The Research Of Polyimide Capacitive Humidity Sensor

Polymer capacitive humidity sensor is concerned widespread in recent years,it has ample room to development, this kind of humidity sensor has a large market in China, but the domestic products are not many, because there exists a linear differential, wet stagnation, poor stability, the short comings of the performance, with advantages of the same type of foreign products, most of the market are occupied by them.The purpose of this paper is to research a type of commercialization of capacitive humidity sensor, Because most of the experiment content were completed in the company, combined with the basic condition of the company, we design a complete process line, work summed up as follows:First, research insulating layer:take advantage of sol-gel (Sol-Gel) technology, finally use TEOS as the main raw material, with the role of the silane coupling agent, we successfully made a layer of silane insulating film on the surface of steel-18played with good adhesive properties of stainless steel collective and a sense of the wet film, compared with the humidity sensor without the insulating film obtained, the yield of components increase from50%to95%,this is an innovative point of this paper.Second, the wet film of organic polymer:the wet film is the core of the humidity sensor, around a sense of wet polymer polyimide (PI) in this experimental study, the main study the synthesis of principles of polyimide, change to a different dianhydride and diamine, to change the production process, such as temperature-programmed process, the polyamide acid process, and more from the product performance, and ultimately determine the sense of wet film of polymers synthesized types of raw materials and synthesis techniques, obtained by the humidity the sensitivity of the components can be achieved0.408PF/RH%response time of less than5S, the maximum hysteresis8.15%RH. Lag for further reducing the hysteresis, add a layer of protective film in the sense of wet membrane, cellulose acetate butyrate, produced after the success of a certain extent to reduce the hysteresis, the hysteresis is7%RH.In the same test conditions, the homemade product performance has reached the model of HS1101from United States MEAS Co., LTD.Thirdly,The development of humidity components manufacturing process:in combination with actual conditions, and on the basis of the design for mass production process, the stainless steel plate with for down electrode, using sol-gel technique was used to gel insulating layer, after the preparation of wet film, the screen printing technology was used on the up electrode, so realize the large-scale production of humidity capacitance components.The last part of the paper summaried the improvement place of product, laid solid foundation for the further enhance of the product performance.