Chip resistor

Abstract

To provide a chip resistor suitable for reducing the size and excellent in surge characteristic.SOLUTION: In a chip resistor 1 of the present invention, a resistor 7 electrically connecting between a first front electrode 3 and a second front electrode 4 is printed and formed in a crank shape having a first resistor part 7a, a second resistor part 7b, and a third resistor part 7c, a first region S1 surrounded by a parallelogram, in which a first deriving part 7b-1 of the second resistor part 7b and a second deriving part 7c-1 of the third resistor part 7c in this resistor 7 constitute opposite sides, is a part where a large amount of current flows, and two second regions S2a, S2b existing outside the first region S1 is a part where the current distribution is small. A trimming groove 12 for adjusting the resistance value includes a rough adjustment part 12a extending into the first region S1 passing the second region S2a in contact with a lower side of the first resistor part 7a, and a fine adjustment part 12b extending to a position reaching the second region S2a again while passing from a tip of the rough adjustment part 12a through the first region S1, and is formed to have an L cut shape as a whole.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a chip resistor in which the resistance value is adjusted by forming a trimming groove in the resistor element. [Background technology]

[0002] A chip resistor is mainly composed of a rectangular insulating substrate, a pair of front electrodes arranged opposite each other with a specified distance on the surface of the insulating substrate, a pair of back electrodes arranged opposite each other with a specified distance on the back surface of the insulating substrate, end electrodes bridging the front electrodes and the back electrodes, a resistive element bridging the pair of front electrodes, and a protective film covering the resistive element.

[0003] Generally, when manufacturing this type of chip resistor, a large number of electrodes, resistors, protective films, etc. are formed on a large sheet-like substrate at once, and then the large substrate is divided along grid-like dividing lines (e.g., dividing grooves) to obtain a large number of chip resistors. In the manufacturing process of such chip resistors, a large number of resistors are formed on one side of the large substrate by printing and firing a resistive paste, but since it is difficult to avoid slight variations in the size and film thickness of each resistor due to misalignment or bleeding during printing or uneven temperature in the firing furnace, a resistance value adjustment work is performed in which trimming grooves are formed in each resistor while the substrate is still in the large substrate and the desired resistance value is set.

[0004] When a surge voltage generated by static electricity or power supply noise is applied to a chip resistor having such a configuration, the excessive electrical stress affects the characteristics of the resistor, and in the worst case, the resistor may be destroyed. It is known that the surge characteristics can be improved by making the resistor meandering (meandering) and increasing its overall length, which makes the potential drop more gradual.

[0005] For example, as described in Patent Document 1, a chip resistor is proposed in which a serpentine-shaped resistor is formed on the main surface of an insulating substrate by a printing technique, and then trimming grooves are formed in opposite directions extending linearly from each of the opposing sides of the resistor, and these two trimming grooves are extended to a position where their tips intersect, causing the resistor to meander near the tips of the two trimming grooves, thereby increasing its overall length.

[0006] In a chip resistor configured in this manner, two trimming grooves that extend linearly relative to the resistor element are formed in opposite directions at 180 degrees, so that the main current path of the resistor element changes by 180 degrees at the point where the tips of the two trimming grooves intersect. This increases the overall length of the printed resistor element and improves surge characteristics. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2006-19694 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the conventional technology described in Patent Document 1, in which the tips of two trimming grooves are arranged to intersect with each other and the current path is turned 180 degrees, microcracks that occur at the tips of the two trimming grooves occur in the turn where the load is concentrated, so that when a high voltage is applied, there is a risk that the resistor will be destroyed due to a local temperature rise. In particular, in small-sized chip resistors with a small board area, the width dimension of the resistor becomes very narrow as the overall length of the resistor is increased by the trimming grooves, so when the chip resistor is used with a large power load, the current per unit area (current density) becomes large, and a problem occurs in that the resistor cannot withstand the load and is prone to destruction.

