Are you looking to plunge into the world of Flex PCB Types? With their versatility and remarkable capabilities, Flex PCBs (Flexible Printed Circuit Boards) have revolutionized the field of electronics. They’ve made innovative designs possible for us all. Then, if you’re eager to explore the different types and possibilities of Flex PCBs, you’ve come to the right place.
This blog will cover various Flex PCB Types, including their applications and manufacturing processes. Whether you’re an electronics enthusiast, a hobbyist, or a PCB professional, this comprehensive guide will give you the info you need to decide.
And to top it off, we’ll showcase the number of layers and technology highlights to materials, profile methods, and surface finishes. We will cover all these and introduce you to a reputable manufacturer for all Flex PCB types.
So, fasten your seatbelt, and unravel the wonders of Flex circuit boards together!
What are Flex PCBs?
Flexible printed circuit boards, or flex PCBs, have a number of advantages over conventional rigid PCBs. They are a preferable option for many electronic applications because of these benefits. These PCBs started with Dr. P. Eisler. His work on flexible circuits was initially done in Austria and later continued in the United Kingdom.
Flex PCB Main Benefits
Compared to traditional Rigid PCBs, the benefits that flex PCBs bring to the table are:
Enhanced Flexibility
This flexibility allows for improved freedom in product design, making them suitable for applications with space constraints or intricate form factors.
Space Optimization
Flex PCBs’ thin and light design helps them to fit miniaturized products. This makes them perfect for portable and miniaturized devices. By eliminating bulky connectors and wires, flex PCBs enable sleeker, more compact designs.
Increased Reliability
Flex PCBs offer enhanced reliability due to their reduced number of interconnections and solder joints compared to traditional rigid PCBs. The flexible substrate minimizes the risk of mechanical stress and fatigue, improving the overall lifespan and performance of the electronic device.
Improved Signal Integrity
With shorter signal paths and better impedance control, flex PCBs improve signal integrity. This is critical for high-speed data transmission and sensitive electronic applications.
Higher Durability
Flex PCBs exhibit excellent resistance to vibration, shock, and temperature variations. This durability makes them well-suited for applications that undergo rigorous environmental conditions.
Design Versatility
If you need versatility in design and three-dimensional configurations, use Flex PBCs. They can be bent, folded, or twisted to fit specific spatial requirements.
While the initial manufacturing cost of flex PCBs may be slightly higher than rigid PCBs, the overall price is quite affordable if you factor in convenience.
Raw Materials for Flex PCB
Materials Used in Flex PCBs (Polyimide, Polyester, and Others)
All Flex PCB Types are manufactured using materials specifically chosen for their unique properties and suitability for flexible applications.
Common Materials Used in Almost All Flex PCB Types
- Polyimide (PI): Polyimide is a popular material choice
- Polyester (PET): Polyester is cost-effective and offers high chemical resistance
- Liquid Crystal Polymer (LCP): It is a high-performance material known for its exceptional mechanical strength, low moisture, and absorption
- Polyethylene Naphthalate (PEN): With good electrical and thermal properties, it features high tensile strength, chemical resistance, and dimensional stability
Adhesive Systems
These are used to bond different layers of the flex PCB together.
Applicable to all Flex PCB Types, they can be:
- Epoxy-based adhesives
- Thermal adhesives
- Acrylic-based adhesives
- Pressure-sensitive adhesives (PSAs)
Coverlay
Applied over the circuitry to provide insulation and protection for most Flex PCB Types
Soldermask
Used to protect the copper traces from oxidation and facilitate soldering during assembly
Surface Finishes
- Common surface finishes include gold plating, ENIG (Electroless Nickel Immersion Gold), and OSP (Organic Solderability Preservative).
- Never HASL
Now that we’ve covered the basics about Flex PCBs let’s go to the main part of this blog. We will be covering six main flex PCB types.
These are Single-Sided flex PCBs, Double-Sided flex PCBs, Multilayer Flex PCBs, Rigid-Flex PCBs, Semi-Flex PCBs and lastly, Hybrid Flex PCBs.
Single-Sided Flex PCB
#1 Single-Sided Flex PCBs
Here’s our concise guide for the Single-Sided Flex PCB:
Definition and Characteristics
- Single-Sided Flex PCBs are flexible circuit boards with conductive traces on only one side, while the other side may have a protective cover or insulation.
