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 Everything you should know about the Tg of PCB

Everything you should know about the Tg of PCB

Introduction

Tg of PCB In the prototyping and fabrication always encounter Tg130, TG150, and TG170. What does the PCB Tg value mean? And what do these models represent? What is the difference betweenTg130/TG150/TG170/TG175/TG180 PCB? Let us understand the role of Tg in the PCB industry through this article below.

What is Tg of PCB?

The PCB Tg is the glass transition temperature of the board under high-temperature heat. As we all know, the board must be flame-resistant. At a certain temperature, it can not burn, only soften. This time, the temperature point means the glass transition temperature (Tg point). This value related to the stability of the PCB board. The higher the Tg value, the better the temperature resistance of the board. especially the high Tg used in the lead-free tin spraying process.

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What Are the Tg of PCB Classifications?

The glass transition temperature (Tg) of PCB materials. That can vary widely depending on the type of material and its composition. Different types of PCB materials designed for specific applications . Here are some common classifications of PCB materials and their typical Tg ranges:

FR-4 Standard Tg PCBs:

FR-4 is the most commonly used PCB material. Standard FR-4 materials typically have a Tg range of around 130°C to 140°C . This is suitable for many general-purpose and consumer electronics applications.

FR4 PCB TG

High Tg PCBs:

High Tg PCBs designed for applications that require higher thermal stability. These materials have a Tg of 150°C or higher. The Tg for high Tg materials can range from 150°C to 180°C or even higher. High Tg PCBs are commonly used in lead-free soldering processes. automotive electronics, and industrial applications.

Rogers High-Frequency PCBs:

Rogers Corporation manufactures high-frequency PCB materials. that are specifically designed for applications in the microwave and RF ranges. These materials have Tg values that can range from 280°C to 400°C. depending on the specific Rogers material selected.

Specialty Materials:

There are specialty PCB materials with unique compositions. and Tg values designed for niche applications. For example, some materials engineered for high thermal conductivity. high-frequency performance, or extreme temperature resistance.

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The Benefits of High Tg PCB

High Tg (glass transition temperature) PCBs offer several benefits. that make them a preferred choice for various applications. especially those that involve elevated temperatures, lead-free soldering, and demanding environments. Here are the key benefits of using high Tg PCBs:

Thermal Stability:

High Tg PCBs designed to withstand elevated temperatures without undergoing significant dimensional changes. or loss of mechanical and electrical properties. This thermal stability is crucial for applications exposed to high operating temperatures. or soldering processes with lead-free solders.

Lead-Free Soldering Compatibility:

High Tg PCBs can handle the higher temperatures associated with lead-free soldering. making them essential for compliance with environmental regulations and RoHS directives. They prevent warping and maintain their structural integrity during soldering.

Reduced CTE:

High Tg materials have a lower coefficient of thermal expansion compared to standard materials. This property helps minimize the risk of thermal stress and microcracking. making the PCB more reliable in temperature-varying environments.

Dimensional Stability:

High Tg materials exhibit excellent dimensional stability. which is vital in applications with fine-pitch components. high component density, and stringent tolerances. The reduced risk of warping ensures consistent electrical and mechanical performance.

Improved Moisture Resistance:

High Tg materials often have lower moisture absorption rates. reducing the risk of delamination and electrical degradation due to moisture ingress. This is advantageous in applications where humidity or moisture exposure is a concern.

Enhanced Signal Integrity:

High Tg PCBs preferred for high-frequency and high-speed applications. They maintain their dielectric properties and signal integrity even at elevated temperatures. reducing signal loss and distortion.

Long-Term Reliability:

High Tg materials contribute to the long-term reliability of PCBs. They are less prone to degradation over time. making them suitable for applications with extended product lifecycles. such as in aerospace, automotive, and industrial sectors.

Environmental Resistance:

High Tg materials are more resilient in harsh environments. making them suitable for applications. where PCBs may encounter extreme conditions, vibrations, or chemical exposure.

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When To Choose To Use High Tg Material?

As a PCB manufacturer, we provide professional advice to our customers. on when to choose high Tg base materials is crucial for ensuring quality and reliability. Here are some key factors to consider when advising your customers on the use of high Tg materials:

Application Requirements:

Start by understanding your customer’s specific application requirements. Ask them about the operating temperature range, and environmental conditions. and any other critical factors that may affect the PCB’s performance.

Temperature Considerations:

If the application involves exposure to elevated temperatures. high Tg materials are typically recommended. Advise your customer to select materials with a Tg rating. that exceeds the expected operating temperature to ensure stability and reliability.

Lead-Free Soldering:

Inquire about the soldering processes your customer will be using. If they plan to use lead-free soldering. it’s essential to use high Tg materials to withstand the higher soldering temperatures.

