FR-5 HTG (High-Tg FR-5)
Grade
ASTM D709 Grade FR-5
Choose for lead-free reflow, continuous 180 °C service or low-CTE requirements in multilayer builds.
Values for the HTG condition
What is FR-5 HTG?
FR-5 HTG is FR-5 in the HTG grade — choose for lead-free reflow, continuous 180 °C service or low-CTE requirements in multilayer builds. FR-5 HTG has a tensile strength of 340 MPa (49.3 ksi), stronger than 61% of composite grades. The elastic modulus is 22 GPa (3.19 Msi). FR-5 HTG has a density of 1.85 g/cm³ (0.0668 lb/in³), heavier than 67% of composite grades. Its glass-transition temperature is 185°C (365 °F).
Limitations
- Hard to polish — 25/100, worse than 76% of composite grades
FR-5 HTG properties
Typical room-temperature values for FR-5 HTG; 6 are specific to this condition. Other listed values are FR-5 reference data and may not represent this condition. Bars are the position among composite grades.
Physical4
FR-5 HTG has a density of 1.85 g/cm³ (0.0668 lb/in³), heavier than 67% of composite grades. Its glass-transition temperature is 185°C (365 °F).
Mechanical11
FR-5 HTG has a tensile strength of 340 MPa (49.3 ksi), stronger than 61% of composite grades. The elastic modulus is 22 GPa (3.19 Msi).
Thermal8
FR-5 HTG is rated for continuous service to 180°C (356 °F). It conducts heat at 0.3 W/m·K (0.173 BTU/hr·ft·°F), worse than 63% of composite grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical7
FR-5 HTG is an electrical insulator with a dielectric strength of 20 kV/mm (508 V/mil) and a resistivity of 1×10¹² Ω·m.
Chemical & Environmental3
Corrosion resistance is very good (80/100), better than 54% of composite grades. UV resistance is fair.
Sustainability4
Producing a kilogram of FR-5 HTG takes about 110 MJ of energy and emits 6.5 kg of CO₂ — less than 60% of composite grades. Typical recycled content is 0%.
Manufacturability2
FR-5 HTG's machinability is fair (42/100, better than 58% of composite grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with FR-5 HTG
Is FR-5 easy to machine?
Machines like G-11/FR-4 but abrasive: use carbide or PCD tooling, high speed/low feed, vacuum dust extraction and support to avoid delamination and edge chipping.
Can FR-5 be welded?
Thermoset — cannot be welded; join by bonding with epoxy adhesives or mechanical fastening with washers to spread load.
Can FR-5 be formed, bent or molded?
Supplied as fully cured pressed sheet/rolled tube; no post-forming possible — cut, drill, rout or waterjet to shape.
What surface finishes work on FR-5?
Edges deburred/sealed with epoxy varnish for tracking resistance; paint or conformal coat for UV exposure; no plating except on copper-clad grades.
FR-5 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| E-glass woven fabric7628/2116 style cloth, silane finished | 50 – 65 | 58 |
| bromine (as flame retardant)wt % of resin fraction; gives UL 94 V-0 | 12 – 20 | 16 |
| inorganic filler / curing agentssilica or ATH in filled high-Tg versions | 0 – 8 | 3 |
| brominated epoxy resin (TBBPA-based)dicy or phenolic-novolac cured, high-Tg system | ≥ 30 (balance) |
FR-5 HTG — frequently asked
What is FR-5 HTG used for?
FR-5 HTG is typically used for high-performance PCB substrates, structural insulation under elevated temperature and aerospace electrical components. In short: higher-temperature FR-4 upgrade; flame-retardant G-11 equivalent; 340 MPa epoxy-glass laminate.
What is the tensile strength of FR-5 HTG?
FR-5 HTG has a typical tensile strength of 340 MPa (49.3 ksi) — stronger than 61% of composite grades.
Is FR-5 HTG easy to machine?
Not especially — machinability is rated fair (42/100, better than 58% of composite grades). Machines like G-11/FR-4 but abrasive: use carbide or PCD tooling, high speed/low feed, vacuum dust extraction and support to avoid delamination and edge chipping.
Can FR-5 HTG be welded?
Thermoset — cannot be welded; join by bonding with epoxy adhesives or mechanical fastening with washers to spread load.
What surface finishes work on FR-5 HTG?
Edges deburred/sealed with epoxy varnish for tracking resistance; paint or conformal coat for UV exposure; no plating except on copper-clad grades.
Can FR-5 HTG be formed, bent or molded?
Supplied as fully cured pressed sheet/rolled tube; no post-forming possible — cut, drill, rout or waterjet to shape.
What is the maximum service temperature of FR-5 HTG?
FR-5 HTG is rated for continuous use to about 180°C (356 °F), and briefly to 200°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- ASTM D709 Standard Specification for Laminated Thermosetting Materials — ASTM International (2017)
- NEMA LI 1 Industrial Laminating Thermosetting Products — NEMA (1998)
- IPC-4101 Specification for Base Materials for Rigid and Multilayer Printed Boards — IPC (2021)
- Engineered Materials Handbook Vol.1: Composites — ASM International (1987)
- Epoxy glass laminate (G-10/FR-4/G-11/FR-5) property sheets — insulation laminate producers (2023)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.