Resistance device and manufacturing method thereof

Abstract

The invention relates to the technical field of resistors, in particular to a resistance device and a manufacturing method thereof. The resistance device comprises a base body, a resistive film and a terminal electrode, the base body is of a cylinder structure, and the resistive film wraps the outer surface of the base body; the outer ring of the resistive film is provided with a spiral groove, and the outer surface of the resistive film is provided with a protective layer; according to the resistance device and the manufacturing method thereof, line contact between the end electrode and the PCB is converted into surface contact through the arranged limiting surface, and the surface contact mode provides resistance for rolling of the resistance device. Moreover, the gravity center of the resistor device can be adjusted to a low position through the arranged counterweight part, and when the limiting surface is not in a downward state, the limiting surface can automatically rotate to a downward state under the combined action of the counterweight part and the circular section of the end electrode, so that on one hand, the rolling phenomenon of the resistor device is avoided, and on the other hand, the states of the resistor device before and after mounting are consistent, and the mounting efficiency is improved. And the orientation of the limiting surface does not need to be adjusted during mounting.

Description

Technical Field

[0001] This invention relates to the field of resistor technology, and more specifically, to a resistor device and its manufacturing method. Background Technology

[0002] Wafer resistors, also known as cylindrical resistors, leadless resistors, or leadless resistors, are mainly suitable for high-end circuits with high power, high voltage impact, and high safety requirements. They are surface mount components.

[0003] Wafer resistors offer the following advantages: 1. Due to their cylindrical structure and uniform thin-film layer, they can withstand significantly higher instantaneous pulse power (e.g., surge current) than chip resistors of the same size, and are less prone to burnout. They are ideal for surge suppression, current sensing, and snubber circuits. 2. Wafer resistors typically employ metal thin-film technology, resulting in a very low temperature coefficient (TCR) and minimal resistance change with temperature. 3. Compared to rectangular surface-mount resistors of the same power rating, they are generally smaller. For example, a 1W MELF resistor may occupy less PCB area than a 1W 2512-package surface-mount resistor. However, while the cylindrical structure of wafer resistors brings these advantages, it also presents the following problems: Because of its cylindrical shape, it is prone to rolling during manual or SMT placement processes, as well as in reflow ovens, causing it to deviate from its preset position and resulting in soldering defects. This places high demands on the placement process. Summary of the Invention

[0004] The purpose of this invention is to provide a resistor device and its manufacturing method, which solves the problem mentioned in the background art by setting a planar structure to change the contact between the terminal electrode and the PCB board from line contact to surface contact. That is, because it is cylindrical, it is easy to roll during manual or SMT pick-and-place process, as well as in the reflow soldering oven.

[0005] To achieve the above objectives, one objective of this invention is to provide a resistive device, comprising a substrate, a resistive film, and terminal electrodes. The substrate has a cylindrical structure, and the resistive film is wrapped around the outer surface of the substrate. The outer ring of the resistive film has helical grooves, and a protective layer is disposed on the outer surface of the resistive film. The terminal electrodes are located at both ends of the resistive film. The outer diameter of the end electrode is larger than the outer diameter of the protective layer. The outer ring of the end electrode is provided with a limiting surface for connecting PCB board pins. The limiting surface protrudes from the outer ring of the protective layer. The limiting surface changes the contact between the end electrode and the PCB board from line contact to surface contact. It also includes a counterweight, which is located at the position of the protective layer corresponding to the limiting surface. The counterweight is used to increase the weight of the resistor at the limiting surface, reduce the distance between the limiting surface and the center of gravity of the resistor, and make the limiting surface face downward under normal conditions.

[0006] The terminal electrode includes a metal end cap, a nickel plating layer disposed around the outer ring of the metal end cap, and a tin plating layer disposed around the outer ring of the nickel plating layer. The limiting surface has a planar structure, and the terminal electrode has a circular segment and a planar segment. Under the gravity of the counterweight, the resistive device rolls through the circular segment of the terminal electrode until the limiting surface is facing downwards.

[0007] In the above technical solution, the limiting surface increases the contact area with the PCB board, which allows the contact between the terminal electrode and the PCB board to change from the original line contact to a surface contact. This greatly reduces the phenomenon of the resistor device rolling when subjected to external interference during the mounting process.

[0008] Based on this, the structure of the confined surface can be categorized into the following two types: Structure 1: The outer ring of the metal end cap has a partial void area. The nickel plating layer has a uniform thickness around the entire ring, and the tin plating layer has a uniform thickness around the entire ring. The tin plating layer forms a limiting surface corresponding to the void area.

