JP2000021602A - Chip resistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily distinction the upper or lower face of a resistor, and determinate whether a resistor exists or not in bulkily mounting by providing the resistor on a ceramic substrate with a body color which is formed by mixing ceramic raw material powder with a coloring pigment and firing it. SOLUTION: A ceramic substrate 1 is provided by mixing ceramic raw material powder with a coloring pigment and firing it. In general, the substrate is preferably an alumina substrate using alumina raw material powder, for example Al2O3 powder, at 94 to 96% of purity. Inorganic pigment of a metal oxide capable of hanging a ground color of the ceramic is used as the coloring pigment. A resistor layer 3 is provided on the ceramic substrate 1, a pair of electrodes are provided on both ends of the substrate 1 and an intermediate electrode 4 and an outer electrode 5 are formed on the surface of the electrodes 2 by a plating method. A protective layer 6 is also formed on the surface of the resistor layer 3. Thereby, distinction between the upper end the lower faces of the resistor, and determination whether the resistor exists or not in mounting it can be facilitated without increasing the production cost including part and mounting costs.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip type resistor mounted on a printed circuit board on which a wiring circuit is formed by a bulk mounting method.

[0002]

2. Description of the Related Art An extremely large number of resistors are used in electronic equipment, and as the electronic equipment itself is reduced in size and weight, resistors are also reduced in size and made into a chip type.

As shown in FIG. 1, such a chip resistor is formed by applying a conductive paste such as a silver-palladium paste to both ends of a ceramic substrate 1 made of alumina.
A pair of electrode terminals 2 formed by baking is arranged, a resistance paste such as ruthenium oxide is printed between the pair of electrode terminals 2 on the surface of the ceramic substrate 1, and the resistance layer 3 formed by baking is formed. (Usually black). An intermediate electrode 4 made of a nickel plating film or the like and an external electrode 5 made of a solder plating film or the like are formed on the surface of the electrode terminal 2, and a protective layer 6 is formed on the surface of the resistance layer 3.

When a chip type resistor as shown in FIG. 1 is mounted on a printed circuit board of an electronic device, the chip type resistor is provided in an embossed container (part supply container for a chip mounter) having a recess for accommodating the resistor. A device in which a container is housed and wound on a reel, or a device in which a chip type resistor is housed in a tape carrier and wound on a reel, is mounted by a chip mounting device. Here, when the chip type resistor is stored in the embossed container or when stored in the tape carrier, the color of the back surface of the ceramic substrate and the color of the resistance layer are different.
The front and back of the chip type resistor are completely distinguished and stored.

[0005] Further, while it is always required to reduce the manufacturing cost of electronic components, in the case of a chip type resistor as shown in FIG. 1, not only the manufacturing cost of itself but also the mounting cost is strongly required to be reduced. Have been.

Therefore, in order to reduce the mounting cost, it is possible to reduce the frequency of replenishing components, reduce the time required for replenishing components, and reduce inventory space from a mounting type using an embossed container or a tape carrier. Bulk mounting formats that do not require high additional equipment costs are being attempted. In the bulk mounting type, a large number of chip-type resistors are collectively stored in a box-shaped bulk case without using the above-described reels or the like that store individual components.

However, in bulk mounting, chip resistors are stored in a bulk case in a bulk without being distinguished from the front and back, so that the chip resistors are necessarily distinguished between front and back. Mounted on a printed circuit board.

For this reason, as shown in FIGS. 2A and 2B, the periphery (FIG. 2A) of a region 21 on which a chip type resistor is mounted on a printed board 20 or both ends (FIG. 2A). FIG.
(B)), the symbol mark (S) is printed in advance with a white paint, and after the chip resistor is mounted, the black color of the resistance layer or the overcoat glass layer of the chip resistor and the white color of the symbol mark are set. By detecting the difference in contrast, the edge of the chip-type resistor is determined, and it is determined whether or not the displacement of the mounting position is within an allowable range (that is, whether or not the mounting is actually performed correctly). Then, a repair operation is performed as needed.

In the manufacturing process of the chip-type resistor, a ceramic substrate for a chip-type resistor having a predetermined size (for example, 40 × 50 mm) is collectively formed in a predetermined shape (for example, 1.6 × 0.8 mm). After the chip-type resistors are formed, each chip-type resistor is obtained by separating it into individual parts by using a pre-formed dividing groove.

In order to reliably detect the surface on which the dividing groove is formed, it is necessary to have a clear contrast between the color of the resistor (black) and the body color (body color). Blue-green colors are desired.

[0011]

On the other hand, the back surface of the chip resistor (see FIG. 1) has the color of the material itself because the ceramic substrate 1 is exposed. Since the ordinary ceramic substrate 1 is made of alumina, the color of the back surface of the chip resistor is usually white.

