No matter the industry, PCBs are ubiquitous across almost all applications, including network and communication sectors. These boards play a crucial role in facilitating seamless communication. Printed circuit boards in these applications can utilize a variety of materials, with their structure and design tailored to specific application needs.
Material selection stands as the initial step in the PCB design process and holds significant importance. Choosing the right material greatly impacts the overall performance of the circuit board. Before making a selection, numerous factors must be carefully considered to ensure that the material properties align with the specific board requirements and final application.
One common challenge in PCB manufacturing is over-reliance on material data sheets by designers. While these sheets provide a comprehensive overview of the material’s electrical properties, real-world manufacturing issues often exceed the scope of these data sheets. Addressing such practical manufacturing challenges is crucial as they directly influence output quality and costs.
370HR: 370HR is essentially a prepreg and laminate used in PCB boards. PCBs made with 370HR meet ROHS requirements. A common issue in PCBs is Conductive Anodic Filament (CAF), an electrochemical corrosion process where copper at the anode dissolves and moves to the cathode, causing electrical short circuits that are especially detrimental in network and communications applications. However, 370HR PCBs are resistant to CAF. Additionally, they feature high-density interconnects and excellent thermal reliability. Polyclad designs its 370HR laminates and prepregs with a patented high-performance 180°C Tg FR-4 epoxy resin system, specifically tailored for multi-layer PCBs requiring maximum thermal performance and reliability. These materials are made from high-quality alkali-free glass fiber fabrics, ensuring superior CAF resistance. 370HR offers outstanding thermal properties, a low coefficient of thermal expansion (CTE), and mechanical, chemical, and moisture resistance properties that match or exceed those of traditional FR-4 materials. It has been widely adopted in thousands of PCB designs, recognized for its superior thermal reliability, CAF resistance, ease of processing, and performance in sequential laminate designs.
Glass Epoxy FR4: Glass epoxy FR4 boasts an excellent strength-to-weight ratio and is a versatile high-pressure thermosetting laminate, ideal for network and communication applications. It maintains electrical insulation and excellent mechanical properties under both dry and wet conditions, with near-zero water absorption and robust mechanical strength.
High-Speed Pyralux TK: High-speed Pyralux TK materials are primarily used in high-frequency PCB applications. These materials, often referred to as Teflon Kapton (TK), typically feature double-sided copper clad adhesive layers and laminates. Their bonding layers safeguard against harsh environments while providing strong electrical insulation. Primary composites include fluoropolymers and polyimides, offering advantages such as low moisture absorption, enhanced flexibility, and a low dielectric constant.
Polyimide: Polyimide is another material widely used in network and communication PCBs, valued for its exceptional thermal stability that enables it to withstand high temperatures in various applications. Known for providing a reliable surface mounting base, polyimide is also a cost-effective choice for PCBs.
Coefficient of Thermal Expansion (CTE): CTE refers to the rate of expansion of PCB materials when heated, expressed in parts per million per degree Celsius (ppm/°C). As temperature rises above the glass transition temperature (Tg), CTE also increases. The substrate’s CTE, typically higher than that of copper, can cause interconnection issues when the PCB is heated. CTE along the X and Y axes is generally low, about 10 to 20 ppm/°C, due to braided glass reinforcement limiting expansion in these directions. Z-axis CTE should ideally be less than 70 ppm/°C to minimize dimensional changes when the material exceeds Tg.
Dielectric Constant (Dk) or Relative Permeability (Er): Dk is the ratio of a material’s dielectric constant to that of free space (vacuum). It is also known as relative permeability and varies with resin content in the core or prepreg, which depends on composition, copper content, and prepreg thickness. Most PCB materials exhibit Dk values between 2.5 and 4.5, with higher Dk materials used in specific microwave applications. Dk generally decreases with increasing frequency.
In the realm of communication network equipment, the trend toward high-speed systems necessitates PCB materials with superior electrical properties. Concurrently, optimizing material costs remains crucial for enhancing the price competitiveness of electronic products. Thus, selecting materials that balance electrical performance and cost-effectiveness is a key consideration for PCB designers in the communication network sector.
