High-precision chip thermistor and manufacturing method thereof

Abstract

The application provides a high-precision chip thermistor, a pair of back electrodes, a first positive electrode layer, a first resistance layer, a second resistance layer, a second positive electrode layer, a first protective layer, a second protective layer, a side electrode, a back electrode and a third positive electrode layer are formed on a substrate, the high-precision chip thermistor obtained through the above design is covered with a partial covering resistance layer on the upper surface of the first positive electrode, the third positive electrode layer is filled between the protective layer and the side electrode, the resistance value precision of the thermistor is ensured through laser resistance trimming processing, and the resistance value precision can be below ±0.5%.

Description

Technical Field

[0001] This invention relates to the field of resistor manufacturing technology, specifically to a high-precision chip thermistor and its manufacturing method. Background Technology

[0002] A thermistor is a ceramic semiconductor whose resistance changes dramatically with temperature. Due to its sensitivity, accuracy, and stability, thermistors are often the most advantageous sensors in many applications, including temperature measurement, compensation, and control.

[0003] The most important characteristic of a thermistor is its extremely high temperature coefficient of resistance and highly accurate resistance with respect to temperature. Within its operating temperature range, this sensitivity to temperature changes can cause the thermistor's resistance value to vary by tens of millions to one. However, current printed thermistors have an accuracy of ±5%, which can no longer meet the market's demand for high precision in this product. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of this invention is to propose a manufacturing method for a high-precision chip thermistor to solve the problems mentioned in the background section above.

[0005] This invention is achieved through the following technical solution:

[0006] A method for manufacturing a high-precision chip thermistor, the method comprising the following steps:

[0007] S1: Electrode material is printed on the lower surface of the substrate to form a plurality of back electrodes that are spaced apart from each other and not connected to each other. The substrate has a plurality of folded units. On each folded unit, the back electrodes are respectively spaced apart and disposed on opposite sides of the lower surface of the folded unit.

[0008] S2: Electrode material is printed on the upper surface of the substrate and then sintered to form a first positive electrode layer, wherein, on each folding unit, the first positive electrode layer includes a left electrode and a right electrode spaced apart on opposite sides.

[0009] S3: Print a resistive material in the middle of the first positive electrode layer, and then sinter it to form a first resistive layer. One end of the first resistive layer extends to partially cover the upper surface of the left electrode, and the other end of the first resistive layer extends to partially cover the upper surface of the right electrode, and separates the left electrode from the right electrode.

[0010] S4: Print resistive material again on the first resistive layer, and then sinter to form a second resistive layer, the second resistive layer covering the upper surface of the first resistive layer;

[0011] S5: Print electrode material on the second resistive layer and then sinter to form a second positive electrode layer, wherein the second positive electrode layer partially covers the second resistive layer and does not overlap with the first positive electrode layer;

[0012] S6: Print insulating material on the second positive electrode layer and then sinter it to form a first protective layer, wherein the first protective layer completely covers and is fused to the second resistive layer, and extends at both ends to cover the left electrode and the right electrode, respectively.

[0013] S7: Perform laser resistance correction on the product obtained in S6, and stop when the product reaches the set resistance value.

[0014] S8: Print insulating material on the first protective layer and then sinter it to form a second protective layer, wherein the second protective layer completely covers and is fused to the first protective layer;

[0015] S9: Heat-treat the product obtained in S8;

[0016] S10: Print electrode material on the upper surface of the first positive electrode layer that is not covered by the first resistive layer in step S3, and then sinter to form the third positive electrode layer.

[0017] S11: Perform a first separation operation on the product obtained by sintering in S10 to obtain multiple strip-shaped semi-finished products. Vacuum sputter the sides of the strip-shaped semi-finished products to form side electrodes. The side electrodes extend to both ends to connect the first positive electrode layer, the third positive electrode layer and the back electrode.

[0018] S12: Perform a second separation operation on the product obtained in S11 to obtain multiple granular semi-finished products. Each granular semi-finished product corresponds to one folding unit. Electroplating is performed on the granular semi-finished products to obtain a high-precision chip thermistor.

[0019] Furthermore, in step S7, the laser resistance correction includes:

[0020] S701: Measure the resistance value of the product obtained in step S6;

[0021] S702: The measured resistance value is transmitted to the matrix database for comparison and the difference resistance value is calculated;

[0022] S703: Eliminate the difference in resistance by laser repair and return to step S701 until the measured resistance value is equal to the resistance value set in the matrix database, then stop and return to step S701.

