JP2001093704A - Chip thermistor and method for manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chip thermistor where resistance adjustment of high precision is made easy, and its manufacturing method. SOLUTION: A chip thermistor 10 is provided with a thermistor element assembly 20, where prism parts 21 at both ends and a columnar part 22 sandwiched by the prism parts 21 are collectively formed in an unified body, terminal electrodes 30 which are formed from the prism parts 21 of the thermistor element assembly 20 to the columnar part 22 and are not connected electrically with each other, and an outer seath 40 formed around the columnar part 22. Resistance characteristic can be adjusted by adjusting the dimensions of the columnar part 22 and the prism parts 21 and adjusting the gap between the pair of the terminal electrodes 30. Since adjustment is enabled after the thermistor element assembly is manufactured, adjustment of resistance is easily enabled with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip-type thermistor whose resistance value changes with temperature and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, a laminated chip thermistor as shown in FIG. 16 is known as this type of chip thermistor. Hereinafter, this laminated chip thermistor is shown in FIG.
This will be described with reference to FIG. FIG. 16 is a perspective view of a conventional multilayer chip thermistor with a part cut away.

The laminated chip thermistor 100 has a rectangular parallelepiped thermistor element 103 formed by laminating a plurality of ceramic layers 101 on which an internal electrode 102 is formed, and the internal electrode 10 provided at both ends of the thermistor element 103.
2 and a terminal electrode 104 for connection. here,
As a material of the ceramic layer 101, a ceramic powder for a thermistor containing manganese oxide or cobalt oxide as a main material is used. Thus, the thermistor element 103 has a temperature-dependent resistance value.

The laminated chip thermistor 100 forms a green sheet from the ceramic powder for the thermistor, and applies a conductive paste to be the internal electrode 102 to the green sheet. Next, a plurality of the green sheets are laminated and pressed. Next, the sheet laminate is cut to obtain a laminate having a unit component size. Next, the laminated body is fired at a predetermined temperature to obtain a ceramic thermistor body 103 in which the internal electrodes are embedded. Finally, by forming a terminal electrode on the element body 103,
The multilayer chip thermistor 100 is obtained.

[0005]

However, it has been difficult for conventional multilayer chip thermistors to make adjustments to obtain desired resistance characteristics. That is, in the conventional multilayer chip thermistor, when the conductive paste is applied to the green sheet, the shape and dimensions of the green paste are adjusted to change the shape of the internal electrode 102, thereby adjusting the resistance characteristics of the thermistor. . However, with this method, the resistance value could not be adjusted after obtaining the thermistor body 103 as a sintered body. For this reason, it has been difficult to obtain a chip thermistor having desired resistance characteristics with high accuracy.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a chip thermistor capable of easily performing high-precision resistance adjustment and a method of manufacturing the same.

[0007]

In order to achieve the above object, in claim 1, both ends form a prism, and a central portion sandwiched between the both ends has a cylindrical or prismatic shape having a smaller diameter than both ends. And a pair of terminal electrodes made of a metal film that covers the prism portions at both ends of the thermistor body and is formed from the prism portion to the center portion and is nonconductive to each other. We propose a chip thermistor characterized by

According to the present invention, a desired resistance characteristic can be obtained by adjusting the dimensions of the cylindrical portion and the prism portion of the thermistor body. Further, the resistance characteristic can be adjusted by adjusting the distance between the pair of metal films formed from both ends of the thermistor body to the center. Therefore, since the adjustment after the thermistor body is manufactured is possible, the adjustment of the resistance characteristic can be performed easily and with high accuracy. Further, since both ends of the thermistor element are prismatic, they do not roll even when the chip thermistor is mounted on the circuit board on which it is mounted. Therefore, the chip thermistor of the present invention is suitable for surface mounting.

According to a second aspect of the present invention, there is provided the chip thermistor according to the first aspect, wherein an outer shape is formed at a central portion of the thermistor body so that an end portion is defined by prisms at both ends of the thermistor body. The present invention proposes a device having the formed exterior.

According to the present invention, since the sheath is formed at the center of the thermistor body, it is possible to prevent erosion and deterioration of the thermistor body due to invasion of moisture and the like. Further, since the external shape is a prismatic shape, mounting is easy. In other words, it is easy to transport components by the suction head of the component mounting machine.

