JPH08250307A - Chip thermistor - Google Patents

Abstract

PURPOSE: To increase the dimensional accuracy between electrodes by electrically connecting outer electrodes to other terminals of inner electrodes and surface electrodes and forming external electrodes facing at both ends of a multilayer body so as to expose one end of each surface electrode. CONSTITUTION: Thermistor layers 3a and 3b are formed one on another to form a multilayer body 7, a pair of inner electrodes 9a and 9b are formed in the body 7 and two pairs of surface electrodes 13a and 13b are formed on the upper and lower faces 15a and 15b of the body 7. A pair of external electrodes 11a and 11b are formed at both ends 17a and 17b of the body 7. The other end of one electrode 9a is connected to the electrode 11a and the other end of the other electrode 9b is connected to the electrode 11b. The other end of the electrode 13a and that of the electrode 13b are connected to the external electrodes 11a and 11b, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip thermistor, and more particularly to a chip thermistor such as an NTC thermistor and a PTC thermistor.

[0002]

2. Description of the Related Art Conventionally, a chip thermistor 1 is shown in FIG.
As shown in FIG. 3, since the terminals are connected by soldering when mounted on a printed board, the terminal electrodes 5 for soldering are formed at both ends of the thermistor element body 3.

In such a chip thermistor 1, the resistance value is governed by the interelectrode dimension X1 of the terminal electrode 5.

By the way, the terminal electrode 5 is formed by a dipping method in which the end surface of the thermistor element body 3 is dipped and adhered on the electrode paste.

However, in the conventional dipping method, the dimensional accuracy of the interelectrode dimension X1 of the terminal electrode 5 varies due to the thickness of the conductive paste, the immersion depth of the thermistor element body 3, etc., which affects the resistance value. Therefore, a highly accurate chip thermistor 1 having stable characteristics cannot be obtained.

A chip thermistor 1 as shown in FIG. 8 has a rectangular parallelepiped laminated body 7 in which the thermistor layers 3a and 3b are laminated and integrated, and one end of each is formed on the same surface of the thermistor layer 3b. It is provided with a pair of internal electrodes 9 provided so as to face each other, and a pair of external electrodes 11 formed so as to be connected to the other end of the internal electrode 9 and to face both ends of the stacked body 7.

In such a chip thermistor 1, most of the resistance value (about 80 to 90%) is governed by the inter-electrode dimension Y1 of the internal electrode 9. The inter-electrode dimension X2 of the external electrode 11 does not so much influence.

The internal electrodes 9 are formed on the surface of the thermistor layer 3b by screen printing. Since this screen printing is performed in a state where the thermistor layer 3b before lamination is accurately positioned, it can be managed accurately,
Therefore, it is possible to obtain a chip thermistor having a small variation in size and a high resistance value accuracy.

[0009]

However, the above-mentioned FIG.
In the chip thermistor as shown in (1), most of the resistance value (about 80 to 90%) is dominated by the inter-electrode dimension Y1 of the internal electrode 9 formed with high accuracy, but the inter-electrode dimension X2 with variation in accuracy is present. Of the internal electrode and the external electrode on the side opposite to the internal electrode have no effect on the resistance value (about 10 to 20).
%), And it was difficult to demand higher precision.

It is an object of the present invention to provide a highly accurate chip thermistor having a small variation in resistance value by improving the dimensional accuracy between electrodes.

[0011]

SUMMARY OF THE INVENTION The present invention has completed a chip thermistor to solve the above problems. The chip thermistor of the present invention includes a laminated body in which a plurality of thermistor layers are laminated, and a pair of internal portions that are formed inside the laminated body and have one ends facing each other on the same surface of the thermistor layer. Electrodes, a pair of surface electrodes formed on the same surface of the laminate so that their one ends face each other, and electrically connected to the other ends of the internal electrodes and the surface electrodes, and the surface electrodes. And a pair of external electrodes formed so as to face each other at both ends of the laminated body so that one end of the external electrode is exposed.

That is, since the external electrodes are formed at both ends of the laminated body so that one end of the surface electrode electrically connected to the external electrode is exposed, the inter-electrode dimension of the surface electrode is the resistance value of the chip thermistor. However, the inter-electrode dimension of the external electrodes does not affect the resistance value, and high dimensional accuracy is not required. Therefore, the external electrode can be easily formed by a so-called dipping method in which the laminated body is immersed in the electrode paste. Further, the surface electrode can be formed in advance with high dimensional accuracy on the surface of the thermistor layer by a method such as screen printing, similarly to the internal electrode.