[0009] Structure 2: A plane is provided in a part of the outer ring of the tin plating layer, and a limiting surface is formed at the part of the tin plating layer corresponding to the plane.

[0010] Furthermore, the counterweight structure also exists in the following two forms: Structure 1: The counterweight is a counterweight block set on the outer ring of the protective layer, and the counterweight block is set on the limiting surface.

[0011] Structure 2: The counterweight is a protrusion, which is integrally formed on the corresponding limiting surface of the protective layer. The thickness of the corresponding limiting surface of the protective layer is greater than the thickness of other parts.

[0012] In another technical solution, the distance between the outer surface of the counterweight and the protective layer is consistent with that between the limiting surface and the protective layer, so that the bottom of the counterweight fits the surface of the PCB board.

[0013] This technical solution uses a counterweight that adheres to the PCB surface to block most of the molten solder, thereby reducing the risk of short circuits or other impacts on the PCB when the molten solder at both ends comes into contact.

[0014] The second objective of this invention is to provide a method for manufacturing a resistive device, comprising the following steps: S1. In a vacuum environment, a thin film of nickel-chromium alloy or similar precision alloy is deposited on a substrate by sputtering or evaporation technology to form a resistive film. S2. A protective layer is provided on the outer surface of the resistive film to cover the outer surface of the resistive film; S3. Cut off a portion of the outer ring of the tin plating layer along the axial direction of the tin plating layer, so that the corresponding cut-off part of the tin plating layer forms a restrictive surface; S4. Set a counterweight at the location corresponding to the limiting surface on the outer ring of the protective layer, and adjust the orientation of the limiting surface by adjusting the counterweight.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. In this resistor device and its manufacturing method, the contact between the terminal electrode and the PCB board is changed from line contact to surface contact by a limiting surface. This surface contact provides resistance to the rolling of the resistor device. Furthermore, the added counterweight adjusts the center of gravity of the resistor device to a low position. When the limiting surface is not facing downwards, the combined action of the counterweight and the circular segment of the terminal electrode causes the limiting surface to automatically rotate to a downward-facing position. This prevents the resistor device from rolling and ensures that the resistor device remains in the same state before and after mounting, eliminating the need to adjust the orientation of the limiting surface during mounting.

[0016] 2. In this resistor device and its manufacturing method, the counterweight not only ensures that the resistor device is in a state of facing downwards before and during mounting, but also adheres to the surface of the PCB board during mounting, blocking most of the solder and reducing the probability of contact between the solder at both ends, thereby reducing short circuits and damage caused by contact between the solder at both ends. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a cross-sectional structural diagram of the overall structure of the present invention; Figure 3 This is a schematic diagram of the structure of the terminal electrode of the present invention. Figure 1 ; Figure 4 This is a schematic diagram of the structure of the terminal electrode of the present invention. Figure 2 ; Figure 5 This is a schematic diagram of the structure of the metal end cap of the present invention; Figure 6 This is a schematic diagram of the tin plating layer of the present invention; Figure 7 This is a schematic diagram of the structure of the protrusion of the present invention; Figure 8 This is a schematic diagram of the partition cavity of the present invention.

[0018] The meanings of the labels in the diagram are as follows: 100. Substrate; 101. Resistive film; 102. Spiral groove; 103. Protective layer; 104. Color ring; 105. Protrusion; 110. Terminal electrode; 111. Restricting surface; 112. Metal end cap; 113. Nickel plating layer; 114. Tin plating layer; 115. Void area; 120. Counterweight; 200. PCB board. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this 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. Therefore, they should not be construed as limitations on this invention.

[0021] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0022] To address the problem of cylindrical resistors easily rolling during soldering, one objective of this invention is to provide a resistor device. For example... Figure 2As shown, the resistor is a leadless cylindrical resistor, mainly composed of a substrate 100, a resistive film 101, and terminal electrodes 110. The substrate 100 is a solid cylindrical structure made of high-purity (typically above 96%) alumina ceramic powder, serving as the framework of the entire resistor. It can withstand the mechanical stress during manufacturing and installation, while ensuring complete isolation between the resistor and the external circuit. The resistive film 101 is wrapped around the outer surface of the substrate 100. Materials used for the resistive film 101 include, for example, nickel-chromium alloys or ruthenium oxide. When using nickel-chromium alloys or similar precision alloys, a thin film of the nickel-chromium alloy or similar precision alloy is deposited on the substrate 100 in a vacuum environment using sputtering or evaporation techniques. This type of resistor offers the best performance (high precision, low temperature drift, low noise). When using ruthenium oxide, a resistive paste containing metal oxides (such as ruthenium oxide) is coated onto the substrate 100 via screen printing, followed by high-temperature sintering. Furthermore, the outer ring of the resistive film 101 is provided with spiral grooves 102. The spiral grooves 102 can increase the path length of current flow, thereby transforming the initial low resistance value into the high resistance value required by the design. The change in resistance value can be achieved by adjusting the spacing and depth of the spiral grooves 102.