According to a third aspect of the present invention, in the chip thermistor according to the second aspect, the metal film has an inner layer formed from a prism portion to a central portion, and the outer surface is formed on a surface of the inner layer. And an outer layer formed in a non-existing portion.

According to the present invention, the resistance characteristics can be adjusted by adjusting the width between the metal films by the inner layer of the metal film. on the other hand,
The outer layer of the metal film is soldered to a circuit board as a terminal electrode. Therefore, a material suitable for adjusting the resistance characteristics can be used for the inner layer of the metal film, and a material suitable for mounting can be used for the outer layer.

According to a fourth aspect of the present invention, in the chip thermistor according to any one of the first to third aspects, at least a part of a central portion of the thermistor body that is not covered with the metal film is removed. We propose one that is characterized.

According to a fifth aspect of the present invention, in the chip thermistor according to any one of the first to fourth aspects, the pair of metal films are formed such that the distance between them is non-uniform in the circumferential direction of the thermistor body. Are proposed.

According to the third or fourth aspect of the invention, the adjustment of the resistance characteristic can be performed easily and reliably.

According to a sixth aspect of the present invention, the step of grinding the central portion of the prism-shaped thermistor body into a column or a prism having a smaller diameter than both ends, and covering the ground thermistor body with the prism portions at both ends. And forming a pair of terminal electrodes formed of metal films that are non-conductive from each other and are formed from the prism portion to the central portion, and a method for manufacturing a chip thermistor is provided.

According to the present invention, the chip thermistor according to claim 1 can be reliably manufactured. That is, in the grinding process of the prismatic thermistor body, a desired resistance characteristic can be obtained by adjusting the grinding width, the grinding depth, and the like. Also, by adjusting the shape of the pair of metal films, the distance between the metal films, and the like, desired resistance characteristics can be obtained. Therefore, since the adjustment after the thermistor body is manufactured is possible, the adjustment of the resistance characteristic can be performed easily and with high accuracy.

According to a seventh aspect of the present invention, in the method of manufacturing a chip thermistor according to the sixth aspect, the terminal electrode forming step includes a step of forming a metal film so as to cover the entire surface of the ground thermistor body. As the metal film is divided in the length direction of the thermistor body and each becomes a terminal electrode,
Removing at least a part of the metal film formed at the center of the thermistor body.

According to the present invention, the metal film having the shape described in the first aspect can be easily formed. That is, it is relatively difficult to separately form metal films at both ends of the thermistor body after the grinding step so as to be non-conductive. On the other hand, the process of forming a metal film so as to cover the entire surface of the thermistor body and the process of removing the metal film at the center of the thermistor to divide the metal film are both relatively easy to realize. . Therefore,
A metal film can be easily formed. Further, since the metal film is once formed on the entire surface of the thermistor body, it is possible to prevent erosion and deterioration of the thermistor body due to invasion of moisture or the like.

According to an eighth aspect of the present invention, in the method of manufacturing a chip thermistor according to the seventh aspect, in the metal film removing step, the chip thermistor has a desired resistance value while maintaining a resistance value between the pair of metal films. The following is a proposal of a method characterized by removing a metal film.

According to the present invention, a chip thermistor having a desired resistance characteristic can be easily and accurately manufactured. That is, the removal amount of the metal film may be adjusted so that the chip thermistor has a desired resistance value.

According to a ninth aspect of the present invention, in the method for manufacturing a chip thermistor according to any one of the seventh and eighth aspects,
In the metal film removing step, a method is proposed in which the thermistor body is ground together with the removal of the metal film.

According to the present invention, by simultaneously grinding the thermistor body, the adjustment range of the resistance characteristic can be expanded to a range where adjustment is impossible only by removing the metal film.

According to a tenth aspect, in the method of manufacturing a chip thermistor according to any one of the sixth to ninth aspects,
It is proposed that a step of activating the surface of the thermistor body is provided as a pre-process before the metal film forming process.

According to the present invention, since the surface of the thermistor body is activated during the formation of the metal film, the metal film has good adsorbability. Therefore, erosion and deterioration of the thermistor body due to intrusion of moisture and the like can be prevented. Further, peeling of the metal film or the like can be prevented.

