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An Introduction to Alumina PCB in 2021 - All You Want to Know

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Thur, Jun 24, 2021

Alumina PCBs is a type of ceramic PCBs that use aluminum oxide (Al₂O₃) as their substrate. In this post, you will get to know about alumina PCBs, including their characteristics, pros, cons, and applications.

#1: Characteristics of Alumina PCB

Alumina PCBs require high purity Al₂O₃ materials. Alumina has many isomorphic crystals, and alumina PCBs use  α-Al₂O₃ There are 75%, 96%, and 99% alumina substrates. The higher purity, the smoother surface, denser appearance, and lower dielectric loss. And of course, the higher price. To make a balance between quality and costs, PCBONLINE uses 96% alumina substrates for alumina PCB manufacturing.

alumina COB LED

The most important characteristic of an alumina PCB is the thermal conductivity, which ranges from 15W/mK to 50W/mK. When the LED or IC generates a lot of heat, the heat is transferred to the alumina circuit board directly and quickly. Using the alumina PCB, there is no need for an insulating layer as it already achieves good thermal dispassion.

Another property of the alumina PCB is the high thermal withstand. The melting point of the 96% alumina is 1400°C, and for the 99% alumina, it is 1600°C. However, the melting point doesn't stand for the PCB maximum using temperature. If the alumina PCB is multilayer, and the manufacturer uses PP (polypropylene) to connect the two alumina layers, the PCB's overall maximum using temperature is reduced, as PP melts at lower temperatures. If the manufacturer adopts the high-temperature sintering lamination method, the two ceramic layers directly bond, and the thermal withstand is not affected. But in whatever lamination method or manufacturing process, an alumina PCB can work properly at 300°C.

Note
Ag, Ag-Pd, and low-melting-point glass can add to the Al₂O₃ substrate. If we do so, the dielectric constant can be lower, but the temperature for sintering the hybrid ceramic substrate is higher, and so will be the manufacturing costs.

Compared with another ceramic PCB substrate, the beryllium oxide (BeO), alumina is safe. BeO has a much higher thermal conductivity than alumina, but it is toxic. While alumina has high biocompatibility, in other words, safety.

Besides, alumina PCBs have excellent hardness and electrical insulation. For your reference, below is an alumina PCB specifications table made by PCBONLINE.

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

#2: Pros and Cons of Alumina PCB

I find that the above-mentioned characteristics of alumina PCBs are the pros, but I need to list their pros and cons still. To be precise, the pros of the alumina PCBs are:

    • Strong heat resistance and thermal conductivity,
    • High strength and hardness,
    • High electrical insulation, corrosion resistance, and biocompatibility.

In regards to the cons, alumina PCBs have the same cons as all of the ceramic PCBs do:

  • All ceramics are fragile and easy to break,
  • Have higher costs than normal FR4 and metal core PCBs.

No matter what lamination method or manufacturing process the manufacturer adopts, the alumina PCBs are processed with complicated procedures at high temperatures. The below DPC process image shows how the conductive layer is plated onto the ceramic substrate surface at PCBONLINE. From it, you can understand how complex alumina PCB manufacturing is.

ceramic PCB processing flow

#3: What Can Alumina PCBs Be Used for

Alumina is a material having balanced mechanical performance parameters, and it is cheaper than other ceramic materials such as aluminum nitride and BeO. So alumina PCBs are used more commonly than other ceramic PCBs. Its applications include:

  • Automotive products such as engines, sensors, and shock absorbers,
  • LED lighting products,
  • High-power semiconductor modules such as semiconductor refrigerators and electric heaters,
  • Smart power modules such as high-frequency switching power supplies and solid-state relays,
  • High-temperature industrial furnaces,
  • Refrigeration sheets,
  • Telecommunications dedicated exchanges, receiving systems, lasers, and other industrial electronics.

#4: High-Quality Alumina PCB Manufacturing and Assembly

PCBONLINE is a leading advanced PCB manufacturer. The DPC (direct plating copper) technology is used by PCBONLINE to manufacture alumina PCBs. Below is why PCBONLINE is considered a priority alumina PCB manufacturer:

  • Alumina PCB's 3D circuit design can be realized;
  • The thickness of the alumina PCB's conductive layer is arbitrarily customized from 1um to 1mm;
  • PCBONLINE’s alumina PCBs have no oxide layer and have a long shelf life in reducing atmosphere;
  • PCBONLINE can manufacture the alumina PCB to be high-density (HDI) with the minimum 20μm line spacing;
  • PCBONLINE offers one-on-one engineering support (free DFX) to alumina PCB projects.

#5: Showcase of Alumina PCB

Please take a look at these alumina PCBs and products manufactured by PCBONLINE.

Alumina PCB No.1

alumina ceramic pcb

Alumina PCB No.2

ceramic printed circuit board

Alumina Substrate DOB LED

ceramic PCB DOB

Conclusion

This post gives an introduction to alumina PCBs including the characteristics, pros, cons, and applications. Alumina PCBs are replacing aluminum PCBs and copper-based PCBs in high-power applications. If you are looking for ceramic printed circuit boards and assembly, choose PCBONLINE with superior quality!