- They are lightweight, thin, and highly flexible, allowing them to conform to various shapes and spaces.
- The single-sided design simplifies the manufacturing process and reduces costs compared to more complex flex PCB types.
Typical Applications
- Widely used in cheaper, simpler consumer electronics such as:
- Handheld gaming devices
- Portable speakers
- TV remote Controls
- Calculators
- Printers
- Digital cameras
- Basic fitness trackers/smartwatches
- Flexible displays
- Touch sensors
- Membrane switches
Copper Weights and Minimum Track/Gap Specifications
- Single-Sided Flex PCBs typically use thin copper layers, with common copper weights ranging from 1/3 oz (0.375 oz) to 1 oz per square foot.
- The minimum track width and the gap can vary based on the specific manufacturing capabilities but are commonly around 0.004 inches (4 mils).
PCB Thickness and Maximum Dimensions
- Depending on the application requirements, it can range from 0.004 inches (4 mils) to 0.020 inches (20 mils) or more.
- The maximum dimensions can vary significantly; for example, small-sized ones can be 50mm x 50mm or 2 inches x 2 inches
- For larger single-sided flex PCBs, sizes can extend to 300mm x 300mm or 12 inches x 12 inches
Double-Sided Flex PCB
#2 Double-Sided Flex PCBs
Following the Single-sided Flex PCB is the Double-sided flex PCB. These offer a solution that combines the advantages of flexible circuits with limited capability to accommodate SMT components.
Definition and Features
- Double-sided flex PCBs consist of two flexible layers with circuitry on both sides and rigid sections for component mounting.
- They provide flexibility and bendability while supporting the integration of SMT components on the rigid sections.
Technology Highlights
- Can leverage advanced manufacturing techniques (to a degree) to achieve precise circuitry
- They cannot accommodate high-density interconnections (HDI) and complex circuit layouts.
Materials Used and Their Properties:
Polyimide, chiefly.
Component mounting may include standard rigid PCB materials, such as FR-4
Profile Methods and Manufacturing Techniques
- Laser cutting
- Punching
- Routing
Copper Weights and Minimum Track/Gap Specifications
- Copper Weights: Can support different copper weights ranging from 0.5 oz (17 µm) to 2 oz (70 µm) or more.
- Track/Gap Specifications: These range from 0.006″ (0.15 mm) to 0.010″ (0.25 mm), while gap distances may vary between 0.006″ (0.15 mm) and 0.010″ (0.25 mm).
SMT Compatibility
- Double-sided flex PCBs typically do not support SMT components directly on the flexible portion of the board.
- So, SMT components are mounted on the rigid areas, while the flexible sections provide interconnections and routing flexibility.
Double-sided flex PCBs enable the integration of flexible and surface mount technologies, offering a balance between flexibility and component density.
#3 Multilayer Flex PCBs
Multilayer flex PCBs offer advanced design capabilities and increased functionality by incorporating multiple layers of flexible circuitry. These flex PCBs consist of three or more layers of flexible circuitry interconnected using vias.
They provide increased design flexibility, allowing for complex circuit layouts and improved signal integrity.
Benefits
- Enhanced functionality and space optimization
- Ideal for compact electronic devices
- Enables the integration of multiple circuits, power planes, and signal layers,
- Supports the most advanced features and functionalities like RF and HDI
Number of Layers and Layer Stack-up Options
- Typically ranging from 4-6 layers depending on the design requirements.
- The layer stack-up configuration is customizable, allowing for specific arrangements of flex and rigid layers.
- Most of the layers come in even numbers (4, 6, 8, and so on)
But two companies, PCB Universe and Sierra Circuits, both from the USA, have pushed the boundaries of flex PCB technology. While PCB Universe, based in the USA, has achieved an impressive feat with a 16-layer flex PCB, Sierra Circuits has also demonstrated its expertise with multilayer flex PCBs, including up to 12 layers.
Whether it’s PCB Universe’s 16-layer flex PCB or Sierra Circuits’ 12-layer flex PCB, these examples showcase the potential for creating intricate and advanced flex PCBs to meet the demanding requirements of modern electronic applications.
Applications that Utilize these PCBs
Multilayer flex PCBs are utilized in a wide range of industries and applications:
- For instance, in telecommunications, they are used in network equipment and high-speed data transmission systems.