According to an eleventh aspect of the present invention, in the method of manufacturing a chip thermistor according to the sixth aspect, in the terminal electrode forming step, a metal film is formed by plating an annular mask at a central portion of the thermistor body and then plating. We propose one that is characterized.

According to the present invention, a metal film having the shape described in the first aspect can be easily formed.

Further, in claim 12, claims 6 to 11
A method for manufacturing a chip thermistor according to any one of the preceding claims, further comprising a step of adjusting a resistance value by trimming a metal film.

According to the present invention, fine adjustment of the resistance characteristics of the chip thermistor can be performed easily and reliably by trimming the metal film.

Furthermore, in claim 13, claims 6 to 12
The method for manufacturing a chip thermistor according to any one of the preceding claims, wherein after the terminal electrode forming step, the center of the thermistor body is formed so that the external shape becomes a prismatic shape whose ends are defined by prismatic portions at both ends of the thermistor body. The present invention proposes a device having a step of forming an exterior in a part.

According to the present invention, since the exterior is formed at the central portion where the thermistor body is exposed, it is possible to prevent erosion and deterioration of the thermistor body due to invasion of moisture and the like.
Further, since the external shape is a prismatic shape, mounting is easy. In other words, it is easy to transport components by the suction head of the component mounting machine.

According to a fourteenth aspect of the present invention, in the method of manufacturing a chip thermistor according to the thirteenth aspect, after the outer package forming step, the metal films exposed at both ends of the thermistor body are subjected to a plating process so that the metal film is formed. The present invention proposes a method including a step of forming a multilayer structure.

According to the present invention, the surface of the metal film can be formed of a material suitable for mounting, and the inner layer of the metal film has good adsorbability to the thermistor body and is suitable for adjusting resistance characteristics. It can be formed of a material. Therefore, both ease of resistance adjustment and mountability can be realized.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A chip thermistor according to a first embodiment of the present invention is shown in FIGS.
This will be described with reference to FIG. FIG. 1 is an external perspective view of the chip thermistor according to the first embodiment, and FIG. 2 is a sectional view of the chip thermistor according to the first embodiment.

The chip thermistor 10 includes a thermistor body 20, a pair of terminal electrodes 30 formed at both ends of the thermistor body 20, and an exterior 40 formed at the center of the thermistor body 20. ing.

The thermistor body 20 is made of Mn, Co, N
It is made of a ceramic sintered body whose main component is an oxide of a transition metal such as i, Fe, or Cu. The thermistor element body 20 is formed by integrally forming a regular square prism 21 formed at both ends and a cylindrical cylinder 22 formed at the center between a pair of prisms 21. Prism part 21 and cylinder part 22
Are arranged coaxially with each other. Further, the pair of prism portions 21 have a cross-sectional shape orthogonal to the longitudinal direction of the thermistor element body 20 and a length in the longitudinal direction which are the same. Further, the pair of prism portions 21 are formed such that the four side surfaces are arranged on the same plane. In addition, the cylindrical portion 22
The diameter of the cross section is formed smaller than the diameter of a circle inscribed in the cross section of the prism portion 21.

The terminal electrode 30 is made of a metal film having a multilayer structure. In the present embodiment, the terminal electrode 30 includes a first layer 31, a second layer 32,
The third layer 33 is formed. Each of the layers 31 to 33 is made of a conductive metal thin film. The first layer 31 that is in close contact with the thermistor body 31 preferably has good electrical characteristics. For example, the first layer 31 is made of a base metal such as Cu, Al, or Ni or an alloy thereof, or a noble metal such as Au or Ag or an alloy thereof. The second layer 32 is preferably one that can protect against solder erosion and the like. For example, the second layer 32 is made of C
base metals such as u, Al, Ni or alloys thereof, or
It is made of a noble metal such as Au or an alloy thereof. Terminal electrode 3
The third layer 33, which is the surface layer of No. 0, preferably has good mountability by soldering or the like. For example, it is a Sn alloy. In the present embodiment, Cu is used for the first layer 31, Ni is used for the second layer 32, and Sn alloy is used for the third layer 33.

