Rigid-Flex PCB Applications

Rigid-flex PCB applications are similar to traditional rigid PCBs, with the added advantage of reduced system complexity. Rigid-flex combines flexible printed circuit technology with the high-density interconnectivity of rigid boards; this combination can eliminate the need for a discrete wire harness and supports the optimization of space within tight enclosures. While rigid-flex connections are generally more robust than standard wire-and-plug assemblies, the technology faces greater manufacturing challenges and costs due to a more intricate fabrication process.

How Rigid-Flex Improves on Rigid PCBs

The Middle Ground of Rigid-Flex

The primary advantage of rigid-flex PCB applications over traditional rigid PCBs is the simplification of system integration. Wire harnesses can contribute significantly to the enclosure’s weight and size for electronic systems that use multiple sub-assemblies. Replacing the wire harness with a flexible printed circuit dramatically reduces the electronic device’s size and weight.

Unlike a flexible printed circuit, rigid-flex still benefits from a rigid board’s routing and placement density. The middle ground between a rigid board and a flexible circuit leverages the best of both worlds at the cost of greater manufacturing complexity. Rigid-flex PCBs provide a unique solution for additional design challenges:

• Motion – Devices that rely on bendable motion, such as wearable health/fitness monitors, can utilize rigid-flex layouts to simplify the connector interface and reduce board layout area. Depending on the construction of the flex layers, the bending motion can be fixed or repeatable in one or more directions.
• Portability – Rigid-flex PCBs are essential for portable devices like cell phones, laptops, and other modern devices where size and weight concerns play a significant role in day-to-day operations. Designing the wire harness to fit the rigid PCBs (and not vice versa) means engineers can create enclosures that would be otherwise impossible – like fitting four rigid boards around an optical sensor.
• Signal integrity – When considering the complete transmission path from transmitter to receiver, connectors and wires/cables can exhibit greater loss than a flex PCB connection. Impedance matching with the flex PCB enhances reliability during operation and keeps performance.

Breaking Down Rigid-Flex PCB Applications

Any application can benefit from rigid-flex PCBs, yet some industry applications can better leverage the unique characteristics of rigid-flex. Wearable devices (i.e., medical) use rigid-flex to provide a one-size-fits-most solution for healthcare, aerospace can further improve efficiency by reducing weight, and various other industries benefit from the adaptability of rigid-flex:

• Medical – In medicine, many devices have to conform to the shape of the human body with some reasonable leeway to account for person-to-person differences. Flexible printed circuits with a reduced air gap have a smaller bending radius, giving them a greater range of motion. The enhanced mechanical reliability also limits the effects of wear and ensures a long-lasting, high-performance service life for critical medical devices.
• Sensors and imaging – As the Internet of Things (IoT) continues to evolve and grow in scale, integration of discrete electronic sensors can prove challenging, especially for large sensors or those that can’t be die-packaged for placement during PCB assembly. Rigid-flex PCBs act as a Goldilocks solution, as they can provide the high component density of rigid boards and the tighter enclosures of flex designs.
• Aerospace – Any industry where the weight of the final device is a primary design constraint benefits from rigid-flex over standard rigid. Rigid-flex reduces the system’s weight by replacing a portion of the rigid board and the entirety of the wire harness with the flexible printed circuit. Reducing the weight also improves shock and vibration resistance, a key factor for rapid acceleration.

Your Contract Manufacturer Is as Flexible as Your Circuit

Rigid-flex PCB applications are vast due to the numerous advantages of combining flexible printed circuits with traditional rigid PCBs—weight and size reductions open avenues for electronic assemblies that rigid boards alone cannot meet. Despite their adaptability, rigid-flex designs are not one-size-fits-all from a project appropriateness standpoint. Here at VSE, we’re a team of engineers committed to building electronics for our customers, including a complete design review for manufacturing suitability. We’ve been building life-saving and life-changing devices with our valued manufacturing partners for over forty years.