GB2321558A - Chip resistor and method for manufacturing the same - Google Patents
Chip resistor and method for manufacturing the same Download PDFInfo
- Publication number
- GB2321558A GB2321558A GB9807983A GB9807983A GB2321558A GB 2321558 A GB2321558 A GB 2321558A GB 9807983 A GB9807983 A GB 9807983A GB 9807983 A GB9807983 A GB 9807983A GB 2321558 A GB2321558 A GB 2321558A
- Authority
- GB
- United Kingdom
- Prior art keywords
- resistive film
- film
- chip resistor
- resistor
- insulated substrate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
- H01C17/06—Apparatus or processes specially adapted for manufacturing resistors adapted for coating resistive material on a base
- H01C17/075—Apparatus or processes specially adapted for manufacturing resistors adapted for coating resistive material on a base by thin film techniques
- H01C17/14—Apparatus or processes specially adapted for manufacturing resistors adapted for coating resistive material on a base by thin film techniques by chemical deposition
- H01C17/18—Apparatus or processes specially adapted for manufacturing resistors adapted for coating resistive material on a base by thin film techniques by chemical deposition without using electric current
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C1/00—Details
- H01C1/14—Terminals or tapping points or electrodes specially adapted for resistors; Arrangements of terminals or tapping points or electrodes on resistors
- H01C1/142—Terminals or tapping points or electrodes specially adapted for resistors; Arrangements of terminals or tapping points or electrodes on resistors the terminals or tapping points being coated on the resistive element
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
- H01C17/006—Apparatus or processes specially adapted for manufacturing resistors adapted for manufacturing resistor chips
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
- H01C17/06—Apparatus or processes specially adapted for manufacturing resistors adapted for coating resistive material on a base
- H01C17/065—Apparatus or processes specially adapted for manufacturing resistors adapted for coating resistive material on a base by thick film techniques, e.g. serigraphy
- H01C17/06506—Precursor compositions therefor, e.g. pastes, inks, glass frits
- H01C17/06513—Precursor compositions therefor, e.g. pastes, inks, glass frits characterised by the resistive component
- H01C17/06533—Precursor compositions therefor, e.g. pastes, inks, glass frits characterised by the resistive component composed of oxides
- H01C17/0654—Oxides of the platinum group
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
Landscapes
- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Manufacturing & Machinery (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Apparatuses And Processes For Manufacturing Resistors (AREA)
- Non-Adjustable Resistors (AREA)
Abstract
A chip resistor which can detect an overcurrent with high accuracy is provided with an insulating substrate, a resistance section provided on the substrate, and a pair of electrode sections. Each electrode section has a surface electrode and the resistance section is composed of a lower resistance film which is connected to each of the surface electrodes of the electrode sections and provided on the surface of the insulating substrate, and an upper resistance film which is connected to the surface electrodes and provided on the surface of the lower resistance film. The sheet resistivity of the upper resistance film is made lower than that of the lower resistance film. A method for easily, efficiently and inexpensively manufacturing the chip resistor.
Description
SPECIFICATION
CHIP RESISTOR AND METHOD FOR PRODUCING THE SAME
FIELD OF ART
The present invention relates to a chip resistor and a method for producing the same, in particular to a chip resistor which can detect overcurrent with high accuracy and which is low in resistance, and a method for producing such a chip resistor easily at low cost.
BACKGROUND ART
Overcurrent protection circuits in compact size electronics products these days are provided with low-resistance chip resistors. Known types of such chip resistors include chip resistors wherein the resistor portion is formed on the insulated substrate by vapor deposition or sputtering, and the protective film covers the parts other than the electrode portions, which are instead plated; and chip resistors wherein a resistive metal foil is fixed to the insulated substrate with an adhesive and patterned byphotoetching, and a protective coating and electrodes are molded.
However, formation of the resistor portion by vapor deposition or sputtering should be carried out under vacuum, which lowers productivity; whereas fixing of the resistive metal foil to the insulated substrate with an adhesive should be carried out manually, which will cause lack of uniformity in adhesion strength of the resistive foils, and thus lowering of productivity.
If only the productivity of the resistive films is to be improved, the resistor portion may be formed of an ordinary resistor paste, such as a Pd-Ag paste or a Pd-Ag-RuO2 paste, by screen printing, which is regarded as the most productive method at present. However, when the resistor portion is formed of a single material only by screen printing, a resistive film having as low resistance as, forexample,100m or lower is hardly obtained. Therefore, this approach is not appropriate for producing the low-resistance chip resistors which seek to detect overcurrent with high accuracy.
