Miniature low-resistance thick-diaphragm thermosensitive resistor and resistance value adjusting method thereof
By using the structural design of the interdigitated electrode layer and the top electrode layer, the miniaturization, low resistance and low cost problems of traditional thick film thermistors are solved, realizing flexible adjustment of resistance and composite conduction of current paths, reducing product cost and size.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-22
- Publication Date
- 2026-03-13
AI Technical Summary
Traditional thick-film thermistors face challenges in miniaturization, low resistance, and low cost. Resistance adjustment is difficult and the accuracy is low, making it impossible to achieve miniaturization, low resistance, and low cost simultaneously.
The structure is designed to connect the interdigitated electrode layer and the top electrode layer with the thermistor layer. The resistance is adjusted by changing the structure of the interdigitated electrode layer and the projected area of the top electrode layer, forming horizontal and vertical current paths to achieve low resistance and easy adjustment.
This technology enables the miniaturization, low resistance, and low cost of thick-film thermistors, improves the flexibility of resistance adjustment, reduces the amount of precious metals used, and reduces product size.
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Figure CN121662531A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of production technology of thick film thermistors, specifically relating to a miniature low-resistance thick film thermistor and its resistance adjustment method. Background Technology
[0002] As electronic circuits evolve towards integration, miniaturization, and high reliability, electronic components are also moving towards miniaturization. Among these, surface-mount thermistors, as a typical representative of miniaturized electronic components, are widely used in temperature measurement, control, and compensation applications in miniaturized circuits. With the increasingly complex operating environments of electronic circuits, the demand for surface-mount thermistors with superior packaging characteristics, higher reliability, and higher production efficiency is becoming increasingly urgent.
[0003] Surface-mount chip thermistors include thick-film chip thermistors and thin-film chip thermistors. Although thin-film chip thermistors can be miniaturized, they rely on vacuum deposition equipment and precious metal materials. The production process requires maintaining a vacuum environment, resulting in high energy consumption and low production capacity, leading to high manufacturing costs. Moreover, their resistance adjustment capability is weak, with resistance values mostly concentrated in the kΩ range. Their ability to achieve low resistance is insufficient, and they mainly rely on target composition and sputtering parameters for adjustment. The adjustment method is simple and cannot achieve flexible adjustment over a wide range, which greatly limits their application.
[0004] Thick-film thermistors have relatively low production costs and are suitable for widespread adoption. However, traditional thick-film thermistors have the following drawbacks: their resistance adjustment mainly relies on pattern design (aspect ratio / squareness) to change the product size (such as increasing thickness or cross-sectional area) or thermistor paste containing precious metals such as ruthenium. However, the resistance reduction effect of pattern adjustment within a limited space is extremely limited and directly leads to an increase in product size, which contradicts the trend of miniaturization in electronic components. Using precious metal paste not only significantly increases material costs but also affects the paste's B value, requiring complex compositional design to balance electrical parameters, which undoubtedly prolongs the product development cycle. At the same time, the current of traditional thick-film thermistors exhibits a single, long-distance, horizontal flow characteristic. Their resistance value depends on the sheet resistance of the thermistor paste, the aspect ratio and thickness of the two-dimensional planar resistance pattern, and has a small adjustable range. Therefore, traditional thick-film thermistors cannot fundamentally achieve miniaturization, low resistance and low cost simultaneously. Moreover, resistance adjustment is difficult, inaccurate, and lacks flexibility.
[0005] The main reason for the aforementioned defects in traditional thick-film thermistors lies in their structural limitations. Their basic structure is as follows: a thermistor layer (formed by curing thermistor paste) is placed on a ceramic substrate, with two end electrodes connected to the two ends of a rectangular thermistor layer. An encapsulation layer covers the thermistor layer. Based on this structure, the resistance value of a traditional thick-film thermistor can only be determined by the chemical properties and dimensions of the thermistor layer itself. Even if the interdigitated structure from the utility model patent with publication number "CN218782847U" entitled "A Thin-Film NTC Thermistor with Linear Output" is introduced into a traditional thick-film thermistor, it can only solve the above problems to a certain extent, and it is still difficult to simultaneously achieve miniaturization, low resistance, low cost, and easy resistance adjustment. Summary of the Invention
[0006] The purpose of this invention is to provide a miniature, low-resistance, low-cost, and easily adjustable resistance thick-film thermistor and its resistance adjustment method in order to solve the above problems.
