Materials / Compare
Glass vs. PCB Laminate FR-4
Compare Glass vs. PCB Laminate FR-4 strength, stiffness, weight and thermal properties.
| Try it on a partA panel to run stress or thermal on, free in your browser | Open in LessCAD | Open in LessCAD |
|---|---|---|
| Mechanical | ||
| Yield strength | not given (tensile used) | not given (tensile used) |
| Ultimate tensile strength | 41MPasourcetypical mean surface tensile stress at fracture (MOR), 60 s load, weathered, 50% breakage probability | 246–385MPasourcetypical, in-plane: cross direction .. length direction (ASTM D3039) |
| Flexural strength | 41MPasourcemean MOR (same value as tensile) | 531–621MPasourcetypical: cross direction .. length direction (IPC-TM-650 2.4.4B) |
| Elongation at break | not sourced | not sourced |
| Young's modulus (stiffness) | 72GPasourcetypical | 21.9–25.8GPasourcetypical, in-plane: cross direction .. length direction (ASTM D790-15e2) |
| Density | 2,500kg/m³sourcetypical | 1,920kg/m³sourcetypical, 50% resin content; another FR-4 producer: Park Nelco N4000-6 (high-Tg multifunctional epoxy), not Isola 370HR |
| Strength to weight | 16.4kN·m/kg | 164kN·m/kg10x higher |
| Stiffness to weight | 28.8MN·m/kg2.32x higher | 12.4MN·m/kg |
| Poisson's ratio | 0.22sourcetypical | 0.171–0.177sourcetypical, in-plane: cross direction .. length direction |
| Shear modulus | 29.5GPa2.9x stiffer in shear | 10.2GPa |
| Bulk modulus | 42.9GPa | 12.2GPa |
| Speed of sound | 5,367m/s | 3,525m/s |
| Thermal | ||
| Thermal conductivity | 0.937W/m·Ksourcetypical at 75 F | 0.4W/m·Ksourcetypical (ASTM E1952); direction not stated by the sheet |
| Thermal expansion | 8.3µm/m·Ksourcetypical, 75-575 F | 13–14µm/m·Ksourcetypical, in-plane X/Y-axis, below Tg (IPC-TM-650 2.4.24C) |
| 100 mm part over a 50 °C swing | 41.5µm growth1.63x less | 67.5µm growth |
| Specific heat | 880J/kg·Ksourcetypical at 75 F | 1,200–1,400J/kg·Ksourcetypical (ASTM E1461); another FR-4 producer: Park Nelco N4000-6 (high-Tg multifunctional epoxy), not Isola 370HR |
| Heats up and cools (diffusivity) | 0.426mm²/s2.66x faster | 0.16mm²/s |
| Thermal shock resistance | 50.1W/m | 324W/m6.45x more resistant |
| Glass transition | not sourced | 180°Csourcetypical, DSC (IPC-TM-650 2.4.25C) |
| Max service temperature | 511°Csourcestrain point (ASTM C336) - stress-relaxation onset, not a rated service limit | 130°CsourceUL Relative Thermal Index (UL 796) |
| Values for | Annealed soda-lime-silica float glass, Pilkington North America Technical Bulletin ATS-129 (04/2025) | Isola 370HR FR-4 laminate (Polyclad PCL-FR-370HR, 180 C Tg multifunctional epoxy, E-glass fabric), copper removed; Isola data sheet Revision C, last updated April 15, 2021. Woven-glass laminate: the sheet gives in-plane values per weave direction (length / cross) and the Z-axis CTE separately; the solver is isotropic per material. |
Every value links to the document that states it. "Not sourced" means no citable source states it (or only a specification minimum); figures computed from it are left out too.
Questions
Is Glass stronger than PCB Laminate FR-4?
PCB Laminate FR-4 is stronger: its tensile strength is 315 MPa against 41 MPa for Glass (7.69x).
Which is lighter, Glass or PCB Laminate FR-4?
PCB Laminate FR-4 is lighter: 1,920 kg/m³ against 2,500 kg/m³ for Glass.
Which is stiffer, Glass or PCB Laminate FR-4?
Glass is stiffer: Young's modulus 72 GPa against 23.9 GPa for PCB Laminate FR-4, so the same part in Glass deflects less under the same load.
Which is lighter for the same job, Glass or PCB Laminate FR-4?
For the same stiffness or strength: Glass is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate; PCB Laminate FR-4 is lighter for a strong rod or tie, strong beam, strong panel or plate.
| Part that must be | Glass | PCB Laminate FR-4 |
|---|---|---|
| Stiff rod or tie (tension) | lighter | 2.32x heavier |
| Stiff beam (bending) | lighter | 33% heavier |
| Stiff panel or plate | lighter | 11% heavier |
| Strong rod or tie | 10x heavier | lighter |
| Strong beam | 5.07x heavier | lighter |
| Strong panel or plate | 3.61x heavier | lighter |
For the same stiffness or strength, mass scales with density over stiffness (or strength) raised to a power set by how the part is loaded: 1 for a rod in tension, 1/2 for a beam in bending, 1/3 for a panel (the standard material-selection indices).
Which conducts heat better, Glass or PCB Laminate FR-4?
Glass conducts heat better: 0.937 W/m·K against 0.4 W/m·K for PCB Laminate FR-4.
Which expands less with temperature?
Glass expands less: 8.3 µm/m·K against 13.5 µm/m·K for PCB Laminate FR-4.