PCB Fabrication Assemblies Perform in High-Flexure Applications
The ability to assemble flexible printed circuit boards (PCBs) that can maintain integrity and functionality even under high-flexure conditions is rapidly expanding the potential applications of these advanced components. The performance of flexible PCBs largely depends on the design choices made during fabrication. For example, the use of materials with high coefficients of thermal expansion and good tolerances for bending are key factors. Specifying the right fabrication parameters and components for your flex PCBs is also important to maintain high yield rates.
The pcb fabrication assembly process starts with the purchase of raw bare circuit boards from a contract manufacturer. CMs usually have a list of preferred fabricators and will choose one that can best meet the technical requirements for the project. The bare board will undergo the standard processes of lamination, etching and drilling before being drilled and copper-plated to create the connections between layers.
After the etching and drilling process, a layer known as brown oxide is applied to the copper. This helps to ensure the copper foil bonds with the epoxy resin pre-preg properly. Then a post-etch machine called an optical punch is used to align the layers using the registration holes. Next, the PCB is exposed to x-rays for alignment and to check for the proper location of vias and through-hole components. If the flex PCB will be bending under load, stiffeners are added to specific areas of the board to support these areas and prevent them from cracking or peeling. Stiffeners are typically made of a polyimide or FR4 material and attached with a thermally-cured acrylic or pressure-sensitive adhesive.
How Flexible PCB Fabrication Assemblies Perform in High-Flexure Applications
In addition to stiffeners, a protective coating may be applied over the flex PCB to protect it from environmental threats like moisture and abrasion. After this, components are picked and placed on the flex circuit assembly by automated assembly machines and then the entire unit enters a reflow oven. The temperature profile melts the solder paste, attaching and electrically connecting the components to the flex circuit assembly. Finally, the assembled flex PCB is coated in an epoxy to provide mechanical and chemical protection for a long lifespan.
As a final step, the flex PCBs go through electrical testing and inspection to verify connectivity, isolate defects and confirm that they have been fabricated according to the design specifications. If necessary, additional processes like contour milling and 3D shaping can be employed to achieve complex flex shapes. After inspection and reworking, the flex circuit assemblies are packaged and shipped to the customer.
As with rigid boards, a comprehensive testing and documentation suite is essential for maintaining high PCB quality and a seamless fabrication/assembly process. The final products are used in a variety of electronic applications ranging from wearable technology to smart home devices. Regardless of their application, all these products must be manufactured with a high degree of precision and reliability to deliver the performance required by their users. To do this, manufacturers must take advantage of the latest innovations in flex circuit fabrication and assembly technologies.