Ceramic PCBs

High Temperature, Harsh Environments and High Frequency Applications

About Ceramic PCBs

With recent advances in the market, Ceramic PCBs have become a more viable option for PCB designers. With the continuing requirements for miniaturisation, microelectronics and high-power packages, the need for substrates capable of withstanding high operating temperatures, whilst offering outstanding thermal performance is a must. Semiconductors from materials such as Silicon Carbide and Gallium Nitride operate at high temperatures meaning associated circuits need to be ceramic. Ceramic Interposers are also becoming popular for thermal management and when a hermetic package is required where no moisture can be tolerated and no outgassing materials can be used. 

Ceramics are also used for high frequency applications due to low signal loss and as well as resisting UV they are chemical resistant, have no outgassing and are completely water resistant.

Ceramics have been widely used in electronics/electronic components for years due to their thermal, and mechanical advantages. With recent advances in technology and manufacturing capabilities, they are now replacing entire PCBs.

Since their introduction, Ceramic PCBs have received enormous attention from the industry as an effective solution to a range of electronic issues. The superior Thermal Conductivity of ceramics with low signal loss for high frequency being the leading reasons that more and more industries are turning to ceramics for their PCB design.

Advantages Over Other Technologies

Heat dissipation is the key advantage that Ceramic has over more conventional materials such as FR4 and Metal Clad PCBs. With components being placed directly on the boards, and no isolation layer, the flow of heat through the boards is far more efficient. Depending on the material chosen, the Thermal Conductivity values range from 24-180W/mK.

In addition to this, Ceramic material can withstand high operating temperatures (over 800°C) and has a very low CTE (Coefficient of Thermal Expansion), allowing for additional compatibility options for circuit design.

Ceramic Panel

Full list of advantages:

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

Ceramic Substrate Options

  • Al2O3 (Alumina Oxide) - Most commonly 96%, this is the most standard and cost-effective option, with a Thermal Conductivity of around 24W/mK. A 99.6% option is also available.
  • AlN (Aluminium Nitride) - Required when Thermal Conductivity is the driver. With a TC of around 170W/mK it is the best option for highly demanding systems.
  • SiN (Silicon Nitride) - More resistant to shock than other substrate options, with a higher fracture toughness and bending strength. Well suited for automotive applications where structural reliability is key.

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

Highlighted in the table are some of the extreme values that suit each material for different applications -

  • Al2O3 has better light reflectivity - making it suited for LED products.
  • AlN has superior Thermal Conductivity - making it suitable for very high power applications requiring the best possible thermal substrate.
  • SiN has a very low CTE. Coupled with a high Rupture Strength it can withstand stronger thermal shock.
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Once we receive your enquiry we will be in contact to discuss what data files we need to supply a quotation.

See below for more information on Al2O3, AlN, and other technologies available.
Alumina PCB (96% & 99.6%)
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Alumina Oxide (Al2O3) PCB (96% & 99.6%)

The most common material used for Ceramic PCBs is Alumina Oxide (96%). A naturally excellent electrical insulator with strong thermal properties. The thermal conductivity of Alumina is not as high as Aluminium Nitride, however it is still noticeably higher than the best performing Metal Clad PCB materials with a Thermal Conductivity in the region of 24W/mK. Another variant of this is Al2O3 (99.6%) which has a higher Thermal Conductivity, in the region of 29W/mK.

A high light reflectivity, along with good thermal properties makes Alumina Oxide well suited for LED applications. Whilst low values of thermal expansion and signal loss make it suitable for a range of applications including sensor modules, high-frequency systems and cooling systems.

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 a higher thermal conductivity is required then Aluminium Nitride (AlN) will be required. AlN has a superior thermal conductivity; depending on options, the conductivity achieved will be between 150-170W/mK.

This, along with a very low CTE and high operating temperatures makes AlN suitable for a variety of applications including; High power LEDs, testing, sensors, Integrated Components (ICs) and more.

Advantages

  • Superior values of Thermal Conductivity (Up to 170W/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
  • Thermal Conductivity value between Al2O3 and AlN at 85-90W/mK run at extremely high temperatures, but in addition it has a
  • High operating temperatures of over 800°C
  • Very low CTE
  • High rupture strength - makes it a more attractive solution to harsher environments or environments with high levels of vibration.
  • 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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Which surface finish should I choose for Ceramic PCBs? The choice will depend on required storage, the end application, the assembly process, the design of the PCB itself. Not all FR4 surface finishes are suitable for ceramic PCBs. Those available are detailed below and we would be pleased to help you further with any questions you may have regarding a suitable finish for your application.

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.

Ceramics FAQ - Frequently Asked Questions
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What is a Ceramic PCB?

A ceramic printed circuit board is a PCB manufactured with copper directly on a ceramic substrate rather than a common alternative such as FR4. Ceramic substrate choices include Al2O3 (Alumina Oxide), AlN (Aluminium Nitride) and SiN (Silicon Nitride).

Why use ceramic PCB?

Heat management and high frequency applications due to low signal loss are the main advantages of using ceramics. For heat consideration, many high-power packages have the need for substrates that are capable of withstanding high operating temperatures. Ceramics from DK-Daleba have a maximum operating temperature of over 800°C together with high Thermal Conductivity values of up to 180W/mK. They also have a very low CTE (Coefficient of Thermal Expansion) and offer advantages for Hermetic packages with their 0% water absorption.

What is the Thermal Conductivity of Ceramic substrates?

24-180W/mK - depending on the material chosen.

What is the most popular Ceramic substrate?

Al2O3 (Alumina Oxide) - the 96% is the most common substrate and a very cost-effective option and has a Thermal Conductivity of around 24W/mK. A 99.6% option is also available.

What are the advantages of AlN (Aluminium Nitride)?

AlN (Aluminium Nitride) is often the choice when Thermal Conductivity is the driver. With a Thermal Conductivity of around 170W/mK it is the best option for highly demanding systems.

What are the advantages of SiN (Silicon Nitride) for automotive applications?

SiN (Silicon Nitride) has a higher fracture toughness and bending strength than other substrates making it more resistant to shock. It is therefore a good choice for automotive applications where structural reliability is key.

What is the difference between DBC and DPC ceramics?

Direct Bonded Copper (DBC) is used when a high copper thickness is required - 140um (4oz)-350um (10oz). The copper is bonded to the Ceramic substrate on one or both sides using a high-temperature oxidation process. Direct Plated Copper (DPC) is the newest development in the field of Ceramic Substrate PCBs and using this method can result in copper thickness' ranging from 10um (≈ 1/3oz) to 140um (4oz). With DPC track printing and etching is then performed with the thin Copper allowing for very fine tracks and reduced undercutting.

What panel sizes are offered for ceramic circuits?

Standard panel size is to 115 x 115mm but as a special up to 170 x 250mm can be achieved.

What finish options are offered for ceramic circuits?

For ceramics ENIG/ENEPIG/EPIG/Immersion Silver/Immersion Tin and OSP finishes can be applied.

What are the main advantages of a Ceramic PCB?

Maximum operating temperatures of over 800°C, high Thermal Conductivity of up to 180W/mK, very low CTE (Coefficient of Thermal Expansion), 0% water absorption for Hermetic packages and fine micro circuit applications with the DPC production method.

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 Al2O3 Alumina Oxide Al2O3
Direct Bonded Copper Direct Bonded Copper
Alumina Oxide Al2O3 Alumina Oxide Al2O3
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
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