How to make pressure sensor? What should the pressure sensor pay attention to in the processing details? The production steps of the pressure sensor are introduced in detail. Let's take a look.
The main process flow of a typical sputtered thin film pressure sensor, in which the production of pressure-sensitive components is a key process, including four processes such as elastomer manufacturing, grinding and polishing, film coating, and ion beam etching.
Elastomer design and manufacturing: refers to the structural design and mechanical processing of elastomer steel cups, and stress-relief heat treatment. This link will determine the basic parameters of the elastomer diaphragm and basically determine the input-output relationship of the sputtered film pressure sensor. The modeling and calculation process of elastomers is very important and will be explained in the next section.
Grinding and polishing: Grind and polish qualified elastomer steel cups to make the surface meet the requirements of smoothness, and then make further thinning treatment.
Coating: Alternate with etching. Using ion beam sputtering deposition technology, a multilayer film with strong adhesion, uniform film layer, dense and stable performance is manufactured on the surface of the metal elastomer.
Etching: Using semiconductor photolithography and etching methods, or studying the use of ion beam etching to etch the resistive film into the resistive stripe pattern of Wheatstone bridge; etch the lead film into the lead electrode.
Bridge fine-tuning: A thin-film resistor is used to compensate the bridge arm resistance of the Wheatstone bridge, and the output of the sensor is adjusted to the design range (that is, the ideal zero point).
Welding: Laser welding or electron beam welding process is used to weld qualified chips, brackets, shells, etc. to the base with pressure test port. Welding pressure sensitive components and pressure joints is a key process. Welding by high-power laser welding machine or electron beam welding machine, the welding seam depth can reach 2.2mm. A large number of welding process tests have shown that the selection of different welding process parameters can effectively eliminate the adverse effects of welding stress on the sensor. The elastomer is welded to the base, bracket, and shell.
In-lead encapsulation: Gold wire ball welding or pressure welding process is used, and the welding chip lead is connected to the bracket from the electrode of the thin film strain resistance.
Stability treatment: Conduct various environmental tests on the sensor, and repeatedly measure its output to assess its stability.
Digital correction: After stability processing, the sensor performs temperature compensation, nonlinearity and other zero-point compensation according to various parameters designed in advance.
Overall packaging: The compensated sensor sensitive chip is subjected to surface treatment such as spraying, the purpose is to prevent the film layer and circuit of the sensor sensitive chip from being affected by the environment.
Aging and testing: Perform high and low temperature, electrical stress aging tests and various reliability environmental tests such as vibration, impact, fatigue, damp heat, and thermal vacuum on the packaged sensors.