flex PCBs benefit electronic devices

The flexibility of flex PCBs allows for more compact and lightweight electronic devices. They’re especially useful for consumer electronics like smartphones, tablets, and fitness wearables. Flex circuits provide the critical interconnections for these products and enable them to bend, twist, and endure rigorous physical movement without breaking. However, a number of factors affect flex circuits’ performance and durability. Understanding these factors can help you select the right flex circuit for your design.

The flex pcb used in smartwatches and fitness trackers rely on flex PCBs to connect the displays, sensors, and internal components. These flex circuits allow these products to bend freely around the wrist and handle continuous bending and stress without suffering any breakage. Likewise, flex circuits in satellites and aircraft require the ability to bend repeatedly while remaining intact. As the technology behind these devices continues to evolve towards sleeker form factors, flex circuits will remain an important ingredient for many applications.

A key factor in determining how durable or fragile a flex circuit is is its material composition. Most flex circuits are made from polyimide or other thin dielectric film substrates. These materials are very conductive and also act as an insulator to protect the copper traces from environmental damage and other stresses. A thin, flexible coverlay is then laminated over the conductor layer to further insulate it and provide protection.

How does the flexibility of flex PCBs benefit electronic devices?

In multilayer flex circuits, additional dielectric stiffening layers can be added to reduce wrinkling or buckling during fabrication. These additional layers are typically laminated to the substrate using a high-temperature epoxy or acrylic adhesive. A solder mask is then applied to the conductor pattern for insulation and oxidation prevention. Finally, a finish such as Electroless Nickel Immersion Gold (ENIG) is applied to the exposed copper for solderability and corrosion resistance.

One of the biggest challenges for designers is matching the impedance of flex circuits with their signal transmission requirements. This process involves calculating and setting the required conductor width, signal path lengths, and the distance between signals in different layers of the board. These parameters must be carefully controlled to ensure that the flex circuit performs as intended.

Another consideration is the flex circuit’s operating environment. For example, a dynamic flex circuit that bends regularly requires a lower bend radius than a static flex circuit that’s only bent once during assembly. Additionally, the flex circuit must be able to withstand repeated flexing, vibrations, and thermal shock.

To minimize the risk of failure, your flex circuit design should consider these factors early on. Your engineering and design teams should also work closely with your manufacturer throughout the process to avoid expensive errors. The best way to ensure that a flex circuit meets your design requirements is to use a rigid-flex PCB design tool that incorporates a comprehensive set of tools and processes into a single, seamless software package. Altium Designer is the only design software that provides these capabilities and enables your team to collaborate effectively with your manufacturing partner at every stage of the process.