Then another method is adopted for easy production of the low-resistance chip resistors, wherein the resistive film is formed of an electrically conductive paste containing glass powders. However, it has hardly been thought of reducing the temperature coefficient of resistance (abbreviated as TCR hereinbelow) of the resistor portion to, for example, about 500 ppm/ C or lower, and such low TCR has not been achieved in chip resistors by forming the electrically conductive film containing glass powders.
Accordingly, it is now demanded in the field of compact size electronics products to develop chip resistors at low cost which may be used in an overcurrent protection circuit of compact size electronics products, and which detect overcurrent with high accuracy.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a chip resistor which is low in resistance and TCR, and which detects overcurrent with high accuracy.
It is another object of the present invention to provide a method for easily and effectively producing at low cost a chip resistor which detects overcurrent with high accuracy.
According to the present invention, there is provided a chip resistor comprising
an insulated substrate,
a resistor portion on the insulated substrate, and
a pair of electrode portions, each of said electrode portions having a top electrode,
wherein said resistor portion consists of:
a lower resistive film connected to said top electrodes and provided on the insulated substrate, and
an upper resistive film connected to said top electrodes and provided on the lower resistive film,
wherein the upper resistive film has lower sheet resistivity than the lower resistive film.
According to the present invention, there is also provided a method for producing the chip resistor of the above type comprising the steps of:
(a) forming a pair of top electrodes on an insulated substrate by screen printing,
(b) forming a lower resistive film on the insulated substrate by screen printing so that said lower resistive film is connected to the top electrodes,
(c) forming an upper resistive film on the lower resistive film by electroplating or electroless plating so that said upper resistive film is connected to the top electrodes, said upper resistive film having lower sheet resistivity than the lower resistive film.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic longitudinal sectional view of an embodiment of the low-resistance chip resistor of the present invention.
PREFERRED EMBODIMENT OF THE INVENTION
It is essential for the chip resistor of the present invention that the resistor portion on the insulated substrate is composed of two layers, namely, a lower resistive film provided on the insulated substrate and an upper resistive film provided on the lower resistive film, and that the upper resistive film has lower sheet resistivity than the lower resistive film. With such two resistive films having different sheet resistivities, desired low resistance value can be achieved easily. Usually, the resistance value of as low as not higher than 100 mQ/L, preferably 22 to 47 m0/0 can be achieved. Therefore, the chip resistor may be used as an optimal resistor in an overcurrent protection circuit of compact size electronics products.
Incidentally, each of the upper and lower resistive films is directly connected to the pair of top electrodes on the insulated substrate.
In order for the chip resistor of the present invention to detect overcurrent with still higher accuracy, it is preferred that TCR of the resistor portion is low. Specifically, TCR is preferably not higher than 300 ppm/OC, more preferably 0 to 250 ppm/ C.
Such low TCR may be achieved by suitably selecting the material or thickness of each resistive film since the resistor portion is double-layered. In this case, it is preferred to select the material for each resistive film so that TCR of the upper resistive film is lower than TCR of the lower resistive film.
The lower resistive film is not particularly limited, and may be a Pd-Ag film or a Pd-Ag-RuO2 film for its low cost. The thickness of the lower resistive film is preferably 5 to 15 um. On the other hand, the upper resistive film is not particularly limited, and may be a nickel-containing film of relatively low TCR such as a Ni, Ni-P, Ni-Cu-P, Ni-W-P, Ni-Cr-P, or Ni-Re-P film.
The thickness of the upper resistive film is preferably 1 to 5 um. It is preferred to provide the upper resistive film all over the lower resistive film in order to reduce the resistance value without greatly changing TCR of the resistive films. For producing at low cost a chip resistor of the present invention which detects overcurrent with improved accuracy, it is preferred to make the lower resistive film with a Pd-Ag-containing film and the upper resistive film with a Ni-containing film.
The chip resistor of the present invention has a pair of electrode potions each having a top electrode, and usually each of the electrode portions may include an end electrode. Further, the upper resistive film may usually be covered with a protective film made of an epoxy resin or the like.
The method of the present invention is a method for easily and effectively producing the chip resistor of low resistance at low cost which detects overcurrent with high accuracy, by screen printing and electroplating or electroless plating.
According to the present method, step (a) of forming a pair of top electrodes on an insulated substrate by screen printing is first performed. The step (a) may be carried out by applying a conventional electrode material paste to the insulated substrate at predetermined locations by screen printing, and subsequently firing the applied paste.
Second, step (b) of forming a lower resistive film on the insulated substrate by screen printing so that the lower resistive film is connected to the top electrodes formed in step (a), is performed. The step
(b) may be carried out by applying a material for the lower resistive film, such as a Pd-Ag paste or a
Pd-Ag-RuO2 paste, to the insulated substrate at predetermined locations by screen printing so as to extend between and contact with the two top electrodes, and subsequently firing the applied paste.
Third, step (c) of forming an upper resistive film on the lower resistive film by electroplating or electroless plating so that the upper resistive film is connected to the top electrodes formed in step (a) is performed, wherein the upper resistive film has lower sheet resistivity than the lower resistive film. The step (c) may be carried out by applying a material for the upper resistive film, for example, a material which may give the upper resistive film lower sheet resistivity and preferably lower TCR than those of the lower resistive film, such as a metal material including
Ni, Ni-P, Ni-Cu-P, Ni-W-P, Ni-Cr-P, or Ni-Re-P, to the lower resistive film at predetermined locations, preferably to all over the lower resistive film, by electroplating or electroless plating so as to extend between and contact with the two top electrodes. In particular, when the upper resistive film is to be formed by electroless plating, it is preferred to eliminate the pretreatment with an activating strong acid solution (of pH 1 or lower, for example) such as a palladium chloride solution. An activating strong acid solution may raise TCR of the resistive films and reduce the resistance of the resistive films against overload.
The electroless plating without the activating solution may be performed by, for example, negatively charging the lower resistive film by electroplating to make the negative charge function as a trigger for the electroless plating reaction.
In the method of the present invention, optional steps such as forming a protective film, forming end electrodes, or forming plated electrodes by plating, may be performed in addition to the above steps.
EXAMPLES
The present invention will now be explained with reference to Examples taken in combination with the attached drawing, but the present invention is not limited to Examples.
Fig. 1 shows an embodiment of the chip resistor of the present invention, which is made up of alumina ceramics insulated substrate 11, resistive films composed of Pd-Ag lower resistive film 12 and Ni-Cu-P upper resistive film 13, electrode portions composed of Ag top and back electrode films 14, 15 and end electrodes 17, plated electrode films 18, and protective film 16.
The lower resistive film 12 is provided on the insulated substrate 11 with its two ends connected to two top electrodes 14, respectively. The upper resistive film 13 has lower sheet resistivity and lower
TCR than the lower resistive film 12, and is formed over the entire surface of the lower resistive film 12 with its two ends connected to two top electrodes 14, respectively.
The end electrodes 17 are provided on the right and left ends of the insulated substrate 11, with each of the end electrodes covering and contacting the end faces of top and back electrodes 14, 15 and the upper resistive film 13. The protective film 16 is provided on the upper resistive film 13. Each of the plated electrode films 18 is formed over an exposed portion of the upper resistive film 13 which is not covered with the protective film 16, Ag back electrode film 15, and end electrode 17.
For producing the above chip resistor, first an Ag paste is applied to the alumina ceramics substrate 11 at predetermined locations by screen printing, and fired to form a pair of Ag top electrode films 14. Second, a Pd-Ag paste is applied to the insulated substrate 11 by screen printing so as to extend between the Ag electrode films 14, and fired to form lower resistive film 12. Third, the lower resistive film 12 is plated with Ni-Cu-P material by electroless plating to form upper resistive film 13 having lower sheet resistivity than the lower resistive film 12. Next, Ag back electrode films 15 and protective film 16 are formed by screen printing followed by firing, and then end electrodes 17 are formed by applying and firing an electrode material. Finally, plated electrode films 18 are formed by plating Ag back electrode films 15, end electrodes 17, and the exposed portions of the upper resistive film 13 with an electrode material, thereby completing the production of the chip resistor.
The Ni-Cu-P upper resistive film 13 formed on the
Pd-Ag lower resistive film 12 by electroless plating may be replaced with an upper resistive film formed by electroplating with a nickel-containing metal such as
Ni, Ni-P, Ni-W-P, Ni-Cr-P, or Ni-Re-P.
According to the present embodiment, resistive films having resistance of 33 m 51 , 22 m Q, or even lower could be formed on a chip of 3.2 mm X 2.5 mm in size. Further,
TCR of such resistive films was not higher than 300 ppm/"C.
Claims (9)
1. A chip resistor comprising
an insulated substrate,
a resistor portion on the insulated substrate, and
a pair of electrode portions, each of said electrode portions having a top electrode,
wherein said resistor portion consists of:
a lower resistive film connected to said top electrodes and provided on the insulated substrate, and
an upper resistive film connected to said top electrodes and provided on the lower resistive film,
wherein the upper resistive film has lower sheet resistivity than the lower resistive film.
2. The chip resistor of claim 1 wherein said lower resistive film is selected from the group consisting of a Pd-Ag film and a Pd-Ag-RuO2 film, and wherein said upper resistive film is selected from the group consisting of a Ni film, a Ni-P film, a Ni-Cu-P film, a Ni-W-P film, a Ni-Cr-P film, and a Ni-Re-P film.