The first layer 31 covers the prism portion 21 of the thermistor element body 20 and, from the prism portion 21, forms the cylindrical portion 2.
2 is formed over the entire circumference. The first layers 31 of the terminal electrodes 30 formed at both ends of the thermistor body 20 are formed at predetermined intervals D in the cylindrical portion 22 so as to be non-conductive. The distance D between the pair of first layers 31
Is constant in the circumferential direction of the cylindrical portion 22. The edge of the first layer 31 in the cylindrical portion 22 is arranged on a cross section orthogonal to the longitudinal direction of the thermistor body 20.

The second layer 32 is formed on the first layer 31 so as to cover the prism 21 of the thermistor body 20. Further, the third layer 33 is formed so as to cover the entire surface of the second layer 32.

The outer case 40 is made of a resin material such as epoxy. The exterior 40 is arranged around the cylindrical portion 22 of the thermistor body 20. Therefore, the exterior 40 covers the portion of the first layer 31 formed on the cylindrical portion 22 and the thermistor body 22 exposed between the pair of first layers 31. The exterior 40 is formed such that the outer shape of the chip thermistor 10 has a prism shape defined by the prism portions 21 at both ends. That is, the surface of the exterior 40 is
It is substantially flush with each side surface of the prism 21. Due to the exterior 40, only the third layer 33 of the terminal electrode 30 is exposed on the surface.

Next, a preferred method of manufacturing the chip thermistor 10 will be described with reference to FIGS.

First, as shown in FIG. 3 (a), a material rod 50 having a square cross section made of an unfired ceramic material obtained by a method such as extrusion forming is prepared, and is provided with a predetermined length corresponding to the component dimensions. The unit base material 52 is obtained by cutting to dimensions. Alternatively, as shown in FIG. 3B, a material sheet 51 of a predetermined thickness made of the same material obtained by a method such as coating is prepared, and cut into width and length dimensions corresponding to the part dimensions. The unit base material 52 is obtained.

Next, the longitudinal end face of the unit base material 52 is held by a rotatable support (not shown). Then, as shown in FIG. 4, the central portion of the unit base material 52 is shaved in the circumferential direction by the cutting blade 60 while rotating the unit base material 52 about the axis. As a result, an unfired thermistor body 20a in which the prism portions 21a at both ends and the central column portion 22a are integrally formed is obtained.

Next, the unfired thermistor body 20a is fired at a predetermined temperature and then subjected to barrel polishing. In this barrel polishing, the corners and ridges of the thermistor body 20 are rounded to remove burrs and the like. In addition, the surface is appropriately roughened so that the adhesion of the first layer of the terminal electrode 30 is improved. As described above, the prism portions 21 at both ends as shown in FIG.
Then, a ceramic thermistor body 20 formed integrally with the central cylindrical portion 22 is obtained. By the way, the thermistor body 20 can be obtained even if the order of the cutting step and the firing step is changed.

Next, an activation process is performed on the entire surface of the thermistor body 20. This is to improve the adsorbability of the metal thin film in the plating process described later. In particular,
The thermistor body 20 is immersed in the Pd treatment liquid for a predetermined time to activate the surface. Here, the Pd treatment liquid is, for example, a palladium chloride solution.

Next, C is applied to the entire surface of the thermistor body 20.
u Apply electroless plating. Thereby, as shown in the sectional view of FIG. 6, the plating layer 31a is formed on the entire surface of the thermistor body 20.
Is formed.

Next, both end faces in the longitudinal direction of the thermistor element body 20 are held by a rotatable support (not shown). Then, as shown in FIG. 7, the plating layer 31 a formed near the center of the cylindrical portion 22 is scraped in the circumferential direction by the cutting blade 61 while rotating about the axis of the thermistor body 20. Thus, the plating layer 31a formed on the entire surface of the thermistor body 20 is divided in the longitudinal direction so as to be non-conductive, and the first layer 31a of the terminal electrode 30 described above.
Is formed.

Here, the grinding width of the plating layer 31a, that is, the distance D between the pair of first layers 31 is adjusted so that the finished chip thermistor has a desired resistance characteristic. That is, the resistance characteristic is adjusted by the distance D between the pair of first layers 31. Specifically, the grinding width is adjusted while measuring the resistance value between both ends of the thermistor body 20 using the measuring device 62. When the measuring device 62 shows a desired resistance characteristic, the grinding is finished.

