Free engineering tool
LED junction temperature calculator for aluminum PCB
Compare 0.7, 1.0, 1.5 and 2.0 W/m·K dielectric grades on the same SMD layout. The table is a board-layer estimate, not a lifetime rating and not a contract number.
Dielectric comparison
Four grades, same layout
1.5 / 2.0 are market benchmarks, not Lumina production grades.
| Grade | t (mm) | Zth | Dielectric rise | vs 1.0 |
|---|---|---|---|---|
| 0.7 volume | 0.20 | 2.86 | 0.7 °C | +0.2 °C |
| 1.0 commercial | 0.20 | 2.00 | 0.5 °C | +0.0 °C |
| 1.5 marketnot Lumina | 0.10 | 0.67 | 0.2 °C | -0.3 °C |
| 2.0 marketnot Lumina | 0.10 | 0.50 | 0.1 °C | -0.4 °C |
Layer rise at 1.0 commercial
Estimate only. Solder voids and fixture contact change the real board. Send Gerber if you want a factory check on a volume stackup.
Ask for a board quotePhysical Model & Formulas
Complete 1D Thermal Resistance Chain
From LED PN-junction to ambient air: transparent formulas with zero hidden math.
Total junction temperature equals ambient temperature plus the cumulative temperature rise across each thermal layer.
Internal chip rise. Uses electrical wattage and datasheet Rθ j-sp without derating.
The MCPCB bottleneck (99% of board Rth). Pheat = 75% electrical. Aeff = board area ÷ LED count.
Natural convection into still air. Accounts for 60%–80% of total system rise.
0.7 vs 1.0 vs 2.0
Same thickness and typical thin high-k stacks
In the real market, volume 0.6–0.8 W/m·K (shown as 0.7) and 1.0 commercial boards use 0.20 mm dielectric to reliably pass 3000 V Hi-Pot isolation. High-k laminates (1.5 and 2.0 W/m·K) are typically sold as thin 0.10 mm sheets to maximize heat transfer. The table automatically compares these realistic commercial production stacks.
Aluminum base thickness barely moves this 1D vertical model. It still matters for mechanical stiffness and horizontal heat spreading.
Related notes: LED aluminum PCB heat dissipation · aluminum PCB fabrication.
Data Sources & Engineering References
Every preset in this calculator references verified manufacturer datasheets and test standards:
SMD LED Package Thermal Resistances:
- • Bridgelux SMD 2835 0.2W 3V (DS534): 27 °C/W @ 60 mA (2.9 V), Tj max 125 °C. Datasheet ↗
- • Samsung LM281B+ 0.5W: 25 °C/W @ 150 mA, Tj max 115 °C. Datasheet ↗
- • Bridgelux SMD 2835 1W 9V (DS234): 12 °C/W @ 100 mA (9.2 V). Datasheet ↗
- • Lumileds LUXEON 3030 2D (DS207): 12 °C/W @ 120 mA (6.1 V), Tj max 125 °C. Datasheet ↗
- • Cree LED J Series® 5050 (JQ5050 9V): 3.0 °C/W @ 400 mA (9.3 V). Datasheet ↗
Substrate Test Methods & Benchmarks:
- • Lumina In-House CCL-E Substrate: Verified by Microtek Testing Services (CNAS Lab, Report #46724) under ASTM D5470-17. Dielectric k = 0.98 W/m·K, Zth = 2.11 K·cm²/W (99% of total board resistance).
- • Lumina Volume Production Material: Yuxin batch inspection (0.73 mm board, 12 µm copper, 210–220 µm dielectric, 3000 V Hi-Pot).
- • Ventec VT-4A Series IMS: 1.6 W/m·K (VT-4A1) and 2.2 W/m·K (VT-4A2), standard 75–100 µm dielectric options. Datasheet ↗
- • Bergquist Thermal Clad®: MP series (1.3 W/m·K dielectric, 76 µm). Overview ↗
FAQ
Calculator questions
Is this a lab measurement of junction temperature?
No. It is a one-dimensional estimate. Package rise uses electrical power times datasheet Rθ j-sp. Board rise uses heat power through dielectric thickness and area. Real solder voids and fixture contact will move the number.
Why do 0.7 and 2.0 sometimes look almost the same?
Dielectric rise scales with heat flux. On a sparse 2835 strip the board layer is often around 1 °C. Package and housing are larger. On a dense 5050 module with narrow copper the same grade change can be several degrees. Change copper width and watch the table.
Do you produce 1.5 and 2.0 W/m·K material?
Those two columns are market benchmarks, not Lumina production grades. Our volume lighting boards are 0.6–0.8 W/m·K. 1.0 W/m·K commercial material is available when the job needs it.
Why does my bare LED board feel very hot to the touch during bench testing?
Human skin senses pain above 50–55 °C. For LED chips, 60–75 °C is well below the 115–125 °C maximum rating. During a bench test with no luminaire chassis, a bare MCPCB has only a few square centimeters exposed to still air, so it acts as an inefficient heat sink and rises in temperature. In a finished fixture, the board conducts heat into an aluminum enclosure with a far larger convective surface area.
What area should I enter for an LED strip?
Use length × copper pour width ÷ LED count. Do not use the full board width if heat only travels under a narrow copper run.
Need a volume stackup, not a max-spec quote?
Send Gerber, LED type, and quantity. We quote 0.6–0.8 W/m·K volume boards as standard, and 1.0 when the job needs it.