JPS63222401A - Manufacture of chip type positive characteristic 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 chip-shaped positive temperature coefficient thermistor.

<Prior Art> Conventionally, a square chip-shaped positive temperature coefficient thermistor has a square chip-shaped positive temperature coefficient thermistor, as shown in the cross-sectional view of FIG. One contact electrode 2° made of ohmic material that does not contain silver such as nickel,
2o is formed, and surface electrodes 3° and 3o are formed from above each contact electrode 2°+20 using silver paste to cover both ends of the element body 1°, and on the one main surface side of the element body 1°. is the opposite edge of the surface electrodes 3° and 3o, or the contact electrode 2
゜, 2o are set back toward the end side from the opposing edges.

In manufacturing this conventional chip-type positive temperature coefficient thermistor, a plate-like cable continuum in which a large number of element elements 1°, . . . After forming contact electrodes 2°, .

By dividing it into ..., a 1° element body having contact electrodes 2°, 2° on one main surface of both ends is obtained, and after that, for each 1° element, on both ends thereof, A method of forming surface electrodes 3° and 3o, respectively, is adopted.

<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 with respect to .

That is, the contact electrode 2° is located on 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 2° is small, if solder cracks occur on the surface electrode 3° when soldering 5° to a circuit board 4°, etc., the contact electrode 2° 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 the charges are concentrated on the opposite edges of the 'surface electrodes 3°, 3
However, on the other main surface (lower surface in the figure) of the element body 1°, there is no contact electrode inside the surface electrode 3°, and the surface electrodes 3° and 3o directly oppose each other. Therefore, migration is likely to occur between these opposing edges.

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

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 when soldered, and is easy to handle during mounting. purpose.

<Means for Solving the Problems> In order to achieve the above object, the present invention has a structure in which a large number of prismatic chip-like element bodies corresponding to a single chip-type positive temperature coefficient thermistor are connected to each other in the width direction. a step of preparing a body continuum; a step of forming a plating resist film along the longitudinal direction of the body continuum at locations corresponding to unnecessary electrode parts on both main surfaces of each element; A step of plating the element continuum with an ohmic material that does not contain silver to obtain an element continuum in which both main surfaces and end surfaces of the ends of each element are covered with a plating film that serves as a contact electrode. And, in the element continuum having the plating film, the element has entered both ends of the element continuum that are continuous with each other, or both ends of the element element divided from this element continuum, toward the end surface side than the contact electrode. We decided to manufacture a chip-type positive temperature coefficient thermistor by forming a surface electrode using a material containing silver as a main component.

According to the above manufacturing method, the contact electrode and the surface electrode cover both main surfaces and end faces of the element body in the form of a square chip, and the contact electrodes cover both main surfaces and end faces of the element body in the form of a square chip. A chip-type static thermistor is obtained in which the opposing edges of the surface 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 on both main surfaces of the element body are concentrated on opposing edges of the contact electrodes, and no migration occurs on either main surface. In addition, since the contact electrode has a large area, even if some 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 there is no possibility of a connection failure. does not occur. Further, 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.

Moreover, contact electrodes are formed on a large number of 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 both perspective views of a square 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. 1 is obtained by the first embodiment of the manufacturing method of the present invention, which will be described later. and a pair of surface electrodes 3.3.

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 has a U-shape in side view with both main surfaces (top and bottom surfaces in the figure) of the end of the element body (upper and lower surfaces in the figure). covered. Therefore, this contact electrode 2 has two main surface covering parts 2
a, 2a, and an end face covering part 2b. The surface electrode 3 is mainly composed of silver, and covers both main surfaces and ends of the element I from above the contact electrode 2 at both ends of the element I in a U-shape when viewed from the side. There is. Therefore, this surface electrode 3 also has two main surface covering portions 3a.

3a, and an end face covering part 3b. Then, on each main surface of the element body, the main surface covering portion 3 a of the surface electrode 3.3
, 3a are set back toward the end of the element body 1 by a predetermined dimension S than the opposing edges between the main surface covering portions 2a, 2a of the contact electrode 2.2.

