JP2003224002A - Chip resistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chip resistor not suffering from disconnection in top electrode layers and excellent in sulfurization resistance even when used in a gas sulfide containing atmosphere. <P>SOLUTION: A protection layer 14 made of a resin based material covers the part of a resistor layer 13 between a pair of top electrode layers 12 and part of overlaying part of the resistor layer 13 with the pair of the top electrode layers 12. A Ni plate layer 16 is formed to cover end face terminals 15, the parts of the top electrode layers 12 not covered by the resistor layer 13, and the part of the resistor layer 13 not covered by the protection layer 14. Moreover, an Sn-based plate layer 17 is formed to cover the Ni plate layer 16. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip resistor used in a high-density wiring circuit, and more particularly to a chip resistor used in a sulfurized atmosphere.

[0002]

2. Description of the Related Art In recent years, with the ever-increasing demand for light, thin, short and small electronic devices, very small chip resistors are often used as chip resistors to increase the wiring density of circuit boards. It's starting to happen.

A conventional chip resistor will be described below.

FIG. 2 (a) is a perspective view of a conventional chip resistor, and FIG. 2 (b) is a sectional view taken along line BB 'of FIG. 2 (a).

In FIGS. 2A and 2B, 1 is a substrate made of a 96 alumina substrate, 2 is a pair of upper surface electrode layers formed on both ends of the upper surface of the substrate 1, and the pair of upper surface electrode layers 2
Is composed of a silver-based thick film electrode. A resistor layer 3 is formed so as to overlap a part of the pair of upper surface electrode layers 2. The resistor layer 3 is composed of a ruthenium-based thick film resistor. Reference numeral 4 denotes a protective layer formed so as to completely cover the resistor layer 3, and reference numeral 5 denotes a pair of end surface electrodes formed on both end surfaces of the substrate 1 so as to be electrically connected to the pair of upper surface electrode layers 2. Is. Reference numerals 6 and 7 denote a Ni plating layer and a tin-based plating layer formed so as to cover the exposed portions of the end surface electrode 5 and the upper surface electrode layer 2, and the Ni plating layer 6 and the tin-based plating layer 7 ensure solderability. It is provided to do so.

[0006]

In the conventional chip resistor described above, the chip resistor is soldered and mounted on the printed circuit board at the boundary portion 8 between the protective layer 4, the tin-based plating layer 7 and the Ni plating layer 6. Sometimes, thermal shock during soldering tends to cause gaps. Furthermore, when an electric product incorporating a printed circuit board on which this chip resistor is mounted is used in an atmosphere containing a sulfurizing gas such as a hot springs, the sulfurizing gas enters inside through the gap formed in the boundary portion 8, and The sulfide gas directly reacts with silver forming the upper electrode layer 2 to form silver sulfide. Since this silver sulfide is an insulator, when the reaction with silver progresses, the chip resistor will become the upper electrode layer 2
There is a problem that a defect such as a disconnection occurs at the part.

In order to solve the above problems, the upper electrode layer 2 may simply be replaced with a gold electrode which has no problem even if it is used in a sulfurizing atmosphere. However, this gold electrode is very expensive and therefore The chip resistor using this gold electrode has a problem that it becomes expensive.

The present invention solves the above-mentioned conventional problems. Even when used in an atmosphere containing a sulfurizing gas, no disconnection occurs in the upper electrode layer, and the sulfurating resistance is excellent. The present invention is intended to provide a chip resistor having the same structure.

[0009]

In order to achieve the above object, the present invention has the following constitution.

