JP3110677B2 - Chip resistor - Google Patents

Description

Description: 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 on both ends of the substrate. It is about a vessel. 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 on the surface of the substrate so as to be connected to the pair of electrodes. It is a structure formed by printing. 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] Conventionally, as a material for further covering the lower glass coat, a glass coat having the same properties as the lower glass coat is best from the viewpoint of fixing.
A double glass coat was applied over the resistor. However, in a structure in which the upper glass coat is further applied on the lower glass coat, it is necessary to again expose the chip resistor to a high temperature (for example, 650 ° C.) when firing the upper glass coat. When the resistor is exposed to a high temperature, there arises a problem that the trimmed resistance value tends to change. When the upper glass coat is applied, when the trace of the laser trimming is deep or wide, the laser trimming may be performed in a state in which bubbles are taken in the trace, and cracks are easily generated in the upper glass coat. Also, even if glass is poured into the trace of trimming without leaving any bubbles, a step is easily formed inevitably, and there is a problem that the step is likely to cause cracking. Further, the glass coat is usually expensive and needs to be fired at a high temperature, so that there is a problem that a large amount of power is consumed, and the manufacturing cost cannot be reduced. Further, when a characteristic display or the like is printed on the glass coat, there is also a problem that the printability is poor and the display ink is hard to adhere. In a conventional chip resistor, a bending force is applied to a circuit board on which the chip resistor is mounted.
If excessive force is applied to the electrodes of the chip resistor soldered to the electrodes of the circuit board, cracks may occur in the pair of electrodes provided at both ends of the board and connection failures may occur, resulting in poor reliability. There was a problem of lowering. SUMMARY OF THE INVENTION An object of the present invention is to provide a highly reliable chip resistor with less variation in resistance value. Another object of the present invention is to provide a chip resistor having high reliability of soldering. According to the present invention, a pair of electrodes are formed at both ends of a substrate surface of an insulating ceramic substrate.
A resistor is printed and formed on the substrate surface so as to be connected to a pair of electrodes, and a glass chip is applied so as to cover the resistor. Apply resin coat. Since the curing temperature of the resin is about 200 ° C., even if the resin coat is applied on the glass coat, the trimming resistance value is not affected as compared with the conventional case where the glass coat is applied again. Almost no. Therefore, according to the present invention, it is possible to obtain a chip resistor having less variation in resistance value. When a resin coat is applied, the resistance value is hardly affected. Since the viscosity of the resin for forming the resin coat can be freely changed, even if the trace of laser trimming is deep or wide even if the trace of the laser trimming is wide, it is possible to make the resin smoothly There is no fear of getting in (as in FIG. 2) and taking in air bubbles. Also,
The resin is softer than glass and does not crack even if a slight level difference occurs. In addition, the resin coat can be formed thicker than the glass coat,
When the thickness of the resin coat is increased to some extent, there is no portion where the resin coat becomes extremely thin around the trace of trimming, and it is possible to prevent moisture and plating solution from entering. In addition, the resin coat has good printability of the display ink and can perform precise printing. Furthermore, since the step of forming the resin coat is a low-temperature baking step, the equipment is inexpensive, consumes little power, and can reduce the manufacturing cost. Therefore, according to the present invention, it is possible to obtain a chip resistor having a small change in resistance value and a small variation in resistance value, and a chip having little aging and excellent in moisture resistance, solvent resistance and plating solution resistance. Resistors can be obtained at low cost. Further, 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 pair of electrodes is 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 one electrode, and further covering the end surface of the insulating ceramic substrate, and connecting the first electrode and the second electrode;
The conductive paste applied to connect the electrodes cures
And a pair of third electrodes formed by the first and second electrodes.
A plating layer may be formed so as to cover the electrode and the third electrode. Then, the third electrode is formed so that both ends thereof partially overlap the surfaces of the first electrode and the second electrode, respectively. [0010] When the first, second and third electrodes provided on the front and back surfaces and the end surfaces at both ends of the insulating substrate are covered with Ni plating, solder cracking can be prevented. The solder wettability of the Ni plating layer can be improved. The third electrode partially overlaps the surface of the second electrode such that a gap is formed between the circuit board and the second electrode in a state where the third electrode is disposed on the circuit board for mounting. That is, since the third electrode is provided on the lower surface side of the substrate so as to partially overlap the second electrode, 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. In this case, the molten solder flows into 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. Further, according to the present invention, an epoxy phenol resin is used as a conductive paste for forming the third electrode.
with contaminating Ag- resin-based conductive paste g
I have. 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. The structure of the third electrode is effective even when no resin coat is applied on the glass coat. 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 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, first, the end face of the substrate 2 across the second electrode 6, was mixed with Ag to e Po carboxymethyl phenolic resin Ag
-A third electrode 8 made of a resin-based conductive paste is provided, and the third electrode 8 is provided so as to partially cover the first and second electrodes 6 and 7, thereby achieving conduction between the two. Then, Ni plating 9 and solder plating 10 are applied to cover the entire first, second, and third electrodes. The surface of the resistor 3 is protected by a glass coat 11 and a resin coat 12. The method for 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, if the resin is applied to the end face 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 value, 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 coat 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 type third electrode is provided on the end face of the substrate over the metal glaze type 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 reduced in size due to today's demand for higher packing density. However, even if the electrodes are small, sufficient fixing force can be obtained, and the size and weight of electrical products can be reduced, reliability and durability can be improved. And it greatly contributes to improvement of productivity. According to the present invention, it is possible to obtain a chip resistor having a small change in the resistance value and a small variation in the resistance value. Chip resistors with excellent plating solution properties can be obtained at low cost. In particular, according to the present invention, 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. Molten solder wraps around this gap,
Even if the chip resistor is small, a sufficient fixing force can be obtained. Also, an epoxy pheno provided on the end face of the substrate
Since the Ag-resin-based third electrode in which Ag is mixed into the resin has moderate flexibility, it can sufficiently withstand the bending of the circuit board on which the chip resistor is mounted,
There is an advantage of increased reliability.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of one embodiment of a chip resistor according to 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 Signs] 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

