How to Use Flex PCBs in Robotics

Flex PCBs in Robotics

Rigid flex PCBs are used extensively in industrial and automation settings where they’re often subjected to repeated bending, vibration, and high currents. The flexibility and durability of flex circuits make them well-suited for the rugged environments and demanding applications that many robotic systems must endure. This is why more and more companies are relying on flex PCBs in their latest products, especially in the areas of smart devices, wearables, and IoT devices that require a highly flexible yet compact design.

The first step in designing a flex circuit is to determine the desired layout and stack-up, which involves specifying the number of rigid and flex layers and their configuration. The flex layer is typically made of flexible polymer materials like polyimide, while the rigid layers are traditionally made from standard FR-4 material. These layers are bonded together using specialized adhesives, creating a robust and flexible composite structure. Conductive traces are then applied to the substrate, and a protective layer is then applied (typically solder mask or coverlay).

To maximize the functionality of your flex pcbs and ensure it will withstand repeated bending, it’s important to select the right materials and incorporate appropriate features into your design. For example, you should use proper trace widths and spacing to maintain reliable electrical connections and prevent short circuits. It’s also a good idea to add stiffeners to areas that are expected to experience a lot of flexing. Stiffeners can be created from various materials including metals and polymer composites, and they help to increase the strength of a flex circuit by increasing its stiffness.

How to Use Flex PCBs in Robotics

Another consideration when designing a flex circuit is ensuring that the copper pads are strong enough to withstand repeated bending. Ideally, these pads should be rounded to reduce the risk of cracking in case the circuit is bent too tightly. Also, if possible, you should avoid designing the pads in a solid polygon shape. Instead, you should use a hatched or a triangular shape that’s more durable and resistant to cracking.

In addition to these mechanical design considerations, you should also keep in mind the cost of your flex PCB. Rigid PCBs are typically cheaper than flex ones, but it’s important to check the manufacturer calculators to see how much your specific design will cost. This will be particularly important if you have multiple designs in the works, since the manufacturing costs for each may vary significantly.

In general, the fabrication process for a flex PCB is much more complicated than that of a rigid one. The reason for this is the additional steps and materials required to create the flexible layers. According to a recent webinar by Epec Engineered Technologies, the process for a rigid PCB requires 8 steps while that of a flex PCB can be as long as 17 with more materials. To minimize the cost of your flex circuit, you should consider using thinner traces and adding what’s called “Stiffener” to specified areas of your PCB that will be subjected to a lot of flexing. This is a rigid material such as FR4 added to the specified area of the PCB to increase its overall thickness.

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