How to Choose the Right PCB material?

PCB board is an important core part of electronic products, and the material of PCB board determines the life and performance of PCB board. So in order to reduce the risk of project failure due to PCB board materials, we need to know how to choose the right PCB board material to ensure that our project design requirements are consistent with the required board functionality. Read the following PCB material guide to help you understand how to choose the right PCB board material to make the best choice for your design.

What are the main PCB board materials?

According to the hardness division, the general PCB board material can be divided into #rigidsubstrate material and #flexiblesubstrate material.

Rigid Substrate Material

The general rigid substrate material is copper-clad laminate (#CCL), which is made of reinforced material that adds strength and durability to the PCB and allows for good integration with PCB components. Rigid substrate materials include FR1, FR2, FR3, FR4, CEM1, CEM2, CEM3, Rogers, metal substrates, etc.

What is PCB FR1?

#FR1 is a paper substrate consisting of a thin copper layer on a non-conductive phenolic resin. It is an environmentally friendly substrate that complies with ROHS regulations and is easy to bend process and mold but is not suitable for over-hole, so it is usually used on single-sided PCBs.

What is PCB FR2?

#FR2 is a similar material to FR1, and their cost and use are similar. However, the Tg value of FR2 is lower than that of FR1 at 150°C, which means that the heat resistance of FR2 is not as good as that of FR1.

What?is PCB FR3?

#FR3 is also a paper substrate similar to FR2, but FR3 uses an epoxy resin that can be used as a coating on circuit boards.

What is PCB FR4?

#FR4 is a glass-reinforced epoxy resin laminate, FR (flame retardant) stands for flame retardant and meets the requirements of the UL94V-0 standard. Because FR4 has good adhesion to copper foil, good moisture resistance, and low cost, it is mostly used for double-sided or multi-layer PCBs, such as computer motherboards, power supplies, set-top boxes, Bluetooth audio, etc.

What is PCB CEM1?

#CEM1 is a low-cost flame retardant composite material made of compiled glass fabric surface and paper core combined with epoxy resin, which has better electrical and mechanical properties compared to paper materials such as FR1 and FR2, and is mostly used for single-sided PCBs.

What is PCB CEM2?

#CEM2 is similar to CEM1, the Tg value of CEM2 is higher than that of CEM1, but CEM2 is a non-flame retardant composite.

What is PCB CEM3?

#CEM3 is a copper-clad composite laminate, consisting of glass fiber cloth and copper foil impregnated with epoxy resin, a flame retardant material with a lower cost than FR4, mostly used in double-sided PCBs with plated holes.

What is PCB Rogers?

#Rogers material is a high-frequency material with advantages such as low electrical signal loss, low dielectric loss, and better thermal performance, which is widely used in the high-speed design, RF, microwave, and mobile applications.

What is PCB Metal Substrate?

#Aluminum and #copper are the most common metal substrates. Among them, aluminum substrates are mostly used for single and double-side pcb, which have excellent electrical performance, heat dissipation capability, high dielectric strength, and resistance to bending, and the cost is also much cheaper than other metal composites, and are widely used in LED lighting products.

Flexible Substrate Material

Common flexible substrate materials (FCCL) include mainly PET, PI?and PTFE.

What is PCB PET?

Polyester films, also called #PET, offer good flexibility, electrical properties, and high chemical and moisture resistance. Polyester films are typically 25 to 125 microns thick, have a melting point of 250°C and a glass transition temperature of 80°C, and can be bent to fit circuit boards in tight spaces.

What is PCB PI?

#Polyimide, often abbreviated as PI, is a polymer with excellent thermal stability, heat resistance, electrical properties and chemical resistance.

What is PCB PTFE?

#Polytetrafluoroethylene (PTFE), known by its brand name Teflon, is the preferred choice for flexible circuit boards with good temperature stability and low power consumption for applications such as cruise control, power amplifiers, and antennas.

4 Things to Consider When Choosing PCB Materials

1)?Thermal Properties

The thermal properties include the glass transition temperature, coefficient of thermal expansion, decomposition temperature and thermal conductivity.

