TWI863671B - Current sensing resistors and method of manufacturing the same - Google Patents

Abstract

A current sensing resistor and a method of fabricating the same are provided. The current sensing resistor includes the resistance layer with the first surface and the second surface, two first electrodes and the second electrode. The first surface and the second surface are located on two opposite sides of the resistance layer. The first electrodes are located on the first surface of the resistance layer and are separately located on two ends of the first surface. The second electrode is located on the second surface of the resistance layer. The region of the second electrode where the resistance layer overlaps is across two first electrodes, while the second electrode overlaps at least a part of each first electrode. Thus, one of the first electrodes is electrically connected to the other one of the first electrodes through the second electrode, so that the heat dissipation efficiency is increased.

Description

Current flow measuring resistor and manufacturing method thereof

The present disclosure relates to an inductive flow measuring resistor, and more particularly to an inductive flow measuring resistor with heat dissipation function and a manufacturing method thereof.

It is known that the current flow sensing resistor is to set a pair of electrodes at both ends of the substrate carrier, and form a resistance layer under the pair of electrodes and distribute between the pair of electrodes. Generally speaking, when the current flows through the current flow sensing resistor, the heat generated is dissipated from the substrate carrier (for example, ceramic) by air convection or thermal radiation, or the heat is conducted to the circuit board through the electrodes at both ends, thereby realizing the overall heat dissipation of the current flow sensing resistor. Since the heat energy is mainly generated by the resistance layer, the heat energy is easily concentrated on the substrate carrier between the above-mentioned electrodes. However, the indirect heat dissipation efficiency of air convection or thermal radiation through the substrate carrier is poor, so it is difficult to improve the situation where the temperature of the current flow sensing resistor is too high.

On the other hand, based on the law of resistance, if the material remains unchanged and the electrode spacing is fixed, if you want to reduce the resistance of the resistor layer, you must increase its thickness to increase the cross-sectional area through which the current flows. However, the size of the current flow sensing resistor is limited by the product specifications of the electronic component, so it is not possible to arbitrarily reduce the resistance by increasing the thickness of the resistor layer.

Therefore, the present disclosure provides an inductive flow sensing resistor and a manufacturing method thereof to improve the heat dissipation efficiency of the inductive flow sensing resistor.

The present disclosure provides an inductive flow sensing resistor, which includes a resistor layer, two first electrodes and a second electrode. The resistor layer has a first surface and a second surface, and the first surface and the second surface are respectively located on opposite sides of the resistor layer. Two first electrodes are located on the first surface of the resistor layer and are respectively located at opposite ends of the first surface. The second electrode is located on the second surface of the resistor layer, and the area where the second electrode overlaps with the resistor layer spans between the two first electrodes. The second electrode overlaps with at least a portion of each first electrode.

In at least one embodiment of the present disclosure, the resistivity of the second electrode is smaller than the resistivity of the resistive layer.

In at least one embodiment of the present disclosure, the current flow sensing resistor further includes two layers of protective layers. The protective layers are respectively located on the first surface and the second surface of the resistor layer, and the first electrode and the second electrode are located between the two layers of protective layers. The protective layer located on the first surface covers the first electrode and exposes an area of the first electrode, respectively, while the protective layer located on the second surface covers the second electrode.

In at least one embodiment of the present disclosure, the current flow sensing resistor further includes two solder materials. These solder materials are respectively located on the first electrode and are electrically connected to the first electrode. The solder materials cover the area of the first electrode exposed by the protective layer.

In at least one embodiment of the present disclosure, each solder material includes a solder layer and an electrode layer. The electrode layer is located between the solder layer and one of the first electrodes, wherein the solder layer and the electrode layer have an interface, and the protective layer located on the first surface has a top surface. The interface protrudes from the top surface, and the distance between the interface and the top surface is greater than 5 μm.

In at least one embodiment of the present disclosure, each solder material has an interface between one of the first electrodes, and the protective layer located on the first surface has a top surface. The interface protrudes from the top surface, and the distance between the interface and the top surface is greater than 5μm.

In at least one embodiment of the present disclosure, the current sensing resistor further includes a resistance trimming region located on the first electrode and extending to the resistor layer.

The present disclosure also provides a method for manufacturing an inductive sensing resistor, comprising providing a resistor layer having a first surface and a second surface; forming two first electrodes on the first surface of the resistor layer, and the first electrodes are respectively located at two opposite ends of the first surface; and forming a second electrode on the second surface of the resistor layer, and the region where the second electrode overlaps with the resistor layer spans between the two first electrodes. The second electrode overlaps with at least a portion of each of the first electrodes.