Next, as shown in FIG. 8, the thermistor body 20 is fitted into a support 63 having a recess 64 formed therein (see FIG. 8A). The concave portion 64 is formed in a rectangular parallelepiped shape defined by the prism portions 21 at both ends of the thermistor body 20. For this reason, the thermistor body 20 is
4, a gap is formed only around the cylindrical portion 22. Then, a low-viscosity exterior resin is poured into the gap and dried and solidified (see FIG. 3B). This allows
An exterior 40 is formed around the cylindrical portion 22.

Then, the surface of the first layer 31 on the prism portion 21 is subjected to electrolytic Ni plating to form a second layer 32. Furthermore, electrolytic Sn alloy plating is performed on the surface of the second layer 32 to form a third layer 33. Thus, the chip thermistor 10 shown in FIGS. 1 and 2 is manufactured.

The chip thermistor 10 according to the present embodiment
By changing the dimensions of the prism portion 21 and the central portion 22 of the thermistor body 20, the resistance characteristics can be easily adjusted. That is, when grinding the prismatic unit base material 52, by appropriately changing the grinding width, the grinding depth, and the like,
A chip thermistor having desired resistance characteristics can be easily obtained.

Further, the chip thermistor 10 has first terminals 30 formed on both ends of the thermistor body 20.
By adjusting the interval between the layers 31, the resistance characteristics can be easily adjusted. Therefore, the thermistor body 2
Since the adjustment after the firing of 0 is possible, the adjustment of the resistance characteristics can be performed easily and with high accuracy.

Since the both ends of the thermistor body 20 are prismatic, they do not roll when the chip thermistor 10 is mounted on the circuit board on which it is mounted. Therefore, it is suitable for surface mounting.

Further, since an exterior is formed at the center of the thermistor body 20, erosion and deterioration of the thermistor body 20 due to invasion of moisture or the like can be prevented. Further, since the external shape is a prismatic shape, mounting is easy. In other words, it is easy to transport components by the suction head of the component mounting machine.

Further, the resistance characteristics can be adjusted by the first layer 31 of the terminal electrode 30. On the other hand, the third layer 33 is a surface layer of the terminal electrode 30 and is soldered to a circuit board. Therefore, by using a material suitable for adjusting the resistance characteristics for the first layer 31 and using a material suitable for mounting for the third layer 33, the adjustment of the resistance characteristics is easy and the mountability is good. A simple chip thermistor can be obtained.

Further, in the present embodiment, as a manufacturing process, a step of grinding a central portion of the prism-shaped thermistor body 20a, a step of forming a plating layer 31a on the entire surface of the ground thermistor body 20; Grinding the plated layer 31a formed on the cylindrical portion 22 of the thermistor body 20 into an annular shape. And, this plating layer 31a
In this grinding step, since the grinding is performed while adjusting the resistance characteristics, a chip thermistor having desired resistance characteristics can be easily and reliably manufactured.

Since the entire surface of the thermistor body 20 is activated before the step of forming the plating layer 31a, the adsorptivity of the plating layer 31a is improved. Therefore, the infiltration of moisture into the thermistor element 20 can be prevented, so that the thermistor element 20 can be prevented from being deteriorated or damaged.

In the present embodiment, the central portion is formed in a cylindrical shape by grinding the prismatic unit base material 50 with the cutting blade 60, but the present invention is not limited to this. For example, it may be ground by sand blast, grinder or the like.

In this embodiment, the plating layer 31a formed on the entire surface of the thermistor body 20 is ground by a cutting blade 61 to remove the plating layer 31a.
Although divided into a pair of first layers 31, the present invention is not limited to this. Other mechanical processing such as sandblasting or grinder may be used, or optical processing such as trimming by laser light may be used.

Further, in the present embodiment, the plating layer 31a is removed while measuring to have a desired resistance characteristic. However, after this step, the first layer 31 formed on the cylindrical portion 22 is removed. It is more preferable to finely adjust the resistance characteristics by trimming with a laser or the like. By this trimming, the first layer 31 of the terminal electrode 30 is formed with a notch or a small hole extending in the circumferential direction or the length direction of the cylindrical portion 22 on the surface of the cylindrical portion 22.

(Second Embodiment) A chip thermistor according to a second embodiment of the present invention will be described with reference to FIG. FIG. 9 is a diagram in which the exterior is removed from the chip thermistor according to the second embodiment. In the figure, the first
The same reference numerals are given to members and elements similar to those of the embodiment.

