High-power thick-film resistor
By employing a structural design of substrate, resistive layer, front electrode and back electrode in high-power thick film resistors, and setting L-shaped laser-cut adjustable grooves on both sides of the resistive layer, the problems of unstable resistance value and poor heat dissipation are solved, and more stable electrical performance and high-temperature performance are achieved.
Patent Information
- Application Number
- CN202423321835.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-30
- Publication Date
- 2026-02-17
- Estimated Expiration
- 2034-12-30
AI Technical Summary
Existing high-power thick film resistors suffer from poor resistance stability, power limitation, poor heat dissipation, and insufficient stability during manufacturing. This is mainly due to the fact that fixing the front electrode limits the effective length of the resistive layer, and the diffusion of silver metal leads to unstable resistance values.
The structure consists of a substrate, a resistive layer, two front electrodes, and two back electrodes. The resistive layer is mounted on the front side of the substrate, and the front electrodes cover the ends of the resistive layer. The density of the resistive layer is optimized through two sintering processes, and L-shaped laser-cut adjustable grooves are set on both sides of the resistive layer to lengthen the current path.
It improves the electrical properties and physical strength of the resistor, enhances its power handling capacity, ensures the stability of the resistance value and its high-temperature resistance, reduces silver diffusion, and optimizes its electrical properties and mechanical strength.
Smart Images
Figure CN223927147U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to a resistor, and more particularly to a high-power thick-film resistor. Background Technology
[0002] There are some problems in the manufacturing process of high-power thick film resistors, such as poor resistance value stability, power limitation, poor heat dissipation, and insufficient stability performance.
[0003] The existing manufacturing process for high-power thick-film resistors is as follows: back conductor (back electrode) printing → front conductor (front electrode) printing → conductor layer sintering → resistor (resistor layer) printing → resistor layer sintering → glass protective layer printing → glass protective layer sintering → laser finishing → resin protective layer printing → character printing → hardening → automatic striping → vacuum coating → granulation → terminal fabrication. As can be seen from the flowchart above, most resistors use a method of printing the front electrode first, followed by printing the resistor itself. That is, in this resistor structure, the two ends of the resistor layer cover the front electrodes at both ends. This structure limits the effective length of the resistor layer, mainly because the fixed front electrode prevents further elongation of the resistor layer, thus limiting its effective length. It also easily causes silver diffusion in the conductor layer (front electrode). During resistor (resistor layer) sintering, the conductor (front) is also sintered again. Since the main component of the front electrode is silver, secondary sintering easily causes silver diffusion. This results in poor resistance stability in the operating environment. Therefore, solving these technical problems is a direction that those skilled in the art need to strive towards. Summary of the Invention
[0004] The purpose of this invention is to provide a high-power thick-film resistor. By using this structure, the electrical performance and physical strength of the resistor can be effectively improved, the power handling capacity and the resistance value can be increased, and the high-temperature resistance performance is better.
[0005] To achieve the above objectives, the technical solution adopted by this utility model is: a high-power thick-film resistor, comprising a substrate, a resistive layer, two front electrodes, and two back electrodes, wherein the two back electrodes are symmetrically disposed on both sides of the back surface of the substrate.
[0006] The resistive layer is mounted on the front side of the substrate, and both ends of the resistive layer are disposed close to the two ends of the front side of the substrate.
[0007] Two front electrodes are symmetrically mounted at both ends of the front side of the substrate. The outer end of each front electrode is disposed on the front side of the substrate at the end of the resistive layer, and the inner end of each front electrode extends inward and covers the front side of the end of the resistive layer.
[0008] The above technical solution also includes two end electrodes, which are disposed at both ends of the substrate, and the two ends of each end electrode respectively cover the front electrode and the back electrode on one side.
[0009] The above technical solution also includes a first protective layer, which covers the front side of the resistive layer, and the two ends of the first protective layer respectively cover a portion of the front side of the two front electrodes;
[0010] The first protective layer is further covered by a second protective layer, with both ends of the second protective layer covering a portion of the front surface of the front electrode.
[0011] In the above technical solution, the first protective layer is a glass protective layer, and the second protective layer is a resin protective layer.
