JPH08316003A - Square type chip resistor and its manufacture - Google Patents

Abstract

PURPOSE: To provide a highly accurate square type chip resistor of low resistance and small TCR and a method for the manufacture with stability at low price. CONSTITUTION: A resistance film 13 is formed on a substrate 11 with a base layer 12 in between. A protective film 14 is formed in such a manner that it covers the resistance film 13 with both its ends left. End-face electrodes 15 are formed in such a manner that they enclose both the ends of the substrate 11 and that they connect the substrate with the portion of the resistance film 13 not covered with the protective film 14. This obtains a square type chip resistor of low resistance and small TCR.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly accurate rectangular chip resistor which is generally used in an electronic circuit or the like and has a small temperature coefficient of resistance in a low resistance region and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, with the miniaturization of various electronic devices, the demand for surface-mounted components has been increasing in order to reduce the mounting area of various electronic components. Among them, there is an increasing demand for high precision as a substitute for the conventional semi-fixed volume for the rectangular chip resistor.

The conventional rectangular chip resistors will be described below.
This will be described with reference to the drawings. FIG. 4 is a sectional view of a conventional rectangular chip resistor. In the figure, reference numeral 1 is a substrate containing 96% alumina, and an upper surface electrode 2 and a lower surface electrode 3 are provided on the upper and lower sides of the substrate 1, respectively. Reference numeral 4 is a resistor provided so as to be electrically connected to the upper surface electrode 2 provided on each side of the substrate 1. A protective film 5 is provided so as to cover a part of the upper surface electrode 2 and the resistor 4. Reference numeral 6 denotes an end surface electrode provided on the side end surface of the substrate 1 so as to electrically connect the upper surface electrode 2 and the lower surface electrode 3. Reference numeral 7 denotes a Ni plating film made of Ni provided so as to cover the end surface electrode 6. Reference numeral 8 is a solder plating film provided with a Ni plating film.

The manufacturing method of the rectangular chip resistor provided as described above will be described below.

First, a pair of upper surface electrodes 2 made of thick-film silver are formed on the side surface of the upper surface of the substrate 1 containing chip-shaped 96% alumina, and a thickness corresponding to the upper surface electrode 2 is formed on the back surface of the substrate 1. The silver-based back electrode 3 is formed.

Next, a resistor 4 made of a ruthenium oxide-based thick film glaze is formed on the substrate 1 so as to be electrically connected to the upper surface electrode 2 on the side of the substrate 1.

Next, in order to make the resistance value of the resistor 4 equal to a predetermined resistance value, the resistance value is corrected by laser trimming.

Next, a protective film 5 made of lead borosilicate glass is formed to completely cover the resistor 4 after laser trimming correction. At this time, after forming a pattern by screen printing on the part excluding the laser trimming, 8
It is formed by baking at a high temperature of 50 ° C. or 600 ° C.

Next, a thick film silver-based end face electrode 6 for connecting the upper face electrode 2 and the back face electrode 3 is formed on the side end face of the alumina substrate 1. At this time, the end face electrode 6 is generally 600
It is formed by firing at a high temperature around ℃.

Finally, in order to ensure reliability during soldering, a Ni plating film 7 is formed by electroplating so as to cover the end surface electrodes 6, and then a solder plating film 8 is formed so as to cover the Ni plating film 7. And manufactured a rectangular chip resistor.

[0011]

However, in the above-described conventional structure and manufacturing method, the resistor 4 having a low resistance value of 1Ω or less is limited by the limit of the specific resistance in the thick film glaze material containing ruthenium oxide as a main component. Since it cannot be formed, a resistor material to which a metal powder such as Ag or Pd is added is used. With a resistor material composed only of ruthenium oxide, the resistance temperature characteristic (hereinafter abbreviated as TCR) can be controlled by TCR adjustment. Agent (mainly metal oxide)
It is possible to achieve about ± 50 ppm / ° C. by adding Al, but in the resistance value region of 1Ω or less, the content of Ag or Pd in the resistor material composition is high. Control becomes impossible, and the TCR value is metal powder (Ag or Pd)
It is inevitable that the temperature will be +600 to 1000 ppm / ° C, which is a property of itself, and a low resistance value can be formed, but T
There is a problem that it is not possible to manufacture a highly accurate rectangular chip resistor having a small CR.

