy to use and adapts for rigid-flex design. It also integrates 3D design features, allowing users to quickly visualize and test their designs in three dimensions.
Key Features of a Flex Rigid PCB
One of the most important considerations when designing a flex rigid PCB is determining the proper bend radius for the flexible section. Choosing a smaller radius than needed can cause stress concentration, which can lead to mechanical failure or signal integrity issues.
Other design concerns include achieving optimal layer transitions between the rigid and flexible sections. Transitioning signals improperly can result in impedance mismatches and EMI interference, while signal attenuation may cause signal degradation and loss of function. Finally, deciding where to place the connectors is another critical design decision. Poor connector placement can cause stress points, which can reduce the lifespan of the flex-to-rigid transition area.
Rigid flex circuits are also resistant to vibration and shock, making them an excellent choice for electronic devices that will be in motion or subjected to harsh environments. They can withstand temperatures up to +260°C and are durable enough to resist repeated bending.
When designing a flex rigid PCB, it’s important to avoid putting stress on the copper layers and connections. Whenever possible, traces should be routed perpendicular to the flex-to-rigid area to eliminate stress points and minimize failure. It’s also a good idea to avoid vias and pads in the flex-to-rigid areas, as the mechanical stress can weaken them.
Rigid flex PCBs can also save valuable space in electronic devices by eliminating the need for connecting wire harnesses. This can greatly reduce assembly time and costs and improve reliability and functionality. In addition, the rigid flex circuits are designed as a single unit so that they can be tested and automated to ensure connectivity before they’re assembled into an enclosure. This can help reduce the cost of production, maintenance, and replacement.