[0012] In the above technical solution, the two front electrodes are disposed at both ends of the length direction of the resistive layer;
[0013] The resistive layer has a laser-cut resistance adjustment groove on each side in the width direction.
[0014] In the above technical solution, one of the laser-cut trimmed grooves is disposed near one of the front electrodes, and the other laser-cut trimmed groove is disposed near another of the front electrodes.
[0015] In the above technical solution, the laser-cut resistance adjustment groove has an L-shaped structure, and the L-shaped openings of the two laser-cut resistance adjustment grooves are in opposite directions.
[0016] In the above technical solution, the L-shaped openings of the two laser-cut resistance adjustment grooves are arranged opposite each other.
[0017] In the above technical solution, the two laser-cut resistivity adjustment grooves have a first spacing in the length direction of the resistive layer, and the two laser-cut resistivity adjustment grooves have a second spacing in the width direction of the resistive layer.
[0018] Due to the application of the above technical solution, this utility model has the following advantages compared with the prior art:
[0019] 1. In this utility model, the two ends of the resistive layer are close to the two ends of the substrate, and the inner end of the front electrode covers the front end of the resistive layer. In this structure, the length of the resistive layer can be effectively stretched to the limit, thereby effectively improving the electrical performance of the resistor, improving the power handling capacity and the more stable resistance value.
[0020] 2. In this utility model, since the front electrode is covered on the resistive layer, the resistive layer is printed, sintered and cured first, and then the front electrode is printed and cured. This allows the resistive layer to be sintered a second time, making the resistive layer more compact. The second sintering can release the residual stress in the resistive layer, which can not only improve the physical strength of the resistor, but also effectively improve the electrical performance of the resistor, improve the power handling capacity and the more stable resistance value, and have better high temperature resistance.
[0021] 3. In this invention, the front electrode covers the front end of the resistive layer, which can protect the contact area at the end of the resistive layer and make the resistance performance more stable;
[0022] 4. In this utility model, the front electrode can reduce the number of high-temperature sintering times, reduce the diffusion of silver in the material used for the front electrode, and improve the stability of the resistance value in the working environment.
[0023] 5. In this utility model, L-shaped laser-cut grooves are respectively arranged oppositely on both sides of the width direction of the resistor layer, which can effectively increase the effective length of the resistor, lengthen the current path, and improve the stability of the resistor's electrical performance. Attached Figure Description
[0024] Figure 1 This is a schematic diagram of the structure in Embodiment 1 of this utility model;
[0025] Figure 2a This is a schematic diagram of the L-shaped blade in the comparative example;
[0026] Figure 2b This is a schematic diagram of the IL knife in the comparative example;
[0027] Figure 2c This is a schematic diagram of the structure of knife I in the comparative example;
[0028] Figure 2d This is a schematic diagram of the Z-knife structure in the comparative example;
[0029] Figure 3a This is a schematic diagram of the microcrack and current flow direction in the "I"-shaped knife-shaped structure in the comparative example;
[0030] Figure 3b This is a schematic diagram of the structure of the "L"-shaped knife-shaped microcrack and the direction of current flow in the comparative example;
[0031] Figure 4 This is a schematic diagram of the structure of the laser-cut resistance adjustment groove disposed on the resistor layer in Embodiment 1 of this utility model.
[0032] Wherein: 1. Substrate; 2. Resistive layer; 3. Front electrode; 4. Back electrode; 5. Upper part; 6. Lower part; 7. End electrode; 8. Vacuum coating layer; 9. Electroplating layer; 10. First protective layer; 11. Second protective layer; 12. Laser-cut resistance adjustment groove; 13. Horizontal groove; 14. Vertical groove; 101. Microcrack; 102. Current flow direction; 201. Resistance adjustment groove; 202. Resistive layer. Detailed Implementation
[0033] The present invention will be further described below with reference to the accompanying drawings and embodiments:
[0034] Example 1: See Figures 1-4 As shown, a high-power thick-film resistor includes a substrate 1, a resistive layer 2, two front electrodes 3, and two back electrodes 4. The two back electrodes 4 are symmetrically disposed on both sides of the back surface of the substrate 1.
[0035] The resistive layer 2 is mounted on the front side of the substrate 1, and both ends of the resistive layer 2 are disposed close to the two ends of the front side of the substrate 1.
