Current detection resistor and manufacturing method thereof

Abstract

The invention relates to a current detection resistor and a manufacturing method thereof. The current detection resistor comprises a resistor disc, two cooling fins and an insulating sleeve, two electrode parts are arranged at the two ends of the resistor disc, each cooling fin comprises a connecting part, a transition part and a tilting part which are connected in sequence, the connecting part is attached to the single electrode part, the two cooling fins are separated, and the insulating sleeve is arranged between the two cooling fins. The middle part of the resistor disc and the transition parts and the upwarp parts of the two radiating fins are completely wrapped by the insulating sleeve; and the upwarp parts are closer to the outer wall of the insulating sleeve than the connecting parts. When the current detection resistor is used, the tilting part is separated from the resistor disc by a certain distance, so that the two surfaces of the tilting part have effective heat dissipation areas and can dissipate heat to the material of the insulating sleeve, and the upper surface of the tilting part is closer to the outer wall of the insulating sleeve, so that the heat can be quickly dissipated, and the current detection resistor can bear higher power under the same volume. The manufacturing method comprises the steps of raw material preparation, raw material bonding, in-mold injection molding and film coating. The current detection resistor is simple in structure, easy to install, low in cost and suitable for batch production.

Description

Technical Field

[0001] This invention belongs to the field of current sensing resistor technology, and relates to a current sensing resistor and its manufacturing method. Background Technology

[0002] A current-sensing resistor, also known as a shunt, is a resistive device used to detect the current in a circuit. Its operation is based on Ohm's law, which states that current is directly proportional to voltage and inversely proportional to resistance. A current-sensing resistor circuit typically consists of two resistive branches: one to measure the current in the circuit, and the other to measure the resistance itself. When current flows through the circuit, one branch of the current-sensing resistor (usually the smaller resistor) experiences a voltage drop. This voltage drop is measured through the other branch (usually the larger resistor), allowing the calculation of the current value in the circuit. By reading the voltage drop across the current-sensing resistor, the magnitude of the current in the circuit can be determined. Current-sensing resistors are widely used in power management, motor control, inverters, and other fields for accurate current detection. Their main functions include: 1) Current sampling: Converts current into a voltage signal (U=IR) through its own small resistance (usually in the milliohm range), which is then collected and analyzed by subsequent circuits (such as op-amps, MCUs); 2) Overcurrent protection: When the current exceeds the threshold, the protection circuit will trigger power-off or current limiting to prevent equipment damage; 3) Precision control: Provides real-time current feedback to adjust the system's operating status in scenarios such as motor drive and power management.

[0003] The formula for resistor power consumption is: Therefore, it inevitably generates heat during operation. Poor heat dissipation can lead to the following problems: 1) Power limitation: Conventional sensing resistors are limited by size and heat dissipation capacity, resulting in low power density, which cannot meet the requirements of high-current and high-precision sampling.

[0004] 2) Excessive temperature rise: When operating at high power, the temperature of the resistor body rises rapidly, causing resistance drift, decreased accuracy, or even burnout.

[0005] 3) Complex heat dissipation structure: Some solutions improve heat dissipation by increasing the encapsulation or adding thermal paste, but installation is inconvenient, costly, and the effect is limited.

[0006] Chinese patent CN117790096A discloses a double-sided alloy foil current sensing resistor and its preparation method. The double-sided alloy foil current sensing resistor includes a substrate and electrodes located at both ends of the substrate. It also includes a first alloy foil resistive body covering the upper surface of the substrate and a second alloy foil resistive body covering the lower surface of the substrate. The first and second alloy foil resistive bodies are simultaneously electrically connected to the electrodes at both ends to form a parallel structure. In this invention, both the upper and lower alloy foil resistive bodies can dissipate heat, increasing the heat dissipation area by 100% compared to the single-sided resistive body in the prior art. This effectively solves the heat dissipation problem of current sensing resistors, thereby improving product power. However, in this structure, the middle section between the first and second alloy foil resistive bodies is sealed at the junction of the protective layer and the ceramic substrate. Since the protective layer and the ceramic substrate are made of different materials, they are prone to separation due to differences in expansion and contraction during use, leading to seal failure. If dust or liquid enters, it may cause a short circuit.

[0007] Chinese patent CN219418632U discloses a packaged alloy resistor with a heat dissipation structure, comprising: a resistor body, an insulating layer, two heat sinks, and a packaging layer. To prevent the resistor body from forming a new circuit with the two heat sinks, the resistor body and the heat sinks are separated by an insulating layer, and there is a blocking gap between the two heat sinks. The main body (middle part) of the heat sinks should cover as much of the resistor body as possible. The problem with this structure is that the addition of the insulating layer not only increases the manufacturing steps, but also the thermal conductivity of the insulating layer is difficult to match that of the heat sinks, resulting in a decrease in heat dissipation performance.

[0008] Therefore, it is necessary to provide a current sensing resistor with better heat dissipation to solve the above problems. Summary of the Invention

[0009] The purpose of this invention is to provide a current sensing resistor that can increase the heat dissipation area, withstand higher power with a smaller volume, ensure high-precision sampling, and have a long service life.

[0010] The present invention achieves the above objective through the following technical solution: a current sensing resistor, comprising a resistive element, two heat sinks and an insulating sleeve, wherein the two ends of the resistive element are two electrode portions, and the heat sink includes a connecting portion, a transition portion and a raised portion connected in sequence, wherein the connecting portion is attached to a single electrode portion, the two heat sinks are separated, the middle portion of the resistive element and the transition portion and raised portion of the two heat sinks are completely wrapped by the insulating sleeve, and the raised portion is closer to the outer wall of the insulating sleeve than the connecting portion.

[0011] Specifically, the heat sink is made of aluminum sheet with a thickness of 0.15mm.

[0012] Specifically, the raised portion is spaced 1-2 mm from the resistor sheet.

[0013] Specifically, the heat sink transition portion has notches on both sides, and the width of the raised portion is smaller than the width of the connecting portion.

[0014] Specifically, the insulating sleeve is made of a material with a thermal conductivity ≥1W / (m·K) and an insulation strength ≥14kV / mm.

[0015] Specifically, the middle part of the resistor sheet has an S-shaped curved structure.

[0016] Specifically, the electrode portion and the outer end of the heat sink form an electrode, and the electrode is covered with a plating layer, which consists of a copper layer, a nickel layer and a tin layer from the inside to the outside.

[0017] Specifically, the surface of the insulating sleeve is marked.

[0018] Another object of the present invention is to provide a manufacturing method for obtaining the above-mentioned current sensing resistor.

[0019] This invention achieves the above objective through the following technical solution: a method for manufacturing a current sensing resistor, comprising the following steps: S1. Raw material preparation: The resistor sheet and two heat sinks are stamped to form the resistor sheet and two heat sinks respectively. The resistor sheet has a planar sheet structure and the heat sink has a Z-shaped bending structure. S2, Material bonding: The connecting parts of the two heat sinks are fixed to the electrode parts of the resistor to form electrodes. The two raised parts are not connected to each other and are located above the resistor to form a connecting body. S3. In-mold injection molding: The insulating sleeve is formed by injection molding in the middle of the connector. The insulating sleeve completely covers the middle of the resistor and the transition and raised part of the two heat sinks to form a plastic body. The electrode extends from both ends of the insulating sleeve. S4. Coating: A copper layer, a nickel layer and a tin layer are electroplated sequentially on the electrode to form a complete coating, thus obtaining the current detection resistor.

[0020] Specifically, markings are made on the surface of the insulating sleeve after the in-mold injection molding step.

[0021] The beneficial effects of the technical solution of this invention are: 1) The raised part is separated from the resistor piece by a certain distance, so both sides of the raised part are effective heat dissipation areas and can dissipate heat to the insulating sleeve material. The upper surface of the raised part is closer to the outer wall of the insulating sleeve, so it can dissipate heat faster, allowing the current sensing resistor to withstand higher power in the same volume. 2) The high thermal conductivity of the heat sink can reduce the temperature rise of the resistor, reduce resistance drift, and maintain sampling accuracy; 3) Simple structure, easy to install, low cost, suitable for mass production; 4) High reliability, extended resistor life, and reduced failure rate. Attached Figure Description

[0022] Figure 1 This is a cross-sectional view of the current sensing resistor in Example 1; Figure 2 This is a diagram illustrating the manufacturing process of the current sensing resistor in Example 1; Figure 3 This is a top view of the combined state of the resistor and heat sink in Example 1; Figure 4 This is a top view of the combined state of the resistor and heat sink in Example 2.

[0023] Figure 3 and Figure 4 The thinner outline is the outline of the resistor, and the thicker outline is the outline of the heat sink.

[0024] The diagram is marked as follows: 1-Resistor element; 11-Electrode section; 2-Heat sink, 21-Connector, 22-Transition section, 221-Notch, 23-Raised section; 3-Insulating sleeve; 4-plating layer, 41-copper layer, 42-nickel layer, 43-tin layer; 5-Identification. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to specific embodiments.

[0026] Example 1: like Figure 1 As shown, a current sensing resistor includes a resistive element 1, two heat sinks 2, and an insulating sleeve 3. The two ends of the resistive element 1 are two electrode portions 11. The heat sink 2 includes a connecting portion 21, a transition portion 22, and a raised portion 23 connected in sequence. The connecting portion 21 is attached to a single electrode portion 11. The two heat sinks 2 are separated. The middle part of the resistive element 1 and the transition portion 22 and raised portion 23 of the two heat sinks 2 are completely wrapped by the insulating sleeve 3. The raised portion 23 is closer to the outer wall of the insulating sleeve 3 than the connecting portion 21.

[0027] Both heat sinks 2 only have their connecting portions 21 in contact with the resistor piece 1, and they are separated by an insulating material (the material of the insulating sleeve 3), so no new conductive path is created. The heat sinks 2 can be made of 0.15mm thick aluminum sheets. Although thin, they possess a certain structural rigidity after stamping, maintaining the distance between their raised portions 23 and the resistor piece 1. Aluminum has a very low density (2.7g / cm³). 3While the heat sink 2 has a thermal conductivity as high as 237 W / (m·K), its heat dissipation performance is better than most insulating materials (the material of the insulating sleeve 3). The connecting part 21 provides a heat dissipation surface, and through direct contact with the electrode part 11, heat is quickly conducted to the raised part 23, reducing the temperature of the resistor 1. Theoretically, the heat sink 2 can also be made of materials such as copper, silver, gold, aluminum alloy, and aluminum nitride, but some materials are expensive, dense, or difficult to process, making aluminum more suitable. The raised part 23 is separated from the resistor 1 by a certain distance (1-2 mm), so both sides of the raised part 23 are effective heat dissipation areas, which can dissipate heat to the material of the insulating sleeve 3. The upper surface of the raised part 23, being closer to the outer wall of the insulating sleeve 3, can dissipate heat more quickly, allowing the current sensing resistor to withstand higher power in the same volume. The high thermal conductivity of the heat sink 2 can reduce the temperature rise of the resistor 1, reduce resistance drift, and maintain sampling accuracy.

[0028] like Figure 3 As shown, the heat sink 2 has notches 221 on both sides of the transition portion 22, and the width of the raised portion 23 is smaller than the width of the connecting portion 21.

[0029] The connecting portion 21 and the electrode portion 11 are superimposed to form an electrode, allowing for the joint electroplating of other elements on the surface. The transition portion 22 separates the raised portion 23 from the resistive element 1 by a small distance, enabling the insulating material to surround the raised portion 23 from all sides. Of the three parts of the heat sink 2, the transition portion 22 is the narrowest, followed by the raised portion 23, and the connecting portion 21 is the widest. Because the width of the connecting portion 21 is the same as that of the electrode portion 11, heat can be conducted away more quickly. The structure of the heat sink 2 controls the heat conduction path. Heat can dissipate from the raised portion 23 to the surrounding insulating material, mainly occurring on the upper and lower surfaces. Even though the raised portion 23 is slightly narrower, it still provides a sufficiently large heat exchange area. However, from an injection molding perspective, narrowing the raised portion 23 allows for a thicker sidewall of the insulating sleeve 3, preventing cracking. The notch 221 and the partition space between the two heat sinks 2 provide a channel for the flowing insulating material, allowing it to fill the space below the raised portion 23.

[0030] like Figure 1 and Figure 2 As shown, the electrode part 11 and the outer end of the heat sink 2 form an electrode. A plating layer 4 is provided on the outside of the electrode. The plating layer 4 consists of a copper layer 41, a nickel layer 42, and a tin layer 43 from the inside to the outside. The surface of the insulating sleeve 3 is marked with a mark 5.

[0031] The base copper layer 41 ensures electrode conductivity, the middle nickel layer 42 enhances electrode corrosion resistance, and the outer tin layer 43 facilitates soldering. The label 5 indicates the model information of this current sensing resistor.

