JPS63213313A - Manufacture of chip positive characteristics thermistor - 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 <Industrial Application Field> The present invention relates to a method for manufacturing a square or round chip type positive temperature coefficient thermistor.

<Prior Art> Conventionally, a chip-type positive temperature coefficient thermistor, for example, a square chip-shaped positive temperature coefficient thermistor, has a square chip-shaped element body l, as shown in the cross-sectional view of FIG. One major surface of both ends of (
Contact electrodes 2° and 2o are formed using ohmic material that does not contain silver, such as nickel, on the top surface (in the figure), respectively, and silver paste is applied to the surfaces of both ends of the element body 1° from above each contact electrode 2° and 2o. Surface electrodes 3° and 3o are formed to cover the entire body, and on the one main surface side of the element body 1°,
Opposite edges of surface electrodes 3° and 3o are contact electrodes 2° and 2
o It is set back toward the end from the opposite edge of the dowel.

In manufacturing this conventional chip-type positive temperature coefficient thermistor, a plate-shaped element continuum in which a large number of element elements 1°, . . . A single element l on one main surface.

After forming contact electrodes 2°, .

... and a contact electrode 2 on the main surface of one of both ends.
o, an elemental simplex l with 2°. After that, a method is adopted in which surface electrodes of 3° and 3° are formed at both ends of each element every 1°.

<Problem that the invention seeks to solve> According to the above manufacturing method, a large number of single element bodies with an angle of 1°.

Since the contact electrodes 2°, . . . are formed all at once for .

That is, the contact electrode 2° covers one of each surface of the 1° end of the element body.
, since it is formed only on one main surface and the area of the contact electrode 2o is small, if solder cracks occur on the surface electrode 3° when soldering 5° to a circuit board 4°, etc., the contact electrode 2o and The electrical connection between the circuit board 4° and the land 6° may become defective, resulting in poor reliability.

To solve this problem, the thickness of the surface electrode 3° may be made sufficiently thick, but in that case, the amount of expensive electrode material used increases, leading to an increase in cost.

In addition, on one main surface (upper surface in the figure) of the element body 1°, a contact electrode 2 protrudes beyond the surface electrode 3°.
Since charges are concentrated on the opposite edges of the surface electrodes 3° and 3o
However, on the other main surface (lower surface in the figure) side of the element body 1°, the surface electrode 3
Since there is no contact electrode on the inside of the surface electrodes 3° and 3o, and the surface electrodes 3° and 3o directly oppose each other, migration is likely to occur between these opposing edges.

Furthermore, in the conventional dip-type positive temperature coefficient thermistor, the main surface side where the contact electrode 2° is located is the main heat generation site, so in order to obtain the desired characteristics, when mounting it on a circuit board 4°, etc. It is difficult to handle as it is necessary to distinguish between the front and back sides.

One possible solution to this problem is to sequentially form a contact electrode and a surface electrode for each element so that the shape of the contact electrode and surface electrode is shaped so that connection failures and migration do not occur. Efficiency decreases.

In view of the above-mentioned problems, it is an object of the present invention to provide a method for efficiently manufacturing a chip-type positive temperature coefficient thermistor that does not cause poor connection or migration during soldering, and is easy to handle during mounting. purpose.

<Means for Solving the Problems> In order to achieve the above-mentioned object, the present invention provides a method in which a large number of elemental elements corresponding to a single element of a chip-type positive temperature coefficient thermistor are connected to other elemental elements at their end faces. A step of preparing an element continuum, a step of forming an ohmic contact electrode that does not contain silver at a location corresponding to the peripheral surface of each element in the element continuum, and a step of forming an ohmic contact electrode that does not contain silver. A step of dividing the element continuum into individual element units to obtain an element unit in which contact electrodes are formed on the peripheral surfaces of both ends; By forming a surface electrode with a material containing silver as a main component while retracting to the side,
We decided to manufacture a chip type positive temperature coefficient thermistor.

According to the above manufacturing method, anywhere around the element body,
A chip-type positive temperature coefficient thermistor is obtained in which the opposing edges of the contact electrodes protrude more than the opposing edges of the surface electrodes.

In this chip-type positive temperature coefficient thermistor, when a voltage is applied between both electrodes, charges are concentrated on the opposing edges of the contact electrodes anywhere around the element body, and migration occurs between the surface electrodes. do not. In addition, since the area of the contact electrode is large, even if solder cracks occur on the surface electrode when soldering to a circuit board, etc., the connection between the land of the circuit board and the contact electrode is ensured sufficiently, and connection failures are avoided. Does not occur.

