FR4 PCB Material

FR4 is a very commonly used dielectric material for PCB manufacturing. FS Technology is the best FR-4 PCB manufacturer in China, if your project needs to use it, please contact us to get your quotation.

Directory of FR-4 PCBs

What is FR4 PCB

There are different types of PCB is used in industrial and electronic engineering. Each type of circuit board has its corresponding characteristics and application areas. FR4 is a new type of circuit board material, and printed circuit board created with this substrate material are called FR-4 PCBs. In conventional PCBs, there are glass reinforced epoxy resins used as substrate materials. FR4 is fiberglass covered with epoxy laminated layers. Fiberglass is used to offer the stale structure of the material. The materials used for FR4 boards is according to UL94V-0 standards.

Typically a qualified turnkey PCB assembly company can create boards using different types of substrate materials. Taking FS Technology as an example, in addition to making FR4 PCB board, we can also produce aluminum PCB, rogers PCB, etc. The circuit boards we manufacture can achieve single-layer, double-layer, and multi-layer structures. 

High TG FR4

It is a cured category of FR4 PCB and this board is used for projects and applications that require high temperatures. FR4 refers to epoxy glass material grade. Tg is an abbreviation for glass transition temperature. This type of FR-4 PCB is considered the finest option for lead-free soldering and insuring the board from variable temperature conditions. Its common applications are communication system devices and in automobile vehicles. 

Halogen-free FR4

The term halogen-free means that the substrate does not use the periodic table elements bromine, iodine and chlorine. Although halogen-containing flame retardant materials will produce a large amount of toxic gas that is harmful to the human body after combustion, many manufacturers still use them in electronic equipment because of their good flame retardancy. In order to prevent halogen elements from causing damage to the human and nature, FS Tech uses phosphorus and phosphorus nitrogen instead of halogen elements. These materials also have good features for lead-free soldering. Glass transition temperatures fo this substrate is about 150C and decomposition temperature is 330C. The halogen-free substrate is used for devices that created hazardous smoke when gets burnt such as technical instruments. It is commonly used in mobile communication systems and related projects.  

Features of FR4 PCB

FR4 PCB material properties

The temperature of FR4 PCB

As we all know, the TG value is an indicator to measure the heat resistance of the PCB board. Higher TG values represent higher temperature ratings and vice versa. FR4 printed circuit board is created through the use of numerous layers of glass fiber reinforced with epoxy laminated. The maximum operating temperature of PCB FR4 is 130 degrees, which redefines the temperature rating of PCB. If you think that as long as the temperature is below 130C its characteristics will not change then you are wrong. In fact, even if your temperature is not up to the rated value, the physical characteristics of the board will still change. This is because there are too many types of electronic components on the PCBA board, and you can’t take into account the rated temperature of all components, so FS Technology recommends that it should not exceed 100C, even if you use FR-4 material with a high temperature rating. Because the electrical and mechanical properties of circuit boards will be affected by high temperature and TG, FR-4 PCBA boards are widely used in industry. Therefore, FS Technologies recommends that you always consider temperature values when applying FR4 in any circuit.

FR4 PCB thickness

The thickness for Fr-4 PCb is about 0.2-3.2 mm.

Thermal conductivity of FR4 PCB

FR4 materials are considered poor thermal conductors. The thermal conductivity of FR4 is 0.3W/(m·K), the thermal conductivity of copper is 385W/(m·K), and the general range is 10~45W/(m·K). The thermal coefficient of metal materials is the highest.

Some factors affect the thermal conductivity of FR4 PCB

  • Vias
  • Copper Traces in PCB
  • Inner Layers

Vias are holes created on the surface of PCB that help to dissipate heat.  The principle is to spread the heat through the components to the surface of the entire PCB by punching holes on the bare board, and then transfer the heat to the external environment through convection and radiation transfer. FS Tech believes that this is a way to treat the symptoms but not the root cause. If only vias are used as a heat dissipation measure, a small number of vias cannot really solve the problem, but when the number of vias reaches a certain value, the benefit will be greatly reduced. Because the heat does not disappear out of thin air, but collects in the position of the via, which will cause uneven heating of the entire circuit board.

The traces also helps for good thermal conductivity. If traces come in complete connection then heat can dissipate easily. For high heat, dissipation traces must be completed.

The inner layers also help for heat dissipation of the board. If layers are larger thermal conductivity will be reduced.

FR4 PCB density

The density value of FR4 printed circuit board is 1.850 g/cm3

FR4 material has low hygroscopicity

FR4 material comes with features to absorb less quantity of water. its water absorption rate is about 0.10 percent that is very less SO used for marine applications.

FR4 material can resist radiation

FR4 boards are mostly used in communications systems. It comes with features of heat radiation resistance. So used for applications where high radiation is eliminated

FR4 PCB mechanical properties

  • These boards high value for impact strength
  • Dissipation factors of FR4 is less that making it, effective on boards
  • These boards have a stable structure that can bear vibration and shocks
  • It comes with features of less cold flow rates
  • These boards have a high value of tensile strength
  • It has the ability to resist radiation that can damage the boards
  • Its dielectric strength is larger than used for good conductivity
  • High Glass Transition Temperature is about  (150Tg or 170Tg)

Comparison of fr4​ PCB with other types

Advantages of FR-4

FR materials include FR1, FR2, FR3, and FR4 PCB sheet. This article only makes a simple comparison.

  • Use glass fiber reinforced epoxy resin material different from other circuit boards. It is less expensive than FR3 epoxy adhesives and FR2 phenolic resins
  • FR 4 can manufacture single-layer boards, double-layer boards and multi-layer boards. FR1, FR2 and FR3 are not available for the manufacture of multilayer boards
  • High temperature resistance, can work in circuits above 130 degrees Celsius
  • FR1, FR2 and FR3 are not available for the manufacture of multilayer boards

Rogers VS fr4

  • Rogers is better than FR4 in terms of temperature management capabilities
  • In terms of signal, FR4 is more prone to signal loss than Roger
  • FR materials have larger dissipation factor values.
  • In the case of impedance management, the dielectric constant of the roger is different
  • Fr4 is cheaper than Roger
  • FR4 has a smaller dielectric constant value than Rogers PCB

Aluminum PCB VS FR4

  • Aluminum PCB has better heat dissipation coefficient than FR4
  • Aluminum PCBs are chosen when creating larger size boards due to their good mechanical strength and the ability to handle more PCB components
  • Aluminum has properties that protect circuit components from electromagnetic radiation
  • Aluminum is used for LEDs and FR4 is used for HDIs

Ceramic PCB VS FR4

  • The thermal conductivity of FR-4 is less than that of ceramic. Aluminum oxide, aluminum nitride, or silicon carbide ceramic PCBs all have higher thermal conductivity than FR-4
  • FR4 PCBs do not heat dissipate easily so these need vias, metallic layers, and cooling elements to move heat while these are not used for ceramic

How to design FR4 PCB

The steps involved for FR4 PCB plate creation are explained below

  • Materials Cutting
  • Dry film coating
  • AOI inspection done
  • Insulation
  • XRAY inspection
  • Hole Making on the board
  • Electroplating
  • Etching
  • Silkscreen applications
  • Board manufacturing
  • Surface finishes
  • Milling process
  • Electric testing for finding the fault
  • Quality control test
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