The chip-type positive temperature coefficient thermistor shown in FIG. 2 is obtained by the second embodiment of the manufacturing method of the present invention.
covers the entire edge. Therefore, this surface electrode 3
consists of two main surface covering parts 3a, 3a, an end face covering part 3b, and two side face covering parts 3c, 3c. On each main surface of the element body 1, the opposing edges of the main surface covering portions 3a, 3a of the surface electrode 3.3 have a predetermined dimension larger than the opposing edges of the main surface covering portions 2a, 2a of the contact electrode 2.2. The point where S is retreated toward the end of the element L is the first point.
It is similar to the thermistor shown in the figure. The configuration of other parts is also the same as that in FIG. 1, so corresponding parts are given the same reference numerals and detailed explanations will be omitted.

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

FIGS. 3A to 3F are explanatory diagrams of the manufacturing process of the chip type positive temperature coefficient thermistor shown in FIG. 1, according to the first embodiment of the present invention. 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 IO has a short surface shape, and a large number of rectangular chip-shaped element elements l corresponding to the chip-type positive temperature coefficient thermistor elements are mutually arranged in the width direction of the element element 1 (as shown in FIGS. 1 and 2). It is continuous in the direction of arrow A).

Therefore, in this elemental continuum 10, each elemental element l
is continuous to another elemental element l on the side.

■Second step; As shown in FIG. 3(B), a plating resist solution is applied by screen printing along the longitudinal direction of the continuous element body 10 at the center of both main surfaces of the continuous element body 10. Thereafter, it is dried, and a plating resist film 4 having a predetermined width and continuous in the longitudinal direction of the continuous element body 10 is formed on both main surfaces of the continuous element body 10.

The portion where the plating resist film 4 is formed corresponds to the portion where the contact electrode 2 is not formed on both main surfaces of each element unit l.

■Third step: As shown in FIG. 3(C), electroless plating with an ohmic material such as nickel that does not contain silver is applied to the element continuum 10 on which the plating resist film 4 has been formed at the required locations. . As a result, plating films 20, which will become contact electrodes 2, are continuously formed on both edges along the longitudinal direction of the element continuum lO. In this element continuum lO, both main surfaces and end faces of the ends of each element element l are covered with contact electrodes 2.

■Fourth step: The plating resist @4 is removed from the element body continuum 10 subjected to electroless plating. This removal is performed by applying ultrasonic waves to the plating resist film 4 in a solvent. As a result, as shown in FIG. 3(D), the element continuum 10
A continuous element body lO is obtained in which the plating film 20, which will become the contact electrode 2, remains at both edges, that is, at locations corresponding to both main surfaces and end faces of the end portions of each element element l.

■Fifth step; Next, as shown in FIG.
0L, and apply 30L of silver paste on the surface of the plating film 2.
Attach. Here, the liquid depth U of the silver paste 30L is set to be smaller than the formation width V of the plating film 2 by a predetermined dimension S.

By drying and firing the adhered silver paste 30L, as shown in FIG. A membrane 30 is formed.

Each element l of this element continuum IO protrudes by a predetermined dimension S from either the contact electrode 2 or the surface electrode 3 on both main surfaces.

■Sixth step: An element continuum l on which the plating film 20 and the conductive film 30 are formed
O at the position corresponding to the side surface of each elemental unit l (Fig. 3 (F
) at position t). As a result, as shown in FIG. 1, a U-shaped contact electrode 2 and a surface electrode 3 are formed at both ends of the element body l, and the contact electrode 2 is smaller than the surface electrode 3 on both main surfaces by a predetermined dimension. A chip-type positive temperature coefficient thermistor in which only S is protruded can be obtained.

FIG. 4 (A XB ) is an explanatory diagram showing a part of the manufacturing process of the chip type positive temperature coefficient thermistor shown in FIG. 2, according to the second embodiment of the present invention.

Among the steps of this thermistor manufacturing method, the steps up to forming the plating film 20 that becomes the contact electrode 2 on the element continuum lO are the same as the steps shown in FIG.
The process after forming 0 is different from the process shown in FIG.

That is, the manufacturing method of this second embodiment, as in the first embodiment, includes: (1) a first step of preparing an element continuum IO in which a large number of element elements L are continuous in the width direction; A second step of forming a plating resist film 4 on the continuum lO; ■ A third step of applying electroless plating to the element continuum 10 having the plating resist film 4; ■ A continuum of element bodies subjected to electroless plating. 10
After the fourth step of removing the plating resist film 4 from the substrate, the next fifth step and sixth step are performed.

