FLEXIBLE PCB DESIGN applications
Whether your circuit is used in a small, portable device or an aerospace piloting control panel, flexibility plays a critical role. From big swings in temperature and vibration to the rigors of daily use, flexible circuits must be able to withstand whatever is thrown their way. Flexible circuits can also reduce assembly and repair costs. Replacing bulky wire and cable with a PCB that is thinner and lighter eliminates the cost of components, wire and solder connections, and allows for more space in your package.
FR4, FR-Lite and other flex-PCB materials have a lower minimum thickness, which helps with the assembly process and cost savings. Additionally, a thinner substrate can improve thermal management by dissipating heat more effectively. This is especially important in a flex application where the board must bend.
Another advantage of a flexible pcb design is the ability to incorporate three-dimensional shapes into your application. This can be critical for wearable technology, modern hearing aids or several minuscule devices that must fit into tight spaces. Because a flex-PCB is much thinner than a rigid PCB, it can be easier to mold into three-dimensional configurations.
What role does flexibility play in FLEXIBLE PCB DESIGN applications?
Flex circuits are also less expensive than traditional rigid-PCBs because they require less material. This makes them a great option for budget-conscious applications, or when you are trying to achieve the same function as a rigid-board within a smaller package.
While a thin flex circuit is ideal for many applications, there are some cases where it is not suitable. Depending on the design, a flex-PCB may not be compatible with all types of surface-mount components and may require specialized soldering techniques to prevent damage during handling.
A few tips when designing a flex-PCB include: Keeping the area around the bend free of discontinuities like vias, cut-outs, slits and holes is essential for maintaining a robust circuit. When a via is bent, it creates stress and cracks that eventually lead to malfunctions and failures. To avoid this, ensure that the traces on both sides of the bend are the same width. Also, make sure that the traces are routed perpendicular to the bend to minimize stress on the copper.
In a flex circuit, it is important to understand the difference between panel plating and pad-only-plating (button plating). Panel plating has copper deposited across the entire panel, while button plating only deposits copper on the pads. This technique is preferred in a flex circuit because it offers better etch yields and improved copper thickness control. It is recommended that you always have a drill-to-copper distance of at least 8 mils.
Flex circuits are prone to movement and contraction during production, so it is important to plan routing accordingly. Keep in mind that the drill-to-copper distance is more important on a flex circuit than a rigid-board. In addition, consider adding tabs or anchors to vias to assist with preventing peeling.
Finally, a flex circuit must be designed to accommodate the expected number of bend cycles. IPC standards provide guidelines for acceptable bend cycles, but these are generalized guidelines. Therefore, it is critical to perform in-house testing during prototyping to ensure that your flex circuit can meet the requirements of your application.