PCB Manufacturers Work With Flexible Circuits
A flexible circuit is a printed circuit board that can be bent or folded without damaging its connections. It is used to replace bulky wires and cables that add weight and complexity to the product. In addition, a flexible circuit reduces assembly time and the cost of production.
A flex circuit is made of several layers of copper laminate with insulating materials between each layer. Signals are routed through these layers using holes drilled into the insulating material. This makes a flex circuit much thinner than traditional rigid circuit boards. These thinner boards also offer better electrical properties. This allows a pcb manufactures to design smaller products and add more features than would be possible with a rigid PCB.
The base raw material used in a flex circuit is either Poyester (PET), adhesive Polyimide, or both. The copper plating process is either panel or pad-only (button). Panel plating uses copper on both sides of the flex circuit. This increases etch yields and allows for more complicated traces and better control of copper thicknesses. However, it can cause stresses on the copper traces when the flex is bent or folded, which can result in l-beaming. The bending of a flex circuit should be done at a large radius, and conductor traces should be run straight or curved rather than angled to prevent stress.
How Can a PCB Manufacturers Work With Flexible Circuits?
Stiffeners are often added to a flex circuit for additional support, especially in connection areas. FR4 or polyimide stiffeners can be placed in the center of the flex to increase strength and reliability. They can also help to reduce the flexing of the circuit and make it easier for you to solder connections.
In addition to the insulating materials, a flex circuit can contain shielding for electromagnetic interference. This can be particularly helpful in electronic devices that are sensitive to interference. This can reduce noise and help you control the impedance of your signal lines.
A pcb manufactures can work with you to determine if a flexible circuit is the right option for your application. The manufacturer will take into account the type of flex, how many layers are needed, and the desired bend radius. The flex circuit should be designed according to IPC standards. Specifically, the density priority principle should be followed to begin wiring the components at the top of the circuit. This ensures that critical signals are wired first, and that they will be less likely to experience failure or malfunction in the long run.
During manufacturing, a flex circuit is exposed to UV light through a photomask. This process enables the pattern to be transferred onto the insulating material. Then, the photoresist is etched to create the desired circuitry on the surface of the substrate. During this step, it is important to keep the area around the bend free of discontinuities like vias, cutouts, and slits. This helps to minimize stress and cracking on the flex circuit that can cause malfunctions and failures. It is recommended to stagger the buried and blind vias on a flex circuit as well.
