PCB Laminate FR-4 vs. Plastic PBT GF30

Compare PCB Laminate FR-4 vs. Plastic PBT GF30 strength, stiffness, weight and thermal properties.

Plastic PBT GF30Bulk polymer (molded or machined)

Mechanical	PCB Laminate FR-4	Plastic PBT GF30
Yield strength	not given (tensile used)	not given (tensile used)
Ultimate tensile strength	246–385MPa1	stress at break140MPa2
Flexural strength	531–621MPa1	210MPa2
Elongation at break	not sourced	strain at break3%2
Young's modulus (stiffness)	21.9–25.8GPa1	9.8GPa2
Density	1,920kg/m³3	1,530kg/m³225% lighter
Strength to weight	164kN·m/kg1.8x higher	91.5kN·m/kg
Stiffness to weight	12.4MN·m/kg1.94x higher	6.41MN·m/kg
Poisson's ratio	0.171–0.1771	not sourced
Shear modulus	10.2GPa	not sourced
Bulk modulus	12.2GPa	not sourced
Speed of sound	3,525m/s39% faster	2,531m/s

Stiffness against densityHigher and further left: stiffer for its weight

Strength against densityHigher and further left: stronger for its weight

Thermal	PCB Laminate FR-4	Plastic PBT GF30
Thermal conductivity	0.4W/m·K148% more heat through a fin	0.27W/m·K2
Thermal expansion	13–14µm/m·K1	longitudinal25µm/m·K2
100 mm part over a 50 °C swing	67.5µm growth1.85x less	125µm growth
Specific heat	1,200–1,400J/kg·K3	1,050J/kg·K2
Heats up and cools (diffusivity)	0.16mm²/s	0.168mm²/s5% faster
Thermal shock resistance	324W/m	not sourced
Melting point	not sourced	DSC223°C2
Glass transition	180°C1	not sourced
Max service temperature	130°C1	HDT 1.8 MPa205°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

Try it on a partA sample part to run stress or thermal on, free in your browser	Open in LessCAD	Open in LessCAD

Sources3 documents: Isola, BASF, Park Electrochemical (Nelco)

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.
Plastic PBT GF30: BASF Ultradur B 4300 G6 (PBT, 30% glass fibre), injection moulding grade; product information sheet 09/2026, typical values for uncoloured product at 23 °C.

1
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)
2
Ultradur B 4300 G6 Product InformationBASFPlastic PBT GF30 · Ultimate tensile strength: stress at break, 23 °CPlastic PBT GF30 · Flexural strength: typical, 23 °CPlastic PBT GF30 · Elongation at break: strain at break, 23 °CPlastic PBT GF30 · Young's modulus (stiffness): typical, 23 °CPlastic PBT GF30 · Density: typicalPlastic PBT GF30 · Thermal conductivity: typical (DIN 52612-1)Plastic PBT GF30 · Thermal expansion: longitudinal (flow), mean 23-55 °CPlastic PBT GF30 · Specific heat: typical, 23 °CPlastic PBT GF30 · Melting point: DSC (ISO 11357)Plastic PBT GF30 · Max service temperature: HDT 1.8 MPa
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

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 PCB Laminate FR-4 stronger than Plastic PBT GF30?

PCB Laminate FR-4 is stronger: its tensile strength is 315 MPa against 140 MPa for Plastic PBT GF30 (2.25x).

Which is lighter, PCB Laminate FR-4 or Plastic PBT GF30?

Plastic PBT GF30 is lighter: 1,530 kg/m³ against 1,920 kg/m³ for PCB Laminate FR-4.

Which is stiffer, PCB Laminate FR-4 or Plastic PBT GF30?

PCB Laminate FR-4 is stiffer: Young's modulus 23.9 GPa against 9.8 GPa for Plastic PBT GF30, so the same part in PCB Laminate FR-4 deflects less under the same load.

Which is lighter for the same job, PCB Laminate FR-4 or Plastic PBT GF30?

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

Part that must be	PCB Laminate FR-4	Plastic PBT GF30
Stiff rod or tie (tension)	lighter	1.94x heavier
Stiff beam (bending)	lighter	24% heavier
Stiff panel or plate	lighter	7% heavier
Strong rod or tie	lighter	1.8x heavier
Strong beam	lighter	37% heavier
Strong panel or plate	lighter	20% heavier

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, PCB Laminate FR-4 or Plastic PBT GF30?

PCB Laminate FR-4 conducts heat better: 0.4 W/m·K against 0.27 W/m·K for Plastic PBT GF30.

Which expands less with temperature?

PCB Laminate FR-4 expands less: 13.5 µm/m·K against 25 µm/m·K for Plastic PBT GF30.