According to a first aspect of the present invention, there is provided a substrate, a pair of upper surface electrode layers formed of silver-based thick film electrodes formed on both ends of an upper surface of the substrate, and the pair of upper surface electrode layers. A resistor layer made of a ruthenium-based thick film resistor formed so as to overlap a part of the resistor layer, and a protective layer covering the resistor layer,
A pair of end face electrodes formed on both end faces of the substrate and electrically connected to the pair of upper face electrode layers, a Ni plating layer covering the end face electrodes, and a tin-based plating layer covering the Ni plating layer. The protective layer is made of a resin system and is configured to cover a portion of the resistor layer located between the pair of upper surface electrode layers and a portion of a portion overlapping with the pair of upper surface electrode layers. And the Ni plating layer is
In addition to the end face electrodes, it is configured to cover a portion of the upper surface electrode layer that is not covered by the resistor layer and a portion of the resistor layer that is not covered by the protective layer, and further the tin-based plating layer is According to this configuration, the Ni plating layer is completely covered. According to this configuration, a ruthenium-based high resistance to sulfidation is provided just below the boundary between the protective layer and the tin-based plating layer and the Ni-plating layer in the chip resistor. Since the resistor layer made of thick film resistor is located, even when the sulfide gas enters the boundary portion through the gap created by the thermal shock during soldering when used in the atmosphere containing the sulfide gas. This sulfide gas comes into contact with the resistor layer composed of a ruthenium-based thick film resistor having high sulfide resistance, which allows the sulfide gas to form the upper electrode layer as in the conventional case. Since it does not directly react with silver to form silver sulfide, it does not cause disconnection in the upper electrode layer, and as a result, it is possible to obtain a chip resistor having excellent sulfide resistance. . Also, since the protective layer is made of resin, this protective layer is about 2
It can be formed at a low temperature of 00 ° C, which allows
Since the resistance value corrected by laser trimming does not change when the protective layer is formed, it has an effect that a highly accurate chip resistor can be obtained.

The invention according to claim 2 of the present invention is
The end face electrode is made of a resin system in which a conductive powder containing Ni as a main component and a resin component are mixed. According to this configuration, the end face electrode can be formed at a low temperature of about 200 ° C., and thus laser trimming is performed. The resistance value corrected by does not change when the end face electrode is formed.As a result, a highly accurate chip resistor is obtained, and since the silver-based material is not used as the end face electrode material, It also has a function and effect that excellent sulfide resistance is obtained.

The invention according to claim 3 of the present invention is
The end face electrode is composed of a thin film sputtering system containing Ni-Cr as a main component.
Since it can be formed at a low temperature of 0 ° C., the resistance value corrected by laser trimming does not change during the formation of the end face electrode, and as a result, a highly accurate chip resistor can be obtained and the end face electrode material can be obtained. Since it does not use a silver-based material, it has an effect that excellent sulfurization resistance can be obtained.

The invention according to claim 4 of the present invention is
The Ni plating layer is formed by electrolytic plating in a plating bath having a PH of 3.6 to 4.4, and the tin-based plating layer is formed by PH.
It is formed by electrolytic plating in a plating bath of 3.6 to 4.6. According to this configuration, since the Ni plating layer and the tin-based plating layer are formed by electrolytic plating, respectively, a ruthenium-based thick film is formed. The Ni plating layer and the tin-based plating layer can be formed in a stable state on the resistor layer composed of the resistor, and as a result, when the Ni plating layer or the boundary between the tin-based plating layer and the protective layer is soldered. Even if the sulfide gas enters inside through the gap generated by the thermal shock of, the Ni plating layer and the tin-based plating layer are formed in a stable state on the resistor layer, so that the sulfide gas causes the sulfide gas to pass through. The effect on the glass component in the layer can be suppressed, and as a result, stable resistance performance can be ensured.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A chip resistor according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 (a) is a perspective view of a chip resistor according to an embodiment of the present invention, and FIG. 1 (b) is A in FIG. 1 (a).
FIG. 6 is a sectional view taken along the line AA.