Regulatory Standards:

Different industries may have specific regulations. and standards that dictate the use of high-Tg materials. Ensure that your customer is aware of any industry-specific requirements and compliances.

Signal Integrity:

High Tg materials are valuable for maintaining signal integrity. especially in high-frequency and high-speed applications. Discuss with your customer the importance of low dielectric loss. and consistent electrical properties in their design.

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Materials Used in High-Tg PCBs

High Tg (glass transition temperature) PCBs designed to withstand elevated temperatures. and provide better thermal stability compared to standard PCB materials. These materials are essential for applications that involve high-temperature environments. lead-free soldering processes, and demanding mechanical conditions. Several materials are commonly used in the manufacture of high Tg PCBs, and they include:

FR-4 High Tg Materials:

High Tg versions of FR-4 (Fire-Resistant Grade 4) are commonly used for PCBs. These materials made by enhancing the resin system. to increase the glass transition temperature. FR-4 High Tg materials typically have a Tg of 150°C or higher. making them suitable for lead-free soldering and applications requiring better thermal stability.

Polyimide (PI):

As we konw, polyimide is a high-temperature-resistant polymer used in flexible and rigid-flex PCBs. So polyimide PCB materials have a high Tg, typically ranging from 200°C to 260°C. They are well-suited for aerospace, military, and high-temperature applications.

PTFE (Teflon):

Polytetrafluoroethylene (PTFE), known by the brand name Teflon. That used in high-frequency and high-performance applications. PTFE materials have a high Tg, typically above 200°C . and provide excellent electrical properties. They are commonly used in microwave and RF PCBs.

Rogers High-Frequency Laminates:

Rogers Corporation manufactures high-frequency laminates specifically designed for microwave and RF applications. These materials have high Tg values. typically ranging from 280°C to 400°C, depending on the specific product.

High-Temperature Epoxy Resins:

Some high-Tg PCB materials use specialized epoxy resins engineered for high-temperature resistance. These resins can have Tg values that exceed 170°C . and are suitable for applications like automotive electronics and industrial equipment.

Enhanced Signal Integrity:

High Tg PCBs preferred for high-frequency and high-speed applications. They maintain their dielectric properties and signal integrity even at elevated temperatures. reducing signal loss and distortion.

Cyanate Ester Resins:

Cyanate ester resins known for their high-temperature performance. and can have Tg values exceeding 200°C . They used in applications where extreme thermal stability required.

BT Epoxy (Bismaleimide Triazine):

BT epoxy known for its high Tg, typically around 200°C . It used in applications that demand excellent thermal stability and reliability. such as aerospace and telecommunications.

Aramid (Aramid Fiber-Reinforced Substrates):

Some high-Tg PCBs use aramid fiber-reinforced substrates. which offer good mechanical and thermal properties. These materials used in applications that require high temperature and mechanical resistance.

When selecting a material for high Tg PCBs. it’s important to consider the specific requirements of the application. including operating temperature, mechanical stress, electrical properties, and regulatory compliance. Material data sheets and information provided by PCB material suppliers can help in choosing the right material. that meets the Tg and other performance criteria needed for the application.

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How to Test the PCB Tg Value?

The glass transition temperature (Tg) of a PCB (printed circuit board) can be determined using several methods, each with its own advantages and limitations. The choice of method depends on the equipment available, the precision required, and the specific needs of your PCB application. Here are some common methods for testing the Tg value of a PCB:

Differential Scanning Calorimetry (DSC):

DSC is one of the most widely used methods for determining the Tg of PCB materials. In DSC analysis, a small sample of the PCB material is heated at a controlled rate while measuring the heat flow. The Tg is identified as the temperature at which a change in heat flow occurs, corresponding to the transition from the glassy to the rubbery state. DSC is known for its accuracy and is widely accepted for Tg determination.

Thermomechanical Analysis (TMA):

Apparently , TMA measures the dimensional changes in a material as it is subjected to controlled temperature changes. And TMA can be used to determine the Tg by monitoring the expansion or contraction of a sample as it transitions through the glass transition region. TMA is particularly useful for studying the mechanical behavior of materials with changes in temperature.

Dynamic Mechanical Analysis (DMA):

DMA is a highly precise technique for characterizing a material’s mechanical and viscoelastic properties as a function of temperature. The Tg is determined by measuring the material’s modulus, tan delta, or other mechanical properties over a range of temperatures. DMA provides valuable insights into a material’s behavior near the Tg.

Fourier Transform Infrared Spectroscopy (FTIR):

FTIR can be used to identify the Tg of a material by measuring the changes in molecular vibrations as the temperature is increased. By monitoring the changes in infrared spectra, the Tg can be detected as a distinct shift in the material’s properties.

