JP2000082606A - Chip-type thermistor and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly precise, highly strong, and highly reliable chip-type thermistor having inner electrodes and surface electrodes and wide thermistor characteristics (the combination of a resistance value with a B constant). SOLUTION: Insulating protecting layers 4 are formed on the four side faces of a thermistor element 1 in which inner electrodes 2A and 2B and surface electrodes 3A-3D are formed, and external electrodes 5A and 5B are formed on the both end faces in this chip-type thermistor 10A. Thermistor green sheets on which conductive layers for forming inner electrodes are formed are laminated and sintered, and a conductive layer for forming surface electrodes and an insulating coated layer are formed on the upper and lower main plate faces of the sintered body, and this is cut like a prism. Then, insulating coating layers are formed on the two non-coated side faces of the prismatic thermistor element, and this is cut in a direction orthogonally crossing a longitudinal direction so that a chip can be obtained, and external electrodes are formed on the both edge faces of this chip. Thus, this chip-type thermistor can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip thermistor surface-mounted on a printed circuit board or the like and a method for manufacturing the same, and more particularly to a negative thermistor whose resistance value decreases with an increase in temperature. The present invention relates to a chip thermistor having a wide range, high accuracy and high reliability, and a method of manufacturing such a chip thermistor with good workability.

[0002]

2. Description of the Related Art A typical product of a chip thermistor surface-mounted on a printed circuit board or the like is shown in FIG.
External electrodes 42 are provided on both end surfaces of the chip-shaped thermistor element 41 as terminal electrodes made of a conductive metal layer 42A for improving solder heat resistance and solder adhesion, and a Ni plating layer 42B and a solder plating layer covering the surface thereof. 42C, and the four side surfaces other than the external electrode forming end surfaces are
3 is a chip-type thermistor 40 having a structure covered with the same. Further, in order to expand the electrical characteristics of the chip-type thermistor, for example, the combination of the resistance value and the B constant, surface electrodes for adjusting the resistance value are formed on two opposing side surfaces of the chip-like thermistor element body 41, and are formed thereon. There is a type in which a glass layer is formed, and a type in which an internal electrode is formed inside the chip-shaped thermistor body 41.

Conventionally, such a chip-type thermistor has been manufactured as follows.

After the thermistor block is molded and fired, it is cut into a chip shape, four side surfaces of the chip-like thermistor body are covered with glass layers, and external electrodes are formed on both end surfaces. That is, by applying and baking a conductive paste, the conductive metal layer is baked, and further, a Ni plating layer and a solder plating layer are formed.

When forming a surface electrode, a conductive layer for forming a surface electrode is formed on the main plate surface of the thermistor sintered plate before cutting into a chip shape.

If necessary, a plurality of thermistor green sheets are laminated using a thermistor green sheet on which a conductive layer for forming internal electrodes and a conductive layer for forming surface electrodes are formed, and a glass layer is formed. It is cut into a chip shape and external electrodes are formed in the same manner as described above.

[0007]

According to the above method, a chip thermistor having surface electrodes can be manufactured, but a chip thermistor having internal electrodes cannot be manufactured. With only the surface electrode, the effect of reducing the resistance value is limited, and the range of the thermistor characteristics (combination of the resistance value and the B constant) obtained is relatively narrow. There is a problem in realizing a thermistor.

In the above method, a chip thermistor having an internal electrode and a surface electrode can be manufactured. However, in order to cut the chip into a chip at a green stage before firing,
Due to the effects of shrinkage variation during firing, sufficient dimensional accuracy cannot be obtained, and as a result, there has been a problem that sufficient resistance value accuracy cannot be achieved as a product characteristic. In addition, the internal electrode has an excellent effect of reducing the resistance value. However, since the electrode is formed at the green stage, sufficient resistance value accuracy cannot be obtained as described above as a product characteristic. was there.

The present invention solves the above-mentioned conventional problems, and is a chip type thermistor having an internal electrode and a surface electrode and having a wide range of thermistor characteristics (combination of resistance value and B constant). And a highly reliable chip type thermistor and a method for manufacturing the same.

[0010]

The chip type thermistor of the present invention has a thermistor element having an internal electrode formed therein and a surface electrode formed on a side face thereof, and an insulating element formed on four side faces of the thermistor element body. And an external electrode formed on both end surfaces of the thermistor body.

The method of manufacturing a chip-type thermistor according to the present invention is characterized in that a plurality of thermistor green sheets each having a conductive layer for forming an internal electrode formed thereon are laminated on at least a part of the thermistor green sheets and then fired to form a thin plate thermistor. Manufacturing a body, forming a conductive layer for forming a surface electrode on the upper and lower main plate surfaces of the thermistor sintered body, and insulating the upper and lower main plate surfaces of the thermistor sintered body on which the conductive layer is formed. Forming a coating layer of the above, and cutting the sintered body of thermistor on which the insulating coating layer is formed into a rectangular shape to obtain a prism-shaped thermistor body; and insulating the prism-shaped thermistor body. Forming an insulating coating layer on two side surfaces on which no insulating coating layer is formed, and cutting a prism-shaped thermistor body having an insulating coating layer on four side surfaces in a direction orthogonal to the longitudinal direction Then click Obtaining a Jo thermistor element, characterized in that a step of forming external electrodes on both ends surfaces not formed with the insulating covering layer of the chip-like thermistor body.

The chip type thermistor of the present invention has an internal electrode and a surface electrode, so that the resistance can be reduced and a wide range of thermistor characteristics can be realized.

In addition, since it has a surface electrode, it has high strength,
Excellent in temperature cycle performance after mounting. In addition, since it has an insulating protective layer, reliability such as weather resistance and strength is high.

According to the chip-type thermistor of the present invention, in which the laminated body of thermistor green sheets is baked in the form of a wafer without being cut and cut after forming the surface electrode, the wafer is cut and processed, so that a preliminary test is performed. And fine adjustment of the resistance value is possible.

The surface electrode not only allows the resistance value to be adjusted, but also improves the element strength.

Since the cutting is performed after firing, the resistance value can be finely adjusted according to the cutting dimension, and the accuracy of the thermistor characteristics is also high.

The operation and effect described above are achieved.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A chip type thermistor and a method for manufacturing the same according to the present invention will be described below in detail with reference to the drawings.

FIGS. 1 and 2 are cross-sectional views showing an embodiment of a chip thermistor according to the present invention. FIG. 1 (a) is a longitudinal sectional view of the chip thermistor, and FIG.
A cross-sectional view taken along the line BB of the drawing, FIG.
FIG. 3D is a cross-sectional view along the line DD in FIG. 3A, and FIG. 3E is a cross-sectional view along the line EE in FIG. In FIGS. 1 and 2, members having the same function are denoted by the same reference numerals.

The chip type thermistor 10A shown in FIG.
A rectangular parallelepiped chip-shaped thermistor element 1 made of a ceramic sintered body, internal electrodes 2A and 2B provided inside the thermistor element 1, and surface electrodes formed on a pair of opposed side surfaces of the thermistor element 1 3A, 3B, 3C, 3D
And glass layers 4 formed on four side surfaces of the thermistor body 1
And external electrodes 5 formed on both end surfaces of the thermistor body 1.
A, 5B. The internal electrode 2A is connected to the external electrode 5A,
The internal electrodes 2B are provided so as to be electrically connected to the external electrodes 5A. The surface electrodes 3A and 3C are provided so as to be electrically connected to the external electrode 5A, and the surface electrodes 3B and 3D are provided so as to be electrically connected to the external electrode 5B.

The chip type thermistor 1B shown in FIG. 2 has, as internal electrodes, internal electrodes 2a, which are electrically connected to an external electrode 5A.
2d and the internal electrodes 2b and 2e which are electrically connected to the external electrode 5B.
And an internal electrode 2C that is not electrically connected to the external electrodes 5A and 5B at an intermediate position between them, and is different from the chip-type thermistor 1A shown in FIG.

