A high power thick film resistor

Abstract

The utility model discloses a kind of high-power thick film resistors, including substrate, resistance layer, two pieces of front electrode and two pieces of back electrode, the resistance layer and two pieces of front electrode are set on the front of the substrate, two pieces of the front electrode are respectively set on the both sides of the resistance layer, two pieces of the back electrode are respectively set on the back of the substrate, it is characterized in that: two pieces of the back electrode are respectively set on the both sides of the back of the substrate, and there is spacing between two pieces of the back electrode, the length of a piece of the back electrode is greater than the length of another piece of the back electrode;Radial cutting knife edge is also provided on the resistance layer, and the radial cutting knife edge is opposite to a piece of the back electrode setting.

Description

Technical Field

[0001] This utility model relates to a resistor, and more particularly to a high-power thick-film resistor. Background Technology

[0002] As power electronic systems rapidly evolve towards higher power density and miniaturization, the thermal management of thick-film resistors, as key current-limiting components, is becoming increasingly prominent in high-power applications. Common approaches to improve the heat dissipation of thick-film resistors include widening or increasing the thickness of the resistive film (increasing the cross-sectional area of ​​the resistive layer, reducing current density, and minimizing localized heat generation), or replacing the substrate with one of high thermal conductivity (alumina substrate: 24 W / m·K, aluminum nitride: 170 W / m·K) to improve overall heat dissipation efficiency. However, these solutions directly increase costs and reduce product competitiveness. The cost of the resistive ink accounts for the highest proportion of the cost of thick-film resistors, and the aforementioned solutions all increase ink usage; aluminum nitride substrates are expensive and have poor process compatibility. Therefore, solving these technical problems is a direction that those skilled in the art need to address. Summary of the Invention

[0003] The purpose of this invention is to provide a high-power thick-film resistor. By using this structure, the heat dissipation effect of the resistor is effectively improved, and the power handling capability of the resistor is further enhanced.

[0004] 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 resistive layer and the two front electrodes are disposed on the front side of the substrate, the two front electrodes are respectively disposed on both sides of the resistive layer, the two back electrodes are respectively disposed on both sides of the back side of the substrate, and there is a gap between the two back electrodes, wherein the length of one back electrode is greater than the length of the other back electrode;

[0005] The resistive layer is also provided with a laser cutting edge, which is positioned directly opposite one of the back electrodes.

[0006] In the above technical solution, one end of each front electrode is flush with the sidewall of one side of the substrate, and the other end extends toward the center of the substrate.

[0007] In the above technical solution, one end of each back electrode is flush with the sidewall of one side of the substrate, and the other end extends toward the middle of the substrate.

[0008] In the above technical solution, the area of ​​one of the back electrodes is 10% to 15% of the area of ​​the substrate, and the area of ​​the other back electrode is 40% to 50% of the area of ​​the substrate.

[0009] In the above technical solution, the resistive layer is covered with a first protective layer, and the two ends of the first protective layer respectively cover the front part of the front electrode on both sides.

[0010] In the above technical solution, the first protective layer is covered by a second protective layer, and the two ends of the second protective layer respectively cover the front part of the front electrodes on both sides.

[0011] In the above technical solution, end electrodes are respectively provided on both sides of the substrate. One end of the end electrode covers part of the front surface of the corresponding front electrode, and the other end of the end electrode covers the corresponding back electrode.

[0012] In the above technical solution, the back electrode includes a first back electrode and a second back electrode, the length of the second back electrode is greater than the length of the first back electrode, and the laser cutting edge is positioned directly opposite the second back electrode.

[0013] Due to the application of the above technical solution, this utility model has the following advantages compared with the prior art:

[0014] 1. In this utility model, one of the back electrodes is widened to facilitate heat dissipation during resistor operation, thereby improving the resistor's power handling capability;

[0015] 2. The present invention uses two asymmetrical back electrodes, which can avoid the risk of the two back electrodes connecting during the welding process due to the small gap between the two back electrodes;

[0016] 3. In this invention, the temperature at the end of the laser cutting blade is the highest. By positioning the laser cutting blade directly against the longer back electrode on the back of the substrate, the heat from the laser cutting blade can be transferred to the back electrode through the substrate. The projection area of ​​the laser cutting blade is within a large area of ​​the back electrode, which helps to reduce the heat accumulation of the resistive layer at the laser cutting blade and achieve a better heat dissipation effect. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure in Embodiment 1 of this utility model.

[0018] The components are: 1. substrate; 2. resistive layer; 3. front electrode; 4. back electrode; 5. laser cutting edge; 6. first back electrode; 7. second back electrode; 8. first protective layer; 9. second protective layer; 10. end electrode; 11. vacuum coating layer; 12. electroplating layer. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0020] Example 1: See Figure 1As 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 resistive layer 2 and the two front electrodes 3 are disposed on the front side of the substrate 1. The two front electrodes 3 are respectively disposed on both sides of the resistive layer 2, and the two ends of the resistive layer 2 respectively cover the front sides of the two front electrodes 3. The two back electrodes 4 are respectively disposed on both sides of the back side of the substrate 1, and there is a gap between the two back electrodes 4. The length of one back electrode 4 is greater than the length of the other back electrode 4.

