Thermal conductivity against densityHigher and further left: spreads more heat for its weightThermal expansion against thermal conductivityLower and further right: warps less when heated
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Sources5 documents: Kaiser Aluminum, Isola, Park Electrochemical (Nelco), U.S. Department of Defense
Aluminum 7075-T6
7075-T6/T651, Kaiser Aluminum rod & bar (mechanical) and sheet/coil/plate (physical) typical datasheets; Poisson from MIL-HDBK-5J
PCB Laminate FR-4
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.
1
Alloy 7075 Rod & Bar Technical DataKaiser Aluminumarchived copyAluminum 7075-T6 · Yield strength: typical, 0.2% offset, .500 in dia specimenAluminum 7075-T6 · Ultimate tensile strength: typicalAluminum 7075-T6 · Elongation at break: typical, in 4DAluminum 7075-T6 · Young's modulus (stiffness): typical
2
370HR Laminate and Prepreg Data SheetIsolaarchived copyPCB Laminate FR-4 · Ultimate tensile strength: typical, in-plane: cross direction .. length direction (ASTM D3039)PCB Laminate FR-4 · Flexural strength: typical: cross direction .. length direction (IPC-TM-650 2.4.4B)PCB Laminate FR-4 · Young's modulus (stiffness): typical, in-plane: cross direction .. length direction (ASTM D790-15e2)PCB Laminate FR-4 · Poisson's ratio: typical, in-plane: cross direction .. length directionPCB Laminate FR-4 · Thermal conductivity: typical (ASTM E1952); direction not stated by the sheetPCB Laminate FR-4 · Thermal expansion: typical, in-plane X/Y-axis, below Tg (IPC-TM-650 2.4.24C)PCB Laminate FR-4 · Glass transition: typical, DSC (IPC-TM-650 2.4.25C)PCB Laminate FR-4 · Max service temperature: UL Relative Thermal Index (UL 796)
3
Alloy 7075 Sheet, Coil & Plate Technical DataKaiser Aluminumarchived copyAluminum 7075-T6 · Density: nominalAluminum 7075-T6 · Thermal conductivity: typical, 20 °C, T651Aluminum 7075-T6 · Thermal expansion: typical, mean 20-100 °CAluminum 7075-T6 · Specific heat: typical, at 100 °CAluminum 7075-T6 · Melting point: melting range
4
N4000-6 Laminate Data Sheet (2006)Park Electrochemical (Nelco)archived copyPCB Laminate FR-4 · Density: typical, 50% resin content; another FR-4 producer: Park Nelco N4000-6 (high-Tg multifunctional epoxy), not Isola 370HRPCB Laminate FR-4 · Specific heat: typical (ASTM E1461); another FR-4 producer: Park Nelco N4000-6 (high-Tg multifunctional epoxy), not Isola 370HR
5
MIL-HDBK-5J, Metallic Materials and Elements for Aerospace Vehicle Structures (2003)U.S. Department of DefenseAluminum 7075-T6 · Poisson's ratio: typical (handbook physical constant)
Each number points to the document that states it, with the exact basis. Values without a number are computed from the sourced ones. "Not sourced" means no citable source states it (or only a specification minimum); figures computed from it are left out too.
Questions
Mechanical
Is Aluminum 7075-T6 stronger than PCB Laminate FR-4?
Aluminum 7075-T6 is stronger: its yield strength is 503 MPa against tensile strength 315 MPa for PCB Laminate FR-4 (1.59x).
Which is lighter, Aluminum 7075-T6 or PCB Laminate FR-4?
PCB Laminate FR-4 is lighter: 1,920 kg/m³ against 2,800 kg/m³ for Aluminum 7075-T6.
Which is stiffer, Aluminum 7075-T6 or PCB Laminate FR-4?
Aluminum 7075-T6 is stiffer: Young's modulus 71 GPa against 23.9 GPa for PCB Laminate FR-4, so the same part in Aluminum 7075-T6 deflects less under the same load.
Which is lighter for the same job, Aluminum 7075-T6 or PCB Laminate FR-4?
For the same stiffness or strength: Aluminum 7075-T6 is lighter for a stiff rod or tie (tension), stiff beam (bending), strong rod or tie; PCB Laminate FR-4 is lighter for a stiff panel or plate, strong beam, strong panel or plate.
Part that must be
Aluminum 7075-T6
PCB Laminate FR-4
Stiff rod or tie (tension)
lighter
2.04x heavier
Stiff beam (bending)
lighter
18% heavier
Stiff panel or plate
1% heavier
lighter
Strong rod or tie
lighter
9% heavier
Strong beam
7% heavier
lighter
Strong panel or plate
15% 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).
Thermal
Which conducts heat better, Aluminum 7075-T6 or PCB Laminate FR-4?
Aluminum 7075-T6 conducts heat better: 130 W/m·K against 0.4 W/m·K for PCB Laminate FR-4.
Which expands less with temperature?
PCB Laminate FR-4 expands less: 13.5 µm/m·K against 23.4 µm/m·K for Aluminum 7075-T6.