JP3201118B2 - Chip resistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip resistor, and more particularly, to an inexpensive chip resistor which does not fluctuate in resistance during the manufacturing process and during soldering.

[0002]

2. Description of the Related Art A conventional chip resistor is shown in FIG.
As shown in FIG. 2B, a thick or thin resistive film 4 formed on an insulating substrate 3 made of ceramic such as alumina is used. Cr, Ni, Ag formed by plating
And a protective film 10 formed by baking glass glaze for protecting the resistive film.

[0003] Incidentally, a protective film 10 made of glass glaze.
Requires sintering at 600 to 800 ° C., and the resistance value and temperature coefficient of the resistive film shift at high temperatures, so that formation of a protective film by glass glaze has a low yield, and solderability of end electrodes is poor. There was a problem that it reduced.

As a countermeasure against this problem, there is a method of forming a metal oxide (nitride) as a protective film by sputtering, for example, which can be formed by a low-temperature process, but it requires expensive equipment and is difficult in terms of cost. On the contrary,
It is very advantageous to use a resin-based (heat-curable, UV-curable, etc.) protective film in terms of resistance value shift and cost.

[0005]

However, since the resin-based resin described above has weaker adhesive strength and adhesiveness than glass glaze, the solder 11 is connected to the end electrode 9 at the time of soldering as shown in FIG. And the high-temperature solder 11 flips up the protective film 5 made of resin and enters the same, so-called solder erosion of the resistor occurs at the boundary with the resistive film 4, and the resistance value fluctuates. there were.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and has no problem of solder erosion of a resistor even if a protective film such as a resin having a relatively low adhesive strength is used, and a chip resistor having a stable resistance value. The task is to provide

[0007]

In order to solve the above-mentioned problems, the present invention provides an insulating substrate and an insulating substrate formed on an upper surface of the insulating substrate.
Resistance film connected to the resistance film and the insulating substrate
A first electrode formed of a material that is hardly wetted by solder formed over the upper surface and the end surface, and a first electrode formed on the end surface of the insulating substrate.
Over the top, and over the end and bottom surfaces of the insulating substrate
A second electrode solder wettability is formed is made of a material
Is a chip resistor having:

[0008]

When the chip resistor of the present invention is soldered to a circuit board, the solder does not spread to the portion covered with the first electrode made of a material having poor solder wettability, and the solder has good solder wettability. The high-temperature solder does not spread to the resistive film because it spreads only to the portion covered by the second electrode. Therefore, no solder erosion of the resistive film and no change in the resistance value occur.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a chip resistor according to the present invention will be described with reference to FIGS. 1 to 4. The same parts as those of the prior art will be described with the same reference numerals.

FIG. 1 is a sectional view of a chip resistor according to the present invention, in which a resistive film 4 is formed on an upper surface of a chip-shaped insulating substrate 3 made of ceramic such as alumina so as to reach both ends. A first electrode 1 having poor solder wettability is formed on a part of the resistive film 4 and an end face of the insulating substrate 3 at an end of the substrate, and further overlaps a part of the first electrode 1 on the end face of the insulating substrate 3. The second electrode 2 is formed on the lower surface of the substrate as described above. On the upper surface of the insulating substrate 3, a protective film 5 made of a resin for protecting the resistance film 4 is formed so as to be in contact with the first electrode 1. Hereinafter, a method of manufacturing the chip resistor will be described.

First, as shown in FIG. 2A, a chip-shaped insulating substrate 3 made of ceramic such as alumina is placed on a substrate.
A thin film resistive film 4 made of NiCr or the like is masked by a mask 6 into a required shape by sputtering in an argon gas atmosphere of ^-3 torr. This resistance film 4
May be formed in the state of the mother substrate before being cut into chips.

Next, as shown in FIG. 2B, a first electrode 1 having poor solder wettability is formed so that a part of the surface of the insulating substrate 3 on the resistor side overlaps the resistive film 4. This is also 10
^The mask 7 is formed by masking Cr or the like into a required shape in a ^-3 torr argon gas. At this time, the insulating substrate 3 is formed into a mask shape such that the end face of the insulating substrate 3 also has a sputtering film. The length of the resistor not in contact with the end electrode, that is, the resistance value is determined by the mask 7 on the resistive film 4.

