JP2002299102A - Chip resistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chip resistor that is not mounted defectively, even if the resistor is mounted in bulk, and can obtain good characteristics as a resistor. SOLUTION: This chip resistor is provided with a glass layer 31 baked at a high temperature on the surface of an insulating substrate 11, a pair of projecting sections 33 and 33 separately arranged on the layer 31, and a pair of electrodes 13 and 13 arranged on the sections 33 and 33. The resistor is also provided with a resistor 15 connected to the electrodes 13 and 13 and is arranged between the projecting sections 33 and 33, protective films 17 and 19 covering the resistor 15 and arranged between the sections 33 and 33, and plated electrodes 23 and 23, arranged at least on the electrodes 13 and 13. The surfaces of the plated electrodes 23 and 23 are made higher than those of the protective films 17 and 19.

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 a chip resistor suitable for so-called bulk mounting, in which a chip cassette is mounted on a circuit board from a bulk cassette containing a large number of chip components. is there.

[0002]

2. Description of the Related Art FIG. 4A shows an example of the structure of a conventional thick film chip resistor. The conventional chip resistor includes thick film electrodes 13 at both ends of an insulating substrate 11 made of alumina or the like, and a thick film resistor 15 is arranged between the electrodes. The resistor 15 is covered and protected by the glass insulating film 17 and the resin protective film 19. Plating electrodes 23 are formed on the upper surface and side end surfaces of the front electrode 13 and the rear electrode 21 which are both ends of the insulating substrate 11.

In this case, the height of the protective film 19 at the center of the substrate is higher than the height of the electrode portion 23. In many cases, a step on the surface of the plating electrode 23 on the surface side of the insulating substrate 11 and the surface of the protective film 19 are generated at about 30-50 μm.

[0004] By the way, conventional chip resistors are often shipped one by one on a tape at the time of shipment from the factory in a so-called taping package in which the surface on which the resistor exists is fixed as the surface. And when mounting on a circuit board,
It was fixed to the circuit board by a mounting machine (mounter) as it was, that is, with the surface on which the protective film is present as the surface. In this case, as shown in FIG.
The electrode 2 on the back surface side of the insulating substrate 11 is
The back surfaces of the substrates 3 and 23 are in close contact with each other, and are fixed by solder reflow or the like.

However, as a mounting method, there is a bulk mounting using a bulk mounting machine in which a large number of chip components are stored in a bulk cassette as they are, and the chip components are taken out of the bulk cassette one by one and mounted on a circuit board. . When the conventional chip resistor shown in FIG. 4 is bulk-mounted by a bulk mounting machine, as shown in FIG.
A case where the chip resistor is mounted in the opposite direction so that the surface side (protective film side) of the chip resistor is in contact with the circuit board 25 occurs with a probability of about 50%. At this time, there is a strong possibility that the chip resistor is mounted inclined, and in the worst case, there is a problem that one side cannot be soldered or a phenomenon such as chip standing occurs. Therefore, there is a problem that the conventional chip resistor cannot cope with so-called bulk mounting.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a chip resistor which does not cause mounting failure even in bulk mounting and has good characteristics as a resistor. The purpose is to do.

[0007]

In order to solve the problems in the prior art, one embodiment of the present invention includes a glass layer fired at a high temperature on a surface of an insulating substrate, and the glass layer is provided with a glass layer. A pair of convex portions disposed apart from each other, a pair of electrodes disposed on the convex portions, a resistor connected to the electrodes and disposed between the pair of convex portions, A protective film disposed between the pair of convex portions covering the resistor,
A chip electrode comprising at least a plated electrode disposed on the pair of electrodes, wherein the height of the surface of the plated electrode is higher than the height of the surface of the protective film.

It is preferable that a back surface electrode is disposed on a back surface of the insulating substrate and an end surface electrode is disposed on a side end surface, and the convex portion is a glass layer fired at a high temperature. .

Further, according to a method of manufacturing a chip resistor of the present invention, a glass layer is formed on a surface of an insulating substrate by firing at a high temperature, and a pair of convex portions are formed on the glass layer. An electrode is arranged on the upper portion and the back surface of the insulating substrate, a resistor is connected to the electrode in a concave portion between the convex portions, and a protective film covering the resistor is provided between the convex portions. It is characterized in that it is formed in a concave portion, and plating electrodes are formed on both ends of the substrate by plating so as to be higher than the height of the protective film.

According to the above-described chip resistor of the present invention,
By providing a convex portion on the surface of the insulating substrate in advance and raising the height, the plating electrode can be formed higher than the height of the protective film, and the stand-off can be secured also on the protective film surface. Therefore, even if mounting is performed using a mounting machine that supports bulk mounting, the chip resistor can be mounted on the circuit board with a 100% probability. In addition, by forming an insulating layer on the surface of the insulating substrate in advance, the smoothness of the substrate surface is ensured, and the variation in characteristics due to the influence of unevenness on the substrate surface can be extremely reduced. Therefore, highly accurate chip resistors can be produced with high yield.