[0021] The resistive layer 2 is also provided with a laser cutting edge 5, which is positioned directly opposite a back electrode 4.

[0022] In this embodiment, the front side of the substrate is the top surface, and the back side is the bottom surface. The substrate uses a conventional ceramic substrate (e.g., alumina ceramic, or other commonly used ceramic substrates), which is inexpensive and uses the same substrate material as existing high-power thick-film resistors, without adding extra cost. The heat generated by the high-power thick-film resistor during operation is mainly dissipated through the path of "substrate—back electrode—solder pad—PCB board". In this embodiment, increasing the length of one of the back electrodes, i.e., increasing the area of ​​the back electrode, increases the cross-sectional area of ​​the heat dissipation channel, thereby improving heat dissipation, extending service life, and increasing the resistor's power handling capability. Simultaneously, laser-cut edges are provided on the resistor layer. After laser cutting, local hot spots are formed, which are the main factor leading to thermal breakdown of the thick-film resistor. The temperature is highest at the end of the laser-cut edge, which is also a common area of ​​failure for thick-film resistors. Therefore, in this embodiment, the laser cutting edge faces a back electrode. The heat generated by the resistive layer at the laser cutting edge during operation is conducted downward through the substrate to the back electrode. The projection range of the laser cutting edge is included in the back electrode it faces. This helps to reduce the accumulation (piling up, agglomeration) of heat in the resistive layer at the laser cutting edge, further improving the heat dissipation effect, increasing the power resistance of the resistor, and extending the service life of the thick film resistor.

[0023] See Figure 1 As shown, one end of each of the front electrodes 3 is flush with the sidewall of one side of the substrate 1, and the other end extends toward the center of the substrate 1.

[0024] One end of each of the back electrodes 4 is flush with the sidewall of one side of the substrate 1, and the other end extends toward the center of the substrate 1.

[0025] The back electrode 4 includes a first back electrode 6 and a second back electrode 7, wherein the length of the second back electrode 7 is greater than the length of the first back electrode 6, and the laser cutting edge 5 is positioned directly opposite the second back electrode 7. The area of ​​the first back electrode 6 is 10% to 15% of the area of ​​the substrate 1, and the area of ​​the second back electrode 7 is 40% to 50% of the area of ​​the substrate 1.

[0026] In this embodiment, taking the illustrated direction as an example, the first back electrode is located on the left side of the bottom surface of the substrate, with its left end flush with the left side wall of the substrate. The second back electrode is located on the right side of the bottom surface of the substrate, with its right end flush with the right side wall of the substrate. The left end of the left front electrode is flush with the left side wall of the substrate, and the right end of the right front electrode is flush with the right side wall of the substrate. In this embodiment, the length and width of the first back electrode are equal to or approximately the same as the length and width of the two front electrodes. The laser cutting edge is located within the projection range of the second back electrode. Since the laser cutting edge is within the projection range of the large-area back electrode, the accumulation of heat in the resistive layer at the laser cutting edge can be effectively reduced.

[0027] Meanwhile, the area of ​​the first back electrode is 10% to 15% of the area of ​​the back surface of the substrate, and the area of ​​the second back electrode is 40% to 50% of the area of ​​the back surface of the substrate. That is, the sum of the areas of the two back electrodes is more than 50% of the area of ​​the back surface of the substrate (the entire thick-film resistor). Since the thick-film resistor is connected to the PCB board through solder pads, increasing the length and area of ​​one of the back electrodes increases the bonding strength between the thick-film resistor and the PCB board, effectively increasing resistance to external impacts and vibrations, and improving stability in use. Furthermore, since the area of ​​the two back electrodes accounts for more than 50% of the area of ​​the thick-film resistor, its heat dissipation capacity is further increased. In the testing of the 0402 model product, it can withstand a load power increase of more than 5 times when the load power increases from 1 / 16W to 1 / 3W.

[0028] Furthermore, the two back electrodes are of different lengths, meaning they adopt an unbalanced layout, which can balance the contradiction between miniaturization of thick film resistors and high-power applications to a certain extent.

[0029] Meanwhile, in this embodiment, increasing the length of only one side of the back electrode avoids the risk of the two back electrodes becoming connected due to excessively small gaps between them during soldering with the PCB board. Furthermore, since the laser cutting edge is located on the front side of the substrate on the side of the large-sized second back electrode, the temperature field distribution of the back electrode below the laser cutting edge is more uniform, and the closer distance between the laser cutting edge and the back electrode improves heat dissipation.

[0030] See Figure 1As shown, the front side of the resistive layer 2 is covered by a first protective layer 8, and the two ends of the first protective layer 8 respectively cover a portion of the front side of the front electrodes 3 on both sides.

