How Do Rigid Flex Circuits Handle Vibrations and Shocks?

Rigid Flex Circuits Handle Vibrations and Shocks

Rigid flex circuits, a type of printed circuit board (PCB) that incorporates rigid sections with flexible areas, are well-suited for applications that require durability and performance in a small package. They can be used to withstand vibrations and shocks in many industrial, medical and automotive applications.

However, the benefits of rigid flex PCBs do not come without drawbacks, and manufacturers need to weigh these against the unique needs of their application before selecting this option. The higher manufacturing costs associated with rigid flex PCBs can be a deterrent to some projects. Costs can be reduced, however, when multiple boards are produced in a long production run.

The ductility and lower mass of rigid flex circuits are key elements in their ability to absorb vibrations and shocks. In addition, the ultra-thin circuit traces on rigid flex circuits provide a higher connection density than traditional rigid PCBs. This enables more components to be mounted within a smaller space, reducing overall system size and weight. Compared to a similar wired solution, a rigid-flex circuit weighs on average 10% less and delivers superior shock and vibration resistance.

This is primarily due to the materials used in rigid-flex circuits, which are thinner and more durable than conventional copper foil. In fact, the conductive metal is actually etched directly into the circuit substrate material (typically FR4) rather than plated on afterwards as in conventional PCBs. The result is a rigid-flex circuit that can withstand much higher temperatures, making it ideal for high reliability military and medical applications.

How Do Rigid Flex Circuits Handle Vibrations and Shocks?

Another advantage is that rigid-flex circuits are typically produced with an insulator between each layer of the substrate. This reduces the risk of signal interference caused by electrical current passing through different layers of the substrate. This also helps to minimize electromagnetic field (EMI) noise and impedance mismatches between different areas of the board. Rigid flex circuits can be further improved for stability by adding stiffeners.

While the advantages of rigid flex circuits are numerous, the design process is a bit more complex than traditional rigid and fully flexible PCBs. Several factors must be considered when designing rigid-flex PCBs, including mask types, dielectrics, stiffeners and copper thickness. These factors must be optimized to meet the specific requirements of a particular application, including mechanical considerations and flammability ratings.

When it comes to design, it’s important to avoid placing pads, holes and vias close to the bending area of the circuit. These areas can apply mechanical stresses that could tear or damage the structure of the plated hole. Instead, designers should focus on placing these connections on the rigid section of the circuit or on the flex area that is not subject to bending.

The design process for rigid-flex PCBs begins with using a PCB layout software to determine the placement of components, traces and connections. Once this is complete, the layout can be sent to fabrication. During this phase, manufacturers should consult with the design engineer to ensure that the rigid-flex PCB will fit into the final product and meet the required specifications for functionality, durability and performance.