JP2001237107A - Laminated chip thermistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated chip thermistor which can be manufactured at a high yield by reducing the variation of its resistance value. SOLUTION: This laminated chip thermistor is constituted by arranging internal electrodes 12A, 12B, and 12C, each of which is composed of a pair of electrodes arranged in the same plane with a gap section in between, in a vertically laminated state in a box-like blank thermistor body 11 and external electrodes 13 which are connected to the internal electrodes 12A, 12B, and 12C on the side faces of the body 11 in a state where the electrodes 13 are extended to the edge sections of the upper and lower surfaces of the body 2. In this thermistor, high-resistivity layers 15a and 15b having higher resistivities than insulating layers or the body 11 has are respectively arranged among the electrodes 12A, 12B, and 12C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated chip thermistor, and more particularly, to a laminated chip thermistor having a box-shaped chip structure suitable for surface mounting, in which a plurality of thermistor element layers and a pair of internal electrode layers are laminated. The present invention relates to a multilayer chip thermistor configured as described above.

[0002]

2. Description of the Related Art A thermistor is a resistor element having a positive or negative temperature coefficient, particularly a negative temperature coefficient (NTC: Negati).
ve Temperature Coefficient)
It is widely used as a resistance circuit element for applications such as temperature compensation in various electronic circuits. As such a circuit element,
As a structure that can be surface-mounted on a printed circuit board, for example, a multilayer chip thermistor shown in FIG. 4A is known. The laminated chip thermistor has a box-shaped chip structure suitable for surface mounting.
It is about 3 mm and the short side is about 0.5 to 1.5 mm, which is an extremely small component.

The multilayer chip thermistor 10 has an internal electrode 1 consisting of a pair of left and right electrodes inside a thermistor body 11.
A plurality of layers 2A, 12B, and 12C are arranged in layers separated from each other in the vertical direction. That is, a pair of left and right electrodes 12A (a), 12A shown in the figure is provided on the surface of a thin sheet-shaped thermistor body.
(B) is arranged with a gap G in the center, and is formed by laminating a plurality of layers. Internal electrodes 12A, 12
B and 12C are respectively connected to the external electrodes 13 at both left and right ends of the box-shaped thermistor element 11 in the figure. The thermistor element body 11 is a semiconductor ceramic formed by dispersing a powder of a metal oxide or the like in a solvent to form a ceramic green sheet by a doctor blade method or the like, and laminating and firing a plurality of layers. Internal electrodes 12A, 12B, 1
2C is formed by applying a thick film paste such as Ag-Pd on the green sheet constituting the thermistor body by screen printing or the like, and firing the green sheet together with the thermistor body at a high temperature. The external electrode 13 is coated with a thick-film paste such as Ag-Pd so as to extend from the side end surface of the box-shaped thermistor body 11 to the upper and lower surfaces, and is exposed on the side end face of the box-shaped thermistor body 11. It is formed by performing Ni plating, solder plating, or Sn plating after connecting to the internal electrode and firing.

In such a thermistor element, the resistance value is such that a current flows between the internal electrodes 12A, 12B and 12C, for example, from the electrode 12A (a) to the electrode 12A (b) in a distributed manner in the thermistor body 11. , The current distribution path and the specific resistance of the thermistor body.
For this reason, a thermistor element having a low resistance can be obtained by providing the internal electrodes 12A and reducing the size of the gap G between the electrodes and increasing the number of stacked internal electrodes.

That is, the resistance accuracy of such a thermistor element is governed by the printing accuracy of the internal electrode, the thickness of the thermistor element green sheet, and the lamination accuracy. However, as described above, the laminated chip thermistor has a very small size, and is manufactured by printing the internal electrodes by screen printing, laminating green sheets, and firing. For this reason, the printing resistance of the internal electrodes and the misalignment of the green sheets of the thermistor body greatly change the resistance value.

FIG. 4 (b) shows the positional deviation of the internal electrode printing.
Internal electrode 1 due to misalignment of green sheets
The case where 2A and 12B deviate from the normal position (12C) is shown. That is, the internal electrode 12A is shifted to the left by the distance B,
The case where the internal electrode 12B is shifted to the right by the distance A is shown. Also, the case where the thickness of the green sheet is thin between the internal electrodes 12A and 12B and the thickness between them is close to C is shown. In such a case, the left and right inner electrodes 12A and 12B abnormally approach each other at the portion indicated by the arrow D in the drawing.
A leak state occurs and the resistance value decreases. Further, since the distance between the electrodes is reduced, the load is concentrated. When the resistance value fluctuates in this way, there is a problem that the manufacturing yield is reduced.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and provides a multilayer chip thermistor capable of reducing variations in resistance and thereby ensuring a high production yield. The purpose is to do.

