CEM-3 HTG (High-Tg)
Grade
Choose the Tg ≈150 °C epoxy system for lead-free reflow at 260 °C or higher operating temperature, where z-axis expansion must be kept under control.
Values for the HTG condition
Other CEM-3 grades and fills
CEM-3 is listed in 3 conditions; see the grade overview at CEM-3.
Compare all 3 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Halogen-free | Pick the phosphorus/ATH flame-retarded halogen-free version when EU export or customer specifications cap bromine and chlorine at 900 ppm each. | — | 155 | 1.4 | 106 HRM |
High-CTI | Pick for AC mains boards and appliance control boards where CTI ≥ 600 V allows reduced creepage distance under IEC 60664 material group I; glass transition stays at 130 °C. | — | 155 | 1.5 | 104 HRM |
HTGThis page High-Tg | Choose the Tg ≈150 °C epoxy system for lead-free reflow at 260 °C or higher operating temperature, where z-axis expansion must be kept under control. | — | 165 | 1.4 | 107 HRM |
What is CEM-3 HTG?
CEM-3 HTG is CEM-3 in the HTG grade — choose the Tg ≈150 °C epoxy system for lead-free reflow at 260 °C or higher operating temperature, where z-axis expansion must be kept under control. CEM-3 HTG has a tensile strength of 165 MPa (23.9 ksi), weaker than 55% of composite grades. Elongation at break is 1.4% and the elastic modulus is 15.5 GPa (2.25 Msi). CEM-3 HTG has a density of 1.85 g/cm³ (0.0668 lb/in³), heavier than 67% of composite grades. Its glass-transition temperature is 150°C (302 °F).
Advantages
- Easy to machine — 62/100, better than 75% of composite grades
Limitations
- Hard to polish — 25/100, worse than 76% of composite grades
CEM-3 HTG properties
Typical room-temperature values for CEM-3 HTG; 21 are specific to this condition. Other listed values are CEM-3 reference data and may not represent this condition. Bars are the position among composite grades.
Physical4
CEM-3 HTG has a density of 1.85 g/cm³ (0.0668 lb/in³), heavier than 67% of composite grades. Its glass-transition temperature is 150°C (302 °F).
Mechanical11
CEM-3 HTG has a tensile strength of 165 MPa (23.9 ksi), weaker than 55% of composite grades. Elongation at break is 1.4% and the elastic modulus is 15.5 GPa (2.25 Msi).
Thermal8
CEM-3 HTG is rated for continuous service to 140°C (284 °F). It conducts heat at 0.35 W/m·K (0.202 BTU/hr·ft·°F), better than 50% of composite grades. Thermal expansion is 14 µm/m·K (7.78 µin/in·°F).
Electrical7
CEM-3 HTG is an electrical insulator with a dielectric strength of 32 kV/mm (812.8 V/mil) and a resistivity of 1×10¹² Ω·m.
Chemical & Environmental3
Corrosion resistance is excellent (86/100), better than 72% of composite grades. UV resistance is fair.
Sustainability4
Producing a kilogram of CEM-3 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
CEM-3 HTG's machinability is good (62/100, better than 75% of composite grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with CEM-3 HTG
Is CEM-3 easy to machine?
Can be punched after preheating to 40–60 °C and drilled at high speed with lower drill wear than FR-4. Use carbide tooling with vacuum extraction to control glass dust and prevent delamination.
Can CEM-3 be welded?
Thermoset laminate — not weldable; join with epoxy adhesive or mechanical fasteners.
Can CEM-3 be formed, bent or molded?
Pressed from prepreg at 170–180 °C under 2–4 MPa. The cured board cannot be re-formed; only flat cutting operations apply.
What surface finishes work on CEM-3?
Standard PCB route: electroless copper and plating, screen-printed green solder mask, then HASL, OSP or ENIG. Bake boards at 105–120 °C before soldering to drive off moisture and prevent blistering.
CEM-3 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 |
|---|---|---|
| epoxy resin (brominated/FR)Flame-retardant epoxy matrix with curing agent | 28 – 40 | 34 |
| non-woven E-glass mat (core)core glass mat | 30 – 45 | 38 |
| woven E-glass cloth (surface plies)top and bottom surface glass cloth | 12 – 25 | 18 |
| filler (ATH / silica / TiO2)Flame-retardant filler; white boards contain TiO2 | 2 – 15 | 8 |
| copper foil (clad grades only)18-70 um electrodeposited copper foil, clad laminates only | 0 – 12 | 0 |
CEM-3 HTG — frequently asked
What is CEM-3 HTG used for?
CEM-3 HTG is typically used for double-sided PCB substrates, cost-sensitive electronic assemblies and general insulating boards. In short: lower-cost FR-4 substitute; easier drilling than FR-4; glass-mat core composite.
What is the tensile strength of CEM-3 HTG?
CEM-3 HTG has a typical tensile strength of 165 MPa (23.9 ksi) — weaker than 55% of composite grades. Strength varies by condition: see the 3 listed tempers.
Is CEM-3 HTG easy to machine?
Reasonably — machinability is rated good (62/100, better than 75% of composite grades). Can be punched after preheating to 40–60 °C and drilled at high speed with lower drill wear than FR-4. Use carbide tooling with vacuum extraction to control glass dust and prevent delamination.
Can CEM-3 HTG be welded?
Thermoset laminate — not weldable; join with epoxy adhesive or mechanical fasteners.
What surface finishes work on CEM-3 HTG?
Standard PCB route: electroless copper and plating, screen-printed green solder mask, then HASL, OSP or ENIG. Bake boards at 105–120 °C before soldering to drive off moisture and prevent blistering.
Can CEM-3 HTG be formed, bent or molded?
Pressed from prepreg at 170–180 °C under 2–4 MPa. The cured board cannot be re-formed; only flat cutting operations apply.
What is the maximum service temperature of CEM-3 HTG?
CEM-3 HTG is rated for continuous use to about 140°C (284 °F), and briefly to 288°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- IPC-4101 Specification for Base Materials for Rigid and Multilayer Printed Boards — IPC (2021)
- NEMA LI 1 Industrial Laminated Thermosetting Products — NEMA (1998)
- IEC 61249-2-21 (halogen-free base material requirements) — IEC (2003)
- Printed Circuits Handbook — base material properties — McGraw-Hill (2016)
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.