Next, as shown in FIG. 2 (c), the required shape is, for example, Cr, Ni, and Ag in the same 10 ^-3 argon gas from the back surface of the insulating substrate 3 where the resistive film 4 is not provided. The second electrode configuration with good solderability
Is formed. At this time, the second electrode 2 is also formed on the first electrode 1 on the end surface of the insulating substrate 3 so as to overlap.

Further, if necessary, resistance value adjustment (trimming) is performed, and finally epoxy resin is applied and cured (150 ° C., 10 minutes) by a screen printing method or the like, and is made of a resin as shown in FIG. A protective film 5 is formed.

The material of the resistive film 4 is not limited to Ni and Cr, but may be a thick film or another method. The material of the first electrode 1 only needs to be non-wetting as a result of the solder, and is not particularly limited to the embodiment. Similarly, the material and the layer structure of the second electrode 2 are not limited as long as the solderability is good.

For electrode formation, a dry plating method typified by sputtering shown in the above embodiment is preferable from the viewpoint of reliability, but is not particularly limited, and another thick film, wet plating or the like may be used. Also, since the present invention can prevent solder wet-up on the resistive film, the presence or absence of a protective film, the material of the protective film,
The construction method is not limited to those of the embodiment.

FIG. 3 shows another embodiment of the present invention, in which the second electrode 2 is formed up to the surface of the substrate 3 having the resistive film 4. In this case, the first
Electrode 1 covers this surface more than the second electrode 2,
The surface end of the second electrode 2 and the surface of the resistive film 4 are separated from each other with the first electrode 1 interposed therebetween, so that the wetting of the solder to the resistive film 4 is prevented.

In the embodiment shown in FIG. 4, the contact between the resistive film 4 and the first electrode 1 is upside down. First, the first electrode 1 is formed, and the first electrode 1 is formed thereon. The resistive film 4 is formed so as to be electrically connected to the electrode 1, and then the second electrode 2 is formed so as to overlap only with the first electrode 1. In this case, the formation of the resistance film 4 and the formation of the second electrode 2 may be performed in reverse.

Although the present invention has been described by taking a chip resistor as an example, it goes without saying that the present invention can also be applied to a composite component having a resistive film provided on the main surface.

[0020]

As described above, according to the present invention,
A first electrode made of a material in which an end electrode of the chip resistor is in contact with the resistive film and hardly wetted by solder, and a first electrode and at least a part of the first electrode are provided so as to be overlapped with each other and separated from the resistive film. Since the second electrode is made of a material having good solder wettability, the portion where the end electrode and the resistor are in contact with each other is not wet by the solder, and the resistance of the resistor at the boundary with the resistive film is reduced. No breakage occurs, so that the resistance value does not change due to soldering.

In addition, when a protective film for the resistive film is formed, it is possible to prevent the high-temperature solder from getting wet, so that the protective film for the resistor can be formed by an inexpensive material and method, resulting in cost reduction. Further, since the protective film can be formed at a low temperature at the time of formation, the resistance value does not change.

[Brief description of the drawings]

FIG. 1 is a sectional view of a chip resistor according to the present invention.

FIG. 2 shows the manufacturing process of the chip resistor of the present invention (a).
It is process drawing shown in order of (b) and (c).

FIG. 3 is a sectional view of another example of the chip resistor of the present invention.

FIG. 4 is a sectional view of another example of the chip resistor of the present invention.

FIG. 5A is a sectional view of a conventional chip resistor, and FIG. 5B is a perspective view thereof.

FIG. 6 is a partially enlarged sectional view showing a soldering state of a conventional chip resistor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st electrode 2 2nd electrode 3 Insulating substrate 4 Resistive film 5 Protective film made of resin 6, 7, 8 Mask 9 End electrode 10 Protective film by glass glaze 11 Solder

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-243073 (JP, A) JP-A-3-284801 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01C 1/00-7/00

Claims (1)

(57) [Claims] An insulating substrate formed on an upper surface of the insulating substrate;
Resistive film connected to the resistive film and on the upper surface of the insulating substrate
And a first electrode made of a material that is hardly wetted by solder and formed on the end face, and on the first electrode at the end face of the insulating substrate.
Overlaps and forms over the end and bottom surfaces of the insulating substrate
And a second electrode made of a material having good solder wettability.
Chip resistor to be.