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What is Ceramic PCB: Its Materials and Types [2021 Updated]

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Mon, Jun 21, 2021

aluminum nitride PCB

A ceramic PCB is a special process board in which copper foil is directly bonded to alumina ( Al₂O₃), aluminum nitride ( AlN), beryllium oxide (BeO), or silicon carbide (SiC) ceramic substrate surface (single-sided or double-sided) at high temperatures. A ceramic PCB has 10 to 100 times more heat transfer properties than metal core PCBs and has good high-frequency performance and electrical properties. It also has a low expansion coefficient (CTE). A ceramic PCB is being considered to have the best properties of both FR4 and metal-core PCBs.

In this article, you will get a clear overview of the ceramic PCBs from the below parts.

Part 1: Ceramic PCB Base Materials

The ceramic compound material used for ceramic PCBs is a mixture of metallic oxides and nitrides. Commonly used materials are:

  • Aluminum Nitride (AIN)

    aluminum nitride

  • Aluminum oxide (Alumina) (Al₂O₃)

    alumina

  • Beryllium oxide (BeO)

    beo

Aluminum oxide ceramic (Al₂O₃) has a thermal conductivity that ranges from 24W/mK up to 30W/mK, and aluminum nitride ceramic has a thermal conductivity that ranges from 150-320W/mK. Aluminum oxide ceramic has a white color and is a much cheaper option if the application doesn't need the highest thermal performance. On the other hand, Aluminum Nitride (AIN) has a brown color and comparatively more expensive option but gives the best thermal performance.

Part 2: Ceramic PCB Conductor Materials

Ceramic core PCBs support the regular conductor materials of PCB manufacturing and their alloys. These key conductor materials are:

  • Copper (Cu)

  • Silver (Ag)

  • Gold (Au)

  • Platinum (Pt)

  • Palladium (Pb)

Part 3: Types of Ceramic PCBs

From the level of substrates, ceramic PCBs include the aluminum, AlN, BeO, Si₃N₄, hybrid substrate boards, etc. From the layers of the circuit boards, there are the single-layer, double-layer, and multilayer. Here we only put the ceramic PCB types according to the different ceramic substrates.

Alumina PCB

alumina PCB

Advantages: cheap price, good thermal conductivity and resistance, high hardness, high electrical insulation, strong corrosion-resistance, high biocompatibility

Applications: LEDs lamps of white light, infrared, VCSEL

Aluminum oxide (Al₂O₃) PCB, or alumina PCB, is the most used ceramic PCB in the current market due to its cheaper price and nice properties. Alumina has good thermal conductivity and electrical resistance. For this reason, when alumina PCB is used, there is no need for adding an insulation layer.

Alumina PCBs are mainly used for LEDs of 3W to 5 W power. Why? Because the thermal conductivity is not that good to meet the high-power devices demands.

Alumina has a higher thermal expansion coefficient than semiconductors. So you can't expect to use alumina PCBs for large-scale integrated circuits.

But in general, if your devices have not very high power requirements, alumina PCB is good enough.

In the alumina PCB market, there are 75%, 96%, and 99% alumina PCBs. The higher purity, the better properties, and also, the higher costs. PCBONLINE uses 96% alumina to manufacture alumina PCBs. Why? Because this is for a balance between quality and manufacturing cost. From the below table, you will find that 96% and 99% alumina have not so many differences in properties.

Characteristics
96% alumina
99% alumina
Color/Appearance
White/Dense
Beige/Dense
Density
3.6g/cm³
3.9g/cm³
Hardness
1500HV
1700HV
Warpage
≤0.3mm
≤0.2mm
Parallelism
±0.4%
±0.3%
Bending Resistance
3000Kgf/cm²
3500Kgf/cm²
Compressive Strength
25000Kgf/cm²
30000Kgf/cm²
Fracture Toughness
3-4Mpa m1/2
4Mpa m1/2
Thermal Conductivity
25W/(m·K)
31.4W/(m·K)
Voltage Resistance
18KV
18KV
Dielectric Constant [1MHz, 25°C]
9.4
10
Surface Roughness Ra
0.6-0.8μm
0.6-0.8μm
Water Absorption
0%
0%
Sintering Temperature
1689°C
1700°C
Volume Resistivity
/
/
Thermal Shock Resistance
200T°C
220T°C
Thermal Expansion Coefficient [20°C to 300°C]
6-7.5×10ˆ(-6)°C
8-10×10ˆ(-6)°C
Maximum Use Temperature
1400°C
1600°C

Aluminum Nitride PCB

Advantages: higher thermal conductivity and resistance, high hardness, high mechanical strength, higher electrical insulation, strong corrosion-resistance, high biocompatibility, thermal expansion coefficient close to Si

Applications: high-power LEDs, power modules, laser fields

Aluminum nitride PCBs, or AlN PCBs, have 7 to 10 times higher thermal conductivity than alumina PCBs. Why thermal conductivity is mentioned first and so many times? Because it is the most important property to evaluate ceramic PCBs.