By providing a raised portion on the surface of the insulating substrate and raising the height, the plated electrode can be formed higher than the height of the protective film. Response is possible.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a chip resistor according to the present invention will be described below in detail with reference to FIGS. FIG. 1 is a diagram illustrating an overall configuration of a chip resistor according to an embodiment of the present invention.

This chip resistor is provided with a glass layer 31 of uniform thickness formed on a surface of an insulating substrate 11 made of alumina or the like by firing at a high temperature, and furthermore, a pair of glass layers disposed at both ends of the insulating substrate. Similarly, a projection 33 made of a glass layer formed by firing at a high temperature is provided. Glass layer 31,
The firing temperature of 33 is preferably about 1000 to 1300 ° C. Here, the glass layer 31 is preferably formed to have a thickness of about 1-5 μm, and the convex portion 33 is formed to have a thickness of 20-50 μm.
Preferably, it is formed to about m.

The electrodes 13, 13 are arranged on the convex portions 33, 33, and the resistor 15 is arranged between the electrodes 13, 13. The resistor 15 is formed by screen printing and baking of a thick film paste such as ruthenium oxide and has a thickness of 10−
Preferably, it is formed to a thickness of about 15 μm. The resistor 15 is disposed in a concave portion between the pair of convex portions 33, 33, and the electrode 1
3, 13 are connected.

The resistor 15 is covered and protected by a glass insulating film 17 and a resin protective film 19. The glass insulating film 17 and the resin protective film 19 are formed of a pair of convex portions 33, 33.
It is arranged in a concave portion between them. The glass insulating film 17 has a thickness of 1
The thickness is preferably about 5 to 20 μm, and the thickness of the resin protective film 19 is preferably about 20 μm.

On the side end surface of the insulating substrate 11, an end surface electrode formed by sputtering of nickel chromium (Ni-Cr) or the like is formed. A plating electrode 23 formed by plating is arranged on the electrode 13 on the front surface side of the substrate, the electrode 21 on the rear surface side, and the end surface electrode on the end surface on the substrate side. The plating electrode 23 is composed of a nickel plating layer and a solder or tin plating layer. The nickel plating layer is preferably formed to a thickness of about 3-10 μm, and the solder or tin plating layer is preferably formed to a thickness of about 5-15 μm.

Accordingly, a structure is obtained in which the plating electrodes 23, 23 are raised by the pair of convex portions 33, 33, and the protective films 17, 19 are disposed in the concave portions therebetween. That is, the height of the surface of the plating electrode 23 is higher than the height of the surface of the protective film 19. 2A and 2B show a state in which the chip resistor is mounted on a circuit board. FIG. 2A shows a state where the protective film side of the chip resistor faces upward, and FIG. 2B shows a state where the protective film side of the chip resistor faces the circuit board. Respectively (in the opposite direction).

In the chip resistor having the above-described structure, since the electrode 23 protruding from the surface of the protective film 19 of the chip resistor is formed, the chip resistor is turned upside down as shown in FIG. Even if the chip resistor is mounted, the inclination of the chip resistor can be suppressed, whereby the chip resistor can be reliably mounted on the circuit board. For this reason, even if the chip resistor is mounted from the bulk cassette by the bulk mounting machine and mounted so that the front side (protective film side) of the chip resistor faces the circuit board (in the opposite direction), the chip resistor can be fixed by soldering without any problem. It is possible.

Further, an insulating layer (glass coat) 31 is formed on the surface of the insulating substrate 11 in advance, so that the smoothness of the substrate surface is improved. As a result, variations in the resistance value caused by unevenness on the substrate surface and the temperature coefficient of resistance (TC
R) can be made very small.
In addition, the presence of the glass layer 31 improves the adhesion of the resistor 15 and improves the accuracy and reliability of the electrical characteristics of the product.

Next, a method of manufacturing a chip resistor according to the present invention will be described with reference to FIG. First, as shown in (a), an insulating substrate 11 of alumina or the like is prepared.
Although one chip area is shown in the illustrated example, a multi-chip substrate for manufacturing a large number of chip resistors at once is used.

Next, as shown in FIG.
An insulating layer (glass layer) 31 is formed on screen 1 by screen printing and firing. The firing of the glass layer at this time is 100
This is performed at a high temperature of about 0 ° C. to 1300 ° C. This glass layer 31
Plays an important role in improving the adhesion between the upper and lower layers and providing a smooth surface to the resistor formed thereon. Then, a pair of convex patterns are formed on both sides of the substrate by screen printing on the insulating layer 31,
The protruding portion 33 is formed by baking. This convex part 3
Reference numeral 3 also denotes a glass layer, which is preferably formed by firing at a high temperature of 1000C to 1300C. This convex portion 33
Also play an important role in raising the electrodes formed thereon.

Next, as shown in FIG. 3C, the electrode 13 is formed on the convex portion 33. This electrode 13 is made of Ag or Ag-
Forming a Pd paste pattern by screen printing,
For example, it is formed by firing at a temperature of about 850 ° C.
The electrode 13 is formed so as to extend around a concave portion formed between a pair of convex portions. Similarly, the back electrode 21 is formed by arranging an Ag or Ag-Pd paste pattern by screen printing and firing. Either the front-side electrode 13 or the rear-side electrode 21 may be formed first.

