Resistor and manufacturing method thereof

A resistor and a manufacturing method thereof are disclosed. Since a ceramic tube formed of a ceramic material is used and the ceramic tube is joined to sealing electrodes by use of brazing rings, joining strength and durability of the resistor are considerably improved. The resistor may be stably used at a high voltage due to excellent heat dissipation characteristics thereof.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a resistor and a manufacturing method thereof, and more particularly to a resistor having improved joining strength and durability, since a ceramic tube formed of a ceramic material is used and the ceramic tube is joined to sealing electrodes by use of brazing rings, and stably used at a high voltage due to excellent heat dissipation characteristics, and a manufacturing method thereof.

Description of the Related Art

In general, a resistor that is used in a circuit to restrict the flow of current causing a drop in voltage is a device consuming power to produce heat. A maximum power consumed thereby is set as the rated power. Resistors commonly used in electronic circuits have a power rating of about ⅛ to about ½ W, and resistors with a high power rating are used in power supplies.

FIG. 10is a sectional view illustrating a conventional resistor. The conventional resistor includes a coil2wound on a cylindrical body1formed of glass fiber and having a predetermined length, cap bodies3disposed at both ends of the cylindrical body1provided with the coil2wound thereon and formed of a conductive material, and lead wires4connected to the cap bodies3. In addition, both ends of the coil2are electrically connected to each of the cap bodies3.

Then, the coil2and the cylindrical body1are coated with various colored synthetic resins indicating predetermined standards, and the resistor is commercialized. The resistor having the above described structure may be used in an electronic circuit when the lead wires4are inserted into slots of a printed circuit board in a fixed state.

Meanwhile, Korean Patent Application Publication No. 1999-0040562 discloses a coated parallel resistor including a first coil and a second coil.

However, power greater than the rated power supplied to conventional resistors generally causes deterioration in the resistors due to heat, thereby causing damage thereto. In particular, carbon resistors are easily damaged by heat, brining damages to electronic circuits. In addition, as ambient temperature of the resistor increases, heating of a resistive body needs to be reduced. Thus, the resistor needs to be used at a lower power than the rated power. As resistance increases, noise generated in the resistive body increases. In order to obtain high resistance while generating low noise, a fine coil needs to be wound or a thin metal film needs to be. However, in this case, a cut-off may easily occur.

SUMMARY OF THE INVENTION

Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a resistor having improved joining strength and durability, since a ceramic tube formed of a ceramic material is used, and the ceramic tube is joined to sealing electrodes by use of brazing rings, and stably used at a high voltage, and a method of manufacturing the resistor.

It is another object of the present invention to provide a resistor having excellent heat dissipation characteristics and stably used at a high rated voltage by reducing influence by ambient temperature, since heat generated in the resistive element is dissipated via sealing electrodes, the resistive element is disposed in the sealed ceramic tube, and the resistive element is surrounded by air or an inert gas filled in the ceramic tube, and a method of manufacturing the resistor.

It is a further object of the present invention to provide a resistor capable of improving wetting properties and joining strength of brazing rings by forming a plating layer at brazing junction regions, and a method of manufacturing the resistor.

In accordance with the present invention, the above and other objects can be accomplished by the provision of a resistor including a ceramic tube, a pair of sealing electrodes disposed at both ends of the ceramic tube and respectively electrically connected to lead wires, a resistive element accommodated in the ceramic tube to be electrically connected to the sealing electrodes and including a resistive body, terminal electrodes disposed at both ends of the resistive body, and a resistive layer electrically connected to the terminal electrodes, and brazing rings sealing between the ceramic tube and each of the sealing electrodes. In this regard, the ceramic tube is joined to the sealing electrodes by melting of the brazing rings.

The resistive body may have a rod shape and may be formed of a ceramic material, and the resistive layer may be formed by winding a coil on the outer circumferential surface of the resistive body or by forming a conductive layer on the outer circumferential surface of the resistive body and spirally cutting the conductive layer.

The brazing ring may include an alloy including copper (Cu), silver (Ag), and zinc (Zn).

Each of the sealing electrodes may include a contact portion protruding toward the inside of the ceramic tube to be inserted into the ceramic tube and contact the resistive element and a junction portion joined to the brazing ring.

