In China, several types of copper-clad laminates (CCLs) are widely used in the production of Printed Circuit Boards (PCBs). These laminates vary in composition and properties depending on their intended application. The following sections will explore the types of CCLs, their characteristics, and classification methods.
**1. Classification Based on Reinforcing Materials**
Copper-clad laminates can be categorized based on the reinforcing materials used. The main categories include:
– **Paper-based CCL**: Typically made with paper as the reinforcing material, this type is used in lower-cost applications where performance demands are less stringent.
– **Glass Fiber Cloth-based CCL**: The most commonly used type in modern PCBs, especially for applications requiring high strength, thermal stability, and electrical performance. Glass fiber provides excellent reinforcement.
– **Composite-based CCL (CEM series)**: These laminates use a blend of materials like paper and glass fibers or other composites to provide a balance between performance and cost.
– **Multilayer PCBs**: These involve the use of multiple layers of laminate and copper to create more complex circuits, typically in applications such as high-density interconnects (HDI) or advanced devices.
– **Special Material-based CCL**: These include substrates made from materials like ceramics or metal cores. For example, aluminum substrates (metal core) are commonly used in LED PCBs due to their superior thermal management properties.
**2. Classification Based on Resin Adhesives**
CCLs can also be classified according to the types of resin adhesives used. The primary types include:
– **Paper-based CCL Resins**: These typically feature phenolic resins, including varieties such as XPc, XxxPC, and FR-1, FR-2. Phenolic resin-based CCLs are used in low-performance applications due to their low cost.
– **Epoxy Resin-based CCL**: Epoxy resins like FE-3 are commonly used in both paper-based and glass fiber-based CCLs. Epoxy is valued for its excellent electrical insulation properties, thermal resistance, and strong bonding with copper.
– **Polyester Resin-based CCL**: Polyester resins are often used in paper-based CCLs for applications that require moderate performance at a lower cost.
– **Glass Fiber Cloth-based CCL Resins**: The most prevalent resin used in glass fiber-based CCLs is epoxy (e.g., FR-4, FR-5). These resins offer a good balance of electrical properties, thermal stability, and ease of processing.
– **Special Resin Types**: For advanced applications, several specialized resins are used, often in combination with additional materials such as glass fiber cloth or polyamide fibers. These include:
– **Bismaleimide Triazine Resin (BT)**: Known for its high thermal stability and resistance to moisture absorption.
– **Polyimide Resin (PI)**: A high-performance resin with excellent thermal and chemical stability, often used in flexible PCBs.
– **Diphenylene Ether Resin (PPO)**: Known for its superior electrical properties, used in high-frequency applications.
– **Maleic Anhydride Iminostyrene Resin (MS)**: Offers good mechanical properties and is resistant to heat and chemicals.
– **Polycyanate Resin**: Provides high thermal stability and is used in advanced PCB applications.
– **Polyolefin Resin**: Used in specific applications requiring low cost and moderate performance.
**Conclusion**
Copper-clad laminates (CCLs) are integral to the production of PCBs, with various types and resins offering unique benefits depending on the application’s performance requirements. Whether using paper-based, glass fiber, composite, multilayer, or special material bases, the choice of laminate depends on factors such as strength, thermal management, cost, and electrical performance. Similarly, resin choices—from phenolic to specialized polymers—allow for customization of the PCB to meet specific operational demands. Understanding these classifications and materials ensures the selection of the most appropriate laminate for any given application.
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### Current Standards for Substrate Materials
The standards for PCB substrate materials can be classified into national and international categories. Below is a breakdown of these standards:
#### 1. **National Standards**
– **China**: The national standards for substrate materials in China include **GB/T4721-4722** (1992) and **GB4723-4725** (1992). These standards specify the technical requirements for materials used in PCB manufacturing.
– **Taiwan**: The copper-clad laminate standard in Taiwan follows the **CNS** (Chinese National Standard), which was established in 1983 and is largely based on the **Japanese JIS** standard.
#### 2. **International Standards**
Substrate materials are also governed by various international standards, including:
– **Japan**: JIS standards
– **USA**: ASTM, NEMA, MIL, IPC, ANSI, UL
– **UK**: BS (British Standards)
– **Germany**: DIN, VDE
– **France**: NFC, UTE
– **Canada**: CSA
– **Australia**: AS
– **Former Soviet Union**: FOCT
– **International**: IEC standards
Major suppliers of PCB materials include **Shengyi**, **Kingboard**, and **International**.
### PCB Substrate Material Categories
PCB substrates vary in quality and usage. From low to high quality, the common materials are listed below:
1. **94HB**: Ordinary cardboard, non-flame retardant, typically used for die punching. Not suitable for power supply boards (lowest-grade material).
2. **94V0**: Flame-retardant cardboard, suitable for die punching.
3. **22F**: Single-sided, half-glass fiber board, used for die punching.
4. **CEM-1**: Single-sided glass fiber board. Requires computer drilling, not suitable for die punching.
5. **CEM-3**: Double-sided, half-glass fiber board. This is the lowest-end material for double-sided boards, though it is cheaper than **FR-4** (typically 5-10 yuan per square meter).
6. **FR-4**: Double-sided fiberglass board, the most commonly used material for higher-quality PCBs.
### Key Material Parameters and Characteristics
– **Flame Retardancy Classification**: Materials are classified by their flame retardant properties, including:
– **94VO**, **V-1**, **V-2**, and **94HB** (from most flame-retardant to least).
– **Semi-Cured Film Thickness**:
– **1080**: 0.0712mm
– **2116**: 0.1143mm
– **7628**: 0.1778mm
– **Material Types**:
– **FR4**: A glass fiber board with high mechanical strength.
– **CEM-3**: A composite material typically used for double-sided boards.
– **Halogen-Free**: This refers to materials that do not contain halogens (e.g., fluorine, bromine, iodine), as bromine can release toxic gases when burned. Halogen-free materials are more environmentally friendly.
– **Tg (Glass Transition Temperature)**: This refers to the temperature at which the PCB material softens and transitions from a rigid to a flexible state. This temperature point is crucial for the dimensional stability of the PCB and its ability to withstand thermal cycling during use.
### Manufacturing Considerations
A PCB manufacturer must be capable of providing fast and precise sample production and demonstrate expertise in PCB fabrication. The choice of substrate material directly impacts the performance, durability, and cost-effectiveness of the final product, so understanding the material characteristics is essential for ensuring the right material selection for specific applications.
