JPS5911602A - Negative temperature coefficient thermistor and method of producing same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a negative characteristic thermistor used as a temperature detection element and a method for manufacturing the same.

Prior Art The general structure of this type of conventional negative temperature thermistor is as shown in FIG.
It had a structure in which electrodes 2 and 3 were deposited on both end faces of the board so as to cover the entire surface thereof.The electrodes 2 and 3 were formed by printing silver alloy paste or the like.

Disadvantages of the prior art However, the conventional negative characteristic thermistor has a thermistor body l
Since the structure is formed on the entire surface of both end faces of the electrode 2-3,
When a voltage is applied between the electrodes, silver migration occurs in which silver migrates and is deposited from the electrodes 2 or 3 along the outer surface of the negative characteristic thermistor element 1, often resulting in a short circuit between the electrodes. In particular, this type of negative characteristic thermistor is often a minute component with an external dimension of about 2 m/m, and silver migration may cause a short circuit between the electrodes. Since it is used as a temperature detection element in a high temperature and humidity atmosphere such as in various cooking appliances, there are inherent problems such as significantly accelerated silver migration, and 4A is required to suppress and prevent silver migration. This is an extremely important matter from the standpoint of maintaining the quality of the garment. A method of suppressing silver migration by using a noble metal such as gold, platinum, or palladium instead of silver has been proposed, but this method is impractical because it increases the cost of the product.

Gray Shiran to Mata and Silverma. Another known method is to coat the electrode 2.3 with a metal layer such as solder, but this method is expensive, tends to cause problems such as a decrease in temperature detection sensitivity, and has low temperature detection sensitivity. Since it is placed in a high-temperature atmosphere, there are problems such as difficulty in selecting the metal material to be coated and other difficulties in design.

OBJECTS OF THE INVENTION Therefore, the present invention provides an inexpensive and highly reliable negative characteristic thermistor that can reliably prevent the above-mentioned silver migration phenomenon with a simple configuration, and manufactures this negative characteristic thermistor. The purpose is to provide a manufacturing method suitable for

Structure of the Invention In order to achieve the above object, the negative characteristic thermistor according to the present invention has electrodes coated on both end faces of a negative characteristic thermistor element having a rectangular parallelepiped shape with a gap separated from the outer periphery of the element. It is characterized by the fact that it has been formed.

In addition, the manufacturing method according to the present invention for obtaining an L-symbol mister includes a step of depositing a metal layer on the front and back surfaces of a plate-shaped thermistor element body, and a process of partially removing the metal layer and vertically disposing the metal layer. and a step of forming a grid-like gap portion in the horizontal direction, and a step of cutting the thermistor element body along the gap portion.

Embodiment 2 is a perspective view of a negative characteristic thermistor according to the present invention, and 3 is a perspective view of a negative characteristic thermistor according to the present invention.
The figure is also a side view. In this embodiment, on both end faces of the negative characteristic thermistor element l formed in the shape of a rectangular parallelepiped,
Inward by a gap Gl from the four outer peripheral edges of the negative characteristic thermistor element body l.

It has a structure in which an electrode 2.3 whose conductive component is a metal component such as silver, a silver-palladium alloy, or gold is formed on a cover 71.

In general, metal components constituting electrodes are easy to move in the direction of the electric field, but have a property that they are difficult to move in a direction different from the electric field, especially in a direction perpendicular to the electric field. Therefore, if a structure is adopted in which the electrode 2.3 is formed inside the outer periphery of the negative temperature coefficient thermistor body 1 by the gap Gl, as in the present invention, the electrode 2.
When a voltage is applied between the electrodes 3 and 3, the plane portion with the gap Gl becomes a plane perpendicular to the direction of the electric current directed toward the electrodes 2-3, and acts as a barrier to the silver migration graciggon. Therefore, the movement of the metal component constituting the electrode 2.3 is suppressed by the cap Gl. Therefore, silver migration is prevented from occurring when the electrodes 2.3 are made of silver electrodes.

