7 Must-Know Considerations for Designing a Reliable Flexible PCB Stackup
Designing a Reliable Flexible PCB Stackup
A rigid-flex printed circuit board is a hybrid of rigid and flexible substrate materials that combine to create a structure capable of flexing and folding without compromising the integrity of the circuitry. Rigid and flexible layers are bonded together with adhesives, reinforcements and coverings to form a structure that is durable enough for use in a variety of electronic products. In order to ensure that a rigid-flex PCB stackup is able to withstand repeated bending and flexing movements, it’s essential for engineers to carefully design the structure’s layer configuration. In this article, we’ll explore 7 must-know considerations for designing a reliable rigid-flex PCB stackup.
The conductive circuitry on a flexible pcb is comprised of copper traces on both the rigid and flex sections of the board. The copper traces are used to connect the various components on the board and provide power and signals to each component. The conductive circuitry is typically insulated from the surrounding areas of the board by a coverlay, which can be made of polyimide, PET or FR-4 materials. The coverlay is also responsible for protecting the copper traces from corrosion and environmental factors such as water, light and chemicals.
In addition to insulating and protecting the copper traces, the coverlay can also provide electrical isolation between different layers of the PCB. The rigid and flex layers are held in place by an adhesive layer, often made of no flow pre-preg, to form a structure that is strong enough for repeated bending and flexing. The pre-preg can also help to improve the thermal performance of the PCB, by allowing heat to dissipate effectively through the rigid sections.
7 Must-Know Considerations for Designing a Reliable Flexible PCB Stackup
A flex-PCB’s layer count is based on the complexity of the circuitry, shielding requirements, minimum bend radii, and reliability motion cycles. Higher layer counts allow for more routing channels, but can also impact flexibility and cost. Choosing the right number of flex layers is vital for optimal performance and signal quality. The number of signal layers will also depend on the specific application, with high-speed applications requiring more signal layers than low-speed devices.
Another important consideration is the material selection for the flex section of the board. Choosing the right materials will improve flexibility and reliability, while reducing the overall weight of the device. This is especially important for portable and wearable products that will be subject to repeated flexing. The choice of material will also affect the product’s ability to disperse heat.
Engineers should always check with their fabrication house to make sure that the layer stackup they have designed can be reliably fabricated. Fabricators have years of experience working with a variety of materials, and can advise on whether or not a particular stackup will be suitable for the application.
Designing a robust rigid-flex PCB stackup requires careful planning to optimize signal integrity, flexibility, space constraints, thermal management and manufacturing considerations. Taking the time to understand these complexities can result in high-quality rigid-flex PCBs that are both functional and reliable. Working with an experienced flex-PCB manufacturer as a partner throughout the design process will make it even easier to navigate these complex considerations and ensure that your final product performs as intended.