3. The chip resistor of claim 1 wherein resistance value of said resistor portion is not higher than 100 m 2 /Z.
4. The chip resistor of claim 1 wherein resistance value of said resistor portion is not higher than 22 to 47 m0/0.
5. The chip resistor of claim 1 wherein temperature coefficient of resistance (TCR) of said resistor portion is not higher than 300 ppm/OC.
6. The chip resistor of claim 1 further comprising a protective film on the upper resistive film.
7. A method for producing the chip resistor of claim 1 comprising the steps of:
(a) forming a pair of top electrodes on an insulated substrate by screen printing,
(b) forming a lower resistive film on the insulated substrate by screen printing so that said lower resistive film is connected to the top electrodes,
(c) forming an upper resistive film on the lower resistive film by electroplating or electroless rlating so that said upper resistive film is connected to the top electrodes, said upper resistive film having lower sheet resistivity than the lower resistive film.
8. The method of claim 7 wherein said lower resistive film is formed of a Pd-Ag-containing paste selected from the group consisting of a Pd-Ag paste and a Pd-Ag-RuO2 paste, and wherein said upper resistive film is formed of a Ni-containing metal selected from the group consisting of Ni, Ni-P, Ni-Cu-P, Ni-W-P, Ni-Cr-P, and
Ni-Re-P.
9. The method of claim 7 wherein, for forming said upper resistive film by electroless plating, surface of the lower resistive film is negatively charged in advance.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8225545A JP2896996B2 (en) | 1996-08-27 | 1996-08-27 | Low resistance chip resistor and method of manufacturing the same |
| PCT/JP1997/002955 WO1998009298A1 (en) | 1996-08-27 | 1997-08-26 | Chip resistor and method for manufacturing the same |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9807983D0 GB9807983D0 (en) | 1998-06-17 |
| GB2321558A true GB2321558A (en) | 1998-07-29 |
| GB2321558B GB2321558B (en) | 1999-10-27 |
Family
ID=16830979
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9807983A Expired - Lifetime GB2321558B (en) | 1996-08-27 | 1997-08-26 | Chip resistor and method for producing the same |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JP2896996B2 (en) |
| DE (1) | DE19780905C2 (en) |
| GB (1) | GB2321558B (en) |
| WO (1) | WO1998009298A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2014000854A1 (en) * | 2012-06-29 | 2014-01-03 | Isabellenhütte Heusler Gmbh & Co. Kg | Resistor, particularly a low-resistance current-measuring resistor |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4722318B2 (en) * | 2000-06-05 | 2011-07-13 | ローム株式会社 | Chip resistor |
| DE102006060634A1 (en) * | 2006-12-21 | 2008-06-26 | Robert Bosch Gmbh | Method for producing an electrical resistance on a substrate |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5067501A (en) * | 1973-10-15 | 1975-06-06 | ||
| JPS5678506U (en) * | 1979-11-20 | 1981-06-25 |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0567501A (en) * | 1991-05-23 | 1993-03-19 | Mitsubishi Electric Corp | Chip resistor |
-
1996
- 1996-08-27 JP JP8225545A patent/JP2896996B2/en not_active Expired - Lifetime
-
1997
- 1997-08-26 DE DE19780905T patent/DE19780905C2/en not_active Expired - Lifetime
- 1997-08-26 GB GB9807983A patent/GB2321558B/en not_active Expired - Lifetime
- 1997-08-26 WO PCT/JP1997/002955 patent/WO1998009298A1/en not_active Ceased
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5067501A (en) * | 1973-10-15 | 1975-06-06 | ||
| JPS5678506U (en) * | 1979-11-20 | 1981-06-25 |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2014000854A1 (en) * | 2012-06-29 | 2014-01-03 | Isabellenhütte Heusler Gmbh & Co. Kg | Resistor, particularly a low-resistance current-measuring resistor |
| US9437353B2 (en) | 2012-06-29 | 2016-09-06 | Isabellenhuette Heusler Gmbh & Co. Kg | Resistor, particularly a low-resistance current-measuring resistor |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH1070001A (en) | 1998-03-10 |
| GB9807983D0 (en) | 1998-06-17 |
| DE19780905T1 (en) | 1998-10-15 |
| DE19780905C2 (en) | 2003-03-20 |
| GB2321558B (en) | 1999-10-27 |
| JP2896996B2 (en) | 1999-05-31 |
| WO1998009298A1 (en) | 1998-03-05 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 789A | Request for publication of translation (sect. 89(a)/1977) | ||
| PE20 | Patent expired after termination of 20 years |
Expiry date: 20170825 |