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Crucial Factors of Flexible PCBs: Design Considerations and Guidelines

 Mar 18, 2021

Flexible PCBs

Flexible PCBs are a part of several electronic devices. In fact, owing to the benefits like bendability, lesser assembly cost and time, point-to-point wire connections and scope for replacement, etc, these flexible PCBs are widely used in several industrial electronics. However, out of all the benefits, the design flexibility of flexible PCBs is the most significant one. A well-designed flex PCB can offer durability, functional flexibility, ease of installation, etc. Therefore, to design the flexible PCBs in an efficient manner, a few crucial factors must be considered. This post discusses the design considerations and a few guidelines to follow while designing and fabricating high-quality flexible PCBs.

6 Must-Know Design Considerations of Flex PCBs

Consideration of the following factors can enhance the efficiency of flex PCBs.

  • Bendability: Each flex PCB is designed for a calculated bend radius. The bend radius of flex PCBs depends on the number of layers, the flexibility of the material, etc. Considering the bendability of flex PCBs defines the scope of operation of these PCBs. Several applications demand the high-flexibility of the PCBs, in certain cases, bendability becomes a crucial factor.
  • Features of Bend Radius: The features like slots, cutouts, mounted components, etc should not be located on the bend radius. Therefore, while designing, the bend radius and stressed areas must be taken into consideration while designing and allocating the features.
  • Material: To achieve a specific amount of flexibility, a suitable material must be chosen. Often the materials used for the flexible PCBs have low to moderate dimensional stability. Therefore, the material that can sustain the size and shape of PCBs without reducing the flexibility must be chosen for manufacturing flex PCBs. However, based on the material, slight modifications to the design may be needed. These design modifications may include inserting spurs, anchors, etc to stabilize the material layers.
  • Trace Routing: The circuitry on the flex PCBs is a complex task to accomplish. The higher the bend radius is, the lesser is the stresses introduced on the board. Since the traces of mounted components, vias, etc must run through the low-stress regions to gain safety in the PCB design. Trace routing helps in preventing electrostatic discharge in the PCBs. This can eventually help in preventing short-circuits.
  • Flex PCB Layer Stacking: Since multiple layers are stacked over one another in a flex PCB, strategic layer stacking is important. The most flexible layers must be stacked at the center to avoid layer slippage.
  • Risk of Delamination: Delamination (detachment of layers) is a frequent problem faced in PCB fabrication and applications. The layers often delaminate from each other causing abrupt damage to the circuitry and sometimes the PCBs fail entirely. To prevent delamination, appropriate solder paste application must be followed. The solder paste material must be chosen according to the requirements for flexibility. The features like anchors must be introduced to the design so that delamination is prevented.

Considering the above-mentioned factors, the efficient design of flexible PCBs can be accomplished. However, testing for quality control is essential for ensuring the efficiency of the flex PCBs. The testing guidelines stated in the following industrial standards can be adopted to ensure the efficiency of flex PCB design.

  • IPC-2223: This industrial standard offers guidelines for material selection, adhesive selection, and interface selection for sectional flex PCB designs. A few guidelines about flex vias are also introduced in the same.
  • IP-FC-234: This standard includes testing guidelines for the flex PCBs.
  • IPC-6013C: This standard offers guidelines for performance specifications for flexible PCBs.

Considering these standards, the flex PCBs can be tested for efficiency and performance. You can be assured of quality and performance only when you partner with trusted PCB manufacturers such as Accelerated Assemblies. The company offers high-quality flex PCB manufacturing services along with PCB testing and inspection services.