PCB Board FR-4, 2 copper planes vs. Steel

Compare PCB Board FR-4, 2 copper planes vs. Steel strength, stiffness, weight and thermal properties.

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PCB Board FR-4, 2 copper planesComposite

Mechanical
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Yield strength	not given (tensile used)	385MPasourcetypical: mean of 20,295 A992 flange mill-test coupons (1998 SSPC survey), as reported by AISC
Ultimate tensile strength	246–385MPasourcethe bare laminate's (fr4-370hr), in-plane: cross direction .. length direction (ASTM D3039)	505MPasourcetypical: mean of 20,295 A992 flange mill-test coupons (1998 SSPC survey)
Elongation at break	not sourced	not sourced
Young's modulus (stiffness)	21.9–25.8GPasourcethe bare laminate's (fr4-370hr), in-plane: cross direction .. length direction (ASTM D790-15e2); the copper planes are left out	200GPasourcedesign value (AISC 360-16)
Density	not sourced	7,850kg/m³sourcenominal (constructional data)
Strength to weight	not sourced	49kN·m/kg
Stiffness to weight	not sourced	25.5MN·m/kg
Poisson's ratio	0.171–0.177sourcethe bare laminate's (fr4-370hr), in-plane: cross direction .. length direction	0.3sourcedesign value (AISC 360-16 Commentary)
Shear modulus	10.2GPa	76.9GPa7.57x stiffer in shear
Bulk modulus	12.2GPa	167GPa
Speed of sound	not sourced	5,048m/s
Thermal
Thermal conductivity	not sourced	48W/m·Ksourcenominal at 20 °C
Thermal expansion	13–14µm/m·Ksourcethe bare laminate's (fr4-370hr), in-plane X/Y-axis, below Tg (IPC-TM-650 2.4.24C)	12µm/m·Ksourcenominal (constructional data, no temperature range stated)
100 mm part over a 50 °C swing	67.5µm growth	60µm growth12% less
Specific heat	not sourced	460–480J/kg·Ksourcebase material: EN S275JR unalloyed structural steel (the EN counterpart of A36), typical, 50/100 °C
Heats up and cools (diffusivity)	not sourced	13mm²/s
Thermal shock resistance	not sourced	5,390W/m
Values for	A whole circuit board read as one orthotropic plate: the JEDEC high-K thermal test board (JESD51-7, "2s2p"), 0.062 in (1.575 mm) thick with two internal solid copper planes 0.0014 in (1 oz) thick, as Texas Instruments SZZA017A Table 1 gives it. Copper C110 and the Isola 370HR laminate from this library; the layers conduct in parallel along the board and in series through it (boardStackup.ts). Its two 0.0028 in trace layers cover little of the board and are left out; vias are ignored. Mechanical values are the bare laminate's.	Generic structural steel, cited as ASTM A992 (the current US structural grade): ASTM A992 W-shapes; Fy/Fu specified minimums from AISC publications (AISC 360-16 Commentary; Modern Steel Construction); elastic constants AISC 360; physical constants from the bauforumstahl structural-steel EPD, which names A992 among covered product standards.

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 PCB Board FR-4, 2 copper planes stronger than Steel?

Steel is stronger: its yield strength is 385 MPa against tensile strength 315 MPa for PCB Board FR-4, 2 copper planes (22%).

Which is stiffer, PCB Board FR-4, 2 copper planes or Steel?

Steel is stiffer: Young's modulus 200 GPa against 23.9 GPa for PCB Board FR-4, 2 copper planes, so the same part in Steel deflects less under the same load.

Which expands less with temperature?

Steel expands less: 12 µm/m·K against 13.5 µm/m·K for PCB Board FR-4, 2 copper planes.

Among 73 materials

Stiffness against density

Strength against density