Thick film sampling resistor and preparation method thereof

Abstract

The invention provides a thick-film sampling resistor and a preparation method thereof, and belongs to the field of thick-film resistor preparation, and the method comprises the following steps: step S1, manufacturing a resistive film layer with required film thickness on a blank ceramic substrate by adopting resistance paste, measuring an initial resistance value Rsr after sintering after high-temperature sintering and curing, and entering step S2; s2, two electrode film layers are arranged at the two ends of the resistive film layer, each electrode film layer comprises an electrode parallel connection section overlapped with the resistive film layer and an electrode series connection section extending outwards from the electrode parallel connection section, and the electrode film layers divide the resistive film layer into a resistor parallel connection section overlapped with the electrode parallel connection section and a resistor series connection section connected between the two resistor parallel connection sections, the length of the resistor parallel section is the same as that of the electrode parallel section, and the length Lcr of the electrode parallel section is determined according to a formula # imgabs0 #; and S3, manufacturing an electrode film layer according to the determined Lcr, sintering and curing, and then manufacturing a protective layer. According to the invention, the resistance value can be adjusted in a lossless manner, and the resistor body structure is prevented from being damaged.

Description

Technical Field

[0001] The present invention belongs to the field of thick film resistor preparation, and particularly relates to a thick film sampling resistor and a preparation method thereof. Background Art

[0002] Thick film sampling resistors generally refer to resistors with a resistance value lower than 1Ω. Because their resistance value is usually very small, they can be used as sampling resistors in high-current sampling circuits, such as current detection, overcurrent protection, power management, etc., and play a very important role in electronic circuits. With the continuous iterative development of military equipment technologies such as aerospace, aviation, weapons, and radar, and the popularization and rise of new energy vehicles, smart grids, power systems, and 5G communications, the market demand for thick film sampling resistors is increasing day by day, and at the same time, higher requirements are continuously put forward for their performance such as power carrying capacity, temperature characteristics, and surge resistance.

[0003] Traditional thick film sampling resistors use screen printing technology to print resistor paste on a ceramic substrate. After sintering and curing, laser trimming technology is used to adjust the resistance value of the product to achieve the target resistance value. Laser trimming technology uses light with a high energy density to locally heat the surface of the resistor body film layer, causing the resistor body material to be instantly vaporized, and then changing the shape of the resistor body, reducing the cross-sectional area of the resistor body through which the current flows, and realizing the function of increasing the resistance value of the product. However, laser trimming technology will cause some irreversible damages and impacts on the product during the production process of thick film sampling resistors, specifically including the following three aspects: First, thermal damage. Because the resistance value of the product is low and the paste used has a large hardness after sintering and curing, a laser with a large power is required for cutting and trimming the resistance. A laser with a large power density is likely to cause excessive heating of the local resistor body material, and even affect the resistor body area outside the laser spot range, resulting in melting, carbonization of the resistor body film layer material, or damage to the structure, generating microcracks. At the same time, it may cause uneven thermal expansion in the local area, and when the degree is serious, the resistor film layer will peel off or crack. Thermal damage will cause resistance value drift in a high-temperature environment, thereby affecting the reliability of the resistor. Second, laser melting residues. Generally, the resistor body film thickness of thick film sampling resistors is relatively thick. When the laser energy is concentrated on the surface of the resistor film layer, the local temperature rises instantaneously, and some materials will be melted and vaporized to form a structure similar to a crater, and molten substances may remain around it. These residues are likely to cause unstable resistance values during the operation of the resistor, thereby affecting the circuit stability. Third, hot spots are easily formed at the edge of the cutting edge when energized. Affected by the laser cutting edge, when energized, the current is not evenly distributed in the resistor body film layer, and the current density at the edge of the cutting edge will be greater than that in other areas, resulting in ineffective dissipation of local heat and forming hot spots. Long-term heat accumulation may cause the resistor to overheat and even result in open circuit failure of the resistor. In addition, laser trimming technology can only achieve one-way adjustment of increasing the resistance value and cannot achieve reduction adjustment. Summary of the Invention

[0004] The object of the present invention is to provide a thick film sampling resistor and a preparation method thereof, which can realize non-destructive adjustment of the resistance value and avoid damage to the resistor body structure.