An outer surface of the brazing ring may be disposed at the same line of an outer surface of the ceramic tube, and an inner surface of the brazing ring may be disposed to extend toward the inside of the ceramic tube to a portion farther inward than an inner edge of the ceramic tube.

The brazing ring may include an outer circumferential portion joined to the ceramic tube and an inner circumferential portion joined to an end portion of the resistive element.

The resistor may further include brazing members melted between the contact portion and each of the terminal electrodes to join the contact portion to the terminal electrode.

The resistor may further include a plating layer including nickel (Ni) or titanium (Ti) disposed on at least one selected from the group consisting of the contact portion, the junction portion, and the terminal electrode to improve joining strength by melting of the brazing ring or the brazing member.

In accordance with an aspect of the present invention, the above and other objects can be accomplished by the provision of a method of manufacturing a resistor including preparing the first sealing electrode, sequentially stacking the first brazing ring and the ceramic tube on the first sealing electrode, inserting the resistive element into the ceramic tube, sequentially stacking the second brazing ring and the second sealing electrode on the ceramic tube, and sealing between the ceramic tube and each of the first and second sealing electrodes by placing the resultant structure in a chamber and melting the first and second brazing rings. In this regard, the resistor includes a ceramic tube accommodating a resistive element, first and second sealing electrodes disposed at both ends of the ceramic tube to be connected to the resistive element, and first and second brazing rings joining the ceramic tube to each of the sealing electrodes.

Each of the first and second sealing electrodes may include a contact portion protruding toward the inside of the ceramic tube to be inserted into the ceramic tube and contact the resistive element and a junction portion joined to each of the first and second brazing rings, and each of the first and second brazing rings may be inserted to the junction portion of each of the first and second sealing electrodes.

The first and second brazing rings may be formed of Ag25CuZnSn, an alloy including silver (Ag), copper (Cu), zinc (Zn), and tin (Sn), and the sealing may be performed by melting the first and second brazing rings at a temperature of 500 to 850.

A plating layer including nickel (Ni) or titanium (Ti) may further be disposed on the surface of the junction portion to improve joining strength by melting of the first and second brazing rings.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention will be described with reference to the accompanying drawings.

When it is determined that a detailed description of the related art may unnecessarily obscure the subject matter of the present invention, the description thereof will be omitted. Further, the following terms, which are defined in consideration of functions of the present invention, may be altered depending on the user's intentions or judicial precedents. Therefore, the meaning of each term should be interpreted based on the entire disclosure of the specification.

FIGS. 1A and 1Bare sectional views illustrating resistive elements according to the present invention.FIG. 2is a sectional view illustrating a resistor according to a first embodiment of the present invention.FIG. 3is an exploded sectional view illustrating the resistor according to the first embodiment of the present invention.

As illustrated inFIGS. 1A to 3, a resistor100according to the present invention generally includes a ceramic tube120, sealing electrodes130, a resistive element110, and brazing rings150.

Specifically, the resistor100according to the present invention includes a ceramic tube120, a pair of sealing electrodes130, which are disposed at both ends of the ceramic tube120and respectively electrically connected to lead wires170, a resistive element110, which is accommodated in the ceramic tube120, which is electrically connected to the sealing electrodes130, and has a resistant layer115, and brazing rings150which seal between the ceramic tube120and each of the sealing electrodes130.

Referring toFIG. 1A, the resistive element110according to the present invention may include a resistive body111, terminal electrodes117disposed at both ends of the resistive body111, and a resistive layer115electrically connected to the terminal electrodes117and having a predetermined resistance.

The resistive body111may have a rod shape and may be formed of a ceramic material such as alumina. In addition, the resistive layer115is formed on the outer circumferential surface of the resistive body111.

The resistive layer115may be formed by spirally winding a coil on the outer circumferential surface of the resistive body111.

In addition, the resistive layer115may be formed of copper (Cu), silver (Ag), an copper-silver alloy, a nickel-copper alloy, a nickel-iron alloy, copper surface-coated with silver, iron (Fe), chromium (Cr), and an iron-based alloy containing nickel as a main component.

For example, the terminal electrodes117may be formed of a copper alloy. The terminal electrodes117may be disposed at both ends of the resistive body111to electrically connect each of the sealing electrodes130with the resistive element110.