Material selection stands as the initial step in the PCB design process and holds significant importance. Choosing the right material greatly impacts the overall performance of the circuit board. Before making a selection, numerous factors must be carefully considered to ensure that the material properties align with the specific board requirements and final application.
One common challenge in PCB manufacturing is over-reliance on material data sheets by designers. While these sheets provide a comprehensive overview of the material’s electrical properties, real-world manufacturing issues often exceed the scope of these data sheets. Addressing such practical manufacturing challenges is crucial as they directly influence output quality and costs.
370HR: 370HR is essentially a prepreg and laminate used in PCB boards. PCBs made with 370HR meet ROHS requirements. A common issue in PCBs is Conductive Anodic Filament (CAF), an electrochemical corrosion process where copper at the anode dissolves and moves to the cathode, causing electrical short circuits that are especially detrimental in network and communications applications. However, 370HR PCBs are resistant to CAF. Additionally, they feature high-density interconnects and excellent thermal reliability. Polyclad designs its 370HR laminates and prepregs with a patented high-performance 180°C Tg FR-4 epoxy resin system, specifically tailored for multi-layer PCBs requiring maximum thermal performance and reliability. These materials are made from high-quality alkali-free glass fiber fabrics, ensuring superior CAF resistance. 370HR offers outstanding thermal properties, a low coefficient of thermal expansion (CTE), and mechanical, chemical, and moisture resistance properties that match or exceed those of traditional FR-4 materials. It has been widely adopted in thousands of PCB designs, recognized for its superior thermal reliability, CAF resistance, ease of processing, and performance in sequential laminate designs.
Glass Epoxy FR4: Glass epoxy FR4 boasts an excellent strength-to-weight ratio and is a versatile high-pressure thermosetting laminate, ideal for network and communication applications. It maintains electrical insulation and excellent mechanical properties under both dry and wet conditions, with near-zero water absorption and robust mechanical strength.
High-Speed Pyralux TK: High-speed Pyralux TK materials are primarily used in high-frequency PCB applications. These materials, often referred to as Teflon Kapton (TK), typically feature double-sided copper clad adhesive layers and laminates. Their bonding layers safeguard against harsh environments while providing strong electrical insulation. Primary composites include fluoropolymers and polyimides, offering advantages such as low moisture absorption, enhanced flexibility, and a low dielectric constant.
Polyimide: Polyimide is another material widely used in network and communication PCBs, valued for its exceptional thermal stability that enables it to withstand high temperatures in various applications. Known for providing a reliable surface mounting base, polyimide is also a cost-effective choice for PCBs.
Coefficient of Thermal Expansion (CTE): CTE refers to the rate of expansion of PCB materials when heated, expressed in parts per million per degree Celsius (ppm/°C). As temperature rises above the glass transition temperature (Tg), CTE also increases. The substrate’s CTE, typically higher than that of copper, can cause interconnection issues when the PCB is heated. CTE along the X and Y axes is generally low, about 10 to 20 ppm/°C, due to braided glass reinforcement limiting expansion in these directions. Z-axis CTE should ideally be less than 70 ppm/°C to minimize dimensional changes when the material exceeds Tg.
Dielectric Constant (Dk) or Relative Permeability (Er): Dk is the ratio of a material’s dielectric constant to that of free space (vacuum). It is also known as relative permeability and varies with resin content in the core or prepreg, which depends on composition, copper content, and prepreg thickness. Most PCB materials exhibit Dk values between 2.5 and 4.5, with higher Dk materials used in specific microwave applications. Dk generally decreases with increasing frequency.
In the realm of communication network equipment, the trend toward high-speed systems necessitates PCB materials with superior electrical properties. Concurrently, optimizing material costs remains crucial for enhancing the price competitiveness of electronic products. Thus, selecting materials that balance electrical performance and cost-effectiveness is a key consideration for PCB designers in the communication network sector.