[0023] To prevent the resistive film 101 and the spiral groove 102 from being affected by external factors, the present invention also provides a protective layer 103 on the outer surface of the resistive film 101. The protective layer 103 is made of glass enamel material and comprehensively covers the spiral groove 102 and the resistive film 101, achieving the purpose of isolating moisture, oxygen, dust, and various chemical contaminants, ensuring the long-term stability of the resistive film 101, and preventing resistance drift. Furthermore, since the resistive device is cylindrical, it cannot be printed with digital codes like a chip resistor; therefore, reference... Figure 1 This invention uses a color ring system to label parameters. Specifically, color rings 104 are printed on the outer surface of the protective layer 103. The color rings 104 are used to identify parameters such as resistance values ​​and tolerances.

[0024] Terminal electrodes 110 are located at both ends of the resistive film 101 and are used to connect the resistive film 101 to the PCB board 200. Specifically, the terminal electrodes 110 are composite multilayer structures, such as... Figure 4 As shown, the inner layer is a metal end cap 112, which has a ring structure. The inner ring is tightly pressed against the outer ring of the resistive film 101. The material is usually silver or a silver-palladium alloy to ensure excellent, low-resistance ohmic contact with the resistive film 101. The middle layer is a nickel-plated layer 113, which forms a barrier layer to prevent tin in the external solder from diffusing inward and corroding the inner electrode during soldering, thus reducing connection reliability. The outer layer is a tin-plated layer 114, which provides excellent solderability, oxidation resistance, and corrosion resistance, facilitating surface mounting.

[0025] Next, to prevent the resistor from rolling, the outer diameter of the terminal electrode 110 is first adjusted to be larger than the outer diameter of the protective layer 103. Then, a limiting surface 111 is provided on the outer ring of the terminal electrode 110, protruding from the outer ring of the protective layer 103. Figure 2 Taking the state of the limiting surface 111 as an example, when the limiting surface 111 is facing downwards, its height is no higher than the bottom height of the outer ring of the protective layer 103. Furthermore, the limiting surface 111 is used to connect the pins of the PCB board 200. The limiting surface 111 changes the contact between the terminal electrode 110 and the PCB board 200 from line contact to surface contact, preventing the resistor from rolling. Next, the resistor also includes a counterweight, which is located on the protective layer 103 corresponding to the limiting surface 111. This counterweight increases the weight of the resistor at the location corresponding to the limiting surface 111, reducing the distance between the limiting surface 111 and the center of gravity of the resistor, ensuring that the limiting surface 111 is normally in a downward-facing state.

[0026] In other words, the limiting surface 111 changes the contact between the terminal electrode 110 and the PCB board 200 from line contact to surface contact. This surface contact provides resistance to the rolling of the resistor. Furthermore, the counterweight adjusts the center of gravity of the resistor to a lower position. When the limiting surface 111 is not facing downwards, the combined action of the counterweight and the circular segment of the terminal electrode 110 causes the limiting surface 111 to automatically rotate to a downward-facing position. This prevents the resistor from rolling and ensures that the resistor remains in the same state before and after mounting, eliminating the need to adjust the orientation of the limiting surface 111 during mounting.

[0027] Specifically, such as Figure 3 As shown, the limiting surface 111 has a planar structure and is located on the outer ring of the end electrode 110, giving the end electrode 110 both a circular segment and a planar segment. Because the counterweight is located on the protective layer 103 corresponding to the limiting surface 111, the planar segment has a larger weight. Therefore, under the influence of gravity, the end electrode 110 will rotate to... Figure 3 The state shown is that the limiting surface 111 faces downwards. With this design, the terminal electrode 110 is in the state of limiting surface 111 facing downwards both before and during mounting. Therefore, when clamping the resistor device, there is no need to adjust the orientation of the limiting surface 111. At the same time, it also further avoids the rolling phenomenon of the resistor device during soldering.

[0028] During implementation, a portion of the outer ring of the end electrode 110 is cut off along the axial direction of the end electrode 110. At this time, the cut-off portion of the outer ring of the end electrode 110 becomes the limiting surface 111. It should be noted that after cutting, the height of the limiting surface 111 facing downwards must not be higher than the height of the bottom of the outer ring of the protective layer 103.

