JPH11265801A - Chip resistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chip resistor in which the reliability of soldering is high, and to obtain a sufficient fixing force, even when the chip resistor is small. SOLUTION: A pair of electrodes 6 and 6 are formed at the both edge parts of the substrate surface of an insulating ceramic substrate 2. A resistor 3 is printed and formed on the substrate surface so as to be connected with the pair of electrodes 6 and 6. A glass coat 1 is formed so that the resistor 3 can be covered. A third electrode 8 is formed of Ag-resin based conductive paste obtained by mixing Ag into xylene phenol resin or epoxy phenol resin.

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 the substrate.

[0002]

2. Description of the Related Art The basic structure of a chip resistor is such that a pair of electrodes are formed at both ends of the surface of an insulating ceramic substrate, and a resistor is formed by printing on the surface of the substrate so as to be connected to the pair of electrodes. Structure. Conventionally, various electrode structures have been proposed for use in soldering to a circuit board. Further, in order to perform laser trimming of the resistor, glass coating is performed on the surface of the resistor. Further, a chip resistor having a structure in which a glass coat (upper glass coat) is further provided on the above-mentioned glass coat (lower glass coat) after trimming is completed has been proposed.

[0003]

In a conventional chip resistor, a bending force is applied particularly to a circuit board on which the chip resistor is mounted, so that the electrode of the chip resistor soldered to the electrode of the circuit board is forcibly applied. When an excessive force is applied, a pair of electrodes provided at both ends of the substrate may be cracked or a connection failure may occur, and there is a problem that reliability is lowered.

An object of the present invention is to provide a chip resistor having high reliability of soldering.

[0005]

According to the present invention, a pair of electrodes are formed at both ends of a surface of an insulating ceramic substrate,
A chip resistor in which a resistor is printed and formed on a substrate surface so as to be connected to a pair of electrodes and a glass coat is provided so as to cover the resistor is targeted for improvement.

In the present invention, the pair of electrodes is a pair of first electrodes of a metal glaze formed on both ends of the substrate surface of the insulating ceramic substrate, and the first electrodes are formed on both ends of the back surface of the insulating ceramic substrate. A pair of metal glaze-based second electrodes formed so as to face the electrodes were provided, and further formed of a conductive paste so as to cover the end surfaces of the insulating ceramic substrate and connect the first electrodes and the second electrodes. A pair of third electrodes may be provided, and a plating layer may be formed to cover the first, second, and third electrodes. Then, the third electrode is formed so that both ends thereof partially overlap the surfaces of the first electrode and the second electrode, respectively.

[0007] Covering the first, second, and third electrodes provided on the front, back, and end surfaces of both ends of the insulating substrate with Ni plating can prevent solder cracking. The solder wettability of the Ni plating layer can be improved.

The third electrode is disposed on the surface of the second electrode such that a gap is formed between the circuit board and the second electrode when the third electrode is disposed on the circuit board for mounting so that molten solder enters. Since the third electrode is partially overlapped with the second electrode on the lower surface side of the substrate, the electrodes are formed in a step shape, and the chip resistor of the present invention is mounted on a printed circuit board for mounting. When mounted on a circuit board, the molten solder wraps around the gap formed between the lower surface of the second electrode and the circuit board, and a sufficient fixing force can be obtained even if the chip resistor of the present invention is small.

Particularly, in the present invention, the third electrode is formed of an Ag-resin-based conductive paste in which Ag is mixed in a phenolic resin such as a xylene phenol resin or an epoxy phenol resin. When the third electrode is formed with such a conductive paste, the Ag-resin-based third electrode provided on the end face of the substrate has appropriate flexibility and sufficiently withstands bending of the circuit board. be able to.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One 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 convex resistor 3 on a surface of a ceramic substrate 2.
Are printed, and electrodes 4 are provided at both ends. The 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 sand blast to trim the resistance value.

The electrode 4 of the chip resistor 1 is connected to the resistor 3
Has a first electrode 6 directly connected thereto, and a second electrode 7 formed so as to face the first electrode 6 with the substrate 2 interposed therebetween. 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 obtained by mixing Ag in a xylene phenol resin or an epoxy phenol resin is provided on an 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, thereby achieving conduction between them. And the first, second, third
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 a metal glaze paste serving as the first electrode 6 are printed at predetermined intervals across a slit 14 of a ceramic plate 13 serving as a substrate.
Bake at a temperature close to 00 ° C. Further, similarly, the second electrode 7 is formed at a position facing the first electrode 6. Next, FIG.
As shown in B, the resistors 3 are printed and formed in a matrix on the ceramic plate 13 between the first electrodes 6, and the average is 850 ° C.
Firing at a temperature of Then, as shown in FIG. 3C, a glass coat 11 is applied to the surface of the resistor 3 and fired at an average temperature of 650 ° C. Thereafter, the ceramic plate 13 is cut (scribed) along slits 14 provided vertically and horizontally for each chip resistor, and an Ag-resin-based conductive paste is applied to the end surface of the substrate 2 as shown in FIG. 3D. The third electrode 8 is set to 20
It is applied to a thickness of about μ and cured at a temperature of about 200 ° C. Then, as shown in FIGS.
Solder plating 10 is sequentially applied to cover the first, second, and third electrodes 6, 7, and 8, respectively.

In this case, since the slits 14 are provided from both sides of the substrate, when the resin is applied to the end surface of the ceramic substrate in a state of being partially overlapped, a good electrical and mechanical state can be obtained.

According to this method, defects such as peeling of terminal electrodes and cracks do not occur on the end faces of the ceramic substrate.

Finally, the resistor 3 of each chip resistor is trimmed to adjust the resistance, and a resin coat 12 such as an epoxy resin is applied and cured at a temperature of about 200.degree.

The trimming may be performed in the state shown in FIG. 3C. In this case, the resin coating 12 is applied thereafter, and the steps shown in FIG. 3D and thereafter are performed. Thus, the resistance value is trimmed without separating the ceramic plate 13 for each chip, so that the trimming work can be performed efficiently, and the resin coat 12 has an adverse effect on the resistor even in the subsequent plating work. Nor.

According to the chip resistor of this embodiment, the resistance of the electrode 4 to solder cracking is improved, and the bending of the circuit board is more flexible than that of the metal glaze electrode alone. The electrode is strong because of high performance. In addition, the fixing force to the circuit board during soldering is extremely strong because the first and second electrodes 6 and 7 are firmly soldered to the circuit board, and the third electrode is made of an Ag-resin system. There is no reduction in the fixing force.

The resistor of the chip resistor according to the present invention can be appropriately selected according to its use, such as a metal film resistor and a carbon film resistor. The components of the metal glaze paste and the Ag-resin-based conductive paste may contain other additives as appropriate. In the present application, the resistor is coated with a glass coat and trimmed, but can be appropriately changed by a known method, and can be similarly applied to a chip component using another resistor. It is not limited to one.

In the chip resistor of this embodiment, an Ag-resin-based third electrode is provided on the end face of the substrate over the metal glaze-based first and second electrodes provided on both surfaces of the substrate. Since the Ni plating layer covering the second and third electrodes and the solder plating layer covering the Ni plating layers are formed, the Ni plating layer is resistant to solder cracking and can be re-attached to the circuit board. Also, since the third electrode is provided so as to partially overlap the second electrode on the lower surface side of the substrate, a step is formed by the electrode on the lower surface side of the substrate. The solder goes around into the gap between them, and a strong fixing force is obtained. In addition, since the Ag-resin-based third electrode provided on the end face of the substrate has appropriate flexibility, it can sufficiently withstand the bending of the circuit board. Further, as in the present embodiment, a resin-containing silver paint is directly applied to the end face of the substrate after scribing in a state of being partially overlapped on the first and second electrodes on the front and back surfaces, and is subjected to a heat treatment at a low temperature. When the electrodes are formed, the third electrodes are directly bonded to the rough substrate cross section as they are cut, and the third electrode has a strong adhesive force. When plating the soldering electrodes,
The electrode effectively prevents the plating solution from penetrating, and a high-quality product can be manufactured without causing defects such as peeling and cracks in the electrode. If a resin coat is applied before plating, a resistor that is weak to a plating solution is protected by the resin coat, so that the characteristics of the resistor can be maintained.

Accordingly, chip resistors have been miniaturized in response to today's demand for higher packing density. However, even if the electrodes are small, sufficient fixing force can be obtained, and miniaturization and weight reduction, reliability and durability of electric products can be obtained. And it greatly contributes to improvement of productivity.

[0023]

According to the present invention, the third electrode is positioned on the mounting circuit board so that a gap is formed between the circuit board and the second electrode so that a molten solder enters the third electrode. Since the solder is partially overlapped on the surface of the two electrodes, the molten solder also wraps around this gap, and a sufficient fixing force can be obtained even with a small chip resistor.

Further, since the Ag-resin-based third electrode in which Ag is mixed into the phenolic resin provided on the end face of the substrate has a moderate flexibility, the circuit board on which the chip resistor is mounted can be bent. Has the advantage that the reliability can be increased.

[Brief description of the drawings]

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

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

FIGS. 3A, 3B, 3C, 3D, 3F, and 3F are cross-sectional views showing the steps of manufacturing the chip resistor of this embodiment.

DESCRIPTION OF SYMBOLS 1 Chip resistor 2 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

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yozo Ohara 3158 Shimookubo, Osawano-cho, Kamishinkawa-gun, Toyama Prefecture Hokuriku Electric Industry Co., Ltd.

Claims (1)

[Claims] 1. A pair of electrodes are formed at both ends of a substrate surface of an insulating ceramic substrate, and a resistor is printed and formed on the substrate surface so as to be connected to the pair of electrodes, and covers the resistor. A chip resistor coated with glass as described above, wherein the pair of electrodes comprises a metal glaze-based first electrode, and opposite ends of the insulating ceramic substrate are opposed to the first electrode at both ends on the back surface of the substrate. A pair of second electrodes of a metal glaze type formed so as to cover the end surface of the insulating ceramic substrate and formed of a conductive paste so as to connect the first electrode and the second electrode. A pair of third electrodes, a plating layer is formed to cover the first electrode, the second electrode, and the third electrode, and both ends of the third electrode are the first electrode, respectively. And the third electrode is formed so as to partially overlap the surface of the second electrode, and the third electrode is disposed between the circuit board and the second electrode while being arranged on a circuit board for mounting. The third electrode partially overlaps the surface of the second electrode so as to form a gap into which solder enters, and the third electrode is made of Ag mixed with phenolic resin.
-A chip resistor formed of a resin-based conductive paste.