[0012]

In order to solve the above-mentioned problems, the present invention comprises a substrate having a resistive film on the upper surface with an underlying layer interposed between the substrate and the resistive film on the upper surface of the substrate. The protective film, the end face electrodes electrically connected to the resistance film on both end faces of the substrate, and the plating film provided so as to cover the end face electrodes are provided.

Further, an activation treatment is performed on the upper surface of the substrate to form an underlayer, and Cu and Ni are alternately laminated on the upper surface of the underlayer and heated to alloy to form a resistance film. A protective film is formed on the substrate, and a paste containing Ag or Cu containing a resin is printed and cured on both end surfaces of the substrate to form an end surface electrode, and a plating film is formed to cover the end surface electrode. And a method for manufacturing a rectangular chip resistor.

[0014]

With the above structure, since the resistance film is formed by using the Cu-Ni alloy, the TCR can be controlled by changing the ratio of Cu-Ni. Therefore, even if the resistance value is 1Ω or less, the TC: Ni ratio is adjusted to 65-55: 35-45 to obtain TC.
It is possible to realize a rectangular chip resistor capable of achieving R within ± 100 ppm / ° C.

Further, since the end face electrode layer is formed of the Ag-based or Cu-based conductive resin material having an excellent electric conductivity, there is almost no change in the resistance value due to the end face electrode material and it is not necessary to perform high temperature firing. Therefore, deterioration of characteristics due to high temperature can be prevented, and resistance drift and TCR can be prevented.
Can be suppressed.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A rectangular chip resistor according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a rectangular chip resistor according to an embodiment of the present invention. In FIG. 1, reference numeral 11 denotes a substrate, which preferably contains 96% alumina.
A base layer 12 is provided on the upper surface of the substrate 11. Thirteen
Is a resistance film provided on the upper surface of the underlayer 12, and is preferably made of a Cu—Ni alloy. 14 is a resistance film 13
Is a protective film provided on the upper surface of the. Reference numeral 15 denotes an end face electrode provided on both end faces of the substrate 11 and electrically connected to the resistance film 13, which preferably contains a resin. 1
Reference numeral 6 is a first plating film provided so as to cover the end face electrode 15, and preferably contains Ni.
Reference numeral 17 is a second plating film which is provided so as to cover the first plating film 16 and contact the protective film 14.

The method of manufacturing the rectangular chip resistor having the above structure will be described below with reference to the drawings.

FIG. 2 is a process chart showing a method of manufacturing a rectangular chip resistor according to an embodiment of the present invention.

First, a substrate 11 containing 96% alumina is received, and Cu--
In order to roughen the surfaces of the Ni alloy resistance film 13 and the substrate 11 and improve the adhesion by the anchor effect, an etching treatment with a hydrofluoric acid-based aqueous solution is performed to form the Cu—Ni alloy resistance film underlayer 12. Electrolytic Ni plating is performed.
At this time, in the pretreatment of the electroless Ni plating, sensitizing and activating are alternately performed a plurality of times.
Activated.

Next, Cu plating and Ni plating are alternately repeated a plurality of times on the Cu-Ni alloy resistance film underlayer 12 by electrolytic plating to form a Cu-Ni multilayer plating layer. At this time, Ni plating must be performed after Cu plating,
Also, the outermost layer is always manufactured by Ni plating. Cu
As for the film thickness of the plated film and the Ni plated film, the ratio of Cu and Ni of the alloy resistance film subjected to the high temperature treatment in the subsequent step is 65 to 5
5: 35-45 plating conditions (plating time,
The plating current, the number of times of plating, etc.) were set. This is shown in Figure 3.
As shown in the relationship diagram between the ratio of Cu-Ni alloy and properties of
This is because if the ratio of Cu and Ni deviates from the range of 65 to 55:35 to 45, the TCR cannot be controlled within ± 100 ppm / ° C.

Next, the multi-layer plating layer is subjected to a high temperature treatment to obtain C
The Cu-Ni alloy resistance film 13 is formed by alloying the u-Ni layered plating film. At this time, in the high temperature treatment, the material is left in a heat treatment furnace set at 800 ° C. for 2 hours and green gas (nitrogen gas containing 10% hydrogen) is supplied to prevent oxidation of the resistance film.

