JPH07283004A - Chip resistor and fabrication thereof - Google Patents

Abstract

PURPOSE:To provide a chip resistor in which insufficient conduction is eliminated at an electrode formed on the split face of an insulating ceramic substrate. CONSTITUTION:First metal glaze electrodes 6 are printed on the surface of a ceramic substrate 13 provided with a plurality of splitting slits 14 on the opposite sides thereof. Similarly, second electrodes 7 are printed on the rear of the ceramic substrate 13. A resistor 3 to be connected with a pair of first electrodes is printed on the surface of the substrate 13 which is then scribed along each split 14. The scribed ceramic substrate is then applied directly on the opposite end parts, including the split face thereof, with a silver paint containing a resin in substantially C-shape while partially lapped over the first and second electrodes. It is then heat treated to form third electrodes 8 at the opposite end parts which are eventually covered with plating layers 9, 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip resistor in which a resistor is provided on the surface of a chip-shaped insulating ceramic substrate and electrodes are formed at both ends of this substrate, and a method for manufacturing the same.

[0002]

2. Description of the Related Art The basic structure of a chip resistor has a pair of electrodes formed on both ends of the surface of an insulating ceramic substrate, and a resistor is printed on the substrate surface so as to be connected to the pair of electrodes. It has a different structure. In order to improve solderability, a structure has also been proposed in which a side electrode and a back electrode are further provided on the side surface and the back surface of the insulating ceramic substrate.

[0003]

Since the insulating ceramic substrate is formed by dividing a large ceramic plate, the side electrodes are formed on the dividing surface of the insulating ceramic substrate. The angle between the front and back surfaces of the insulating ceramic substrate and the dividing surface (the end surface forming the side electrode) is an acute angle. Therefore, when the side electrode is formed by using the conductive paste, the conductive paste Occurs at the corners of the substrate. In particular, when a metal glaze-based conductive paste containing glass is used as the conductive paste, breakage of the conductive paste is high.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a chip resistor and a method for manufacturing the same, which does not cause defective conduction in the electrodes formed on the divided surfaces of the insulating ceramic substrate.

[0005]

In the chip resistor of the present invention, a ceramic plate 13 having a plurality of dividing slits 14 formed on both surfaces of the substrate so as to face each other in the thickness direction is formed along the slits. The insulating ceramic substrate 2 having the divided surfaces on both end surfaces is used. A pair of first electrodes 6 of metal glaze type are formed on both ends of the insulating ceramic substrate 2 which are located on both end sides of the substrate surface. A pair of second electrodes 7 of metal glaze type are formed on the back surface of the insulating ceramic substrate 2 at positions facing the pair of first electrodes 6. Then, a resistor that is directly connected to the pair of first electrodes is formed on the surface of the substrate. Further, a pair of substantially U-shaped Ag-resin-based third electrodes 8 are formed on both end surfaces of the insulating ceramic substrate 2 so as to partially overlap the first electrode and the second electrode. Further, a plating layer (9, 10) is formed so as to cover a part of the first electrode and the second electrode and the third electrode.

According to the method of the present invention, first, the plurality of slits 14 formed on the substrate surface of the ceramic plate 13 having the plurality of dividing slits 14 formed on the both surfaces of the substrate so as to face each other in the thickness direction, respectively. A metal glaze-based first electrode 6 is formed by printing on the surface of the substrate while sandwiching it. Further, the metal glaze-based second electrode 7 is formed by printing on the back surface of the substrate while sandwiching a plurality of slits 14 formed on the back surface of the substrate of the ceramic plate. Then, the resistor 3 which is directly connected to the pair of first electrodes formed between the two adjacent slits 14 is formed by printing on the surface of the substrate. The ceramic plate on which the first electrode, the second electrode and the resistor are printed is scribed along the slit 14 so that the first electrode and the second electrode are located at both ends. After that, the resin-containing silver paint is directly applied in a substantially U-shape on both end portions including the divided surface of the scribed ceramic plate so as to partially overlap with the first electrode and the second electrode, and then heat treatment is applied to both end portions. Forming a third electrode 8 on the
A plating layer (9, 9) is formed on the outer surfaces of the electrodes, the second electrode and the third electrode.
10) is formed.