The chip thermistor 70 according to the present embodiment
However, the difference from the above-described chip thermistor 10 lies in the structure of the first layer of the terminal electrode. Hereinafter, the contents will be described.

The chip thermistor 70 has the thermistor body 20, a pair of terminal electrodes formed at both ends of the thermistor body 20, and an exterior formed at the center of the thermistor body 20. The configurations of the thermistor body 20 and the exterior are the same as those in the first embodiment, and therefore, the description is omitted.

The terminal electrode is formed of a metal film having a multilayer structure.
Specifically, the first layer 71 formed on the surface of the thermistor body 20, the second layer formed on the surface of the first layer 71, the second layer
The third layer 72 is formed on the surface of the layer. Here, the second layer and the third layer 72 are formed in the prism portions 21 at both ends of the thermistor body 20, as in the first embodiment.

As shown in FIG. 9, the first layers 71 of the terminal electrodes are arranged at intervals around the center of the cylindrical portion 22 of the thermistor body 20. The difference between the first layer 71 and the first embodiment is the shape of the edge of the first layer 71 facing the first embodiment. That is, the first layer 7
The edge portion 1 is not formed in a straight line with respect to the circumferential direction of the column portion 22, but meanders in the length direction of the column portion 22. In other words, the edge of the first layer 71 has irregularities in the length direction of the column 22 on the peripheral surface of the column 22.
Therefore, the interval between the pair of first layers 71 is the columnar portion 2
2 is non-uniform in the circumferential direction.

In order to form such a first layer 71, first, a plating layer 71a is formed on the entire surface of the thermistor body 20. Next, the longitudinal end face of the thermistor body 20 is held by a rotatable support (not shown). Then
As shown in FIG. 10, while rotating the thermistor body 20 intermittently, the central cylindrical portion 22 is irradiated with laser light to remove the plating layer 72a in a ring shape. At this time, the laser light source 65 is repeatedly moved in the longitudinal direction of the thermistor body 20. Thus, the central portion of the plating layer 71a is removed, and the first layer 71 as shown in FIG. 9 is formed. In this step, similarly to the first embodiment,
The plating layer 71a is removed while measuring the resistance characteristics by the measuring device 62. Then, when the measuring device 62 shows a desired resistance characteristic, the removal is terminated.

In the chip thermistor 70, when a part of the plating layer 71 a is removed to form a pair of first layers 71, the edges of the first layer 71 meander in the length direction of the cylindrical portion 22. Since it is formed, fine adjustment of the resistance characteristics becomes easy. Therefore, highly accurate resistance adjustment is possible. Other functions and effects are the same as those of the first embodiment.

In the present embodiment, the plating layer 71a
In the removal step, the thermistor body 20 is rotated and the irradiation position of the laser is moved in the longitudinal direction of the thermistor body 20, but another method may be adopted.
For example, in the same manner as in the first embodiment, after removing the plating layer 71a into a ring having a fixed width by mechanical processing or laser processing, the first layer 71 is formed in the longitudinal direction of the thermistor body 20 by laser processing or the like. You may make it trim. In this case, fine adjustment of the resistance characteristics is further facilitated. Further, as shown in FIG. 11, after forming the first layer 71c having the shape shown in FIG. 9 by laser beam irradiation, the edge of the first layer 71c may be further trimmed by laser processing or the like. Also in this case, fine adjustment of the resistance characteristics is further facilitated.

Further, in the present embodiment, as shown in FIG. 9, the first layer 71 is formed such that its edge meanders in the circumferential direction of the columnar portion 22, but the present invention is not limited to this. Not something. For example, as shown in FIG. 12, the first layer 71d may be formed so that the edge is inclined with respect to the longitudinal direction of the cylindrical portion 22.

(Third Embodiment) A chip thermistor according to a third embodiment of the present invention will be described with reference to FIG. FIG. 13 is a sectional view of a chip thermistor according to the third embodiment. In the drawings, the same reference numerals are given to the same members and elements as in the first embodiment.

The chip thermistor 80 according to the present embodiment
However, the difference from the above-described chip thermistor 10 lies in the structure of the thermistor body. Hereinafter, the contents will be described.

