JP2000195707A - Chip type thermistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hardly generate cracks of terminal electrodes when products are rubbed with each other in a parts feeder or the like, by arranging an insulating film having a thickness greater than the terminal electrodes on one surface of the peripheries of the first and the second terminal electrodes. SOLUTION: A chip type thermistor 1 is constituted by using a thermistor element 2 formed of semiconductor ceramics. A first and a second terminal electrodes 3, 4 are arranged on the upper surface 2a of the thermistor element 2 with a specified distance between them. An insulating film 5 is formed so as to surround the peripheries of the first and the second terminal electrodes 3, 4. The insulating film 5 is formed so as to have a thickness greater than the heights of the first and the second terminal electrodes 3, 4. The insulating film 5 is formed of heat-resistant resin like polyimide. As a result, cracks are hardly generated on the terminal electrodes when products are rubbed with each other in a parts feeder or the like, and generation of change of resistance value, terminal defects, etc., are prevented.

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 used for, for example, a temperature compensation circuit or a temperature detecting element, and more particularly, to a thermistor element having first and second terminal electrodes formed on one surface thereof. To a chip-type thermistor.

[0002]

2. Description of the Related Art Conventionally, chip type thermistors using semiconductor ceramics having positive or negative resistance temperature characteristics have been widely used in temperature detecting elements, temperature compensating circuits and the like. In addition, various types of chip thermistors that can be easily surface-mounted on a printed circuit board or the like have been proposed.

FIG. 13 is a perspective view showing a conventional chip type thermistor having a one-sided electrode as a terminal electrode capable of reducing a mounting area. Chip type thermistor 51
Is composed of a thermistor body 52, and a pair of surface electrodes 53 and 54 are formed on one surface of the thermistor body 52. An insulating film 5 is provided between the surface electrodes 53 and 54.
5 are provided. Further, terminal electrodes 56 and 57 are provided on the surface electrodes 53 and 54, respectively. Since the chip type thermistor 51 having such a structure has a small mounting area, there is an advantage that high-density mounting can be achieved.

[0004]

However, FIG.
In the conventional chip-type thermistor shown in (1), since the terminal electrodes are formed at the corners of the chip, there is a problem that the terminal electrodes are easily chipped. In other words, when mounting on a printed circuit board or the like, in the actual work line, a number of chip-type thermistors are accommodated in the parts feeder and supplied from the parts feeder and mounted on the printed circuit board etc. Are rubbed against each other, and in a chip type thermistor as shown in FIG. 13, the terminal electrode at the corner may be chipped. If a part of the terminal electrode is chipped, the contact area with the ceramic chip changes, which causes a problem that the resistance value of the chip type thermistor changes. Also, if the terminal electrode is missing,
At the time of soldering, there is a problem that the electrode is easily eroded.

An object of the present invention is to provide a chip-type thermistor which is less likely to cause chipping of a terminal electrode even when products rub against each other in a parts feeder or the like, thereby hardly causing a change in resistance value.

[0006]

According to a first aspect of the present invention, there is provided a chip-type thermistor comprising: a thermistor element; and first and second terminals formed on one surface of the thermistor element so as to face each other. An electrode, and an insulating film provided on one surface around the first and second terminal electrodes and having a thickness higher than that of the first and second terminal electrodes. .

According to a second aspect of the present invention, the first and second terminal electrodes are in direct ohmic contact with the thermistor body. In the invention according to claim 3,
First and second surfaces between the first and second terminal electrodes and the thermistor element, which are electrically connected to the first and second terminal electrodes, respectively, and are in ohmic contact with the thermistor element. Electrodes are provided.

According to a fourth aspect of the present invention, in the third aspect of the invention, the distance between the first and second surface electrodes is
It is formed to be shorter than the distance between the first and second terminal electrodes.

The chip type thermistor according to the present invention may use either a thermistor element having a positive resistance temperature characteristic or a thermistor element having a negative resistance temperature characteristic. Any of an NTC thermistor and a PTC thermistor may be used.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be clarified below by giving non-limiting embodiments of the present invention with reference to the drawings.

FIG. 1 is a side sectional view showing a chip type thermistor according to a first embodiment of the present invention.
FIGS. 4 and 5 are a plan view and a side view, respectively, showing the chip thermistor according to the first embodiment.