Further, in the chip thermistor of the present invention, the surface electrodes are formed on both ends of the first main surface of the laminate and the second main surface facing the first main surface. The inter-electrode distance of the surface electrode on the main surface is preferably longer than the inter-electrode distance of the internal electrode.

That is, the resistance value of the surface electrode strongly depends on the internal electrode in consideration of solder erosion and damage due to external force when the chip thermistor is mounted on the printed circuit board by soldering. What you are doing is effective.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A chip thermistor which is an embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a sectional view of this embodiment, and FIG. 2 is a perspective view of this embodiment. The chip thermistor 1 of the present embodiment has a laminated body 7 formed by vertically stacking the thermistor layers 3a and 3b, a pair of internal electrodes 9a and 9b formed inside the laminated body 7, and a laminated body. 7 upper surface 15a and lower surface 15b
Two pairs of surface electrodes 13a and 13b respectively formed on and
And a pair of external electrodes 11a and 11b formed on both ends 17a and 17b of the laminated body 7.

The thermistor layers 3a, 3b have a flat plate shape, and are made of a ceramic body containing Mn, Ni, Co, Cu, Fe or the like as a main component.

The pair of internal electrodes 9a and 9b are formed inside the laminated body 7 on the same surface of the lower thermistor layer 3b so that their respective ends face each other.

The other end of one internal electrode 9a is connected to the external electrode 11a provided at one end 17a of the laminated body 7.

Further, the other end of the other internal electrode 9b is connected to the external electrode 11b provided at the other end 17b of the laminated body 7.
It is connected to the.

Here, as shown in FIG.
The a and 9b have a flat plate shape, and the width W1 of the internal electrodes 9a and 9b in the width direction is smaller than the width W2 of the thermistor element body 21 for the internal electrodes. This is because it is preferable that W1 is smaller than W2 and the internal electrodes are not exposed to the outside in consideration of weather resistance such as heat resistance, cold resistance, and humidity resistance.

Here again, the ends 9 of the internal electrodes 9a, 9b are
a1 and 9b1 are formed to have substantially the same size as the widthwise size W2 of the internal electrode thermistor element body 21. As a result, the connection distance between the external electrode and the external electrode becomes long, so that the reliability of the connection between the internal electrode and the external electrode can be improved. The ends 9a1 and 9b1 are connected to the external electrode 11a,
Since it is covered with 11b, it is not exposed to the outside.

The internal electrodes 9a and 9b are made of Pt and A.
It is made of a metal containing g, Pd, Ni, Cu or the like or a composite material thereof, and is formed as a thick film by screen printing.

The metals used for the internal electrodes 9a and 9b are not limited to these, and any metal can be used as long as it can be co-fired with the ceramic body.

The pair of surface electrodes 13a, 13b are arranged so that their ends are opposed to each other, both ends of the upper surface 15a which is the first main surface of the laminate 7 and both ends of the lower surface 15b which is the second main surface. , Respectively, and there are two pairs in total.

The other end of the one surface electrode 13a is connected to the external electrode 11a provided from one end 17a of the laminated body 7 toward the upper surface 15a and the lower surface 15b of the laminated body 7.

Further, the other end of the other surface electrode 13b is
The external electrode 11 provided on the other end 17b of the laminated body 7
connected to b.

Furthermore, the surface electrodes 13a and 13b are
Like the internal electrodes 9a and 9b, it has a flat plate shape, and P
It is made of a metal containing t, Ag, Pd, Ni, Cu or the like or a composite material thereof, and is formed as a thick film by screen printing.

The metals used for the internal electrodes 13a and 13b are not limited to these, and any metal can be used as long as it can be simultaneously fired with the ceramic body.

The external electrodes 11a and 11b are formed on both ends 17a and 17b of the laminated body 7, and are connected to the other ends of the internal electrodes 9a and 9b and the other ends of the surface electrodes 13a and 13b (two above and below). It is formed so that it is electrically connected and one end of the surface electrodes 13a and 13b is exposed.

Since the external electrodes 11a and 11b are coated on the surface electrodes 13a and 13b printed on the upper surface 15a and the lower surface 15b of the laminated body 7, the external electrodes 11a and 11b are different from the upper surface 15a and the lower surface 15b of the laminated body 7. Not in contact.

The external electrodes 11a and 11b are made of Ag,
It is a multi-layer electrode having a three-layer structure made of a single material or a composite material of Pd, Ni, Cr, Sn, Pb or the like.