[0008]

According to a first aspect of the present invention, there is provided a box-shaped thermistor element comprising a plurality of internal electrodes in which a pair of electrodes are arranged on the same surface and separated by a gap. In a multilayer chip thermistor in which external electrodes connected to the internal electrodes of the plurality of layers are arranged around the upper and lower surfaces from the side surfaces of the box-shaped thermistor element, between the internal electrodes of the plural layers A multilayer chip thermistor, wherein an insulating layer or a layer having a higher specific resistance than the specific resistance of the thermistor element is disposed.

Since the insulating layer or the high resistivity layer is arranged between the internal electrodes of a plurality of layers, the internal electrode of one layer and the internal electrode of the layer adjacent thereto are insulated, and almost no current flows between them. . Therefore, even if an internal electrode of an adjacent layer moves with respect to a certain layer due to displacement, almost no current flows between the internal electrodes, so that no current flows to other electrodes and no interference occurs between the internal electrodes. Therefore, since the resistance value is determined by the accuracy of the gap between the pair of internal electrodes and the specific resistance of the thermistor element, it is possible to manufacture a thermistor with good resistance value accuracy.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a laminated chip thermistor according to an embodiment of the present invention. Inside the thermistor body 11, a plurality of layers of internal electrodes (here, three layers of internal electrodes) 12A, 1
2B and 12C are arranged, and each electrode 12A, 12C
The pair of electrodes B and 12C are external electrodes 13 and 13 respectively.
Are the same as those shown in FIG. In the present invention, an insulating layer or a layer 15a having a high specific resistance to the specific resistance of the thermistor element is disposed between the internal electrode 12A and the internal electrode 12B, and similarly between the internal electrode 12B and the internal electrode 12C. Insulation layer or high resistivity layer 1
5b are arranged. Here, the layer having a high specific resistance is a layer having a specific resistance higher than the specific resistance of the thermistor body, for example, by one or two digits, and is a layer in which substantially no current flows.

In this embodiment, the insulating layer or high resistivity layer 15a, 15b is a box-shaped thermistor element 1
1 are arranged on the entire surface of the lamination surface. That is, the insulating layer or the high specific resistance layer 15 is interposed between the sheet-shaped thermistor bodies (green sheets), and these are laminated to form a box-shaped thermistor body.

Therefore, the internal electrodes 12A, 12B, 12C
Is composed of a pair of left and right electrodes, respectively, and the current flowing through the gap between the pair of left and right electrodes via the thermistor element is completely separated by the insulating layers or the high resistivity layers 15a and 15b. That is, the current flowing from one of the external electrodes 13 is shunted to the internal electrodes 12A, 12B, and 12C, flows through the channels between the electrodes in the thermistor element separated by the insulating layer or the high specific resistance layer, and the other. No current flows through the internal electrodes. Therefore, the internal electrodes 12
The problem that the resistance value fluctuates even if a deviation occurs in the left-right direction between A, 12B, and 12C is solved.

FIG. 2 shows another embodiment of the present invention. Also in this embodiment, insulating layers or high resistivity layers 16a and 16b are arranged between a plurality of internal electrodes so that a current flowing between a pair of internal electrodes does not interfere with a current flowing between other internal electrodes. Common in that That is, a plurality of (here, three layers) internal electrodes 12A, 12B, and 12C are arranged on the box-shaped thermistor element 11, and these internal electrodes are connected to the external electrodes 13 arranged on the side end surfaces of the thermistor element 11. In this structure, insulating layers or high resistivity layers 16a and 16b between a plurality of internal electrodes are arranged.
In this embodiment, the insulating layer or the high resistivity layer 1 disposed between the internal electrodes inside the thermistor body 11 is used.
6a and 16b are large enough to cover the gap between the pair of internal electrodes, not the entire surface as shown. As a result, the current path flowing in the gap between the pair of internal electrodes is formed by the insulating layer or the high resistivity layer 16a,
It is distributed in the space separated by 16b and does not interfere with the current path flowing in the gap between the other internal electrodes. Since there is almost no current path except in the vicinity of the gap between the internal electrodes, the same effect of preventing a variation in resistance value as when an insulating layer or a high resistivity layer is disposed on the entire surface can be obtained. Since the insulating layer or the high resistivity layer partially enters the thermistor body, the influence of the insulating layer or the high resistivity layer entering the entire thermistor body can be reduced.

