Mitsubishi Materials has been granted a patent for a method of manufacturing a thermistor chip. The method involves forming a base electrode layer on both surfaces of a thermistor wafer, cutting the wafer to form chips, forming a protective film on the chip’s surface, and applying a cover electrode layer. The electrode portion is made conductive through a heat treatment process. The protective film is made of silicon oxide and is formed by immersing the chip in a reaction solution. GlobalData’s report on Mitsubishi Materials gives a 360-degree view of the company including its patenting strategy. Buy the report here.
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Method of manufacturing a thermistor with protective film and electrodes
A recently granted patent (Publication Number: US11763967B2) describes a method for manufacturing a thermistor with improved performance and durability. The method involves several steps to create a thermistor chip with a columnar shape, a protective film, and electrode portions on both ends.
The first step is the formation of a base electrode layer by applying and sintering a conductive paste on both surfaces of a thermistor wafer made of a thermistor material. This conductive paste can be a glass-filled metal paste containing metal powder and glass powder. The thermistor wafer is then cut to form individual thermistor chips with the base electrode layer.
Next, a protective film made of a silicon oxide is formed on the entire surface of each thermistor chip with the base electrode layer. This protective film is created by immersing the chip in a reaction solution containing a silicon alkoxide, water, an organic solvent, and an alkali. The silicon oxide is then precipitated on the chip's surface through hydrolysis and a polycondensation reaction of the silicon alkoxide.
Afterward, a cover electrode layer is formed on the end surface of each thermistor chip with the base electrode layer. This is achieved by applying and sintering a conductive paste, which can also be a glass-filled metal paste containing metal powder and glass powder, on the surface of the protective film.
Finally, a conduction heat treatment is performed to ensure electrical conductivity between the base electrode layer and the cover electrode layer. This heat treatment further enhances the performance and durability of the thermistor.
Additional steps in the method include chamfering the thermistor chip after the cutting process and carrying out the protective film forming step after the chamfering.
Overall, this patented method offers a comprehensive approach to manufacturing thermistors with improved performance and durability. The use of a protective film made of a silicon oxide and the specific conductive pastes contribute to the overall quality and functionality of the thermistors produced using this method.