High-Density Interconnect (HDI) printed circuit boards (PCBs) are widely used in various fields, especially in smartphones, tablets, medical devices, and automotive electronics, due to their high integration and miniaturization characteristics. The choice of materials for HDI PCBs is crucial, as their properties directly influence the performance and reliability of the circuits. This article explores common materials used for HDI PCBs and their respective properties.
1. FR-4 Material
Model: FR-4
Properties:
Dielectric Constant: Typically between 4.0 and 5.0.
Dissipation Factor: Ranges from 0.02 to 0.03.
Heat Resistance: Meets UL 94 V-0 flammability standards, with a high thermal deformation temperature.
Mechanical Strength: Good compressive and bending strength, suitable for high-density routing.
Applications: Widely used in consumer electronics, computers, and communication devices.
FR-4 is one of the most commonly used substrates for HDI PCBs due to its balanced performance and relatively low cost. Its electrical characteristics are suitable for most medium to high-frequency applications.
2. RO4350B
Model: RO4350B
Properties:
Dielectric Constant: 2.55±0.05.
Dissipation Factor: 0.0037, making it ideal for high-frequency applications.
Coefficient of Thermal Expansion: CTE is 30 ppm/°C, indicating good thermal stability.
Temperature Resistance: High-temperature resistance suitable for high-power and high-frequency designs.
Applications: Mainly used in RF circuits, microwave circuits, and high-frequency signal transmission.
RO4350B is particularly suitable for HDI PCBs that require stringent signal integrity control due to its low loss and high-frequency performance.
3. RO4003C
Model: RO4003C
Properties:
Dielectric Constant: 3.38±0.05.
Dissipation Factor: 0.0035, suitable for high-frequency applications.
Coefficient of Thermal Expansion: CTE is 18 ppm/°C.
Processing Performance: Easy to drill and process, suitable for complex circuit designs.
Applications: Widely used in communications, medical devices, and industrial control high-frequency electronics.
RO4003C’s good electrical and processing properties make it another popular choice for HDI PCB designs.
4. Teflon® (PTFE)
Model: Teflon® (PTFE)
Properties:
Dielectric Constant: Approximately 2.1, very suitable for high-frequency applications.
Dissipation Factor: Below 0.0002, resulting in minimal signal loss.
Temperature Resistance: High temperature tolerance, suitable for harsh environmental conditions.
Mechanical Properties: Strong chemical resistance, suitable for specialized environments.
Applications: Mainly used in aerospace, military, and high-frequency communication devices.
Teflon® performs exceptionally well in high-frequency and high-temperature environments but is relatively expensive, mainly used in high-end applications.
5. High Tg Materials
Model: High Tg FR-4
Properties:
Glass Transition Temperature: Generally above 170°C.
Dielectric Constant: Between 4.0 and 5.0.
Mechanical Strength: Good thermal shock resistance and bending strength.
Applications: Suitable for electronic products operating in high-temperature environments, such as automotive electronics and industrial control.
High Tg materials maintain stable electrical performance under high temperatures and pressures, making them suitable for HDI PCBs that require high thermal stability.
6. Polyimide (PI)
Model: Polyimide Film
Properties:
Dielectric Constant: Approximately 3.0.
Temperature Resistance: Excellent high-temperature resistance, suitable for high-power applications.
Mechanical Properties: Exceptional flexibility and abrasion resistance.
Applications: Mainly used in flexible circuits and HDI PCBs requiring high-temperature performance.
Polyimide materials are known for their superior thermal resistance and mechanical strength, commonly used in demanding flexible HDI PCB applications.
7. Aluminum Substrate
Model: Aluminum PCB
Properties:
Thermal Performance: Excellent heat dissipation capabilities.
Mechanical Strength: High strength and impact resistance.
Applications: Widely used in LED lighting and automotive electronics where good heat dissipation is essential.
Aluminum substrates offer significant advantages in thermal management, making them suitable for power-dense HDI PCB designs.
The performance of HDI PCBs depends not only on design but also on the choice of materials. Depending on specific application requirements, different types of substrates can be selected. From FR-4 to advanced PTFE and polyimide materials, each type offers unique properties and application scenarios. Understanding these materials helps engineers make informed decisions during design, thereby enhancing product performance and reliability.