[0023] Furthermore, in step S701, the product is placed in an oil bath to maintain a constant temperature, and the resistance of the product is measured using a bridge circuit. After the measurement is completed, the product is cleaned and dried by ultrasonic cleaning.

[0024] Furthermore, in step S7, the laser repair light source is a cold light source or a semi-cold light source;

[0025] Furthermore, in step S12, the side electrodes are sequentially covered with a nickel layer and a tin layer through electroplating, and defective high-precision chip thermistors are eliminated by magnetization.

[0026] Furthermore, in step S6, the sintering temperature is 600° to 700°.

[0027] Furthermore, in step S9, after the product sintered in step S8 is placed at room temperature for 4H to 12H, it is sintered at a temperature range of 220℃ to 280℃.

[0028] Furthermore, the third positive electrode layer is filled between the side electrode and the first protective layer.

[0029] Furthermore, step S13 is included after step S12.

[0030] Step S13: By controlling the ambient temperature range to 24°C to 26°C, the high-precision chip thermistor is tested. After passing the test, it is packaged in a tape and the tape is coiled into a reel.

[0031] A high-precision chip thermistor is manufactured according to any one of the above-mentioned manufacturing methods, wherein the resistance value R of the high-precision chip thermistor is: 5Ω≤R≤2MΩ.

[0032] The high-precision chip thermistor obtained by the above method of the present invention forms a pair of back electrodes, a first positive electrode layer, a first resistive layer, a second resistive layer, a second positive electrode layer, a first protective layer, a second protective layer, a side electrode, a back electrode, and a third positive electrode layer on a substrate. The high-precision chip thermistor obtained by the above design has a partially covered resistive layer on the upper surface of the first front electrode, and the third positive electrode layer is filled between the protective layer and the side electrode. The resistance value accuracy of the thermistor is ensured by laser resistance correction treatment, and the resistance value accuracy can reach below ±0.5%. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the manufacturing method of the present invention.

[0034] Figure 2 This is a schematic diagram of the structure of the high-precision chip thermistor of the present invention;

[0035] Figure 3 This is a schematic diagram of the structure after step S0 in the manufacturing method of the present invention.

[0036] Figure 4 This is a schematic diagram of the structure after step S1 in the manufacturing method of the present invention.

[0037] Figure 5 This is a schematic diagram of the structure after step S2 in the manufacturing method of the present invention.

[0038] Figure 6 This is a schematic diagram of the structure after step S3 in the manufacturing method of the present invention.

[0039] Figure 7 This is a schematic diagram of the structure after step S5 in the manufacturing method of the present invention.

[0040] Figure 8 This is a schematic diagram of the structure after step S10 of the manufacturing method of the present invention.

[0041] The above figures include the following reference numerals:

[0042] 1. Substrate; 1a. Folded line; 1b. Folded grain line; 2. Back electrode; 3. First positive electrode layer; 3a. Left electrode; 3b. Right electrode; 4. First resistive layer; 5. Second resistive layer; 6. Second positive electrode layer; 7. First protective layer; 8. Second protective layer; 9. Third positive electrode layer; 10. Side electrode; 11. Nickel layer; 12. Tin layer. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0044] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0045] S0: Obtain substrate 1, such as Figure 3As shown, a plurality of folded lines 1a extending along a first direction and a plurality of folded lines 1b extending along a second direction are uniformly formed on the upper and lower surfaces of the substrate 1. The first and second directions are approximately perpendicular, and the folded lines 1a and folded lines 1b intersect to form a grid, with each grid constituting a folded unit. Specifically, the first direction is the width direction of the substrate 1, and the second direction is the length direction of the substrate 1. Preferably, the substrate 1 is a ceramic substrate with dimensions of 60mm*70mm.

[0046] S1: As Figure 4 As shown, electrode material is printed on the lower surface of substrate 1 to form a plurality of back electrodes 2 that are spaced apart from each other and not connected to each other. Substrate 1 has a plurality of folding units. On each folding unit, the back electrodes 2 are respectively spaced apart on opposite sides of the lower surface of the folding unit. The back electrodes 2 are parallel to the second direction.

[0047] Preferably, in step S1, the sintering temperature is 800℃~900℃, more preferably 855℃~860℃, and the sintering time is 6min~15min. The electrode material includes, but is not limited to, conductive paste containing metals such as silver.

