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PCBs boards are laminated composites made from non-conductive substrate materials with layers of copper circulatory buried on the internal or external surface. The substrate most commonly used in a printed circuit board is a glass fiber reinforced epoxy resin.

In this topic, we are going to discuss more of the materials used in the manufacturing of PCB boards.

Types of materials used

The primary materials used in the manufacture of PCBs boards are of importance. It’s essential to consider the materials in terms of temperature resistance, flexibility, tensile strength, dielectric constant, and many other factors. These materials include;

1. FR-4
2. PTFE(Teflon)
3. Resins
4. Polyimide
5. Kapton

1. FR-4

These are the most used substrates for Printed circuit boards. However, it does not refer to the type of material but refers to the grade of materials.

• FR-4 is a grade designation for glassed epoxy laminate material. Once all the materials are fixed to each other, the board is laminated with copper foil before going into the PCB manufacturing process.
• It is composed of fiberglass cloth and epoxy resin bind which is flame resistant. The glass epoxy of FR-4 is known to be adaptable high-pressure thermoset laminate with good strength to weight ratios.
• It is one of the most popular materials used in making PCBs. FR-4 stands for flame retardant where the number 4 effeminates materials from the same group. It stands for the grade used to make the laminated sheet. FR-4 is a fiberglass reinforced epoxy that looks like a thin sheet.

The FR-4 is the most popularly used due to its low cost and versatility of the material. FR-4 are electric insulators with high dielectric strength and also a high height strength weight ratio.

Subclasses of FR-4

FR4 materials are divided into several subclasses which are done according to their specifications:

1. High glass transition: also known as Tg and the temperature where fiberglass gets unstable.
2. Standard: Standard FR4 PCBs are made of a certain

• Halogen-free: this is an FR-4 board that is made with no toxic bromine.

Properties of FR4 PCB material

• Versatility: FR4 is used in different types of PCBs boards including single layer, multilayer, single-sided, and double-sided PCBs.
• Chemically resistant: This material is resistant to corrosion. Also, FR4 materials don’t absorb water as compared to other materials thus increasing their resistance to chemicals.
• Strength to weight ratio
• Dimensional stability: this material is is affected by vibrations and pressure hence they hold its physical shape very well.
• Good electric insulator: FR4 has good electrical properties which make it a better choice for man electrical engineering applications.

Limitations of FR4

Despite being the least expensive and providing enough electric insulation. When used in high-speed applications may cause the following problems;

1. Temperature stability – FR4 is not recommended for devices with high temperatures. They also do not support lead-free soldering because of the reflow temperatures
2. The insulating stability – FR4 being a great insulator has limits when exposed to high voltage if it reaches a certain limit more than required the properties will defect and start conducting electricity instead.
3. Controlled impedance – FR4 imposes challenges while maintaining the impedance value since FR4 does not offer, a uniform dielectric constant like high-speed board materials. FR4 material is not the preferred choice for controlled impedance boards
4. They have a low thermal conductivity: FR4 PCBs may have some trouble when it comes to heat dissipation hence affecting its thermal conductivity properties.

FR-4 is used in the PCB when they form a primary insulating backbone. Once the manufacturing company prepares the circuit, the FR4 board is laminated with layers of copper foil using heat adhesive.

Advantages of FR 4 materials

1. Costly friendly when compared to other materials resulting in lower production costs overall
2. Wide range of operating temperatures: FR4 materials can withstand high temperatures without losing their properties.
3. Compact and easy to design
4. Moisture resistance
5. Strong plastic fastener materials

Applications of FR-4

1. Low-frequency applications due to their compatibility and low cost.
2. DC board application: Due to excellent accessibility and performance most of the DC boards are completed with FR4. The low cost of the FR4 board compared to boards made from other materials is also a factor.
3. Digital applications: this digital application include consumer electronics appliances such as mobile phones and Television.

 

2. PTFE (Teflon)

Teflon is the highly useful plastic material polytetrafluoroethylene (PTFE) trading name. PTFE semi-crystalline polymer is made up of a carbon backbone surrounded by fluorine atoms. These fluorine atoms act as a barrier and are responsible for the high corrosion resistance. Teflon PCB material can resist high temperatures. Due to this, it is commonly used in high-frequency PCB.

