Reducing Electronic Product Assembly Expenses with Flexible-Rigid Designs
In the world of electronics, rigid-flex Printed Circuit Boards (PCBs) have become a popular choice due to their versatility and numerous benefits. This article outlines key factors to consider when designing rigid-flex PCBs to minimise costs while maintaining quality.
Rigid-flex PCBs, a combination of rigid and flexible technologies, offer several advantages over traditional PCBs. They permit better airflow and heat dissipation, have lower assembly costs, less overall susceptibility to assembly errors, and simplify the testing procedure.
One of the primary cost-saving strategies is optimising layer count. Reducing the number of layers significantly lowers fabrication expenses; consolidating routing to fewer layers can cut costs by 10-15% per board[1].
Another crucial factor is using standard components and sizes. Selecting widely available, standard-sized components (e.g., 0805 or 0603 resistors) avoids costly custom parts, reduces procurement delays, and can cut component costs by up to 20%[1][2].
Simplifying trace layouts also contributes to cost savings. Employing wider traces (e.g., 6-8 mils for power lines) and larger vias (e.g., 12 mils) facilitates manufacturing and reduces defect rates and rework costs[1].
Design for Manufacturability (DFM) is another essential aspect. Managing mechanical stresses around interconnects with techniques like pad reliefs and tear-drop vias improves yield and reliability without increasing cost[4].
Optimising PCB size and panelization is another cost-saving measure. Fitting designs efficiently on standard panel sizes (e.g., 18x24 inches) increases yield per panel by up to 30%, reducing per-unit costs[1][3].
Selecting cost-effective base materials is also vital. Using commonly used substrates like FR-4 where possible, as specialized materials (e.g., PTFE) substantially raise material cost. Also, avoiding unnecessarily thick substrates saves raw material expenses[3][5].
Balancing flexibility and durability is crucial in flex sections. Controlling layer count and using appropriate stiffeners carefully maintains required bending without overengineering the board, which adds cost. Adhesiveless constructions can improve reliability and allow thinner, potentially cheaper builds in flexible areas[5].
Component placement and assembly considerations also play a role. Positioning large packages to minimise board warpage and avoiding complex mechanical fastening by using surface-mount packages with integrated heat sinks simplifies assembly and reduces cost[2].
In addition, several specific design considerations are worth noting. 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.
In rigid-flex designs, hole to flex distance is important. Avoid going below 50 mils for high-reliability applications. Keep in mind the rule most broken in rigid-flex designs: most manufacturers will not allow less than 30 mils for commercial applications.
Flex sections in rigid-flex PCBs offer 360-degree bendability, superior resistance to vibrations, compact and lightweight design, small flexible cables, and the ability to be warped or contorted without breakage.
Using rigid laminates instead of additional no-flow prepregs can help achieve a specific overall thickness at a lower cost. 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.
In conclusion, cost savings arise mainly from reducing layer complexity, using standard components, streamlining mechanical design for manufacturing, choosing appropriate materials, and efficient panelization. These measures collectively reduce material, processing, assembly, and yield losses in rigid-flex PCB production[1][3][4][5].
[1] "Design for Manufacturing (DFM) Best Practices for Rigid-Flex PCBs." Altium, 14 Mar. 2019, www.altium.com/design-center/pcb-design/design-for-manufacturing-dfm-best-practices-for-rigid-flex-pcbs.
[2] "Rigid-Flex PCB Design: Cost Savings Strategies." MacDermid Alpha Electronics Solutions, www.macdermidalpha.com/resource-center/rigid-flex-pcb-design-cost-savings-strategies.
[3] "Rigid-Flex PCB Design: Tips for Cost Reduction." TTM Technologies, www.ttm.com/resource-center/rigid-flex-pcb-design-tips-for-cost-reduction.
[4] "Design for Manufacturing (DFM) Guide for Rigid-Flex PCBs." Cadence Design Systems, www.cadence.com/content/design-for-manufacturing-dfm-guide-for-rigid-flex-pcbs.
[5] "Rigid-Flex PCB Design: Cost-Effective Strategies." I-Connect007, www.iconnect007.com/article/rigid-flex-pcb-design-cost-effective-strategies.
Rigid-flex Printed Circuit Boards (PCBs) can save costs by optimizing layer count, reducing the number of layers lowers fabrication expenses and consolidating routing can cut costs by 10-15% per board. Additionally, using technology like controlled impedance can improve design for manufacturability (DFM) and yield, which in turn reduces costs and increases reliability without adding significant expense.