That is, the innermost first layer is a thick film layer made of Ag or Ag-Pd, and is formed by the dip method. Next, the second layer formed outside the first layer is a plating layer made of Ni. Note that C
It is also possible to use r or Ni-Cr. Further, the third layer formed outside the second layer is Sn or S
It is a plating layer made of n-Pb.

Here, the inter-electrode dimension Y2 of the internal electrodes 9a and 9b, the inter-electrode dimension X3 of the surface electrodes 13a and 13b, and the inter-electrode dimension X4 of the external electrodes 11a and 11b shown in FIG. 1 are Y2 <X3. <There is a relationship of X4.

Therefore, the electrode that most affects the resistance value of the chip thermistor 1 is the internal electrode 9 having the shortest inter-electrode dimension.
a and 9b, and the next influential electrode is the surface electrode 13 having the shortest interelectrode dimension next to the internal electrodes 9a and 9b.
a and 13b.

The influence of the internal electrodes 9a and 9b on the resistance value is about 80 to 90%.
The influence of b on the resistance value is about 20 to 10%.

Considering that when the chip thermistor 1 is mounted on a printed circuit board by soldering, the surface electrode may be eroded by solder, or the surface electrode may not be protected and may be damaged by an external force. The fact that the resistance value depends almost on the internal electrode 9 is not a little effective.

Since the internal electrodes 9a and 9b and the surface electrodes 13a and 13b are both formed by screen printing, dimensional accuracy can be controlled without causing electrode sagging. That is, the inter-electrode dimensions Y2 and X3 can be managed with high accuracy, and a high-quality chip thermistor 1 with a small variation in resistance value can be obtained.

Since the external electrodes 11a and 11b are formed by the dipping method, it is difficult to form them with high precision, but the inter-electrode dimension X4 of the external electrodes 11a and 11b is difficult.
Does not contact the laminate 7 on the surface 15 having the surface electrodes 13a and 13b, and therefore has almost no effect on the resistance value.

By this screen printing method, the internal electrodes 9a and 9b formed inside the laminated body and the surface electrodes 13a and 13b formed on the same surface of the laminated body 7 are less susceptible to electrode sag, and Variations in size are suppressed. Therefore, the thermistor layers 3a, 3
The dimensional accuracy is very high as compared with an electrode formed by immersing b or by a method similar thereto.

Therefore, since the internal electrodes 9a, 9b and the surface electrodes 13a, 13b can be formed with high accuracy, the inter-electrode dimensions Y2, X3 of the internal electrodes 9a, 9b and the surface electrodes 13a, 13b are also formed with high dimensional accuracy. be able to.

The resistance value of the chip thermistor 1 having the internal electrodes 9a and 9b is mainly determined by the inter-electrode dimension Y2 of the internal electrodes 9a and 9b, but in order to require higher accuracy, the surface electrode 13a, It is also necessary to improve the accuracy of the inter-electrode dimension X3 of 13b. Therefore, as in the present invention, the internal electrodes 9a and 9b and the surface electrodes 13a and 1 have high dimensional accuracy.
If 3b can be formed, the resistance value can be adjusted with high accuracy, and a thermistor element having a small resistance value distribution can be obtained.

Next, with reference to FIGS. 3 to 6, a method of manufacturing a chip thermistor which is an embodiment of the present invention will be described. (1) First, a raw thermistor element body, that is, a so-called ceramic green sheet, which is a thermistor element body 21 for internal electrodes, is prepared, and a thick film is formed by screen printing, and its upper surface 21a
A pair of internal electrodes 9a and 9b are formed on both end sides of the so that their one ends face each other and dried (FIG. 3).

(2) Next, two raw thermistor elements, that is, so-called ceramic green sheets, are prepared for the surface electrode thermistor element 19, and each of them is a thick film formed by screen printing on both ends of the upper surface 19a. A pair of surface electrodes 13a and 13b are formed so that their one ends face each other, and dried (FIG. 4).

(3) Next, the above-mentioned thermistor element body for internal electrode 21 is arranged substantially at the center, and the thermistor element body for internal electrode 21 is a raw thermistor element body above and below which the electrode is not formed. A predetermined number of dummy sheets 23 are stacked, and the above two thermistor element bodies 19 for surface electrodes are stacked on the upper and lower sides of the dummy sheets 23 so as to face each other (FIG. 5).

(4) Next, the thermistor element bodies stacked as described above are integrally pressed and fired to form a ceramic laminated body 7 (FIG. 6).