The #glasstransitiontemperature is the board can not burn at a certain temperature and can only soften the temperature point, the unit is Tg (℃), the higher the Tg value, it represents the better the temperature resistance of the material to avoid melting or bending of the substrate in the production process.

The coefficient of #thermalexpansion (CTE) is a percentage that describes the expansion of a PCB when it is heated or cooled. In our experience, the PCB board material you choose in your design needs to have a low coefficient of thermal expansion to ensure it can handle the operating ambient temperature range. This is because if the coefficient of thermal expansion is high, each unit of temperature increases and the PCB will expand more, which affects the length, width, and thickness of the PCB, changing the shape of the PCB and may causing damage to the PCB.

#Thermalconductivity refers to the rate of heat transfer through the PCB material, in K (w/m), and is a parameter of thermal performance.

The #decompositiontemperature (Td), also called the lamination separation temperature, is the temperature at which 5% of the weight of the material is lost and is measured at °C.

2)?Electrical Properties

When you need to meet dielectric requirements such as balanced impedance, signal quality, and resistance, especially when building multilayer PCBs, electrical properties become one of the key factors to consider. Electrical properties include properties such as dielectric strength, dielectric constant, and volume resistivity. We can compare common PCB substrates by the dielectric constant (dk) and heat resistance (Tg) of these two characteristics, so as to choose the right PCB substrate for our design requirement

#Dielectricstrength refers to the Z-direction of the PCB circuit, the ability of the PCB board material to resist electrical breakdown in v/mil, the dielectric strength of most PCB board materials between 800v/mil and 1500v/mil.

The #dielectricconstant (DK) refers to the ability to store energy relative to a vacuum-enhanced material and is generally between 3.5 and 5.5. The dielectric constant tends to decrease with increasing frequency, and the lower the value of the dielectric constant (DK), the faster the transmission of high-speed signals.

#Volumeresistivity is the measure of dielectric volume resistance and is used to measure the insulation and resistance of PCB materials in Ω-m.

3）Mechanical properties

Mechanical properties include peel strength, flexural strength, density and delamination time

#Peelstrength refers to the ability to bond between the dielectric and copper layers of a PCB board under thermal and chemical stress.

#Bendingstrength refers to the ability of the PCB material to withstand physical stress without fracture, which determines the stress in the PCB material, measured by the tensile modulus.

#Thedenselayer refers to the number of masses per volume of the dielectric, measured in g/cm^3 or lb/in^3.

#Delaminationtime is the time that the PCB material is exposed to temperature changes or moisture, the PCB layer can be retained.

4）Chemical Properties

The chemical properties include three main components: plastic flammability, moisture absorption and resistance to methylene chloride.

#Plasticflammability refers to the flame retardant properties of plastics, UL94 for PCB requirements in the prescribed flame burning, the burning time of the specimen can not exceed 10 seconds. For a group of five specimens, combined specimens in the flame burning can not burn more than 50 seconds.

#Moistureabsorption refers to the ability of PCB board material submerged in liquid, most PCB board material moisture absorption value is between 0.01% and 0.20%. Moisture absorption will also affect the electrical properties of the dielectric and thermal properties.

Methylene chloride resistance (#MCR) refers to the chemical resistance of the PCB material and is the most direct measure of the resistance of the dielectric to methylene chloride absorption. Generally speaking, the dielectric MCR is between 0.01% and 0.20%.

Recommended PCB Material manufacturer

Isola, Rogers, Panasonic, Dupont, and Arlon are five well-known PCB board manufacturers in the industry, so you can choose the right brand of the board according to your budget and design requirements.

Conclusion

Each circuit board design is different, we recommend that you choose PCB materials before you can be based on the electrical properties mentioned in this article, thermal properties, mechanical properties, and chemical properties of the four key elements combined with your design requirements and cost requirements, a list of specific requirements. Then you can follow the list of requirements to choose the most correct material, for example, if good heat dissipation is required, then the metal substrate is a good choice. For example, if good heat dissipation is required then a metal substrate is a good choice. If high-temperature resistance is required then you can choose High Tg FR4.

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