■Fifth step: The element continuum IO having the plating film 20 is prepared as shown in FIG. 4(A).
As shown in the figure, each element unit 1 is divided at a position corresponding to the side surface (position of symbol t) to obtain an element unit 1 in which contact electrodes 2 are formed on both main surfaces and end faces of each end. .

■Sixth step: Next, as shown in FIG. 4(B), each end of the element unit l having the contact electrode 2 is immersed in the silver paste 30L of a certain depth, and the contact type 4fi2 30L of silver paste was applied to the surface of the plate. Here, the liquid depth U of the silver paste 30L is
It 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 30L, surface electrodes 3 are formed on the entire surface of both ends of the element unit 1 in a state that substantially covers the contact electrodes 2. On both main surfaces of this single element 1, the contact electrode 2 protrudes from the surface electrode 3 by a predetermined distance S.

In this way, as shown in FIG. 2, the contact electrode 2 and the surface electrode 3 are formed at both ends of the element body l, and the contact electrode 2 is closer to the surface electrode 3 on both main surfaces of the element body l. A prominent chip type positive temperature coefficient thermistor is obtained.

In the chip type positive temperature coefficient thermistor obtained by this second embodiment, the surface electrode 3 covers both sides of the element body l,
Although the surface electrodes 3.3 directly face each other on this side, there is no concern that migration will occur.

<Effects of the Invention> As described above, according to the present invention, a chip-shaped main body in which the opposing edges of the contact electrodes on both main surfaces of the square chip-shaped element body protrude more than the opposing edges of the surfaces ihi. A characteristic thermistor is obtained, and in this chip-type positive characteristic thermistor, migration does not occur on any of the main surfaces of the cable, and the occurrence of migration can be reliably prevented.

Incidentally, a migration comparison test (conditions: 30 samples each, temperature 40℃ When conducted in an atmosphere with 95% humidity, applied voltage of 3V, and test time of 3,000 hours,
In the conventional product, migration occurred in three pieces, but in the product of the present invention, no migration occurred.

In addition, in the chip-type positive temperature coefficient thermistor obtained by the method of the present invention, contact electrodes are formed on both main surfaces and the end face of the end of the element body, and compared to conventional chip-type positive temperature coefficient thermistors, the contact electrodes are Because the surface area is large, even if some 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 sufficiently ensured, 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 of the element, as well as the left and right sides, 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., making handling easier. becomes easier.

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.

Furthermore, since the spacing between contact electrodes is determined by the width of the plating resist and film formed by screen printing,
The interval can be set with high precision, and therefore a thermistor with stable characteristics can be obtained.

[Brief explanation of drawings]

1 to 4 relate to the present invention, and FIGS.
Each figure is a perspective view of a chip-type positive temperature coefficient thermistor obtained by the method of the present invention, FIG. 3 is an explanatory diagram showing each step of the first embodiment of the present invention, and FIG. It is an explanatory diagram showing a part of each process. FIG. 5 is a sectional view of a conventional chip type positive temperature coefficient thermistor.゛■...Elementary body (single element), IO...Elementary body continuum, 2...
・Contact electrode, 20... Plating film, 3... Surface electrode,
30... Conductive film, 4... Plating resist film.

Claims (1)

[Claims] (1) A step of preparing an element continuum in which a large number of square chip-shaped element bodies corresponding to a single chip-type positive temperature coefficient thermistor are continuous in the width direction; A process of forming a plating resist film on the parts corresponding to unnecessary electrodes on both main surfaces of each element, and plating the continuous element body having the plating resist film with an ohmic material that does not contain silver. A step of obtaining a continuous element body in which both main surfaces and end faces of the end portion of the single body are covered with a plating film serving as a contact electrode, and both ends of the single element body continuous with each other in the continuous element body having the plating film. or a step of forming surface electrodes of a material containing silver as a main component on both ends of a single element divided from this element continuum in a state of recess toward the end face side than the contact electrode. A method for manufacturing a chip-type positive temperature coefficient thermistor, characterized in that: