role do flex PCBs
A flex PCB is a flexible circuit board with conductors that are bonded to the substrate using an adhesive or, gaining popularity, non-adhesive construction. It is often surrounded by dielectric layers and has plated through holes (PTH) which connect the copper to other components. It can also have openings for access to lower level features which may be necessary in certain applications. The conductive paths are created using lithographic procedures and a dielectric material such as polyimide is typically used. A flex circuit can be manufactured with multiple layers of copper and/or various thicknesses of dielectric materials depending on the application’s requirements.
Rigid flex is one of the most common and highest performance types of flex pcb. It combines the best of rigid and flex circuits, providing superior reliability and quality and allowing for larger component packages that can be mounted in tight spaces. Rigid flex circuits are most commonly used in high-reliability, high-density applications, such as automotive and medical devices.
The conductive paths in a flex circuit are created on the metal layer, called a copper foil, using lithographic methods. The resulting copper foil is then bonded to the dielectric material, which in most cases is a thin layer of polyimide. A solder mask is then applied to protect the conductor pattern and prevent oxidation during assembly, and the finished product is usually treated with hot air solder leveling or similar techniques.
What role do flex PCBs play in electronic textiles?
The most basic flex circuits, single-sided flex circuits, feature a single layer of copper on one side and are only partially insulated from each other by the dielectric material. They are ideal for smaller designs and can be made much faster than multi-layer flex circuits. They are also more affordable, making them an attractive choice for low-volume production runs and for clients who are looking to cut costs.
While there are many different ways to construct a flex circuit, the most popular method is with a copper-clad laminate (CCL). This is because it offers an excellent balance of flexibility, tensile strength and electrical performance. In addition, it can be reliably etched, which is an important consideration for the high-speed electronics that flex circuits are used in.
A flex circuit’s physical flexibility is what allows it to be shaped into three-dimensional shapes for use in electronic textiles and eliminates the need for ribbon cables. This provides the wearables with an added degree of flexibility, while also providing them with a higher conductor density than traditional hardwired cables could ever provide.
Another important benefit of a flex circuit is that it can be washed without damaging the key electrical components, unlike traditional ribbon cables. This is especially useful for wearable sensors or actuators that need to be able to resist repeated exposure to water to maintain their working condition. In a washable flex circuit, these components can be connected via detachable connections that are easily removed for washing and can be reattached afterward to ensure the sensor or actuator is still in working condition.