Locally Encapsulated High-Power Alloy Resistor with Antioxidant Property

Abstract

The present invention discloses an antioxidant high-power alloy resistor with partial encapsulation, which is characterized in that it includes a resistor body, electrodes located on both sides of the resistor body, an encapsulation material covering a partial surface of the alloy resistor, and a nickel-tin layer covering the remaining surface; the remaining surface of the high-power alloy resistor, excluding the two end faces in the length direction and the parts of the electrodes for subsequent welding, is covered with the encapsulation material, and the remaining surfaces are covered with the nickel-tin layer. For the antioxidant high-power alloy resistor with partial encapsulation of the present invention, the whole product is encapsulated, and the ends and welding areas of the product are electroplated with nickel-tin to achieve antioxidant performance during the reflow soldering process of the product.

Description

[0001] This application is a divisional application of the invention patent application with the application date of January 10, 2023, application number 2023100377100, and invention title "An antioxidant high-power alloy resistor with partial encapsulation and its preparation method". Technical Field

[0002] The present invention belongs to the technical field of alloy resistors, and particularly relates to an antioxidant high-power (at least 7W) alloy resistor with partial encapsulation. Background Art

[0003] High-power alloy resistors have the advantages of high power and low resistance accuracy compared with traditional encapsulated resistors. Since they are made of pure alloy materials, there are no existing products and processes for encapsulating high-power alloy resistors in the prior art. The disadvantage of this structure is that wave soldering cannot be performed at the client side, and solder climbing during the soldering process will have a certain impact on the resistance value and temperature drift. However, the encapsulation of traditional encapsulated resistors is highly dependent on molds, which is cumbersome to debug for different product devices and consumes a large amount of power. In addition, traditional high-power alloy resistors are stamped and bent into an arch shape. Since the temperature coefficient of resistance of copper is much larger than that of alloy, the proportion of copper in the arch greatly increases the temperature coefficient of the product.

[0004] In existing high-power alloy resistor products, when the product is short-circuited and overloaded, the heating temperature of the product reaches 500 - 700 °C. Existing encapsulation materials cannot meet the requirements of this test condition. Therefore, currently, high-power shunt resistors all use a method of forming a passivation layer on the surface to solve the antioxidant problem before use.

[0005] For example, the invention patent application with the application number CN109102973A discloses a resistor and a manufacturing method of the resistor. However, only the position below the resistor body uses a common method such as spraying, printing, roll coating or other similar coating materials to apply paint or epoxy resin. Not only is the coating area boundary unclear and the spraying area accuracy difficult to control, which in turn affects the resistance value of the product, especially for low-resistance resistor products that are sensitive to resistance values. Moreover, the antioxidant layer of the product prepared by it will crack during the reflow soldering process, and the product will thus lose its protective effect. Summary of the Invention

[0006] In view of this, in order to overcome the defects of the prior art, the purpose of the present invention is to provide an antioxidant high-power alloy resistor with partial encapsulation to achieve full protection of the high-power alloy resistor.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions:

[0008] A preparation method of a high-power alloy resistor with partial encapsulation, comprising the following steps:

[0009] Weld the electrode strip and the alloy strip to obtain a strip of material;

[0010] Die-cut the strip of material to form a plurality of alloy resistors on the strip of material;

[0011] Perform a plastic encapsulation operation on the entire strip of material so that the outer surface of the alloy resistor is completely covered with a plastic encapsulation material;

[0012] Remove the plastic encapsulation material on the area of the alloy resistor corresponding to the electrode for subsequent welding;

[0013] Separate the alloy resistor from the strip of material to form the partially plastic-encapsulated high-power alloy resistor;

[0014] Perform barrel plating of nickel-tin on the partially plastic-encapsulated high-power alloy resistor so that plating layers are formed on both end faces and the welding area of the alloy resistor.

[0015] According to some preferred implementation aspects of the present invention, during welding, the length extension directions of the electrode strip and the alloy strip are the same, and the welding is to weld the electrode strip to the side surface in the width direction of the alloy strip by means of electron beam welding.

[0016] According to some preferred implementation aspects of the present invention, the electrode strip is used to form the electrode of the high-power alloy resistor, and the alloy strip is used to form the resistor body of the high-power alloy resistor; the thickness of the electrode strip is greater than the thickness of the alloy strip.