[0007] The present invention achieves the above objectives through the following technical solutions: A miniature low-resistivity thick-film thermistor includes a ceramic substrate, a thermistor layer, a first end electrode, and a second end electrode. The rectangular thermistor layer is placed on the ceramic substrate. The first end electrode and the second end electrode are located at opposite ends of the ceramic substrate. The miniature low-resistivity thick-film thermistor also includes a first interdigitated electrode layer, a second interdigitated electrode layer, and a top electrode layer made of an electrically conductive material. The first interdigitated electrode layer and the second interdigitated electrode layer have identical structures, and one or more strip electrodes with reduced width are provided at one end of each layer. These strip electrodes are parallel to each other. The first interdigitated electrode layer and the second interdigitated electrode layer are respectively placed on top of the ceramic substrate, and the first end electrode is... The strip electrodes of the first interdigital electrode layer and the second interdigital electrode layer are arranged alternately. The thermistor layer is placed above the first interdigital electrode layer and the second interdigital electrode layer and covers the strip electrodes of the first interdigital electrode layer and the second interdigital electrode layer and is electrically connected to each other. The rectangular top electrode layer is placed above the thermistor layer and is electrically connected to each other. The center position of the top electrode layer is vertically offset from the center position between the first interdigital electrode layer and the second interdigital electrode layer and is close to the second end electrode. The first interdigital electrode layer is electrically connected to the first end electrode. The second interdigital electrode layer and the top electrode layer are both electrically connected to the second end electrode.
[0008] Preferably, in order to achieve better resistance adjustment, the top electrode layer at least covers a portion of the strip electrodes of the first interdigital electrode layer but does not completely cover all the strip electrodes of the first interdigital electrode layer.
[0009] Preferably, in order to achieve better conductivity, the first interdigital electrode layer, the second interdigital electrode layer and the top electrode layer are all silver or palladium-silver electrode layers.
[0010] Preferably, in order to facilitate assembly and achieve reliable electrical connection, a connecting portion is formed by extending downward below one end of the top electrode layer near the second end electrode. The thickness of the connecting portion is the same as the thickness of the thermistor layer, and the lower part of the connecting portion is electrically connected to the upper part of the second interdigital electrode layer.
[0011] Preferably, for ease of application, the first interdigital electrode layer, the second interdigital electrode layer, the thermistor layer, and the top electrode layer are all placed within an epoxy resin-based encapsulation layer.
[0012] A method for adjusting the resistance of a miniature low-resistance thick-film thermistor, wherein the resistance of the miniature low-resistance thick-film thermistor is adjusted by the following formula. : in, It is the resistance value of the horizontal branch of the micro low-resistance thick film thermistor, namely the lateral current path formed by the first interdigital electrode layer, the second interdigital electrode layer and the thermistor layer. is the resistance value of the vertical current path formed by the second interdigital electrode layer, the thermistor layer, and the top electrode layer in the vertical branch of the miniature low-resistance thick-film thermistor. k is a correction coefficient used to correct the gap between the idealized model and the actual fabrication process. It is determined by the contact resistance between the top electrode layer and the thermistor layer, the contact resistance between the first interdigital electrode layer and the thermistor layer, the contact resistance between the second interdigital electrode layer and the thermistor layer, the edge effect of the suspended end of the strip electrode, and the geometric deviation of each component. 1 is the sheet resistance of the thermistor layer paste; b is the spacing between adjacent strip electrodes of the first and second interdigital electrode layers; N is the number of strip electrodes of the first and second interdigital electrode layers, which is half the total number of strip electrodes of the first and second interdigital electrode layers, or the number of strip electrodes of the first or second interdigital electrode layers; d is the length of the overlapping portion between the strip electrodes of the first and second interdigital electrode layers; h is the thickness of the first interdigital electrode layer, the thickness of the second interdigital electrode layer, and the thickness of the strip electrode; t is the thickness of the thermistor layer; and s is the total projected area of the top electrode layer projected vertically onto the strip electrodes of the first interdigital electrode layer.