In at least one embodiment of the present disclosure, after forming the first electrode, a protective layer is disposed on the resistor layer. The protective layer is located on the first surface of the resistor layer and covers the first electrode. The protective layer exposes an area of the first electrode.

In at least one embodiment of the present disclosure, after forming the first electrode, a welding material is formed on the first electrode, and the welding material covers the area of the first electrode exposed by the protective layer.

In at least one embodiment of the present disclosure, after forming the second electrode, a protective layer is disposed on the resistor layer. The protective layer is located on the second surface of the resistor layer and covers the second electrode.

Based on the above, the present disclosure sets a second electrode with a lower resistivity on one side of the resistor layer so that the current tends to pass from one of the first electrodes through the second electrode to reach the other first electrode. In this way, the heat generated by the resistor layer can be dispersed to the first electrodes at both ends, and the heat is conducted to the outside through the first electrodes. In addition, the second electrode located on one side of the resistor layer also provides a heat dissipation path, which helps to improve the overall heat dissipation efficiency.

The present disclosure will be described in detail with the following embodiments. It should be noted that the following description of the embodiments of the present disclosure is only used for illustration and is not intended to disclose all embodiments in detail or to limit the specific embodiments of the present disclosure. For example, the description of "a first feature formed on a second feature" includes a variety of implementations, including the first feature and the second feature being in direct contact, and also including additional features formed between the first feature and the second feature so that the two are not in direct contact. In addition, the same component symbols used in the drawings and the specification will represent the same or similar components as much as possible.

In the following text, in order to clearly present the technical features of the present disclosure, the dimensions (e.g., length, width, thickness, and depth) of the elements (e.g., layers, films, substrates, and regions, etc.) in the drawings will be enlarged in a non-uniform manner. Therefore, the description and explanation of the embodiments below are not limited to the dimensions and shapes presented by the elements in the drawings, but should cover the dimensions, shapes, and deviations therefrom caused by actual processes and/or tolerances. For example, the flat surface shown in the drawings may have rough and/or nonlinear features, and the sharp corners shown in the drawings may be rounded. Therefore, the elements presented in the drawings of the present disclosure are mainly used for illustration, and are not intended to accurately depict the actual shapes of the elements, nor are they used to limit the scope of the patent application of the present disclosure.

Referring to FIG. 1 , the present embodiment discloses an electric current sensing resistor 10, which includes a resistor layer 100, a first electrode 120a, a first electrode 120b, and a second electrode 140. The resistor layer 100 has a first surface 100f and a second surface 100s, and the first surface 100f and the second surface 100s are respectively located on opposite sides of the resistor layer 100. The first electrode 120a and the first electrode 120b are located on the first surface 100f of the resistor layer 100, and are respectively located at opposite ends of the first surface 100f. In some embodiments, the resistor layer 100 may include, for example, copper manganese tin (CuMnSn), copper manganese nickel (CuMnNi), other appropriate alloy materials, or any combination of the above materials.

There is a distance D1 between the first electrode 120a and the first electrode 120b. In this embodiment, the distance D1 ranges from 1/4 of the length d to 4/5 of the length d in terms of the length d, width w and thickness t of the chip resistor, wherein the length d, width w and thickness t of the chip resistor are respectively equivalent to the length L, width (not shown) and thickness T of the resistor layer 100, as shown in FIG1. On the other hand, the second electrode 140 is located on the second surface 100s of the resistor layer 100, and the overlapping area of the second electrode 140 and the resistor layer 100 spans between the first electrode 120a and the first electrode 120b. In addition, the second electrode 140 overlaps at least a portion of the first electrode 120a and the first electrode 120b. Although in this embodiment, the second electrode 140 covers a portion of the first electrode 120a and the first electrode 120b, the present disclosure is not limited thereto. In other embodiments, the second electrode 140 may also completely cover the first electrode 120a and the first electrode 120b.