[0009] The present invention has been made in view of the above-mentioned state of the art, and an object of the present invention is to provide a chip resistor which has excellent surge characteristics and is suitable for miniaturization. [Means for solving the problem]

[0010] In order to achieve the above object, the chip resistor of the present invention comprises a rectangular parallelepiped insulating substrate, a first surface electrode and a second surface electrode arranged to face each other at both ends of the insulating substrate with a gap of a certain width therebetween, and a resistor arranged in the gap to bridge between the first surface electrode and the second surface electrode, and a resistance value is adjusted by forming a trimming groove in the resistor, the resistor comprising a rectangular first resistor portion extending parallel to the first surface electrode and the second surface electrode, a rectangular second resistor portion connected to one side of the first resistor portion via a first lead portion connected to the first surface electrode, and a second lead portion connected to the second surface electrode. and a third resistor portion connected to the other side portion of the first resistor portion, and a region within the resistor surrounded by a parallelogram with the first lead-out portion and the second lead-out portion as opposite sides is defined as a first region, and two triangular regions located outside the first region are defined as second regions, respectively.The trimming groove has a coarse adjustment portion that extends in a straight line from one of the opposing outer edges of the first resistor portion as a starting point toward the other outer edge, passes through the second region and reaches at least the first region, and a fine adjustment portion that extends in a perpendicular direction from the tip of the coarse adjustment portion, passes through at least the first region, and extends until it reaches the second region again.

[0011] In the chip resistor thus constructed, the resistor having the first resistor portion, the second resistor portion, and the third resistor portion is generally formed in a crank shape, so that the entire length of the resistor can be secured and the resistor can have stable surge characteristics. In addition, in a resistor having such a shape, the first region is a region where a large amount of current flows, and the second region is a region where the current distribution is small, but the trimming groove for adjusting the resistance value is formed in an L-cut shape so that it runs from the second region through the first region to the second region again, so that the region where microcracks occur can be separated from the current path where the load is concentrated. Moreover, since the main current path becomes long without having a turn portion after the resistance value adjustment, the adverse effects on the characteristics caused by microcracks can be reduced and the surge characteristics can be further improved.

[0012] In the chip resistor having the above configuration, if the tip of the coarse adjustment portion, which is the bent portion of the trimming groove, is located within the first region, the width dimension of the first resistor portion, which narrows with the amount of cutting of the coarse adjustment portion, is limited to a certain extent, so that the resistance width of the resistor does not become extremely thin, and high power can be supported even if the chip resistor is miniaturized. However, the coarse adjustment portion of the trimming groove may extend beyond the first region to a position where it reaches the second region, and in that case, after forming the coarse adjustment portion from one second region beyond the first region to the other second region, the fine adjustment portion may be extended from the tip of the coarse adjustment portion from the other second region beyond the first region to one second region.

[0013] Furthermore, in a chip resistor having the above configuration, if the length of the outer edge of the first resistor portion is L, it is preferable that the starting end of the trimming groove is set within a range of L / 2 from the first derivation portion of the second resistor portion or the second derivation portion of the third resistor portion, since this makes it possible to extend the current path after adjusting the resistance value. Effect of the Invention

[0014] According to the present invention, it is possible to provide a chip resistor that has excellent surge characteristics and is suitable for miniaturization. [Brief description of the drawings]

[0015] [Figure 1] 1 is a plan view of a chip resistor according to a first embodiment of the present invention; [Diagram 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Diagram 3] 2 is an explanatory diagram of a resistor provided in the chip resistor of FIG. 1. [Figure 4] FIG. 5 is a plan view of a chip resistor according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0017] FIG. 1 is a plan view of a chip resistor according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line II-II in FIG.

