JPH07169601A - Square-shaped chip resistor and its manufacture - Google Patents

Abstract

PURPOSE:To provide a chip resistor excellent in sulfur resistance and low in cost, in a square-shaped chip resistor which is mounted in a lump with other chip resistors. CONSTITUTION:A pair of second top electrode layers 5 being so made as to lie upon one part of the first top electrode layer 2 is so made as to overlap one part of the top of a protective layer 6, so the first top electrode layer 2 is never corroded by sulfide gas, and it is hard to cause wire breaking.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rectangular chip resistor used in a high density wiring circuit and a method for manufacturing the same.

[0002]

2. Description of the Related Art An example of the structure of a conventional thick film type rectangular chip resistor is shown in FIG. 3 (a) is a perspective view, FIG.
(B) is a sectional view taken along the line AA 'in (a).

A conventional rectangular chip resistor is a pair of upper electrode layers 11 made of a pair of silver-based thick films formed on a 96% alumina substrate 10 and a ruthenium-based thick film formed so as to be connected to the upper electrode layers 11. The resistance layer 12 is formed of a film, a glass layer 14 that completely covers the resistance layer, and a side surface electrode layer 13 that partially overlaps the top surface electrode layer 11. The Ni plating layer 15 and the solder plating layer 1 are formed on the exposed surfaces of the upper surface electrode layer 11 and the side surface electrode layer 13 in order to secure solderability.
6 is formed.

[0004]

However, the glass layer 14, the solder plating layer 16 and the N layer of this rectangular chip resistor are used.
At the boundary 17 of the i-plated layer 15, when the chip resistor is mounted on the printed circuit board by soldering, a gap is likely to be formed due to thermal shock during soldering. Furthermore, when an electric product mounted with this chip resistor is used in an atmosphere containing a sulfurizing gas such as in a hot spring, the sulfurizing gas enters the gap 17,
Reacts with the upper electrode layer 11 to form silver sulfide. Since this silver sulfide is an insulator, there is a problem that when the reaction proceeds, the chip resistor is disconnected at the upper surface electrode 11 to cause insulation failure.

In order to solve this problem, the upper electrode layer may simply be replaced with a gold electrode or the like, but the cost of using the gold electrode is very high and is far from practical use.

The present invention solves such a problem, and an object of the present invention is to provide a chip resistor which is less likely to be broken even in a sulfide gas atmosphere at a low cost.

[0007]

In order to solve this problem, the present invention provides an insulating substrate, a pair of silver-based first upper surface electrode layers formed on the insulating substrate, and a first upper surface electrode layer. A resistance layer partially overlapping with the first upper surface electrode layer, a pair of end surface electrode layers connected to the first upper surface electrode layer and formed at an end portion of the insulating substrate; a protective layer completely covering the resistance layer on the resistance layer; A pair of second upper surface electrode layers formed on the first upper surface electrode layer so as to overlap a part of the first upper surface electrode layer, and the second upper surface electrode layer overlaps a part of the upper surface of the protective layer. There is something.

[0008]

As a result, since the second upper surface electrode layer is formed so as to overlap the protective film, even if a gap occurs due to thermal shock during soldering, the sulfurization gas does not easily reach the first upper surface electrode layer, and therefore, the sulfurization is not performed. It is possible to provide a rectangular chip resistor with greatly improved reliability against gas at low cost without using expensive electrodes such as gold electrodes.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIGS. 1A and 1B are a perspective view and a sectional view showing a rectangular chip resistor according to the present invention.

In FIGS. 1A and 1B, 1 is 96%.
It is an alumina substrate. 2 is a first upper surface electrode layer. Reference numeral 4 is a resistance layer. Reference numeral 5 is a second upper surface electrode layer. 6 is an overcoat glass layer as a protective layer.

