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Features of FR-4 PCB Material: A Practical Guide to Select PCB Materials

FR-4 PCB composition

When it comes to fabricating printed circuit boards in today’s world of cutting-edge electronics, selecting the correct type of PCB materials is crucial. In this detailed article learn everything about the composition of PCBs, the most prevalent types of PCB materials, and the most important aspects you should keep in mind when selecting PCB material choices for manufacturing. 

This article provides a practical guide for the selection of right PCB materials but if you want to avoid costly delays and mistakes in the PCB design process, it’s best to acquire some expert advice right from the start. ELE PCB is here to fulfil all of your PCB material needs.

Table of Contents

1. Basic Composition of PCB

Basic composition of a typical PCB

PCB Materials are chosen based on their electrical and thermal qualities, which are essential for the board to function according to the design rating. The form factor and the number of layers on the board are both determined by the schematic. A sophisticated PCB, at least, will have following layer composition,

Substrate Layer: It is the main insulating and supporting material layer for the whole PCB. The thickness of this substrate layer, which provides a sturdy base for printed circuit boards, varies depending on the intended purposes of the board.

Conductive Layer: In most cases, the PCB is fabricated by depositing a very thin layer of a metal such as copper on the surface of the insulating material.

Solder Mask Layer: It is an additional layer on the top of conductive layer. Contacting pads on PCB need this insulating layer to prevent shorts to other conductive components.

Silkscreen Layer: This layer of printing epoxy is used for printing symbols or any informative text on solder mask. A silkscreen can be used to read cautionary signals, identify parts, and determine assembly locations.

2. Properties of PCB Materials

When the high-quality PCB materials are used to fabricate a printed circuit board, not only will it function properly, but it will also survive for the lifetime of the product. Following are some important properties of PCB materials.

Electrical Conductivity: Conductive metal normally have high conductivity to reduce the resistance of tracks. Copper is the main used conductive material having good electric conduction properties which do not require any further explanation.

Thermal Conductivity: Substrate material should have low thermal conductivity constant. This PCB material should help in NOT spreading the heat of one electrical component to nearby components.

Flexibility and Strength: PCB material needs to be rigid and mechanically a little flexible as during operation the material can be prone to effect of thermal elongation and should not develop cracks causing traces to break.

Substrate is the only major PCB material that is considered the backbone of entire PCB as it has to provide support and some extra thermal efficiency.  From hereafter, we will focus on the substrate as the main PCB material.

3. Common Types of PCB Material

PCB manufacture relies heavily on the careful selection and integration of PCB materials. While there are literally hundreds of various materials from which to pick depending on budget and technical needs, some of the most common PCB materials are listed here.

3.1 Cellulose Based Composite Materials

  • CEM-1
  • CEM-2
  • CEM-3
  • CEM-4
  • CEM-5

3.2 Glass Reinforced Epoxy Laminate Materials

  • FR-1
  • FR-2
  • FR-3
  • FR-4
  • FR-5
  • FR-6

3.3 Teflon Based Materials

  • PTFE

3.4 Polymer Materials

  • Polyimide

3.5 Metallic Materials

  • Alumina

4. Most Commonly used PCB Materials

Different materials have different properties and their use depend on the design and environmental requirements. But some of these PCB materials are mostly used due their best and economical properties. Following are some commonly used PCB materials.

4.1 FR1 & FR2

These Fire-Retardant materials are utilised only for single layer PCB and is fabricated using paper and phenol chemicals. The glass transition temperature is the only distinguishing feature between FR1 and FR2. FR1’s Tg is greater than that of FR2’s glass transition state. 

4.2 FR-4

The National Electrical Manufacturers Association (NEMA) has established FR-4 as the standard for a glass-reinforced epoxy resin laminate. 

4.3 Polyimide

The temperature endurance of polyimide laminates is superior to that of FR-4 materials, and they also exhibit a minor increase in their electrical performance characteristics. Polyimide materials are more expensive than FR-4 materials, but this PCB material offers enhanced endurance in hostile and higher temperature conditions. As a result of their improved stability during thermal cycling and reduced tendency towards expansion, these materials are well suited for structures with a greater number of layers.

4.4 Teflon – PTFE

Teflon possesses outstanding electrical characteristics for PCB, which makes it well suited for use in high-speed circuits applications. Teflon material is more costly than polyimide. PCBs made of Teflon can also be coated with fabric glass other additives to increase their mechanical strength. In many cases, the production of Teflon based PCBs calls for a workforce with a specific set of skills, specialized equipment, and procedures.

5. Best of PCB Materials

When selecting best PCB material for all sorts of PCBs, whether for household electronics or industrial equipment, quality is of the highest importance.  Furthermore, what is most vital is that the PCB material in question provides exceptional levels of excellent performance throughout its planned working life.

FR-4 is the most frequent material used in PCBs. This epoxy-based PCB material is both fire and water resistant. It has a high strength-to-weight ratio. This material has an extremely high tensile strength.