[0017] According to some preferred implementation aspects of the present invention, on one side in the thickness direction of the strip of material, the electrode strip is flush with the alloy strip; on the other side in the thickness direction of the strip of material, the surface of the electrode strip is higher than the surface of the alloy strip to form a welding area.

[0018] According to some preferred implementation aspects of the present invention, the plastic encapsulation is to immerse the entire strip of material in the plastic encapsulation material or spray the plastic encapsulation material onto the entire strip of material, and then perform drying and curing so that the entire strip of material is completely plastic-encapsulated. Immersing the strip of material product in a high-temperature resistant polyimide material has a simple and easy-to-operate method and low cost.

[0019] According to some preferred implementation aspects of the present invention, the removal is to remove the plastic encapsulation material on the welding area by means of laser ablation. Using laser ablation can selectively remove the electrode polymer to achieve a plastic-encapsulated product with low cost, high efficiency, and high yield.

[0020] According to some preferred implementation aspects of the present invention, the plastic encapsulation material is a polyimide material, preferably a high-temperature resistant polyimide material, and its thermal decomposition temperature is 500 - 600 °C.

[0021] According to some preferred implementation aspects of the present invention, the width of the electrode is greater than the width of the resistor body.

[0022] According to some preferred implementation aspects of the present invention, the operating power of the high-power alloy resistor is greater than or equal to 7W, and the power of products with the same specifications is higher than that of traditional plastic-encapsulated resistors.

[0023] According to some preferred implementation aspects of the present invention, the separation is performed by longitudinally cutting along the thickness direction of the tape to form individual bridge-shaped locally plastic-encapsulated resistors.

[0024] The present invention also provides a locally plastic-encapsulated high-power alloy resistor prepared by the preparation method as described above.

[0025] Due to the adoption of the above technical solutions, compared with the prior art, the beneficial effects of the present invention are as follows: The locally plastic-encapsulated antioxidant high-power alloy resistor of the present invention is integrally plastic-encapsulated, and the ends and welding areas of the product are electroplated with nickel-tin to achieve antioxidant performance during the reflow soldering process of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0027] Figure 1 It is a schematic cross-sectional structure diagram of the locally plastic-encapsulated antioxidant high-power alloy resistor in the embodiment of the present invention;

[0028] Figure 2 It is a schematic top view structure diagram of the locally plastic-encapsulated antioxidant high-power alloy resistor in the embodiment of the present invention;

[0029] Figure 3 It is a schematic structure diagram of the tape when preparing the antioxidant high-power alloy resistor in the embodiment of the present invention

[0030] In the drawings, 1: Locally plastic-encapsulated antioxidant high-power alloy resistor; 2: Strip; 3: Alloy resistor body; 4: Spacing area; 5: Connection; 8: Plastic encapsulation material; 9: Resistor body; 10: Electrode; 11: Ni plating layer; 12: Sn plating layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] To enable those skilled in the art to better understand the technical solution of the present invention, the following will clearly and completely describe the technical solution in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0032] Embodiment 1 High-power alloy resistor

[0033] As Figures 1-3 shown, the locally potted high-power alloy resistor 1 in this embodiment includes a resistor body 9, electrodes 10 on both sides of the resistor body 9, a potted material 8 covering a part of the surface of the alloy resistor, nickel-tin layers 11 and 12 covering the remaining surface, and the electrodes 10 are welded to both sides in the length direction of the resistor body 9 by electron beam welding. The width of the electrode 10 is greater than the width of the resistor body 9, and the width direction here refers to the width direction of the high-power alloy resistor 1.

[0034] The thickness of the electrode 10 is greater than that of the resistor body 9. Specifically, on one side in the thickness direction of the high-power alloy resistor 1, the electrode 10 is flush with the resistor body 9; on the other side in the thickness direction of the high-power alloy resistor 1, the surface of the electrode 10 is higher than the surface of the resistor body 9 and extends outward.