- In automotive systems, multilayer flex PCBs are vital in advanced driver-assistance systems (ADAS), vehicle entertainment systems, and engine control devices
- Benefit medical devices such as diagnostic equipment and implantable devices
- Also employed in industrial equipment, aerospace systems, and consumer electronics.
- Well-suited for devices requiring high-speed impedance control and signal integrity management.
Multilayer Flex PCBs enable the integration of multiple circuits in a compact form factor, making them an ideal choice for HDI and IoT usage.
Here is a short video to give you an idea how the Multilayer Flex PCB is made:
Minimum Mechanical Drill and Laser Drill Specifications
- Creating vias and through-hole connections between layers in multilayer flex PCBs requires precise mechanical and laser drills.
- Design specifications and manufacturing capabilities determine the minimum drill sizes and tolerances.
- Typically, mechanical drill sizes range from 0.1 mm to 0.3 mm, while laser drill diameters can be as small as 0.075 mm.
Structural Applications and Heavy Copper Flex PCBs
Multilayer flex PCBs find extensive use in structural and load-bearing scenarios where their flexibility and strength are essential. They can withstand various mechanical stresses and offer excellent reliability.
In addition, heavy copper multilayer flex PCBs are designed to handle higher current levels and increased power demands, making them suitable for demanding applications.
#4 Semi-Flex PCBs
The Semi-Flex PCB offers a unique combination of flexibility and stability. They’re also called flex-rigid PCBs (not to be mistaken with Rigid-Flex PCBs, which we discuss as #5 in our blog).
Semi-Flex PCBs are a hybrid construction typically consisting of 2-4 flexible layers and 2-4 rigid layers interconnected with plated through-holes.
Features and Advantages
Semi-Flex PCBs come with several notable features and advantages.
- They can achieve a bending radius as low as 4 times the thickness of the flexible layers, allowing for precise movements and space limitations in applications.
- These PCBs can handle 3-6 layers of copper, offering excellent electrical conductivity and signal integrity.
Additionally, Semi-Flex PCBs provide enhanced reliability, with the ability to withstand up to 200,000 flex cycles without failure.
Bending Capabilities
Flexibility and Bending Capabilities
Semi-Flex PCBs offer the flexibility to accommodate complex and intricate designs while maintaining stability. With a bending capability of up to 180 degrees, they can be shaped to fit within confined spaces, ensuring efficient use of available real estate in compact devices.
Applications and Industries
- They are used in flexible circuits for catheters, endoscopes, and wearable medical devices in the medical field.
- In aerospace, Semi-Flex PCBs are employed in avionics systems and satellite communications.
- They are also utilized in automotive electronics for flexible LED lighting, control panels, and sensors.
Design Considerations and Profile Methods
Designers must carefully plan the bending areas and ensure proper routing and clearance to avoid stress concentrations. Various profile methods, such as laser cutting and punching, achieve precise shapes and dimensions.
Copper Weights, Track/Gap Specifications, and Surface Finishes
- Semi-Flex PCBs offer flexibility in copper weights, track/gap specifications, and surface finishes.
- Copper weights typically range from 0.5 to 2 oz, allowing for varying current carrying capabilities.
- Track/gap specifications can be as low as 0.0035 inches, enabling high-density circuitry.
#5 Rigid-Flex PCBs
Rigid-flex PCBs combine the advantages of rigid and flexible PCBs. Using them, design possibilities for complex electronic systems abound.
Note that Rigid-Flex PCBs are not Semi-Flex PCBs.
While Rigid-flex PCBs are made up of interconnecting layers that are both rigid and flexible. Rigid and flexible portions are combined to create semi-flex PCBs.
Technology Highlights and Design Considerations
- Rigid-flex PCBs offer exceptional flexibility, allowing them to conform to three-dimensional shapes and fit into compact spaces.
- They enhance signal integrity by reducing the need for connectors and minimizing signal loss.
- Also, they improve reliability by eliminating the need for cable assemblies, reducing points of failure.
Materials Used in Manufacturing These PCBs
- Primarily utilize materials such as polyimide and polyester.
- Polyimide’s excellent thermal stability makes it the preferred material.
- Meanwhile, polyester is a more cost-effective option suitable for applications with lower thermal requirements.
Applications Rigid-Flex PCBs are Great For
- Aerospace and Defense: Avionics systems, military communications, missile guidance systems
- Automotive Industry
- Consumer Electronics
- Industrial control systems, robotics, factory automation equipment
- IoT and Smart Devices
- Medical Devices: Implantable devices, diagnostic equipment, patient monitoring systems
- Networking equipment, base stations, satellite communication systems
Profile Methods
Laser cutting, routing, and punching.