[0048] S2: As Figure 5 As shown, electrode material is printed on the upper surface of substrate 1. The electrode material is evenly spaced and arrayed and is not connected to each other. Then, it is sintered to form a first positive electrode layer 3. In each folded unit, the first positive electrode layer 3 includes a left electrode 3a and a right electrode 3b spaced apart on opposite sides.

[0049] Preferably, in step S2, the sintering temperature is 800℃~900℃, more preferably 855℃~860℃, and the sintering time is 6min~15min. The electrode material includes, but is not limited to, conductive paste containing metals such as silver.

[0050] S3: As Figure 6 As shown, a resistive material is printed in the middle of the first positive electrode layer 3, and then sintered to form a first resistive layer 4. One end of the first resistive layer 4 extends to partially cover the upper surface of the left electrode 3a, and the other end of the first resistive layer 4 extends to partially cover the upper surface of the right electrode 3b, and separates the left electrode 3a and the right electrode 3b by a gap.

[0051] Preferably, in step S3, the sintering temperature is 800℃~900℃, more preferably 855℃~860℃, and the sintering time is 6min~15min. The resistive material includes, but is not limited to, semiconductor ceramic paste containing metal oxides.

[0052] S4: Print resistive material again on the first resistive layer 4, and then sinter to form the second resistive layer 5, which covers the upper surface of the first resistive layer 4.

[0053] Preferably, in step S4, the sintering temperature is 800℃~900℃, more preferably 855℃~860℃, and the sintering time is 6min~15min. The resistive material includes, but is not limited to, semiconductor ceramic paste containing metal oxides.

[0054] In steps S3 and S4, the semiconductor ceramic paste exhibits a characteristic where its resistance decreases with increasing temperature, and the current market demand is mostly for low resistance values. According to the resistance law R = ρL / S, a larger cross-sectional area of ​​the resistive layer results in a smaller resistance value. Therefore, adding a second resistive layer 5 increases the cross-sectional area of ​​the resistive layer, effectively reducing the resistance value. Furthermore, adding the second resistive layer 5 makes the surface of the resistive layer smoother and the resistance concentration higher, facilitating subsequent laser resistance repair processes.

[0055] S5: As Figure 7 As shown, electrode material is printed on the second resistive layer 5 and then sintered to form the second positive electrode layer 6, wherein the second positive electrode layer 6 partially covers the second resistive layer 5 and does not overlap with the first positive electrode layer 3.

[0056] By designing different sizes of the second positive electrode layer 6 and changing the ratio of the cross-sectional area of ​​the second positive electrode layer 6 to the cross-sectional area of ​​the second resistive layer 5, a reserved resistance value for the required resistance value is obtained. This reserved resistance value will be repaired through a subsequent laser repair process.

[0057] Preferably, in step S5, the sintering temperature is 800℃~900℃, more preferably 855℃~860℃, and the sintering time is 6min~15min. The electrode material includes, but is not limited to, conductive paste containing metals such as silver.

[0058] S6: Insulating material is printed on the second positive electrode layer 6 and then sintered to form a first protective layer 7, wherein the first protective layer 7 completely covers and is fused to the second resistive layer 5, and extends at both ends to cover the left electrode 3a and the right electrode 3b respectively.

[0059] Preferably, in step S6, the sintering temperature is 600℃~700℃, more preferably 555℃~560℃, and the sintering time is 6min~15min. The insulating material includes, but is not limited to, glass paste.

[0060] S7: Perform laser resistance correction on the product obtained in S6, and stop when the product reaches the set resistance value.

[0061] Specifically, in step S7, laser resistance correction includes:

[0062] S701: Measure the resistance value of the product obtained in step S6;

[0063] S702: The measured resistance value is transmitted to the matrix database for comparison and the difference resistance value is calculated;

[0064] S703: Eliminate the difference in resistance by laser repair and return to step S701 until the measured resistance value is equal to the resistance value set in the matrix database, then stop and return to step S701.

[0065] The equipment used to measure the resistance of the product in steps S701 to S703 is as follows: First, the product is placed in a constant temperature oil bath, and then the resistance of the product is measured using a bridge circuit. Second, after the resistance is measured, the product is conveyed to an ultrasonic cleaning and drying machine for cleaning and drying via a conveyor device. Third, after cleaning and drying, the product is conveyed to a laser machine for resistance repair via a conveyor device. Fourth, after the resistance repair is completed, the product is returned to the constant temperature oil bath to confirm whether the resistance value meets the requirements. If the product meets the requirements, step S8 is performed; otherwise, steps S701 to S703 are repeated.

