Eager to know about high-speed PCB materials? This blog specifically focuses on high-speed printed circuit board (PCB) materials for the flexible type of circuit board.
Prepare yourself for a discussion on the game-changing innovations in flexible circuit boards used in the essential parts of daily life. Let’s learn the crucial role of high-speed PCB materials in lightning-fast data transmission.
Together, let’s dive into the intricacies of high-speed PCB material selection, uncovering the optimal choices that guarantee unparalleled signal integrity.
Advantages of Using Flexible Materials for High-Speed Signal Transmission
Signal integrity is paramount in high-speed electronic systems. Even minor signal degradation can have significant consequences. Flexible materials in constructing PCBs offer advantages that make signal integrity possible. Also, these materials make sure high-speed signal transmission happens.
The key advantages of using flexible materials in high-speed PCB designs are as follows:
Reduced Signal Loss
Flexible materials, such as PolyimidePolyimide and liquid crystal polymer (LCP), have lower dielectric constants (Dk) than traditional rigid PCB substrates like FR-4.
Consider the numbers:
Polyimide
Dielectric Constant (Dk): Typically ranges from 3.3 to 3.5.
Dissipation Factor (Df): Generally low, often around 0.003 to 0.007.
H4: Liquid Crystal Polymer (LCP)
Dielectric Constant (Dk): Typically ranges from 2.8 to 3.2.
Dissipation Factor (Df): Generally low, often around 0.001 to 0.01.
Compared to FR-4
Dielectric Constant (Dk): Typically ranges from 4.2 to 4.8.
Dissipation Factor (Df): Typically higher than flexible materials, often around 0.015 to 0.020.
Lower Dk reduces signal loss and better propagation at higher frequencies. It helps minimize the attenuation and distortion of signals, preserving their integrity over longer distances. Additionally, the lower dissipation factors of Polyimide and LCP materials indicate lower energy loss and better signal transmission efficiency.
Polyimide vs. FR4
More Flexible
The inherent flexibility of the materials used in flexible PCBs allows for improved signal routing and impedance control. With the ability to bend and flex, these PCBs can be designed to fit into tight spaces or conform to complex shapes. This flexibility reduces the need for bulky connectors, EMI, and excessive signal routing.
Mechanical Reliability
All flexible materials possess excellent mechanical properties, such as high tensile strength and resistance to vibration and shock. These characteristics make them well-suited for applications that experience physical stress, such as automotive, aerospace, and portable electronic devices. Consider the following values:
Polyimide’s Values
Tensile Strength: Approximately 110 MPa to 170 MPa (16,000 psi to 25,000 psi).
Resistance to Vibration and Shock: Polyimide is known for its excellent resistance to vibration and shock, making it suitable for applications in harsh environments.
Liquid Crystal Polymer (LCP) Values
Tensile Strength: Approximately 100 MPa to 190 MPa (14,500 psi to 27,500 psi).
Resistance to Vibration and Shock: LCP exhibits good resistance to vibration and shock, making it suitable for demanding applications in cars, aerospace, and electronics.
Polyethylene Naphthalate (PEN)
Tensile Strength: Approximately 150 MPa to 210 MPa (21,750 psi to 30,450 psi).
Resistance to Vibration and Shock: PEN offers excellent resistance to vibration and shock too.
Polyether Ether Ketone (PEEK)
Tensile Strength: Approximately 90 MPa to 170 MPa (13,050 psi to 24,650 psi).
Resistance to Vibration and Shock: PEEK is known for its high resistance to vibration and shock as well.
The ability of High-Speed Materials for flexible PCBs makes the flex PCBs withstand mechanical stress. Also, stable electrical connections become a reality. It minimizes the risk of signal degradation due to mechanical movement.
Lighter & Smaller
Most High-Speed PCB materials are lightweight and thin compared to rigid substrates. This advantage is crucial in applications where weight and space are critical, such as wearable devices, portable electronics, and aerospace systems.
Costs You Less
Flexible PCBs with High-Speed PCB materials offer cost advantages regarding material usage and assembly processes. The elimination of rigid substrates and the ability to create intricate designs using flexible materials can result in material cost savings.
The Materials Listed
What are the High-Speed PCB materials used in Flexible Circuits?
These boards with High-speed PCB materials are best-sellers because they support efficient signal transmission at high frequencies. Let’s explore some of these key materials and their characteristics:
Polyimide (PI)
The number one choice for High-Speed PCB materials is PolyimidePolyimide. It’s due to its excellent mechanical properties, high-temperature resistance, and good dielectric performance. It offers low signal loss and good insulation properties, making it suitable for high-speed applications. Polyimide films are commonly used as substrates in flexible PCBs, providing flexibility while maintaining stability and reliability.
Companies that manufacture them are the following:
DuPont
- DuPont makes Kapton®, a widely recognized polyimide film used as a substrate in flexible PCBs.
