Bare Aluminum Nitride (AlN) Substrate for High-Power SiC and IGBT Modules

Bare AlN Substrates Applications

• Power Electronics Modules（IGBT, SiC, MOSFET, Rectifiers）

  ✅Key Advantages

  1. Lower thermal resistance in high-power modules – bare aluminum nitride substrate with ≥170 W/m·K thermal conductivity reduces baseplate temperature rise at power densities above 10 W/cm² compared with alumina substrates.
  2. Improved power cycling robustness – CTE close to silicon and SiC helps keep solder and sintered joints within acceptable strain levels during thousands of thermal cycles.
  3. High isolation voltage in compact layouts – dielectric strength around 15–20 kV/mm allows safe creepage and clearance distances even in thin bare AlN ceramic substrates.

  ✅ Problem Solved

  A power module manufacturer converted a 75 kW inverter platform from alumina to bare aluminum nitride substrates while keeping the same outline and mounting pattern. Thermal simulations and tests showed a junction temperature reduction of about 15–20 °C at peak load, allowing the module to run at a higher continuous current without exceeding the original temperature limit. Field data over 3,000 power cycles indicated a reduction in solder fatigue failures, and the customer extended the expected module lifetime by approximately 30% while maintaining existing mechanical interfaces and assembly processes.

• LED /UV LED /Laser Diode Packaging

  ✅Key Advantages

  1. Efficient heat removal for high-brightness LEDs – bare aluminum nitride ceramic substrate spreads heat away from LED chips more effectively than alumina-based carriers, limiting junction temperature rise under continuous operation.
  2. Stable optical output over lifetime – better thermal control on bare AlN substrates helps reduce lumen depreciation and wavelength drift in LED and UV LED engines.
  3. Compact multi-die layouts – the combination of high thermal conductivity and dielectric strength allows dense chip arrays on a single bare AlN substrate while maintaining electrical isolation.

  ✅ Problem Solved

  An OEM building 365 nm UV LED curing modules moved from alumina ceramic boards to bare aluminum nitride substrates with similar chip layout. Under a 50 W optical output condition, the maximum measured junction temperature dropped by about 12 °C, and long-term testing at 5,000 hours showed a reduction in optical power degradation from roughly 20% to around 11%. The more stable junction temperature on bare AlN substrate also reduced color shift, which simplified the customer’s calibration and binning process and allowed them to extend the warranty on the UV modules.

• RF /Microwave/5G Modules and Industrial Power Supplies

  ✅Key Advantages

  1. Low dielectric loss with strong heat spreading – bare AlN ceramic substrate combines low dielectric loss at microwave frequencies with high thermal conductivity, supporting compact RF power amplifiers.
  2. Stable impedance over temperature – controlled CTE and dielectric constant help maintain line impedance and matching conditions over a wide operating temperature range.
  3. Reliable isolation in high-voltage industrial power supplies – bare aluminum nitride substrate provides stable dielectric strength at elevated temperatures for isolated power stages and sensing circuits.

  ✅ Problem Solved

  A manufacturer of RF power amplifiers for telecom infrastructure introduced bare AlN substrates for a 200 W L-band amplifier stage. Compared with an alumina-based design, the amplifier running on bare aluminum nitride substrate showed about 8–10 °C lower baseplate temperature at rated output and a measurable improvement in gain stability over the full temperature range. In parallel, an industrial power supply customer adopted bare AlN ceramic substrates in a high-voltage DC supply, achieving the required isolation margin with a thinner board stack and freeing more space for magnetic components in the same housing.

Product Use Guide – Bare Aluminum Nitride Substrate

• Installation

  1. Check each bare aluminum nitride substrate for visible chips or cracks under appropriate lighting before assembly.
  2. Use clean, non-metallic tweezers or vacuum pens when handling thin bare AlN substrates to avoid edge damage.
  3. Place the substrate on a flat, clean support surface during screen printing, metallization or bonding processes to minimize bending stress.

• Operation

  1. Design the assembly so that the bare AlN substrate is supported over a large area, avoiding local point loads from mounting screws or posts.
  2. Maintain operating temperatures within the specified range for the aluminum nitride substrate material and any attached solder or adhesive system.
  3. For power modules, verify junction-to-case thermal resistance and total thermal path using realistic power cycling profiles.

• Storage

  1. Store bare aluminum nitride substrates in their original trays in a dry, clean environment, ideally below 60% relative humidity.
  2. Avoid stacking heavy objects on top of substrate trays to prevent warp or microcracks over time.
  3. For long-term storage, keep packed trays inside moisture-barrier bags with desiccant and replace desiccant according to humidity indicators.