Next, the resistance value of the Cu-Ni alloy resistance film 13 is corrected by laser trimming so as to obtain a target resistance value. Through this process, the desired resistance value and T
It is indispensable that the Cu-Ni alloy resistance film 13 having CR is formed, and that there is no high temperature step that affects the resistance characteristics in the subsequent steps. That is, the following steps are low-temperature process construction methods.

Next, an epoxy resin paste having excellent resistance to moisture and heat is screen-printed so as not to be exposed except for a part of the resistance-modified Cu-Ni alloy resistance film 13, and the temperature is set to 200 ° C. 30 in a BOX dryer in the atmosphere
The film is dried and cured for a minute to form the protective film 14.

Next, a conductive resin is used to form the resin end face electrodes 15 that surround both end portions of the substrate 11 in a substantially U shape and are connected to the exposed portions of the Cu-Ni alloy resistance film 13. Apply Ag paste with roller applicator,
Dry and cure for 30 minutes in a BOX dryer at 0 ° C. The end surface electrode 15 may be made of another resin material such as Cu or the like as long as it is a resin material having an excellent electric conductivity, and carbon or the like can be used.

Finally, in order to secure the reliability of the exposed end surface electrode 15 at the time of soldering, Ni plating is performed by electrolytic plating.
The plating film 16 and the solder plating film 17 are formed to obtain the rectangular chip resistor according to the present invention.

It was confirmed that the rectangular chip resistor manufactured as described above is a highly accurate product having a resistance value of about 20 mΩ to 200 mΩ and a TCR of about +30 ppm / ° C. .

In the rectangular chip resistor of this embodiment, the manufacturing process has been described with the individual chip resistors, but in general, in order to improve mass productivity, a plurality of chips should be manufactured simultaneously. A sheet-shaped alumina substrate in which a plurality of dividing slits are formed in the vertical and horizontal directions is used. Therefore, as a pre-process of forming the end-face electrodes, a primary dividing process for exposing the end-face portion and a secondary dividing process for forming individual chip resistors after forming the end-face electrodes are added.

Although the Cu-Ni plating film was formed by electrolytic plating, the plating film can be formed by electroless plating as well. However, since the plating film grows slowly, electrolytic plating is more advantageous in terms of productivity. Also,
The Cu-Ni plating film of the present embodiment is Cu plating and N
Although the i-plating is formed by a multilayer plating layer which is alternately repeated a plurality of times, it may be formed by a single layer by electrolytic Cu-Ni alloy plating.

[0030]

As is apparent from the above description, according to the manufacturing method of the present invention, the resistance film is formed of the alloy of Cu-Ni, so that the resistance value is 1Ω or less and the TCR is ± 50. It is possible to provide a rectangular chip resistor having ˜100 ppm / ° C.

Further, by using a conventional thick film chip resistor production facility such as a screen printer, an end face coater, a baking furnace, and a plating facility, it is possible to manufacture a product with high mass productivity at low cost. It is possible.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a rectangular chip resistor according to an embodiment of the present invention.

FIG. 2 is a process drawing showing the same manufacturing method.

FIG. 3 is a diagram showing a relationship between a Cu—Ni alloy ratio and properties.

FIG. 4 is a cross-sectional view of a conventional rectangular chip resistor.

[Explanation of symbols]

 11 Substrate 12 Underlayer 13 Cu-Ni alloy resistance film 14 Protective film 15 End face electrode 16 First plating film 17 Second plating film

Claims (4)

[Claims] 1. A substrate having a resistive film on an upper surface thereof with a base layer interposed therebetween, a protective film provided on the resistive film on the upper surface of the substrate, and the resistive film and the electrical conductive film on both side end surfaces of the substrate. Rectangular chip resistor comprising an end face electrode that is electrically connected and a plating film that is provided so as to cover the end face electrode. 2. The rectangular chip resistor according to claim 1, wherein the resistance film is a Cu—Ni alloy and the content ratio thereof is Cu: Ni = 65 to 55:35 to 45. 3. The rectangular chip resistor according to claim 1, wherein the end face electrode contains an Ag-based or Cu-based resin material. 4. A resistance film is formed by performing activation treatment on the upper surface of a substrate to form a base layer, and alternately stacking Cu and Ni on the upper surface of the base layer and heating them to alloy them to form a resistance film. A protective film is formed on the substrate, and a paste containing Ag or Cu containing a resin is printed and cured on both end surfaces of the substrate to form an end surface electrode, and a plating film is formed to cover the end surface electrode. Of manufacturing rectangular chip resistor.