[0018] 1 and 2, the chip resistor 1 according to the first embodiment is mainly composed of a rectangular parallelepiped insulating substrate 2, a first front electrode 3 and a second front electrode 4 provided at both ends in the short side direction on the front surface of the insulating substrate 2, a first back electrode 5 and a second back electrode 6 provided at both ends in the short side direction on the back surface of the insulating substrate 2, a resistor 7 provided to conduct electricity between the pair of the first front electrode 3 and the second front electrode 4, an undercoat layer 8 provided to cover the resistor 7, an overcoat layer 9 provided to cover the undercoat layer 8, a pair of end electrodes 10 provided on both ends in the short side direction of the insulating substrate 2, and a pair of external electrodes 11 provided to cover the end electrodes 10. In the following description, the longitudinal direction of the insulating substrate 2 (the left-right direction in FIG. 1) is the X-axis, and the short side direction of the insulating substrate 2 (the up-down direction in FIG. 1) is the Y-axis.

[0019] The insulating substrate 2 is obtained by dividing a large sheet-like substrate along primary dividing grooves and secondary dividing grooves that extend vertically and horizontally into multiple pieces, and the large substrate is a ceramic substrate whose main component is alumina.

[0020] The first surface electrode 3 and the second surface electrode 4 are formed by screen printing an Ag-based paste containing Ag (silver) as the main component, followed by drying and firing. The first surface electrode 3 and the second surface electrode 4 are formed along the long side of the surface of the insulating substrate 2, with a certain width of gap in the short direction (Y-axis direction).

[0021] The first back electrode 5 and the second back electrode 6 are formed by screen printing an Ag-based paste, followed by drying and firing. The first back electrode 5 and the second back electrode 6 are formed along the long side of the rear surface of the insulating substrate 2 with a certain gap therebetween in the short direction.

[0022] Resistor 7 is formed by screen printing resistor paste such as ruthenium oxide, drying and baking it. As will be described in detail later, resistor 7 has one trimming groove 12 formed therein, and the initial resistance value of resistor 7 formed by printing is adjusted to a target resistance value by this trimming groove 12.

[0023] The undercoat layer 8 is formed by screen printing a glass paste, followed by drying and baking. The undercoat layer 8 is formed so as to cover the entire resistor 7 before the trimming groove 12 is formed.

[0024] The overcoat layer 9 is formed by screen printing a resin paste such as an epoxy resin or a phenol resin and then heat-curing it. The overcoat layer 9 is formed so as to cover the entire undercoat layer 8 after the trimming grooves 12 are formed.

[0025] The pair of end electrodes 10 are formed by sputtering Ni-Cr or the like, and provide electrical conductivity between the first front electrode 3 and the first back electrode 5, and between the second front electrode 4 and the second back electrode 6, which are separated by the end faces of the insulating substrate 2.

[0026] A pair of external electrodes 11 each have a two-layer structure consisting of an inner barrier layer 13 and an outer external connection layer 14, of which the barrier layer 13 is a Ni plating layer formed by electrolytic plating, and the external connection layer 14 is a Sn plating layer formed by electrolytic plating.

[0027] Figure 3 is an explanatory diagram of a resistor 7 provided in a chip resistor 1, where Figure 3(A) shows the state before the trimming groove 12 is formed, and Figure 3(B) shows the state after the trimming groove 12 has been formed.

[0028] 3(A), the first front electrode 3 and the second front electrode 4 are disposed opposite each other at both ends in the short side direction on the surface of the insulating substrate 2 with a gap D of a certain width therebetween, and a resistor 7 is printed in the gap D to provide electrical continuity between the first front electrode 3 and the second front electrode 4. The resistor 7 has a rectangular first resistor portion 7a disposed in the center of the gap D and extending parallel to the first front electrode 3 and the second front electrode 4 (in the X-axis direction), a rectangular second resistor portion 7b extending in the Y-axis direction from a first lead-out portion 7b-1 connected to the first front electrode 3 to partway through the gap D and connected to the left side of the first resistor portion 7a in the figure, and a third resistor portion 7c extending in the Y-axis direction from a second lead-out portion 7c-1 connected to the second front electrode 4 to partway through the gap D and connected to the right side of the first resistor portion 7a in the figure.