[0036] Two front electrodes 3 are symmetrically mounted at both ends of the front side of the substrate 1. The outer end of each front electrode 3 is disposed on the front side of the substrate 1 at the end of the resistive layer 2, and the inner end of each front electrode 3 extends inward and covers the front side of the end of the resistive layer 2.
[0037] In this embodiment, taking the illustrated direction as an example, a resistive layer and a front electrode are disposed on the top surface of the substrate, and a back electrode is disposed on the bottom surface of the substrate. The outer bottom surface of the front electrode is connected to the top end of the substrate, and the inner bottom surface of the front electrode abuts against the top surface of the resistive layer. The end of the resistive layer is in contact with the sidewall of the front electrode. The front electrode has an L-shaped structure, including an upper part 5 and a lower part 6. The upper part is longer than the lower part. The lower part is disposed on the outer end of the bottom surface of the upper part, and its bottom surface is connected to the top surface of the substrate. The inner bottom surface of the upper part is connected to the top end of the resistive layer, and the end face of the resistive layer is connected to the inner sidewall of the lower part. This method allows the resistive layer to be stretched as much as possible, reaching its maximum length, thereby effectively improving the electrical performance of the resistor, increasing its power handling capability, and providing a more stable resistance value.
[0038] In this embodiment, the manufacturing process of the resistor is as follows:
[0039] 1. Preparation of the substrate; wherein, in this embodiment, the substrate may be made of ceramic, such as an alumina ceramic substrate;
[0040] 2. Printing of the back electrode: Print the back electrode on both ends of the back side of the substrate;
[0041] 3. Sintering of the back electrode: The substrate with the back electrode printed on it is sintered and cured at 850°C (of course, the sintering step can be omitted. After the back electrode is printed, it is dried and the resistive layer is printed directly after drying).
[0042] 4. Printing of the resistive layer: The resistive layer is printed on the front side of the substrate, and there will be a certain gap between the two ends of the resistive layer and the two ends of the substrate.
[0043] 5. Sintering of the resistive layer: The substrate with the printed resistive layer is sintered and cured at 850℃.
[0044] 6. Printing of the front electrode: The front electrode is printed on both sides of the front side of the substrate, and part of the front electrode is also printed and covered on the front side of the end of the resistive layer.
[0045] 7. Sintering of the front electrode: The substrate with the front electrode printed on it is sintered and solidified at 850°C.
[0046] 8. Proceed with other subsequent processes.
[0047] In this embodiment, the main material for both the front and back electrodes is silver. The front electrode only requires one high-temperature sintering process, which reduces silver diffusion (reducing silver diffusion optimizes electrical performance and mechanical strength), resulting in better contact between the front electrode and the resistive layer and improving the stability of the resistor's value during operation. Simultaneously, the resistive layer requires two high-temperature sintering processes, which reduces stress in the resistive layer, releases residual stress, and thus improves the physical strength of the resistor. Furthermore, as the structure with the greatest impact on resistance, complete and thorough sintering of the resistive layer contributes to long-term resistance stability. The preferred sintering time for the resistive layer and the front electrode is generally 30 to 40 minutes.
[0048] See Figure 1 As shown, it also includes two end electrodes 7, which are disposed at both ends of the substrate 1, and the two ends of each end electrode 7 respectively cover the front electrode 3 and the back electrode 4 on one side.
[0049] End electrodes are used to connect the front and back electrodes at each end of the substrate. The end electrodes include a vacuum-deposited layer 8 and an electroplated layer 9 covering the outside of the vacuum-deposited layer 8. The two ends of the vacuum-deposited layer cover the front and back electrodes, while the middle covers the end of the substrate. The electroplated layer completely covers the outside of the vacuum-deposited layer, and the back of the electroplated layer also completely covers the back electrode that is not completely covered by the vacuum-deposited layer. Of course, the end electrode has a common structure and is the same as the end electrode structure in the prior art.
[0050] See Figure 1 As shown, it also includes a first protective layer 10, which covers the front side of the resistive layer 2, and the two ends of the first protective layer 10 respectively cover a portion of the front side of the two front electrodes 3.