In addition, referring toFIG. 1B, a resistive element110baccording to the present invention may include a resistive body111, terminal electrodes177disposed at both ends of the resistive body111, and a resistive layer115belectrically connected to the terminal electrodes117and having a predetermined resistance.

The resistive layer115bmay be formed by forming a conductive layer on the outer circumferential surface of the resistive body111and spirally cutting the conductive layer.

As described above, the resistive elements110and100aaccording to the present invention may be formed in various shapes, taking into consideration use and characteristics of products.

The ceramic tube120according to the present invention has a cylindrical shape and is formed of a ceramic material. The cylindrical ceramic tube120is provided with the sealing electrodes130at both ends. In addition, both ends of the ceramic tube120are joined to each of the sealing electrodes130by brazing junctions.

The sealing electrodes130are installed at both ends of the ceramic tube120as described above to be respectively electrically connected to the lead wires170.

In addition, for example, the sealing electrodes130may be formed of a copper alloy.

For example, each of the sealing electrodes130may include a contact portion133that protrudes toward the inside of the ceramic tube120to be inserted into the ceramic tube120and contact the resistive element110and a junction portion131joined to the brazing ring150.

Since the contact portion133of the sealing electrode130protrudes inward, the sealing electrode130may be efficiently assembled with the brazing ring150or the ceramic tube120. Since the resistive element110contained in the ceramic tube120may be pressed during a brazing process, electrical connection between the sealing electrode130and the contact portion133may be improved.

The brazing ring150according to the present invention, as a filler metal, is melted between the ceramic tube120and each of the sealing electrodes130which are base metals to join the ceramic tube120to the sealing electrodes130in a sealed state.

For example, the brazing ring150may be formed of an alloy including copper (Cu), silver (Ag), and zinc (Zn).

In addition, the brazing process is performed at a temperature higher than a melting point of the brazing ring150, as a filler metal, and lower than melting points of the ceramic tube120and the sealing electrodes130, as base metals.

Wetting properties that indicate the degree of affinity between a filler metal and a base metal are an important factor in a brazing junction. That is, when the brazing ring has poor wetting properties with the ceramic tube120and the sealing electrodes130, a junction therebetween cannot be formed. Thus, according to the present invention, a ceramic material having excellent wetting properties with the filler metal is used to form the ceramic tube120that accommodates the resistive element110instead of a glass material having poor wetting properties with the filler metal.

In addition, the brazing junction using the brazing ring150may provide high joining strength since the brazing ring150generates capillary action on the surfaces of the ceramic tube120and the sealing electrodes130while being melted and provide excellent resistance against impact such as vibration or the like.

Meanwhile, an outer surface151of the brazing ring150is disposed at the same level of an outer surface of the ceramic tube120, and an inner surface152of the brazing ring150is disposed to extend toward the inside of the ceramic tube120to a portion farther inward than an inner edge of the ceramic tube120.

As described above, the resistor100according to the present invention may have excellent durability and may be stably used at a high temperature since the ceramic tube120is formed of a ceramic material with excellent mechanical strength, and the ceramic tube120is joined to each the sealing electrodes130by use of the brazing rings.

FIG. 4is a sectional view illustrating a resistor100aaccording to a second embodiment of the present invention.

Referring toFIG. 4, the resistor100aaccording to the present invention may further include brazing members160that join each of the contact portions133to each of the terminal electrodes117.

For example, the brazing member160may have a plate shape and may be formed of an alloy including copper (Cu), silver (Ag), and zinc (Zn).

The brazing member160is melted between the contact portion133and the terminal electrode117to join the contact portion133to the terminal electrode117in the same manner as the brazing ring150.

Thus, the resistive element110may be more firmly joined to the sealing electrodes130by use of the brazing members160, thereby improving durability of the resistor100a.

FIG. 5is a sectional view illustrating a resistor100baccording to a third embodiment of the present invention.

Referring toFIG. 5, each of the brazing rings150aof the resistor100baccording to the present invention may be configured to be joined to both of the ceramic tube120and the resistive element110.

That is, the brazing ring150amay include an outer portion153that is joined to an end of the ceramic tube120and an inner portion154that is joined to an end portion of the resistive element110, particularly, the terminal electrode117.

