A ceramic PCB for high-power LEDs uses an alumina (Al2O3) or aluminum nitride (AlN) substrate instead of FR-4 or a metal-core board, so heat flows from the LED through an electrically insulating material that conducts heat well. Alumina (about 24–26 W/(m·K) for 96% grades) suits most visible-light LED modules at moderate power density and costs less; AlN (about 140–230 W/(m·K) depending on grade) is chosen for dense arrays, high drive current, compact heat sinks and many UV-C designs, where junction temperature margin is tight. Choose from the LED’s junction temperature at your drive current, not from material preference. UV-C adds checks on materials exposed to the light and on cleaning. This guide compares the materials, shows how to estimate junction temperature, covers UV-C points, and lists what to send for a quote.
1. Why Use Ceramic for High-Power LEDs?
| Board type | Heat path from LED | Strengths | Limits |
|---|---|---|---|
| FR-4 | Through laminate, helped by copper and thermal vias | Lowest cost | Poor heat path for high power |
| Metal-core (aluminum) | Through a thin polymer dielectric to the metal base | Low cost, good for many LED lighting products | The dielectric layer is the thermal bottleneck; limited insulation |
| Alumina ceramic | Through the ceramic itself | Insulating and conductive, stable, matches LED package expansion better | Brittle; thermal conductivity lower than AlN |
| AlN ceramic | Through the ceramic itself | Highest thermal conductivity of common ceramics | Higher cost |
Ceramic also expands much less than metal-core boards, closer to the LED package, which reduces stress on solder joints in thermal cycling. For a full material comparison, see our ceramic PCB guide.
2. Alumina vs AlN: What Do the Numbers Say?
| Material (maker’s grade) | Thermal conductivity, W/(m·K) | CTE, ppm/K | Source |
|---|---|---|---|
| Alumina 96% (CoorsTek ADS-96R) | 26 at 20°C; 20 at 100°C | 6.4 (25–200°C) | CoorsTek thick-film design guide |
| Alumina 99.5% (CoorsTek ADS-995R) | 31 at 20°C; 23 at 100°C | 6.4 (25–200°C) | Same |
| AlN (CoorsTek AlN 140 / 180) | 140 / 180 at 20°C | 4.6 (RT–300°C) | CoorsTek AlN datasheet |
| AlN (MARUWA AN-170 / 200 / 230) | 180 / 200 / 230 at 25°C | 4.6 (40–400°C) | MARUWA AlN substrates |
Two points matter for LEDs. First, AlN conducts heat five to nine times better than alumina, so it spreads heat from a small, dense source much faster. Second, thermal conductivity falls as temperature rises, especially for alumina, so compare at your operating temperature. Values are makers’ typical data for their grades; ask your supplier which grade it uses.
3. How Do You Decide Between Alumina and AlN?
Estimate the LED junction temperature on each candidate. LED makers give the method; for example, ams OSRAM’s OSLON UV application note AN155 (February 2026) uses:
Tj = Ts + IF × VF × RthJS
where Ts is the solder-point temperature, IF and VF the forward current and voltage, and RthJS the junction-to-solder-point thermal resistance from the LED datasheet. Ts depends on the board, thermal interface and heat sink, which is where the substrate choice shows up. As an illustration only: with Ts = 60°C, IF = 0.35 A, VF = 6 V and RthJS = 10 K/W, Tj = 60 + 0.35 × 6 × 10 = 81°C. Cree LED’s thermal management note describes the same split between package and board path.
| Choose alumina when | Choose AlN when |
|---|---|
| Power density is moderate and the board has room to spread heat | Emitters are packed closely and hot spots limit drive current |
| Junction temperature has margin on the bench or in the model | Junction temperature is close to the LED’s limit |
| Cost matters and the design is a common visible-LED module | The heat sink or contact area is small |
| Higher drive current is needed for optical output |
Before switching to AlN because a board runs hot, check the thermal interface and heat sink contact: a poor interface can cost more temperature than the substrate difference. Our alumina vs AlN cost guide covers the price side.
4. What Changes for UV-C LEDs?
UV-C LEDs (roughly 200–280 nm) are used for disinfection of air, water and surfaces. They are less efficient than visible LEDs, so more of the input power becomes heat, and their output and lifetime depend strongly on junction temperature. That makes AlN common in UV-C modules. UV-C also adds checks that visible LED boards do not need:
| Item | What to check |
|---|---|
| Materials in the light path | Adhesives, coatings, inks, encapsulants and plastics near the emitter can degrade under UV; use materials with UV exposure data |
| Chemical compatibility | Some materials outgas and affect the LED; follow the LED maker’s compatibility guidance (AN155 sections 2.4 and 3.4 for OSLON UV) |
| Surface finish and reflectors | Visible appearance says nothing about UV reflectance; ask for data if the finish has an optical role |
| Cleaning | Use cleaning methods approved by the LED maker |
5. What Copper, Finish and Process Should You Specify?
| Item | Options and notes |
|---|---|
| Metallization | DPC (plated copper, fine lines, plated vias) suits most LED packages; thick film for simpler circuits; DBC for high-current power circuits |
| Copper thickness | Enough for current and heat spreading under the LED pads |
| Surface finish | ENIG, ENEPIG or silver depending on the LED package, solder and any wire bonding |
| Vias | Plated or filled vias if the circuit must pass through the ceramic |
| Flatness | Matters for heat sink contact; state a limit if needed |
| Outline | Laser-cut or scored; brittle ceramic needs careful depaneling |
For DPC versus DBC, see our DPC vs DBC guide.
6. What Should You Send for a Quote?
- Gerber files and a drawing with ceramic type, thickness, copper thickness and finish.
- LED datasheet, drive current and number of emitters.
- Heat sink and thermal interface, if known.
- For UV-C: wavelength and the materials near the emitter.
- Quantity, and whether you need bare boards or assembly.
If you are unsure between alumina and AlN, ask for both on the same drawing so the quotes compare like for like. Our guide to ordering your first ceramic PCB prototype lists the files in detail.
How Can We Help?
We build alumina and AlN ceramic boards with DPC, DBC and AMB metallization. Send your files and LED details and we will quote alumina and AlN options side by side; bare-board quotes come back within 2 hours. See our ceramic PCB manufacturing and LED PCB pages for the boards we make.
Conclusion
For high-power LEDs, alumina is the cost-effective ceramic when junction temperature has margin; AlN, with several times the thermal conductivity, is the choice for dense arrays, high drive current, compact heat sinks and many UV-C designs. Estimate junction temperature with the LED maker’s method, check the thermal interface, and for UV-C check every material in the light path. Contact us for a quote.
FAQ
Is alumina good enough for high-power LEDs? Often, when power density is moderate and the junction temperature has margin; check it with the LED maker’s thermal method.
Is AlN always better for UV-C LEDs? It gives the best heat path, which UV-C usually needs, but reliability also depends on materials near the emitter, cleaning and the heat sink.
Can I use a metal-core PCB instead of ceramic for LEDs? For many LED lighting products, yes. Ceramic is chosen when the polymer dielectric of a metal-core board limits heat flow or insulation.
What is the thermal conductivity of alumina and AlN? About 24–31 W/(m·K) for alumina and 140–230 W/(m·K) for AlN at room temperature, depending on grade.
Does QueenEMS make ceramic LED boards? Yes, in alumina and AlN, with DPC, DBC or AMB metallization.
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