[0031] The first protective layer is a glass protective layer. In the direction shown in the figure, its bottom surface completely covers the top surface of the resistive layer, and its two ends respectively cover the top surface of the front electrodes on both sides, which is used to insulate and protect the resistive layer.

[0032] See Figure 1 As shown, the front of the first protective layer 8 is covered by the second protective layer 9, and the two ends of the second protective layer 9 respectively cover the front portions of the front electrodes 3 on both sides.

[0033] The second protective layer is a resin protective layer. In the illustrated direction, the bottom surface of the second protective layer completely covers the top surface of the first protective layer, and its two ends respectively cover the top surfaces of the front electrodes on both sides, which is used to further insulate and protect the first protective layer and the resistive layer.

[0034] See Figure 1 As shown, the substrate 1 has end electrodes 10 on both sides. One end of the end electrode 10 covers part of the front surface of the corresponding front electrode 3, and the other end of the end electrode 10 covers the corresponding back electrode 4.

[0035] In this embodiment, end electrodes 10 are respectively disposed on the left and right sides of the substrate. Each end electrode 10 includes a vacuum-deposited layer 11 and an electroplated layer 12 covering the outside of the vacuum-deposited layer 11. The inner surface of the vacuum-deposited layer covers the sidewall of the substrate (the vacuum-deposited layers of the end electrodes on both sides cover the left and right sidewalls of the substrate, respectively). One end of the vacuum-deposited layer covers the sidewall and front surface of one side of the front electrode, with its end abutting against the outer surface of the second protective layer. Thus, through the resistive layer, the first protective layer, the second protective layer, and the end of the vacuum-deposited layer, the outer surface of the front electrode is completely covered, preventing the front electrode from being exposed. The other end of the vacuum-deposited layer covers the sidewall and part of the bottom surface of one side of the back electrode, but its bottom does not completely cover the back electrode. The vacuum-deposited layer connects the front electrode and the back electrode on one side. The electroplating layer completely covers the outside of the vacuum coating layer. One end of the electroplating layer rests against the front of the second protective layer, completely covering the vacuum coating layer at that end. The other end of the electroplating layer completely covers the exposed back electrode on one side and rests against the back of the substrate.

[0036] In the preparation of thick film resistors, back electrodes and front electrodes are printed on the back and front sides of the substrate, respectively, and then sintered and cured. Then, the resistor layer is printed and sintered, followed by the printing and sintering of the first protective layer, and then laser cutting to repair the resistor. After the laser cutting and repair is completed, the second protective layer is printed, sintered and cured, and then the strips are arranged. After the strips are arranged, the vacuum coating layer is deposited, and then the granules are folded. After the granules are folded, the electroplated layer is prepared.

[0037] In the process of laser cutting and resisting, the resistive layer is laser-cut from the first protective layer. Therefore, the laser cutting edge is set on the resistive layer and the first protective layer, and the second protective layer can shield and protect the laser cutting edge.

[0038] 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.

[0039] 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 resistive layer and the two front electrodes are disposed on the front side of the substrate, the two front electrodes are respectively disposed on both sides of the resistive layer, and the two back electrodes are respectively disposed on the back side of the substrate, characterized in that: The two back electrodes are respectively disposed on both sides of the back side of the substrate, and there is a gap between the two back electrodes. The length of one back electrode is greater than the length of the other back electrode. The resistive layer is also provided with a laser cutting edge, which is positioned directly opposite one of the back electrodes.

2. The high-power thick-film resistor according to claim 1, characterized in that: One end of each of the front electrodes is flush with the sidewall of one side of the substrate, and the other end extends toward the center of the substrate.

3. The high-power thick-film resistor according to claim 1, characterized in that: One end of each of the back electrodes is flush with the sidewall of one side of the substrate, and the other end extends toward the center of the substrate.

4. The high-power thick-film resistor according to claim 3, characterized in that: One of the back electrodes has an area of ​​10% to 15% of the substrate area, and the other back electrode has an area of ​​40% to 50% of the substrate area.

5. The high-power thick-film resistor according to claim 1, characterized in that: The resistive layer is covered with a first protective layer, and the two ends of the first protective layer respectively cover the front part of the front electrodes on both sides.

6. The high-power thick-film resistor according to claim 5, characterized in that: The first protective layer is covered by a second protective layer, and the two ends of the second protective layer respectively cover the front part of the front electrodes on both sides.

7. The high-power thick-film resistor according to claim 6, characterized in that: The substrate has end electrodes on both sides, one end of the end electrode covers part of the front surface of the corresponding front electrode, and the other end of the end electrode covers the corresponding back electrode.

8. The high-power thick-film resistor according to claim 1, characterized in that: The back electrode includes a first back electrode and a second back electrode, the length of the second back electrode is greater than the length of the first back electrode, and the laser cutting edge is positioned directly opposite the second back electrode.

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