- DuPont offers various grades of Kapton® films with different thicknesses, thermal properties, and performance characteristics to meet diverse application needs.
Kaneka Corporation
- This corporation produces polyimide films for PCBs under their Apical® brand.
- Apical® polyimide films suitable for flexible PCB applications, including single-sided, double-sided, and adhesive-coated options.
Saint-Gobain
- The company is a supplier of polyimide films for PCBs under its Norton® TH portfolio.
UBE Industries
- Provides a range of UBISTOR® products suitable for flexible PCB applications, including options with surface treatments.
LCP
To continue with our list of High-Speed PCB materials, let’s discuss LCP.
- It is a specialized material known for its outstanding electrical properties, including low dielectric constant (Dk) and low dissipation factor (Df). Vectra® LCPs are known in high-performance applications, including electronics, automotive, outer space, and telecommunications.
- Other companies that make them include PolyOne’s OnForce™ LCP and Sumitomo Chemical’s SumikaExcel®. SumikaExcel®
- LCPs, are characterized by their high thermal stability, excellent flowability, low moisture absorption, and outstanding electrical properties. These LCP materials are utilized in connectors, switches, and microelectronic components.
Rogers Corporation’s High-Frequency Laminates
- Next, Rogers Corporation offers a range of high-frequency laminates specifically designed for high-speed applications.
- Materials like RO4000® and RT/duroid® exhibit low Dk and Df values, providing excellent signal integrity and minimizing losses.
- These laminates offer stable electrical performance over a wide frequency range, making them suitable for high-frequency and high-speed designs.
DuPont Pyralux®
Meanwhile, DuPont Pyralux® is a flexible circuit material combining polyimide film with copper foil layers. It offers excellent flexibility, heat resistance, and reliability. Pyralux® materials are widely used in consumer electronics, automotive, aerospace, and medical devices, where high-speed signal transmission is critical.
Isola’s ISpeed®
Offered by Isola is ISpeed®. It’s designed specifically for applications that demand high signal integrity. These materials feature low Dk, low Df, and tight impedance control, ensuring optimal signal performance in high-frequency designs. ISpeed® materials also incorporate thermal management properties, addressing heat dissipation challenges in high-speed applications.
High-Speed Adhesive Systems
Besides the substrate materials, the choice of adhesive systems used in flexible PCBs also impacts high-speed signal transmission. Adhesive systems with high-frequency characteristics, such as low dielectric loss and low moisture absorption, ensure minimal signal degradation and reliable performance.
Various companies specializing in electronic adhesives produce high-speed adhesive systems for flexible PCBs. Here are a few prominent suppliers in this field:
Henkel
Offers Loctite® and Ablestik®
3M
Their product line includes brands like Scotch-Weld™ and VHB™, which provide strong bonding and reliable performance.
Permabond
They provide a range of adhesive systems that offer excellent electrical properties, thermal resistance, and compatibility with flexible substrates.
Dow
Dow is a global manufacturer of adhesive solutions for various industries. They offer adhesive products, such as DOWSIL™ and Betalink™.
High-Speed PCB vs High-Frequency PCB
What is the difference between High-Speed PCB materials and High-Frequency PCB Materials?
Understanding the difference between high-speed and high-frequency in flex and rigid-flex PCBs is essential knowledge if you are designing PCBs.
While these terms are related, they refer to different aspects of signal transmission. Here’s an explanation to help clarify the concepts:
High-speed PCBs = fast signal transitions and data rates
The emphasis is on the rise and fall times of digital signals or the bandwidth of analog signals. Key factors in high-speed PCB design include reducing signal propagation delay, minimizing signal reflections, and managing signal integrity issues like crosstalk and electromagnetic interference (EMI).
High-speed PCB design techniques focus on controlling impedance, ensuring controlled routing, and optimizing the layout for signal integrity. These considerations are vital to maintain signal integrity and minimize data errors or signal degradation.
High-Frequency PCBs = signals with high-frequency components (RF & Microwave)
With high-frequency PCB materials, they are dedicated to RF (radio frequency) and microwave ranges. The focus here is on the actual frequency of the signals being transmitted. High-frequency PCB design involves controlling the characteristic impedance of transmission lines to match the source and load impedance, preventing signal reflections and loss. It also minimizes losses due to dielectric absorption, skin effect, and other high-frequency phenomena.
The design considerations for high-frequency PCBs often involve:
- Specific transmission line structures.
- Impedance matching.
- Controlled dielectric materials.
- RF component placement techniques.
Why the confusion between High-Speed PCB materials and High-Frequency PCB materials?
It’s important to note that high-speed and high-frequency designs often intersect, as high-frequency signals tend to require high-speed transmission. As a result, a successful PCB design for high-frequency applications usually incorporates high-speed design techniques to maintain signal integrity at higher frequencies.
Where are High-Speed PCB materials used in daily life?
