FOLYSKY（WuHan） LTD.
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FOLYSKY（WuHan） LTD.
According to the process, the humidity sensor can be divided into integrated sensors, thin film sensors, thick film sensors. Integrated sensors are manufactured using standard production silicon-based semiconductor IC process technology, and typically also integrate part of the circuit used for the initial processing of the signal under test on the same chip. Thin film sensors and thick film sensors are different.
Whether it is a thin film sensor or a thick film sensor, the circuit is printed directly on the substrate, but the method of processing is different, the thick film sensor is made of the corresponding slurry, coated on the substrate, the substrate is usually made of alumina ceramic substrate, and then heat treatment, so that the thick film is formed. Thin film sensors are formed by depositing a thin film of the corresponding sensitive material on the substrate. When the hybrid process is used, part of the circuit can also be printed on the substrate.
There are many advantages of using ceramic substrate, we have to speak from the advantages of ceramic substrate. Ceramic substrate mainly has the following advantages:
1, higher thermal conductivity: the thermal conductivity of the traditional aluminum-based circuit board MCPCB is 1 ~ 2W/mk, the thermal conductivity of copper itself is 383.8W/m.K, but the thermal conductivity of the insulation layer is only about 1.0W/m.K, and the better can reach 1.8W/m.K. The thermal conductivity of alumina ceramics is 15 ~ 35 W/m.k, the thermal conductivity of aluminum nitride ceramics is 170 ~ 230 W/m.k, and the thermal conductivity of copper substrate is 2W/(m*K). Aluminum/copper-based circuit board: its own thermic conductivity is high, but there is an insulating layer on the aluminum/copper-based circuit board, resulting in a decrease in the thermal conductivity of the entire board. We can replace the insulation layer with a ceramic base, with aluminum/copper as the substrate and a ceramic base as the insulation layer.
2, more matched thermal expansion coefficient: humidity sensor operating temperature span is very large, in the high temperature and low temperature environment, the coefficient of thermal expansion between the material if not matched, it will cause the line to fall off, and then the entire sensor will be scrapped, ceramic substrate has a more matched thermal expansion coefficient of humidity sensor, can have relatively good stability.
3, good insulation: breakdown resistance voltage of up to 20KV/mm, can prevent any damage caused by short circuit, the protection of sensitive components can be extreme.
4, small dielectric loss: high-frequency circuit can be designed and assembled, the dielectric loss is very small, and the sensor output signal can reach the lossless level.
5, does not contain organic ingredients: corrosion resistance, acid and alkali resistance, high temperature resistance, these are the guarantee that the humidity sensor can operate in harsh environments.
The above list is only for the humidity sensor more helpful features, in fact, there are many advantages of ceramic substrate. The biggest difficulty of the humidity sensor is to operate at high or low temperatures, and the ceramic substrate is just right to solve these problems.
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