FR-4 · grade
FR-4 High-Tg
Properties of the High-Tg condition, compared with the other FR-4 grades.
Pick for lead-free reflow, multilayer/HDI boards or parts running above 130 °C where Z-axis expansion and via reliability matter.
What is FR-4 High-Tg?
FR-4 High-Tg is FR-4 in the High-Tg grade — pick for lead-free reflow, multilayer/HDI boards or parts running above 130 °C where Z-axis expansion and via reliability matter. FR-4 High-Tg has a tensile strength of 310 MPa (45 ksi), stronger than 53% of composite grades. Elongation at break is 1.8% and the elastic modulus is 22 GPa (3.19 Msi). FR-4 High-Tg has a density of 1.85 g/cm³ (0.0668 lb/in³), heavier than 65% of composite grades. Its glass-transition temperature is 175°C (347 °F). Epoxy Matrix is the default condition FabDigit quotes; High-Tg is available on request or by drawing note.
Advantages
- Low moisture uptake — 0.08%, better than 90% of composite grades
FR-4 High-Tg properties
Typical room-temperature values for FR-4 High-Tg — 9 properties are specific to this condition; the rest are grade-level values shared by every FR-4 grade. Each bar shows where the value sits among the composite grades in FabDigit's library — further right is higher.
Physical4
FR-4 High-Tg has a density of 1.85 g/cm³ (0.0668 lb/in³), heavier than 65% of composite grades. Its glass-transition temperature is 175°C (347 °F).
Mechanical12
FR-4 High-Tg has a tensile strength of 310 MPa (45 ksi), stronger than 53% of composite grades. Elongation at break is 1.8% and the elastic modulus is 22 GPa (3.19 Msi).
Thermal8
FR-4 High-Tg is rated for continuous service to 150°C (302 °F). It conducts heat at 0.3 W/m·K (0.173 BTU/hr·ft·°F), worse than 62% of composite grades. Thermal expansion is 13 µm/m·K (7.22 µin/in·°F).
Electrical7
FR-4 High-Tg 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 excellent (85/100), better than 65% of composite grades. UV resistance is fair.
Sustainability4
Producing a kilogram of FR-4 High-Tg takes about 95 MJ of energy and emits 6 kg of CO₂ — less than 72% of composite grades. Typical recycled content is 0%.
Manufacturability2
FR-4 High-Tg's machinability is fair (45/100, better than 64% of composite grades).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other FR-4 grades and fills
FR-4 is also supplied in 20 other conditions. The full side-by-side table is on the FR-4 overview.
- Epoxy MatrixDefaultDefault choice for general PCB substrates, insulating plates, spacers and fixtures below ~130 °C.310 MPa tensile
- NEMA-G11High-temperature epoxy / woven E-glass laminate (non flame-retardant, UL 94 HB) retaining ≥50 % of flexural strength at 150 °C.340 MPa tensile
- G10Choose when flame rating is irrelevant but the best mechanical/electrical properties and lowest cost are wanted (knife scales, jigs, insulators).330 MPa tensile
- NEMA-FR5Heat-resistant multifunctional epoxy / woven E-glass laminate, flame-retardant (UL 94 V-0), retains strength to ~155 °C.320 MPa tensile
- NEMA-G9Electrical-grade melamine / woven glass laminate — G-5 mechanicals with better dielectric performance under humidity and high arc resistance.215 MPa tensile
- NEMA-G5Melamine-resin / woven glass laminate — very hard, high arc- and track-resistance, self-extinguishing; used for arc barriers and switchgear.205 MPa tensile
- NEMA-G3Phenolic-resin / woven glass laminate — tough and impact resistant with fair electricals; largely superseded by G-10/FR-4.170 MPa tensile
- NEMA-G7Silicone-resin / woven glass laminate — Class H thermal endurance (~220 °C), excellent arc resistance and low dielectric loss, modest strength.145 MPa tensile
- NEMA-XPaper-reinforced phenolic laminate, mechanical grade — highest strength of the paper grades, electrical properties not guaranteed.125 MPa tensile
- NEMA-XXPaper/phenolic laminate of mechanical-and-electrical quality — better moisture resistance and dielectric behaviour than Grade X.110 MPa tensile
- NEMA-XXXPaper/phenolic electrical-grade laminate with minimum cold flow and low loss under humidity — classic radio/terminal-board material.100 MPa tensile
- NEMA-LFine-weave linen/cotton fabric phenolic laminate — smoother finish and finer machined detail than Grade C, mechanical grade.85 MPa tensile
- NEMA-LEFine-weave fabric phenolic laminate of electrical quality — best machining/finish of the cotton grades with usable dielectric strength.85 MPa tensile
- GPO-1Glass-mat reinforced polyester sheet, general-purpose mechanical/electrical grade, non flame-retardant (UL 94 HB).80 MPa tensile
- GPO-3Flame-retardant glass-mat polyester sheet with high arc and tracking resistance (CTI ≥ 600 V); standard switchgear insulation board.75 MPa tensile
- NEMA-CCoarse-weave cotton fabric / phenolic laminate — mechanical grade with high impact strength and good machinability; poor electricals.70 MPa tensile
- NEMA-CECoarse cotton fabric / phenolic laminate with improved moisture and electrical performance over Grade C.70 MPa tensile
- High-TgPick for lead-free reflow, multilayer/HDI boards or parts running above 130 °C where Z-axis expansion and via reliability matter.9 properties
Working with FR-4 High-Tg
Is FR-4 easy to machine?
Machine dry with carbide or diamond-coated tools at high speed/low feed; glass is highly abrasive, so expect rapid tool wear, and capture the dust (respirable glass/epoxy) with local extraction.
Can FR-4 be welded?
Not weldable — a thermoset; join by adhesive bonding (epoxy), riveting or threaded inserts.
Can FR-4 be formed, bent or molded?
Supplied only as pressed flat sheet/rod/tube; no post-forming — parts are machined, routed, drilled or laser/water-jet cut, and layer count is set during lamination.
What surface finishes work on FR-4?
Deburr edges to avoid delamination and glass splinters; can be silkscreened, epoxy-painted, copper-etched and plated (through-hole Cu/Ni/Au), but never anodized or polished to a mirror finish.
FR-4 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 fabric (7628/2116/1080 styreinforcement, wt % | 50 – 65 | 58 |
| brominated flame retardant (TBBPA-derivewt % of the resin phase; absent in halogen-free grades | 12 – 20 | 17 |
| inorganic filler (silica / ATH)grade dependent | 0 – 10 | 3 |
| epoxy resin (DGEBA / multifunctional, cumatrix incl. hardener (dicy or phenolic) | ≥ 30 (balance) | — |
FR-4 High-Tg — frequently asked
What is FR-4 High-Tg used for?
FR-4 High-Tg is typically used for printed circuit board substrate, electrical insulators, standoffs and barriers, terminal boards and switchgear panels, transformer and busbar spacers, motor and battery pack insulation plates and test fixture and bed-of-nails plates. In short: bullet-proof glass alternative.
What is the tensile strength of FR-4 High-Tg?
FR-4 High-Tg has a typical tensile strength of 310 MPa (45 ksi) — stronger than 53% of composite grades. Strength varies by condition: see the 21 listed tempers.
Is FR-4 High-Tg easy to machine?
Reasonably — machinability is rated fair (45/100, better than 64% of composite grades). Machine dry with carbide or diamond-coated tools at high speed/low feed; glass is highly abrasive, so expect rapid tool wear, and capture the dust (respirable glass/epoxy) with local extraction.
Can FR-4 High-Tg be welded?
Not weldable — a thermoset; join by adhesive bonding (epoxy), riveting or threaded inserts.
What surface finishes work on FR-4 High-Tg?
Deburr edges to avoid delamination and glass splinters; can be silkscreened, epoxy-painted, copper-etched and plated (through-hole Cu/Ni/Au), but never anodized or polished to a mirror finish.
Can FR-4 High-Tg be formed, bent or molded?
Supplied only as pressed flat sheet/rod/tube; no post-forming — parts are machined, routed, drilled or laser/water-jet cut, and layer count is set during lamination.
What is the maximum service temperature of FR-4 High-Tg?
FR-4 High-Tg is rated for continuous use to about 150°C (302 °F), and briefly to 260°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in FR-4 High-Tg?
Yes — FR-4 High-Tg is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- IPC-4101 Specification for Base Materials for Rigid and Multilayer Printed Boards — IPC (2021)
- NEMA LI-1 Industrial Laminating Thermosetting Products — NEMA (1998)
- Isola / Shengyi / ITEQ FR-4 laminate datasheets (S1141, S1000-2, IT-180A) — Isola, , ITEQ (2023)
- Garolite FR-4 / G-10 sheet property tables — McMaster-Carr / Röchling (2024)
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.