This chip thermistor body 80 has a thermistor body 81, a pair of terminal electrodes 30 formed at both ends of the thermistor body 81, and an exterior 40 formed at the center of the thermistor body 81. are doing. Since the configurations of the terminal electrode 30 and the exterior 40 are the same as those of the first embodiment, the description is omitted.

As shown in FIG. 13, the portion of the thermistor body 81 that is not covered with the terminal electrode 30, that is, the cylindrical portion 82 between the pair of first layers 31 is ground. In other words, a groove having a width equal to the gap between the pair of first layers 31 is formed in an annular shape in the circumferential direction of the cylindrical portion 82.
Thus, the cylindrical portion 82 has a smaller diameter at the portion where the first layer 31 is not formed than at other portions.

In order to obtain the chip thermistor 80 having the thermistor body 81, the chip thermistor 80 is formed on the surface of the cylindrical portion 82 in the step of grinding and removing the first layer 31 in the first embodiment (see FIG. 7). A portion of the column portion 82 may be scraped off together with the first layer 31 thus formed.

In the chip thermistor 80, the plating layer 31a formed on the surface of the thermistor body 81 is removed and the cylindrical portion 82 of the thermistor body 81 is also ground. The adjustment range of the resistance characteristic is expanded. Other functions and effects are the same as those of the first embodiment.

In the present embodiment, all portions of the cylindrical portion 82 of the thermistor body 81 where the first layer 31 is not formed are ground, but the present invention is not limited to this. For example, as shown in FIG.
An annular groove 83 extending in the circumferential direction along one edge may be formed. Further, as shown in FIG. 15, a groove 83 may be formed in the columnar portion 82 between the pair of first layers 31.

As described in detail above, in each embodiment,
After forming a metal film on the entire surface of the thermistor body, a pair of terminal electrodes made of a metal film were formed by removing the metal film formed at the center of the thermistor body. However, the present invention is not limited to this. For example,
After the cylindrical surface of the thermistor body is masked in an annular shape, a metal film may be formed on the entire surface of the thermistor body by plating or the like, and finally, the mask may be removed.

Further, in each of the embodiments, a plating process is exemplified as a means for forming a metal film on the entire surface of the thermistor body, but the present invention is not limited to this. That is, not only a wet metal film forming method such as plating, but also a dry metal film forming method such as sputtering may be used.

Further, in each of the embodiments, the thermistor body is formed by integrally forming the prism portions at both ends and the central column portion sandwiched between the prism portions, but the present invention is not limited to this. Not something. For example, the central column may have a shape whose diameter increases and decreases in the longitudinal direction. Specifically, for example, a shape in which the diameter of the central portion is larger than both ends in the longitudinal direction, or conversely, a shape in which the central portion is small may be used.
Further, the central portion of the thermistor body may have an elliptical cross section. Furthermore, the central part of the thermistor body may be a prismatic shape such as a regular square prism.

[0080]

As described in detail above, according to the present invention,
A desired resistance characteristic can be obtained by adjusting the dimensions of the cylindrical portion and the prism portion of the thermistor body. Further, the resistance characteristic can be adjusted by adjusting the distance between the pair of metal films formed from both ends of the thermistor body to the center. Therefore, since the adjustment after the thermistor body is manufactured is possible, the adjustment of the resistance characteristic can be performed easily and with high accuracy. Further, since both ends of the thermistor element are prismatic, they do not roll even when the chip thermistor is mounted on the circuit board on which it is mounted.
Therefore, the chip thermistor of the present invention is suitable for surface mounting.

[Brief description of the drawings]

FIG. 1 is an external perspective view of a chip thermistor according to a first embodiment.

FIG. 2 is a cross-sectional view of the chip thermistor according to the first embodiment.

FIG. 3 is a view showing a process of forming a unit base material.

FIG. 4 is a diagram showing a grinding process of a unit base material.

FIG. 5 is a perspective view of a thermistor body after barrel polishing.

FIG. 6 is a cross-sectional view of a thermistor body after a plating layer is formed.

FIG. 7 is a diagram showing a step of removing a plating layer;

FIG. 8 is a view showing a step of forming an exterior.

FIG. 9 is a view of the chip thermistor according to the second embodiment, in which an exterior is removed.