[0005] The present invention is realized through the following technical solutions: A preparation method of a thick film sampling resistor includes the following steps: Step S1: Use resistor paste to make a resistor film layer with the required film thickness on a blank ceramic substrate, and measure the initial resistance value after high-temperature sintering and curing, then enter step S2; R sr , and enter step S2; Step S2: Set two electrode film layers at both ends of the resistor film layer. The electrode film layer includes an electrode parallel section stacked with the resistor film layer and an electrode series section extending outward from the electrode parallel section. The electrode film layer divides the resistor film layer into a resistor parallel section stacked with the electrode parallel section and a resistor series section connected between the two resistor parallel sections. The length of the resistor parallel section is the same as the length of the electrode parallel section. Among them, according to the formula Determine the length of the electrode parallel section L cr , R t is the set target resistance, R c is the resistance of the electrode series section, R cr is the total resistance of the electrode parallel section and its corresponding resistor parallel section, R r is the resistance of the resistor series section, ρ c is the resistivity of the material of the electrode film layer, L c is the set length of the electrode series section, S c is the cross-sectional area of the current flowing through the electrode film layer, L C is the total length of the electrode film layer, ρ r is the resistivity of the material of the resistor film layer, S r is the cross-sectional area of the current flowing through the resistor film layer, L R is the set total length of the resistor film layer; Step S3: Make the electrode film layer according to the length of the electrode parallel section determined in step S2, and after sintering and curing, make a protective layer.

[0006] Further, in step S3, after sintering and curing, judge the resistance value after sintering Is it within the allowable deviation? If so, proceed with the production of the protective layer; otherwise, return to step S1 to adjust the ratio of the resistor paste to adjust the initial resistance value R sr .

[0007] Furthermore, in step S3, if the resistance value is outside the allowable deviation and greater than the target resistance value R t , then adjust the ratio of the high sheet resistance paste to the low sheet resistance paste in the resistor paste to reduce the proportion of the high sheet resistance paste; otherwise, increase the proportion of the high sheet resistance paste.

[0008] Furthermore, in step S1, use a four-terminal chip automatic measuring machine to measure the initial resistance value after sintering according to the points after sintering and curing R sr .

[0009] Furthermore, in step S3, after determining the length of the electrode parallel section, select a matching electrode stencil from the stencil library to make the electrode film layer, and then perform sintering and curing.

[0010] Furthermore, in step S2, if the length of the electrode parallel section 2 L cr > L R , then return to step S1 to adjust the ratio of the resistor paste to lower the initial resistance value R sr , otherwise, proceed to step S3.

[0011] Furthermore, in step S2, the width of the electrode film layer is the same as the width of the resistor film layer.

[0012] Furthermore, in steps S1 and S3, the temperature used for the high-temperature sintering is 800°C to 900°C.

[0013] Furthermore, the film thickness of the resistor film layer is at least 10μm.

[0014] The present invention is also achieved by the following technical solutions: A thick film sampling resistor prepared based on any one of the above-mentioned thick film sampling resistor preparation methods, comprising a ceramic substrate, a resistor film layer provided on the ceramic substrate, and an electrode film layer. The electrode film layer includes an electrode parallel section superimposed on the resistor film layer and an electrode series section extending outward from the electrode parallel section. The resistor film layer includes two resistor parallel sections respectively superimposed on the two electrode parallel sections and a resistor series section connected between the two resistor parallel sections.

[0015] The present invention has the following beneficial effects: 1. First, a resistor film layer with the required film thickness is fabricated on a blank ceramic substrate and sintered and cured. Secondly, the length of the parallel section of the electrode is calculated according to the series - parallel formula. Then, an electrode film layer is fabricated based on the determined length of the parallel section of the electrode and sintered, thereby obtaining a thick - film sampling resistor with a target resistance value. In this way, the resistance value can be adjusted without loss, maintaining the original structure of the resistor film layer, avoiding the defect of damage to the resistor body caused by the traditional laser cutting technology for adjusting the resistance value, and making the current distribution more uniform when the thick - film sampling resistor is powered on, reducing the risk of hot - spot formation, and making the resistance value more stable and reliable. It can adjust the resistance value downward according to actual needs, making up for the deficiency that the laser - adjusted resistance value can only be adjusted upward. During the production process, if thick - film sampling resistors with different resistance values within a certain range need to be realized, only the resistor film layer needs to be fabricated uniformly, and then the length of the parallel section of the electrode is adjusted by calculation to accurately achieve the target resistance value, without the need to conduct resistance sample trials for products with different resistance values, thus significantly shortening the production cycle. After stacking the electrode film layer with the determined length on the resistor film layer, the production of the protective layer is directly carried out, eliminating the ultrasonic pure - water cleaning and drying processes, effectively avoiding the problem of dust residue caused by laser trimming.

[0016] 2. If the resistance value obtained after the electrode film layer is sintered and cured is not within the allowable deviation, it indicates that the ratio of the resistor paste for fabricating the resistor film layer needs to be adjusted. After adjusting to within the allowable deviation of the resistance value, subsequent mass production can be carried out, thereby shortening the production cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described in detail below with reference to the drawings.