[0066] The process involves adding a temperature control system, heat dissipation unit, temperature controller, and platinum-based temperature sensor to the existing laser cutting machine's internal working area. This structure ensures a constant temperature during product processing. The laser resistance repair light source used in the laser cutting machine is a cold or semi-cold light source (e.g., green or ultraviolet light), thereby reducing the laser's thermal impact and ensuring a constant temperature during product resistance repair. This prevents external temperature from affecting the product's resistance value and thus compromising the accuracy of the laser resistance repair process.

[0067] The matrix database contains the resistance values ​​of the thermistors to be repaired at different temperatures, thus enabling dynamic measurement and resistance repair.

[0068] S8: Insulating material is printed on the first protective layer 7 and then sintered to form the second protective layer 8, wherein the second protective layer 8 completely covers and is fused to the first protective layer 7.

[0069] Preferably, in step S8, the sintering temperature is 220℃~280℃, more preferably 245℃~265℃, and the sintering time is 6min~15min. The insulating material includes, but is not limited to, epoxy resin slurry.

[0070] S9: Heat-treat the product obtained in S8;

[0071] Specifically, in step S9, after the product sintered in step S8 is placed at room temperature for 4 to 12 hours, it is then sintered at a temperature between 220°C and 280°C. Heat treatment can release the internal stress of the product, making its performance more stable. By combining different combinations of heat treatment temperature and time, the sensitivity of the product to temperature sensing and different applicable temperatures can be controlled and adjusted.

[0072] S10: As Figure 8As shown, electrode material is printed on the upper surface of the first positive electrode layer 3 that is not covered by the first resistive layer 4 in step S3, and then sintered to form the third positive electrode layer 9; wherein, the third positive electrode layer 9 fills the space between the side electrode 10 and the first protective layer 7, and the function of the third positive electrode layer 9 is to resist sulfidation and improve the appearance accordingly.

[0073] Preferably, in step S10, the sintering temperature is 220℃~280℃, more preferably 245℃~265℃, and the sintering time is 6min~15min. The insulating material includes, but is not limited to, epoxy resin slurry.

[0074] S11: Perform a first separation operation on the product obtained by sintering in S10 to obtain multiple strip-shaped semi-finished products. Vacuum sputter the sides of the strip-shaped semi-finished products to form side electrodes 10. The side electrodes 10 extend to both ends to connect the first positive electrode layer 3, the third positive electrode layer 9 and the back electrode 2.

[0075] Specifically, in step S10, the first separation operation is a strip folding operation, that is, the substrate 1 is folded into a strip-shaped semi-finished product according to the position of the folding line 1a. Specifically, when the third positive electrode layer 9 covers the first positive electrode layer 3, the side electrode 10 extends to both ends to connect the first positive electrode layer 3, the third positive electrode layer 9 and the back electrode 2.

[0076] S12: Perform a second separation operation on the product obtained in S11 to obtain multiple granular semi-finished products. Each granular semi-finished product corresponds to a folding unit. Electroplating is performed on the granular semi-finished products to obtain a high-precision chip thermistor.

[0077] Specifically, through electroplating, the side electrode 10 is sequentially covered with a nickel layer 11 and a tin layer 12, and defective high-precision chip thermistors are eliminated by magnetization. The nickel layer 11 is used to protect the resistor and to give the resistor good solderability.

[0078] Step S13: By controlling the ambient temperature range to 24°C to 26°C, the high-precision chip thermistor is tested. After passing the test, it is packaged in a tape and the tape is coiled into a reel.

[0079] This embodiment also proposes a high-precision chip thermistor, manufactured using the above process. The resistance R of the high-precision chip thermistor is: 5Ω ≤ R < 2MΩ. Figure 1As shown, the high-precision chip thermistor includes a substrate 1, a pair of back electrodes 2, a first positive electrode layer 3, a first resistive layer 4, a second resistive layer 5, a second positive electrode layer 6, a first protective layer 7, a second protective layer 8, a side electrode 10, and a third positive electrode layer 9. The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method of manufacturing a high-precision chip thermistor, characterized by: The method includes the following steps: S1: Electrode material is printed on the lower surface of the substrate to form a plurality of back electrodes that are spaced apart from each other and not connected to each other. The substrate has a plurality of folded units. On each folded unit, the back electrodes are respectively spaced apart and disposed on opposite sides of the lower surface of the folded unit. S2: Electrode material is printed on the upper surface of the substrate and then sintered to form a first positive electrode layer, wherein, on each folding unit, the first positive electrode layer includes a left electrode and a right electrode spaced apart on opposite sides. S3: Print a resistive material in the middle of the first positive electrode layer, and then sinter it to form a first resistive layer. One end of the first resistive layer extends to partially cover the upper surface of the left electrode, and the other end of the first resistive layer extends to partially cover the upper surface of the right electrode, and separates the left electrode from the right electrode. S4: Print resistive material again on the first resistive layer, and then sinter to form a second resistive layer, the second resistive layer covering the upper surface of the first resistive layer; S5: Print electrode material on the second resistive layer and then sinter to form a second positive electrode layer, wherein the second positive electrode layer partially covers the second resistive layer and does not overlap with the first positive electrode layer; S6: Print insulating material on the second positive electrode layer and then sinter it to form a first protective layer, wherein the first protective layer completely covers and is fused to the second resistive layer, and extends at both ends to cover the left electrode and the right electrode, respectively. S7: Perform laser resistance correction on the product obtained in S6, and stop when the product reaches the set resistance value. S8: Print insulating material on the first protective layer and then sinter it to form a second protective layer, wherein the second protective layer completely covers and is fused to the first protective layer; S9: Heat-treat the product obtained in S8; S10: Print electrode material on the upper surface of the first positive electrode layer that is not covered by the first resistive layer in step S3, and then sinter to form the third positive electrode layer. S11: Perform a first separation operation on the product obtained by sintering in S10 to obtain multiple strip-shaped semi-finished products. Vacuum sputter the sides of the strip-shaped semi-finished products to form side electrodes. The side electrodes extend to both ends to connect the first positive electrode layer, the third positive electrode layer and the back electrode. S12: Perform a second separation operation on the product obtained in S11 to obtain multiple granular semi-finished products. Each granular semi-finished product corresponds to one folding unit. Electroplating is performed on the granular semi-finished products to obtain a high-precision chip thermistor.

2. The method of claim 1, wherein the method is characterized by: In step S7, the laser repair includes: S701: Measure the resistance value of the product obtained in step S6; S702: The measured resistance value is transmitted to the matrix database for comparison and the difference resistance value is calculated; S703: Eliminate the difference in resistance by laser repair and return to step S701 until the measured resistance value is equal to the resistance value set in the matrix database, then stop and return to step S701.

3. The manufacturing method of a high-precision chip thermistor according to claim 2, characterized in that: In step S701, the product is placed in an oil bath to maintain a constant temperature, and the resistance of the product is measured using a bridge circuit. After the measurement is completed, the product is cleaned and dried by ultrasonic cleaning.

4. A method for manufacturing a high-precision chip thermistor according to any one of claims 1 to 3, characterized in that: In step S7, the laser repair light source is a cold light source or a semi-cold light source.

5. The manufacturing method of a high-precision chip thermistor according to claim 1, characterized in that: In step S12, the side electrodes are sequentially covered with nickel and tin layers through electroplating, and defective high-precision chip thermistors are removed by magnetization.

6. The manufacturing method of a high-precision chip thermistor according to claim 1, characterized in that: In step S6, the sintering temperature is 600° to 700°.

7. The method for manufacturing a high-precision chip thermistor according to claim 1, characterized in that: In step S9, the product sintered in step S8 is left at room temperature for 4H to 12H, and then sintered at a temperature of 220℃ to 280℃.

8. The manufacturing method of a high-precision chip thermistor according to claim 1, characterized in that: The third positive electrode layer fills the space between the side electrode and the first protective layer.

9. The method for manufacturing a high-precision chip thermistor according to claim 1, characterized in that: Step S12 is followed by step S13. Step S13: By controlling the ambient temperature range to 24°C to 26°C, the high-precision chip thermistor is tested. After passing the test, it is packaged in a tape and the tape is coiled into a reel.

10. A high-precision chip thermistor, characterized in that: The high-precision chip thermistor manufactured by the manufacturing method according to any one of claims 1 to 9 has a resistance value R of 5Ω ≤ R ≤ 2MΩ.

Images