[0007]

The ceramic plate 13 having a plurality of dividing slits 14 formed on both sides of the substrate so as to face each other in the thickness direction is formed on both end faces of the insulating ceramic substrate 2 formed by dividing the ceramic plate 13 along the slits 14. Two inclined surfaces for forming the two slits 14 facing each other in the thickness direction remain on the divided surface. Therefore, the angle between the front surface and the back surface of the substrate and these two inclined surfaces and the angle between the two inclined surfaces and the remaining divided surfaces are both obtuse angles. Therefore, when the third electrode 8 is formed on both end surfaces of the insulating ceramic substrate 2 with the conductive paste, the conductive paste is unlikely to break. However, when the third electrode is formed of a metal glaze-based conductive paste containing glass, the rate at which the conductive paste is cut at the corners of the substrate is still high. It is considered that this is due to the glass contained in the conductive paste. Therefore, in the present invention, a resin-containing silver paint is used as a conductive pace for forming the third electrode 8. The resin-containing silver paint has lower fluidity than a metal-glaze-based conductive paste containing glass, and almost never breaks when the corners formed on the substrate are obtuse.
Therefore, according to the present invention, the yield is significantly improved. The Ag-resin-based third electrode 8 provided on the end surface of the substrate is
Since it has appropriate flexibility, it can sufficiently withstand the bending of the circuit board and does not peel off. However, the curing temperature at the time of forming the Ag-resin type third electrode is significantly lower than the curing temperature at the time of forming the metal glaze type first electrode 6 and the second electrode 7, and the heat resistance is low. Therefore, solder erosion may occur. Further, silver migration may occur from the Ag-resin-based third electrode 8. Therefore, in the present invention, the first electrode, the second electrode, and the third electrode are covered with the plating layers (9, 10). This plated layer can prevent solder erosion and silver migration.

Since the third electrode is provided so as to partially overlap with the second electrode on the lower surface side of the substrate, the electrodes are formed in a step shape, and when the chip resistor of the present invention is attached to the printed circuit board, Solder wraps around the gap formed between the lower surface of the electrode and the circuit board, and a sufficient fixing force can be obtained even if the chip resistor of the present invention is small.

[0009]

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

As shown in FIG. 1, a chip resistor 1 of this embodiment has a ceramic substrate 2 and a convex resistor 3 on a surface thereof.
Is printed, and the electrodes 4 are provided on both ends thereof. As shown in FIG. 3, this ceramic substrate 2 divides along a slit a ceramic plate 13 having a plurality of dividing slits 14 formed on both surfaces of the substrate so as to face each other in the thickness direction. Therefore, in reality, the corners of both ends of the substrate 2 are not 90 degrees as shown in the drawing, and the substrate 2
Slopes forming the slits 14 remain at the corners of both ends of the. Therefore, the corners formed on both ends of the actual substrate 2 are obtuse angles larger than 90 degrees. In addition, the slit 14
The corners between the divided surface where the mark is not included and the inclined surface forming the slit 14 are also obtuse angles. Resistor 3
Is provided with a thickness of about 10 μm of ruthenium oxide, and a trimming groove 5 is formed upward from the bottom of the convex shape by laser or sandblasting to trim the resistance value.

The electrode 4 of the chip resistor 1 is a resistor 3
Has a first electrode 6 directly connected thereto and a second electrode 7 formed so as to face the first electrode 6 and the substrate 2, and the first and second electrodes 6 and 7 are Ag-Pd, Ag-P
It is formed by printing a metal glaze paste such as t. Further, a third electrode 8 made of an Ag-resin-based conductive paste in which Ag is mixed with xylene phenol resin or epoxy phenol resin is provided on the end surface of the substrate 2 with the first and second electrodes 6 and 7 interposed therebetween. The third electrode 8 is provided so as to partially cover the first and second electrodes 6 and 7 so as to establish electrical continuity between them. And this 1st, 2nd, 3rd
Ni plating 9 and solder plating 10 are applied to cover the entire electrode.

The surface of the resistor 3 is protected by a glass coat 11 and a resin coat 12.

The method of manufacturing the chip resistor of this embodiment is as follows.
As shown in FIGS. 3A to 3F, first, a plurality of rows of metal glaze paste to be the first electrodes 6 are printed at predetermined intervals across the slits 14 on the substrate surface side of the ceramic plate 13 to be the substrate, and the temperature is set to about 900 ° C. Bake at. In most cases, when the metal glaze paste is applied on the surface of the substrate, a part thereof flows into the slit 14. Further, similarly, the second electrode 7 is also formed at a position on the back surface of the substrate facing the first electrode 6. Next, as shown in FIG. 3B, the first electrode 6
The resistors 3 are printed and formed in a matrix on the ceramic plate 13 between them and fired at a temperature of 850 ° C. on average. And
As shown in FIG. 3C, a glass coat 1 is formed on the surface of the resistor 3.
1 and baked at an average temperature of 650 ° C. After that, the ceramic plate 13 is cut (scribed) along the slits 14 provided in the vertical and horizontal directions for each chip resistor, and as shown in FIG. 3D, the end face of the substrate 2 is coated with Ag-resin based conductive paste. 3 electrode 8 is applied to a thickness of about 20μ, 200 ℃
Cure at moderate temperature. Then, as shown in FIGS. 3E and 3F, Ni plating 9 and solder plating 10 are sequentially applied to cover the first, second, and third electrodes 6, 7, and 8.

In this case, since the slits 14 are provided so as to face each other in the thickness direction from both sides of the substrate, when the resin is applied to the end face of the ceramic substrate in a state of partially overlapping, both electrically and mechanically. A good condition is obtained.

According to this method, defects such as peeling and cracking of the terminal electrode, that is, the third electrode 8 do not occur on the end surface of the ceramic substrate.

Finally, the resistor 3 of each chip resistor is trimmed to adjust its resistance value, and a resin coat 12 of epoxy resin or the like is applied and cured at a temperature of about 200.degree.

Trimming may be performed in the state shown in FIG. 3C. In this case, the resin coat 12 is then applied and the steps shown in FIG. 3D and thereafter are performed. As a result, since the resistance value is trimmed without separating the ceramic plate 13 into chips, the trimming work can be performed efficiently, and the resin coat 12 adversely affects the resistor during the subsequent plating work. Nor.

According to the chip resistor of this embodiment, the resistance of the electrode 4 to the solder erosion is improved, and moreover, it is more flexible against the bending of the circuit board as compared with the electrode made of only the metal glaze type. The electrode is strong because it has high properties. In addition, the fixing force to the circuit board during soldering also depends on the first and second electrodes 6, 6.
Since 7 is firmly soldered to the circuit board, it is extremely strong, and the adhesion strength does not decrease due to the third electrode being made of Ag-resin.

The resistor of the chip resistor of the present invention is
A metal film resistor, a carbon film resistor or the like can be appropriately selected according to its application. In addition, the metal glaze paste and the Ag-resin-based conductive paste components may appropriately contain other additives. In the present application, a glass coat is applied on the resistor and trimming is performed, but it can be appropriately changed by a known method, and it can be similarly applied to a chip component using another resistor. It is not limited to one.

In the chip resistor of this embodiment, the Ag-resin based third electrode is provided on the end face of the substrate across the metal glaze based first and second electrodes provided on both sides of the substrate. Since the Ni plating layer that covers the second and third electrodes and the solder plating layer that covers the Ni plating layer are formed, they are resistant to solder erosion and can be reattached to the circuit board. Further, since the third electrode is provided so as to partially overlap the second electrode on the lower surface side of the board, a step is formed on the electrode on the lower surface side of the board, and when soldered to the circuit board, the lower surface electrode and the circuit board are separated. Solder wraps around the gap between them to obtain a strong fixing force. Moreover, since the Ag-resin-based third electrode provided on the end surface of the substrate has appropriate flexibility, it can sufficiently withstand bending of the circuit board. Further, as in this example, the resin-containing silver coating was applied to the end surface of the substrate side after scribing on the front and back surfaces.
When the third electrode is formed by directly applying it on the second electrode in a partially overlapped state and heat-treating it at a low temperature, the third electrode is directly bonded to the rough substrate cross section that has been cut, and the adhesive strength of the third electrode is strong.
Further, when the soldering electrode is plated, the third electrode can effectively prevent the plating solution from penetrating, and it is possible to manufacture a high-quality product that does not cause defects such as peeling and cracks on the electrode. If the resin coat is applied before plating, the resistor which is weak against the plating solution is protected by the resin coat, so that the characteristics of the resistor can be maintained.