Next, as shown in FIG.
The resistor 15 is formed between the three by screen printing and firing. As the resistor, it is preferable to use ruthenium oxide or the like. For example, firing is performed at a temperature of about 850 ° C. The resistor 15 is formed in a concave portion formed between a pair of convex portions.
Laser resistance is applied to the resistor 15 as necessary to adjust the resistance value.

Next, as shown in (e), a first protective layer pattern is formed on the resistor pattern 15 by screen printing, and baked. The first protective layer 17 is a glass layer,
It is preferable to fire at a temperature of about 00 ° C. Next, the second protective layer 19 is formed by screen printing and heat curing. The second protective layer 19 is an epoxy resin,
It is preferable to heat and cure at a temperature of about 0 ° C. The first protective layer 17 and the second protective layer 19 are formed of a pair of convex portions 33 and 3.
It is arranged in a recess formed between the three.

The above process is a batch process of a multi-piece substrate, and then a process of dividing into strips is performed. The processing may be either dicing or break. Next, an end face electrode is formed on the end face on the substrate side. The end electrode forms a Ni / Cr layer by, for example, sputtering. Then, a process of dividing into single chips is performed. Processing may be dicing or break. Next, as shown in (f), electrolytic plating is performed to form plated electrodes 23,23. To prevent electrode cracking and improve the reliability of soldering, Ni plating layer and Sn-Pb plating layer (S
(a n-plated layer may be used).

As a result, the electrodes at both ends of the insulating substrate are raised, and a stand-off is generated at the central protective film, thereby completing a chip resistor suitable for bulk mounting. This chip resistor is not only suitable for bulk mounting, but also has a glass layer fired at a high temperature on the surface of the insulating substrate, so that good electrical characteristics can be obtained due to the effect of the smooth surface.

In the above embodiment, an example has been described in which electrodes are provided on the front and back surfaces of the insulating substrate, and the chip resistor can be mounted face up or reverse. It is also applicable to so-called filletless mounting in which mounting is performed in the opposite direction. That is, by providing a convex portion on the surface of the insulating substrate and raising the height in advance, the plating electrode can be formed to be higher than the height of the protective film, and the stand-off can be secured also on the protective film surface.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and it goes without saying that the present invention may be embodied in various forms within the scope of the technical idea.

[0029]

As described above, according to the present invention, since the electrode raised above the surface of the protective film of the chip resistor is formed, even if the chip resistor is mounted face down, it is ensured. This allows soldering to a printed circuit board. Thereby, a chip resistor suitable for bulk mounting can be provided. In addition, by forming an insulating layer (glass layer) for the purpose of surface smoothness on the substrate surface in advance, variations in characteristics conventionally affected by unevenness of the substrate surface can be suppressed to a small level. -By improving the adhesion of the resistor layer, a highly reliable and highly accurate resistor can be provided.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a mounting state of the chip resistor.
(A) shows a state in which the chip resistor is mounted with the protective film side facing upward, and (b) shows a state in which the protective film is mounted face down with the protective film side facing the circuit board.

FIG. 3 is a view showing a manufacturing process of the chip resistor.

4A is a cross-sectional view showing the entire configuration of a conventional chip resistor, FIG. 4B is mounted with the protective film side facing the front side, and FIG. 4C is mounted with the protective film side facing the circuit board; It is a figure which shows the state respectively mounted.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Insulating substrate 13, 21 Electrode 15 Resistor 17, 19 Protective film 23 Plating electrode 31 Glass layer 33 Convex part (glass layer)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5E028 BA11 BB01 CA02 EA01 EB05 JC03 JC05 JC12 5E032 BA15 BB01 CA02 CC14 CC16 TB02 5E033 AA03 BC01 BD01 BE02 BE04 BH02

Claims (4)

[Claims] An insulating substrate includes a glass layer fired at a high temperature on a surface thereof, a pair of convex portions arranged on the glass layer so as to be separated from each other, and a pair of convex portions disposed on the convex portion. An electrode, a resistor connected to the electrode and disposed between the pair of protrusions, a protective film disposed between the pair of protrusions covering the resistor, and at least the pair of electrodes; And a plating electrode disposed thereon, wherein the height of the surface of the plating electrode is higher than the height of the surface of the protective film. 2. The chip resistor according to claim 1, wherein a back surface electrode is arranged on a back surface of the insulating substrate, and an end surface electrode is arranged on a side end surface. 3. The chip resistor according to claim 1, wherein the convex portion is a glass layer fired at a high temperature. 4. A glass layer is formed on the surface of the insulating substrate by firing at a high temperature, a pair of convex portions are formed on the glass layer, and electrodes are provided on the convex portions and on the back surface of the insulating substrate. And a resistor is connected to the electrode in the concave portion between the convex portions, and a protective film covering the resistor is formed in the concave portion between the convex portions, and plating is performed on both ends of the substrate. Forming a plated electrode higher than the height of the protective film.