PCB News - Why use ceramic circuit boards

Why use ceramic circuit boards

The general PCB is made of copper foil and the substrate. Due to thermal stress, chemical factors, improper production process and other reasons in its processing, the PCB substrate is prone to bend to varying degrees. Another kind of PCB substrate, namely ceramic circuit board, is greatly superior to the general glass fiber PCB in terms of heat dissipation performance, energization ability, insulation, thermal expansion coefficient, etc. It is widely used in high-power electronic modules, aerospace, and military needs. Electronics and other products.

We usually use PCB adhesives to bond copper foil and substrates. Ceramic circuit boards use bonding methods to combine copper foil and ceramic circuit boards in high-temperature environments. The bonding force is strong, the copper foil does not fall off, the reliability is high, and the temperature is high. It can maintain stable performance even in high humidity environments.
The main material of ceramic circuit board
1. Alumina (Al2O3)

Alumina is the most commonly used substrate material in ceramic circuit boards. It has high strength and chemical stability to many other oxide ceramics in terms of mechanical, thermal, and electrical properties. It has a rich source of raw materials and is suitable for various manufacturing technologies and different shapes.

Ceramic circuit boards are classified into 75 porcelain, 96 porcelain and 99.5 porcelain according to the percentage of alumina. The content of alumina is different, the electrical properties are almost unaffected, but the mechanical properties and thermal conductivity vary greatly. Substrates with low purity have more glass phases and large surface roughness. The higher the purity of the substrate, the more shiny, dense, and low dielectric loss, but the higher the price.
2. Beryllium oxide (BeO)

If ceramic circuit boards have higher thermal conductivity than metal aluminum and require high thermal conductivity, the temperature will drop rapidly when the temperature exceeds 300°C, but its toxicity limits its own development.
3. Aluminum Nitride (AlN)

Aluminum nitride ceramics is based on aluminum nitride powder as the main crystalline phase ceramics. Compared with alumina ceramic circuit boards, it has higher insulation resistance, insulation withstand voltage and low dielectric constant. Its thermal conductivity is 710 times that of Al2O3, and its coefficient of thermal expansion (CTE) almost matches that of silicon wafers, which is very important for high-power semiconductor chips. In the manufacturing process of ceramic circuit boards, the thermal conductivity of AlN is greatly affected by the residual oxygen impurity content, which can reduce the oxygen content and significantly increase the thermal conductivity. The thermal conductivity of the current process production level has reached 170W/(m·K) or more.

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