Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1999-02-05
2001-11-13
Young, Lee (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S610100, C029S621000, C338S309000, C338S308000, C338S332000
Reexamination Certificate
active
06314637
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The invention relates to a chip resistor which is widely used in an electronic circuit, particularly to a chip resistor which has a low resistance and a low TCR, and also to a method of producing the resistor.
2. Background Art
Recently, as typically exemplified by a portable telephone, a movie camera, and a notebook-type personal computer, demands for small electronic apparatuses are growing. It is no exaggeration that miniaturization and improvement of the performance of such electronic apparatuses will depend on those of chip-type electronic parts to be used in the apparatuses. As a thin film resistor body, known are ruthenium oxide and a composition which contains bismuth ruthenate and lead ruthenate that are complex oxides of ruthenium oxide, as main components (for example, see the Unexamined Japanese Patent Application Publication No. Sho 58-37963). Such a resistor body is used in various fields.
An example of a method of producing a conventional chip resistor will be described with reference to the accompanying drawings.
FIG. 12
is a perspective view showing an example of the structure of a conventional chip resistor, and
FIG. 13
is a section view taken along the line A-A′ of FIG.
12
. Usually, a chip resistor of this kind is produced in the following manner. First, upper electrodes
11
are formed on the upper face of a chip-like alumina substrate
10
which is made of alumina of 96% purity. A resistor body
12
is formed on a part of the upper face of the alumina substrate
10
so as to be connected with the upper electrodes. A protective film
14
which is made of lead borosilicate glass is formed so as to cover the whole of the resistor body
12
. Usually, the protective film 14 is formed by forming a pat-tern by means of screen printing and then firing the film at a temperature as high as 500 to 800° C.
Next, end-face electrodes
13
each consisting of an Ag thick film are formed on the end faces of the alumina substrate
10
so as to be connected with the upper electrodes
11
, respectively. Usually, the end-face electrodes
13
are formed by conducting a firing process at a high temperature of about 600° C. In order to ensure the reliability in a soldering process, finally, Ni plated films
15
are formed by electroplating so as to cover the end-face electrodes
13
, and solder plated films
16
are formed so as to cover the Ni plated films
15
, thereby completing a chip resistor.
In a chip resistor produced by such a production method, generally, a thick film glaze resistor body material which contains ruthenium oxide as a main component is used as conductive particles constituting the resistor body. However, a resistor body material which contains only ruthenium oxide has a large temperature coefficient of resistance (hereinafter, often abbreviated as “TCR”) which indicates a change of the resistance with temperature. Therefore, the material must be used after the TCR is reduced to a small value of about ±50 ppm/° C. or less by adding a TCR adjustment material such as a metal oxide.
When such a resistor body material is used, however, it is difficult to produce a chip resistor having a low resistance of 1 &OHgr; or less because ruthenium oxide has high resistivity. To comply with this, a chip resistor has been proposed in which a copper nickel alloy having a low temperature coefficient of resistance, such as that described in JIS C2521 and JIS C2532 is used as a resistor body material of a low resistance of 1 &OHgr; or lower.
Specifically, a structure is proposed in which such an alloy material is formed into a foil-like or plate-like shape and then applied to an alumina substrate, and that in which resistor body paste obtained by kneading copper powder, nickel powder, and a glass frit in an organic vehicle is printed on an alumina substrate and then fired in an inert atmosphere, thereby forming an alloy film (see the Unexamined Japanese Patent Application Publication Nos. Hei 2-308501 and Hei 3-270104).
In the former structure, however, the mass productivity is not highly excellent because of the following reason. Under the situation where miniaturization of a chip part is growing, a method of working alloy foil or an alloy plate has a limit, a trimming process cannot use a laser, and other processes such as grinding have a limit. Furthermore, also from the view point of cost, the method is more disadvantageous than the printing method.
In the latter structure, the bonding between the resistor body film and the substrate, and the adjustment of the resistance layer are realized by using glass, and hence components other than copper-nickel are contained at high ratios. Consequently, the temperature coefficient is different from that of a copper nickel alloy. Depending on the firing conditions, furthermore, the glass component exhibits diffusion behavior in the metal components and at the interface between sintered particles in different manners. Therefore, the latter structure has a problem in that a stable resistance property is hardly obtained.
In the paste method using copper powder and nickel powder, the properties of a resistor are largely affected by the properties of terminal electrodes of a power supply portion, and the structure of the interface between the resistor body and an electrode. The minimum resistance which can be produced by the method is limited to 100 m&OHgr;. It is difficult to realize a lower resistance.
As described above, the recent tendency to miniaturization of a chip resistor is growing. On the other hand, the needs for a chip resistor which may be used in current detection in an electronic circuit, and the like and which has a low resistance and a low TCR is increasing. From the view point of the performance required in a use, moreover, a chip resistor which can ensure high accuracy and high reliability in addition to a low resistivity and a low TCR is eagerly requested.
SUMMARY OF THE INVENTION
The invention has been conducted in order to solve the above-discussed problems and satisfy the requirements. It is an object of the invention to provide a chip resistor which has a low resistance of 1 &OHgr; or less, particularly 100 m&OHgr; or less and a low TCR, and which is highly reliable.
DISCLOSURE OF INVENTION
The chip resistor of the invention comprises: an insulating substrate; a resistance layer which is formed on at least one face of the insulating substrate and which is made of a copper nickel alloy; a pair of upper-face electrode layers which respectively make surface contact with upper faces of both end portions of the resistance layer; and a pair of end-face electrodes which are formed on both end portions of the insulating substrate so as to cover at least parts of the upper-face electrode layers, respectively. Particularly, the bonding between the resistance layer and the upper-face electrode layers is realized by metal-to-metal bonding, and hence impurities which may affect the properties do not exist in the interface. As a result, a chip resistor which has a low resistance and a low TCR and which is excellent in heat resistance can be obtained.
REFERENCES:
patent: 3167451 (1965-01-01), Tierman
patent: 4437140 (1984-03-01), Ohyama et al.
patent: 4684916 (1987-08-01), Ozawa
patent: 5510594 (1996-04-01), Mori
patent: 5680092 (1997-10-01), Yamada et al.
Patent Abstracts of Japan, vol. 013, No. 207 (E-750), May 16, 1989 & JP 01 024401 A (Murata Mfg Co Ltd), Jan. 26, 1989, *abstract*.
Patent Abstracts of Japan, vol. 013, No. 410 (E-819), Sep. 11, 1989 & JP 01 151205 A (Matsushita Electric Ind Co Ltd), Jun. 14, 1989, *abstract*.
Patent Abstracts of Japan, vol. 016, No. 174 (E-1195), Apr. 27, 1992 & JP 04 018701 A (Murata Mfg Co Ltd), Jan. 22, 1992, *abstract*.
Patent Abstracts of Japan, vol. 097, No. 001, Jan. 31, 1997 & JP 08 236325 A (Hokuriku Electric Ind Co Ltd), Sep. 13, 1996 *abstract*.
Patent Abstracts of Japan, vol. 007, No. 251 (E-209), Nov. 8, 1983 & JP 58 138071 A (Matsushita Denki Sangyo KK), Aug. 16, 1983, *abstract*.
Kimura Suzushi
Nakao Keiichi
Shimoyama Koji
Yoneda Naotugu
Matsushita Electric - Industrial Co., Ltd.
Pearne & Gordon LLP
Smith Sean
Young Lee
LandOfFree
Method of producing a chip resistor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of producing a chip resistor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of producing a chip resistor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2601479