How to Reduce Rigid Flex PCB Costs

What Are Rigid-Flex PCBs?

Rigid-flex PCBs represent a hybrid construction technology that merges the robustness of rigid PCBs with the versatility of flexible circuits. This innovative combination results in PCBs that can be designed to fit into the most challenging spaces, providing unparalleled design freedom. Unlike traditional rigid boards, rigid-flex PCBs can bend, fold, and flex, making them an ideal choice for dynamic or spatially constrained applications.

The applications of rigid-flex PCBs span across various high-tech industries, reflecting their adaptability and the critical role they play in modern electronics:

• Consumer Electronics: In the realm of consumer gadgets, rigid-flex PCBs are pivotal in designing compact, lightweight devices such as smartphones, wearable tech (like smartwatches and fitness trackers), cameras, and portable electronics. Their ability to conform to tight spaces and complex shapes allows for more innovative product designs.
• Medical Devices: The medical industry benefits significantly from the application of rigid-flex PCBs, especially in creating small, reliable devices that can withstand the rigors of medical use. Examples include portable medical monitors, diagnostic equipment, and advanced prosthetics. The flexibility and durability of these PCBs make them suitable for both external and implanted devices, where reliability and compactness are critical.
• Automotive Industry: Rigid-flex PCBs are increasingly used in automotive electronics, where they contribute to the sophistication of vehicle systems. From dashboard displays and controls to sensors and electronic modules for engine management, infotainment systems, and safety features, rigid-flex PCBs offer the durability and reliability required in the demanding automotive environment.
• Aerospace and Defense: In aerospace and defense, the combination of light weight, high reliability, and the ability to withstand extreme conditions makes rigid-flex PCBs an excellent choice for spacecraft, satellites, military communication devices, and avionics. Their use in these applications ensures that critical missions have the support of electronics that can endure the stresses of launch, flight, and the harshness of space or battlefield environments.
• Industrial Applications: Rigid-flex PCBs also find their place in industrial applications, including robotics, manufacturing equipment, and sensors. Their durability and flexibility are advantageous in environments subject to vibrations, frequent movements, and the need for precise control and monitoring.

Why Are Rigid-Flex and Flexible PCB Expensive?

Manufacturing Difficulty

1. Complex Fabrication Process: Rigid-flex PCBs require a sophisticated fabrication process that combines the manufacturing techniques of both rigid and flexible PCBs. This complexity begins with design and extends through layer stacking, lamination, and the precise alignment of the rigid and flex parts. Each step must be executed flawlessly to maintain the integrity and functionality of the PCB, necessitating advanced equipment and skilled labor.

2. Specialized Materials: The materials used in rigid-flex PCBs, such as polyimide for the flexible layers, are more expensive than those used in standard PCBs. These materials are chosen for their durability and flexibility, but their cost is significantly higher, contributing to the overall expense of the PCB.

3. Precision and Waste: The precision required in cutting and aligning the flexible parts of the PCB leads to a higher scrap rate compared to traditional rigid PCBs. The waste material, particularly of the more expensive flexible substrates, adds to the manufacturing costs.

4. Testing and Quality Control: Due to the complex nature of rigid-flex PCBs, testing and quality control are more rigorous and time-consuming. These PCBs often undergo additional inspections and tests to ensure that they meet the high reliability required by their applications, further increasing production costs.

Rigid-Flex PCB Market Dynamics

1. Niche Market: Rigid-flex PCBs cater to a niche market, primarily used in high-end applications where performance and reliability are critical. The demand in these markets—such as aerospace, medical devices, and advanced consumer electronics—supports higher prices due to the specialized requirements of the products.

2. Limited Manufacturer Pool: The complexity of manufacturing rigid-flex PCBs limits the number of suppliers capable of producing them to the required standards. This limited competition can keep prices higher, as fewer manufacturers possess the expertise and equipment necessary to produce high-quality rigid-flex PCBs.

3. Customization and Low Volume: Many rigid-flex PCBs are custom-designed for specific applications, leading to lower production volumes compared to standard PCBs. The custom nature and lower economies of scale increase the per-unit cost, as manufacturers must recoup their investment in design, setup, and manufacturing over a smaller number of units.

