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Ceramic Circuits

Operating temperature of 800°c+, high frequency and harsh environments

Ceramic Circuits

Choosing a ceramic substrate for a PCB design is becoming more popular. High maximum operating temperatures of 800°C+ allows for the much higher operating temperatures Silicon Carbide and Gallium Nitride Semiconductors can now operate at. The new DPC (Direct Plated Copper) method of production also allows for miniaturisation and microelectronics not possible with other methods. Ceramics are UV resistant and their inert nature also makes these substrates ideal when a hermetic package is required when no outgassing or moisture can be tolerated.

Low signal loss makes ceramics ideal for high frequency applications but the superior thermal conductivity of up to 180W/mK is often why designers are turning to ceramics.

Advantages Over Other Technologies

Other PCB substrates such as FR4 and Metal Clad PCBs simply do not have the same heat dissipation properties of ceramics. With no isolation layer necessary components are mounted directly onto the boards making the flow of heat through the circuit much more efficient. Depending on substrate choice ceramics offer Thermal Conductivity values ranging from 24-180W/mK. This is matched by excellent CTE (Coefficient of Thermal Expansion) values.

Advantages include:

  • Thermal Conductivity up to 180W/mK
  • Hermetic packages - 0% water absorption
  • Excellent Coefficient of Thermal Expansion (CTE)
  • Low signal loss - ideal for high-frequency applications
  • Maximum operating temperatures 800°C+
Ceramic Panel

Available Ceramic Substrates

  • Al2O3 (Alumina Oxide) - The most popular material is the 96% variant. This is the most cost-effective substrate and has a Thermal Conductivity of around 24W/mK. A 99.6% option is also available.
  • AlN (Aluminium Nitride) - When Thermal Conductivity is important this is the material to consider with a TC of around 180W/mK.
  • SiN (Silicon Nitride) - A choice for many automotive applications as it is more resistant to shock than other materials. It has a good bending strength and a higher fracture resistance making it ideal when structural reliability is key design factor.

Ceramic Material Specifications

Property Unit Al2O3 (96%) Al2O3 (99.6%) AlN SiN
Thermal Conductivity W/mK 24 29 180 85
Maximum Operating Temperature (MOT) °C >800 >800 >800 >800
Coefficient of Thermal Expansion (CTE) x 10¯6/K 6.7 6.8 4.6 2.6
Dielectric Constant - 9.8 9.9 9 9
Signal Loss x 10¯3 0.2 0.2 0.2 0.2
Light Reflectivity % 70/85 75 35 -
Dielectric Strength KV/mm ≥15 ≥15 ≥15 ≥15
Rupture Strength Mpa 400 550 450 800
Alumina PCB (96% & 99.6%)
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Alumina Oxide (Al2O3) PCB (96% & 99.6%)

The most popular ceramic with a Thermal Conductivity in the region of 24W/mK, a higher figure than the best performing Metal Clad PCB materials.

Available in two different, the 96% being the most cost effective and popular. The 99.6% variant has a higher Thermal Conductivity, in the region of 29W/mK.

Advantages

  • High values of Thermal Conductivity (24-29W/mK)
  • High operating temperatures to over 800°C
  • Low CTE
  • Suitable for high frequency applications due to low signal loss
  • High light reflectivity
  • Possibility for Hermetic packages with 0% water absorption

Technical Specifications

Download our complete design rules below. If you have different requirements, or have any questions please contact us.

Alumina 96% Manufacturing Capabilities

Aluminium Nitride PCB
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Aluminium Nitride (AlN)

If the driver in a design is high thermal conductivity then Aluminium Nitride (AlN) will be the right choice. AlN has a superior thermal conductivity of upto 180W/mK.

With its high temperature and a very low CTE makes AlN suitable for a variety of applications including Semiconductors, High power LEDs, testing and sensors.

Advantages

  • Superior values of Thermal Conductivity (Up to 180W/mK)
  • High operating temperatures to over 800°C
  • Very low CTE
  • Suitable for high frequency applications due to low signal loss
  • Possibility for Hermetic packages with 0% water absorption

Technical Specifications

Download our complete design rules below. If you have different requirements, or have any questions please contact us.

Aluminium Nitride Manufacturing Capabilities

Silicone Nitride PCB
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Property Unit SiN
Thermal Conductivity W/mK 85
Maximum Operating Temperature (MOT) °C 1000
Coefficient of Thermal Expansion (CTE) x 10¯6/K 2.6
Dielectric Constant - 9
Signal Loss x 10¯3 0.2
Light Reflectivity % -
Breakdown Voltage KV/mm 15
Rupture Strength Mpa 800
  • SiN has a high rupture strength - making it a more attractive solution for environments with high levels of vibration such as automotive.
  • The Thermal Conductivity value of 85-90W/mK sits between Al2O3 and AlN
  • High operating temperatures of over 800°C
  • Very low CTE
  • Suitable for high frequency applications due to low signal loss
  • Possibility for Hermetic packages with 0% water absorption
Ceramics - Process Methods & Capabilities
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Ceramic - Thick Film