In FIGS. 1A and 1B, 11 is a substrate made of a 96 alumina substrate, 12 is a pair of upper surface electrode layers formed on both ends of the upper surface of the substrate 11, and the pair of upper surface electrode layers 12 are It is composed of a silver-based cermet thick film electrode. Reference numeral 13 is a resistor layer formed so as to overlap a part of the pair of upper surface electrode layers 12, that is, electrically connected, and the resistor layer 13 is composed of a ruthenium-based thick film resistor. . Reference numeral 14 is a protective layer formed so as to cover a portion of the resistor layer 13 located between the pair of upper surface electrode layers 12 and a portion of the portion overlapping with the pair of upper surface electrode layers 12. 14 is made of an epoxy resin. Reference numeral 15 denotes a pair of end surface electrodes formed on both end surfaces of the substrate 11 so as to be electrically connected to the pair of upper surface electrode layers 12, and the pair of end surface electrodes 15 are made of Ni.
It is composed of a resin-based material obtained by mixing a conductive powder of a system and a resin component. Reference numeral 16 is a Ni plating layer that covers the pair of end surface electrodes 15. The Ni plating layer 16 is a portion other than the end surface electrodes 15 in the upper surface electrode layer 12 not covered by the resistor layer 13 and the resistor. It is formed so as to cover a portion of the layer 13 which is not covered by the protective layer 14. Reference numeral 17 is a tin-based plating layer formed so as to completely cover the Ni plating layer 16.

Next, a method of manufacturing the chip resistor having the above structure will be described.

First, a sheet-shaped substrate made of a 96-alumina substrate having excellent heat resistance and insulation is received. In order to divide the sheet-like substrate into strips and individual pieces, grooves for division (molding at the time of green sheet) are formed in advance.

Next, a cermet thick film silver paste was screen-printed on the upper surface of the sheet-shaped substrate and dried, and a belt type continuous baking furnace was used at a temperature of 850 ° C. for a peak time of 6 minutes and an IN-OUT time of 45. The upper surface electrode layer 12 is formed by firing according to the minute profile.

Next, a thick film resistor paste containing ruthenium oxide as a main component is screen-printed on a sheet-like substrate so as to overlap with a part of the upper electrode layer 12, that is, electrically connected to the belt, and a belt is formed. 850 by the continuous firing furnace
The resistor layer 13 is formed by baking at a temperature of C. with a profile having a peak time of 6 minutes and an IN-OUT time of 45 minutes.

Next, in order to make the resistance value of the resistor layer 13 between the upper electrode layers 12 uniform, a part of the resistor layer 13 is cut off by laser light to correct the resistance value (L cut, 30 mm).
/ Sec, 12 kHz, 5 W).

Next, the portion of the resistor layer 13 located between the pair of upper surface electrode layers 12 and the pair of upper surface electrode layers 1
The epoxy resin paste was screen-printed so as to cover a part of the portion overlapping 2 and the temperature was set to 200 ° C. in a belt-type continuous curing furnace at a peak time of 30 minutes for IN.
The protective layer 14 is formed by curing with a curing profile of −OUT time 60 minutes.

Next, as a preparatory step for forming the end face electrode 15, a primary substrate division for dividing the sheet-like substrate into strip substrates is performed to expose the end face portion where the end face electrode 15 is formed.

Next, the Ni-based conductive powder and the resin component are mixed with the exposed end face portion of the strip-shaped substrate so as to overlap a part of the upper surface electrode layer 12, that is, to be electrically connected. The resulting resin-based electrode paste is applied with a roller, and a belt-type continuous curing furnace is used to
At a temperature of ℃, peak time 30 minutes, IN-OUT time 60
By curing with a minute curing profile,
The end face electrode 15 is formed.

Next, as a preparatory step for electrode plating, the strip-shaped substrate on which the end surface electrodes 15 are formed is divided into individual substrates, and the secondary substrate is divided to obtain individual substrates.

Finally, the end face electrodes 15 on the individual substrate, the portions of the upper surface electrode layer 12 not covered by the resistor layer 13 and the portions of the resistor layer 13 not covered by the protective layer 14 are covered. Then, the Ni plating layer 16 is formed by electrolytic plating.
By forming the tin-based plating layer 17 by electrolytic plating so as to completely cover the plating layer 16, the chip resistor is manufactured. In this case, the Ni plating layer 16 has PH 4.0.
Ni plating bath is used, and the tin-based plating layer 17 is P
An H4.1 tin-based plating bath was used.