[0018] Figure 1 is a flowchart of the present invention.

[0019] Figure 2 is a schematic structural diagram of the thick - film sampling resistor of the present invention.

[0020] Figure 3 is a schematic diagram of the sintering and curing points of the present invention.

[0021] Among them, 1. Ceramic substrate; 2. Resistor film layer; 21. Resistor parallel section; 22. Resistor series section; 3. Electrode film layer; 31. Electrode parallel section; 32. Electrode series section. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] As Figures 1 to 3As shown in the figure, a thick film sampling resistor ceramic substrate 1, a resistor film layer 2 and an electrode film layer 3 provided on the ceramic substrate 1, a first protective layer, a second protective layer and an end face electrode. The electrode film layer 3 includes an electrode parallel section 31 superimposed on the resistor film layer 2 and an electrode series section 32 extending outward from the electrode parallel section 31. The resistor film layer includes two resistor parallel sections 21 respectively superimposed on the two electrode parallel sections 31 and a resistor series section 22 connected between the two resistor parallel sections 21.

[0023] A method for preparing a thick film sampling resistor includes the following steps: Step S1: Use a resistor paste to make a resistor film layer 2 with a required film thickness on a blank ceramic substrate 1, and measure the initial resistance value after high-temperature sintering and curing. R sr , and enter step S2; Specifically, the film thickness of the resistor film layer 2 is at least 10 μm, the sintering and curing is carried out at a temperature of 850 °C, and a four-terminal chip automatic measuring machine is used to measure the initial resistance value after sintering and curing according to the points after sintering and curing. R sr .

[0024] Step S2: Set two electrode film layers 3 at both ends of the resistor film layer 2. The electrode film layer 3 includes an electrode parallel section 31 superimposed on the resistor film layer 2 and an electrode series section 32 extending outward from the electrode parallel section 31. The electrode film layer 3 divides the resistor film layer 2 into a resistor parallel section 21 superimposed on the electrode parallel section 31 and a resistor series section 22 connected between the two resistor parallel sections 21. The length of the resistor parallel section 21 is the same as the length of the electrode parallel section 31, and the width of the electrode film layer 3 is the same as the width of the resistor film layer 2. Among them, according to the formula Determine the length of the electrode parallel section 31 L cr , R t is the set target resistance, R c is the resistance of the electrode series section 32, R cr is the total resistance of the electrode parallel section 31 and its corresponding resistor parallel section 21, R r is the resistance of the resistor series section 22, ρ c is the resistivity of the material of the electrode film layer 3, L c is the set length of the electrode series section 32, S c is the cross-sectional area of the current flowing through the electrode film layer 3, L C is the total length of the electrode film layer 3, ρ ris the resistivity of the material of the resistive film layer 2, S r is the cross-sectional area of the current flowing through the resistive film layer 2, L R is the total length of the set resistive film layer 2; In this embodiment, R t = 100 mΩ, R sr = 120 mΩ, ρ r = 3×10 -8 Ω·m, L R = 1.2 mm, S r = 12 μm×1.15 mm, ρ c = 1.6×10 -8 Ω·m, L c = 0.91 mm, S c = 8 μm×1.15 mm. Substituting the data into the above formula, L cr = 0.229 mm can be obtained. After judgment, 2 L cr < L R , that is, the resistance value of the resistive film layer 2 is large enough and there is enough space length to stack and fabricate the electrode film layer 3. Therefore, enter step S3. Otherwise, it means that the initial resistance value is too large and the proportion of the resistive paste needs to be adjusted to reduce the initial resistance value. More specifically, if the resistive paste is composed of a high sheet resistance paste and a low sheet resistance paste, the proportion of the high sheet resistance paste is reduced. If the resistive paste is a pure paste, a pure paste with a lower sheet resistance needs to be added for mixing and preparation.

[0025] Step S3: Fabricate the electrode film layer 3 according to the length of the electrode parallel section 31 determined in step S2, and after sintering and curing, fabricate the protective layer; Specifically, after determining the length of the electrode parallel section 31, select a matching electrode screen from the screen library to fabricate the electrode film layer 3, and then sinter and cure it at a high temperature of 850°C. After sintering and curing, use a four-terminal chip automatic measuring machine to measure the resistance value after sintering according to the points after sintering and curing . According to the formula to judge whether the resistance value after sintering is within the allowable deviation. If so, sequentially perform the fabrication of the first-layer protective layer, the second-layer protective layer, the marking, the physical splitting, the end-face electrode fabrication, the physical folding, the electroplating, and the resistance value and appearance screening. If not, when the resistance value is outside the allowable deviation and greater than the target resistance value Rt When the resistance value is outside the allowable deviation and less than the target resistance value, adjust the ratio of the high sheet resistance paste to the low sheet resistance paste in the resistance paste to reduce the proportion of the high sheet resistance paste. R t When the resistance value is outside the allowable deviation and greater than the target resistance value, increase the proportion of the high sheet resistance paste.