  • Thick Film technology involves the addition of layers of conductor (Copper or Silver) onto a Ceramic substrate via screen printing processes.
  • Suitable for use with Al2O3/AlN and Sapphire substrates.
  • A cost-effective solution with fewer manufacturing processes than other methods.
  • With a conductor thickness between 7-20um it is not well suited to power electronics requiring high current capacity.
  • Due to conductor application it is also unsuitable for designs requiring fine tracks and/or plated/filled vias.
Closeup of Ceramic Thick Film
Ceramic Thick Film Technology - layers of conductor onto a ceramic substrate

Ceramics - DBC (Direct Bonded Copper)

  • Direct Bonded Copper (DBC) is used when a high copper thickness is required - 140um (4oz)-350um (10oz). Heavy Copper.
  • The copper is bonded to the Ceramic substrate on one or both sides using a high-temperature oxidation process.
  • The copper and substrate are heated in an atmosphere of nitrogen containing about 30 ppm of oxygen; under these conditions, a copper-oxygen eutectic forms which bonds successfully both to copper and the oxides used as substrates.
  • The copper layers can then be etched using standard PCB technology to form an electrical circuit.
  • Laser drilling is then used for any through hole requirements and profile machining.

Disadvantages:

  • Due to the Oxidisation bonding process there can be a slight reduction in Thermal Conductivity created by a void between the Copper and Ceramic layers.
Closeup of Ceramic Direct Bond Copper

Applications:

Main applications are high power modules, like IGBT, CPV, or any other wide bandgap device modules.

  • IGBT
  • High-Frequency Switching Power Supply
  • Automotive
  • Aerospace
  • Solar Cell Component
  • Power Supply for Telecommunication
  • Laser Systems
Closeup of Ceramic Direct Bonded Copper

Ceramics - DPC (Direct Plated Copper)

  • Direct Plated Copper (DPC) is the newest development in the field of Ceramic Substrate PCBs.
  • It involves plating the copper conductor layer to the copper substrate under high temperature and pressure conditions.
  • The addition of a thin titanium layer acts as a bonding interface between the copper and Ceramic layers.
  • A very thin layer of Copper is deposited at this stage coating the Ceramic substrate and any pre-drilled holes.
  • Track printing and etching is then performed with the thin Copper allowing for very fine tracks and reduced undercutting.
  • The panels are then plated up to the required end copper thickness.
  • Using this method can result in copper thickness' ranging from 10um (≈ 1/3oz) to 140um (4oz).
  • It also allows for the possibility of plated or filled vias. Something not possible with Thick Film or DBC technology.
Ceramic Direct Plated Copper - layers of conductor onto a ceramic substrate

Applications:

  • HBLED
  • Substrates for solar concentrator cells
  • Power semiconductor packaging including automotive motor control
  • Hybrid and electric automobile power management electronics
  • Packages for RF
  • Microwave devices
Closeup of Ceramic Direct Plated Copper

Ceramics - DPC vs DBC

Both DBC and DPC have the same advantages for high power applications, due to the use of a direct bond between Copper and the Ceramic substrate, therefore, the same key attributes for both of them are:

  • Outstanding Thermal Conductivity
  • High operating temperatures
  • Good mechanical strength; mechanically stable shape, good adhesion.
  • Excellent electrical insulation
  • Very good thermal conductivity
  • Superb thermal cycling stability
  • Good heat spreading

The differences come when looking at the design considerations and applications. DBC being suited to high current capacity, however limited on circuit design. DPC allowing for finer tracks and through hole connection.

Ceramic - Capabilities

Property DPC DBC
Compatible Substrates Al2O3 / AlN / SiN Al2O3 / AlN / SiN
Substrate Thickness (mm) 0.25/0.38/0.5/0.635.1.0/1.5/2.0 0.25/0.38/0.5/0.635.1.0/1.5/2.0
Copper Weight (oz) 10 - 140 140 - 350
Panel Sizes (mm x mm) Standard: 115 x 115mm
Special: Up to 170 x 250mm
Standard: 115 x 115mm
Special: Up to 170 x 250mm
Finish Options ENIG/ENEPIG/EPIG/Immersion Silver/Immersion Tin/OSP ENIG/ENEPIG/EPIG/Immersion Silver/Immersion Tin/OSP
Min Track Width (mm) 0.1 Dependant on Cu Weight
Minimum Hole Dia (mm) 0.08 0.08
Plated Via Aspect Ratio 5:1 N/A
PCB Surface Finishes - Ceramics
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Some of the surface finishes common with standard substrates such as FR4 are not suitable for ceramics. The finishes we offer are shown below. We would be happy to discuss with you further what might be a suitable finish for your boards.

OSP (Organic Solderability Preservative)

Usual thickness : 0.20-0.65µm
Shelf Life : 6 months

Unprotected copper will quickly oxidise which can cause soldering issues. OSP is a popular, low cost, environmentally friendly finish to prevent that oxidisation and provide an improved surface for solderability.

Populated with LEDs
Populated with LEDs
Silver Paste Conductor with ENIG Surface Treatment
Silver Paste Conductor with ENIG Surface Treatment
Immersion Tin Panel
Immersion Tin Panel
Alumina Oxide Al203
Alumina Oxide Al203
Direct Bonded Copper
Direct Bonded Copper
Alumina Oxide Al203
Alumina Oxide Al203
AIN Used For LED Products
AIN Used For LED Products
Saphire Alumina 0.4mm 2 Layer Silver Conductor
Saphire Alumina 0.4mm 2 Layer Silver Conductor
Alumina 0.5mm Silver Fin
Alumina 0.5mm Silver Fin