The chip type thermistor 1 is constituted by using a thermistor body 2 made of semiconductor ceramics. On the upper surface 2a of the thermistor body 2, first and second terminal electrodes 3 and 4 are provided at a predetermined distance. An insulating film 5 is formed on the upper surface 2a around the first and second terminal electrodes so as to surround the first and second terminal electrodes. The insulating film 5 is formed with a thickness such that the height of the insulating film 5 is higher than the heights of the first and second terminal electrodes 3 and 4. The difference between the heights of the first and second terminal electrodes 3 and 4 and the height of the insulating film 5 is not particularly limited, but the current thickness of the land solder paste is generally 100 to 20.
Since the height is 0 μm, the difference in height is preferably 100 μm or less, and more preferably in the range of 2 to 30 μm.

The first and second terminal electrodes are preferably formed of a material that makes ohmic contact with the thermistor body 2. The method of forming the terminal electrode is not particularly limited, but the terminal electrode can be formed by, for example, a screen printing method. The insulating film 5 preferably has heat resistance so as to withstand the soldering step, and can be formed using, for example, a heat-resistant resin such as polyimide. The insulating film 5 can be formed by, for example, a photolithography method.

The terminal electrodes 3, 4 and the insulating film 5 may be provided at an interval as shown in FIG. 2, or may be provided so as to be in contact with each other as shown in FIG.
In addition, as shown in FIG.
The interval is preferably not more than 00 μm.

The resistance value of the chip type thermistor 1 is determined by the specific resistance of the thermistor body 2, the shape of the thermistor body 2, and the area between the first and second terminal electrodes 3 and 4 facing each other. Is done. In the chip thermistor 1 of the present embodiment, the insulating film 5 is provided so as to be higher than the first and second terminal electrodes 3 and 4, so that even if products rub against each other in the parts feeder, The terminal electrodes 3 and 4 can be protected by the insulating film 5, and it is possible to prevent other products from hitting the terminal electrodes 3 and 4. Therefore, the terminal electrodes 3 and 4 are less likely to be chipped, and it is possible to prevent the resistance value from changing in a later step.

Next, a specific experimental example of the chip type thermistor 1 will be described. The chip thermistor 1 was manufactured in the following manner. First, a Mn compound, N
The i compound and the Co compound were kneaded with a binder to prepare a slurry, which was formed into a sheet by a doctor blade method and cut into a 65 × 65 mm planar shape to obtain a rectangular green sheet. After laminating a plurality of the above green sheets and pressing them, 1300 ° C., 1
Baking under the condition of time, 50 × 50 × shown in FIG.
A sintered ceramic sheet 2 for thermistor body having a dimension of 0.5 mm was obtained.

Next, an Ag / Pd paste is applied by screen printing and baked at 700 ° C. for 60 minutes.
Terminal electrodes 3 and 4 having a thickness of 20 μm were formed (FIG. 6).
(B)). Further, a photosensitive polyimide resin was applied on the terminal electrodes 3 and 4 and the ceramic sintered sheet 12 for the thermistor element by a spin coater so as to have a thickness of 30 μm to form a polyimide film 5 (FIG. 6 (c)). )).

Next, a photomask 6 having a pattern capable of exposing portions where the terminal electrodes 3 and 4 are not formed is disposed on the polyimide film 5 and exposed (FIG. 6).
(D)).

Next, as shown in FIG. 6 (e), the photosensitive polyimide film is developed with a solvent and cured at 350 ° C. for 60 minutes. An insulating film 5 made of polyimide was formed. The thickness of the insulating film 5 was 25 μm. FIG. 7 is a plan view in the state shown in FIG.

Next, as shown in FIG. 6 (f), the ceramic sintered sheet 2 for the thermistor body is 1.6 × 0.8 m
The resultant was cut by dicing into m-shaped chips to obtain a plurality of chip-type thermistors 1. FIG. 8 is a plan view in the state shown in FIG.

After 1000 obtained chip type thermistors were put into a parts feeder and rotated in the parts feeder, an appearance inspection was performed. As a result, no abnormality such as chipping of terminal electrodes was found in each chip type thermistor. .
Also, with respect to the change in the resistance value, no chip-type thermistor having changed by 0.5% or more was found. 270 ° C
The chip was immersed in the molten solder for 30 seconds and subjected to an appearance inspection. As a result, there was no chip having a solder eroded area of 25% or less.

(Comparative Example 1) With respect to the conventional chip-type thermistor shown in FIG. 13, 1000 pieces were put into a parts feeder and rotated as in Example 1, and an appearance inspection was carried out. Six chip-type thermistors were found. In addition, when the resistance value change was measured for six chip-type thermistors lacking terminal electrodes,
The resistance value was changed by 0.5 to 2.0%.

When 1000 chip-type thermistors were immersed in molten solder at 270 ° C. for 30 seconds and inspected for appearance, it was found that 11 chips had a solder erosion area of 25% or less. .

(Embodiment 2) FIGS. 9A to 9C show a chip type thermistor according to a second embodiment of the present invention, wherein FIG. 9A is a plan view and FIG. , (C) is a side sectional view.

The chip type thermistor 11 is constituted by using a thermistor body 12 made of semiconductor ceramics. On the upper surface 12a of the thermistor body 12, first,
Second surface electrodes 16 and 17 are formed. The surface electrodes 16 and 17 are formed by, for example, a laminated structure of a Ni / Cr alloy film and an Au film, and are in ohmic contact with the thermistor body 12. In addition, as described later, the surface electrode 1
6 and 17 can be formed by patterning, for example, by photolithography.

First and second terminal electrodes 13 and 14 are formed on the first and second surface electrodes 16 and 17, respectively. The first and second terminal electrodes 13 and 14 are
The second surface electrodes 16 and 17 are electrically connected.
The terminal electrodes 13 and 14 can be formed of an Au film or the like by, for example, a plating method, as described later.

An insulating film 15 is formed around the first and second terminal electrodes 13 and 14 so as to surround the first and second terminal electrodes 13 and 14. In this embodiment, the insulating film 15 is formed so as to be almost in contact with the terminal electrodes 13 and 14. Such an insulating film 15 can be formed, for example, by a photolithography method using a heat-resistant resin such as polyimide. The insulating film 15 is a terminal electrode 1
The insulating film 15 is formed to have a thickness such that the height of the insulating film 15 is higher than the heights of the insulating films 15 and 16.

The resistance value of the chip type thermistor 11 of this embodiment is determined by the specific resistance of the thermistor body 12, the shape of the thermistor body 12, and the distance between the opposing electrodes of the first and second surface electrodes 16 and 17. Is determined by the area of Therefore, the resistance value can be reduced by reducing the distance between the surface electrodes 16 and 17. Therefore, the terminal electrodes 13,
The resistance value can be reduced without changing the distance between.

In the chip type thermistor 11 of this embodiment, the insulating film 15 is provided so as to be higher than the heights of the terminal electrodes 13 and 14, as described above. As described above, since the insulating film 15 is provided so as to be higher than the terminal electrodes 13 and 14, even if products rub against each other in the parts feeder, it is possible to prevent another product from hitting the terminal electrodes 13 and 14. be able to. Therefore, the terminal electrodes 13 and 14 are hardly chipped, and a change in resistance value, electrode erosion, and the like can be reduced.

Next, a specific experimental example of the chip type thermistor 11 of the second embodiment will be described. The chip thermistor 11 was manufactured in the following manner.

First, a Mn compound, a Ni compound, and a Co compound are kneaded with a binder to prepare a slurry, which is formed into a sheet by a doctor blade method, and is formed into a sheet having a size of 65 ×.
The sheet was cut so as to have a planar shape of 65 mm to obtain a rectangular green sheet. A plurality of the above-mentioned green sheets are laminated, pressed and fired at 1300 ° C. for 1 hour, and the ceramic sintered body for a thermistor body having a size of 50 × 50 × 0.5 mm shown in FIG. Sheet 12 was obtained.

Next, as shown in FIG. 10B, on the upper surface of the ceramic sintered sheet 12 for the thermistor body, a Ni / Cr alloy film is formed in a lower layer portion, an Au film is formed in an upper layer portion, and each is formed by evaporation. ... .Mu.m were sequentially formed and laminated to form a laminated metal film 20. FIG. The laminated metal film 20 finally constitutes a surface electrode. Particularly, as a surface electrode material of a lower layer portion, it is in electrical ohmic contact with the thermistor body, has a strong mechanical peel strength, and has a high post-processing strength. It is desirable to use a material that is easy to work with. Further, it is desirable to use a metal material having a low specific resistance as the electrode material of the upper layer portion.

Next, as shown in FIG. 10C, a photoresist was applied on the laminated metal film 20 to a thickness of 1 μm by a spin coater to form a photoresist layer 21.

Next, as shown in FIG. 10D, a mask 22 having a predetermined shape is brought into contact with the photoresist layer 21.
Exposure. Next, as shown in FIG. 10E, development was performed using a solvent, and the photoresist layer 21 was patterned.

Next, the portion not covered with the photoresist layer 21 is replaced with the upper Au film, and then the lower Ni / Cr film.
Etching was performed using an acid in the order of the film, and patterning was performed so as to be a surface electrode. Next, the photoresist layer 21 remaining on the patterned electrodes was stripped with a solvent to obtain patterned surface electrodes 16 and 17 as shown in FIG.

The surface electrodes 16 formed as described above,
Reference numeral 17 has a shape in which surface electrodes of a plurality of thermistor elements are assembled. Patterning was performed so that the facing distance between the pair of surface electrodes 16 and 17 in each thermistor element portion was 100 μm. The resistance accuracy of the thermistor
The distance between the electrodes greatly depends on the distance between the surface electrodes, and the distance between the electrodes is preferably about 10 to 100 μm in consideration of the accuracy of photolithography processing and the required resistance value.

Next, as shown in FIG. 11A, a photosensitive polyimide resin is spun on the entire surface of the surface electrodes 16, 17 and the ceramic sintered sheet 12 for the thermistor body so as to have a thickness of 10 μm. It was applied with a coater to form a polyimide film 15.

Next, as shown in FIG. 11B, a photomask 23 was disposed on the polyimide film 15. As the photomask 23, one having a pattern capable of exposing a portion covering the surface electrodes 16 and 17 was used. The polyimide film 15 was exposed using such a mask 23.

Next, the photosensitive polyimide film was developed with a solvent and cured at 350 ° C. for 60 minutes to form an insulating film 15 made of a 7 μm-thick polyimide film (FIG. 11C).

Next, a 5 μm thick Au film is formed on the surface electrodes 16 and 17 on which the insulating film 15 is not formed by immersing in an Au plating solution.
Terminal electrodes 13 and 14 were formed on the substrate (see FIG. 11).
(D)).

Next, as shown in FIG. 11 (e), the ceramic sintered sheet 12 for thermistor body was placed in a 1.6 × 0.
The chip was cut into 8 mm chips by dicing to obtain a plurality of chip thermistors 11.

After 1,000 of the obtained chip-type thermistors were put in a parts feeder and rotated, an appearance inspection was performed. As a result, no abnormality such as chipping of the terminal electrodes was found at all. Regarding the change in resistance, no chip thermistor having a change in resistance of 0.5% or more was observed. Furthermore, it is immersed in molten solder at 270 ° C. for 30 seconds,
When a visual inspection was performed, there was no chip having a solder eroded area of 25% or less.

(Embodiment 3) FIGS. 12A to 12C are views showing a chip type thermistor according to a third embodiment of the present invention, wherein FIG. 12A is a plan view and FIG. FIG. 3C is a side sectional view. The chip thermistor 31 is configured using a thermistor body 32 made of semiconductor ceramics. On the upper surface 32a of the thermistor body 32, first and second terminal electrodes 33 and 34 are formed. The terminal electrodes 33 and 34 are formed of a material that makes ohmic contact with the ceramic body 32, and are formed, for example, by applying and baking an Ag / Pd paste by a screen printing method as in the first embodiment.

An insulating film 35 is formed around the terminal electrodes 33 and 34 so as to surround the terminal electrodes 33 and 34.
The insulating film 35 is formed, for example, by a photolithography method using a heat-resistant resin such as polyimide. The height of the insulating film 35 is formed to be higher than the height of the terminal electrodes 33 and 34. Therefore, even if the products are rubbed in the parts feeder as in the first and second embodiments, other products can be prevented from hitting the terminal electrodes 33 and 34, and the terminal electrodes 33 and 34 can be prevented. Can be prevented from occurring, and a change in resistance value can be reduced.

The ceramic body 32 of the embodiment shown in FIG.
Has a shape with rounded corners. Such a chip-type thermistor is formed, for example, by obtaining a chip-type thermistor having a sharp corner and then polishing it with a barrel or the like to forcibly cut the corner of the thermistor body. Such barrel polishing is generally performed to adjust the resistance value of the thermistor. In the chip-type thermistor of this embodiment, the insulating film 35 is formed so as to be higher than the terminal electrodes 33 and 34, so that the corners of the ceramic body are forcibly cut by such barrel polishing or the like. Sometimes
Chipping of the terminal electrodes 33 and 34 can be prevented.

