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Why do nanofilm pressure sensors exhibit very low temperature drift, excellent long-term stability, and superior overall performance?

2020-08-19

　　The sensing element of a sputtered thin-film pressure sensor is fabricated using vacuum deposition technology. Insulating materials, sensitive strain-resistance materials, and protective materials are deposited onto an elastic stainless steel diaphragm in atomic form, forming atomic-bonded thin films—including an insulating film, a resistive-sensitive-material film, and a protective film—that are integrally fused with the elastic stainless steel diaphragm. Subsequently, through processes such as photolithography and resistance adjustment, a robust and stable Wheatstone bridge is patterned onto the surface of the elastic stainless steel diaphragm. When the medium under measurement exerts pressure on the elastic stainless steel diaphragm, the Wheatstone bridge mounted thereon generates an electrical signal that is directly proportional to the applied pressure. After amplification, adjustment, and other signal-processing steps, and combined with an appropriate structural design, this sensor can be developed into a thin-film pressure sensor or thin-film pressure transmitter suitable for wide-ranging applications across various fields.
　　Currently, commonly available pressure transmitters on the market include several types, such as sputtered thin-film, diffused-silicon, capacitive, ceramic piezoresistive, and metal strain-gauge bonded varieties. Compared with other types of pressure sensors, sputtered nanofilm pressure sensors have the following key features:
　　1. A prominent feature of nano-film pressure sensors is their minimal sensitivity to humidity. This is primarily due to the fact that, prior to depositing the thin film, the sensitive material can undergo compositional modification to achieve an extremely low temperature coefficient of resistance (TCR) inherent in the material itself—down to as low as 0.0002% per degree Celsius. By employing nano-film deposition technology, the modified sensitive material is deposited onto an elastomer substrate, enabling “atomic-level fusion” between the thin film and the elastic diaphragm as well as between adjacent film layers. When such a pressure sensor is fabricated using this approach, its zero-point drift remains below 0.3% even when the temperature varies by 100°C, demonstrating outstanding thermal stability. As a result, the application range of these pressure sensors is greatly expanded, allowing them to operate effectively in ultra-low or ultra-high temperature environments.
　　2. Since the Wheatstone bridge on the sensitive elastomer of the nanofilm pressure sensor is atomically bonded to the diaphragm without any adhesive, it exhibits higher long-term stability and reliability compared to bonded strain gauges.
　　3. The pressure-sensitive elastomeric material is made of high-quality elastic stainless steel, and the pressure connection component welded integrally with it is made of materials such as 316 stainless steel, allowing direct contact with common corrosive media. Therefore, this product can be used for pressure measurement and control in corrosive media and is suitable for deployment in many harsh environments.
　　4. The flexible stainless steel diaphragm is manufactured through precision machining, grinding, annealing, and other processes, ensuring long-term reliability.
　　5. Since the nanofilm pressure sensor is fabricated by laser welding, integrating the sensitive elastomer and the pressure port into a single unit without using an “O”-ring seal or filling with silicone oil, the pressure medium directly acts on the corrosion-resistant stainless steel sensing element. As a result, the product can withstand high-intensity vibrations and shocks with no risk of leakage. It offers accurate measurements and boasts a high frequency response.
　　Nanofilm pressure sensor technology is the most reliable and stable pressure sensing technology, offering excellent overall product performance and making it particularly well-suited for applications in harsh environments—for example, pressure control in engines and hydraulic equipment, precise pressure measurement in industries such as petroleum, chemical processing, rubber, nuclear energy, metallurgy, and power generation, as well as pressure detection and control in military hardware and weaponry. The Swiss company Trafag has conducted long-term comparative tests on the stability of metal-sputtered thin-film pressure sensors, as shown in Figures 1 and 2 below.

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