[0013] The beneficial effects of this invention are as follows: This invention interconnects the interdigitated electrode layer and the top electrode layer with the thermistor layer as a resistance adjustment component. It not only utilizes the interdigitated electrode layer to achieve low-resistance adjustment of the horizontal current path (horizontal branch) of the thermistor layer, but also utilizes the top electrode layer to achieve low-resistance adjustment of the vertical current path (vertical branch). This significantly enables the realization of low-resistance and resistance adjustment functions in thick-film thermistors through structural adjustments. The achievement of low resistance and resistance adjustment requirements no longer depends on the chemical properties and dimensional variations of the traditional thermistor layer itself. Therefore, it can reduce the amount of precious metals used, thereby lowering costs and reducing product size. Ultimately, it simultaneously achieves miniaturization, low resistance, low cost, and easy resistance adjustment. Attached Figure Description
[0014] Figure 1 This is a three-dimensional structural schematic diagram of the miniature low-resistance thick-film thermistor described in this invention; Figure 2 This is a three-dimensional structural diagram of the ceramic substrate, the first interdigital electrode layer, and the second interdigital electrode layer of the miniature low-resistivity thick film thermistor described in this invention. Figure 3 This is a three-dimensional structural diagram of the ceramic substrate, first interdigitated electrode layer, second interdigitated electrode layer, thermistor layer and top electrode layer of the miniature low-resistivity thick film thermistor described in this invention before assembly. Figure 4 This is a schematic diagram of the three-dimensional structure of the ceramic substrate, the first interdigitated electrode layer, the second interdigitated electrode layer, the thermistor layer and the top electrode layer of the miniature low-resistivity thick film thermistor described in this invention. Figure 5 This is a top view of the first interdigitated electrode layer, the second interdigitated electrode layer, the thermistor layer, and the top electrode layer of the miniature low-resistivity thick-film thermistor described in this invention. Detailed Implementation
[0015] The present invention will be further described below with reference to the accompanying drawings: like Figures 1-5As shown, the miniature low-resistance thick-film thermistor of the present invention includes a ceramic substrate 3, a thermistor layer 10, a first end electrode 1, a second end electrode 4, and a first interdigital electrode layer 5, a second interdigital electrode layer 7, and a top electrode layer 8 made of an electrical conductor material. The rectangular thermistor layer 10 is placed on the ceramic substrate 3. The first end electrode 1 and the second end electrode 4 are located at opposite ends of the ceramic substrate 3. The first interdigital electrode layer 5 and the second interdigital electrode layer 7 have the same structure, and one or more strip electrodes 6 with reduced width are provided at one end of each layer. The multiple strip electrodes 6 are parallel to each other. The first interdigital electrode layer 5 and the second interdigital electrode layer 7 are respectively placed on top of the ceramic substrate 3, and the first interdigital electrode layer 5... The bar electrodes 6 of the first interdigital electrode layer 5 and the second interdigital electrode layer 7 are arranged alternately. The thermistor layer 10 is placed above the first interdigital electrode layer 5 and the second interdigital electrode layer 7 and simultaneously covers the bar electrodes 6 of the first interdigital electrode layer 5 and the second interdigital electrode layer 7 and is electrically connected to each other. The rectangular top electrode layer 8 is placed above the thermistor layer 10 and is electrically connected to each other. The center position of the top electrode layer 8 is vertically offset from the center position of the first interdigital electrode layer 5 and the second interdigital electrode layer 7 and is close to the second end electrode 4. The first interdigital electrode layer 5 is electrically connected to the first end electrode 1, and the second interdigital electrode layer 7 and the top electrode layer 8 are both electrically connected to the second end electrode 4.
[0016] like Figures 1-5 As shown, the present invention also discloses the following more optimized specific structures: To achieve better resistance adjustment, the top electrode layer 8 at least covers a portion of the strip electrodes 6 of the first interdigital electrode layer 5, but does not completely cover all the strip electrodes 6 of the first interdigital electrode layer 5.
[0017] To achieve better conductivity, the first interdigital electrode layer 5, the second interdigital electrode layer 7, and the top electrode layer 8 are all silver or palladium-silver electrode layers.
[0018] To facilitate assembly and achieve reliable electrical connection, a connecting portion 9 is formed by extending downward below one end of the top electrode layer 8 near the second end electrode 4. The thickness of the connecting portion 9 is the same as the thickness of the thermistor layer 10, and the lower part of the connecting portion 9 is electrically connected to the upper part of the second interdigital electrode layer 7.
[0019] For ease of application, the first interdigital electrode layer 5, the second interdigital electrode layer 7, the thermistor layer 10 and the top electrode layer 8 are all placed within the epoxy resin-based encapsulation layer 2.
[0020] illustrate: Figure 1 The image shows that both the first end electrode 1 and the second end electrode 4 are multilayer structures, specifically including a back electrode, end electrode, intermediate electrode and external electrode. These are all conventional end electrode structures of thick film thermistors, and will not be described in detail here.