Furthermore, the shapes of the contact electrode and the surface electrode are symmetrical with respect to the front and back sides and left and right sides of the element body, and the heat generating portions are symmetrical.

Therefore, contact electrodes can be formed on a large number of single element bodies at once, resulting in high production efficiency.

<Example> Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

1 and 2 are partially cutaway perspective views of a chip type positive temperature coefficient thermistor obtained by the manufacturing method of the present invention.

The chip-type positive temperature coefficient thermistor shown in FIG. Equipped with

The element body 1 is made of semiconductor ceramics such as barium titanate. The contact electrode 2 is made of an ohmic material that does not contain silver, such as nickel or aluminum, and covers four surrounding surfaces of the element body 1 (the top surface, the bottom surface, and both sides in the width direction in the figure). Therefore, this contact electrode 2 includes an upper surface covering portion 2a, a lower surface covering portion 2b, and a lower surface covering portion 2b.
It consists of two side surface covering parts 2c, 2c. The surface electrode 3 is mainly composed of silver, and covers the contact electrode 2 at both ends of the element body 1, the four peripheral surfaces of the element body 1, and the end faces of the element body 1. Therefore, this surface electrode 3
consists of an upper surface covering portion 3a, a lower surface covering portion 3b, two side surface covering portions 3c, 3c, and an end surface covering portion 3d. The opposing edges of the surface electrodes 3.3 are set back toward the end of the element body l by a predetermined dimension S than the opposing edges of the contact electrodes 2.2.

The chip type positive temperature coefficient thermistor shown in FIG. 2 is a round thermistor, and this thermistor has a cylindrical element body 4
, a pair of ohmic contact electrodes 5.5 that do not contain silver, such as nickel, and a pair of surface electrodes 6.6 that contain silver as a main component. The contact electrode 5 covers the circumferential surface of the element body 4.

The surface electrode 6 covers the peripheral surface of the element body 4 and the ends of the element body 4 from above the contact electrode 5 . Reference numeral 6a represents a peripheral surface covering portion of the surface electrode 6, and 6b represents an end surface covering portion of the surface electrode 6. The opposing edges of the surface electrodes 6.6 are set back toward the end of the element body 4 by a predetermined dimension S than the opposing edges of the contact electrodes 5.5.

Next, a method for manufacturing the chip-type positive temperature coefficient thermistor having the above structure will be explained step by step.

3A to 3E are explanatory diagrams of the manufacturing process of the square chip type positive temperature coefficient thermistor shown in FIG. 1. This thermistor manufacturing method includes the following steps.

(1) First step: First, as shown in FIG. 3(A), an element body continuum IO made of semiconductor ceramics is prepared. This element continuum lO is strip-shaped, and has a large number of element elements 1 corresponding to individual chip-type positive temperature coefficient thermistors connected to other element elements at their end faces.

■Second step: As shown in FIG. 3(B), among the various parts of the surface of the element body continuum 10, the parts corresponding to the parts where the contact electrode 2 is not formed in each element unit l, that is, each element body A mesh resist liquid is applied to the upper surface, lower surface, and both side surfaces of the central portion of the unit 1 and cured to form a mesh resist M7.

■Third step: The entire surface of the continuous element body 10 on which the metskiresist film 7 has been formed is electrolessly plated with an ohmic material such as nickel that does not contain silver.

■Fourth step: The metal resist film 7 is removed from the element body continuum IO whose entire surface has been electrolessly plated. This removal is performed by applying ultrasonic waves to the mesh resist film 7 in a solvent. As a result, as shown in FIG. 3(C), a nickel plating film 2, which will become the contact electrode 2, is formed on the peripheral surface of the end of the single element 1.
An elementary field continuum IO in which 0 remains is obtained.

■Fifth step: The continuous element body 10 in which the nickel plating film 20, which will become the contact electrode 2, remains is divided at a position corresponding to the end face of each element element l (position t in Fig. 3 (C)). As shown in Figure 3 (D), the peripheral surfaces of both ends (top surface, bottom surface and both side surfaces)
A single rod 1 is obtained, each having a contact electrode 2.2.

■Sixth step: Next, as shown in FIG. 3(E), each end of the element unit l having contact electrodes 2.2 at both ends is placed in silver paste 30 at a certain depth. The silver paste 30 is attached to the surface of the contact electrode 2 by immersion. Here, the liquid depth U of the silver paste 30 is set smaller than the formation width V of the contact electrode 2 by a predetermined dimension S. By drying and firing the adhered silver paste 30, surface electrodes 3 are formed at both ends of the element unit 1, substantially covering the contact electrodes 2. At each end of the element unit l, the contact electrode 2 is of the surface type W! , 3 by a predetermined dimension S.