(5) Next, the other ends of the internal electrodes 9a and 9b and the other ends of the surface electrodes 13a and 13b (two above and below).
And the external electrodes 11a, 1b on both ends of the laminate 7 so that one ends of the surface electrodes 13a, 13b are exposed.
The first layer 1b is formed as a thick film by the dipping method and baked. Then, the surface of the first layer is plated with the second layer, and the surface of the second layer is plated with the third layer (FIG. 2).

As described above, the chip thermistor of this embodiment is manufactured.

By the way, the chip thermistor and the method for manufacturing the same according to the present invention are not limited to the above embodiments, but various modifications can be made within the scope of the present invention.

For example, in the above embodiment, the relationship between the inter-electrode dimension Y2 of the internal electrodes, the inter-electrode dimension X3 of the surface electrodes and the inter-electrode dimension X4 of the external electrodes is Y2 <X3 <X4.
2 and X3 may be equal, that is, Y2≤X3 <X4. This is because both the internal electrode and the surface electrode are formed with high precision by screen printing, and therefore there is no functional problem even if the influence on the resistance value of the surface electrode increases.

Further, for example, in the above-mentioned embodiment, the laminated body has a rectangular parallelepiped shape, but if a disc-shaped thermistor element body is used, a laminated body having a columnar shape is obtained.

Further, for example, in the above embodiment, the dummy sheet is provided between the thermistor element body for surface electrode and the thermistor element body for internal electrode, but the thickness of the dummy sheet is not particularly limited. The surface electrode and the internal electrode may be adjusted to have a desired distance so as not to come into direct contact with each other.

Further, for example, in the above-described embodiment, the external electrodes of the chip thermistor are formed on the upper and lower surfaces and the three side surfaces of the laminated body by forming the individual chip-shaped laminated bodies and then attaching the external electrodes thereto. Although the external electrodes of the chip thermistor are five-sided electrodes, the external electrodes of the chip thermistor are formed by attaching the external electrodes to a laminated body that is a mother substrate in which rod-shaped thermistor elements are laminated It may be a three-sided electrode formed on the upper and lower surfaces and the end surface.

[0053]

According to the chip thermistor of the present invention, it is possible to manufacture a highly accurate chip thermistor with a small variation in the resistance value by increasing the dimensional accuracy between the electrodes.

Further, since the yield is increased, the manufacturing cost can be reduced.

Moreover, the quality of the chip thermistor according to the second aspect is further improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a perspective view showing an embodiment of the present invention.

FIG. 3 is an explanatory view showing a part of the manufacturing process of the embodiment of the present invention.

FIG. 4 is an explanatory view showing a part of the manufacturing process of the embodiment of the present invention.

FIG. 5 is an explanatory view showing a part of the manufacturing process of the embodiment of the present invention.

FIG. 6 is an explanatory view showing a part of the manufacturing process of the embodiment of the present invention.

FIG. 7 is an explanatory diagram showing an example of a conventional chip thermistor.

FIG. 8 is an explanatory diagram showing another example of a conventional chip thermistor.

[Explanation of symbols]

1 Chip Thermistor 3 Thermistor Element 3a, 3b Thermistor Layer 5 Terminal Electrode 7 Laminated Body 9, 9a, 9b Internal Electrode 9a1, 9b1 End of Internal Electrode 11, 11a, 11b External Electrode 13, 13a, 13b Surface Electrode 15a Top Surface 15b Lower surface 17a, 17b Both ends 19 Thermistor element body for surface electrode 19a Upper surface of thermistor element body for surface electrode 21 Thermistor element body for internal electrode 21a Upper surface of thermistor element body for internal electrode 23 Dummy sheet X1 Electrode dimension of terminal electrode X2, X4 Distance between electrodes of external electrode X3 Distance between electrodes of surface electrode Y1, Y2 Distance between electrodes of internal electrode W1 Width direction of internal electrode W1 Width dimension of thermistor element for internal electrode

Claims (2)

[Claims] 1. A laminated body in which a plurality of thermistor layers are laminated, and a pair of internal electrodes which are formed inside the laminated body and on the same surface of the thermistor layer so that one ends thereof face each other. A pair of surface electrodes formed on the same surface of the laminated body so that the ends thereof face each other, and electrically connected to the respective other ends of the internal electrode and the surface electrode, and one end of the surface electrode. And a pair of external electrodes formed so as to face each other at both ends of the laminate so as to expose the chip thermistor. 2. The surface electrodes are respectively formed on both ends of a first main surface of the laminate and a second main surface facing the first main surface, and the front surface electrode of each of the main electrodes is formed on each main surface. The chip thermistor according to claim 1, wherein the inter-electrode distance is longer than the inter-electrode distance of the internal electrodes.