6. FR-4 PCB Material

FR-4 is a composite material that is flame resistant. It is made of woven fiberglass fabric that has an epoxy resin acting as the binder. Since its introduction at least fifty years ago, FR-4 has undergone significant development, and it is now capable of withstanding continuous temperatures of up to 180 degrees Celsius. FR-4 has the benefit of having an excellent resistance to weight ratio, which is a distinct advantage. It does not absorb water but maintains a high mechanical strength and maintains an excellent insulating capacity regardless of the surrounding conditions, whether they are dry or wet. This PCB material is particularly common for printed circuit boards that have lower layer counts, such as single-sided, double-sided, or multilayered structures that have less than 14 layers.

FR-4 PCB composition

As a foundation material for printed circuit boards (PCB), FR-4 sheets are quite popular among electrical engineers and designers. The widespread use of the material may be attributed to the fact that it is both inexpensive and adaptable, in addition to possessing an abundance of advantageous physical qualities. FR4 sheets have a high dielectric strength and can be used as electrical insulators. In addition to this, they have a high strength-to-weight ratio, are not affected by the presence of moisture, and are lightweight. When you combine this quality with their relative resistance to temperature change, you can see how FR4 material may function effectively in the majority of environmental circumstances.

Some benefits of FR-4 are listed as follows,

  1. It is the most often utilized dielectric substance used in PCB board fabrication.
  2. Single, double, and multilayer PCB boards with a temperature range of 50 to 150 centigrade employ FR-4.
  3. It is Flame retardant.
  4. It has a variety of properties, depending on the manufacturer, but its most popular features include liquid resistance and great mechanical strength.

6.1 Features of FR-4 PCBs

The term FR-4 stands for flame retardant, and the number 4 designates a rating that distinguishes the material from others. FR-4 is a woven, thin epoxy fiberglass-reinforced laminated sheet used in the production of PCBs. The substance’s FR-4 composite fiberglass layer structure, which gives it rigidity and stability. The following benefits of FR-4 make it a popular material with OEMs and PCB producers. Let’s look at them in the context of that.

Great Electrical Characteristics

Electrical properties of circuit board materials are essential in signal impedance and integrity calculations because they influence how rapidly an electrical signal moves through a material. The high dielectric strength of FR-4 is what gives it its electrical insulating properties. The thickness, kind of fiberglass weave, and resin employed all affect the FR-4 Dk, which varies between 3.8 and 4.8 MHZ. 

Retardant To Flames

A flame retardant can be used in a wide range of production procedures and produce reliable results. Due to its superior electrical, thermal, and mechanical properties, FR-4 is a preferred material for many electronics applications.

Absorption Of Moisture

This is one of the most important properties of the FR-4 material. When submerged in water, the material absorbs moisture at a minuscule 0.10% rate. The FR-4 is primarily resistant to moisture, but it is also temperature resistant and can withstand a wide range of temperatures.

Cost Efficiency

FR-4 is a well-known foundation material for circuit boards because of its inexpensive cost and stable chemical and physical properties. This benefits a lot of PCB manufacturers and designers that are concerned about costs.

7. Considerations to Select Best PCB Material

It is critical to carefully select the best type  of PCB material to ensure that the PCB has the appropriate electrical, thermal, and mechanical characteristics for durable application. While selecting appropriate PCB material, consider following characteristics in mind.

7.1 Design Requirements

Think through the PCB’s intended use, intended environment, signal integrity requirements, and overall design. Do high temperatures need to be tolerated? Is a stiff or pliable board better for your needs? One thing that matters the most is that the PCB material should be insulating.

7.2 PCB Thickness

Basically, the thickness depends on the project you’re working on; printed circuit boards, for example, frequently employ the thinnest boards. PC board thickness reduces stress. Ideal FR-4 thickness would be close to 1 to 3 inches. Because thin boards impose certain constraints on PCB layouts, they are not always the best option. This is the primary reason why thin boards are not always preferred. Grooves are impossible to implement on thin FR-4 circuit boards because of the risk of cracking, and the grooves themselves cannot be too big. However, thicker boards are capable of achieving both of these goals. Always remember to take this into consideration when choosing between different FR-4 thicknesses.

7.3 Impedance matching

Impedance or frequency matching is crucial for low-frequency or high-frequency printed circuit boards in electrical and electronic equipment. Paying closer attention to those details would make the boards more logical and safer to operate. It can also provide information on the capacitance of multisided boards.

7.4 Spacing

Space conservation is a key consideration when constructing FR-4 printed circuit boards. Spacing is crucial for Bluetooth gadgets and USB ports. For designing, we mostly used the thinnest boards.

7.5 Flexibility

In comparison to thicker boards, thinner ones are more flexible. Due to their flexibility, thin boards were more commonly employed in manufacturing than thick ones. When utilizing FR-4, there is a significant risk if the substrate is very thin, and the FR-4 PCB’s area or dimensions are greater. Stress can be reduced in thin FR-4 PC boards used in electrical and electronic devices. Thinner boards are more pliable and heat sensitive. It may be bent to a desired angle while soldering.