In the chip resistor according to the embodiment of the present invention described above, the protective layer 14 overlaps the portion of the resistor layer 13 located between the pair of upper surface electrode layers 12 with the pair of upper surface electrode layers 12. The Ni plating layer 16 is formed so as to cover a portion of the upper surface electrode layer 12, and the Ni plating layer 16 is formed so as to cover a part of the existing portion and the protective layer 14 in the resistor layer 13. Since the tin-based plating layer 17 is configured so as to cover the portion not covered with and the Ni-based plating layer 16 is completely covered, the protective layer 14 and the tin-based plating layer in this chip resistor are formed. 17 and Ni plating layer 16
The resistor layer 13 made of a ruthenium-based thick film resistor having high sulfide resistance is located immediately below the boundary portion 18 of the sulphate. As a result, when the sulfide gas is used in an atmosphere containing sulfide gas, Even if it enters the boundary portion 18 through a gap generated by thermal shock during soldering,
This sulfide gas comes into contact with the resistor layer 13 made of a ruthenium-based thick film resistor having a high sulfide resistance, whereby the sulfide gas directly reacts with silver forming the upper electrode layer 12 as in the conventional case. Since silver sulfide is not formed, disconnection does not occur in the upper electrode layer 12, and as a result, a chip resistor having excellent sulphidation resistance can be obtained.

Since the protective layer 14 is made of a resin such as an epoxy resin, the protective layer 14 can be formed at a low temperature of about 200 ° C., so that the resistance value corrected by laser trimming can be obtained. Does not change when the protective layer 14 is formed, so that a highly accurate chip resistor can be obtained.

Since the end face electrode 15 is made of a resin system in which Ni-based conductive powder and a resin component are mixed, the end face electrode 15 can be formed at a low temperature of about 200.degree. As a result, the resistance value corrected by laser trimming does not change when the end face electrode 15 is formed, so that a highly accurate chip resistor can be obtained, and the end face electrode 15 is made of a silver-based material. Since, is not used, it is possible to obtain a product excellent in sulfidation resistance.

Further, in the above-described embodiment of the present invention, since the Ni plating layer 16 and the tin-based plating layer 17 are formed by electrolytic plating, respectively, the resistance layer 13 made of a ruthenium-based thick film resistor is formed. The Ni plating layer 16 and the tin-based plating layer 17 can be formed in a stable state at
As a result, the Ni plating layer 16 and the tin-based plating layer 17
Even if the sulfide gas enters the boundary portion 18 between the protective layer 14 and the protective layer 14 through the gap generated by thermal shock during soldering, the Ni plating layer 16 and the tin-based plating layer 17 are stable on the resistor layer 13. By being formed in such a state, the influence of the sulfide gas on the glass component in the resistor layer 13 can be suppressed, and as a result, stable resistance performance can be secured.

Table 1 shows a chip resistor according to one embodiment of the present invention and a conventional chip resistor, which are mounted on a printed circuit board by flow soldering, 100 pieces each, and are subjected to a sulfide gas test (60 ° C., 95 ° C.). 10 in% RH atmosphere
This is a result of carrying out a test for examining the number of generated silver sulfides by allowing to stand for 100 hours in a state of containing 000 ppm of H ₂ S).

[0032]

[Table 1]

As is clear from Table 1, in the conventional chip resistor (conventional product), out of 100, 10 silver sulfides were generated. Out of 100 pieces of the container (invention product), no silver sulfide was generated, and the container had excellent resistance to sulfidation.

In the embodiment of the present invention described above, the end surface electrode 15 is formed by applying and curing the resin-based electrode paste formed by mixing the Ni-based conductive powder and the resin component. However, the invention is not limited to this, and the end face electrode 15 may be configured by a thin film sputtering system containing Ni—Cr as a main component, and in this case also, the end face electrode 1
Since No. 5 can be formed at a low temperature of about 200 ° C., the resistance value corrected by laser trimming does not change when the end face electrode 15 is formed, as in the above-described embodiment of the present invention. A highly accurate chip resistor can be obtained, and since a silver-based material is not used as a material for the end face electrode 15, an excellent sulfur resistance can be obtained.

In the embodiment of the present invention described above, when the Ni plating layer 16 is formed, N of PH 4.0 is used.
In the case of using the i-plating bath and forming the tin-based plating layer 17, the tin-based plating bath of PH4.1 was used, but the PH of the plating bath is not limited to this. The pH of the plating bath is preferably in the range of 3.6 to 4.4, and the pH of the tin-based plating bath is 3.6 to 4.4.
A range of 4.6 is preferred.