[0021] like Figures 1-5 As shown, the method for adjusting the resistance of the miniature low-resistance thick-film thermistor of the present invention adjusts the resistance of the miniature low-resistance thick-film thermistor using the following formula. : in, It is the resistance value of the horizontal branch of the micro low-resistance thick film thermistor, namely the lateral current path formed by the first interdigital electrode layer 5, the second interdigital electrode layer 7, and the thermistor layer 10. It is the resistance value of the vertical current path formed by the vertical branch of the miniature low-resistance thick-film thermistor, namely the second interdigital electrode layer 7, the thermistor layer 10 and the top electrode layer 8. K These are correction coefficients used to correct the gap between the idealized model and the actual fabrication process. They are mainly determined by the contact resistance between the top electrode layer 8 and the thermistor layer 10, the contact resistance between the first interdigital electrode layer 5 and the thermistor layer 10, the contact resistance between the second interdigital electrode layer 7 and the thermistor layer 10, the edge effect of the suspended end of the strip electrode 6, and the geometric deviations of each component. t is the sheet resistance of the thermistor layer 10, b is the spacing between adjacent strip electrodes 6 of the first interdigital electrode layer 5 and the second interdigital electrode layer 7, N is the logarithm of the strip electrodes 6 of the first interdigital electrode layer 5 and the second interdigital electrode layer 7, which is half the total number of strip electrodes 6 of the first interdigital electrode layer 5 and the second interdigital electrode layer 7, and also the number of strip electrodes 6 of the first interdigital electrode layer 5 or the number of strip electrodes 6 of the second interdigital electrode layer 7, d is the length of the overlapping portion between the strip electrodes 6 of the first interdigital electrode layer 5 and the strip electrodes 6 of the second interdigital electrode layer 7, h is the thickness of the first interdigital electrode layer 5, the thickness of the second interdigital electrode layer 7, and the thickness of the strip electrodes 6, t is the thickness of the thermistor layer 10, and s is the total projected area of the top electrode layer 8 projected vertically onto the strip electrodes 6 of the first interdigital electrode layer 5, i.e. Figure 5 The area of the projected region A.
[0022] The current in the miniature low-resistance thick-film thermistor described in this invention exhibits a composite conduction characteristic of "horizontal + vertical". That is, the current is conducted through two branches: a horizontal branch formed by the first interdigital electrode layer 5, the second interdigital electrode layer 7, and the thermistor layer 10, and a vertical branch formed by the second interdigital electrode layer 7, the thermistor layer 10, and the top electrode layer 8. The total resistance of the resistor is composed of the parallel connection of the horizontal and vertical branch resistances. In contrast, the current in traditional thick-film thermistors exhibits a single, long-distance, horizontal flow characteristic, and its resistance value depends on the sheet resistance of the thermistor layer paste, the aspect ratio of the two-dimensional planar resistive pattern, and its thickness. Therefore, the structure and resistance adjustment principle of this invention are significantly different from traditional technologies.
[0023] Combination Figures 1-5 The specific resistance adjustment principle of this invention is as follows: (1) The principle of resistance adjustment for horizontal branches is as follows: The first interdigital electrode layer 5 and the second interdigital electrode layer 7 transform the conductive path of the horizontal branch from a long, single current path into multiple parallel short current paths. Each short current path corresponds to a "small resistor," and the total resistance of the horizontal branch is determined by the equivalent resistance of these parallel branches. When the number N of the strip electrodes 6 in the first interdigital electrode layer 5 and the second interdigital electrode layer 7 increases, it is equivalent to an increase in the number of parallel "small resistors," thus increasing the number of conductive paths. According to the law of parallel resistance, the total resistance of the horizontal branch decreases accordingly. When the interdigital spacing b between adjacent strip electrodes 6 in the first interdigital electrode layer 5 and the second interdigital electrode layer 7 decreases, the path length of a single "small resistor" is shortened, thereby reducing the total resistance of the horizontal branch. The length of the overlapping portion between the strip electrodes 6 of the first interdigital electrode layer 5 and the strip electrodes 6 of the second interdigital electrode layer 7 also decreases. When adding resistors, the cross-sectional area of a single "small resistor" can be increased, which also reduces the total resistance of the horizontal branch.
[0024] (2) The principle of resistance adjustment for vertical branches is as follows: Adjusting the total projected area s of the top electrode layer 8 projected vertically onto the strip electrode 6 of the first interdigital electrode layer 5 essentially adjusts the number of parallel equivalent resistances of the vertical branch. The larger s is, the smaller the total resistance of the vertical branch. Adjusting the thickness t of the thermistor layer 10 essentially adjusts the thermistor layer 10 to directly increase the current transmission distance of the vertical branch. The larger t is, the larger the total resistance of the vertical branch.
