size limitations for rigid flex circuits
Rigid flex circuits are becoming indispensable for many electronic devices, including laptops, cameras, robotics, and automotive control systems. Their flexibility and capacity to fit into small spaces makes them a viable alternative to more complex wire harnesses, which can be costly, time-consuming, and prone to mechanical failures. However, these advantages come with a price; high-quality rigid flex PCBs cost more than cheaper alternatives, but they offer better functionality and reliability in the long run.
The most significant limit to a rigid flex circuits is the maximum amount of stress the copper conductors can tolerate during deformation. When the conductors are forced to bend beyond their limits, they can crack and break, resulting in poor performance and possible failure of the entire circuit board. To reduce this risk, designers should follow IPC 6013C design guidelines when making a rigid-flex circuit. These guidelines specify the electrical constraints, such as signal clearance and controlled impedance, that should be applied to both the flexible and rigid sections of the board.
The IPC guidelines also cover mechanical requirements, such as the minimum bending radius, that should be achieved by a rigid-flex circuit. In addition, the guidelines provide information on the pad and hole plating used to minimize stress points. Ideally, these pads and holes should have anchoring spurs that prevent the separation of the base material from the copper during bending. The pads should also be filled to minimize the stress of repeated flexing.
Are there any size limitations for rigid flex circuits?
Other factors that can impact the performance of a rigid-flex circuit include the choice of a conductive material, the etching process, and the thickness of the copper. The preferred choice is rolled annealed copper (RBAC), which offers higher reliability and greater flex life compared to etched copper. The etching process should be controlled to prevent the formation of shorts between adjacent layers and to avoid excessive copper thickness, which can cause conductor fatigue and fracture.
Lastly, designers should keep in mind the limitations of their fab house’s capabilities when selecting a rigid-flex circuit. For example, not all manufacturers can produce a rigid-flex circuit with a core made of adhesive-less polyimide. This is a necessary feature for the flexibility of rigid-flex circuits, as it reduces risks of cracking and breaking during assembly and operation.
Choosing the right rigid-flex circuit manufacturer is crucial to ensure that you get the best possible results for your project. Cheaper options may cut corners in the design, fabrication, and testing of their products, resulting in thermal, electrical, and flexibility issues in the final device. However, a reputable manufacturer will pay careful attention to detail and go the extra mile to make sure that their rigid-flex circuits perform flawlessly. Investing in these high-quality products will be well worth it in the long run. They will save you the hassle of dealing with unforeseen problems down the line, and they will improve the overall quality of your finished product.