Further, in the above-described one embodiment of the present invention, the case where the resistance value is corrected by the laser beam after the resistance layer 13 is formed has been described, but after the resistance layer 13 is formed. Even when the precoat glass layer is formed by printing and baking in a pattern smaller than the protective layer 14 and then the resistance value is corrected by the laser beam, the same effect as that of the embodiment of the present invention can be obtained. It is a thing.

[0037]

As described above, the chip resistor of the present invention is
The protective layer is configured to cover a portion of the resistor layer located between the pair of upper surface electrode layers and a portion of a portion overlapping with the pair of upper surface electrode layers, and the Ni plating layer is formed on the portion other than the end surface electrodes. A part of the upper surface electrode layer that is not covered by the resistor layer and a part of the resistor layer that is not covered by the protective layer, and tin so as to completely cover the Ni plating layer. Since the chip-based plating layer is formed, a resistor layer made of a ruthenium-based thick film resistor having high sulfidation resistance is provided just below the boundary between the protective layer and the tin-based plating layer and the Ni plating layer in this chip resistor. As a result, when used in an atmosphere containing sulfide gas, the sulfide gas entered the inside of the boundary through a gap created by thermal shock during soldering. However, this sulfide gas comes into contact with the resistor layer composed of a ruthenium-based thick film resistor having high sulfide resistance, which allows the sulfide gas to directly react with the silver forming the upper electrode layer as in the conventional case. Since the formation of silver sulfide is eliminated, disconnection does not occur in the upper electrode layer portion, and as a result, it is possible to obtain a chip resistor having excellent sulfidation resistance. Further, since the protective layer is made of a resin system, the protective layer can be formed at a low temperature of about 200 ° C., so that the resistance value corrected by laser trimming changes when the protective layer is formed. Therefore, there is an effect that a very accurate chip resistor can be obtained.

[Brief description of drawings]

FIG. 1A is a perspective view of a chip resistor according to an embodiment of the present invention, and FIG. 1B is a sectional view taken along the line AA ′ of FIG.

FIG. 2A is a perspective view of a conventional chip resistor. (B) BB 'line sectional drawing of (a)

[Explanation of symbols]

11 board 12 Top electrode layer 13 Resistor layer 14 Protective layer 15 Edge electrode 16 Ni plating layer 17 Tin-based plating layer

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5E028 AA04 BA03 BB01 CA01 DA01                       EA01 EB01 JC05                 5E033 AA02 BB06 BC01 BD01 BE01                       BH01

Claims (4)

[Claims] 1. A substrate, a pair of upper surface electrode layers made of silver-based thick film electrodes formed on both ends of the upper surface of the substrate, and formed so as to partially overlap the pair of upper surface electrode layers. A resistor layer formed of a ruthenium-based thick film resistor, a protective layer covering the resistor layer, and a pair of end face electrodes formed on both end faces of the substrate and electrically connected to the pair of upper face electrode layers. And a Ni plating layer covering the end face electrode and the Ni plating layer.
A tin-based plating layer covering the plating layer, the protective layer is made of a resin, and a portion of the resistor layer located between the pair of upper surface electrode layers and a portion of the portion overlapping with the pair of upper surface electrode layers. In addition to the end face electrodes, the Ni plating layer is covered with a portion of the upper surface electrode layer that is not covered by the resistor layer and the protective layer of the resistor layer. A chip resistor configured to cover the unplated portion, and the tin-based plating layer to completely cover the Ni plating layer. 2. The end face electrode is made of a resin system in which a conductive powder containing Ni as a main component and a resin component are mixed.
The listed chip resistor. 3. The chip resistor according to claim 1, wherein the end face electrode is constituted by a thin film sputtering system containing Ni—Cr as a main component. 4. A Ni plating layer is formed by electrolytic plating in a plating bath of PH 3.6 to 4.4, and a tin-based plating layer is formed by electrolytic plating in a plating bath of PH 3.6 to 4.6. The chip resistor according to claim 1.