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Mitsuru Yokoyama               3158 Shimo-Okubo, Osawano-cho, Kamishinkawa-gun, Toyama               Hokuriku Electric Industry Co., Ltd. (72) Inventor Yozo Ohara               3158 Shimo-Okubo, Osawano-cho, Kamishinkawa-gun, Toyama               Hokuriku Electric Industry Co., Ltd.                (56) References JP-A-61-245501 (JP, A)                 JP-A-61-268001 (JP, A)                 JP-A-58-87704 (JP, A)                 Shokai Sho 57-119501 (JP, U)                 Shokai 59-185801 (JP, U)

Claims (1)

(57) [Claims] A pair of electrodes are formed at both ends of the substrate surface of the insulating ceramic substrate, a resistor is printed and formed on the substrate surface so as to be connected to the pair of electrodes, and a glass coat is formed to cover the resistor. A chip resistor applied, wherein a resin coat is applied entirely on the glass coat, the pair of electrodes comprises a first electrode of a metal glaze type, and a substrate of the insulating ceramic substrate. At both ends of the back surface, a pair of metal glaze-based second electrodes formed so as to face the first electrode is further provided, and covers an end surface of the insulating ceramic substrate and the first electrode and the second electrode. a third electrode is provided a pair of coated conductive paste so as to connect the electrodes are formed by curing, the first electrode, the plating layer so as to cover the second electrode and the third electrode form The third electrode is formed such that both ends thereof partially overlap the surfaces of the first electrode and the second electrode, respectively, and the third electrode is formed on a circuit board for mounting. The conductive layer used for forming the third electrode partially overlaps the surface of the second electrode such that a gap is formed between the circuit board and the second electrode in the arranged state. Paste and
Ag-mixed with epoxy phenolic resin
A chip resistor using a resin-based conductive paste.