•  Cleaning

  1. If cleaning is required, use particle-free solvents such as isopropyl alcohol or deionized water and dry with oil-free compressed air or nitrogen.
  2. Do not use abrasive pads or aggressive mechanical brushing on polished bare AlN substrate surfaces.
  3. Avoid alkaline cleaners that might attack metal traces if metallization has already been applied downstream.

• Precautions and Misoperation Points

  1. Do not subject thin bare aluminum nitride ceramic substrates to sudden temperature changes beyond the recommended thermal shock limits.
  2. Avoid bending or twisting the substrate during assembly, especially for thicknesses below 0.5 mm.
  3. Do not clamp the substrate at a single edge while applying high mechanical force on the opposite side.

• Typical Misuse and How to Address It

  1. Issue: Polished bare AlN substrate shows scratches after cleaning.
  Cause: Wiping with dusty cloths or abrasive tissues.
  Action: Switch to lint-free wipes and filtered solvents; specify double-side polished bare aluminum nitride substrate only where necessary to limit rework.

  2. Issue: Cracks appear near mounting holes during screw tightening.
  Cause: Excessive torque and lack of washers spreading the load.
  Action: Use torque-limited drivers, introduce compliant washers or metal clamps, and adjust drawing so that bare AlN substrate holes are sized with appropriate clearance.

  3. Issue: Measured thermal performance is below expectation in a prototype.
  Cause: Interface material or mounting surface dominates thermal resistance even with high-conductivity bare AlN substrate.
  Action: Re-evaluate thermal interface materials, flatness of the baseplate and clamping pressure before changing the bare aluminum nitride substrate thickness or grade.

FAQ – Bare Aluminum Nitride Substrate

1. Q: What is the main benefit of using a bare aluminum nitride substrate instead of an alumina substrate in power modules?
   A: A bare aluminum nitride substrate typically offers thermal conductivity above 170 W/m·K, while alumina is often in the 20–30 W/m·K range, so the bare AlN substrate can significantly reduce thermal resistance and improve junction temperature margin in high-power modules.
2. Q: How thin can a bare AlN substrate be made for LED or laser diode packaging?
   A: For many designs, bare aluminum nitride substrates with thickness from 0.25 to 0.5 mm are used, and thinner formats may be possible depending on panel size, flatness requirements and handling conditions.
3. Q: What thermal conductivity grades are available for bare aluminum nitride substrates?
   A: Typical thermal conductivity for bare AlN substrate materials ranges from about 140 W/m·K up to 170–200 W/m·K, depending on the powder, sintering route and grade selected.
4. Q: Can bare AlN ceramic substrates be used directly in DBC or AMB processes?
   A: Yes, many DBC and AMB processes use bare aluminum nitride ceramic substrates as starting plates; the copper or other metals are bonded onto the bare AlN substrate in a subsequent process step.
5. Q: Is a bare AlN substrate compatible with high-frequency RF or microwave circuits?
   A: Bare aluminum nitride substrates have a dielectric constant around 8–9 and low loss tangent, so they are widely used for RF, microwave and 5G modules where both thermal management and RF performance must be balanced.
6. Q: Can a bare aluminum nitride substrate be laser machined or drilled after sintering?
   A: Yes, thin bare AlN substrates can be laser machined for vias, slots and shaping, but design rules for hole diameter, spacing and edge distances should be observed to maintain mechanical strength and yield.

Bare Aluminum Nitride Substrate

• ⭐️⭐️⭐️⭐️⭐️
  We switched our 30 kW inverter prototypes to a bare aluminum nitride substrate from ADCERAX to gain more thermal headroom. The new ceramic baseplate allowed us to keep the same outline but drop the junction temperature by around 15 °C at full load, which made the reliability calculations much more comfortable.
  -- Michael R., Power Electronics Engineer, E-Motion Drives GmbH
• ⭐️⭐️⭐️⭐️⭐️
  For one of our power supply platforms we needed several sizes of bare AlN ceramic substrates with tight thickness tolerances. ADCERAX supported a mix of standard plates and custom dimensions in one package, and the dimensional consistency between lots has been stable enough for our SMT and assembly lines.
  -- Sofia L., Senior Buyer, NorthWave Industrial Power Inc.
• ⭐️⭐️⭐️⭐️⭐️
  Our high-density UV LED arrays are built on thin bare aluminum nitride substrates to control junction temperature. After moving to ADCERAX plates, we saw more stable warpage and smoother surfaces, which helped improve our chip bonding yield and uniformity of optical output.
  -- Kenji S., LED Module Development Manager, Lumisense Optoelectronics Co.
• ⭐️⭐️⭐️⭐️⭐️
  We use bare AlN substrates for a family of RF power amplifier modules where both loss and heat dissipation matter. The ADCERAX bare AlN substrate parts held up well through thermal cycling and assembly, and the mechanical tolerances matched our line’s fixturing without extra rework.
  -- Emily T., RF Hardware Lead, AeroLink Systems Ltd.