The prismatic chip resistor of the present invention having such a structure has a pair of first silver-based thick films on a 96% alumina substrate 1.
The upper surface electrode layer 2, the resistance layer 4 of a ruthenium-based thick film that overlaps a portion of the first upper surface electrode layer 2, the glass layer 6 that completely covers the resistance layer 4, and the first upper surface electrode layer 2 are formed. The second upper surface electrode layer 5, the first upper surface electrode layer 2, and the end surface electrode layer 3 of a silver-based thick film that overlaps a part of the second upper surface electrode layer 5. In order to improve solderability on the exposed electrode surface,
The Ni plating layer 7 and the Sn-Pb plating layer 8 are formed.

Next, a method of manufacturing the rectangular chip resistor of the present invention shown in FIG. 1 will be described. First, a 96% alumina insulating plate having excellent heat resistance and insulation is accepted. This 96% alumina insulating plate is formed with a strip-shaped groove and a groove for splitting (molding with a green sheet) in order to divide it into individual pieces. Next, a thick film silver paste was screen-printed and dried on the surface of a 96% alumina insulating plate, and baked by a belt type continuous baking furnace at a temperature of 850 ° C. for a peak time of 6 minutes and an IN-OUT 45 minute profile, 1 The upper surface electrode layer 2 was formed.

Next, a thick film resistance paste containing RuO ₂ as a main component is screen-printed so as to overlap a part of the first upper surface electrode layer 2, and a peak time 6 at a temperature of 850 ° C. in a belt type continuous firing furnace. And a resistance layer 4 was formed by firing according to a profile of 45 minutes and IN-OUT 45 minutes.

Next, in order to make the resistance value of the resistance layer 4 between the first upper surface electrode layers 2 uniform, a part of the resistance layer 4 is destroyed by laser light to correct the resistance value (L cut, 100 mm / sec, 1
2 KHz, 5 W) was performed. Subsequently, a lead borosilicate glass paste was screen-printed so as to completely cover the resistance layer 4, and fired in a belt type continuous firing furnace at a temperature of 590 ° C. for a peak time of 6 minutes and an IN-OUT 50 minute firing profile. Then, the overcoat glass layer 6 was formed.

Next, a thick film silver paste is screen-printed and dried so as to overlap a part of the first upper surface electrode layer 2, and the peak time is 6 at a temperature of 600 ° C. in a belt type continuous firing furnace.
And a pair of second upper surface electrode layers 5 were formed by baking according to a profile of 45 minutes for IN-OUT. At this time
Length X in the longitudinal direction of the overlapping portion with the resistance layer shown in (a)
If the thickness is 0.2 mm or more, a gap is likely to be formed due to thermal shock during soldering. Next, as a preparatory step for forming the end face electrodes, the 96% alumina insulating plate was divided into strips to expose the end face electrodes, and strip-shaped 96% alumina insulating plates were obtained. A thick film silver paste was applied to the side surface of the strip-shaped 96% alumina insulating plate by a roller so as to overlap a part of the first upper surface electrode layer 2 and the second upper surface electrode layer 5, and the belt type continuous firing furnace was used to apply 600 At a temperature of ℃,
The end face electrode layer 3 was formed by firing with a firing profile of IN-OUT 45 minutes with a peak time of 6 minutes.

Next, as a preparatory step for electrode plating, a secondary substrate is divided into individual pieces of the strip-shaped 96% alumina insulating plate on which the end face electrode layer 3 has been formed.
Alumina substrate 1 was obtained. Finally, in order to prevent electrode erosion during soldering of exposed portions of the first upper surface electrode layer 2, the second upper surface electrode layer 5, and the end surface electrode layer 3 and to secure reliability of soldering, Ni plating is performed by electrolytic plating. Plating layer 7,
Subsequently, a Sn-Pb plated layer 8 was formed.

(Second Embodiment) Next, a second embodiment of the present invention will be described.