Thermogravimetric Analysis (TGA):

TGA measures the change in a material’s mass as it is heated. While TGA is primarily used for thermal decomposition and stability studies, it can also provide information about the Tg by observing weight loss or changes in the rate of weight loss as the temperature increases.

Dielectric Analysis:

Dielectric analysis involves measuring the electrical properties of a material as it undergoes temperature changes. The Tg can be identified by observing changes in the dielectric constant and loss tangent. This method is particularly relevant for applications involving high-frequency PCBs.

The choice of method should be based on the specific requirements of your application and the available equipment and expertise. It’s important to consider factors such as precision, temperature range, and the material’s behavior during the Tg transition when selecting a testing method. 

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What the Difference of TG130/TG150/TG170/TG180 ?

The differences between TG130, TG150, TG170, and TG180 PCB materials. That based on their respective glass transition temperature (Tg) values. and the specific applications for which they are best suited. Here are the main distinctions between these Tg classes:

Characteristic

TG130

TG150

TG170

TG180

Glass Transition Temperature (Tg)

≥ 130°C

≥ 150°C

≥ 170°C

≥ 180°C or higher

Thermal Stability

Lower thermal stability

Moderate thermal stability

Higher thermal stability

Highest thermal stability

Lead-Free Soldering Suitability

Typically not suitable

Suitable for lead-free soldering

Suitable for lead-free soldering

Suitable for lead-free soldering

Application Range

General-purpose

Moderate thermal requirements

More demanding thermal requirements

Extreme-temperature applications

Common Applications

Consumer electronics

Automotive electronics, some industrial and military applications

Automotive under-the-hood electronics, industrial control systems, more demanding aerospace and military applications

Advanced aerospace and military applications, high-temperature industrial and power electronics

Material Formulations

Varies by manufacturer

Varies by manufacturer

Varies by manufacturer

Varies by manufacturer

Cost

Lower cost

Moderate cost

Higher cost

Higher cost

Please note that the specific Tg values. and material formulations may vary slightly between manufacturers. When selecting a PCB material. it’s important to consider the specific requirements of the application. and the manufacturer’s data sheets. to ensure that the chosen material aligns with the project’s needs.

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Factors Influencing the Tg Value During PCB Production

The Tg of a PCB material influenced by various factors during the production process. Tg is a critical parameter that affects the thermal stability and reliability of the PCB. Here are some factors that can influence the Tg value during PCB production:

Choice of PCB Material:

The type of PCB material selected for the fabrication process plays a significant role in determining the Tg value. Different materials have different Tg ranges. and selecting a specific material with a higher Tg is one way. to ensure the PCB meets elevated temperature requirements.

Resin System Composition:

The composition of the resin system used in the PCB material affects the Tg value. The resin system is typically a combination of epoxy or other polymer resins. reinforcement materials (like glass fibers), and other additives. Adjusting the resin composition can impact the material’s thermal properties, including Tg.

Curing Process:

The curing process during PCB manufacturing involves subjecting the material. to elevated temperatures to harden the resin. The curing process of temperature, time, and pressure conditions can influence the Tg value. Proper curing is essential to achieving the desired material properties.

Glass Fiber Content and Orientation:

The content and orientation of glass fibers in the PCB substrate can affect the Tg. Higher glass fiber content and controlled fiber orientation. That can enhance the material’s thermal properties.

Additives and Fillers:

The addition of fillers, flame retardants, or other additives to the PCB material can influence the Tg value. These additives can affect the material’s thermal and mechanical properties.

Manufacturer's Formulation:

PCB material manufacturers develop specific formulations of their materials. and the exact composition can vary between suppliers. Different manufacturers may produce materials with slightly different Tg values. even if they claim to be the same type of material.

Quality of Raw Materials:

The quality and purity of the raw materials used in PCB production. including resins and reinforcement materials, can impact the final Tg value. High-quality materials are essential for consistent and reliable performance.

Copper Foil Thickness and Cladding:

The presence of copper foils on the PCB layers can also influence the Tg value. Copper has a higher thermal conductivity, and the thickness of copper layers. That can affect the heat distribution in the PCB.

PCB Design and Layer Stackup:

The design and layer stackup of the PCB can influence the thermal characteristics. For example, the arrangement of copper layers and the use of copper planes. That can impact the heat dissipation and thermal performance.

Post-Treatment Processes:

Post-treatment processes, such as surface finishes (e.g., ENIG, HASL, OSP), can affect the Tg value. Some surface finishes involve additional thermal exposure that may influence the material’s properties.

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Conclusion:

So, in general, the higher the Tg value, the better the temperature resistance of the sheet. The less severe the deformation of the sheet, the better the warpage. However, because of the high Tg value, it means the temperature requirement of the board. The pressed board will be harder and more brittle. which will affect the quality of the mechanical drilling. and the electrical properties of the board. If you want to know more about Tg of PCB please contact us now !

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