[0029] The formation of the limiting surface 111 is described in detail by means of the following embodiments: exist Figure 5 In the illustrated embodiment, a partial void area 115 is provided on the outer ring of the metal end cap 112, and the portion of the void area 115 corresponding to the outer ring of the metal end cap 112 is planar. Next, the nickel plating layer 113 has a uniform thickness throughout its entire ring, and the tin plating layer 114 also has a uniform thickness throughout its entire ring. In this way, the portion of the tin plating layer 114 corresponding to the void area 115 is parallel to the void area 115, and at this point, the portion of the tin plating layer 114 corresponding to the void area 115 forms a limiting surface 111.

[0030] In this embodiment, a portion of the outer ring of the vacancy area 115 is cut off along the axial direction of the vacancy area 115. Then, when setting the nickel plating layer 113 and the tin plating layer 114, it is only necessary to ensure that the thickness of the nickel plating layer 113 and the tin plating layer 114 are consistent throughout their entire ring. At this time, the portion of the tin plating layer 114 corresponding to the vacancy area 115 automatically forms a limiting surface 111. For specific effects, refer to... Figure 5 .

[0031] exist Figure 6 In the illustrated embodiment, a plane is partially provided on the outer ring of the tin plating layer 114, and a limiting surface 111 is formed at the portion of the tin plating layer 114 corresponding to the plane. In implementation, a portion of the outer ring of the tin plating layer 114 is cut off along its axial direction. At this time, the limiting surface 111 automatically forms at the cut portion of the tin plating layer 114. For specific effects, refer to [reference needed]. Figure 6 .

[0032] In addition, the present invention also provides the following two structures for the counterweight part.

[0033] First structural reference Figure 1 The embodiment shown has a counterweight 120 disposed on the outer ring of the protective layer 103. The counterweight 120 is disposed opposite to the limiting surface 111, meaning both the counterweight 120 and the limiting surface 111 face downwards. The counterweight 120 is made of an insulating material, such as ceramic. The counterweight 120 and the protective layer 103 can be connected by means of bonding, sleeve connection, or other methods.

[0034] Second structural reference Figure 7 The illustrated embodiment shows a counterweight portion, a protrusion 105, integrally formed on the protective layer 103 at the corresponding limiting surface 111, such that the thickness of the protective layer 103 at the corresponding limiting surface 111 is greater than the thickness of other portions. In implementation, with... Figure 7 Taking the illustrated state as an example, when setting the protective layer 103, the bottom of the protective layer 103 is made thicker, which increases the weight of the bottom of the protective layer 103. This embodiment is suitable for some lighter resistive devices.

[0035] In the two structures described above, the distance between the outer surface of the counterweight and the protective layer 103 cannot be greater than the distance between the limiting surface 111 and the protective layer 103; otherwise, the protruding counterweight will lift up the limiting surface 111, preventing the limiting surface 111 from contacting the PCB board 200.

[0036] The working principle of resistive devices will be explained in more detail below: Before mounting, under the gravity of the counterweight 120, the counterweight 120 applies a downward force to the resistor. The resistor rolls along the circular segment of the limiting surface 111. When the limiting surface 111 faces downwards, the resistor's center of gravity is at its lowest, and the resistor stops rotating. At this point, the limiting surface 111 faces downwards. During mounting, the surface contact between the limiting surface 111 and the PCB board 200, combined with the gravity of the counterweight 120, makes it difficult for the counterweight 120 to roll during the soldering process.

[0037] Furthermore, considering that during the soldering process, molten solder at one end electrode 110 may flow to the other end electrode 110, this could easily damage the entire PCB board 200. Therefore, [the following measures are taken]. Figure 8 Taking the state shown and the counterweight 120 as an example, the present invention adjusts the bottom height of the counterweight to be consistent with the bottom of the limiting surface 111. At this time, it can be found that the bottom of the counterweight is attached to the surface of the PCB board 200, thereby blocking most of the solder liquid at both ends of the resistor device.

[0038] In addition, the bottom of the counterweight can be a flat structure, while the rest of the parts are arc-shaped (the whole corresponds to the end electrode 110, which can be understood as the counterweight being consistent with the lower half of the end electrode 110), which can improve the blocking effect on the molten solder.

[0039] In summary, the counterweight not only ensures that the resistor device is in a state with the limiting surface 111 facing down before and during mounting, but also adheres to the surface of the PCB board 200 during the mounting process, blocking most of the solder and reducing the probability of contact between the solder at both ends, thereby reducing short circuits and damage caused by contact between the solder at both ends.

