Reduced Expenses in Electronic Product Manufacturing via Flexible Rigid Assembly
Rigid-flex Printed Circuit Boards (PCBs) are a combination of rigid and flexible technologies, where one or more flex circuits connect sub-circuits in rigid PCBs. These boards offer several advantages, including 360-degree bendability, superior resistance to vibrations, compact and lightweight design, and improved airflow and heat dissipation.
To minimize the cost of rigid-flex PCB design, several strategies can be employed.
Simplify Bend Zones
Reducing the number of bend areas is crucial as each requires precise alignment and increases processing costs.
Minimize Vias
Limit or replace costly microvias and blind vias with standard through-hole vias where possible. Using larger via sizes when signal integrity permits also lowers drilling costs.
Use Standard Materials and Thicknesses
Employing commonly available material thicknesses and copper weights can avoid custom orders and expensive plating. High-performance or specialized materials significantly increase cost.
Optimize Panelization
Design PCBs to fit standard panel sizes to maximize material utilization and reduce waste.
Reduce Layer Count
Keeping the number of layers to the minimum required can reduce processing steps, materials, and complexity.
Design for Testability
Include accessible test points to streamline quality control and reduce testing time and labor.
Perform Early DFM Reviews
Consult with manufacturers early to identify design changes that improve manufacturability and lower costs.
In addition to these strategies, there are specific design considerations for rigid-flex PCBs.
Flex Sections
Flex sections in a rigid-flex PCB are built using unreinforced substrates made up of polyimide dielectric film cladded with rolled copper. The flexible section provides 360-degree bendability and is generally multi-layer circuits.
Drill to Copper Clearance
Drill to copper should be 10 mils in rigid-flex designs, and it is very important.
Annular Rings and Transitions
Annular rings should be as large as possible in flex-only regions to reduce the risk of peeling, and the transition from the annular ring to the trace should be teardrop-shaped for the same reason.
Hole to Flex Distance
Hole to flex distance is important in rigid-flex designs, with a minimum of 50 mils for high-reliability applications. Most manufacturers will not allow less than 30 mils for commercial applications.
Traces and Folds
Traces should always be perpendicular to the fold in the flex areas that will be bending. Where flex ribbons have sharp interior corners, tear stops should be added. Traces in the flex area should be curved, not angled, to increase peel strength.
Materials and Components
The PCB material used in flex sections can be just a few microns thick but can be reliably etched. No flow prepregs are one of the most critical components in rigid-flex manufacturing, preventing the flow of epoxy resin onto the flexible sections of the PCB.
Using rigid-flex PCBs can lead to direct cost savings due to reduced Bill of Materials and inventory. Additionally, indirect cost savings come from reduced assembly costs and improved reliability.
In conclusion, by implementing these strategies, designers can significantly reduce production expenses without compromising board functionality. It is essential to consult with manufacturers early in the design process to optimise these strategies for the specific needs of the project.
[1] Designing Rigid-Flex PCBs for Cost-Effective Manufacturing [2] PCB Design for Manufacturing: 7 Strategies to Reduce Costs [3] Designing Rigid-Flex PCBs for Cost-Effective Manufacturing
Controlled impedance technology is essential when designing flexible sections in rigid-flex PCBs to maintain consistent signal integrity throughout the board.
Incorporating cost-efficient controlled impedance technology during the design phase can lead to substantial savings in the overall manufacturing costs of the rigid-flex PCB.