[0029] The resistor 7 thus printed has a crank shape that is point-symmetrical with respect to the center of the first resistor portion 7a, and the crank shape increases the overall length of the resistor 7, ensuring the overall length of the resistor 7 and providing stable surge characteristics. In the resistor 7 having such a shape, the main current path through which the largest amount of current flows from the first front electrode 3 to the second front electrode 4 is a straight path from the first lead portion 7b-1 of the first front electrode 3 through the center of the first resistor portion 7a to the second lead portion 7c-1 of the second front electrode 4. In other words, if a region surrounded by a parallelogram with the first lead portion 7b-1 and the second lead portion 7c-1 as opposite sides in the resistor 7 is defined as a first region S1, and two triangular regions located on the outside of the first region S1 are defined as second regions S2a and S2b, respectively, the first region S1 is a region through which a large amount of current flows, and the two second regions S2a and S2b are regions with a small current distribution.

[0030] As shown in FIG. 3B, by forming one trimming groove 12 in such a crank-shaped resistor 7, the initial resistance value of the resistor 7 after printing is adjusted to a target resistance value.

[0031] The trimming groove 12 is made up of a coarse adjustment portion 12a that extends linearly upward along the Y axis from the bottom side of the first resistor portion 7a, and a fine adjustment portion 12b that bends at a right angle from the tip of the coarse adjustment portion 12a and extends linearly to the right along the X axis, and is generally formed in an L-cut shape. Here, the coarse adjustment portion 12a passes through the second region S2a that contacts the bottom side of the first resistor portion 7a and extends into the first region S1, and the fine adjustment portion 12b extends from the tip of the coarse adjustment portion 12a through the first region S1 to a position where it again reaches the second region S2a.

[0032] The coarse adjustment portion 12a of the trimming groove 12 is formed from the second region S2a where the current distribution in the resistor 7 is small to the position where it reaches the first region S1, so that the width dimension of the first resistor portion 7a is narrowed by extending the cutting amount of the coarse adjustment portion 12a in the Y-axis direction, and the resistance value can be coarsely adjusted. On the other hand, the fine adjustment portion 12b of the trimming groove 12 is formed from the first region S1 where the tip of the coarse adjustment portion 12a is located toward the second region S2a where the current distribution is small again, and the ratio of the resistance value increment to the cutting amount increment of the fine adjustment portion 12b is small, so that the resistance value can be finely adjusted with high accuracy by extending the cutting amount of the fine adjustment portion 12b in the X-axis direction. And, since the tip of the trimming groove 12 formed in an L-cut shape is located in the second region S2a, the occurrence site of the microcracks can be separated from the current path where the load is concentrated. At this time, by extending the tip of the trimming groove 12 to the third resistor portion 7c, the site where the microcracks occur can be further separated from the current path, so that the effect of the microcracks can be further reduced.

[0033] Furthermore, in resistor 7 after the resistance value is adjusted by trimming groove 12, the main current path through which the greatest current flows from first front electrode 3 to second front electrode 4 is a curved path that runs from first lead-out portion 7b-1 of first front electrode 3 through a corner portion (tip of coarse adjustment portion 12a) of trimming groove 12 to second lead-out portion 7c-1 of second front electrode 4. This curved main current path is longer than the linear main current path that flows in resistor 7 before the resistance value is adjusted, so that the surge characteristics that are ensured by printing and forming resistor 7 in a crank shape are further improved by forming trimming groove 12.

[0034] Here, the starting position of the trimming groove 12 in the second region S2a is not particularly limited, but if the length of the outer edge of the first resistor portion 7a along the X-axis direction is L, the starting position of the trimming groove 12 is set within a range of L / 2 from the first derived portion 7b-1 of the second resistor portion 7b.