Therefore, although the chip resistors have been miniaturized in response to today's demand for higher packaging density, sufficient fixing force can be obtained even with small electrodes, and the electrical products can be made compact, lightweight, reliable and durable. It also contributes greatly to the improvement of productivity.

[0022]

As in the present invention, an insulating ceramic substrate formed by dividing a ceramic substrate having a plurality of dividing slits formed on both sides of the substrate so as to face each other in the thickness direction along the slits is used. Since the corners formed on both ends of the substrate are obtuse, the conductive paste is less likely to break even when the third electrode is formed on the both ends of the insulating ceramic substrate with the conductive paste. Moreover, in particular, in the present invention, since the resin-containing silver paint having low fluidity is used as the conductive paste for forming the third electrode, the conductive paste is almost cut when the corners formed on the substrate are obtuse angles. There is no. Therefore, according to the present invention, there is an advantage that the yield is significantly improved. In addition, Ag provided on the end surface of the substrate
-Since the resin-based third electrode has appropriate flexibility,
It has an advantage that it can sufficiently withstand bending of the circuit board and does not peel off. Furthermore, silver migration may occur from the Ag-resin-based third electrode, and solder erosion may occur.
In the present invention, since the first electrode, the second electrode and the third electrode are covered with the plating layer, the plating layer has an advantage that solder erosion can be prevented and silver migration can be prevented.

[Brief description of drawings]

FIG. 1 is a plan view of an embodiment of a chip resistor of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

3A, 3B, 3C, 3D, 3E, 3F, 3E, 3F, 3E, 3F, 3E, 3F, 3E, 3F, 3E, 3F, 3E, 3F, 3F, 3F, 3F, 3F, 3F, 3F, 3F, 3F, 3F, 3F, 3F, 3F, 3F, 3D, 3F, 3D, and 3F are cross-sectional views showing a manufacturing process when manufacturing the chip resistor of the invention.

[Explanation of symbols]

 1 Chip Resistor 2 Insulating Ceramic Substrate 3 Resistor 4 Electrode 5 Trimming Groove 6 First Electrode 7 Second Electrode 8 Third Electrode 9 Ni Plating 10 Solder Plating 11 Glass Coat 12 Resin Coat 13 Ceramic Plate 14 Slit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yozo Ohara 3158 Shimookubo, Osawano-cho, Kamishinagawa-gun, Toyama Prefecture Hokuriku Electric Industry Co., Ltd.

Claims (2)

[Claims] 1. A ceramic plate (13) having a plurality of dividing slits (14) formed on both sides of a substrate so as to face each other in the thickness direction, is divided along the slits, and is formed on both end faces. Insulating Ceramic Substrate (2)
A pair of metal glaze-type first electrodes (6) formed at both ends of the insulating ceramic substrate (2) located on both end sides of the substrate surface of the insulating ceramic substrate (2); A pair of metal glaze type second electrodes (7) formed on the back surface of the substrate at a position facing the pair of first electrodes (6), and directly connected to the pair of first electrodes formed on the front surface of the substrate And a pair of substantially U-shaped Ag-resin system formed on both end surfaces of the insulating ceramic substrate (2) so as to partially overlap the first electrode and the second electrode. Third electrode (8)
And a part of the first and second electrodes and a plating layer (9, 10) covering the third electrode. 2. A plurality of said slits (14) formed on the substrate surface of a ceramic plate (13) having a plurality of dividing slits (14) formed on both sides of the substrate so as to face each other in the thickness direction. A step of printing and forming a metal glaze-type first electrode (6) on the front surface of the substrate while sandwiching the metal glaze on the back surface of the substrate by sandwiching the plurality of slits (14) formed on the back surface of the substrate of the ceramic substrate; A step of printing and forming a second electrode (7) of the system, and a resistor (3) directly connected to the pair of first electrodes formed between the two adjacent slits (14), the substrate surface And a step of forming the first electrode, the second electrode, and the resistor by printing so that the first electrode and the second electrode are located at both ends of the ceramic substrate. 14 Scribing along with, and directly applying resin-containing silver paint in a substantially U-shape in a state where it partially overlaps with the first electrode and the second electrode on both side ends including the divided surface of the scribed ceramic substrate. And then heat-treating to form third electrodes (8) on both side ends, and plating layers (9, 10) on outer surfaces of the first electrode, the second electrode and the third electrode. A method of manufacturing a chip resistor including the step of forming.