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Is FR4 the Best Board Material for Your Design

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Is FR4 the Best Board Material for Your Design

July 24, 2023

In the world of electronics and printed circuit board manufacturing, choosing the right substrate material for your design can mean the difference between success and failure. FR4 substrate, with its excellent mechanical strength, electrical insulation, and resistance to heat and chemicals, is widely used in the industry. In this article, we will explore the properties and advantages of FR4 substrate, its use in printed circuit boards, as well as some limitations and tips for selecting the right FR4 material.

What Is FR4 Substrate Material?

FR4 substrate stands for "flame retardant 4" which indicates that FR4 substrate is made to resist the propagation of flames and meets certain fire safety standards. FR4 lame retardant devices are used where fire safety is a concern like in electronics or electrical systems and flame retardancy acts as an added safety where there is a risk of fire accidents. It is a type of substrate that is used in the making of electrical components and is widely used in the manufacturing of printed circuit boards. This type of substrate has fiberglass as one of its components which provides mechanical strength along with epoxy resin The combination of the two materials acts as an insulating matrix. FR4 substrates provide excellent electrical insulation, mechanical strength and protection for the electrical components on the board. They are resistant to heat and chemicals which makes them suitable to be used in various applications. FR4 substrates are best known for their durability, and mechanical strength which provide the board with dimensional stability and resistance to chemicals and moisture. They are widely used because of their high performance and cost-effectiveness. They provide excellent electrical insulation which results in reduced risks of short circuits and increases reliable signal transmission. FR4 substrates can hold their shape under different conditions due to their dimensional stability, which acts as an essential part of the proper mounting of electrical components on the printed circuit boards.If you want to have your own FR4 substrate you can grab it on JLCPCB's website, the researchers in the JLCPCB lab work efficiently and deliver their best quality products in 2-4 working days.

(Image credits: Jichangsheng Technology)

What are the properties of FR4 substrate?

It is the properties of an FR4 substrate that make it so useful and so unique Among all the properties we will be discussing a few of them:

GOOD DIELECTRIC PROPERTIES: FR4 substrates offer high resistance to electrical current flow; due to the high resistance signal loss issues and interference between the circuit pathways are minimized.

TEMPERATURE RESISTANCE: FR4 can withstand relatively high temperatures commonly up to 130 degrees to 140 degrees; this property enables the use of FR4 substrates in devices where elevated operating temperatures are involved.

CHEMICAL RESISTANCE: FR4 substrates exhibit good resistance to a lot of chemicals including different acids which are commonly encountered by the substrate during the electronic manufacturing processes. This resistance helps the substrate from being damaged during such operations.

FLAME RETARDANCY: One of the substrate's main properties is its flame retardancy which allows the substrate to withstand ignition and will also not contribute to the spread of fire in case of an incident his property is crucial for safety purposes n electronic devices.

MECHANICAL STRENGTH: The fiberglass gives the FR4 substrate mechanical strength and dimensional stability his property prevents the substrate from being bent during the assembly of the printed circuit boards.

ELECTRICAL INSULATION: FR4 substrates provide excellent electrical insulation therefore they are ideal for devices that require insulation between conductive elements.

MACHINABILITY: FR4 substrates have good machinability which means that they are easily processed; these substrates can be drilled, machined and etched to create complex PCB designs.

COMPATIBILITY: These substrates are mostly compatible with common PCB manufacturing processes like drilling or soldering, plating and then the placement of electrical components on the board; it is due to this property of FR4 substrates that they can be easily machined.

DIMENSIONAL STABILITY: FR4 exhibits minimal dimensional changes during extreme weather conditions like extreme humidity or varying temperatures, this stability ensures the substrate is stable and makes it reliable to be used in various devices.

AVAILABILITY: FR4 substrates are easily available in the market you can also easily grab them online; one of the trusted sites is JLCPCB which allows you to grab your required product with your product being safely delivered straight to your house; this property makes it easier for designers to select and work with their desired FR4 substrate.

THERMAL CONDUCTIVITY: Thermal conductivity is the property of FR4 substrates that allows them to dissipate heat as much as they can from electrical components.

ENVIRONMENTALLY FRIENDLY: Due to their flame retardancy and durability, FR4 substrates are generally considered to be environmentally friendly.

How Is FR-4 Used in PCBs?

There are some steps as to how to make an FR4 PCB which we will be discussing As an overview of how FR4 substrates are being used in PCBs manufacturers use FR4 substrate material as a base to provide a sturdy platform for mounting electrical components on the board, Copper traces which are also added on the FR4 sheets to increase electrical conductivity are added, the sheets acts as an insulating layer between the copper traces which ensure proper signal transmission Now let us discuss the procedure in a few steps.


The designing procedure involves designing the PCB circuit pattern through specialized software in which the placement of different electrical components are specified and all the necessary designing is done in this step.


Step 2 involves the prepping of materials before the manufacturing of the board FR4 sheets are selected based on desired thickness and other specifications.


The substrate FR4 sheets are prepared They are treated to be more adhering and cleaned, to improve the quality of the FR4 sheets many processes may be involved.


Copper is added to the FR4 sheets to create conductive pathways which means to allow power distribution and electrical signals on the circuit.


After adding copper to the FR4 sheets transferring the PCB design comes next, this process uses a photographic process involving ultraviolet light.


Unwanted copper is removed from the board and the desired copper stays intact.


Holes are drilled in the FR4 to interconnect various layers of PCB The holes are plated with a thin layer of Copper for electrical conductivity and soldering Soldermask is added on top of the copper traces where it is required to protect the copper traces from oxidizing and improve insulation.


T help with soldering and to avoid oxidation, the PCB is treated with a surface finish.


Marking like the logo or any other important markings are printed on the PCB. The markings are commonly called silkscreen.


The made printed circuit board undergoes various tests to ensure its smooth operation, quality and functionality.

This completes the manufacturing of the boards. A point to remember is that different procedures may be carried out by different manufacturers for different printed circuit boards, these steps won’t be the same for the manufacture of every printed circuit board.

When is FR4 Not the Best Material For Your Board?

A question may arise in your mind as to when is FR4 substrate not good for my device or when it is not the best choice for my boards because as far as we have discussed up till now we can only see its advantages, what are its limitations? Here are some reasons why your FR4 substrate might not be the best for you.

HARSH ENVIRONMENTS: Yes, FR4 substrates are resistant to chemicals and or extreme temperatures but when the limit goes beyond the capabilities of your substrate as it's exposed to corrosive chemicals it will no longer fulfill your desires and you will have to find an alternative to an FR4 substrate.

HIGH FREQUENCIES: the FR4 substrate won’t work when your device requires very high-speed signals or microwave frequencies range ther substrate options like a ceramic-based substrate would be better than an FR4 substrate.

HIGH TEMPERATURES: FR4 substrates offer limited temperature resistance, so if your device needs to be operated in a very hot environment then these are not for you as they will not be able to perform in an extremely hot environment.

THINNER DESIGNS: This substrate will not be suitable in working for such designs that are very thin or very small ther alternatives like a flex printed circuit board may work.

These are some of the reasons why the FR4 substrate may not be the best for your board hese also vary based on the PCB designer, as well as different requirements and varying specifications which may impose limitations which will cause the FR4 substrate to not be beneficial for you.

Tips for selecting the right FR4 material

Here are some of the tips that will make you choose the right FR4 substrate.

THICKNESS: The thickness of the FR4 sheets determines whether you want more mechanical strength for your board made possible by thick sheets or you want a more compact design which will be possible by using thin FR4 sheets.

GLASS TRANSITION TEMPERATURE: Glass transition temperature is a very important property of an FR4 substrate This is the temperature where the substrate material transitions from a rigid to a flexible state. You should choose a substrate with a high enough glass transition temperature to avoid performance issues or other problems.

COPPER WEIGHT: Varying copper weight means different current carrying capacities for your design. Heavier (thicker) copper weight is used for better conductivity but heavier copper also makes the substrate more costly and also adds to the manufacturing challenges ighter copper weight enables less conductivity but the substrate gets cheaper.

FLAME RETARDANCY: Be on the lookout for those FR4 substrates that meet industry standards to comply with safety standards and regulations.

COST CONSIDERATION: Cost may vary depending on the different specifications of the substrate so be on the lookout for cheaper substrate if your work is not as professional and go for the pricey ones when your work is professional.

SUPPLIER SUPPORT: Make sure that you are in direct contact with the supplier who gave you your substrate because the know the best regarding the compatibility of the substrate with your printed circuit board design.

In summary, FR4 substrate is an excellent choice for your printed circuit board designs, providing reliable performance and cost-effectiveness. Its properties like good dielectric and chemical resistance, flame retardancy, mechanical strength, and dimensional stability make it an indispensable material in the industry. However, it is important to consider its limitations in chemically harsh environments, high temperature, and thin designs when selecting the right material. By following some useful tips like considering thickness, glass transition temperature, copper weight, flame retardancy, cost, and supplier support, you can make the most out of your FR4 substrate and achieve high-quality PCB manufacturing.