[0035] The trimming groove 12 may be formed with its start position on the upper side instead of the lower side of the first resistor portion 7a. In this case, the coarse adjustment portion 12a is formed to a position where it passes through the second region S2b that contacts the upper side of the first resistor portion 7a and reaches the first region S1, and then the fine adjustment portion 12b is formed from the tip of the coarse adjustment portion 12a through the first region S1 to a position where it again reaches the second region S2b. In this case, the start position of the trimming groove 12 in the second region S2b is set within a range of L / 2 from the second lead-out portion 7c-1 of the third resistor portion 7c.

[0036] As described above, in the chip resistor 1 of the first embodiment, the resistor 7 is printed and formed in the gap D between the first surface electrode 3 and the second surface electrode 4. The resistor 7 has a rectangular first resistor portion 7a that is positioned in the center of the gap D and extends parallel to the first surface electrode 3 and the second surface electrode 4, a rectangular second resistor portion 7b that extends in the Y-axis direction from the first lead-out portion 7b-1 connected to the first surface electrode 3 to partway through the gap D and connects to one side of the first resistor portion 7a, and a third resistor portion 7c that extends in the Y-axis direction from the second lead-out portion 7c-1 connected to the second surface electrode 4 to partway through the gap D and connects to the other side of the first resistor portion 7a. Since the resistor 7 is printed and formed in a crank shape overall, the entire length of the resistor 7 can be secured to provide stable surge characteristics.

[0037] In such a crank-shaped resistor 7, the first region S1 surrounded by a parallelogram with the first lead-out portion 7b-1 and the second lead-out portion 7c-1 as opposite sides is a region where a large amount of current flows, and the two triangular second regions S2a, S2b located on the outside of the first region S1 are regions where the current distribution is small, but the trimming groove 12 for adjusting the resistance value is formed in an L-cut shape so as to run from one of the second regions S2a (or S2b) through the first region S1 to the second region S2a (or S2b) again, so that the region where microcracks occur can be separated from the current path where the load is concentrated. Moreover, since the main current path becomes long without having a turn portion after the resistance value adjustment, the adverse effects on the characteristics caused by microcracks can be reduced and the surge characteristics can be further improved.

[0038] In addition, since the tip position of the coarse adjustment portion 12a, which is the bent portion of the trimming groove 12, is set within the first region S1, the width dimension of the first resistor portion 7a, which narrows with the amount of cutting of the coarse adjustment portion 12a, is limited to a certain extent. As a result, the resistance width of the resistor 7 does not become extremely narrow, and even the miniaturized chip resistor 1 can handle high power.

[0039] Furthermore, when the length of the outer edge of the first resistor portion 7a along the X-axis direction is L, the starting end of the trimming groove 12 is set within a range of L / 2 from the first lead-out portion 7b-1 of the second resistor portion 7b or the second lead-out portion 7c-1 of the third resistor portion 7c, so that the current path can be extended long after the resistance value is adjusted.

[0040] FIG. 4 is a plan view of a chip resistor 20 according to a second embodiment of the present invention, and parts corresponding to those in FIGS. 1 to 3 are given the same reference numerals and overlapping descriptions will be omitted as appropriate.

[0041] In the chip resistor 20 of the second embodiment, the trimming groove 12 for adjusting the resistance value formed in the resistor 7 comprises a coarse adjustment portion 12a extending upward on the Y-axis from one second region S2a, passing through the first region S1 to the other second region S2b, and a fine adjustment portion 12b extending to the right on the X-axis from the tip of the coarse adjustment portion 12a located in the second region S2b, passing through the first region S1, and again to one second region S2a; the other configuration is basically the same as that of the chip resistor 1 of the first embodiment.