Copper Weights and Track/Gap Specifications
- Rigid-flex PCBs can accommodate various copper weights, typically ranging from 0.5 to 3 oz.
- The track and gap specifications depend on the design requirements and manufacturing capabilities, with typical values ranging from 3 mils to 8 mils.
Surface Finish & Solder Mask Options
- Rigid-flex PCBs support HASL for rigid parts only
- Like all flex PCBs, the Rigid-Flex PCB can use ENIG, OSP, Immersion Tin, Immersion Silver, and Hard Gold.
- Solder mask options include traditional orange and other colors like green, black, blue, and white.
Rigid-flex PCBs have the best combo of rigid and flexible layers. They have become a go-to choice for applications in aerospace, medical devices, consumer electronics, and more.
Hybrid-Flex PCB
#6 Hybrid Flex PCBs
These PCBs combine the flexibility of polyimide-based flexible circuits with the rigidity of FR4 or other rigid substrates. They are composed of both flexible and inflexible sections interconnected through Plated Through-Holes.
- Rigid substrates used in hybrid Flex PCBs: FR4 (Flame Retardant 4) and Polyethylene Terephthalate (PET)
- Aluminum has good thermal conductivity and a high strength-to-weight ratio, often used in aerospace and automotive applications.
- Ceramic
- Teflon (Polytetrafluoroethylene)
Applications and Benefits
Commonly used in consumer products, automotive, and medical devices. But they also benefit:
- Smartphones
- Tablets
- Laptops
- Gaming consoles
- E-readers
Copper Weights and Track/Gap Specifications
- There is a wide range of copper weights, typically ranging from 0.5 oz to 3 oz.
- The track and gap specifications depend on the design requirements and manufacturing capabilities, with typical values ranging from 3 mils to 8 mils.
Minimum Laser Drill Requirements for Hybrid Flex PCBs
- The laser drill sizes for hybrid Flex PCBs range from 0.1 mm (4 mil) to 0.15 mm (6 mil) in diameter. However, it’s important to note that specific designs may have different requirements.
- For example, a hybrid Flex PCB used in high-density applications with fine-pitch components might require laser drills as small as 0.075 mm (3 mil) to accommodate the tight spacing.
- On the other hand, larger drills up to 0.25 mm (10 mil) may be used for applications that prioritize robustness and current-carrying capacity.
Generally, Hybrid Flex PCBs can integrate flexible and rigid sections. They can be effective with space utilization, just like Rigid-Flex PCBs.
Ending
End Notes of Our Blog
So, there you have it— a comprehensive exploration of the various Flex PCB Types! We’ve delved into single-sided, double-sided, multilayer, semi-flex, rigid-flex, and hybrid-flex PCBs throughout this journey.
We’ve learned about their unique features, applications, materials, manufacturing techniques, copper weights, track/gap specifications, and surface finishes. Whether designing a wearable device, automotive system, medical instrument, or industrial equipment, understanding the Flex PCB Types empowers you to make informed decisions for your project’s success.
Now, as you go further into bringing innovative ideas to life, it’s crucial to partner with a trusted and experienced manufacturer capable of making these Flex PCB Types. That’s where MV Flex Circuit comes in.
With our expertise in Flex PCB Types manufacturing and dedication to quality, we’re here to support you every step of the way. We offer reliable and customized solutions that meet your requirements from prototype to production. Let us be your partner in turning your vision into reality.
Choosing Your Flex PCB Manufacturer Wisely
When selecting a flex PCB manufacturer for your project, make the right choice. Whatever Flex PCB Types you prefer.
You want a supplier who understands your needs, delivers high-quality products, and provides excellent customer service. At MV Flex Circuit, we pride ourselves on being a trusted and reliable flex PCB manufacturer.
We specialize in designing and manufacturing top-notch flex PCB types for various applications. You can have full confidence in us to satisfy your Flex PCB Types need. Here’s what sets us apart in terms of production:
- Extensive experience:
- Strict quality assurance
- Newest Technology based on Shenzhen’s world-class standards
- Timely delivery of your purchase globally.
By choosing MV Flex Circuit as your flex PCB manufacturer, you can have peace of mind knowing that you are partnering with a reputable Chinese company.
Contact us today!
