Aluminum vs. PCB Laminate FR-4

Compare Aluminum vs. PCB Laminate FR-4 strength, stiffness, weight and thermal properties.

Mechanical	Aluminum	PCB Laminate FR-4
Yield strength	276MPa1	not given (tensile used)
Ultimate tensile strength	310MPa1	246–385MPa2
Flexural strength	not sourced	531–621MPa2
Elongation at break	17%1	not sourced
Young's modulus (stiffness)	68.3GPa1	21.9–25.8GPa2
Density	2,700kg/m³1	1,920kg/m³341% lighter
Strength to weight	102kN·m/kg	164kN·m/kg1.61x higher
Stiffness to weight	25.3MN·m/kg2.04x higher	12.4MN·m/kg
Poisson's ratio	0.334	0.171–0.1772
Shear modulus	25.7GPa2.53x stiffer in shear	10.2GPa
Bulk modulus	67GPa5.49x higher	12.2GPa
Speed of sound	5,030m/s43% faster	3,525m/s

Stiffness against densityHigher and further left: stiffer for its weight

Strength against densityHigher and further left: stronger for its weight

Thermal	Aluminum	PCB Laminate FR-4
Thermal conductivity	167W/m·K1418x more heat through a fin	0.4W/m·K2
Thermal expansion	23.6µm/m·K1	13–14µm/m·K2
100 mm part over a 50 °C swing	118µm growth	67.5µm growth1.75x less
Specific heat	896J/kg·K1	1,200–1,400J/kg·K3
Heats up and cools (diffusivity)	69mm²/s431x faster	0.16mm²/s
Thermal shock resistance	19,159W/m59.2x more resistant	324W/m
Melting point	solidus-liquidus582–652°C1	not sourced
Glass transition	not sourced	180°C2
Max service temperature	not sourced	130°C2

Thermal conductivity against densityHigher and further left: spreads more heat for its weight

Thermal expansion against thermal conductivityLower and further right: warps less when heated

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Sources4 documents: Kaiser Aluminum, Isola, Park Electrochemical (Nelco), U.S. Department of Defense

Aluminum: 6061-T6/T651, Kaiser Aluminum typical properties (sheet, coil & plate datasheet); 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 6061 Sheet, Coil & Plate Technical DataKaiser Aluminumarchived copyAluminum · Yield strength: typical, 0.2% offset, .500 in dia specimenAluminum · Ultimate tensile strength: typicalAluminum · Elongation at break: typical, in 4D, 0.500 in dia specimenAluminum · Young's modulus (stiffness): typicalAluminum · Density: nominalAluminum · Thermal conductivity: typical, 20 °CAluminum · Thermal expansion: typical, mean 20-100 °CAluminum · Specific heat: typical, at 100 °CAluminum · Melting point: solidus-liquidus
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
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
4
MIL-HDBK-5J, Metallic Materials and Elements for Aerospace Vehicle Structures (2003)U.S. Department of DefenseAluminum · 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 stronger than PCB Laminate FR-4?

PCB Laminate FR-4 is stronger: its tensile strength is 315 MPa against yield strength 276 MPa for Aluminum (14%).

Which is lighter, Aluminum or PCB Laminate FR-4?

PCB Laminate FR-4 is lighter: 1,920 kg/m³ against 2,700 kg/m³ for Aluminum.

Which is stiffer, Aluminum or PCB Laminate FR-4?

Aluminum is stiffer: Young's modulus 68.3 GPa against 23.9 GPa for PCB Laminate FR-4, so the same part in Aluminum deflects less under the same load.

Which is lighter for the same job, Aluminum or PCB Laminate FR-4?

For the same stiffness or strength: Aluminum is lighter for a stiff rod or tie (tension), stiff beam (bending); PCB Laminate FR-4 is lighter for a strong rod or tie, strong beam, strong panel or plate.

Part that must be	Aluminum	PCB Laminate FR-4
Stiff rod or tie (tension)	lighter	2.04x heavier
Stiff beam (bending)	lighter	20% heavier
Stiff panel or plate	about equal	about equal
Strong rod or tie	1.61x heavier	lighter
Strong beam	1.54x heavier	lighter
Strong panel or plate	1.5x 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 or PCB Laminate FR-4?

Aluminum conducts heat better: 167 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 23.6 µm/m·K for Aluminum.