For this reason, when the color of the back surface of the chip resistor is white, the printed circuit board 2 shown in FIGS.
The difference in color tone and contrast between the white symbol mark (S) on 0 is not sufficient, and depending on the case, the chip resistor is mounted upside down and the chip resistor itself is mounted. There is a problem that it cannot be sufficiently distinguished from the case where it is not performed.

In order to solve such a problem, it is conceivable to provide an expensive front and back detection mechanism and an alignment mechanism in a bulk case or a mounter, but it is possible to avoid an increase in the overall manufacturing cost including the mounting cost of the chip type resistor. Absent.

It is also conceivable to apply colored ink to the back surface of the chip-type resistor, but this leads to an increase in the number of manufacturing steps (coating → drying → inspection) and avoids an increase in the manufacturing cost of the chip-type resistor. Absent.

Further, a symbol mark (S) is printed on the printed board.
However, it is not an effective method in consideration of improvement of mounting accuracy and quality, repair (service) after mounting, and the like. In addition, it is conceivable to change the color of the symbol mark.However, in recent years, when inspection machines for discriminating the front and back of chip type resistors have become quite widespread, it is necessary to change the inspection machine. It is not easy to realize this because it is assumed.

An object of the present invention is to solve the above-mentioned problems of the prior art. When a chip-type resistor is mounted in bulk, the case where the chip-type resistor is mounted upside down is different from the case where the chip-type resistor is mounted upside down. The chip resistor has a configuration that enables easy realization of the distinction from the case where the type resistor itself is not mounted and the inspection of the mounting accuracy without increasing the overall manufacturing cost including the component cost and the mounting cost. The purpose is to grant.

[0017]

Means for Solving the Problems The present inventors used a ceramic substrate prepared by mixing a ceramic raw material powder with a coloring pigment and firing the same, whereby the manufacturing process of the chip type resistor can be improved. The inventors have found that the above object can be achieved without increasing the manufacturing cost, and have completed the present invention.

That is, according to the present invention, in a chip type resistor having a resistance layer on a ceramic substrate, the ceramic substrate is produced by mixing a ceramic raw material powder and a coloring pigment and firing the mixture, and the body color itself is obtained. It is intended to provide a chip-type resistor characterized by having.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The chip type resistor according to the present invention has a resistance layer 3 on a ceramic substrate 1 as shown in FIG. Further, a pair of electrode terminals 2 are provided at both ends of the ceramic substrate 1.
And an intermediate electrode 4 and an external electrode 5 are formed on the surface of the electrode terminal 2 by plating.
Is provided with a protective layer 6 on the surface thereof.

The chip type resistor of the present invention is characterized in that a ceramic substrate 1 is prepared by mixing ceramic raw material powder and a coloring pigment and firing the mixture. Such a ceramic substrate 1 has a body color and is manufactured at low cost, and the back surface is also a surface colored with a coloring pigment without performing a special coloring step such as applying ink. Therefore, it can be easily distinguished from the white symbol mark formed on the printed board for indicating the position where the chip type resistor is mounted. It is easy to distinguish the case where the device is mounted upside down and the case where the chip type resistor itself is not mounted, and to shift the position without increasing the overall manufacturing cost including the component cost and the mounting cost. Can be detected.

In the present invention, the thickness of the ceramic substrate 1 can be determined according to the purpose of use of the chip type resistor and the like.

As the ceramic substrate 1, an alumina substrate is generally preferable, and it is preferable to use an alumina raw material powder (for example, Al ₂ O ₃ powder) having a purity of 94 to 96%.

As the coloring pigment, it is preferable to use an inorganic pigment such as a metal oxide which can change the ground color of the ceramic substrate 1. For example, as an inorganic pigment,
Cr ₂ O ₃ (green), CoO.nAl ₂ O ₃ (green), CoO.nSnO.mMgO (blue), CoO.
nZnO (green), CuO.Cr ₂ O ₃ (green), CuO
• Fe ₂ O ₃ .Mn ₂ O ₃ (green) or the like can be preferably used. Here, the color described in parentheses is a color shown as an example because it changes depending on the firing temperature.

The amount of the coloring pigment used depends on the ceramic substrate 1
Material, symbol mark paint type, expected color tone,
It can be appropriately determined within a range of several percent or less depending on the color density and the like.

As a method for producing the ceramic substrate 1, a ceramic raw material powder and a coloring pigment may be mixed and fired by a conventional method, and the mixing conditions, firing conditions, and the like can be appropriately selected.

The components other than the ceramic substrate 1 of the chip resistor of the present invention can have the same configuration as the conventional chip resistor.

