Flex PCBs
A flexible printed circuit board is a patterned arrangement of copper features on a base material that is flexed during assembly. It is a more durable and reliable alternative to wire harnesses, which are susceptible to failure from vibrations and harsh environmental conditions. Flex PCBs are used in a wide variety of electronics including mobile devices, laptop computers, and tablets. They are also used in medical and automotive devices as well as aerospace applications. The key to success in a flex PCB is achieving the right balance of bending and stress tolerance with design and operating requirements.
Flex PCBs can be made with either a rigid or a semi-flexible substrate, and are designed to accommodate both dynamic bending and static bending. They are ideal for use in harsh environments where a more durable circuit board is required. They can be flexed many times without failing, and are highly tolerant of solder reflow cycles, temperature fluctuations, and other stresses. In addition, flex pcbs are designed to withstand a high degree of vibration.
The choice of material for a flex circuit board is critical to its long-term performance. It should be a thermosetting adhesive film such as polyimide, which stays flexible after heating and provides good resistance to moisture and tears. Choosing an upgraded version of this material is especially beneficial, as standard PI film does not provide adequate moisture resistance and is prone to tearing and failure.
What Are Flex PCBs?
A rigid-flex PCB can be assembled using an acrylic or epoxy adhesive, and should be placed in an autoclave to ensure a strong bond between the board and the substrate. It is also important to avoid placing vias, cutouts, or slits in the bend area as these can weaken the overall structure and cause traces to break. It is best to use a narrower trace width to minimize the number of points in the bend area. This will prevent stress and cracking of the copper, and reduce the risk of failure.
RF/EMI shielding can be incorporated into a flex circuit board by stitching or welding a copper layer onto the substrate. This helps to limit noise, protect the circuit board from damage, and meet EMI and regulated impedance requirements. Alternatively, cross-hatching can be used to create the same effect while providing greater flexibility and lower copper thickness.
Flex circuits have several benefits over traditional wire harnesses, including higher reliability and space savings. They are able to withstand high temperatures and bending, and can eliminate the need for wire connections in the device, eliminating the chance of failure due to corrosion or poor connections. This allows the circuit to be designed in a more compact and portable package, while reducing costs by eliminating the need for connectors. This makes a flex circuit the preferred solution for many demanding electronic products. This technology is becoming increasingly common in many industries, such as the aerospace industry, IoT, and wearables. This is because it enables 3D connectivity, which can increase device functionality while reducing weight and size.
