What’s not to love about FR-4 It is well-known as one of the strongest plastic materials available.  As we’ve written in this blog before, FR-4 rivals the strength of some metals.  The Ultimate Tensile Strength (UTI) of FR-4 is 45,000 PSI while the UTI of cast iron is 29,000 PSI.  Copper comes in at 31,900 PSI and aluminum is 43,500 PSI.  Structural Steel has an UTI of 40,000 PSI.

FR-4 a material made of a woven glass fabric and a difunctional  epoxy resin system.  It is an anisotropic or directionally dependent material. The standards for FR-4 are regulated by the National Electrical Manufacturers Association (NEMA.)

There’s so much more to the engineering might of FR-4 than just strength!  It’s a very well-rounded material.  Here are the top 6 reasons why FR-4 is a great material-we think you’ll love it.

1. FR-4 stands for flame resistant.  UL give this material a rating of 94 V-0.  Bromine, an oxygen scavenger, is added to G10 to create FR-4, giving it the highest flame retardant rating on the UL 94 V index.  Burning stops within 10 seconds on a vertical specimen after two applications of a blue flame and drips are allowed as long as they are not burning.  FR-4 will prevent a fire from starting.  If a fire is already burning, this material will slow it down.

2. FR-4 is chemically resistant.   FR-4 performs excellently in a wide variety of chemicals including most alcohols, aromatic hydrocarbons like benzene and toluene, nickel plating materials, and in such acids as hydrofluoric 100% and hydrochloric 100%.  The complete list of chemicals that FR-4 resists is quite long.  For more information on specific chemical resistance, check out our High Performance Material Guide.

3. FR-4 is water-proof.  With a water absorption rate of almost zero percent, it is no surprise that FR-4 is inert in water.  FR-4 is even saltwater resistant, making it ideal for use in marine equipment. It is used to make fish farming pods, boats, fishing rods, railings for sewage treatment plants, and more.  FR-4 has also been used in international undersea communications cable applications.

4. FR-4 is nonconductive.  Because of its extremely low water absorption, FR-4 is an outstanding insulator.  In both wet and dry applications, it has good dielectric loss [i]properties and good dielectric strength.[ii]  It is used extensively in the manufacture of circuit boards but because ii can be easily machined it is made into screws, nuts, spacers and a variety of shapes used for electrical insulation purposes.

5. FR-4 is light weight.   As it is made of woven fiberglass cloth and epoxy resin is light weight with a specific gravity[iii] of 1.8 compared to 2.7 of aluminum.   Cast iron has a specific gravity of 7.2 while copper is 8.96 and steel is 7.82.

6.  FR-4 is UV resistant.  This point refers specifically to grades of FR-4 that are made with a tetrafunctional epoxy system.  This kind of FR-4 is the type most often used for circuit boards.   UV resistance makes FR-4 even more ideally suited for underwater and marine applications.

[i] Dielectric loss is the amount of heat an insulating material dissipates when subjected to an electrical current.

[ii] The dielectric strength of a material is the maximum electrical field strength it can withstand without loss of its insulating properties.

[iii] Tetra functional describes a compound having four bonding sites in a molecule.

(Are you looking for more engineering term definitions?  Check out our Plastic Manufacturing Terms Glossary!)

Have you used FR-4 in your applications?  Let us know what your experience with FR-4 has been in the comments below.

Do you have more questions about FR-4?  Sign up for a complimentary Material Consultation and let our engineers answer them for you!



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