For example, the resistance layer 3 may have the same configuration as that of a known chip type resistor, and may be formed by screen-printing and firing a resistance paste such as a ruthenium oxide paste or the like. , Cr, Ni, Ni
-Vacuum deposited thin film of metal or alloy such as Cr (Nichrome),
Preferable examples include a sputtering thin film.

As the pair of electrode terminals 2 at both ends of the ceramic substrate 1, those formed by applying a conductive paste such as a silver palladium paste and baking it can be preferably used. The thickness of the electrode terminal 2 can be appropriately selected.

An intermediate electrode 4 formed on the surface of the electrode terminal 2
Preferably, a nickel plating film can be used, and as the external electrode 5, a solder (lead-tin alloy) plating film can be preferably used. The thickness of the intermediate electrode 4 and the external electrode 5 can also be appropriately selected.

The protective layer 6 of the resistance layer 3 is preferably made of a low soda-containing glass (borosilicate glass (B ₂ O ₃ .Si
O ₂ ) and the like. The layer thickness can also be appropriately selected.

In the case where the resistance layer 3 made of a metal film or the like has good stability, the formation of the protective layer 6 can be omitted.

The chip resistor of the present invention can be manufactured as follows. First, a ceramic substrate is prepared by mixing a ceramic raw material powder and a color pigment and firing the mixture. Next, a conductive paste is applied to both ends of the ceramic substrate and baked to form a pair of electrode terminals. Next, a resistive paste is printed between the pair of electrode terminals on the surface of the ceramic substrate and baked to form a resistive layer. Then, after forming the protective layer on the surface of the resistance layer, it can be manufactured by forming an intermediate electrode and an external electrode on the surface of the electrode terminal by plating.

The above-described chip-type resistor of the present invention comprises:
Other mounting formats can be accommodated, but are particularly suitable for bulk mounting.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to embodiments.

Example 1 Alumina powder raw material (purity 94-96% Al ₂ O ₃ ) 100
The color pigment (Cr ₂
A small amount (1 to 3 parts by weight) of O ₃ ) was added, and a binder (eg, water-soluble cellulose such as methyl cellulose) and water were further added as vehicles. The kneaded material was molded into a plate to form a green sheet, which was baked at 1600 ° C. for about 1 hour. Thus, a ceramic substrate having a desired body color was obtained.

A silver palladium paste was applied to both ends of the obtained ceramic substrate, and baked to form electrode terminals.

A layer film resistor paste (ruthenium oxide: Ru ₂ O ₃ ) was screen-printed on the ceramic substrate and baked at 850 ° C. for about 1 hour to form a resistor layer.

Next, the resistance layer was adjusted to a predetermined resistance value by a laser trimming method. Then, a borosilicate glass frit was screen-printed as a protective film on the resistance layer, and baked to form a metal glaze.

Next, in order to provide the electrode terminals with good solderability, plating adhesion, and electrochemical and chemical stability (migration prevention, whisker prevention), a nickel film as a base plating layer and a solder A (tin-lead (9: 1)) plating layer was formed on the surface. This allows
A chip resistor having the structure shown in FIG. 1 was obtained.

Example 2 A chip-type resistor was manufactured in the same manner as in Example 1, except that a vacuum deposited Ni—Cr film was formed as a resistance layer on the same ceramic substrate as in Example 1.

(Evaluation) The obtained chip-type resistors of Examples 1 and 2 were stored in a bulk cassette, and a white symbol mark indicating the mounting position was printed using a general bulk mounting apparatus. Mounted on a printed circuit board.

After the bulk mounting, the mounting surface was inspected with a general mounting inspection device for chip type resistors. As a result, the discrimination between the front and back and the mounting position of the chip type resistors could be performed with a 100% probability. .

[0044]

According to the chip-type resistor of the present invention, in bulk mounting, it is distinguished whether the chip-type resistor is mounted upside down or the chip-type resistor itself is not mounted. Can be easily performed without increasing manufacturing costs including component costs and mounting costs.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a chip resistor.

FIG. 2 is an explanatory view of a symbol mark formed on a printed board (FIGS. 2A and 2B).

[Explanation of symbols]

1 ceramic substrate, 2 electrode terminals, 3 resistive layers, 4
Intermediate electrode, 5 external electrode, 6 protective layer

Claims (2)

[Claims] 1. A chip-type resistor having a resistance layer on a ceramic substrate, characterized in that the ceramic substrate is produced by mixing a ceramic raw material powder and a coloring pigment and firing it, and has a body color itself. And chip type resistor. 2. The chip type resistor according to claim 1, wherein the ceramics substrate is an alumina substrate.