[0032] like Figure 2As shown, the manufacturing method of the current sensing resistor includes the following process steps: S1. Raw material preparation: Separately stamping to form a resistor sheet 1 and two heat sinks 2. The resistor sheet 1 has a flat sheet structure, and the heat sink 2 has a Z-shaped bending structure. S2, Material bonding: The connecting part 21 of the two heat sinks 2 is fixed to the electrode part 11 of the resistor 1 to form an electrode. The two raised parts 23 are not connected to each other and are located above the resistor 1 to form a connecting body. S3, In-mold injection molding: An insulating sleeve 3 is formed by injection molding in the middle of the connector. The insulating sleeve 3 completely wraps the middle of the resistor 1 and the transition part 22 and the raised part 23 between the two heat sinks 2 to form a plastic body. The electrodes extend from both ends of the insulating sleeve 3. S4. Manufacturing markings: Markings 5 ​​are manufactured on the surface of the insulating sleeve 3; S5. Coating: A copper layer 41, a nickel layer 42, and a tin layer 43 are electroplated sequentially on the electrode to form a complete coating 4, thus obtaining a current detection resistor.

[0033] The marking 5 on the current sensing resistor serves only as an annotation and does not affect the resistor's function; it is not a key element in this process. The marking 5 can be formed using methods such as laser marking, screen printing, or inkjet printing.

[0034] This current sensing resistor has a simple structure, is easy to install, and is low in cost, making it suitable for mass production. It also boasts high reliability, extends resistor lifespan, and reduces the failure rate.

[0035] Example 2: like Figure 4 As shown, the difference from Embodiment 1 is that the middle part of the resistor 1 has an S-shaped curved structure.

[0036] In Example 1, the resistor 1 has a simple strip structure in the middle, and its length is fixed, so its resistance is controlled only by the size of its cross-sectional area. In Example 2, the resistor 1 has a longer middle section, which means that within the same top-view area, the resistance can be increased, the current can be reduced, and the range can be increased.

[0037] The above are merely some embodiments of the present invention. For those skilled in the art, various modifications and improvements can be made without departing from the inventive concept of the present invention, and all such modifications and improvements fall within the scope of protection of the present invention.

Claims

1. A current sensing resistor, characterized in that: The device includes a resistor, two heat sinks, and an insulating sleeve. The resistor has two electrode portions at both ends. The heat sink includes a connecting portion, a transition portion, and a raised portion connected in sequence. The connecting portion is attached to a single electrode portion. The two heat sinks are separated. The middle part of the resistor and the transition portion and raised portion of the two heat sinks are completely wrapped by the insulating sleeve. The raised portion is closer to the outer wall of the insulating sleeve than the connecting portion.

2. The current sensing resistor according to claim 1, characterized in that: The heat sink is made of aluminum sheet with a thickness of 0.15mm.

3. The current sensing resistor according to claim 1, characterized in that: The raised portion is spaced 1-2 mm from the resistor sheet.

4. The current sensing resistor according to claim 1, characterized in that: The heat sink transition section has notches on both sides, and the width of the raised section is smaller than the width of the connecting section.

5. The current sensing resistor according to claim 1, characterized in that: The insulating sleeve is made of a material with a thermal conductivity ≥1W / (m·K) and an insulation strength ≥14kV / mm.

6. The current sensing resistor according to claim 1, characterized in that: The resistor sheet has an S-shaped curved structure in the middle.

7. The current sensing resistor according to claim 1, characterized in that: The electrode portion and the outer end of the heat sink form an electrode. The electrode is covered with a plating layer, which consists of a copper layer, a nickel layer, and a tin layer from the inside out.

8. The current sensing resistor according to claim 1, characterized in that: The surface of the insulating sleeve is marked.

9. A method for manufacturing the current sensing resistor according to claims 1-8, characterized in that... The steps include: S1. Raw material preparation: The resistor sheet and two heat sinks are stamped to form the resistor sheet and two heat sinks respectively. The resistor sheet has a planar sheet structure and the heat sink has a Z-shaped bending structure. S2, Material bonding: The connecting parts of the two heat sinks are fixed to the electrode parts of the resistor to form electrodes. The two raised parts are not connected to each other and are located above the resistor to form a connecting body. S3. In-mold injection molding: The insulating sleeve is formed by injection molding in the middle of the connector. The insulating sleeve completely covers the middle of the resistor and the transition and raised part of the two heat sinks to form a plastic body. The electrode extends from both ends of the insulating sleeve. S4. Coating: A copper layer, a nickel layer and a tin layer are electroplated sequentially on the electrode to form a complete coating, thus obtaining the current detection resistor.

10. The manufacturing method according to claim 1, characterized in that: After the in-mold injection molding step, markings are made on the surface of the insulating sleeve.

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