[0051] The first protective layer 10 is further covered by a second protective layer 11, with both ends of the second protective layer 11 covering a portion of the front surface of the front electrode 3.
[0052] The first protective layer is a glass protective layer, and the second protective layer is a resin protective layer.
[0053] The first and second protective layers protect and insulate the resistor layer. The resin protective layer uses a high-temperature resistant resin with excellent heat dissipation to enhance the resistor's high-temperature resistance and heat dissipation capabilities, increasing its stability under high-temperature conditions. The resin protective layer typically uses a resin material with a low coefficient of thermal expansion.
[0054] After the front electrode is sintered, a first protective layer is printed. After the first protective layer is printed, it is sintered and cured. After the first protective layer is sintered and cured, laser cutting (i.e., laser trimming) is performed. After the laser trimming is completed, a second protective layer is printed and hardened. Then, strip arrangement, vacuum coating, folding, and terminal fabrication (electroplated on the outside of the vacuum coating layer, i.e., electroplating layer fabrication) are carried out.
[0055] In this process, one end of the vacuum-deposited layer covers the outer surface of the front electrode that is not covered by the first and second protective layers, the middle part covers the end face of the substrate, and the other end covers part of the back electrode. The front end of the vacuum-deposited layer abuts against the outer surface of the second protective layer, the inner end of the front end of the electroplated layer abuts against the outer surface of the second protective layer, and the back end of the electroplated layer completely covers the outside of the back electrode and partially covers the back of the substrate, so that the inner end of the back electrode is not exposed.
[0056] See Figure 4 As shown, the two front electrodes 3 are disposed at both ends of the length direction of the resistive layer 2;
[0057] The resistive layer 2 has a laser-cut trimming groove 12 on each side in the width direction. Taking the illustrated example, two front electrodes are set on the left and right sides of the resistive layer, and two laser-cut trimming grooves are set on the top and bottom of the resistive layer.
[0058] In this embodiment, in order to achieve the required resistance value and shape, laser trimming is performed, that is, the resistive layer is precisely cut and adjusted by laser. The laser-cut trimming groove is made by laser cutting.
[0059] See Figure 4As shown, one of the laser-cut trimmed grooves 12 is disposed near one of the front electrodes 3, and the other laser-cut trimmed groove 12 is disposed near another of the front electrodes 3.
[0060] The laser-cut resistance adjustment groove 12 has an L-shaped structure, and the two laser-cut resistance adjustment grooves 12 have opposite L-shaped opening directions.
[0061] The L-shaped openings of the two laser-cut resistance adjustment grooves 12 are arranged opposite each other.
[0062] As a comparative example, commonly used cutting blade types include L-shaped blades (such as...). Figure 2a As shown), IL knife (as shown) Figure 2b As shown), I knife (as shown) Figure 2c (as shown), Z-knife (as shown) Figure 2d (As shown). The resistance adjustment groove 201 is disposed on the resistor layer 202. From the perspective of current flow path analysis, the influence of the L-shaped cutter's termination point is less than that of the I-shaped cutter. See [reference needed]. Figure 3a As shown, the microcracks 101 produced by the "I"-shaped cutter (and similarly, the Z-shaped cutter) are perpendicular to the current flow direction 102, cutting into the area with the smallest current flow area. Figure 3bAs shown, the microcracks 101 generated by the "L"-shaped blade cutting are parallel to the current flow direction 102, and the current flow density in some crack areas is extremely low. Both blade types have drawbacks. For high-power product development, the main evaluation indicator is electrical performance. Conventional laser cutting blade types are prone to thermal breakdown during application testing, failing to meet the electrical performance requirements for high power applications. Therefore, in this embodiment, two L-shaped laser-cut trimmers with relatively open openings are provided, i.e., L-shaped cutters, and are positioned opposite each other on both sides of the width direction of the resistor layer. In this way, cutting with L-shaped cutters can increase the effective length of the resistor, lengthen the current path, and the cut point is located in a low current density local area. Taking the laser trimmers including horizontal grooves 13 and vertical grooves 14 as an example, the end of the vertical groove is connected to the outer wall of the resistor layer in the width direction, and it is set parallel to the side of the resistor layer in the length direction. One end of the horizontal groove is connected to the vertical groove inside the resistor layer, and the other end is set towards another laser-cut trimmer. Taking the direction shown in the figure as an example, it includes an upper laser-cut trimmer and a lower laser-cut trimmer. The lower laser-cut trimmer is close to the front electrode on the left side, and the upper laser-cut trimmer is close to the front electrode on the right side. The lower part of the vertical groove of the lower laser-cut trimmer is connected to the lower part of the resistor layer, and the left end of the horizontal groove of the lower laser-cut trimmer is connected to and perpendicular to the top of the vertical groove of the lower laser-cut trimmer. The upper vertical groove of the upper laser-cut trimming groove is connected to the upper part of the resistor layer, and the right end of the horizontal groove of the upper laser-cut trimming groove is connected to the lower part of the vertical groove of the upper laser-cut trimming groove and is perpendicular to it. The cut-off point is located at the end of the horizontal groove (the left end of the horizontal groove of the upper laser-cut trimming groove and the right end of the horizontal groove of the lower laser-cut trimming groove). The microcracks at the cut-off point of the L-cut (there will be some microcracks in the resistor layer at the cut-off point) spread in a direction parallel to the current direction and are located in a region with relatively low current density, which can effectively improve the electrical performance of the product and also improve the stability of the electrical performance of the resistor.
[0063] The two laser-cut adjustable grooves have a first spacing along the length of the resistor layer and a second spacing along the width of the resistor layer. Preferably, the width of the laser-cut adjustable groove is less than 1 / 4 of the width of the resistor layer, and the length of the laser-cut adjustable groove is less than 1 / 4 of the length of the resistor layer. Therefore, it can effectively lengthen the current path and improve the electrical performance of the resistor.
[0064] In the description of this utility model, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In the description of the invention, "a plurality of" means two or more, unless otherwise explicitly specified.
[0065] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. For instance, the two components can be mechanically connected by contact or abutting; they can also be directly hooked or connected by an intermediate medium; or they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.
Claims
1. A high-power thick-film resistor, comprising a substrate, a resistive layer, two front electrodes and two back electrodes, wherein the two back electrodes are symmetrically disposed on both sides of the back surface of the substrate, characterized in that: The resistive layer is mounted on the front side of the substrate, and both ends of the resistive layer are disposed close to the two ends of the front side of the substrate. Two front electrodes are symmetrically mounted at both ends of the front side of the substrate. The outer end of each front electrode is disposed on the front side of the substrate at the end of the resistive layer, and the inner end of each front electrode extends inward and covers the front side of the end of the resistive layer.
2. The high-power thick-film resistor according to claim 1, characterized in that: It also includes two end electrodes, which are disposed at both ends of the substrate, and the two ends of each end electrode respectively cover the front electrode and the back electrode on one side.
3. The high-power thick-film resistor according to claim 2, characterized in that: It also includes a first protective layer, which covers the front side of the resistive layer, and the two ends of the first protective layer respectively cover a portion of the front side of the two front electrodes; The first protective layer is further covered by a second protective layer, with both ends of the second protective layer covering a portion of the front surface of the front electrode.
4. The high-power thick-film resistor according to claim 3, characterized in that: The first protective layer is a glass protective layer, and the second protective layer is a resin protective layer.
5. The high-power thick-film resistor according to claim 1, characterized in that: The two front electrodes are disposed at both ends of the resistive layer along its length. The resistive layer has a laser-cut resistance adjustment groove on each side in the width direction.
6. The high-power thick-film resistor according to claim 5, characterized in that: One of the laser-cut trimmed grooves is positioned close to one of the front electrodes, and the other laser-cut trimmed groove is positioned close to another of the front electrodes.
7. The high-power thick-film resistor according to claim 5 or 6, characterized in that: The laser-cut resistance adjustment groove has an L-shaped structure, and the L-shaped openings of the two laser-cut resistance adjustment grooves are in opposite directions.
8. The high-power thick-film resistor according to claim 7, characterized in that: The two L-shaped openings of the laser-cut resistance adjustment grooves are arranged opposite each other.
9. The high-power thick-film resistor according to claim 7, characterized in that: The two laser-cut resistivity grooves have a first spacing in the length direction of the resistive layer and a second spacing in the width direction of the resistive layer.