Next, a method for manufacturing the above negative characteristic thermistor will be explained. FIGS. 4(A) to 4(C) are diagrams showing the manufacturing process. First, as shown in FIG. 4(A), metal layers 201 and 301 are formed on the entire front and back surfaces of the thermistor body 101 in the form of a rectangular plate or a disk. The metal layer 20
1 and 3′O1 are electrodes 2.3, so
The electrode material is made of the metal mentioned above, such as silver, silver-palladium alloy, or gold, as a conductive component. The method for forming the metal layers 201 and 301 involves preparing an electrode paste containing the metal as a conductive component, and applying it to the thermistor body 1 by means such as screen printing.
The electrode paste that is applied and baked on 01 may be a screen printing method, a vapor deposition method, a sputtering method, or the like.

Next, as shown in FIG. 4(B), the metal layers 201 and 301 are partially removed to form a lattice-shaped gap Gl that intersects vertically and horizontally. After this, Figure 4 (C
), by cutting the thermistor element lO1 into a grid shape along the gap G1, the parts shown in FIGS.
The negative characteristic thermistor according to the present invention shown in the figure is obtained.

As a method for forming the gap portion Gl, a photo-etching method or an etching method is suitable. Since this type of negative characteristic thermistor usually has a very small outer diameter of, for example, about 2 m/m, it is necessary to maintain extremely high dimensional accuracy of the electrode formed at E and the cap Gl that separates the electrode. There is. The photo-etching method, which is widely used in semiconductor manufacturing technology, can form extremely fine patterns, so by using this method, the dimensional accuracy of the electrode and the camp G1 around it can be maintained at a very high level. I can do it. Figures 5 (A) to (D) are photos.

FIG. 3 is a diagram showing an example of an etching process. First, Figure 4 (
In step A), a metal layer 2 is formed on both sides of the thermistor element 101.
01 and 301, as shown in FIG. 4(A), the L of the metal layer 201 or 301 is covered with a photomask 4 made of photosensitive resin or the like, and then as shown in FIG. 5(B). As shown in , a negative or positive 5 with the gap Gl pattern formed thereon is placed on this photomask 4,
By looking at the light, the photo mask 4 is exposed according to the pattern. After this, Figure 5 (C
) as shown in FIG.
By performing etching 01, a gap Gl having a pattern shown in FIG. 4(B) is formed.

Effects of the present invention As described above, the negative characteristic thermistor according to the present invention has
On both end faces -H of the rectangular parallelepiped negative characteristic thermistor body,
Since the cap is depressed from the outer periphery of the element body and the electrode is deposited thereon, the silver migration phenomenon of the electrode can be reliably prevented by a simple structure in which the gap is used as a barrier part. Thus, it is possible to provide a low-cost, highly reliable negative characteristic thermistor.

Further, the method for manufacturing a thermistor according to the present invention includes a step of depositing and forming a metal layer on the front and back surfaces of a plate-shaped thermistor body, and partially removing the metal layer to form a lattice pattern in the vertical and horizontal directions. The negative characteristic thermistor can be manufactured efficiently because the method includes a step E of forming a gap portion and a step of cutting the thermistor body along the gap portion ifI.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a conventional negative characteristic thermistor, and FIG. 2 is a perspective view of a negative characteristic thermistor according to the present invention. FIG. 3 is a side view thereof, FIGS. 4(A) to 4(C) are diagrams showing the steps of the manufacturing method according to the present invention, and FIGS. 5(A) to
(D) is a diagram showing an example of a photo-etching process. 1... Negative characteristic thermistor element body 2.3... Electrode G1... Gap Figure 4 (A) (C)

Claims (3)

[Claims] (1) A characteristic thermistor characterized in that electrodes are formed on both end faces of a negative characteristic thermistor element having a rectangular parallelepiped shape with a gap separated from the outer periphery of the element. (2) a step of depositing a metal layer on the front and back surfaces of a plate-shaped thermistor body, and a step of partially removing the metal layer to form a grid-like gap in the vertical and horizontal directions; A method for manufacturing a thermistor, comprising the step of cutting the thermistor element along the gap portion. (3) The step of partially removing the metal layer to form a grid-like cap portion in the vertical and horizontal directions is a photo-etching step, as set forth in claim 2. A method of manufacturing a thermistor.