Next, a method of manufacturing such a chip type thermistor of the present invention will be described with reference to FIG.

FIGS. 3A to 3G are perspective views illustrating an embodiment of a method for manufacturing a chip thermistor according to the present invention. Ceramic green sheets 11, 12, and 13 of thermistor material are prepared by a casting method, and a conductive layer 14 serving as an internal electrode is printed at a predetermined position. The conductive layer 14 can be formed by printing a conductive paste containing a conductive metal powder such as Ag or Ag / Pd. In the illustrated example, the ceramic green sheet 1
Of the sheets 1 to 13, the conductive layer 14 was formed on one surface of the sheet 11 and the sheet 12. And this sheet 11-1
3 are laminated (FIG. 1A), pressurized, degreased and fired to obtain a thin plate-shaped sintered body 15. (FIG. 1 (b)).

Next, a conductive layer 16 to be a surface electrode is formed on the front and back main plate surfaces of the sintered body 15 (FIG. 1 (c)).
The conductive layer 16 can be formed in the same manner as the conductive layer 14 for the internal electrode. When forming the conductive layer 16, the thickness can be adjusted by polishing both main plate surfaces of the sintered body 15 as necessary.

After forming the surface electrode conductive layer 16, a glass paste is printed, dried and fired on the front and back main plate surfaces of the sintered body 15 to form a glass layer 17 (FIG. 1).
(D)) Then, the sintered body 15 is divided into the conductive layers 14 and 16.
Is cut in a direction directly supporting the extending direction of the prism (dot-dash line L _{1 in} FIG. 1D) to obtain a prism-shaped thermistor element 18 (FIG. 1E), and then this prism-shaped thermistor element The glass layer 17 is provided on the two sides 18A and 18B of the body 18 which are not covered with the glass layer.
To form The prism-shaped thermistor element 18 having the glass layers 17 formed on the four side surfaces in this manner is cut in a direction directly supporting the longitudinal direction (a dashed line L _{2 in} FIG. 1 (f)) to form a chip-shaped thermistor element. A body 19 is obtained (FIG. 1 (g)).

By forming external electrodes on both end surfaces 19A and 19B of the chip-like thermistor element 19 according to a conventional method, a chip-type thermistor 10A as shown in FIG.
Can be obtained.

It is preferable that the glass layer 17 as a protective coating layer is formed to a thickness of about 10 to 30 mm. This coating layer is not limited to a glass layer, and may be another inorganic insulating material layer.

According to the present invention, 0.6-2.
Even a small chip thermistor with a thickness of 0 mm x 0.3 to 1.25 mm x 0.3 to 1.0 mm can be manufactured with high productivity under good processing accuracy and workability. it can.

[0029]

The present invention will be described more specifically with reference to the following examples.

Example 1 A chip thermistor 10A shown in FIG. 1 was manufactured according to the method shown in FIG.

First, as starting materials, commercially available manganese carbonate, cobalt carbonate, and copper oxide are weighed so as to have a predetermined metal element ratio, wet-mixed in a ball mill for 10 hours, dried, crushed, and dried at 900 ° C. for 10 hours. It was calcined for hours. The particle size of the calcined powder was about 1 μm. Next, an organic solvent and a binder were added to the pulverized powder, and a green sheet having a thickness of 20 μm was prepared by a slip casting method.

Then, the prepared green sheets were laminated and the conductive layer for internal electrodes was printed so as to obtain the cross-sectional structure shown in FIG. The internal electrode material is Ag / Pd.
= 30: 70 conductive paste was used.

This laminate was pressed isostatically to a thickness of 100 mm.
A green sheet having a size of 100 mm and a thickness of 0.5 mm was obtained. After degreasing this laminate at 350 to 500 ° C, 11
It was fired at 00 ° C. to obtain a sintered body.

Both surfaces of this sintered body were polished, and a conductive layer for a surface electrode was formed by screen printing using the same material as the conductive material for an internal electrode.

Next, a glass paste (glass material: SiO ₂ + PbO) was applied on both sides of the sintered body by screen printing.
+ B ₂ O ₃ ) and baked at 850 ° C. to form a glass layer.

Thereafter, the resultant was cut into strips, glass layers were formed on the two side surfaces of the obtained prismatic thermistor body in the same manner as described above, and further cut into chips to obtain a chip thermistor body. The glass layer was formed to a thickness of 20 μm.

About the obtained chip type thermistor, 25
B calculated from resistance R25 at R ° C and R25 and R50
The constants and their variations were examined, and the results are shown in Table 1 together with the values of the conventional product. From Table 1, it can be seen that the product of the present invention has no variation as compared with the conventional product and exhibits remarkably good characteristics.

[0038]

[Table 1]

[0039]

As described above in detail, the chip thermistor of the present invention and the method for manufacturing the same are provided with a chip thermistor having an internal electrode and a surface electrode and having a wide range of thermistor characteristics (combination of resistance value and B constant). Thus, a highly accurate, high-strength, and highly reliable chip thermistor is provided.

[Brief description of the drawings]

FIG. 1A is a sectional view showing an embodiment of a chip thermistor of the present invention, and FIG. 1B is a sectional view of FIG.
1 (c) is a sectional view taken along line BB of FIG.
1D is a cross-sectional view taken along the line C, and FIG.
1 (e) is a cross-sectional view taken along line EE of FIG. 1 (a).

FIG. 2A is a sectional view showing another embodiment of the chip type thermistor of the present invention, and FIG.
FIG. 2A is a sectional view taken along the line BB, and FIG.
2A is a cross-sectional view taken along the line CC, and FIG.
FIG. 2A is a cross-sectional view taken along the line DD, and FIG.
It is sectional drawing which follows the EE line of (a).

FIG. 3 is a perspective view illustrating an embodiment of a method for manufacturing a chip thermistor of the present invention.

FIG. 4 is a sectional view showing a conventional chip thermistor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Thermistor body 2A, 2B, 2a, 2b, 2c, 2d, 2e Internal electrode 3A, 3B, 3C, 3D Surface electrode 4 Glass layer 5A, 5B External electrode 10A, 10B Chip-type thermistor 11, 12, 13 Thermistor green sheet Reference Signs List 14 conductive layer 15 sintered body 18 prismatic thermistor element 19 chip-shaped thermistor element

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yasutaka Maeda 2270 Yokoze, Yokoze-cho, Chichibu-gun, Saitama F-term in the Electronic Technology Laboratory, Mitsubishi Materials Corporation 5E032 BA23 BB10 CA02 CC06 CC14 CC16 5E034 BB01 DA07 DB04 DC01 DC03 DE07 DE17 5E336 AA04 CC32 CC38 CC42 CC60 EE03 GG11

Claims (2)

[Claims] 1. A thermistor element having an internal electrode formed therein and a surface electrode formed on a side surface, an insulating protective layer formed on four side surfaces of the thermistor element, and both ends of the thermistor element A chip-type thermistor comprising: an external electrode formed on a surface. 2. a step of laminating a plurality of thermistor green sheets each having a conductive layer for forming an internal electrode formed on at least a part of the thermistor green sheets and firing the laminated sheets to produce a thin plate-shaped thermistor sintered body; Forming a conductive layer for forming a surface electrode on the upper and lower main plate surfaces of the sintered body; forming an insulating coating layer on the upper and lower main plate surfaces of the thermistor sintered body having the conductive layer formed thereon; Cutting the sintered body of the thermistor on which the insulating coating layer is formed into a rectangular shape to obtain a prismatic thermistor body; and forming no insulating coating layer of the prismatic thermistor body. Forming an insulating coating layer on two side surfaces; cutting a prism-shaped thermistor element body having an insulating coating layer on four side surfaces in a direction perpendicular to the longitudinal direction to form a chip-shaped thermistor element; Obtaining, Forming external electrodes on both end faces of the chip-shaped thermistor element body where the insulating coating layer is not formed.