[0040] The second objective of this invention is to provide a method for manufacturing a resistive device, comprising the following steps: S1. In a vacuum environment, a thin film of nickel-chromium alloy or similar precision alloy is deposited on the substrate 100 by sputtering or evaporation technology to form a resistive film 101. S2. A protective layer 103 is provided on the outer surface of the resistive film 101 to cover the outer surface of the resistive film 101; S3. Cut off a portion of the outer ring of the tin plating layer 114 along the axial direction of the tin plating layer 114, so that the corresponding cut portion of the tin plating layer 114 forms a limiting surface 111. S4. A counterweight is provided at the position of the outer ring of the protective layer 103 corresponding to the limiting surface 111, and the orientation of the limiting surface 111 is adjusted by the counterweight.

[0041] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A resistive device, comprising a substrate (100), a resistive film (101), and terminal electrodes (110), wherein the substrate (100) is a cylindrical structure, and the resistive film (101) is wrapped around the outer surface of the substrate (100); a spiral groove (102) is provided on the outer ring of the resistive film (101), and a protective layer (103) is provided on the outer surface of the resistive film (101); the terminal electrodes (110) are located at both ends of the resistive film (101), characterized in that: The outer diameter of the end electrode (110) is larger than the outer diameter of the protective layer (103). The outer ring of the end electrode (110) is provided with a limiting surface (111) for connecting the pins of the PCB board (200). The limiting surface (111) protrudes from the outer ring of the protective layer (103). The limiting surface (111) changes the contact between the end electrode (110) and the PCB board (200) from line contact to surface contact. It also includes a counterweight, which is located at the part of the protective layer (103) corresponding to the limiting surface (111) to increase the weight of the part of the resistor device corresponding to the limiting surface (111), reduce the distance between the limiting surface (111) and the center of gravity of the resistor device, and make the limiting surface (111) face downward under normal conditions.

2. The resistive device according to claim 1, characterized in that: The terminal electrode (110) includes a metal end cap (112), a nickel plating layer (113) disposed on the outer ring of the metal end cap (112), and a tin plating layer (114) disposed on the outer ring of the nickel plating layer (113).

3. The resistive device according to claim 2, characterized in that: The metal end cap (112) has a ring structure, with the inner ring pressed against the outer ring of the resistive film (101).

4. The resistive device according to claim 2, characterized in that: The limiting surface (111) is a planar structure, and the end electrode (110) has a circular segment and a planar segment. Under the gravity of the counterweight, the resistive device rolls through the circular segment of the end electrode (110) until the limiting surface (111) is facing downwards.

5. The resistive device according to claim 4, characterized in that: The outer ring of the metal end cap (112) has a partial void area (115), the nickel plating layer (113) has a uniform thickness around the whole ring, the tin plating layer (114) has a uniform thickness around the whole ring, and the tin plating layer (114) forms a limiting surface (111) corresponding to the void area (115).

6. The resistive device according to claim 4, characterized in that: The outer ring of the tin plating layer (114) is partially provided with a plane, and the portion of the tin plating layer (114) corresponding to the plane forms a limiting surface (111).

7. The resistive device according to claim 1, characterized in that: The counterweight is a counterweight block (120) disposed on the outer ring of the protective layer (103), and the counterweight block (120) is disposed on the limiting surface (111).

8. The resistive device according to claim 1, characterized in that: The counterweight is a protrusion (105), which is integrally formed on the part of the protective layer (103) corresponding to the limiting surface (111). The thickness of the part of the protective layer (103) corresponding to the limiting surface (111) is greater than the thickness of other parts.

9. The resistive device according to claim 1, characterized in that: The distance between the outer surface of the counterweight and the protective layer (103) is consistent with the distance between the limiting surface (111) and the protective layer (103), so that the bottom of the counterweight fits the surface of the PCB board (200).

10. A method for manufacturing a resistive device as described in any one of claims 6-9, characterized in that: The methods and steps include the following: S1. In a vacuum environment, a thin film of nickel-chromium alloy or similar precision alloy is deposited on a substrate (100) by sputtering or evaporation technology to form a resistive film (101). S2. A protective layer (103) is provided on the outer surface of the resistive film (101) to cover the outer surface of the resistive film (101); S3. Cut off a portion of the outer ring of the tin plating layer (114) along the axial direction of the tin plating layer (114) so ​​that the corresponding cut portion of the tin plating layer (114) forms a limiting surface (111). S4. A counterweight is provided at the position of the outer ring of the protective layer (103) corresponding to the limiting surface (111), and the orientation of the limiting surface (111) is adjusted by the counterweight.

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