4. Technological Advancements: The rapid pace of technological advancement in sectors that commonly use rigid-flex PCBs requires continuous investment in research and development by manufacturers. This investment, necessary to stay competitive and meet the evolving needs of high-tech industries, contributes to the higher costs of rigid-flex PCBs.

Factors Affecting Rigid-Flex PCB Cost

Material Selection’s

The most common base material for the flexible part of a rigid-flex PCB is polyimide due to its excellent thermal stability, flexibility, and electrical properties. An alternative, cheaper material might be polyester, which also offers good flexibility but with lower thermal resistance and durability.

Layer Count

Each additional layer requires more substrate material, conductive (copper) layers, and prepreg (the bonding material between layers), directly increasing material costs.

More layers necessitate additional steps in the manufacturing process, including lamination, drilling, plating, and etching for each added layer. These steps increase the time and complexity of production, leading to higher labor and overhead costs.

Size and shape

The most direct impact of the PCB size is on the amount of material required. Larger PCBs use more substrate material, conductive layers (such as copper), and protective coatings, directly increasing the material cost.

Larger PCBs can also require special handling and processing steps, further adding to the cost. For example, larger boards may need additional support during the manufacturing process to prevent warping or damage, and they may also incur higher costs for inspection and testing.

Irregular shapes or designs with intricate cutouts and contours can increase manufacturing complexity. Specialized cutting and machining processes are often required to achieve non-standard shapes, increasing production time and costs.

Custom shapes might require unique tooling or fixtures, leading to higher setup costs. These costs are especially significant for low-volume runs where the setup costs are a larger proportion of the overall manufacturing expense.

The efficiency of panelization is also affected by the PCB’s shape. Standard rectangular boards can be easily arranged to maximize panel usage, reducing waste. In contrast, irregular shapes may leave unused spaces on the panel, which cannot be used for other PCBs, thus increasing the per-unit cost.

Special Features

Impedance Control:
Ensuring impedance control requires precise calculations and adjustments to the PCB’s geometry (trace width, spacing, and dielectric thickness) and material properties. This precision level often necessitates additional design time, specialized materials, and testing to verify compliance with the required impedance values.

Blind and Buried Vias:
These vias connect internal layers without going through the entire board (blind vias) or connect two or more internal layers (buried vias), enabling more complex designs without increasing the PCB size. Manufacturing them involves additional drilling and plating steps, which must be precisely aligned across multiple layers.

High-Density Interconnects (HDI):
HDI technology allows for a higher density of components on a PCB by using smaller vias and pad sizes. While HDI can significantly increase the functionality of a PCB in a smaller space, it requires advanced manufacturing techniques, including laser drilling and fine-line etching.

Tips for Reducing Rigid Flex PCB Costs

1. Optimize PCB Layer Count and Design:

Aim to use the minimum number of layers that meet your design requirements to reduce material and processing costs.
Design with standard materials and processes in mind to avoid premium charges associated with custom solutions.

2. Material Selection and Utilization:

Select standard materials that offer a balance between performance and cost. Consider lower-cost alternatives for stiffener materials when feasible.
Optimize board size to minimize waste and material costs. Design boards to fit standard panel sizes and maximize material utilization.

3. Panelization and Board Design:

Efficiently build panels to include as many boards as possible, reducing waste and improving the cost-effectiveness of each production run.
Adjust your layer stackup to conform to standard thicknesses, simplifying manufacturing processes and reducing costs.

4. Production and Ordering Strategies:

Be flexible with lead times; longer lead times can often secure better pricing from manufacturers.
Order in larger quantities to take advantage of volume discounts, reducing the per-unit cost significantly.

5. Design for Manufacturability (DFM) and Assembly:

Focus on ease of manufacture and assembly to reduce production complexities and associated costs. Simple designs are generally less expensive to produce and assemble.
Engage with your PCB manufacturing partner early in the design process to benefit from their expertise in cost-saving measures and DFM practices.

6. Proactive Design Review and Collaboration:

Request design reviews from your PCB manufacturer to identify potential cost reduction opportunities before finalizing the design.
Collaborate closely with your manufacturer to ensure that your design aligns with their capabilities and material availability, avoiding costly last-minute changes.