JP3159963B2 - 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. In a conventional chip resistor, a bending force is applied particularly to a circuit board on which the chip resistor is mounted, and the chip resistor is soldered and connected to an electrode of the circuit board. When an excessive force is applied to the electrodes, a pair of electrodes provided at both ends of the substrate may be cracked or a connection failure may occur, resulting in a problem that reliability is reduced. An 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 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, an insulating ceramic substrate is used.
To slits provided vertically and horizontally on both sides of the ceramic plate.
It is used by cutting along. Further, the pair of electrodes is a pair of metal glaze-based first electrodes formed on both ends of the substrate surface of the insulating ceramic substrate, and is provided on both ends of the back surface of the insulating ceramic substrate so as to face the first electrodes. A pair of second formed metal glazes
An electrode, and a pair of third electrodes formed of a conductive paste so as to cover the end surface of the insulating ceramic substrate and connect the first electrode and the second electrode, and provide the first electrode, the second electrode, and the third electrode. A plating layer may be formed so as to cover the three 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. In particular, the insulating ceramic substrate used in the present invention
Has an inclined portion on the edge that forms part of the slit
Therefore, corners that are almost right angles are formed at the edges.
It will not be. Therefore, a third electrode described later is formed.
The conductive paste for the electrode becomes thinner at the corners of the substrate
It is possible to prevent the resistance value at the portion from increasing. And
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. The Ag-resin-based third electrode formed on the end face of the substrate using such a conductive paste has appropriate flexibility, and thus can sufficiently withstand the bending of the circuit board. 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. As shown in FIG . 2, the electrode 4 of the chip resistor 1 is connected to a first electrode 6 to which the resistor 3 is directly connected.
And a second electrode 7 formed to face the first electrode 6 with the substrate 2 interposed therebetween. The first and second electrodes 6 and 7
It is formed by printing a metal glaze paste such as g-Pd or Ag-Pt. Furthermore, the first and second electrodes 6, 7
A third electrode 8 made of an Ag-resin-based conductive paste in which Ag is mixed into a xylene phenol resin or an epoxy phenol resin is provided on the end face of the substrate 2 with the third electrode 8 in between. The two electrodes 6 and 7 are provided so as to partially cover them, thereby achieving conduction between the two electrodes. 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 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. That Although not shown in FIG. 2, when prepared by the method shown in FIG. 3, the insulating ceramic base
The plate 2 constitutes a part of the slits 14 at the edge.
Because it has a slope, the corner that is almost right angle is
It is not formed at the edge. Therefore, the third electrode 8
Conductive paste for forming a thin film at the corners of the substrate 2
To prevent the resistance value at the electrode part from increasing.
You. 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-based third electrode is provided on the end surface 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 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 miniaturization and lightness of electric products, reliability and durability can be achieved. And it greatly contributes to improvement of productivity. According to the present invention, an insulating ceramic substrate is provided.
Has a slope at the edge that forms part of the slit.
Therefore, a corner that is almost right angle is formed at the edge.
The conductive paper for forming the third electrode.
The strike becomes thinner at the corners of the substrate and the resistance at the electrode
It can be prevented from growing. Further , according to the present invention, the third
The electrodes are partially overlapped on the surface of the second electrode so as to form a gap between the circuit board and the second electrode, where the molten solder enters between the circuit board and the second electrode when the electrodes are arranged on the mounting circuit board. ,
The molten solder wraps around this gap, and a sufficient fixing force can be obtained even if the chip resistor is small. Further, since the Ag-resin-based third electrode in which Ag is mixed with the phenolic resin provided on the end face of the substrate has a moderate flexibility, the third electrode can be bent against the bending of the circuit board on which the chip resistor is mounted. 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 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 the front page (72) Inventor Yozo Ohara 3158 Shimookubo, Osawano-cho, Kamishinkawa-gun, Toyama Prefecture Inside Hokuriku Electric Industry Co., Ltd. (JP, A) JP-A-62-176101 (JP, A) JP-A-57-119501 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01C 7/00

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. Wherein the insulating ceramic substrate is provided on both sides of a ceramic plate.
Formed by cutting along the slit provided on the side
The pair of electrodes is formed of a metal glaze-based first electrode, and a pair of metal glaze-based electrodes formed on both ends of the back surface of the insulating ceramic substrate so as to face the first electrode. A second electrode is further provided; a pair of third electrodes formed of a conductive paste so as to cover an end surface of the insulating ceramic substrate and connect the first electrode and the second electrode; A plating layer is formed so as to cover one electrode, the second electrode, and the third electrode, and both ends of the third electrode partially overlap the surfaces of the first electrode and the second electrode, respectively. The third electrode is formed so that a gap in which molten solder enters between the circuit board and the second electrode is formed in a state where the third electrode is arranged on a circuit board for mounting. Surface of two electrodes Are partially overlapped, the third electrode is obtained by mixing Ag into phenolic resin Ag in
-A chip resistor formed of a resin-based conductive paste.