[0042] In the second embodiment, too, it is possible to form the trimming groove 12 with the upper side of the first resistor portion 7a as the starting position. In that case, the coarse adjustment portion 12a may be formed from the other second region S2b through the first region S1 to one second region S2a along the downward direction of the Y axis, and then the fine adjustment portion 12b may be formed from one second region S2a through the first region S1 to the other second region S2b again along the leftward direction of the X axis.

[0043] In the chip resistor 20 according to the second embodiment configured as described above, the resistor 7 is printed in a crank shape, so that the resistor 7 can have a stable surge characteristic by ensuring its overall length. The trimming groove 12 for adjusting the resistance value is formed in an L-cut shape having a coarse adjustment portion 12a that passes through the first region S1 from one of the second regions S2a (or S2b) to the other of the second regions S2b (or S2a), and a fine adjustment portion 12b that passes through the first region S1 from the other of the second regions S2b (or S2a) to the one of the second regions S2a (or S2b) again, so that the occurrence site of the microcracks can be separated from the current path where the load is concentrated. Moreover, since the main current path becomes long without having a turn portion after the resistance value adjustment, the adverse effect on the characteristics caused by the microcracks can be reduced and the surge characteristic can be further improved.

[0044] The present invention is not limited to the above-mentioned embodiment, and various modifications are possible without departing from the gist of the present invention, and all technical matters included in the technical ideas described in the claims are the subject of the present invention. The above-mentioned embodiment shows a preferred example, but a person skilled in the art can realize various alternatives, modifications, variations, or improvements from the contents disclosed in this specification, and these are included in the technical scope described in the attached claims.

[0045] For example, in each of the above embodiments, the first front electrode 3, the second front electrode 4, the first back electrode 5, and the second back electrode 6 are each formed along the long sides of the insulating substrate 2, but they may also be formed along the short sides of the insulating substrate 2. [Explanation of symbols]

[0046] 1,20 Chip resistor 2. Insulating substrate 3 Table 1 Electrodes 4 Table 2 Electrodes 5 First back electrode 6 Second back electrode 7 Resistor 7a 1st resistor part 7b 2nd resistor part 7b-1 First derivation part 7c 3rd resistor part 7c-1 Second derived part 8 Undercoat layer 9. Overcoat 10 Edge electrode 11 External electrode 12 Trimming 12a Coarse adjustment section 12b Fine adjustment section 13 Barrier Layer 14 External Connection Layer D gap S1 1st area S2a,S2b 2nd area

Claims

1. A chip resistor comprising: an insulating substrate having a rectangular parallelepiped shape; a first front electrode and a second front electrode disposed opposite each end of the insulating substrate with a gap of a certain width therebetween; and a resistor disposed in the gap and bridging between the first front electrode and the second front electrode, the resistance value of which is adjusted by forming a trimming groove in the resistor, the resistor has a rectangular first resistor portion extending parallel to the first surface electrode and the second surface electrode, a rectangular second resistor portion connected to one side of the first resistor portion via a first lead portion connected to the first surface electrode, and a third resistor portion connected to the other side of the first resistor portion via a second lead portion connected to the second surface electrode, A region surrounded by a parallelogram having opposite sides defined by the first lead-out portion and the second lead-out portion in the resistor is defined as a first region, and two triangular regions located outside the first region are defined as second regions, The trimming groove has a coarse adjustment portion that extends linearly from one of the opposing outer edges of the first resistor portion toward the other outer edge, passes through the second region, and reaches at least the first region, and a fine adjustment portion that extends perpendicularly from the tip of the coarse adjustment portion, passes through at least the first region, and extends again to reach the second region. A chip resistor characterized in that

2. 2. The chip resistor according to claim 1, wherein a tip of the coarse adjustment portion is located within the first region.

3. 2. The chip resistor according to claim 1, characterized in that, when the length of the outer edge of the first resistor portion is L, the starting end of the trimming groove is set within a range of L / 2 from the first lead-out portion or the second lead-out portion.

4. 2. The chip resistor according to claim 1, wherein a tip of the fine adjustment portion is located within the third region.

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