[0035] In this embodiment, except for the two end faces in the length direction of the high-power alloy resistor 1 and the parts (welding areas) of the electrodes 10 for subsequent welding, the remaining surface is covered with a potted material 8, while the remaining surfaces are covered with a nickel plating layer 11 and a tin plating layer 12, which can effectively achieve antioxidant performance during the reflow soldering process of the product.

[0036] The locally potted high-power alloy resistor 1 in this embodiment has the advantages of high power, high resistance accuracy, low temperature drift, wave soldering, and low manufacturing cost.

[0037] Embodiment 2 Preparation method

[0038] This embodiment provides a preparation method for the locally potted high-power alloy resistor 1 based on Embodiment 1, which specifically includes the following steps:

[0039] Step 1. Prepare a strip

[0040] According to the required resistance value, select appropriate alloy strip materials and appropriate electrode strip materials. The alloy strip material is usually Mn-Cu alloy, etc.; the electrode strip material is pure copper material with low resistivity. The electrode strip material and the alloy strip material are welded by electron beam welding to obtain an arched strip of electrode + alloy + electrode. The middle of the strip is electrode + alloy + electrode, and the two sides are strip materials 2 connected to the electrodes.

[0041] During welding, the length extension directions of the electrode strip and the alloy strip are the same, and the two electrode strips are welded to the side surfaces in the width direction of the alloy strip. Among them, the thickness of the electrode strip is greater than that of the alloy strip. The electrode strip is used to form the electrode 10 of the high-power alloy resistor 1, and the alloy strip is used to form the resistor body 9 of the high-power alloy resistor 1. The width of the finally formed electrode 10 is greater than that of the resistor body 9.

[0042] On one side in the thickness direction of the strip, the electrode strip is flush with the alloy strip; on the other side in the thickness direction of the strip, the surface of the electrode strip is higher than the surface of the alloy strip to form a welding area.

[0043] Step 2: Punching

[0044] The strip is punched according to the predetermined size required for the resistance value, so that a plurality of alloy resistor bodies 3 are formed on the strip. The two ends of each resistor alloy body are connected to the strip 2 at the connection position 5 of the ends of the electrode 10 to form a strip. The plurality of alloy resistor bodies 3 are arranged in sequence along the length direction of the strip, and there is a spaced area 4 formed by punching between adjacent alloy resistor bodies 3.

[0045] Step 3: Encapsulation

[0046] An encapsulation operation is performed on the entire strip. The entire strip is immersed in the encapsulation material 8 or the encapsulation material 8 is sprayed onto the entire strip, and then dried and cured so that the entire strip is completely encapsulated, and the outer surface of the alloy resistor body 3 is completely covered with the encapsulation material 8.

[0047] The encapsulation material 8 is a high-temperature resistant polyimide material, whose tensile strength is 250 - 500 MPa, the thermal decomposition temperature is 500 - 600 °C, the thermal expansion coefficient is 1×10 -6 / °C, and the smoke emission rate is extremely low, and the char residue rate after high-temperature combustion is above 50%.

[0048] Step 4: Laser

[0049] The encapsulation material 8 corresponding to the welding area (i.e., the bottom of the electrode 10) on the alloy resistor body 3 is removed by laser ablation, exposing the copper substrate, which is convenient for subsequent welding with the solder pad. The accuracy of the laser ablation can be controlled within ±0.2 mm.

[0050] Step 5: Granulation

[0051] The connection position 5 between the electrode 10 and the strip 2 on the encapsulated strip is granulated, and longitudinally cut along the thickness direction of the strip to separate the alloy resistor body 3 from the strip, forming a partially encapsulated high-power alloy resistor 1 with a working power greater than or equal to 7 W.

[0052] The obtained locally encapsulated high-power alloy resistor 1 has a resistor body 9 and two welding electrodes 10. Except for the surfaces (welding areas) at the bottoms of the electrodes 10 and the two end faces in the length direction without an encapsulation layer, the remaining parts all have an encapsulation layer.

[0053] Step 6, electroplating

[0054] The product is barrel-plated with nickel-tin, so that nickel-tin plating layers 11 and 12 are formed on the two end faces and the welding areas of the product, and a locally encapsulated antioxidant high-power alloy resistor 1 is obtained. That is, the two end faces of the obtained high-power alloy resistor 1 and the welding areas of the electrodes have a nickel plating layer 11 and an outer tin plating layer 12, and the surfaces of the remaining parts all have an encapsulation layer 8.

