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What is the experience of using a humidity sensor with a ceramic substrate?

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According to the process, the humidity sensor can be divided into an integrated sensor, a thin film sensor, and a thick film sensor. Integrated sensors are fabricated using standard silicon-based semiconductor integrated circuit process technology, and some of the circuitry used to initially process the signal under test is also integrated on the same chip. Thin film sensors and thick film sensors are different.

Both the thin film sensor and the thick film sensor directly print the circuit on the substrate, but the processing method is different. The thick film sensor is made by coating the substrate with the corresponding slurry, and the substrate is usually made of alumina. The ceramic substrate is then heat treated to form a thick film. The thin film sensor is formed by a film of a corresponding sensitive material deposited on the substrate. When a mixing process is used, part of the circuit can also be printed on the substrate.

There are many benefits to using a ceramic substrate, and we have to look at the advantages of ceramic substrates. Ceramic substrates have the following main advantages:

1. Higher thermal conductivity: The thermal conductivity of the traditional aluminum-based circuit board MCPCB is 1~2W/mk, and the thermal conductivity of copper itself is 383.8W/mK, but the thermal conductivity of the insulating layer is only about 1.0W/mK. A little better can reach 1.8W/mK. The thermal conductivity of alumina ceramics: 15 ~ 35 W / mk, the thermal conductivity of aluminum nitride ceramics: 170 ~ 230 W / mk, the thermal conductivity of copper substrates is 2W / (m * K), aluminum / copper base Circuit board: The aluminum itself has high thermal conductivity, but there is an insulating layer on the aluminum/copper-based circuit board, which causes the thermal conductivity of the whole board to decrease. We can replace the insulating layer with a ceramic base, with aluminum/copper as the substrate and ceramic as the insulating layer.

2. More matching thermal expansion coefficient: The operating temperature span of the humidity sensor is very large. In the high temperature and low temperature environment, if the coefficient of thermal expansion between the materials does not match, the line will fall off, and then the entire sensor will be scrapped. Ceramic The substrate has a coefficient of thermal expansion that more closely matches the humidity sensor and can have relatively good stability.

3, good insulation: breakdown voltage up to 20KV / mm, can prevent damage caused by any short circuit, the protection of sensitive components can be done to the extreme.

4, the dielectric loss is small: the design and assembly of the high-frequency circuit can be carried out, the dielectric loss is very small, and the signal output by the sensor can reach the lossless level.

5, does not contain organic components: corrosion resistance, acid and alkali resistance, high temperature resistance, these are guaranteed by the humidity sensor can operate in harsh environments.

The above list is only useful for the humidity sensor. In fact, the ceramic substrate has many advantages. The biggest difficulty with humidity sensors today is that they operate at high or low temperatures, and ceramic substrates are just right to solve these problems.

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