There are different types of substrate for fabricating printed circuit boards. The foundation of a PCB features a laminate and substrate. The type of substrate material used will determine the performance of the PCB. Therefore, it is important to choose the appropriate type of PCB material. This material will determine the failure or success of a PCB. Also, it impacts mechanical and electrical characteristics of the PCB.
What is a PCB Substrate Material?
The materials of a PCB feature components and transmission lines that allow RF/microwave circuits.PCB substrate material are the main material used for fabricating a circuit board. Also, this material ensures a minimum electricity amount from the circuit. FR4 is a good example of a PCB substrate material. Most of these materials are reinforced with epoxy resin. In addition, these substrate materials are widely used for the fabrication of printed circuit boards.
Types of Substrate material
There are different types of substrate materials. Each of these PCB substrate materials features several properties. Also, these materials are ideal for use in different applications. The application of these boards will determine the type of substrate to use.
FR4
FR4 is a popular PCB substrate material. It is a laminate reinforced with glass fabric and impregnated with flame-resistant epoxy resin. This versatile material is made from sheets of prepreg. Also, FR4 is the industry standard in terms of metallization and ease of drilling. The “FR4” specifies a class of materials that meet the NEMA LI 1-1998 standards.
This substrate material features electrical, thermal, and mechanical properties. The glass transition temperature of FR4 is 135 degree Celsius. Therefore, this material is ideal for use in high-density applications. Also, this substrate material features a high strength-to-weight ratio. However, this material has its limitations. It features a high dielectric loss which makes it not ideal for high-speed digital circuits.
PTFE
PTFE which is also known as Polytetrafluoroethylene is one of the most efficient PCB substrate materials. It is an ideal choice for high power and microwave PCBs. Also, PTFE features high thermal conductivity and dielectric strength. It maintains high flexural strength even in extremely low temperatures.
PTFE is a versatile plastic fluoropolymer suitable for various applications. It is commonly used in industries like aerospace and defense. The melting point of PTFE is about 327 degree Celsius. Also, this material is chemical inert and thermally stable. A PCB that features PTFE as its substrate material will be corrosion-resistant. This is because this material can repel oil and water. Also, this material is environmentally-friendly.
Polyimide
This substrate material features higher temperature performance. Polyimide materials are more expensive than FR4. This material provides enhanced survivability in harsh temperature environments. Also, they feature less expansion characteristics. Therefore, this makes them ideal for constructing higher layer PCB. Also, polyimide is resistant to chemicals. PCBs made with polyimide can function in a corrosive environment.
Polyimide material is widely used due to its strength and flexibility. Also, this PCB substrate features thermal stability and excellent flexibility. It is commonly used to fabricate rigid-flex and flexible PCBs. However this material is resistant to warping despite its flexibility. Also, it is an ideal choice for applications demanding physical durability. Polyimide can resist thermal damage during its manufacturing processes.
CEM
This is a cheaper alternative to FR-4 material. CEM means composite epoxy material. There are different types of CEM material. They are CEM 1, CEM2, and more. CEM 1 is ideal for fabricating single sided boards only. Also, CEM is made from woven glass epoxy, paper, and phenol compounds. CEM 3 is ideal for fabricating double sided boards. CEM 1 features a glass temperature of 122 degree Celsius. Also, CEM 2 features a glass temperature of 125 degree Celsius. CEM 3 features a glass temperature of 125 degree Celsius.
Alumina
This is a ceramic-based substrate material ideal for use in high frequency applications. It is the most effective ceramic based substrate material for PCB. This material features great thermal conductivity. Also, it is cost-effective. Hence, it is popularly used in fabrication PCBs. Alumina is capable of transmitting heat from critical components. Therefore, it is ideal for high-power boards.
How to Select the Best PCB Substrate Material
There are a wide variety of PCB substrate materials. These substrates vary in strength and thickness. Therefore, it is quite challenging to choose the best substrate for your PCB project. Ensure you consider the following properties when choosing a PCB substrate material:
- Mechanical properties
- Electrical properties
- Thermal properties
- Chemical properties
Mechanical properties
The mechanical properties include the peel strength and flexural strength. The peel strength indicates the strength of the bond between the copper conductor and the dielectric material. Also, the flexural strength measures the ability of the substrate material to withstand mechanical stress without breaking. The tensile modulus is another mechanical property to consider. This specifies the material’s strength on the PCB.
Electrical properties
When choosing a PCB substrate material, you should consider the dissipation factor and electrical strength. For instance, PTFE has a low dissipation factor which makes it deal in some applications. Another important property to consider is the dielectric constant of the substrate material. This helps to check signal integrity and impedance considerations. The frequency determines the dielectric constant values. Also, you should consider surface resistivity and volume resistivity.
Thermal properties
PCB manufacturers should consider thermal properties like CTE and thermal conductivity. CTE means coefficient of thermal expansion. It determines the rate at which a material expands after exposure to heat. Some materials will expand in response to heat. The glass transition temperature (Tg) is another thermal property to consider. Thermal conductivity measures the rate of heat transfer.
Chemical properties
The chemical properties of a substrate material include moisture absorption. This property measure the ability of a material to resist moisture. Moisture absorption can influence the properties of a substrate material.
Conclusion
PCB substrate materials influence the performance and functionality of a circuit board. Therefore, it is essential to know the types and what they offer. This article has provided information on the types of substrate materials available. Also, it provided vital information on how to choose these materials. Each of these substrate materials features different benefits.