In FIG. 2, a rectangular chip resistor according to the present invention comprises a pair of first upper surface electrode layers 2 of a silver-based thick film on a 96% alumina substrate 1 and ruthenium overlapping a part of the first upper surface electrode layer 2. A thick system resistance layer 4, an overcoat glass layer 6 as a protective layer that completely covers the resistance layer 4, a second upper surface electrode layer 9 formed of a nickel chromium thin film formed on the first upper surface electrode layer 2, 1 is composed of an upper surface electrode layer 2 and an end surface electrode layer 3 of a silver-based thick film that partially overlaps the second upper surface electrode layer 9. In order to improve solderability, the exposed surface of the end surface electrode 3 and the second upper surface electrode layer 9 should have a Ni plating layer 7 and Sn.
-Pb plating layer 8 is formed.

Next, a method of manufacturing the rectangular chip resistor of the present invention shown in FIG. 2 will be described. First, a 96% alumina insulating plate having excellent heat resistance and insulation is accepted. This 96% alumina insulating plate is formed with a strip shape and a groove for division (by die molding at the time of green sheet) for dividing into a strip shape. Next, screen print a thick film silver paste on the surface of the 96% alumina insulating plate.
It was dried and fired in a belt type continuous firing furnace at a temperature of 850 ° C. at a peak time of 6 minutes and a profile of IN-OUT 45 minutes to form a first upper electrode layer 2.

Next, a thick film resistance paste containing RuO ₂ as a main component was screen-printed so as to overlap a part of the first upper surface electrode layer 2, and a peak time 6 at a temperature of 850 ° C. in a belt type continuous firing furnace. And a resistance layer 4 was formed by firing according to a profile of 45 minutes and IN-OUT 45 minutes.

Next, in order to make the resistance value of the resistance layer 4 between the first upper surface electrode layers 2 uniform, a part of the resistance layer 4 is destroyed by laser light to modify the resistance value (L cut, 100 mm / sec, 1
2 KHz, 5 W) was performed. Subsequently, a lead borosilicate glass paste was screen-printed so as to completely cover the resistance layer 4, and baked in a belt-type continuous baking furnace at a temperature of 590 ° C. for a peak time of 6 minutes and an IN-OUT 50 minute baking profile. Then, the overcoat glass layer 6 was formed.

Next, nickel chrome was formed by a thin film sputtering process so as to overlap a part of the first upper surface electrode layer 2 to form a second upper surface electrode layer 9 of a nickel chrome thin film. At this time, if the length Y in the longitudinal direction of the overlapping portion with the resistance layer shown in FIG. 2 (a) is 0.2 mm or more, a gap is likely to be formed due to thermal shock during soldering.

Next, as a preparation step for forming the end face electrodes, the 96% alumina insulating plate was divided into strips to expose the end face electrodes, and strip-shaped 96% alumina insulating plates were obtained. A thick film silver paste was applied to the side surface of the strip-shaped 96% alumina insulating plate by a roller so as to overlap a part of the first upper surface electrode layer 2 and the second upper surface electrode layer 5, and the belt type continuous firing furnace was used to apply 600 The end face electrode layer 3 was formed by firing at a temperature of ℃ for 6 minutes and a firing profile of IN-OUT 45 minutes.

Next, as a preparatory step for electrode plating, a secondary substrate is divided into individual pieces of the strip-shaped 96% alumina insulating plate on which the end face electrode layer 3 has been formed.
Alumina substrate 1 was obtained. Finally, in order to prevent electrode erosion during soldering of the exposed first upper surface electrode layer 2, second upper surface electrode layer 5, and end surface electrode layer 3 and to secure reliability of soldering, electrolytic plating is performed. A Ni plating layer 7 and a Sn-Pb plating layer 8 were formed.

Through the above steps, a rectangular chip resistor according to an embodiment of the present invention was obtained. The rectangular chip resistor according to this example was mounted on a printed circuit board by flow soldering, and left in a sulfide gas test (at 60 ° C., 95% RH (relative humidity) for 100 hours in an atmosphere containing 100 ppm of H ₂ S N = The results of carrying out 100) are shown in (Table 1).