[0026] As mentioned above, it is only the preferred embodiment of the present invention, and thus the scope of implementation of the present invention cannot be limited thereby. That is, equivalent changes and modifications made according to the scope of the patent application of the present invention and the content of the specification should still fall within the scope covered by the patent of the present invention.

Claims

1. A method for preparing a thick film sampling resistor, characterized in that: Including the following steps: Step S1: A resistive film layer with a required film thickness is fabricated on a blank ceramic substrate using a resistive paste. After high-temperature sintering and curing, the initial resistance value after sintering is measured, and then proceed to step S2; R sr , and enter step S2; Step S2: Set two electrode film layers at both ends of the resistive film layer. The electrode film layer includes an electrode parallel section superposed with the resistive film layer and an electrode series section extending outward from the electrode parallel section. The electrode film layer divides the resistive film layer into a resistive parallel section superposed with the electrode parallel section and a resistive series section connected between the two resistive parallel sections. The length of the resistive parallel section is the same as that of the electrode parallel section. Among them, according to the formula Determine the length of the electrode parallel section L cr , R t is the set target resistance, R c is the resistance of the electrode series section, R cr is the total resistance of the electrode parallel section and its corresponding resistive parallel section, R r is the resistance of the resistive series section, ρ c is the resistivity of the material of the electrode film layer, L c is the set length of the electrode series section, S c is the cross-sectional area of the current flowing through the electrode film layer, L C is the total length of the electrode film layer, ρ r is the resistivity of the material of the resistive film layer, S r is the cross-sectional area of the current flowing through the resistive film layer, L R is the set total length of the resistive film layer; Step S3: Fabricate the electrode film layer according to the length of the electrode parallel section determined in step S2, and after sintering and curing, fabricate the protective layer.

2. The method for preparing a thick film sampling resistor according to claim 1, wherein: In the step S3, after sintering and curing, judge the resistance value after sintering whether it is within the allowable deviation. If so, proceed to fabricate the protective layer; otherwise, return to step S1 to adjust the proportion of the resistive paste to adjust the initial resistance value R sr .

3. A method for preparing a thick film sampling resistor according to claim 2, characterized in that: In the step S3, if the resistance value is outside the allowable deviation and greater than the target resistance value R t , the ratio of the high sheet resistance paste to the low sheet resistance paste in the resistance paste is adjusted to reduce the proportion of the high sheet resistance paste; otherwise, the proportion of the high sheet resistance paste is increased.

4. A method for preparing a thick film sampling resistor according to claim 1 or 2 or 3, characterized in that: In the step S1, a four-terminal chip automatic measuring machine is used to measure the initial resistance value after sintering according to the points after sintering and curing R sr .

5. A method for preparing a thick film sampling resistor according to claim 1 or 2 or 3, characterized in that: In step S3, after determining the length of the electrode parallel section, select a matching electrode screen from the screen library to fabricate the electrode film layer and then perform sintering and curing.

6. A method for preparing a thick film sampling resistor according to claim 1 or 2 or 3, characterized in that: In the step S2, if the length of the electrode parallel section 2 L cr > L R , then return to step S1 to adjust the ratio of the resistance paste to lower the initial resistance value R sr , otherwise, proceed to step S3.

7. A method for preparing a thick film sampling resistor according to claim 1 or 2 or 3, characterized in that: In step S2, the width of the electrode film layer is the same as that of the resistance film layer.

8. A method for preparing a thick film sampling resistor according to claim 1 or 2 or 3, characterized in that: In step S1 and step S3, the temperature used for the high-temperature sintering is 800°C to 900°C.

9. A method for preparing a thick film sampling resistor according to claim 1 or 2 or 3, wherein: The film thickness of the resistance film layer is at least 10 μm.

10. A thick film sampling resistor prepared by the method for preparing a thick film sampling resistor according to any one of claims 1 to 9, characterized in that: It includes a ceramic substrate, a resistance film layer and an electrode film layer provided on the ceramic substrate. The electrode film layer includes an electrode parallel section superimposed on the resistance film layer and an electrode series section extending outward from the electrode parallel section. The resistance film layer includes two resistance parallel sections respectively superimposed on the two electrode parallel sections and a resistance series section connected between the two resistance parallel sections.

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