FR-4
Encyclopedia
FR-4 is a grade designation assigned to glass-reinforced epoxy laminate sheets, tubes, rods and printed circuit boards (PCB
). FR-4 is a composite material composed of woven fiberglass
cloth with an epoxy resin binder that is flame resistant (self-extinguishing).
FR-4 glass epoxy is a popular and versatile high-pressure thermoset plastic laminate grade with good strength to weight ratios. With near zero water absorption, FR-4 is most commonly used as an electrical insulator possessing considerable mechanical strength. The material is known to retain its high mechanical values and electrical insulating qualities in both dry and humid conditions. These attributes, along with good fabrication characteristics, lend utility to this grade for a wide variety of electrical and mechanical applications.
NEMA is the regulating authority for FR-4 and other insulating laminate grades. Grade designations for glass epoxy laminates are: G10, G11, FR4 and FR5. Of these, FR4 is the grade most widely in use today. G-10, the predecessor to FR-4, lacks FR-4's self-extinguishing flammability characteristics. Hence, FR-4 has since replaced G-10 in most applications.
FR-4 epoxy resin systems typically employ bromine
, a halogen, to facilitate flame-resistant properties in FR-4 glass epoxy laminates. Some applications where thermal destruction of the material is a desirable trait will still use G-10 non flame resistant.
s (PCBs) are produced. A thin layer of copper foil is laminated to one, or both sides of an FR-4 glass epoxy panel. These are commonly referred to as "copperclad laminates."
FR-4 copper-clad sheets are fabricated with circuitry etched into copper layers to produce printed circuit boards. More sophisticated and complex FR-4 printed circuit boards are produced in multiple layers, aka "multilayer circuitry".
s per square foot (oz/ft2). One ounce copper foil has a weight of one oz/ft2. This works out to a thickness of 34.1 µm (1.34 mils). Some PCB manufacturers refer to one ounce copper foil as having a thickness of 35 µm this may also be referred to as 35μ, 35 micron
, or 35 mic. Two ounce would be and half ounce would be or thereabouts.
1/0 - denotes 1 ounce copper one side / with no copper on the other side.
1/1 - denotes 1 ounce copper on both sides.
Similarly: H/0 or H/H - denotes half ounce copper on one and both sides, respectively. 2/0 or 2/2 - denotes 2 ounce copper on one and both sides respectively.
, arc
shields, transformer
s and screw terminal
strips.
Both FR-4 and G10 are used extensively in amateur high powered rocketry for constructing fins and avionics frameworks.
Printed circuit board
A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board or etched wiring...
). FR-4 is a composite material composed of woven fiberglass
Fiberglass
Glass fiber is a material consisting of numerous extremely fine fibers of glass.Glassmakers throughout history have experimented with glass fibers, but mass manufacture of glass fiber was only made possible with the invention of finer machine tooling...
cloth with an epoxy resin binder that is flame resistant (self-extinguishing).
FR-4 glass epoxy is a popular and versatile high-pressure thermoset plastic laminate grade with good strength to weight ratios. With near zero water absorption, FR-4 is most commonly used as an electrical insulator possessing considerable mechanical strength. The material is known to retain its high mechanical values and electrical insulating qualities in both dry and humid conditions. These attributes, along with good fabrication characteristics, lend utility to this grade for a wide variety of electrical and mechanical applications.
NEMA is the regulating authority for FR-4 and other insulating laminate grades. Grade designations for glass epoxy laminates are: G10, G11, FR4 and FR5. Of these, FR4 is the grade most widely in use today. G-10, the predecessor to FR-4, lacks FR-4's self-extinguishing flammability characteristics. Hence, FR-4 has since replaced G-10 in most applications.
FR-4 epoxy resin systems typically employ bromine
Bromine
Bromine ") is a chemical element with the symbol Br, an atomic number of 35, and an atomic mass of 79.904. It is in the halogen element group. The element was isolated independently by two chemists, Carl Jacob Löwig and Antoine Jerome Balard, in 1825–1826...
, a halogen, to facilitate flame-resistant properties in FR-4 glass epoxy laminates. Some applications where thermal destruction of the material is a desirable trait will still use G-10 non flame resistant.
