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 | 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-A | 4.8 | |
| Permittivity-D24/23 | 4.8 | |
| Dissipation Factor-A | 0.017 | |
| Dissipation Factor-D24/23 | 0.018 | |
| Dielectric constant permittivity | 4.70 max, 4.35 @ 500 MHz, 4.34 @ 1 GHz | |
| Glass Transition Temperature | Can vary, but is over 120°C | |
| Young's Modulus - LW | 3.5x10^6 psi | |
| Young's Modulus - CW | 3.0x10^6 psi | |
| CTE x-axis | 14ppm/°C | |
| CTE y-axis | 13ppm/°C | |
| CTE z-axis | 175ppm/°C | |
| Poisson's Ratio - LW | 0.136 | |
| Poisson's Ratio - CW | 0.118 |
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