As described above, the square thermistor shown in FIG. 1 is manufactured through the first to sixth steps.

FIGS. 4A to 4E are explanatory diagrams of the manufacturing process of the round depth type positive temperature coefficient thermistor shown in FIG. 2. As shown in this explanatory diagram, each manufacturing process of a round thermistor is similar to each manufacturing process of a square thermistor.

In other words, in the case of a round shape, the process is as follows: (1) As shown in FIG. A first step of brightening the round rod-shaped element continuum 40;
As shown in Figure (B), a second step of forming a plating resist film 7 on the parts of the surface of the element continuum 40 corresponding to the parts where the contact electrode 5 is not formed; A third step of applying electroless plating with an ohmic material not containing silver such as nickel to the entire surface of the element continuum 40 on which is formed; After removing the Metskirenst film 7,
As shown in FIG. 4(C), a fourth step of obtaining a continuous element body 40 in which a nickel plating film 50, which will become a contact electrode 5, remains on the circumferential surface of the end of the element body 4; By dividing the element body continuum 40 in which the nickel plating film 50 remains,
As shown in FIG. 4(D), contact electrodes 5 are attached to the circumferential surfaces of both ends.
．． The fifth step is to obtain a cable unit 4 having contact electrodes 5 and 5 at both ends. It consists of a sixth step of forming surface electrodes 6.6 on both ends of the element unit 4 in a state of substantially covering the contact electrode 5 by immersing it in the silver paste 60.

In addition, in each of the above embodiments, the element continuum 10.4
After forming a plated Renost film 7 on the element series 10.40, a plating film is formed on the entire surface of the element body continuum 10.40, and then, by removing the Metski Resist film 7, a plating film 7 is formed on the element body continuum 10.40 at required locations. Although the contact electrodes 2.5 are formed, in forming the contact electrodes 2, 5, for example, the ohmic material may be applied to the element body continuum 10.40 only at required locations; The process of forming the contact electrode 2.5 on the body 10.40 is not limited to that of the embodiments described above.

<Effects of the Invention> As described above, according to the present invention, it is possible to obtain a chip type positive temperature coefficient thermistor in which the opposing edges of the contact electrodes around the cable body protrude more than the opposing edges of the surface electrodes. In this chip-type positive temperature coefficient thermistor, migration does not occur anywhere around the element body, and migration can be reliably prevented from occurring.

In addition, since the chip-type positive temperature coefficient thermistor obtained by the method of the present invention has a larger contact electrode area than conventional chip-type positive temperature coefficient thermistors, it is difficult to solder the surface electrode when soldering to a circuit board, etc. Even if a crack occurs, the connection between the land of the circuit board and the contact electrode is sufficiently secured, and no connection failure occurs.

Furthermore, since the shapes of the contact electrodes and surface electrodes are symmetrical with respect to the front and back sides and left and right sides of the element, and the heat generating parts are also symmetrical, there is no need to consider the orientation of the front and back when mounting on a circuit board, etc. properties and easy handling.

Moreover, in the method of the present invention, since contact electrodes are formed on a large number of single element bodies at once, it is efficient and can be manufactured with the same efficiency as conventional chip-type thermistor manufacturing methods.

[Brief explanation of the drawing]

1 to 4 relate to the present invention, and FIGS.
Each figure is a partially cutaway perspective view of a chip type positive temperature coefficient thermistor obtained by the method of the present invention, and FIGS. 3 and 4 are explanatory views showing each step of the method of the present invention. FIG. 5 is a sectional view of a conventional chip type positive temperature coefficient thermistor. 1.4...Element body (single substance), 10.40...Element body continuum, 2.5...Contact electrode, 3,6...Surface electrode.

Claims (1)

[Claims] (1) A process of preparing an element continuum in which a large number of element elements corresponding to the element elements of a chip-type positive temperature coefficient thermistor are connected to other element elements at their end faces, and each element element in this element element continuum. A step of forming an ohmic contact electrode that does not contain silver at a location corresponding to the peripheral surface of the end, and a process of dividing the element continuum on which the contact electrode is formed into individual elements, and forming a contact electrode on the peripheral surface of both ends. A step of obtaining a single element having a contact electrode formed thereon, and forming a surface electrode at each end of the single element using a material containing silver as a main component in a state where the contact electrode is recessed toward the end face side. A method for manufacturing a chip-type positive temperature coefficient thermistor, comprising the steps of: