Flexible PCBs (made up of only flexible elements) excel in applications with space constraints and continuous movement. Whereas rigid flex PCBs (incorporating both flexible and rigid elements) are preferred for complex 3D designs and applications demanding a balance between flexibility and structural stability. So, choosing between flexible and rigid-flex PCBs depends on the electronic application’s specific needs, with each type offering unique advantages.
Let’s discuss in detail, exploring which one is ideal for your project.
| Aspect | Flexible PCBs | Rigid Flex PCBs |
| Construction | Entirely flexible materials, allowing bending and twisting | Combination of flexible and rigid substrates |
| Flexibility | High flexibility, suitable for bending and dynamic movement | Perfect balance between flexibility and structural stability |
| Space Efficiency | Ideal for tight space constraints | Offers space savings, especially in applications with both flexible and rigid sections |
| Durability | Enhanced durability due to reduced solder joints | Enhanced reliability, minimizing points of failure |
| Weight | Lightweight and thin, contributing to overall weight reduction | Balances weight reduction with structural stability |
| Applications | Best for space-constrained, dynamic environments | Suitable for applications requiring a combination of flexibility and rigidity |
| Design Freedom | Ideal for intricate shapes and 3D configurations | Allows for complex layouts, accommodating both rigid and flexible requirements |
| Interconnection | Minimizes connectors and solder joints, improving reliability | Reduces interconnect points, enhancing overall reliability |
| Manufacturing Complexity | Generally simpler manufacturing processes | Involves additional manufacturing complexities due to combining different materials |
| Cost | Can be cost-effective, especially for simpler designs | May involve higher manufacturing costs due to added complexity |
| Signal Integrity | Good for many applications, but may have limitations in high-frequency designs | Provides a stable environment for critical components, contributing to improved signal integrity |
Flexible VS Rigid Flex PCBs Fabrication
Flexible PCB manufacturers focus on producing entirely flexible circuitry using materials like polyimide or polyester. This is done to allow for bending and conforming to irregular shapes.
In contrast, Rigid-Flex PCB manufacturers start the fabrication integrating both flexible and rigid sections. This requires more complex processes such as bonding layers and through-hole plating, to combine flexibility with structural support.
Let’s get to the details.
| Manufacturing Steps | Flexible PCBs | Rigid-Flex PCBs |
| Substrate Preparation | Cut and size flexible substrate material (e.g., polyimide or polyester). | Cut and shape flexible substrate material to match design requirements. |
| Copper Cladding | Add copper layers to the substrate through processes like etching or deposition. | Rigid sections manufactured separately using standard PCB fabrication techniques. |
| Circuit Patterning | Create circuit patterns on copper-clad substrates using photolithography techniques. | Bond flexible substrate layers onto rigid sections using specialized adhesives. |
| Coverlay Application | Apply protective coverlay over conductive traces for insulation and mechanical protection. | Drill holes through the entire stack of rigid and flexible materials, then plate with conductive material. |
| Plating and Finishing | Apply surface finishes such as gold or solder to improve solderability and protect against oxidation. | Apply surface finishes and additional protective layers to ensure reliability and durability. |
Flexible PCBs Manufacturing Process
First of all, let’s understand how flexible PCB fabrication is carried out, from initial planning to the complete production and final inspection:
Step 1- Material Selection in flexible pcbs
Flexible PCB materials include polyimide or polyester films, prized for flexibility and temperature resistance. The flexible PCB manufacturers choose copper foils (with suitable thicknesses) for conductive layers, ensuring both ideal conductivity and flexibility.
Step 2 – Design Considerations for flexible pcbs
The flexible PCB design engineers consider factors such as bending radius, flexing cycles, and material properties to ensure the circuit can withstand intended applications without damage. They optimize the layout of components and traces to minimize stress concentrations. All while ensuring reliable electrical connections, especially in areas prone to bending or flexing.
Step 3 – Substrate Preparation for flexible pcbs
The flexible PCB manufacturers carefully cut and size the selected flexible substrate material according to the design specifications of the circuit board. They may also apply surface treatments to the substrate to enhance adhesion and compatibility with subsequent processing steps.
Step 4 – Copper Cladding
Consequently, they add the copper layers to the substrate to form the conductive paths of the circuit. This can be achieved through processes like laminating thin copper foils onto the substrate. They may do it by depositing copper using techniques such as sputtering or electroplating.
Step 5 – Circuit Patterning for flexible pcbs
When it comes to the desired circuit pattern, the flexible PCB manufacturers do it on the copper-clad substrate using photolithography techniques. For this, they apply a layer of photoresist to the substrate, exposed to UV light through a mask defining the circuit pattern, and then developed to remove the unexposed areas. All while leaving the patterned copper traces behind.
Step 6 – Etching
The flexible PCB manufacturers etch away the exposed copper areas using an etchant solution, leaving only the desired conductive traces on the substrate. Rest assured that this strips off the remaining photoresist.
Step 7 – Drilling of flexible pcbs
Since flexible PCBs require component mounting and interconnections between different layers of the circuit board, the manufacturers drill the holes through the substrate. They may use mechanical drilling or laser drilling techniques depending on the flexible PCB design requirements.
Step 8 – Coverlay Application
Eventually, they apply the protective coverlay over the circuitry to insulate the copper traces and provide mechanical protection. Keep in mind that the coverlay material, typically a flexible polymer like polyimide or liquid photoimageable solder mask (LPSM), is applied in a thin layer over the entire surface of the circuit board using lamination or coating techniques.
Step 9 – Plating and Finishing
Lastly, they apply surface finishes such as electroless nickel immersion gold (ENIG) or immersion silver to the exposed copper areas. This is done to improve solderability and protect against oxidation. Notably, additional finishing processes may include silk-screening of component designations and final inspection/testing to ensure quality and functionality.
Rigid Flex PCBs Manufacturing Process
Now, let’s move forward to discuss how flex rigid PCBs are manufactured:
Step 1 – Design Layout
Rigid Flex PCB manufacturers skillfully consider the integration of rigid and flexible sections to ensure a well-optimized design with utmost functionality and space utilization. They typically use CAD software to create the layout, allowing for precise placement of components and traces.
Step 2 – Rigid Board Fabrication
Rigid Flex PCB manufacturers commence fabricating the rigid sections of the PCB using standard PCB fabrication techniques. This involves substrate preparation, where the rigid material, often FR4, is cut and cleaned. After this, they apply copper cladding to the substrate using processes like lamination or electroplating. All while forming the conductive traces and pads.
Step 3 – Flex Material Preparation
Simultaneously, flexible materials such as polyimide are prepared for the flexible sections of the PCB.
They carefully cut and shape the flexible material to match the design requirements precisely, ensuring complete compatibility with the rigid sections.
Step 4 – Bonding Layers
Once the rigid and flexible sections are prepared, they are bonded together using specialized adhesives and bonding techniques. This bonding process creates a strong and reliable connection between the rigid and flexible materials, ensuring structural integrity.
Step 5 – Through-Hole Plating
The rigid flex PCB manufacturers add plated through-holes to establish connections between the layers of the Rigid-Flex PCB. They drill the holes through the entire stack of rigid and flexible materials. Afterwards, the holes are plated with conductive material to create electrical connections between layers.
Step 6 – Final Processing
The rigid flex PCB fabrication engineers apply surface finishes such as ENIG or HASL to improve solderability and protect against oxidation. They may apply additional protective layers to the PCB to safeguard against environmental factors like moisture and mechanical stress.
Finally, the board undergoes thorough inspection and testing to ensure it meets quality standards and functions as intended.
Flex VS Rigid PCB Cost Details
Flexible PCB Fabrication and Assembly Costs can range based on complexity, such as four boards may total approximately $3,945 (Board 1: $1,800, Board 2: $970, Board 3: $710, Board 4: $465) plus connectors and cabling at $33.
Rigid-Flex PCB Fabrication and Assembly Costs also range according to complexity, such as the flex layer fabrication is estimated at $1,690, with reductions in the cost of individual rigid sections by between 5 and 25% due to process step reductions.
However, it is recommended to discuss your PCB requirements with PCB manufacturers and get a personalized quote. Feel free to contact us for guidance.
| Cost Driver | Flexible PCBs | Rigid-Flexible PCBs |
| Tooling Costs | Can vary based on the complexity and custom requirements of the project. | Typically higher due to the additional complexity of integrating flex and rigid parts. |
| Material Costs | Dependent on the type of materials used, with a range due to varying foil types, thicknesses, and base film types. | Generally higher due to specialized materials for both rigid and flexible parts. |
| Manufacturing Costs | Influenced by the unique fabrication needs of flexible circuits. | May be higher initially but can offer savings in assembly and integration compared to separate PCB assemblies. |
| Assembly Costs | Assembly can be complex due to flexibility, potentially increasing costs. | Simplified by reducing the need for separate cable assemblies and connectors, potentially lowering overall costs. |
| Testing and Reliability | May require more rigorous testing due to unique designs, affecting costs. | Increased reliability and durability can lead to long-term cost savings despite possibly higher initial testing costs. |
| Design Costs | Custom designs may increase costs. | A single design that integrates multiple functionalities reduces overall design costs. |
| Long-term Costs | May incur higher replacement or repair costs over time. | The robustness and integration can result in lower maintenance and longer lifespan, offering long-term savings. |
Frequently Asked Questions
How is flexible PCB fabrication different from rigid PCB fabrication?
Flexible PCB fabrication involves similar steps to rigid PCB fabrication but requires additional considerations for the flexible nature of the materials. For example, careful handling to prevent damage and specific techniques for layer bonding and etching.
How a quick turn rigid flex PCB is manufactured?
A quick turn rigid flex PCB is a type of printed circuit board that combines both rigid and flexible technologies. Its manufacturing starts by selecting polyimide and FR4 materials, etching circuit patterns, drilling vias, and plating for conductivity. Technicians laminate layers with special adhesives to combine rigid and flexible parts. They may expedite the process through advanced machinery and strict quality control.
What are flexible PCB connectors?
Flexible PCB connectors are specialized connectors designed to connect flexible PCBs to other electronic components or boards. They are tailored to accommodate the flexing and bending of the PCB without causing damage or disconnection.
How do I choose a flexible PCB manufacturer?
When you choose a flexible PCB manufacturer, make sure to consider their experience, manufacturing capabilities, quality certifications (such as ISO 9001), turnaround times, and customer service. It’s also beneficial to review their portfolio and customer testimonials.
Are flexible PCBs more expensive than rigid PCBs?
Generally, flexible PCBs can be more expensive than rigid PCBs due to the specialized materials and more complex manufacturing processes involved. However, the overall cost can vary based on the design complexity and quantity.