Our daily lives use High-Speed PCB materials, especially in terms of technology that we use at home. Here are a few examples:
Internet and Data Communication
- High-speed PCB materials are extensively used in routers, modems, and networking equipment, enabling internet connectivity and data communication.
- These materials help maintain fast and reliable data transmission, allowing us to browse the web, stream videos, and connect with others online.
Consumer Electronics:
- Many consumer electronic devices we use daily, such as smartphones, tablets, and laptops, incorporate high-speed PCB materials.
Home Entertainment Systems
- Found in home entertainment systems, including televisions, gaming consoles, and audio systems
- These materials help deliver high-quality audio and video signals for a better viewing or gaming experience.
Smart Devices & Wearables
- Consider the ecosystem of IoT devices, such as smart speakers, smart thermostats, and smart home security systems; they rely on high-speed PCB materials.
- Wearable tech that needs data transfer and real-time communication between IoT devices, such as fitness trackers, smartwatches, and health monitoring for out-of-patient care.
- Uses sensor data, biometric information, and wireless connectivity, allowing us to track our health and stay connected on the go.
So, as you see, High-Speed PCB materials are valuable. But using them needs specialized knowledge. Read about this in the next section.
Manufacturing Considerations
Special Considerations for Manufacturing High-Speed PCBs with Flexible Materials
Not the ordinary type of PCB materials, High-Speed PCB materials need special care:
During material handling
Choosing the right high-speed PCB material is crucial for achieving top-notch performance. Flexible materials like Polyimide or LCP have unique properties that require special attention during manufacturing.
Controlled temperature and pressure when the flexible material is bonded to other layers
- Temperature typically ranges from around 150°C to 200°C (302°F to 392°F).
- Pressure applied during lamination generally ranges from 5 to 15 bar (72 to 217 psi).
Note: this applies to LCP (Liquid Crystal Polymer) and PI (Polyimide) flexible materials during lamination.
Etching of the flexible material requires accurate trace widths, spacing, and impedance values
Specifically, you need to implement the following, if you are designing High-speed applications:
Trace Widths
For flexible PCBs, trace widths can range from as small as 0.075 mm (3 mils) to larger widths of around 0.5 mm (20 mils) or more, depending on the application and current carrying capacity required.
Here’s a simple video on etching for PCBs:
Spacing
The spacing between traces, also known as the gap or pitch, is typically determined by design considerations such as signal integrity requirements, manufacturing capabilities, and the complexity of the circuit. It can vary from as small as 0.075 mm (3 mils) to several millimeters.
Minimum Feature Sizes
In precision etching, the minimum feature size refers to the smallest dimension that can be accurately etched. This includes the smallest trace width or spacing achievable. As manufacturing techniques continue to advance, it is possible to achieve feature sizes as small as 0.025 mm (1 mil) or even smaller.
Controlled flexing and bending are needed so that circuit can last long
This can be achieved by implementing the following:
- Dynamic Flex Testing
- Controlled Bending Radius
- Proper design of the flex areas
- Selection of flexible materials considering their tensile strength, elongation, and flexural modulus
- Use of adhesives with good flexibility and adhesion properties
Surface Finish Considerations
Only surface finishes compatible with flexible materials, such as ENIG, ENEPIG, OSP, and Immersion Silver, are used. You can’t use HASL in high-speed PCBs.
Handling and Storage
Lastly, High-Speed PCB materials are more susceptible to damage than rigid materials. It’s especially true for High-Speed PCB flex materials. Proper handling, storage, and protection during manufacturing processes, transportation, and assembly are necessary to prevent scratches, tears, or stretching.
Your Flex PCB Manufacturer
Your lifetime partner for flexible circuit boards with High-Speed PCB materials
In the ever-evolving world of electronics, utilizing High-Speed PCB materials in flexible circuit boards has become essential for unlocking new possibilities and achieving optimal performance.
Now that you’ve understood all there is to know about the complexities of utilizing High-Speed PCB materials, it’s time to introduce you to your ideal partner in this journey—MV Flex Circuit. We specialize in providing high-quality flexible circuit boards that leverage the advantages of High-Speed PCB materials, such as Polyimide, PEEK, PEN and LCP.
We are committed to excellence and possess knowledge. We are confident that these cutting-edge materials’ flexibility, signal integrity, and dependability will be advantageous to your electrical designs.
Introducing MV Flex Circuit
At MV Flex Circuit, we take pride in being at the forefront of the flexible PCB industry. With years of experience and a dedicated team, we offer flexible and rigid-flex circuit boards perfectly made for you. Whether you require flexible circuit boards for high-speed applications, medical devices, aerospace systems, or IoT devices, we have the expertise to deliver. Our state-of-the-art manufacturing facilities, stringent quality control processes, and collaborative approach ensure you receive the highest quality products that meet your special requests.
Contact us immediately to develop flexible circuit boards that can enhance your ideas.