Next, an outline of an example of a method of manufacturing the multilayer chip thermistor will be described. Disperse powders of metal oxides and the like that provide an appropriate temperature coefficient in a solvent,
A green sheet of a thermistor body is formed by a doctor blade method or the like, and an internal electrode is coated with a thick film paste of, for example, Ag-Pd by screen printing. On the other hand,
In the case of the embodiment shown in FIG. 1, a thick film paste of an insulating film or a thick film paste of a high-resistance body is applied to the entire green sheet of the thermistor body, and in the case of the embodiment shown in FIG. The coating is applied in a similar manner partially by using a method such as screen printing, including the periphery of the gap between them. Here, as the thick film paste of the insulating film or the high-resistance body, for example, a paste containing alumina as a main component can be used. Also,
When forming an insulating film (or high-resistance film) on the entire surface,
An insulating or high-resistance green sheet may be laminated. Then, a green sheet having an internal electrode formed on its surface and a green sheet having an insulating film or a high-resistance film formed on its surface are alternately stacked and pressed. Thereafter, the multilayer chip thermistor of the present invention is manufactured by dicing, formation of an end face (external) electrode, baking, and plating of the external electrode in accordance with a normal manufacturing method of a multilayer chip thermistor.

FIG. 3 shows the results of comparison between the resistance histograms of the multilayer chip thermistor of the present invention and a conventional multilayer chip thermistor. (A) shows a resistance value histogram of the conventional multilayer chip thermistor, and shows that the distribution is outside the allowable range, for example, ± 1%, which is the target allowable range. On the other hand, (b) shows a resistance value histogram of the multilayer chip thermistor of the present invention, and shows that the resistance value falls well within a target allowable value range of ± 1%.

In the above embodiment, an example in which the number of the internal electrodes is three has been described. However, it goes without saying that the gist of the present invention can be similarly applied to any number of layers.

[0018]

As described above, according to the present invention, an insulating layer or a high resistivity layer is arranged between a plurality of internal electrodes in a multilayer chip thermistor. As a result, even if printing misalignment of the internal electrodes or misalignment of the green sheet occurs, current flows only between the pair of internal electrodes facing each other via the air gap and does not interfere with the internal electrodes of other layers. Variation can be suppressed. Therefore,
According to the present invention, the production yield of the multilayer chip thermistor can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a multilayer chip thermistor according to an embodiment of the present invention.

FIG. 2 is a sectional view of a multilayer chip thermistor according to another embodiment of the present invention.

FIG. 3 is a histogram showing a distribution of resistance values;
(A) shows the distribution of the conventional multilayer chip thermistor, and (b) shows the distribution of the multilayer chip thermistor of the present invention.

4A is a cross-sectional view of a conventional multilayer chip thermistor, and FIG. 4B is a cross-sectional view showing a case where the position of an internal electrode is shifted.

[Explanation of symbols]

Reference Signs List 10 laminated chip thermistor 11 thermistor body 12A, 12B, 12C pair of internal electrodes 13 external electrode 15a, 15b insulating layer or high resistivity layer 16a, 16b partially disposed insulating layer or high resistivity layer

Claims (3)

[Claims] 1. A box-shaped thermistor body, a plurality of internal electrodes in which a pair of electrodes are spaced apart from each other via a gap on the same surface are stacked and arranged, and connected to the internal electrodes of the plurality of layers. A stacked chip thermistor in which external electrodes to be wrapped around the upper and lower surfaces from the side surfaces of the box-shaped thermistor element, between the internal electrodes of the plurality of layers, the insulating layer or the specific resistance of the thermistor element A multilayer chip thermistor characterized in that a layer having a high specific resistance is arranged. 2. The multilayer chip thermistor according to claim 1, wherein the insulating layer or the layer having a high specific resistance is disposed on the entire surface of the lamination surface between the plurality of internal electrodes. 3. The semiconductor device according to claim 1, wherein the insulating layer or the high resistivity layer is partially disposed so as to cover at least a gap between the pair of internal electrodes disposed on the same surface. The multilayer chip thermistor according to claim 1.