Properties
Typical physical and electrical properties of FR-4 are as follows. LW (length wise, warp yarn direction) and CW (cross wise, fill yarn direction) refer to fiber orientations in the board that are perpendicular to one another.| Parameter | Value | Alternate units |
|---|---|---|
| Specific Gravity/Density Density The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight... |
1850 kg/m³ | |
| Water Absorption | -.125" < .10 % | |
| Temperature Index | 140 °C | 284 °F |
| Rockwell Hardness | 110 M scale | |
| Bond Strength | > 1000 kg | 2200 lbs |
| Flexural Strength-LW-A-.125" | > 448 MPa | 65,000 psi |
| Flexural Strength-CW-A-.125" | > 345 MPa | 50,000 psi |
| Tensile Strength (.125") LW | > 310 MPa | 45,000 psi |
| Izod Impact Strength-LW | > 54 Nm/m | |
| Izod Impact Strength-CW | > 44 Nm/m | 8 ft-lbs/in |
| Compressive Strength-Flatwise | > 415 MPa | 60,000 psi |
| Dielectric Breakdown-A | > 50 kV | |
| Dielectric Breakdown-D48/50 | > 50 kV | |
| Dielectric strength | 20 kV/mm | |
| Permittivity Permittivity In electromagnetism, absolute permittivity is the measure of the resistance that is encountered when forming an electric field in a medium. In other words, permittivity is a measure of how an electric field affects, and is affected by, a dielectric medium. The permittivity of a medium describes how... -A |
4.8 | |
| Permittivity-D24/23 | 4.8 | |
| Dissipation Factor Dissipation factor In physics, the dissipation factor is a measure of loss-rate of energy of a mode of oscillation in a dissipative system. It is the reciprocal of Quality factor, which represents the quality of oscillation.... -A |
0.017 | |
| Dissipation Factor-D24/23 | 0.018 | |
| Dielectric constant permittivity | 4.70 max, , | |
| Glass Transition Temperature | Can vary, but is over 120°C |
Printed circuit boards
FR-4 is the primary insulating backbone upon which the vast majority of rigid printed circuit boardPrinted circuit board
A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board or etched wiring...
s (PCBs) are produced. A thin layer of copper foil is laminated to one, or both sides of an FR-4 glass epoxy panel. These are commonly referred to as "copperclad laminates."
FR-4 copper-clad sheets are fabricated with circuitry etched into copper layers to produce printed circuit boards. More sophisticated and complex FR-4 printed circuit boards are produced in multiple layers, aka "multilayer circuitry".
Specifications
In the USA, copper foil thickness is specified in units of ounceOunce
The ounce is a unit of mass with several definitions, the most commonly used of which are equal to approximately 28 grams. The ounce is used in a number of different systems, including various systems of mass that form part of the imperial and United States customary systems...
s per square foot (oz/ft2). One ounce copper foil has a weight of one oz/ft2. This works out to a thickness of 34.1 µm (1.34 mils). Some PCB manufacturers refer to one ounce copper foil as having a thickness of 35 µm this may also be referred to as 35μ, 35 micron
Micron
Micron can refer to:*Micron, a non-SI name for micrometre*Micron , is the measurement used to express the diameter of a wool fibre.*A small curved diacritic mark above some letters, used to indicate shortness, e.g...
, or 35 mic. Two ounce would be and half ounce would be or thereabouts.
1/0 - denotes 1 ounce copper one side / with no copper on the other side.
1/1 - denotes 1 ounce copper on both sides.
Similarly: H/0 or H/H - denotes half ounce copper on one and both sides, respectively. 2/0 or 2/2 - denotes 2 ounce copper on one and both sides respectively.
Other applications
FR-4 is also used in the construction of relays, switches, standoffs, busbars, washersWasher (hardware)
A washer is a thin plate with a hole that is normally used to distribute the load of a threaded fastener, such as a screw or nut. Other uses are as a spacer, spring , wear pad, preload indicating device, locking device, and to reduce vibration...
, arc
Electric arc
An electric arc is an electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive media such as air. A synonym is arc discharge. An arc discharge is characterized by a lower voltage than a glow discharge, and relies on...
shields, transformer
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field...
s and screw terminal
Screw terminal
A screw terminal is a type of electrical connector where a wire is clamped down to metal by a screw.The wire is sometimes just stripped of electrical insulation at the end, and is bent in a U or J shape to fit around the shaft of the screw....
strips.
Both FR-4 and G10 are used extensively in amateur high powered rocketry for constructing fins and avionics frameworks.