flex circuit support
The ability to juxtapose more components closer together allows a flexible circuit board to deliver a greater number of connections per unit area, leading to a smaller and lighter device. A flexible circuit is also more flexible than a rigid PCB, allowing it to bend and twist without damage, which is particularly useful for devices that will be handled. A flex circuit can also carry more current than a traditional PCB, which is important in applications that require high-speed data transfer.
To achieve the desired flexibility, the copper layer of a flex circuit is typically etched and then bonded to a thin polyimide or liquid photoimageable (LPI) coverlay. The coverlay protects the conductive pattern and is also laminated to provide stiffening. This is done in order to ensure that the flex circuit maintains its shape when subjected to stress or vibration.
Flex circuits can be single-sided, double-sided or multi-layered. Regardless of the layer count, the flex circuit must have a solid foundation that can support bending and other mechanical stresses. It can be designed using a variety of materials, including rigid and FR-4 base materials as well as copper foils. These materials can be either rolled or etched, with a range of thicknesses available to meet specific design requirements.
How does flex circuit support higher pin count components?
When it comes to routing traces, the best approach is to route them perpendicularly through the flex areas. This minimizes the amount of plated copper that is exposed to the flex areas and reduces the potential for failure due to excessive stress on the flex area. While copper is the most commonly used material for traces, specialty metals are often available as well for specific attributes such as corrosion resistance or spring properties.
Solder points and solder pads must be a minimum of 100 mils away from the flex area. This is because solder, whether leaded or lead-free, is a rigid material that is not intended to bend or flex. If these points are allowed to come into contact with the flex area, they will likely fail prematurely due to the stress on the solder joint caused by the mechanical flexing of the flex circuit.
A flex circuit must be designed with the same considerations for signal integrity as a traditional PCB, which means that it should be plated and soldered using IPC standards. It should also include a flex circuit legend and label that clearly indicates the flex portion of the circuit.
The last component of a flex circuit is the connector system, which must be selected to match the specific requirements of the device. The majority of flex circuits use ZIF connectors because they are widely used in all segments of the electronics industry and can accommodate a wide range of current levels and pin counts. However, custom connector systems can be developed to meet the unique needs of any device. If you are ready to develop a flex circuit, contact your preferred fabricator today. They can provide you with a quote for your project and will work with you to select the right materials and fabrication process to achieve your goals.