[0055] The electrical properties of the product prepared by the above method are as follows: the power is 7-9w, the resistance value accuracy is 0.5%, and the short-term overload test is 5 times the rated power.

[0056] The preparation method of the locally encapsulated high-power alloy resistor of the present application changes the traditional stamping and bending process of high-power alloy resistors, selects materials with an electrode thickness greater than the alloy thickness and directly welds them into an arched material, greatly reducing the proportion of copper in the arch and thus reducing the resistance temperature coefficient of the product. In addition, selective encapsulation of the high-power alloy resistor reduces the manufacturing cost, and the specifications of the encapsulated products are diversified. Finally, electroplating is carried out on the exposed positions of copper, which has a better antioxidant effect, and then the locally encapsulated high-power alloy resistor is prepared. It not only has high-power characteristics and a low resistance temperature coefficient, but also avoids the influence of tin climbing to the resistor body during the welding process on the resistance value and temperature drift, and can be welded by wave soldering process. Compared with the prior art, the present application adopts a stepped welding method to achieve a low-temperature drift product; soaking the product in a high-temperature resistant polyimide material, the method is simple and easy to operate, and the cost is low. Using precisely controlled (±0.2mm) laser to selectively remove the electrode polymer can achieve low-cost, high-efficiency, and high-yield encapsulated products; the applicable product sizes have greater flexibility in selection and do not rely on molds; the high-temperature resistant polyimide material of the resistor body can achieve the high-power resistance performance of the product; electroplating nickel-tin on the resistor ends and welding areas can achieve antioxidant performance during the reflow soldering process of the product; the overall encapsulation + electroplating of the product can achieve better antioxidant performance.

[0057] The preparation method of the locally encapsulated high-power alloy resistor of the present invention uses tape welding, punching, encapsulation, and then granulation and encapsulation. The preparation is convenient and gets rid of the dependence on molds; the product is integrally encapsulated, and the ends and welding areas of the product are electroplated with nickel-tin to achieve antioxidant performance during the reflow soldering process of the product.

[0058] The above embodiments obtained by the method of the present invention are only for illustrating the technical concept and features of the present invention. The purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and it should not be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A locally encapsulated antioxidant high-power alloy resistor, characterized in that, It includes a resistor body, electrodes located on both sides of the resistor body, a plastic encapsulation material covering a partial surface of the alloy resistor, and a nickel-tin layer covering the remaining surface; for the high-power alloy resistor, except for the two end faces in the length direction and the remaining surface of the electrodes for subsequent welding parts, the remaining surface is covered with the plastic encapsulation material, and the other surfaces are covered with the nickel-tin layer; The high-power alloy resistor is prepared in the order of preparing a strip, punching, plastic encapsulation, laser ablation, granulation, and electroplating; for the plastic encapsulation, the entire strip is immersed in the plastic encapsulation material or the plastic encapsulation material is sprayed onto the entire strip, and then dried and cured to completely encapsulate the entire strip; on one side of the high-power alloy resistor in the thickness direction, the electrode is flush with the resistor body; on the other side of the high-power alloy resistor in the thickness direction, the surface of the electrode is higher than the surface of the resistor body and extends outward to form a welding area; the laser ablation is to remove the plastic encapsulation material on the welding area by means of laser ablation; the working power of the high-power alloy resistor is greater than or equal to 7W.

2. The alloy resistor according to claim 1, characterized in that, The electrodes are welded to both sides of the resistor body in the length direction by electron beam welding to obtain an arched strip of electrode + alloy + electrode.

3. The alloy resistor according to claim 1, characterized in that, The width of the electrode is greater than the width of the resistor body, and this width direction is the width direction of the high-power alloy resistor.

4. The alloy resistor according to claim 1, characterized in that, The thickness of the electrode is greater than the thickness of the resistor body.

5. The alloy resistor according to claim 1, characterized in that, The plastic encapsulation material is a polyimide material with a thermal decomposition temperature of 500 - 600°C.

6. The alloy resistor according to claim 1, characterized in that, The material of the resistor body is an Mn-Cu alloy, and the material of the electrode is a copper material.

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