Thus, the brazing ring150amay have a thickness identical to or greater than that of the contact portion133a.This is because, when the thickness of the brazing ring150ais greater than that of the contact portion133a,the brazing ring150amay be joined to both the ceramic tube120and the terminal electrode117after being melted.

In addition, the inner portion154of the brazing ring150amay be formed to extend inward to a portion farther inward than that of the brazing ring150ofFIG. 2, and the contact portion133amay have a narrower width than the contact portion133ofFIG. 2.

FIG. 6is a sectional view illustrating a resistor100caccording to a fourth embodiment of the present invention.

Referring toFIG. 6, the resistor100caccording to the present invention may further include a plating layer180in order to improve wetting properties of the brazing ring150or the brazing member160with base metals.

In particular, the plating layer180(181,183, and185) is formed on at least one of the contact portion133, the junction portion131, and the terminal electrode117to improve joining strength of the brazing ring150or the brazing member160by a melting process.

In addition, the plating layer180may include nickel (Ni) or titanium (Ti), and may be formed of, for example, a compound such as Ni3P.

FIGS. 7A and 7Bare sectional views illustrating a resistor100daccording to a fifth embodiment of the present invention.

Referring toFIGS. 7A and 7B, each of the sealing electrodes130baccording to the present invention may have a flat panel shape without having a protruding contact portion which is different from the sealing electrodes illustrated inFIGS. 1 to 6.

In addition, a brazing ring150bmay have a flat panel shape so as to be joined to one end of the ceramic tube120and one terminal electrode117at the same time (FIG. 7A).

In addition, a brazing ring150cmay have a hollow ring shape such that the sealing electrode130bdirectly contacts the terminal electrode117(FIG. 7B).

Hereinafter, a method of manufacturing a resistor according to the present invention will be described in detail.

FIGS. 8A to 8Fare sectional views for describing a method of manufacturing a resistor100according an embodiment of the present invention.

As described above, the resistor100manufactured by the method according to the present invention may include a ceramic tube120in which a resistive element110is accommodated, first and second sealing electrodes130and135respectively inserted into both ends of the ceramic tube120to be connected to the resistive element110, and first and second brazing rings150and155respectively joining the ceramic tube120to each of the first and second sealing electrodes130and135.

First, referring toFIG. 8A, the first sealing electrode130is formed in operation S1. The first sealing electrode130includes a contact portion133that protrudes toward the inside of the ceramic tube120to be inserted into the ceramic tube120and contact the resistive element110and a junction portion131joined to the first brazing ring150.

Then, referring toFIG. 8B, the first brazing ring150and the ceramic tube120are sequentially stacked on the first sealing electrode130in operation S2.

The first brazing ring150is mounted on the junction portion131of the first sealing electrode130, and the ceramic tube120is disposed on the first brazing ring150.

In this regard, the resistive element110may include a resistive body111, first and second terminal electrodes117and117adisposed at both ends of the resistive body111, and a resistive layer115electrically connected to the first and second terminal electrodes117and117a.

The first terminal electrode117of the inserted resistive element110is disposed on an upper surface of the contact portion133of the first sealing electrode130. A gap G or space may be formed between an inner surface of the first terminal electrode117and the resistive body111. The gap G or space may be eliminated by pressure applied thereto when the second sealing electrode135is joined thereto which will be described later and by a brazing process described in operation S5. The gap G or space may be naturally or artificially formed during assembly of the resistive element110.

Then, referring toFIG. 8D, the second brazing ring155and the second sealing electrode135are sequentially stacked on the ceramic tube120in operation S4.

The resistor100is assembled through operation S1 to operation S4 to be a state before the brazing junction.

Then, the resistor100that has undergone operation S1 to operation S4 is placed in a chamber C, and the ceramic tube120and each of the first and second sealing electrodes130and135are sealed by melting the first and second brazing rings150and155in operation S5.

Operation S5 may be performed in the chamber C under an inert gas atmosphere, and the inside of the sealed ceramic tube120is filled with an inert gas. In addition, the inert gas functions to prevent oxidation of the resistive element110and improve durability.