The materials of the first electrode 120a, the first electrode 120b and the second electrode 140 may be the same and may include copper. In particular, the resistivity of the second electrode 140 is less than the resistivity of the resistor layer 100. For example, the resistor layer 100 may include an alloy having a resistivity ranging from 20×10 ⁻⁸ Ω•m to 55×10 ⁻⁸ Ω•m (e.g., copper-nickel, copper-manganese, manganese-copper-tin and alloys related to copper elements), while the second electrode 140 may include a metal having a resistivity of approximately 1.7×10 ⁻⁸ Ω•m (e.g., copper). When a voltage is applied to the current sensing resistor 10 and a potential difference is generated between the first electrode 120a and the first electrode 120b, the first electrode 120a and the first electrode 120b, the resistor layer 100 and the second electrode 140 are electrically connected to each other, thereby forming a current path I as shown in FIG. 1 .

Since the resistivity of the second electrode 140 is less than the resistivity of the resistor layer 100, the current sensing resistor 10 tends to electrically connect its input end and output end through the second electrode 140 to form a current path I. In detail, the current is collected from one of the first electrodes (for example, the first electrode 120a) and reaches one end of the second electrode 140 (i.e., the end overlapping with the first electrode 120a) through the first surface 100f and the second surface 100s of the resistor layer 100. Then, the current travels from one end of the second electrode 140 toward the other end of the second electrode 140. After reaching the other end of the second electrode 140, the current tends to pass through the second surface 100s and the first surface 100f of the resistor layer 100 and enter the first electrode 120b.

Based on the above current tendency, although the first electrode 120a and the first electrode 120b at both ends can be electrically connected through the resistor layer 100, since the resistivity of the second electrode 140 is smaller than that of the resistor layer 100, the proportion of the current electrically connected to the first electrodes at both ends (i.e., the first electrode 120a and the first electrode 120b) through the second electrode 140 is higher than the proportion of the current electrically connected to the first electrodes at both ends through the resistor layer 100. In other words, the resistor layer 100 and the second electrode 140 located between the two first electrodes will electrically connect the first electrode 120a to the first electrode 120b in parallel, and most of the total current will choose to pass through the second electrode 140. Therefore, the resistance of the current sensing resistor 10 is not only provided by the resistor layer 100, and is not limited by the size of the resistor layer 100. Specifically, when the resistance of the current sensing resistor 10 needs to be reduced, the second electrode 140 provides a lower resistance, and there is no need to increase the thickness of the resistor layer 100 to increase the cross-sectional area for current flow.

In particular, since the first electrodes 120a and 120b are electrically connected to the resistor layer 100 through the two ends of the first surface 100f and the two ends of the second surface 100s, the heat generated by the resistor layer 100 is concentrated at the two ends thereof, and the heat can be thermally transferred to the outside through the first electrodes 120a and 120b.

The current sensing resistor 10 further includes a protective layer 160a and a protective layer 160b, which are respectively located on the first surface 100f and the second surface 100s of the resistor layer 100. As shown in FIG1 , the protective layer 160a is located on the first surface 100f, and the protective layer 160b is located on the second surface 100s. The first electrode 120a, the first electrode 120b and the second electrode 140 are located between the protective layer 160a and the protective layer 160b. In particular, the protective layer 160a located on the first surface 100f covers the first electrode 120a and the first electrode 120b, and exposes the regions 120r of the first electrode 120a and the first electrode 120b, respectively.

On the other hand, the protective layer 160b located on the second surface 100s covers the second electrode 140. Although in this embodiment, the protective layer 160b completely covers the surface (not shown) of the second electrode 140, the present disclosure is not limited thereto. In other embodiments, the protective layer 160b may also expose a portion of the surface of the second electrode 140. The protective layer 160a and the protective layer 160b may include organic polymer materials such as polyimide (PI) and epoxy resin.

In addition, the current sensing resistor 10 further includes two soldering materials 180. The two soldering materials 180 are respectively located on the first electrode 120a and the first electrode 120b, and are electrically connected to the first electrode 120a and the first electrode 120b. The soldering material 180 covers the region 120r of the first electrode 120a (and the first electrode 120b) exposed by the protective layer 160a.

As shown in FIG1 , each welding material 180 further includes a welding layer 180s and an electrode layer 180e, and the electrode layer 180e is located between the welding layer 180s and the first electrode 120a (or the first electrode 120b). The welding layer 180s and the electrode layer 180e have an interface 180i, and the protective layer 160a located on the first surface 100f has a top surface 160s. In this embodiment, the interface 180i protrudes from the top surface 160s, and the distance D2 between the interface 180i and the top surface 160s is greater than 5μm, but the present disclosure is not limited thereto. In other embodiments, the distance D2 between the interface 180i and the top surface 160s may also be less than 5μm. The material of the welding layer 180s in the welding material 180 may include, for example, nickel or tin, and the material of the electrode layer 180e may include copper.