PTFE exhibits different properties which we are going to look at below,

Properties of PTFE

• Low-temperature resistance: PTFE has a great mechanical toughness when at low temperatures below the standard it can remain elongated
• Non-stick: PTFE is a combination of carbon and fluorine atoms attached to every carbon atom. This nature makes it to be less reactive making it non-stick.
• Exceptional electric properties: this material offers volume resistivity and high breakdown voltage. It features high dielectric loss and dielectric constant over high frequency.
• Low water absorption rate: they have a low absorption rate and hence can be used in humid environments.
• Chemical resistants: PTFE material can withstand chemicals. Board made with PTFE can be used in a chemical reagent environment.
• Fluoropolymer or Polytetrafluoroethylene (PTFE) is used in products with high frequencies with low dielectric constant. Their performances can be demonstrated in the table below

Advantages of PTFE material

PTFE manufacturers add a variety of components into blends like carbon fiber, glass bronze, and many others to strengthen weak characteristics of materials. is useful material in the manufacture of PCB boards. Some of its advantages compared to other materials are;

1. Temperature resistant: Teflon substrate can maintain its properties in both cold and extreme conditions. This explains why the PCB board made of this substrate is used in the military.
2. Great dielectric strength: high dielectric strength makes it nonconductive. The insulating capability of this material protects equipment from electric breakdowns

• Durability: PTFE material can withstand oxidation and ultraviolet rays. It is a cost-effective option because of its long-lasting nature.

Disadvantages of PTFE material

there are some advantages of PTFE that give the products some limitations.

1. Produces toxic fumes when overheated
2. Price: PTFE is not a low-cost polymer
3. It can change shape under pressure

Teflon is one of the most commonly used materials in the electronic industry. PCB boards made of Teflon are used in several applications due to their benefits.

3. Resin

Resins are sticky substances that are converted into rigid polymers using the curing process. Resins are made synthetically. Synthetic resins are made up of several classes. Some are made by the esterification of the organic compounds

Some resins find used in PCB board manufacturing; the industry leader in demand on manufacturing platforms. In this article, we are going to discuss the types of resin and their properties.

Polyester resins

They are very flexible with good resistance to heat, flames, and chemicals

Polyamide resins

Polyamide resins are easily molded, strong and resistant, and lightweight. The resin polyamide has a low friction factor and is free from scrapping and resistant to the chemical.

Polypropylene resins

They have low density and good heat resistance. They can be sterilized. Polypropylene resins are also resistant to chemicals.

Epoxy resins

They have copper-clad laminate (CCL) as a substrate material used in PCBs. Epoxy resin both its structure and performance play an important role in determining the performance of CCL. With the fast development of the electronic industry PCB fabrication technology moves towards high density and multiple layers thus laying higher requirements on dimensional stability and dielectric loss bringing new demands on the performance of the epoxy resin.

Epoxy are materials that make up the green board that houses the components, resistors, and connections needed to run the entire operation.

Properties of epoxy resins

When two or more objects must adhere to every other over an extended period the simplest thanks to accomplishing this is often by use of epoxy. Epoxy exhibits both physical and chemical properties as discussed below

Chemical properties of epoxy resins

• Epoxy resin differs in mass. The relative molecular mass of a resin over 700 is brought up as a high molecular, while epoxy with a lower mass of under 700 is termed low molecular. Epoxy resins will be allergens. The lower the mass the lower the probability of allergies.
• A molecular epoxy glue with a median mass of 380 is liquid at hospital temperature, while an epoxy with a mean relative molecular mass of 1000 is solid at hospital temperature. The mass determines what the synthetic resin is often used for

Physical properties of epoxy glue

• Resins generally occur in an amorphous state
• They generally become soft at heating

Advantages of resins on PCBs

• Resins are employed in high voltage electronics and electronics which operate within the explosive environment to supply a dielectric layer to forestall arcing
• Protects the PCB against high humidity and condensation
• With good dielectric constancy, it acts as an insulator
• Epoxy coating prevents metal within the PCB from rusting and corrosion

Disadvantages of resins on PCBs

• While epoxy provides reliable exterior film protection for PCBs, its long-lasting surface durability also makes it very difficult to remodel and repair; repair costs are high compared to most conformal coating
• Extreme temperature during operation significantly lower epoxy’s stress resistance.
• Not recommended within the coating of components whose operating conditions are water, salt spray, and mist

 

4. Polyamide

Many companies consider the utilization of polyamide in the making of the computer circuit board. Several polyamide PCB materials’ properties fit well with the board application of their industries.