Flexible FR 4 PCB

7.6 Weight

For smaller or lighter items, FR-4 PCB thickness will determine its weight, and vice versa. Thermal conduction is a crucial concept to understand when using FR-4 PCB. Additionally, it is influenced by the temperature. The thermal coefficient of the dielectric medium, also known as the dielectric constant, should be considered when determining the temperature. FR-4 is highly well-liked because of its great heat resistance. It stands to reason that the thickness of the FR-4 will have an impact on the total weight of the PCB. Although weight is less of a concern in other applications, it is typically something that is thought about when designing consumer electronics. PCBs that are lighter lead to goods that are lighter, which in turn makes the items cheaper to ship and, in certain situations, more appealing to customers.

7.7 Heat Transfer

When it comes to a PCB’s durability and performance, power and heat are two of the most important aspects. Be sure to check the thermal capabilities of the PCB material you’re considering for the actual design. Overheating is a common problem in many modern devices due to the high-speed impulses.

7.8 Mechanical Durability & Strength

It’s crucial to think about the PCB materials’ mechanical and electrical durability. CTE is also very important in the field of microelectronics. Consider the factor that how long do you think the PCB’s materials will last in your working environment.

7.9 Cost

When selecting PCB material, its cost factor is considered to be most crucial. Gold or solder tabs are often used by many designers. The price of gold tabs, however, might be prohibitive for some. Buried vias are often less expensive than blind vias. To sum up, while looking at line and breadth spacing at six mils or greater, there are additional expenditures. PCB bases are often made of FR-4 material because of its widespread availability and the reasonable cost it maintains. On the other hand, high-frequency laminates come at a price that is noticeably higher than average, which is a big disadvantage for manufacturers and designers who are worried about costs. When it comes to deciding between FR-4 and high-frequency laminates, this is the key limiting element that organizations must consider.

Get Pricing and Lead Time Here.

ELE PCB is able to fulfil all of your needs for HDI PCBs, beginning with the prototype phase and continuing all the way through the production process. Because of our knowledge and experience in the field of manufacturing multilayer printed circuit boards, we hold a significant advantage over our competitors in the industry of generating printed circuit boards. In addition, we never promise a price that is greater than the prices offered by our rivals, and we never require customers to buy a certain minimum amount of any product with each order that they place.

8. ELE Technology Co. The Leading PCB Manufacturer

Prototyping printed circuit boards is a useful technique for designers since it helps save time and money while guaranteeing a high-quality result. Get in touch with ELE Company Limited right away if you need PCB prototype services for an upcoming venture.

Over 6,000 engineers and 300 contract assemblers from across the world rely on ELE PCB for their PCB prototype services. We pride ourselves on our dedication to quality and our ability to consistently provide fully functional prototypes that meet or exceed your requirements. Whether you need a simple two-sided FR-4 board or a very complicated multi-layered prototype, our PCB design professionals have you covered. Your prototype may be provided by ELE PCB promptly, proficiently, and cheaply, with no hidden expenses.

Our method is straightforward; we utilize CAD software to plan the layout of the prototype, select the manufacturing material, and then cut and assemble the board. After that, the circuit board is complete and ready for testing. And when the time comes, we’ll assist you in making the jump from prototype to production.

ELE PCB is here to assist you if you’re in the market for professional PCB prototype services. Get in touch with us now and talk to a member of our service team about your PCB prototyping needs and how ELE PCB can fulfill them.

9. PCB Manufacturing Services Offered by ELE

We are expert in PCB manufacturing, and we offer a wide range of manufacturing services including the manufacturing of following types of PCBs,

  • FR-4 PCB
  • Multi-layer PCB
  • Flex PCB
  • Rigid-Flex PCB
  • Metal Base PCB
  • Impedance Control PCB
  • High Density Interconnect PCB
  • High Density Multilayer PCB
  • High-TG PCB
  • Heavy Copper PCB
  • Special PCB-Advanced High Frequency PCB

Our team of highly trained engineers performs a DFM check on every Gerber file that is provided. In accordance with IPC-A6012 Class 2 or other standards, each PCB is put through the quality assurance process. Choose ELE Technology today, and you will save a lot of time on your project and work. 

Click Here for a comprehensive rundown of the PCB fabrication capabilities offered by ELE Technology Co., we cherish you as a client and look forward to serving you for the many next years to come.

CONTACT ELE

ELE PCB has got the IS09001:2015, IS013485:2016, ROHS and FCC certifications. We can offer all kinds of services, including PCB manufacturing and PCB assembly, sample orders and batch orders. For PCB assembly, utilizing 7 high-speed SMT PCBA lines from Yamaha and Sony, to meet our customers’ needs. Our extended services include PCB design &PCB Layout, hardware design engineering, firmware &software development, and personalization. ELE company is honored as an excellent supplier from any company all around the world. We deeply believe that our good service and experience will completely meet your needs. Integrality, value and innovation are the forces that drive our success.

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About Michael

Michael is the general manager of ELEPCB, a leading PCB design and manufacturing company based in China. He has over 10 years of experience in the PCB industry, and has been involved in various projects.

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