assembly process for a rigid flex PCB
The assembly process for a rigid flex PCB involves the same steps as that of a conventional rigid PCB. However, rigid-flex boards have a flexible section that can bend and twist to accommodate a product’s shape. To reduce the stress on these flex sections, it’s crucial to consider the placement of rigid and flex components and connectors during the design phase. Failure to do so can result in a mechanical stress that impacts circuit performance and reliability.
Rigid flex PCBs are also characterized by the presence of stiffeners that provide additional support in critical areas of the board. These stiffeners help protect the flex section from damage during manufacturing and assembly. Stiffeners can be applied in a variety of ways, including by screen printing or by using photo-etching to imprint the required pattern. Regardless of the method, the stiffeners must be laminated to ensure their integrity.
A rigid flex pcb may have a single or multilayer stackup, and the structure can range from simple to highly complex. The most basic rigid flex PCB has a single-sided, double-plated copper layer with through holes and high-density interconnect (HDI). More advanced rigid-flex PCBs feature multiple layers of flexible material with or without shields or stiffeners, plated through holes and HDI.
What is the assembly process for a rigid flex PCB?
To fabricate a rigid-flex PCB, the fabricator starts with a base material such as FR4 or a similar substrate. A layer of adhesive or adhesiveless cladding is then laminated on top. The cladding is used to bond the copper layer to the base material, which is typically made of a woven fiberglass cloth with an epoxy resin binder that’s flame resistant.
Once the copper is bonded to the base material, it’s etched and drilled. The etching and drilling processes require the use of harsh chemicals, which adds to the overall cost of a rigid-flex PCB. In addition, the selective plating process can cause delays due to the need for a separate mask for each individual layer.
After the etching and drilling processes, the flexible portion of the rigid-flex PCB is laminated to the final assembly panel. This step requires precise alignment to prevent the flex section from warping or stretching during the reflow oven process. The final assembly panel must also include borders for framing the flex area, so the flex circuit stays flat during the final fabrication and assembly stages.
The aforementioned factors can increase the cost of a rigid-flex PCB, but careful consideration of these variables can lower the price. For example, reducing the layer count can decrease costs by lowering the number of drilled holes and avoiding unnecessary layers of copper. Also, minimizing the need for selective plating and multiple surface finishes can save money by reducing material waste. Finally, ensuring that the rigid and flexible sections of the PCB are properly aligned can reduce assembly time and increase the speed at which the PCB is ready for shipment to customers.