[0027]

[Table 1]

From Table 1, it can be seen that the rectangular chip resistor of this example has excellent reliability.

In this embodiment, the second upper electrode layer is made of a silver thick film and a nickel chrome thin film, but may be a copper thick film or another metal film such as a copper or silver thin film.

[0030]

As is apparent from the above description, the insulating substrate, the pair of first silver-based upper surface electrode layers formed on the insulating substrate, and the resistance layer overlapping a part of the first upper surface electrode layer. ,
A pair of end face electrode layers connected to the first top face electrode layer and formed at an end of the insulating substrate, and a protective layer that completely covers the resistance layer are provided so as to overlap a part of the first top face electrode layer. By forming the pair of formed second upper surface electrode layers so as to overlap a part of the upper surface of the protective layer, it is possible to inexpensively provide a chip resistor that does not easily break even in a sulfide gas atmosphere, without using an expensive electrode material. That is an excellent effect.

[Brief description of drawings]

FIG. 1A is a perspective view showing the structure of a rectangular chip resistor according to a first embodiment of the present invention. FIG. 1B is a sectional view of the rectangular chip resistor.

FIG. 2A is a perspective view showing the structure of a rectangular chip resistor according to a second embodiment of the present invention. FIG. 2B is a sectional view of the rectangular chip resistor.

3A is a perspective view showing the structure of a conventional rectangular chip resistor, and FIG. 3B is a sectional view of the same rectangular chip resistor.

[Explanation of symbols]

 1 96% Alumina Substrate 2 First Top Electrode Layer 3 End Face Electrode Layer 4 Resistance Layer 5, 9 Second Top Electrode Layer 6 Overcoat Glass Layer 7 Ni Plating Layer 8 Solder Plating Layer

Claims (4)

[Claims] 1. An insulating substrate, a pair of silver-based first upper surface electrode layers formed on the insulating substrate, a resistance layer overlapping a part of the first upper surface electrode layer, and the first upper surface electrode layer. A pair of end face electrode layers that are connected to each other and are formed at the ends of the insulating substrate, a protective layer that completely covers the resistance layer on the resistance layer, and a part of the first top surface electrode layer on the first top surface electrode layer. A prismatic chip resistor comprising a pair of second upper surface electrode layers formed so as to overlap with each other, the second upper surface electrode layer overlapping a part of the upper surface of the protective layer. 2. The rectangular chip resistor according to claim 1, wherein the length of the overlapping portion of the protective layer and the second upper surface electrode layer in the longitudinal direction is 0.2 mm or more. 3. A step of forming a pair of silver-based first upper surface electrode layers on an insulating substrate, a step of forming a resistance layer so as to overlap a part of the first upper surface electrode layers, and the upper surface electrode layer. Forming a pair of end face electrode layers on the ends of the insulating substrate so as to connect to the insulating substrate, forming a protective layer on the resistance layer so as to completely cover the resistance layer, and forming a protective layer on the first upper surface electrode layer. And a step of forming a pair of second upper surface electrode layers so as to partially overlap with the first upper surface electrode layer, wherein the second upper surface electrode layer is formed by a thick film printing method using a silver-based printing paste after forming the protective layer. A method for manufacturing a rectangular chip resistor, which is characterized in that it is formed by printing. 4. A step of forming a pair of silver-based first upper surface electrode layers on an insulating substrate, a step of forming a resistance layer so as to partially overlap with the first upper surface electrode layer, and the upper surface electrode layer. Forming a pair of end face electrode layers on the ends of the insulating substrate so as to connect to the insulating substrate, forming a protective layer on the resistance layer so as to completely cover the resistance layer, and forming a protective layer on the first upper surface electrode layer. And a step of forming a pair of second upper surface electrode layers so as to partially overlap the first upper surface electrode layer, the second upper surface electrode layer is formed by forming a nickel-based thin film by a thin film sputtering method after forming a protective layer. A method of manufacturing a rectangular chip resistor, comprising: