Chip resistor manufacturing method, and chip resistor

A chip resistor having a predetermined resistance value is manufactured by the following method. A resistive element is provided on an upper surface of an insulating substrate. The resistive element includes a wide portion, a first narrow portion extending from the wide portion, and a part extending from the wide portion, the first narrow portion has a smaller width than the wide portion. First and second electrodes are provided on the upper surface of the insulating substrate. The first electrode is located away from the wide portion. The first electrode contacts the first narrow portion. The first electrode overlaps the first narrow portion when viewed from above. The second electrode contacts the part of the resistive element. The second electrode overlaps the part of the resistive element when viewed from above. A distance between the narrow portion and the wide portion is determined so as to cause a resistance value between the first and second electrodes to be the predetermined resistance value. This method improves the precision of the resistance value of the chip resistor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national stage application of the PCT international application No. PCT/JP2018/001116 filed on Jan. 17, 2018, which claims the benefit of foreign priority of Japanese patent application No. 2017-020860 filed on Feb. 8, 2017, the contents all of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a chip resistor used for various electronic devices including a thick-film resistive element.

BACKGROUND ART

FIG. 10is a top plan view of a main portion of conventional chip resistor500.FIG. 11is a top plan view of conventional chip resistor500.FIG. 12is a cross-sectional view of chip resistor500along line XII-XII shown inFIG. 11. Chip resistor500includes insulating substrate1, a pair of upper-surface electrodes2provided on both end portions of an upper surface of insulating substrate1, resistive element3provided on the upper surface of insulating substrate1and between the pair of upper-surface electrodes2, protective film4covering at least resistive element3, a pair of end-surface electrodes5provided on both end faces of insulating substrate1so as to be electrically connected to the pair of upper-surface electrodes2, and plated layer6formed on portions of the upper surfaces of electrodes2and on the surfaces of the pair of end-surface electrodes5.

The pair of upper-surface electrodes2and resistive element3have rectangular shapes when viewed from above. Trimming groove7is formed in resistive element3to adjust the resistance value.

A conventional chip resistor similar to chip resistor500is disclosed in, e.g. PTL 1.

CITATION LIST

Patent Literature

SUMMARY

A chip resistor having a predetermined resistance value is manufactured by the following method. A resistive element is provided on an upper surface of an insulating substrate. The resistive element includes a wide portion, a first narrow portion extending from the wide portion, and a part extending from the wide portion, the first narrow portion has a smaller width than the wide portion. First and second electrodes are provided on the upper surface of the insulating substrate. The first electrode is located away from the wide portion. The first electrode contacts the first narrow portion. The first electrode overlaps the first narrow portion when viewed from above. The second electrode contacts the part of the resistive element. The second electrode overlaps the part of the resistive element when viewed from above. A distance between the first electrode and the wide portion is determined so as to cause a resistance value between the first and second electrodes to be the predetermined resistance value.

This method improves the precision of the resistance value of the chip resistor.

DETAIL DESCRIPTION OF PREFERRED EMBODIMENT

FIG. 1is a top plan view of chip resistor1001according to an exemplary embodiment.FIG. 2is a cross-sectional view of chip resistor1001along line II-II shown inFIG. 1.FIG. 3is a cross-sectional view of chip resistor1001along line III-III shown inFIG. 1.

Chip resistor1001includes insulating substrate11, resistive element13provided at the center of upper surface11aof insulating substrate11, electrodes112and212provided on upper surface11aof insulating substrate11, and protective film16that covers resistive element13and parts of electrodes112and212. Electrodes112and212partially overlap and contact resistive element13. Electrodes112and212are provided on end portions111aand211aof upper surface11aof insulating substrate11opposite to each other in predetermined direction D1, respectively. Resistive element13and electrodes112and212are arranged in direction D1such that resistive element13is positioned between electrodes112and212.

FIG. 4is a top plan view of a main portion of chip resistor1001, and illustrates resistive element13and electrodes112and212. Resistive element13includes wide portion13a, narrow portion113bextending from wide portion13ain direction D11parallel with direction D1, and narrow portion213bextends from wide portion13ain direction D12which is opposite to direction D11and parallel with direction D1. Narrow portions113band213bare parts extending from wide portion13ain directions D11and D12, respectively. Thus, wide portion13aand narrow portions113band213bare arranged in direction D1such that wide portion13ais positioned between narrow portions113band213b. In accordance with the embodiment, respective widths W11and W12of narrow portions113band213bin direction D2perpendicular to direction D1are smaller than width W2of wide portion13aalong direction D2. Electrodes112and212are located away from wide portion13a. Electrodes112and212overlap narrow portions113band213bwhen viewed from above, respectively. Electrodes112and212contact narrow portions113band213b, respectively. Electrodes112and212has ends112aand212afacing wide portion13ain direction D1. Ends112aand212aof electrodes112and212in direction D1are located away from wide portion13aby distances L1and L2, respectively, in direction D1. Wide portion13ahas side surfaces13cand13dthat face opposite to each other in direction D2. Trimming groove15is formed in side surface13cof wide portion13a. Narrow portions113band213bare positioned at the center of wide portion13ain direction D2, and are located away from side surfaces13cand13dof wide portion13a, respectively.

Widths W11and W12of narrow portions113band213brange from 60% to 80% of width W2of wide portion13a. Each of distances L1and L2between wide portion13aand respective one of electrodes112and212ranges from 10% to 20% of length LH of resistive element13in direction D1.

As illustrated inFIG. 2, insulating substrate11further has end surfaces11cand11d. End surface11cis positioned at the end of insulating substrate11in direction D11and connected to upper surface11a. End face11dis positioned at the end of insulating substrate11in direction D12and connected to upper surface11a. Chip resistor1001further includes end-surface electrodes117and217and plated layers118and218. End-surface electrode117is provided on end surface11cof insulating substrate11and is electrically connected to electrode112. End-surface electrode217is provided on end face11dof insulating substrate11and is electrically connected to electrode212. Plated layer118is provided on a part of electrode112and on a surface of end-surface electrode117. Plated layer218is provided on a part of electrode212and on a surface of end-surface electrode217.

Insulating substrate11is made of alumina containing 96% of Al2O3. Upper surface11aof insulating substrate11has a rectangular shape.

Electrodes112and212are formed by printing and sintering a thick film material made of a metal, such as copper, on end portions111aand211aof upper surface11aof insulating substrate11.

Resistive element13is formed by printing a thick film material made of a resist material, such as a copper-nickel alloy, a silver-palladium alloy, or ruthenium oxide, on upper surface11aof insulating substrate11, and then sintering the thick film material.

A current flowing in wide portion13abetween electrodes112and212flows mainly in direction D1within the range of the widths of narrow portions113band213b. Trimming groove15has a length which overlaps none of narrow portions113band213bwhen viewed in direction D1in which the current flows.

Protective film16which covers resistive element13and the parts of electrodes112and212is made of an epoxy resin. As illustrated inFIG. 1, the width of protective film16in direction D2is identical to the width of insulating substrate11in direction D2. Both side surfaces of protective film16in direction D2are exposed from both end surfaces of insulating substrate11in direction D2.

End-surface electrodes117and217are provided on end surfaces11cand11dof insulating substrate11, respectively. End-surface electrodes117and217are formed by printing conductive material made Ag and resin on end surfaces11cand11dof insulating substrate11and on parts of the upper surfaces of electrodes112and212that are exposed from protective film16such that end-surface electrodes117and217are electrically connected to the portions of the upper surfaces of electrodes112and212, respectively. End-surface electrodes117and217may be formed by sputtering metal material.

Each of plated layers118and218includes a Ni-plated layer and a Sn-plated layer on a surface of the Ni-plated layer. The Ni-plated layer is formed on the surface of each of end-surface electrodes117and217. Plated layers118and218contact protective film16.

A method of manufacturing chip resistor1001will be described below.

First, a thick film material made of copper-nickel alloy, silver-palladium alloy, or ruthenium oxide is printed on upper surface11aof insulating substrate11, and is sintered, thereby providing resistive element13having wide portion13aand narrow portions113band213b.

Next, electrodes112and212are formed by printing and sintering a thick film material made of copper on end portions111aand211aof upper surface11aof insulating substrate11. At this moment, electrodes112and212are connected to narrow portions113band213b, respectively while each of distances L1and L2between wide portion13aand respective one of respective ends112aand212aof electrodes112and212are set to predetermined values. By changing distances L1and L2, the effective length of resistive element13that functions as a resistor changes so as to adjust the resistance value between electrodes112and212. In parts of narrow portions113band213bof resistive element13that overlap and contact electrodes112and212, a current flows through electrodes112and212which have a significantly lower resistance value than resistive element13. Therefore, these parts of narrow portions113band213bdo not function as resistors. Accordingly, wide portion13aand parts of narrow portions113band213bof resistive element13that are exposed from electrodes112and212and contact none of electrodes112and212function as a resistor. In other words, the effective length of resistive element13is a length of the portion of resistive element13between ends112aand212aof electrodes112and212in direction D1.

Narrow portions113band213bhaving widths W11and W12smaller than width W2of wide portion13ain direction D2have higher resistance values per unit length in direction D1than wide portion13a. Therefore, the rate of a change of the resistance value with respect to a change of distances L1and L2is large. The resistance value can change over a wide range accordingly, and easily obtain a resistance value that is close to a predetermined value. Therefore, the resistance value can be adjusted precisely.

By previously calculating or measuring the relationship between the resistance value and each of distances L1and L2, the relationship between each of distances L1and L2and the resistance value corresponding to the distances L1and L2is obtained. Based on this relationship, distances L1and L2corresponding to the predetermined resistance value are determined. In other words, by determining distances L1and L2, the resistance value between electrodes112and212are determined.

When a predetermined resistance value cannot be obtained by merely changing distances L1and L2, the length or width of trimming groove15is adjusted so as to finely adjust the resistance value.

Subsequently, protective film16is formed so as to cover at least resistive element13. After that, end-surface electrodes117and217electrically connected to electrodes112and212are formed on end surfaces11cand11dof insulating substrate11, respectively. After that, plated layers118and218are formed on parts of electrodes112and212and on the surfaces of end-surface electrodes117and217, respectively.

In conventional chip resistor500shown inFIGS. 10 to 12, the size of resistive element3is large in view of higher power that is required in recent years. When resistive element3is formed after the forming of upper-surface electrodes2, the exposed area of upper-surface electrodes2becomes relatively small, which may result in various problems, such as connection failures at the position of a probe that measures a resistance value when modifying the resistance value, and poor connectivity with end-surface electrodes5.

On the other hand, when upper-surface electrodes2is formed after the forming of resistive element3in order to provide a sufficient exposed area of upper-surface electrodes2in conventional chip resistor500, the resistance value of resistive element3remains unknown until upper-surface electrodes are formed. Accordingly, when the resistance value exceeds a predetermined range after upper-surface electrodes2are formed, resistive element3and upper-surface electrodes2need to be formed from the beginning. Consequently, it is difficult to adjust the resistance value to a predetermined resistance value in mass production, and to improve the precision of resistance value.

In the above-described method of manufacturing chip resistor1001according to the embodiment, the resistance value can be adjusted by changing each of distances L1and L2between wide portion13aand respective one of electrodes112and212. As a result, the resistance value may be adjusted precisely, thus providing a precise resistance value regardless of the order of the forming of resistive element13and electrodes112and212.

In other words, since the resistance value can be adjusted by each of distances L1and L2between wide portion13aand respective one of electrodes112and212, the resistance value can be adjusted precisely even if electrodes112and212are printed after printing resistive element13.

In chip resistor1001according to the embodiment, the resistance value is adjusted coarsely by changing distances L1and L2, and adjusted finely by forming trimming groove15.

Since the resistance value is adjusted coarsely by changing distances L1and L2, trimming groove15may have a small length. Trimming groove15having a small length shorter prevents the resistance value from fluctuating due to heat generated in resistive element13while forming trimming groove15. Moreover, even if cracks are formed at an end portion of trimming groove15, the current flowing between electrodes112and212flows within the range of the width of narrow portions113band213b. Since the length of trimming groove15is determined such that trimming groove15overlaps none of narrow portions113band213bwhen viewed in direction D1in which the current flows, such cracks do not adversely affect the current significantly.

Widths W11and W12of narrow portions113band213bin direction D2range from 60% to 80% of width W2of wide portion13ain direction D2. Widths W11and W12larger than 80% of width W2cause the rate of change of the resistance value with respect to the change of distances L1and L2to be excessively small, only 20% at most. On the other hand, widths W11and W12smaller than 60% of width W2cause the resistance value of narrow portions113band213bto be excessively large, which means that the rate of the change of the resistance value with respect to the change of distances L1and L2becomes extremely high. Moreover, the load on narrow portions113band213bbecomes excessively high due to the heat generated in narrow portions113band213b.

One of widths W11and W12of narrow portions113band213bmay not necessarily be smaller than width W2of wide portion13a. Even in this case, the same advantageous effects are obtained.

Distances L1and L2may range preferably from 10% to 20% of length LH of resistive element13along direction D1. Distances L1and L2less than 10% of length LH of resistive element13may cause electrodes112and212to contact wide portion13aof resistive element13due to size variations of electrodes112and212and resistive element13. Distances L1and L2larger than 20% of length LH of resistive element13may cause the lengths of narrow portions113band213bin direction D1to be excessively large, and increase the resistance value excessively.

Distances L1and L2may be preferably range from 10 μm to 100 μm, and be equal to each other.

FIG. 5is a top plan view of another chip resistor1002according to the embodiment.FIG. 6is a cross-sectional view of chip resistor1002along line VI-VI shown inFIG. 5.FIG. 7is a cross-sectional view of chip resistor1002along line VII-VII shown inFIG. 5.FIG. 8is a top plan view of a main portion of chip resistor1002. InFIGS. 5 to 8, components identical to those of chip resistor1001shown inFIGS. 1 to 4are denoted by the same reference numerals. In chip resistor1002shown inFIGS. 5 to 8, the structure of electrodes112and212is different from that of chip resistor1001shown inFIGS. 1 to 4.

In chip resistor1002shown inFIGS. 5 to 8, electrode112includes electrode layer152provided on upper surface11aof insulating substrate11, and electrode layer114provided on an upper surface of electrode layer152. Electrode212includes electrode layer252provided on upper surface11aof insulating substrate11, and electrode layer214provided on an upper surface of electrode layer252. Electrode layers114and152extend to an end of upper surface11aof insulating substrate11located in direction D11, and electrode layers214and252extend to an end of upper surface11aof insulating substrate11located in direction D12.

Electrode layer152is located away from wide portion13aby distance L3that is larger than distance L1. Electrode layer152contacts narrow portion113bwhile electrode layer152overlaps narrow portion113bwhen viewed from above. Electrode layer114is located away from wide portion13aby distance L1. Electrode layer114contacts narrow portion113band electrode layer152while electrode layer114overlaps narrow portion113band electrode layer152when viewed from above. Electrode layer252is located away from wide portion13aby distance L4that is larger than distance L2. Electrode layer252contacts narrow portion213bwhile electrode layer252overlaps narrow portion213bwhen viewed from above. Electrode layer214is located away from wide portion13aby distance L2. Electrode layer214contacts narrow portion213band electrode layer252while electrode layer214overlaps narrow portion213band electrode layer252when viewed from above.

Electrode layers152and252are made of the same material as electrodes112and212of chip resistor1001shown inFIGS. 1 to 4. Electrode layers114and214are made of the same material as electrode layers152and252.

Electrode layers114and214are relatively thin, and accordingly, have ends114aand214awith precisely, thereby providing the resistance value precisely.

Electrode layers114and214allow the surfaces of electrodes112and212to be smooth. This configuration allows plated layers118and218to be connected firmly to the surfaces of electrodes112and212. When chip resistor1002is in use, a current flows from plated layers118and218into resistive element13mainly through electrode layers114and214. For this reason, electrode layers114and214preferably extend to end faces11cand11dof insulating substrate11and contact narrow portions113band213bof resistive element13, respectively.

FIG. 9is a top plan view of a main portion of still another chip resistor1003according to the embodiment. InFIG. 9, components identical to those of chip resistor1002shown inFIGS. 5 to 8are denoted by the same reference numerals. In chip resistor1002shown inFIG. 9, electrode layers114and214do not extend to end surfaces11cand11dof insulating substrate11, respectively. The resistance value of chip resistor1003may be adjusted accurately by changing distances L1and L2between wide portion13aand respective electrode layers114and214.

In the above embodiment, terms, such as “upper surface” and “when viewed from above”, indicating directions merely indicate relative directions determined only by relative positional relationships of the structural components of the chip resistor, and do not indicate absolute directions, such as a vertical direction.

REFERENCE MARKS IN THE DRAWINGS