 

What is polyamide PCB material?

Polyamide is additionally referred to as polyimides. they’re polymers consisting of imide monomers, the varied groups of this polymer have various metals both natural and artificial. In PCB manufacturing the polyamides used are synthetically mass-produced.

Properties of polyamide PCB material

Polyimide is highly in demand, most notably thanks to the material’s strength. There are different considerations to think about when choosing the most effective application required for the PCB characteristics of your choice. They include

1. good tensile strength: even with the flexibleness of the polyamide material they’re strong and proof against wrapping which makes it a superb choice for many applications that will need some physical strength.
2. Flexible: rigid-flex computer circuit boards and other flexible boards are commonly produced with a polyimide material. because the fabric is exceptionally flexible.
3. iii. Highly durable: other than being proof against chemicals and warmth.
4. Temperature resistant: polyamide is far more stable in an environment of extremely high temperatures
5. immune to chemicals: meaning they can not corrode easily even if exposed to corrosion.

Applications of the polyimide printed circuit board materials.

Polyamide material can be found in consumer products, clothing, and vehicles. However, they are commonly known for their use in printed circuit boards. Specifically, polyamide boards are used to create flexible and rigid-flex PCBs, which are known widely.

Some of the wide range of applications in the PCB board manufacturing industry are discussed below

1. Military and aerospace electronics: Aerospace and military applications prefer polyamide materials for PCBs because of their reliability, thermal stability, and flexibility. This is both due to the frequent necessity for field repairs as well as the physical stressors involved in these industries which other PCBs material are less suited for.
2. Automotive electronics:
3. Consumer electronics: such as tablets and smartphones are made up of flex and rigid-flex PCBs which are made up of polyamide material.
4. Medical industry electronics: medical applications require some amount of flexibility in the electronics used, for example, implants, prosthetics, and imaging technology, which tend to require more movement.

4. Kapton

Kapton is a polyamide used in the manufacture of flexible printed circuit boards. A flexible printed circuit board is made by using a thin layer of the polymer film of Kapton with a conductive pattern of traces on the substrate.

Kapton is used in the manufacturing of electric devices due to heat exposure. Kapton is a flame retardant and highly versatile material which can withstand harsh conditions to offer effective circuit board labeling every time.

Advantages of Kapton PCB

1. Kapton circuit is flexible, it can be bent, move, and have a torsion effect also. And the conductivity would not be affected by this flexibility.
2. Kapton is designed in such a way it can meet higher and smaller density mountain designs and can improve flexibility.
3. Stability and strength can be enhanced by reinforcing the base material of the circuit. There is a solution is ranging from single base Kapton circuits to multilayer printed circuit boards.
4. Boards made of Kapton can reduce their size which is why are preferred in most applications such as laptops, aerospace, and other digital devices.

Properties of Kapton

• Highly durable: It has a higher level of resistance against temperature and many other chemicals which makes it highly durable.
• Excellent stability of thermal power: Kapton polyimide can deal with temperature exposures of electronic devices. Due to this, electronic devices made with Kapton board can work in high temperatures
• Highly flexible: Kapton printed boards can be moved and bend easily.

Characteristics of Kapton

1. Kapton is highly effective
2. It has good radiation a chemical resistance
3. It is stable even in the high range of temperature
4. Well suited for diverse applications
5. It has excellent mechanical, physical, and electric properties which make it an excellent choice for demanding industries

Conclusion

The printed circuit board has led to the manufacture and revolution of modern electric devices. This has been contributed by the properties of the substances used in the making of the PCBs substrate material, the low cost of the materials being one of the major factors. Circuits boards have contributed greatly to both mechanical and electrical features due to this they are essential for use in most applications.

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