In each of the above embodiments, the insulating film is formed so as to surround the first and second terminal electrodes. However, the insulating film does not necessarily surround the first and second terminal electrodes. The first and second terminal electrodes may be partially formed around the first and second terminal electrodes.

[0047]

In the chip thermistor according to the first aspect of the present invention, the insulating film is provided on one surface around the first and second terminal electrodes, and is higher than the first and second terminal electrodes. It is formed with such a thickness. Therefore, even if the products rub against each other in the parts feeder or the like, chipping of the terminal electrode hardly occurs, and therefore, change of the resistance value, electrode erosion and the like can be hardly caused.

According to the second aspect of the invention, the first and second terminal electrodes are provided directly on the thermistor body, and are in ohmic contact with the thermistor body. Therefore, even in such a chip type thermistor, chipping of the terminal electrode can be prevented, and change in resistance value, electrode erosion, and the like can be prevented.

According to the third aspect of the present invention, the first and second surface electrodes are provided on the thermistor body, and the first and second surface electrodes are provided.
First and second terminal electrodes are provided on the second surface electrode. Therefore, even in such a chip thermistor of this type, the occurrence of chipping of the terminal electrode can be similarly prevented, so that a change in resistance value, electrode erosion, and the like can be prevented.

According to the fourth aspect of the present invention, the distance between the first and second surface electrodes is formed so as to be shorter than the distance between the first and second terminal electrodes. Therefore, since the resistance value is determined by the distance between the first and second surface electrodes,
The resistance value can be adjusted without changing the distance between the first and second terminal electrodes. Further, it is possible to prevent chipping of the terminal electrode in such a chip thermistor of this type, thereby preventing a change in resistance value and the occurrence of electrode erosion.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a chip type thermistor according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a state in which a gap is formed between an insulating film and a terminal electrode.

FIG. 3 is a cross-sectional view showing a state where an insulating film and a terminal electrode are formed so as to be in contact with each other.

FIG. 4 is a plan view of the chip thermistor according to the first embodiment of the present invention.

FIG. 5 is a side view of the chip thermistor according to the first embodiment of the present invention.

FIG. 6 is a sectional view showing a step of manufacturing the chip thermistor according to the first embodiment of the present invention.

FIG. 7 is a plan view showing the state of FIG. 6 (e).

FIG. 8 is a plan view showing the state of FIG. 6 (f).

9A is a plan view, FIG. 9B is a side view, and FIG. 9C is a cross-sectional side view of a chip-type thermistor according to a second embodiment of the present invention.

FIG. 10 is a sectional view showing a manufacturing process of the chip-type thermistor according to the second embodiment of the present invention.

FIG. 11 is a sectional view showing a manufacturing process of the chip thermistor according to the second embodiment of the present invention.

12A is a plan view, FIG. 12B is a side view, and FIG. 12C is a sectional side view showing a chip type thermistor according to a third embodiment of the present invention.

FIG. 13 is a perspective view showing a conventional chip thermistor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Chip type thermistor 2 ... Thermistor body 3, 4 ... First and second terminal electrodes 5 ... Insulating film 11 ... Chip type thermistor 12 ... Thermistor body 13, 14 ... First and second terminal electrodes 15 ... Insulating films 16, 17 First and second surface electrodes 31 Chip thermistors 32 Thermistor bodies 33, 34 First and second terminal electrodes 35 Insulating films

Claims (4)

[Claims] 1. A thermistor body, first and second terminal electrodes formed on one surface of the thermistor body so as to face each other, and the one surface around the first and second terminal electrodes. A chip thermistor, comprising: an insulating film provided thereon and having a thickness higher than the first and second terminal electrodes. 2. The chip thermistor according to claim 1, wherein said first and second terminal electrodes are in direct ohmic contact with said thermistor body. 3. The first and second terminal electrodes are electrically connected between the first and second terminal electrodes and the thermistor body, respectively, and are in ohmic contact with the thermistor body. 2. The chip thermistor according to claim 1, wherein said first and second surface electrodes are provided. 4. A distance between the first and second surface electrodes,
4. The chip thermistor according to claim 3, wherein said chip type thermistor is formed to be shorter than a distance between said first and second terminal electrodes.