Printed Circuit Board (PCB) material selection and classification are two critical aspects of designing high-quality electronic circuits. In order to ensure optimal performance, it is crucial to carefully select the right PCB material for your specific application. This involves taking into account factors such as the operating environment, frequency range, and cost. In this article, we will discuss how to select PCB material and why it is important to consider the material's properties during the design process. Additionally, we will explore the different types of materials that are commonly used for PCB fabrication, and provide an overview of the classification of PCBs based on their construction and intended use.

What is the Classification of PCB Materials

The classification of rigid Printed Circuit Board (PCB) materials is typically predicated upon the resin type and the glass transition temperature (Tg) value of the board. This classification can help guide designers and procurement officers in selecting the optimal materials for specific applications, considering a variety of factors ranging from cost to manufacturability and regulatory compliance.

Resin type is a key determinant in the classification of PCB materials. There are six primary types of resins in the market, each has its unique properties and intended applications, FR-4 material is commonly used as a substrate material for rigid circuit board fabrication.

1. Phenolic Resin (FR2): 

This is considered a low-grade material generally utilized in general consumer electronic products. It's typically employed in single-sided boards (Fr2 PCB) due to its limited robustness and durability.

2. Epoxy Resin (FR4 series): 

Fr4 are often preferred for their excellent mechanical and electrical properties, as well as their commendable heat resistance, which make them a versatile choice for both general consumer electronics and industrial electronic products. In fact, this resin type is frequently used in the production of Fr4 PCBs due to its desirable characteristics.

3. Polyimide (PI) Resin, such as 85N: 

PI resin is recognized for its exceptional heat resistance, making it an excellent choice for electronic products that operate under high-temperature conditions.

4. Polytetrafluoroethylene (PTFE or Teflon), for example, RT5880: 

PTFE is employed for its high-frequency performance, making it appropriate for applications such as antennas and RF applications.

5. Bismaleimide Triazine (BT), such as Mitsubishi CCL-HL832HS: 

This resin type is noted for its improved heat resistance and dimensional stability, ideal for multilayer PCBs.

6. Cyanide Ester (CE): 

Although less common, CE is utilized for its high strength and stiffness, alongside its excellent heat and moisture resistance.

The Tg value of the board is another essential classification criterion. This value represents the temperature at which the PCB material transitions from a glassy, rigid state to a softened, pliable state. Four categories exist based on Tg value:

1. Normal Tg board: 130-140℃
2. Mid Tg board: 150-160℃
3. High Tg board: ≥170℃
4. Ultra-high Tg board: 250-260℃

How to Select PCB Materials

When it comes to the selection of materials for design or procurement, designers or procurement officers must consider several factors:

1. Material Availability: This involves consideration of the procurement cycle and timelines for product deployment.
2. PCB Manufacturability: Verifying whether the chosen board material aligns with existing manufacturing processes is critical.
3. Reliability for Lead-free Soldering: With the push towards environmentally friendly practices, the material must be suitable for lead-free soldering.
4. Cost Factors: These include customer research and development budget and cost control mechanisms.
5. Legal Regulations Compliance: Checking the board material's compliance with legal standards such as the Restriction of Hazardous Substances (RoHS) and Underwriters Laboratories (UL) standards is mandatory.

In consideration of the above factors, the following parameters are typically examined:

• Tg, Decomposition Temperature (Td), and heat resistance of small pitch.
• Dielectric constant (Dk) and Dielectric loss (Df).
• Halogen content (determines if it’s a halogen-free material or not).
• Other factors include Conductive Anodic Filament (CAF) resistance, Comparative Tracking Index (CTI) value, Coefficient of Thermal Expansion (CTE), and water absorption.

In conclusion, a comprehensive understanding of the classification of PCB board materials, along with knowledge of the factors that guide the selection of board materials during design or procurement, is integral to the successful implementation of PCB-based applications.

Now that we have an understanding of how to select the right PCB material for a particular electronic circuit, it's important to find a reliable PCB manufacturer that can provide high-quality materials and manufacturing services. This is where NextPCB comes in. NextPCB is a leading PCB manufacturing company that specializes in PCB prototype, PCB manufacturing, and PCB assembly services. With years of experience in the industry, NextPCB offers a wide range of PCB materials, including FR-4, polyimide, and PTFE, among others. Their extensive knowledge of PCB material properties, coupled with their state-of-the-art manufacturing capabilities, ensure that customers receive high-quality PCBs that meet their specific requirements. Whether you're a designer or a procurement officer, NextPCB's commitment to quality, reliability, and on-time delivery makes them an excellent choice for all your PCB needs.