JP2006344777A - Chip resistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To give a resistance higher than before when the overall dimensions are identical. <P>SOLUTION: In the chip resistor where a filmlike resistor 2 is formed on the insulating surface of a substrate 1 and coated with a protective film 5 and an external electrode layer 6 is formed at the opposite ends of the substrate 1, the resistor film 2 is extended below the external electrode layer 6 while sandwiching an insulator film 4 between the resistor film 2 and the external electrode layer 6. Opposing face of the resistor film 2 and the external electrode layer 6 is lacking partially from the insulator film 4 and the lacking portion can serve as a portion for connecting the external electrode layer 6 and the resistor film 2 electrically (i. e. an internal electrode). The portion becoming the internal electrode may be not longer than one half of the short side of the substrate 1 where the external electrode layer 6 is formed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a chip resistor in which a resistor film is formed on an insulating surface of a substrate and external electrodes are provided on both ends of the substrate.

  FIG. 1 is an external view of a conventional general chip resistor, and FIG. 4 is a perspective view for explaining the internal structure in the order of manufacturing steps. The structure of the conventional chip resistor will be described with these. Such a chip resistor is also shown in Patent Document 1.

JP2002-208502

  First, conductive films called internal electrode layers 3 are formed on both ends of the insulating ceramic substrate 1, and the resistor film 2 is formed so as to partially overlap the internal electrode layers 3 ((A) in FIG. 4). . If necessary, the resistor film 2 may be formed with a fine line pattern by a technique such as photolithography, or the resistance value is adjusted by cutting with a laser or the like in a later step.

  For the purpose of protecting the resistor film 2, the resistor protective layer 4 using an insulator film may be formed. The resistor protective layer 4 is formed so as to cover most of the internal electrode layer 3 while covering the resistor film 2. Thereafter, the protective film 5 and the external electrode layer 6 are formed.

  In the structure of the conventional chip resistor, the internal electrode layer 3 occupies a large area, and the resistor film 2 can be disposed only in about 60% of the chip area. Further, the resistor film 2 is partially overlapped on the internal electrode layer 3, and because of the step formed at the overlapped portion, it is difficult to form a resist pattern having a width of 10 μm or less in the photolithography resist pattern forming step. It is difficult to form a fine line pattern of the film. For these reasons, when the external dimensions are the same, it is difficult to provide a high resistance value with the conventional chip resistor.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a chip resistor that can have a higher resistance value than before when the external dimensions are the same.

  According to the present invention, this object is to provide a chip resistor in which a film-like resistor is formed on the insulating surface of the substrate, the resistor film is covered with a protective film, and external electrode layers are formed on both ends of the substrate. The chip resistor is characterized in that the resistor film extends below the external electrode layer with an insulator film interposed between the resistor film and the external electrode layer.

  According to the configuration of the chip resistor of the present invention, the area in which the resistor film is disposed can be significantly increased as compared with the structure of the conventional chip resistor when the outer dimensions are the same, and the resistor film Since thin wire processing becomes easy, a large resistance value can be obtained with a limited chip area.

  In the insulator film, a part of the opposing surface of the resistor film and the external electrode layer is missing, and this lacking part can be a part where the external electrode layer and the resistor film are electrically connected (that is, the internal electrode). . The portion to be the internal electrode can be made to be half or less of the length of the short side on which the external electrode layer of the substrate is formed. In this case, the area of the resistor film is sufficiently increased, while the contact area between the external electrode layer and the internal electrode can be reduced, thereby reducing the influence of moisture entering through the solder and the external electrode on the resistor film. This improves the reliability of the chip resistor. In addition, it is possible to form a resistance pattern in the portion where the resistor film extends below the external electrode.

  In manufacturing the chip resistor of the present invention, a resistor film is first formed on the entire upper surface of an insulating substrate, and then a fine pattern is formed by photolithography to form a resistance pattern. In this way, there is no step in the entire region of the resistor film, and thin line processing by photolithography is easy. Thereafter, the internal electrode layer is formed on the resistor film with a necessary minimum area, the insulator film is formed on the resistor film, and the external electrode layer is formed on the insulator film. In this way, the resistor film can be disposed immediately below the external electrode layer, and the resistor film and thus the resistor pattern can be disposed on almost the entire surface of the substrate except for the internal electrode portion.

  An embodiment of the present invention will be described below with reference to FIGS. 2 is a perspective view showing the structure of one embodiment in the order of the manufacturing process, and FIGS. 3A, 3B, and 3C are taken along lines AA, BB, and CC in FIG. 1, respectively. It is sectional drawing. First, the resistor film 2 was formed on the entire upper surface of the ceramic substrate 1 by a vacuum film forming method ((A) in FIG. 2). The material of the resistor film was a nickel chromium alloy, and the thickness was 0.1 μm. Next, the resistor film 2 was etched using photolithography to form a thin line pattern (resistance pattern) having a width of 2 μm ((B) in FIG. 2).

