PCB FR-4: the Guide to fr-4 for your Printed Circuits

Epoxy resin is used for the impregnation of fiberglass sheets. These sheets are used to make FR4. Eight reinforced sheets were used, covered with a copper foil layer. This structure is configured in press, and that makes a single FR-4 sheet as a combination.

Materials for FR-4 Fabrication

The glass that exists in the FR4 sheet makes it a strong material. The epoxy resin used is normally used as a flame retardant. Bromine used to provide the flame retardant features. It makes PCb a flame-resistant material. It also helps to avoid high temperatures.

Copper used helps to etch patterns on board. These etching patterns make basic circuits that make connections between components. It also makes connections of interconnects of circuits.

Interconnections make connections of layers on boards. In FR4, hardened epoxy is used as  dicyandiamide. It comes with a high temperature of 300 degrees.

FR4 is part of multiyear boards with single layers for component connections.

Types of FR-4

Standard FR-4

This type of FR4 is called normal material that has heat resistance from 150-160 Celsius.

High TG FR-4

High TF FR4 means high glass transition temperature. PCB board created with high glass transition temperature FR4 materials come with features to resist and sustain structure for 170 degrees. This material’s high TG value is obtained through a good lamination process.

PCB created with these materials has features of high resistance and maintains structure at 170 degrees.

The standard FR4 is the best insulator and flame retardant but comes with limitations for high-power voltage or heat.

High TG FR-4 Material Uses

• It is part of electrical and electronic devices and projects.
• It is used in computer motherboard creation.
• It is also part of communication devices.

High CTI FR-4

The CTI, or Comparative Tracking Index, is the limit for which FR4 can handle undesired current passing over the board traces. The value of CTI helps to define how much resistance board materials show for different electrical conditions like moisture and leakage on board.

The high value of CTI material is about 600, which helps the material resist and handle the harsh conditions.

High CTI FR4 material is used in marine applications and aircraft.

FR-4 with no laminated copper

This FR4 is different in its functions. According to its name, this material did not have copper lamination and was sometimes used as insulation and board support.

Applications of FR-4

Read Also: Lead vs. Lead-Free Solder in PCB Manufacturing – 2023 Ultimate Guide

• There are different applications of FR4 explained here.
• It is part of consumer electronics.
• It is part of the aerospace and defense systems.
• Automotive electronics
• It is used in industrial control systems.
• It is used in different telecommunications equipment.

Advantages and Disadvantages of FR-4 Materials PCB?

Advantages

1. FR4 PCB board is commonly used and has a low cost. They offer good quality operation. However, the cost of a high glass transition temperature and a high comparative tracking index is high.
2. This material comes with a high dielectric strength of about 4.25-4.55, according to different parameters like glass weave style, resin content, thickness, and copper foil roughness. The dielectric strength explains the highest electrical field that dielectric materials show resistance to without breaking or changing into conductive materials.
3. FR4 is a mixture of fiberglass and epoxy resin and offers high load-bearing features and mechanical strength to the board. The thickness of standard FR4 is about 0.2 to 3.2 mm.
4. FR4 offers good moisture resistance features. Humidity does not have an effect on the FR4 board like contracting and expansion. But moisture absorption affects the electrical and thermal features of the material and also the power of materials to handle conductive anode filament creation during power connection. So a high value of moisture resistance has advantages for FR4 uses as base PCB materials and supported boards in marine uses.
5. FR4 is a high-temperature-resistant material and has a value of Tg of about t 150 Tg. The Tg is the glass transition temperature of PCB. Glass transition is the temperature where the board starts to become softened and affects its structure. So high TG boards are important.
6. They have a high decomposition value, which means the temperature where the board is about five percent of the laminate mass is lost due to decomposition. FR4 board material has a good decomposition temperature of >345 Celsius. The high decomposition temperature provides good protection to the board for long-life working.

Disadvantages

• The main drawback of FR4 is its high cost. The materials used for FR4 are high cost, which makes the overall product high cost.
• Working with these materials is difficult. It is a hard material, and that causes problems during cutting. So not easily configured on devices and projects.
• These materials are limited in flexibility. It is rigid materials that make it difficult to bend. It can be difficult to design devices that need high flexibility.
• FR4 is a hazardous material and has a toxic nature and can affect the environment if not accurately disposed of.

Limitations of FR-4

• It does not have features to handle high temperatures due to low thermal conductivity.
• It does not work well for high-frequency projects.
• Its dissipation factor is high, which causes signal losses.
• It does not support controlled impedance.
• It has a varying dielectric constant than other substrate materials.

Why Choose FR4 PCB?

Low Cost:

• FR4 board material prices are lower than those of other materials like metal e metal substrates. It makes the best option for different board types: simple designs, complicated, and multiple boards.

Mechanical Strength:

• The FR4 board is strong and can handle high components. So it is used in harsh conditions.

Moisture Resistant:

• FR4 board has resistance to moisture with a non-zero absorption rate. So they are used in humid conditions.

Flame Retardant: 

It has a high flammability rate of about UL94-V0, and the FR4 board does not make safe materials.