[0025] In addition, the sheet resistance of the thermistor layer 10 The smaller the value, the smaller the total resistance of both the horizontal and vertical branches.
[0026] (3) The total resistance of the miniature low-resistance thick film thermistor described in this invention is calculated by formula from the total resistance of the horizontal branch and the total resistance of the vertical branch. The smaller the total resistance of the horizontal branch and the total resistance of the vertical branch, the smaller the total resistance of the miniature low-resistance thick film thermistor described in this invention, thereby achieving the requirements of low resistance and resistance adjustment of the entire resistor.
[0027] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the technical solutions of the present invention. Any technical solution that can be implemented based on the above embodiments without creative effort should be considered to fall within the scope of protection of the patent of the present invention.
Claims
1. A miniature low-resistivity thick-film thermistor, comprising a ceramic substrate, a thermistor layer, a first end electrode, and a second end electrode, wherein the rectangular thermistor layer is disposed on the ceramic substrate, and the first end electrode and the second end electrode are respectively located at both ends of the ceramic substrate, characterized in that: The miniature low-resistivity thick-film thermistor further includes a first interdigitated electrode layer, a second interdigitated electrode layer, and a top electrode layer made of an electrically conductive material. The first interdigitated electrode layer and the second interdigitated electrode layer have the same structure and one or more strip electrodes with reduced width are provided at one end. The multiple strip electrodes are parallel to each other. The first interdigitated electrode layer and the second interdigitated electrode layer are respectively placed on the ceramic substrate, and the strip electrodes of the first interdigitated electrode layer and the second interdigitated electrode layer are arranged alternately. The thermistor layer is placed above the first interdigitated electrode layer and the second interdigitated electrode layer, and simultaneously covers the strip electrodes of the first interdigitated electrode layer and the second interdigitated electrode layer and is electrically connected to each other. The rectangular top electrode layer is placed on the thermistor layer and is electrically connected to each other. The center position of the top electrode layer is vertically offset from the center position between the first interdigitated electrode layer and the second interdigitated electrode layer and is close to the second end electrode. The first interdigitated electrode layer is electrically connected to the first end electrode, and the second interdigitated electrode layer and the top electrode layer are both electrically connected to the second end electrode.
2. The miniature low-resistance thick-film thermistor according to claim 1, characterized in that: The top electrode layer at least covers a portion of the strip electrodes of the first interdigital electrode layer but does not completely cover all the strip electrodes of the first interdigital electrode layer.
3. The miniature low-resistance thick-film thermistor according to claim 1, characterized in that: The first interdigitated electrode layer, the second interdigitated electrode layer, and the top electrode layer are all silver or palladium-silver electrode layers.
4. The miniature low-resistance thick-film thermistor according to any one of claims 1-3, characterized in that: The top electrode layer extends downward below one end near the second end electrode to form a connecting portion. The thickness of the connecting portion is the same as the thickness of the thermistor layer. The lower part of the connecting portion is electrically connected to the upper part of the second interdigital electrode layer.
5. The miniature low-resistance thick-film thermistor according to any one of claims 1-3, characterized in that: The first interdigitated electrode layer, the second interdigitated electrode layer, the thermistor layer, and the top electrode layer are all placed within an epoxy resin-based encapsulation layer.
6. A method for adjusting the resistance value of a miniature low-resistance thick-film thermistor as described in any one of claims 1-3, characterized in that: The resistance of the miniature low-resistance thick-film thermistor is adjusted using the following formula. : in, It is the resistance value of the horizontal branch of the micro low-resistance thick film thermistor, namely the lateral current path formed by the first interdigital electrode layer, the second interdigital electrode layer and the thermistor layer. It is the resistance value of the vertical current path formed by the vertical branch of the miniature low-resistance thick-film thermistor, namely the second interdigitated electrode layer, the thermistor layer, and the top electrode layer. K It is a correction factor. denoted as ρ, b is the sheet resistance of the thermistor layer paste, b is the spacing between adjacent strip electrodes of the first and second interdigital electrode layers, N is the number of pairs of strip electrodes of the first and second interdigital electrode layers, d is the length of the overlapping portion between the strip electrodes of the first and second interdigital electrode layers, h is the thickness of the first and second interdigital electrode layers, t is the thickness of the thermistor layer, and s is the total projected area of the top electrode layer vertically projected onto the strip electrodes of the first interdigital electrode layer.