  Since the resistor film 2 has no step over the entire surface, it is easy to perform fine processing using photolithography. However, when the desired resistance value is relatively low and fine processing is not required, the resistor film is formed by laser processing or by hand. You may process so that it may make a notch and may become desired resistance value. Next, the internal electrode layer 3 was formed on a part of the surface of the resistor film 2. The internal electrode layer 3 was formed by plating, and two layers of Ni and Au were laminated from the resistor film side. The internal electrode layer 3 is not more than half the length of the short side of the substrate 1 (about ¼).

  Next, using a photosensitive polyimide film, a resistor protective layer 4 as an insulator film was formed on a portion other than the internal electrode layer 3 on the upper surface of the substrate 1 ((C) in FIG. 2). Next, a protective film 5 was formed by covering a portion excluding a certain width along the short side of the substrate 1 using an epoxy resin ((D) of FIG. 2). Thereafter, an external electrode layer 6 having a constant width was formed on the internal electrode layer 3 along the short side of the substrate 1. The external electrode layer 6 was prepared by applying an Ag-epoxy paste as a base, and forming a Ni plating layer and a solder plating layer thereon.

  According to the above configuration, the resistor film 2 can be disposed directly under the external electrode layer 6 as shown in FIG. At this time, if the area of the internal electrode layer 3 is minimized, the area where the resistor film 2 can be disposed is maximized. In this embodiment, this area can be about 1.4 times that of the conventional one shown in FIG.

  In this example, a chip resistor having an outer shape of 2.0 mm × 1.2 mm × 0.55 mm was manufactured, but the resistance value was not limited regardless of using a nickel chrome alloy having a relatively low resistivity as the resistor film. Was able to obtain 2 MΩ. This resistance value is about twice as large as that of a conventional one having the same outer dimensions.

  In addition to ceramic, the substrate may be an insulator such as glass, or a substrate having an insulator layer formed on the surface of a conductive substrate. In this embodiment, the resistor film 2 is a thin film formed by a vacuum film formation method (evaporation method, sputtering method, ion plating method, chemical vapor deposition method, etc.), but in this invention, it is formed by a plating method printing method or the like. You may use the film | membrane which carried out.

  The material and the layer structure of the internal electrode layer 3 are determined in consideration of the material of the resistor film 2 and the external electrode layer 6, and it is desirable to include a layer of Ni or Pd that can be a solder barrier layer. The external electrode layer 6 may be formed by forming a metal serving as a solder barrier layer by a vacuum film forming method as a base for plating, and forming a solder layer thereon by solder plating.

  The resistor protective layer 4 can be formed by applying a glass paste in addition to a resin such as polyimide, and an insulating film such as SiO 2 may be formed by using a vacuum film forming method. Between the resistor protective layer 4 and the protective film 5, a layer intended to relieve stress applied to the resistor film from the outside can be formed.

External view of chip resistor The perspective view which shows the structure of the chip resistor of this invention in order of a manufacturing process. (A) Cross-sectional view of the chip resistor of the present invention taken along line AA in FIG. 1 (B) Cross-sectional view of the chip resistor of the present invention taken along line BB in FIG. 1 (C) FIG. 1 of the chip resistor of the present invention CC sectional view taken on the line The perspective view which shows the internal structure of the chip resistor of a prior art example in order of a manufacturing process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ceramic substrate 2 Resistor film 3 Internal electrode layer 4 Resistor protective layer (insulator film)
5 Protective film 6 External electrode layer

Claims (4)

In a chip resistor in which a film-like resistor is formed on an insulating surface of a substrate, this resistor film is covered with a protective film, and external electrode layers are formed on both ends of the substrate.
A chip resistor characterized in that the resistor film extends below the external electrode layer with an insulator film interposed between the resistor film and the external electrode layer.   2. The chip resistor according to claim 1, wherein a part of the opposing surface of the resistor film and the external electrode layer is lacked in the insulator film, and an internal electrode for electrically connecting the resistor film to the external electrode layer is formed in the lacked part.   3. The chip according to claim 2, wherein the portion of the resistor film serving as the internal electrode electrically connected to the external electrode layer is not more than half the length of the short side of the substrate on which the external electrode layer is formed. Resistor.   2. The chip resistor according to claim 1, wherein a resistor pattern is formed in a portion where the resistor film extends below the external electrode.