The resistor100is vertically added to the chamber C in a longitudinal direction (FIG. 8E). The chamber C is heated to melt the first and second brazing rings150and155, thereby completing junction (FIG. 8F).

In this regard, the chamber C is heated at a temperature less than melting points of the first and second sealing electrodes130and135and the ceramic tube120which are base metals in order to prevent deformation of the base metals. The heating temperature may be adjusted in the range of 500 to 850 according to the material of the first and second brazing rings150and155. For example, when the first and second brazing rings150and155are formed of an alloy including copper (Cu) and silver (Ag), e.g., Ag25Cu, the chamber C may be heated to a temperature of 800 to 850. In this regard, the resistive layer115may be formed of a material that is not blown after brazing, for example, a nickel-copper alloy and a nickel-iron alloy.

In addition, when the first and second brazing rings150and155are formed of an alloy including silver (Ag), copper (Cu), zinc (Zn), and tin (Sn), e.g., Ag56CuZnSn, the brazing is performed at a temperature of 600 to 650. Thus, the resistive layer115may be also formed of copper (Cu), silver (Ag), and a silver-copper alloy which are blown at a temperature of 800 to 850 as well as the nickel-copper alloy and the nickel-iron alloy.

That is, by reducing the brazing temperature where the first and second brazing rings150and155are melted from the range of 800 to 850 to the range of 600 to 650, main components of conventional resistive layers such as copper (Cu), silver (Ag), a silver-copper alloy, and the like may be used. Accordingly, there is a wide range of choices in designing resistors. In addition, at a temperature of 800 or greater, the fusible element115may be deteriorated by heat even though it is not blown out. However, when the brazing process is performed at a relatively lower temperature of 600 to 650,degradation of performance and quality by heat may be reduced.

Meanwhile, the heated first and second brazing rings150and155are melted to join the surfaces of base metals in a sealed state through capillary action, thereby decreasing in thickness. Then, lead wires are connected to outer surfaces of the sealing electrodes, thereby completing manufacture of the resistor100.

Meanwhile,FIG. 9is a sectional view illustrating a resistor100aaccording to the present invention mounted on a surface of a substrate.

Referring toFIG. 9, lead wires may be omitted, and the sealing electrodes130may be joined to solder balls in the resistor100aaccording to the present invention. Thus, the resistor100amay be used as a surface mount device (SMD).

As described above, according to the method of manufacturing the resistor, a ceramic tube formed of a ceramic material with excellent mechanical strength is used, and the ceramic tube is joined to the sealing electrodes by use of the brazing rings, and thus joining strength and durability of the resistor are improved. Thus, the resistor may be stably used at a high voltage.

In addition, since heat generated in the resistive element is dissipated via the sealing electrodes, the resistive element is disposed in the sealed ceramic tube, and the restive element is surrounded by air or an inert gas filled in the ceramic tube, influence of ambient temperature on the resistor is reduced. As such, since the resistor according to the present invention has excellent heat dissipation characteristics, it may be used at a high rated voltage.

In addition, by reducing the temperature of the brazing process to the range of 600 to 650, the resistive layer is not blown out even though conventional materials are used. A resistor having a relatively thin and long resistive layer and a high resistance may be manufactured.

As a result, according to the resistor and the manufacturing method thereof according to the present invention, a resistor stably used at a high voltage since durability is improved by the brazing process and heat dissipation characteristics are improved may be manufactured.

As is apparent from the above description, according to the resistor and the manufacturing method thereof according to the present invention, the resistor may have improved joining strength and durability and may be stably used at a high temperature since the ceramic tube formed of a ceramic material is used, and the ceramic tube is joined to the sealing electrodes by use of the brazing rings.

In addition, according to the resistor and the manufacturing method thereof according to the present invention, heat generated in the resistive element is dissipated via the sealing electrodes, the resistive element is disposed in the sealed ceramic tube, and the resistive element is surrounded by air or an inert gas filled in the ceramic tube, and thus influence of ambient temperature on the resistor may be reduced. Accordingly, the resistor may have excellent heat dissipation characteristics and may be used at a high rated voltage.

In addition, according to the resistor and the manufacturing method thereof according to the present invention, a plating layer is formed at brazing junction regions, wetting properties and joining strength of the brazing rings may further be improved.