The quality of PCB assembly is as good as the materials used in manufacturing them. Therefore, this implies that the performance and functionality of a PCB board depends on the type of material they are made from. With the increasing demand for miniturization of devices and cutting-edge technology, it is inctedibly important to choose the right type of PCB board material.
There are a huge range of PCB board materials that can meet your performance requirements. Quality PCB board materials don’t only offer great functionality, but also have great durability. In addition, proper material selection is good way to start your PCB manufacturing and PCB assembly. Also, there are parameters and factors that determine the type of material to use for your PCB project.
This comprehensive guide will help you discover the most common types of printed circuit board materials.
What are PCB boards made of?
Selecting a board material requires considering certain things. PCBs comprise some crucial layers. What are circuit boards really made of?
Substrate layer
The substate layer is the foundation of the printed circuit board. It is usually manufactured from fiberglass. Fiberglass is a very rigid materials, hence, it offers PCB rigidity. However, there are other materials used for substrate. This includes epoxies, CEM-1, G-11, insulated metal substrate, FR-1, and polyimide. Substrates are specially made to meet some requirements like dielectric constant and glass transition temperature. Fiberglass, which is popularly known as FR-4, is the most commonly used material for substrates.
Conductive layer
The copper layer is the conductive layer that makes signal traces. These signal traces conduct electricity in the circuit. Also, copper is a common material used for the conductive layer of a printed circuit board. Other materials like gold and silver can also be used. However, the conductive layers of PCBs are mostly made of copper. This is because copper is a good conductor of electricity.
Solder mask layer
Solder mask comprises a thin layer of polymer. It is on top of the copper clad laminate. Also, the solder mask gives the printed circuit board the green color. This layer prevents the formation of solder bridges by helping PCB manufacturers to solder the appropriate areas on the PCB board. Also, the solder mask prevents conductive copper traces from having contact with metal, solder, and other conductive materials.
Silkscreen layer
Silkscreen is an epoxy ink usually printed on the board. Also, it is a reference designator that indicates where to place components on the circuit board. Furthermore, it helps in detecting some warning symbols. A silkscreen helps to detect manufacturer marks and test points. Also, silkscreen is mostly white in color.
Types of PCB Substrate Materials
FR-4
FR4 is the most commonly used PCB substrate material. It is an epoxy resin laminate sheet reinforced with glass. Also, the epoxy of this material is flame retardant and water resistant. The “FR-4” simply means flame retardant level 4. Also, FR-4 has a high tensile strength and glass transition temperature. Therefore, this substrate can reach about 1180oC. Furthermore, this material is ideal for rigid PCBs.
FR-2
This substrate material has the lowest performance. FR-2 means flame retardant level 2. It comprises phenolic material. Also, FR-2 is commonly used in simple consumer electronics like small low cost radios.
FR-1
FR-1 is ideal for single-sided PCBs. It is a flame retardant level 1 material which is paper-based. It is similar to FR-2 as they both have identical properties. However, FR-1 features a higher temperature value.
Teflon (PTFE)
Teflon is an extremely flexible material that provides no resistance and as such, it is ideal for high speed signals. Also, Teflon is a type of plastic that features high mechanical strength, high degree of insulation, and flame resistance.
Flexible substrates
Flexible substrates can foldable and bendable materials that can form desired shapes. Also, these substrates enable designers to create circuit boards that can fit into the smallest enclosures. Rather than using epoxy resin or fiberglass, flexible substrates integrate plastic films.
These substrates are usually made with materials like liquid crystal polymer (LCP), polyimide, and polyester. In addition, polyimide is the most common material used for flexible substrates.
Metal substrates
Metal substrates are commonly made of aluminum. They offer great thermal and high dielectric properties. Also, aluminum can withstand temperatures of 350 degrees Celsius. These substrates provide exceptional high frequency performance. Therefore, it is ideal for applications like wireless communication base stations, RF sector, and LED lighting.
Other PCB Substrate Material Types
Asides from the materials mentioned above, there are other types of PCB substrate materials.
Fine ceramic
Examples of fine ceramic substances include aluminum nitride and aluminum oxide. Fine ceramic features great endurance when used in environments with high temperature. Also, ceramic compounds feature low CTE, high decomposition temperature, and high glass transition temperature.
CEM1
The composite epoxy material 1 (CEM1) has a whitish color and is usually integrated in printed circuit boards with a conductive layer. CEM1 is a material sandwiched between phenol substances and a glass fiber epoxy layer. Also, CEM1 features similar dielectric properties with FR-4. However, this material is cheaper than FR-4.
LTCC
Low temperature co-fired ceramics (LTCC) is commonly used for multilayer PCB manufacturing. Also, this circuit board material comprises burnt aluminum oxide. It is possible to burn LTCC substrates at temperatures of about 900oC by simply adding glass materials to aluminum oxide. Also, LTCC substrates are ideal for high frequency RF modules.