FIG. 10 is a view showing a step of removing a plating layer;

FIG. 11 is a view of a chip thermistor according to another example of the second embodiment with the exterior removed.

FIG. 12 is a diagram in which an exterior is removed from a chip thermistor according to another example of the second embodiment.

FIG. 13 is a sectional view of a chip thermistor according to a third embodiment;

FIG. 14 is a sectional view of a chip thermistor according to another example of the third embodiment;

FIG. 15 is a sectional view of a chip thermistor according to another example of the third embodiment;

FIG. 16 is a perspective view of a conventional multilayer chip thermistor with a part cut away.

[Explanation of symbols]

10, 70, 80: chip thermistor, 20, 81: thermistor body, 21: prism, 22, 82: column, 8
3, groove, 30, 71 terminal electrode, 31, 72 first layer,
31a, 72a: plating layer, 32: second layer, 33, 73
... Third layer, 40 exterior, 50 material bar, 51 material sheet, 52 unit substrate, 60, 61 cutting blade, 62 measuring instrument

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shinichi Harada 6-16-20 Ueno, Taito-ku, Tokyo Taiyo Denki Co., Ltd. (72) Inventor Junichi Fukuyama 6-16-20 Ueno, Taito-ku, Tokyo Taiyo F-term (in reference) 5E034 BB01 BC02 BC04 DA02 DB05 DC01 DC03 DC09 DE05 DE14

Claims (14)

[Claims] 1. A thermistor element having both ends forming a prism, and a central part sandwiched between the both ends formed in a column or prism having a smaller diameter than both ends, and a prism at both ends of the thermistor element. A chip thermistor, comprising: a pair of terminal electrodes formed of metal films that are covered and formed from the prism portion to the central portion and are nonconductive to each other. 2. An outer case formed at a central portion of the thermistor body so that an external shape is a prism having an end defined by prism portions at both ends of the thermistor body. 2. The chip thermistor according to 1. 3. The metal film has an inner layer formed from a prism portion to a center portion, and an outer layer formed on a surface of the inner layer where the exterior is not formed. The chip thermistor according to claim 2, wherein 4. The chip thermistor according to claim 1, wherein the thermistor body has at least a part of a central portion of the metal film that is not covered with the metal film removed. 5. The chip thermistor according to claim 1, wherein the pair of metal films are formed such that the distance between them is non-uniform in the circumferential direction of the thermistor body. 6. A step of grinding a central portion of a prism-shaped thermistor body into a cylinder or a prism having a smaller diameter than both end portions, covering the ground thermistor body with the prism portions at both ends, Forming a pair of terminal electrodes formed of metal films that are formed from a portion to a central portion and are not conductive to each other. 7. The terminal electrode forming step includes: forming a metal film so as to cover the whole surface of the ground thermistor body; 7. The method of manufacturing a chip thermistor according to claim 6, further comprising the step of: removing at least a part of a metal film formed in a central portion of the thermistor body. 8. The chip according to claim 7, wherein, in the metal film removing step, the chip thermistor removes the metal film so as to have a desired resistance value while measuring a resistance value between the pair of metal films. A method for manufacturing a thermistor. 9. The method of manufacturing a chip thermistor according to claim 7, wherein in the metal film removing step, the thermistor body is ground together with the removal of the metal film. 10. A process prior to the metal film forming step,
The method for manufacturing a chip thermistor according to claim 6, further comprising a step of activating a surface of the thermistor body. 11. The terminal electrode forming step includes a step of forming a metal film over the entire thermistor body by using a circular mask at a central portion of the thermistor body, and a step of removing the mask. The method for manufacturing a chip thermistor according to claim 6. 12. The method of manufacturing a chip thermistor according to claim 6, further comprising a step of adjusting a resistance value by trimming the metal film. 13. A step of forming an exterior at a central portion of the thermistor body after the terminal electrode forming step, so that an external shape becomes a prism having an end defined by prisms at both ends of the thermistor body. 7. The device according to claim 6, wherein
13. The method for manufacturing a chip thermistor according to any one of claims 12 to 12. 14. The method according to claim 13, further comprising a step of plating the metal film exposed at both ends of the thermistor body to form a multilayer structure of the metal film after the exterior forming step. Of manufacturing a chip thermistor.