JP2806802B2 - 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. After the trimming is completed, the overcoat is further placed on the glass coat (lower glass coat).
There has also been proposed a chip resistor having a structure in which a glass coat (upper glass coat) is provided as a sheet . [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 considered to be the best. Had a double or more glass coat. However, when the upper glass coat is applied,
If the trace of laser trimming is deep, or if it is wide, it may be fired with bubbles in the trace,
Cracks easily occur 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. [0004] In addition, chip resistors are shipped in a state in which many chip resistors are packed in a single bag, except in the case of taping parts. The coat covering the resistor of the chip resistor will be hit quite frequently. However, since the glass coat is hard and easily cracks, when the outermost layer of the coat formed on the resistor is made of glass, the glass coat cracks when an external force is locally applied. High risk. In addition, in the case of chip resistors, characteristic indication such as resistance value and number is displayed on the outermost layer of the coat formed on the resistor so that the resistance value of the chip resistor can be confirmed even after mounting Printed using ink. However, when the outermost layer is made of a glass coat, when a characteristic display or the like is printed thereon, the surface of the glass coat has irregularities and the printability is poor, and the display ink is difficult to adhere, so that the display becomes unclear. There is. In the case of a component having a very small size, such as a chip resistor, the characteristic display becomes very small, and a defective product may occur due to poor printability, so that printability is very important. An object of the present invention is to provide a chip resistor which can prevent occurrence of cracks in a glass coat and has excellent printability on a coat surface. SUMMARY OF THE INVENTION The invention of the present application is directed to an insulating ceramic substrate in which a pair of electrodes are formed at both ends of a substrate surface of an insulating ceramic substrate, and a resistor is formed on the substrate surface so as to be connected to the pair of electrodes. The resistor is printed and a glass coat is applied on the resistor, and trimming grooves are formed on the resistor and the glass coat.
All over the glass coat to fill the trimming grooves.
Chip resistors that are physically overcoated are targeted for improvement . In the present invention, the overcoat is
It is formed by coating. [0006] Since the viscosity of the resin for forming the resin coat can be freely changed, when the resin coat is applied on the glass coat having the trimmed traces, ie, the trimmed grooves , Trimming by laser trimming by setting the resin to an appropriate viscosity
Even if the trimming groove is deep or wide, the resin smoothly enters the trimming groove (as shown in FIG. 2), and there is no fear of taking in bubbles. In addition, the resin is softer than glass and does not crack even if a slight level difference occurs. Therefore, if the outermost layer of the coat formed on the resistor is a resin coat, the glass coat thereunder can be protected. In particular, since the resin coat can be formed to be thicker than the glass coat, if the resin coat is made somewhat thick, the lower glass coat to be coated with the resin has large irregularities due to the trimming grooves. Also,
There is no portion where the resin coat becomes extremely thin, and it is possible to prevent moisture and plating solution from entering the inside through the trimming groove . In addition, the surface of the resin coat has good printability of the display ink, and enables precise and clear printing. As described above, according to the present invention, the trimming groove is provided.
Fills the trimming groove without introducing air bubbles
It can, also be obtained to be able to prevent the cracking occurs in the glass coating, yet excellent chip resistor printability of the coated surface. 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, 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 applying 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 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 face 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 miniaturized in accordance with today's demand for higher packing density. However, even if the electrodes are small, a sufficient fixing force can be obtained, and the miniaturization and weight reduction, reliability and durability of electric products can be obtained. And it greatly contributes to improvement of productivity. When a resin coat is applied on a glass coat as in the present embodiment, the trimming resistance value is hardly affected compared to the case where a glass coat is applied again, and a chip with less variation in resistance value. There is an advantage that a resistor can be obtained. In addition, the resin for forming the resin coat can change the viscosity freely,
By making the resin have an appropriate viscosity, even when the trace of laser trimming is deep or wide, there is no fear that the resin will smoothly enter the trace and take in bubbles.
In addition, the resin is softer than glass and does not crack even if a slight level difference occurs. Furthermore, the resin coat can be formed to be thicker than the glass coat, so if the resin coat is thickened to some extent, there will be no part where the resin coat becomes extremely thin around traces of trimming, The liquid can be prevented 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 and consumes less power,
Manufacturing costs can be reduced. Therefore, according to the present embodiment, it is possible to obtain a chip resistor having a small change in resistance value and a small variation in the resistance value, and is excellent in moisture resistance, solvent resistance and plating solution resistance with little aging. Chip resistors can be obtained at low cost. According to the present invention, the overcoat can be
Resistor and glass coat
Without taking air bubbles into the trimming groove
The trimming groove can be filled. Also resin coat
Can be formed thicker than glass coats.
If the thickness of the gin coat is increased to some extent,
Coating the lower glass coat with a trimming groove
Extremely thin resin coat even with large irregularities
Such a part can not be formed, through the trimming groove
It prevents moisture and plating solution from entering inside.
Wear. Furthermore, it is possible to prevent the occurrence of cracks in the glass coat, and to obtain a chip resistor excellent in printability on the coat surface.

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-60-27104 (JP, A)                 JP-A-58-101 (JP, A)

Claims (1)

(57) [Claims] A pair of electrodes are formed on 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 applied on the resistor. The resistor and the glass core
A trimming groove is formed in the glass
Overcoat so as to fill the trimming groove
A chip resistor, wherein the overcoat is made of a resin coat .