Aluminum nitride PCBs are considered to be the most promising ceramic PCBs in the future. Using them, the thermal is dissipated from the ICs and other expensive components immediately. So high-power devices, such as LED ship lights, truck lamps, solar battery modules, large-scale integrated circuits, and so on adopt AlN PCBs as their base plates. Thermal doesn't accumulate in their chips so that the devices work properly at high currents and for long periods.

Another reason that AlN PCBs are welcome for high-power LEDs and power modules is the similar thermal expansion coefficient (4.6×10ˆ-6°C) with semiconductors Si (3.5~4×10ˆ-6°C). The chips of these high-power devices are made of Si. Thanks to the similar thermal expansion coefficients, the chips won't fall off the AlN PCB base plate during thermal deformation.

You can see more characteristics of AlN PCBs from the below table.

Characteristics
Values
Thermal Conductivity
170-320W/(m·K)
Volume Resistivity
>10ˆ13Ω·cm
Dielectric Constant [1MHz, 25°C]
9
Dielectric Loss [1MHz, 25°C]
3.8×10ˆ-4
Dielectric Strength
17KV/mm
Density
≥3.3g/cm³
Surface Roughness Ra
0.3-0.5μm
Thermal Expansion Coefficient [20°C to 300°C]
4.6×10ˆ-6°C
Fracture Toughness
320-330MPa m1/2
Elastic Modulus
310-320GPa
Moh's Hardness
8
Water Absorption
0%
Warpage
0.03-0.05mm
Maximum Use Temperature
2500°C

Silicon Nitride PCB

Advantages: high thermal conductivity, high strength, high fracture toughness

Applications: IGBT modules, vehicle-scale modules, military, aerospace, and aviation modules

Unlike the fragile traditional ceramic materials, under high temperatures, silicon nitride PCBs or Si₃N₄ PCBs have good mechanical strength and fracture toughness. Also, Si₃N₄ PCBs have high thermal conductivity (80+W/mK). Besides, silicon nitride PCBs have matched thermal expansion coefficient with Si.

As you know, IGBT modules for vehicles require much higher thermal conductivity than industrial class IGBTs. And vehicles modules are working in vibrating environments. For safety, the material for cars should also have good impact resistance.

So silicon nitride PCBs are used from vehicle-class modules. For the same reasons, military, aerospace, and aviation modules adopt Si₃N₄ PCBs.

However, the manufacturing of silicon nitride PCBs is not that easy. When the circuit layer is sputtered onto the silicon nitride substrate, the combination is not that stable. In other words, the circuit layer may fall off the ceramic substrate. Thankfully, PCBONLINE has successful manufacturing experience of silicon nitride PCBs for vehicle-class IGBT modules.

The last drawback of silicon nitride PCBs is the lower electrical resistance and insulation than other ceramic PCBs. So when you are designing a Si₃N₄ PCB project, remember this.

Silicon Carbide PCB

Advantages: good strength even at 1400°C, extremely high thermal conductivity and resistance, good semiconductor electrical conductivity, high hardness

Applications: laser fields

Silicon carbon (SiC) is in fact, diamond, but only the different carbon ratios. So silicon carbide PCBs have an extremely high thermal resistance. Working at 1000°C is easy for SiC PCBs. That's why they can be used in laser fields.

SiC has the property Si, so it has close characteristics of semiconductors. In other words, unlike other ceramic PCBs, a SiC PCB doesn't have high insulation.

The manufacturing of SiC PCBs is extremely expensive currently. But in the future, when the manufacturing technology moves forwards, we can expect more applications of silicon carbide PCBs.


And this is a thermal conductivity table of the different ceramic PCB substrates.

Ceramic Substrate Material
Thermal Conductivity
Aluminum Nitride (AIN)
150 – 180 W/mK
Aluminum Oxide(Alumina) (Al₂O₃)
18 – 36 W/mK
Beryllium Oxide (BeO)
184 – 300 W/mK
Boron Nitride (BN)
15 – 600 W/mK
Silicon Carbide (SiC)
70 – 210 W/mK

Part 4: Advantages Properties of Ceramic PCB

    • Good thermal conductivity compared to FR4 PCBs.
    • Very low thermal expansion coefficient.
    • A better choice for high-temperature applications.
    • Better thermal cycling performance.
    • No heavy metal contaminants (PB, Hg, and Cr) in the PCB.
    • High electrical isolation strength.
    • No additional insulation layers are required compared to metal core PCBs.

Part 5: Applications of Ceramic PCBs

Due to the above-mentioned properties, ceramic PCBs are used for applications where strict performance is required. Generally, ceramic PCBs are military applications, space program components, high-power laser applications, etc. But with manufacturing process improvements and reduced costs, they are also entering general industry applications, where more thermal performance is required.

PCBONLINE - High-Quality Ceramic PCB Manufacturer

PCBONLINE is a leading manufacturer of ceramic printed circuit boards. Over the past decades of manufacturing and assembly in ceramic PCBs, we've accumulated rich experience. We provide high-quality alumina PCBs, aluminum nitride PCBs, DOB LEDs, LED COBs, IGBT ceramic substrate boards, 3D alumina products, etc.

Below is the LED COB module that PCBONLINE manufactured for clients. You are welcome to get an online quote or contact by email. Free design and manufacturing plus one-on-one engineering support will bring out the highest quality of your ceramic PCBs.

COB LED