2 , the current sensing resistor 10 further includes a trimmed resistance region 250. In this embodiment, the trimmed resistance region 250 is located on the first electrode 120a and extends to the resistor layer 100, but the present disclosure is not limited thereto. In other embodiments, the number of the trimmed resistance region 250 is not limited to one, but may be more than one, and they may be distributed on the first electrode 120a or the first electrode 120b.

A series of steps from FIG. 3A to FIG. 3D illustrate a method for manufacturing a current sensing resistor according to at least one embodiment of the present disclosure. Referring to FIG. 3A and FIG. 3B , first, a resistor layer 100 is provided, and the resistor layer 100 has a first surface 100f and a second surface 100s. Then, a second electrode 140 is formed on the second surface 100s of the resistor layer 100. On the other hand, two first electrodes (i.e., a first electrode 120a and a first electrode 120b) are formed on the first surface 100f of the resistor layer 100. The first electrode 120a and the first electrode 120b are respectively located at two opposite ends of the first surface 100f, and the region where the second electrode 140 overlaps with the resistor layer 100 spans between the first electrode 120a and the first electrode 120b. In addition, the second electrode 140 partially overlaps with the first electrode 120a and the first electrode 120b.

In this embodiment, the first electrode 120a, the first electrode 120b and the second electrode 140 can be formed by, for example, electroplating. For example, a patterned anti-plating protective layer can be provided on the resistor layer 100 by printing, lamination and lithography, and the anti-plating protective layer can be a photoresist, a removable adhesive film or ink. Then, a metal material, such as copper, is deposited on the resistor layer 100 by electroplating. Finally, the patterned anti-plating protective layer is removed by a stripping solvent or water washing to form the first electrode 120a, the first electrode 120b and the second electrode 140 on the resistor layer 100.

It is particularly noted that in this embodiment, the second electrode 140 is formed first, and then the first electrode 120a and the first electrode 120b are formed. However, the present disclosure is not limited to the above manufacturing sequence. In other words, in other embodiments, the first electrode 120a and the first electrode 120b may be formed first, and then the second electrode 140 is formed.

Referring to FIG. 3B , after forming the second electrode 140, a protective layer 160b may be disposed on the resistor layer 100 by, for example, lamination, printing, or coating. The protective layer 160b is located on the second surface 100s of the resistor layer 100 and covers the second electrode 140. In this embodiment, the protective layer 160b is disposed before forming the first electrode 120a and the first electrode 120b. However, the present disclosure is not limited thereto, and in other embodiments, the protective layer 160b may be disposed after forming the first electrode 120a and the first electrode 120b.

As shown in FIG. 3B , the first electrode 120 a (or the first electrode 120 b ) and a portion of the resistor layer 100 may be removed by laser trimming or mechanical processing to form a trimming region 250 for adjusting resistance to obtain a desired target resistance.

Next, referring to FIG. 3C , after forming the first electrode 120a and the first electrode 120b, a protective layer 160a may be disposed on the resistor layer 100 by, for example, lamination, printing, or coating. The protective layer 160a is located on the first surface 100f of the resistor layer 100 and covers the first electrode 120a and the first electrode 120b. The protective layer 160a exposes the region 120r of the first electrode 120a and the first electrode 120b.

Referring to FIG. 3D , after forming the first electrode 120a and the first electrode 120b (and providing the protective layer 160a), a welding material 180 may be formed on the first electrode 120a and the first electrode 120b respectively by electroplating. The welding material 180 covers the region 120r of the first electrode 120a (and the first electrode 120b) exposed by the protective layer 160a. Specifically, an electrode layer 180e containing copper may be deposited on the first electrode 120a by electroplating. Next, a soldering layer 180s including nickel or tin is deposited on the electrode layer 180e to provide a soldering and bonding function between the current flow sensing resistor 10 and the external circuit board. At this point, the current flow sensing resistor 10 of at least one embodiment of the present disclosure has been basically completed.

In summary, by setting a second electrode with a lower resistivity on one side of the resistor layer, the current tends to pass from one of the first electrodes through the second electrode to reach the other first electrode. In this way, the heat generated by the resistor layer can be dispersed to the first electrodes at both ends, and the heat is conducted to the outside through the first electrodes. In addition, the second electrode located on one side of the resistor layer also provides a heat dissipation path, which helps to improve the overall heat dissipation efficiency.

On the other hand, since the second electrode has provided a relatively low resistance value, it is not necessary to reduce the resistance value of the current flow sensing resistor by increasing the thickness of the resistor layer. Therefore, the present disclosure also helps to reduce the overall thickness of the low resistance current flow sensing resistor.

Although the present invention has been disclosed as above by way of embodiments, it is not intended to limit the present invention. A person having ordinary knowledge in the technical field to which the present invention belongs may make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the attached patent application.

10: Current flow measuring resistor 100: Resistor layer 100f: First surface 100s: Second surface 120a, 120b: First electrode 120r: Region 140: Second electrode 160a, 160b: Protective layer 160s: Top surface 180: Welding material 180e: Electrode layer 180i: Interface 180s: Welding layer 250: Resistor repair area D1, D2: Spacing I: Current path L: Length T: Thickness

The embodiments of the present disclosure can be understood from the following detailed description and the accompanying drawings. It should be noted that various features are not drawn in proportion to the industry practice standards. In fact, for the sake of clarity and understanding in discussion, the sizes of various features can be increased or decreased arbitrarily. Figure 1 shows a cross-sectional view of an inductive flow sensing resistor of an embodiment of the present disclosure. Figure 2 shows a partial three-dimensional view of an inductive flow sensing resistor of an embodiment of the present disclosure. Figures 3A to 3D show cross-sectional views of a method for manufacturing an inductive flow sensing resistor of an embodiment of the present disclosure.

Domestic storage information (please note in the order of storage institution, date, and number) None Foreign storage information (please note in the order of storage country, institution, date, and number) None

10: Inductive flow measuring resistance

100: Resistor layer

100f: first surface

100s: Second surface

120a, 120b: first electrode

120r: Area

140: Second electrode

160a,160b: Protective layer

160s: top surface

180: Welding materials

180e:Electrode layer

180i: Interface

180s: welding layer

D1,D2: Spacing

I: Current path

L: Length

T:Thickness

Claims (5)

A current flow sensing resistor comprises: a resistor layer having a first surface and a second surface, wherein the first surface and the second surface are respectively located on opposite sides of the resistor layer; two first electrodes are located on the first surface of the resistor layer and are respectively located at opposite ends of the first surface; a second electrode is located on the second surface of the resistor layer, wherein the overlapping area of the second electrode and the resistor layer spans between the first electrodes, and the second electrode overlaps with at least a portion of each of the first electrodes; two protective layers are respectively located on the first surface and the second surface of the resistor layer, and the first electrodes and the second electrode are located between the protective layers, wherein the second electrode located on the first surface The protective layer covers the first electrodes and exposes a region of the first electrodes respectively, and the protective layer located on the second surface covers the second electrode; two welding materials are respectively located on the first electrodes and electrically connected to the first electrodes, wherein the welding materials cover the region of the first electrodes exposed by the protective layer, wherein each of the welding materials comprises: a welding layer; and an electrode layer, located between the welding layer and one of the first electrodes, wherein the welding layer and the electrode layer have an interface, and the protective layer located on the first surface has a top surface, wherein the interface protrudes from the top surface, and the distance between the interface and the top surface is 5μm or more. The current sensing resistor as described in claim 1, wherein the resistivity of the second electrode is less than the resistivity of the resistor layer. The current flow sensing resistor as described in claim 1 further comprises: a resistance repairing region located on the first electrodes and extending to the resistance layer. A method for manufacturing an inductive sensing resistor comprises: providing a resistor layer, wherein the resistor layer has a first surface and a second surface; forming two first electrodes on the first surface of the resistor layer, wherein the first electrodes are respectively located at two opposite ends of the first surface; forming a second electrode on the second surface of the resistor layer, wherein the region where the second electrode overlaps with the resistor layer spans between the first electrodes, and the second electrode overlaps with at least a portion of each of the first electrodes; After forming the first electrodes, a protective layer is disposed on the resistor layer, wherein the protective layer is located on the first surface of the resistor layer and covers the first electrodes, wherein the protective layer exposes a region of the first electrodes; after forming the first electrodes, a welding material is formed on the first electrodes respectively, and the welding materials cover the region of the first electrodes exposed by the protective layer, wherein forming the welding material comprises: depositing an electrode layer on one of the first electrodes; and depositing a welding layer on the electrode layer. The method described in claim 4 further comprises: after forming the second electrode, providing a protective layer on the resistor layer, wherein the protective layer is located on the second surface of the resistor layer and covers the second electrode.

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