Chip Resistors

Abstract

To provide a chip resistor that can improve heat shock resistance.SOLUTION: A back surface electrode 14 of the chip resistor 1 has a first back surface electrode 14a provided on the inner side away from the end surface of an insulating substrate 10, and a second back surface electrode 14b provided on the outer side near the end surface of the insulating substrate 10 to contact (adjacent) the first back surface electrode 14a. The electrical resistivity of the first backside electrode 14a is lower than that of the second backside electrode 14b.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a surface-mount type chip resistor that is soldered onto a land of a circuit board. [Background technology]

[0002] Generally, a chip resistor comprises a rectangular parallelepiped insulating substrate, a pair of surface electrodes provided at both longitudinal ends of the surface of the insulating substrate, a resistor provided so as to straddle the pair of surface electrodes, a pair of back surface electrodes provided at both longitudinal ends of the back surface of the insulating substrate, a pair of end surface electrodes provided at both longitudinal ends of the insulating substrate and electrically connecting the surface electrodes and the back surface electrodes, and an external electrode provided so as to cover the back surface electrode and the end surface electrodes. This type of chip resistor is surface-mounted by mounting the back surface electrode facing downward on a land provided on a circuit substrate and soldering it.

[0003] In the chip resistor surface-mounted as described above, repeated changes in the thermal environment (hereinafter referred to as "heat shock") cause thermal stress due to the difference between the thermal expansion coefficient of the circuit board and the thermal expansion coefficient of the insulating substrate of the chip resistor. This thermal stress acts on the solder joint that joins the circuit board and the chip resistor, causing cracks. Therefore, the chip resistor described in Patent Document 1 has a back electrode that includes a stress relaxation layer made of a synthetic resin material provided on the insulating substrate, and a metal thin film layer provided on the stress relaxation layer. Even if such a chip resistor is exposed to a heat shock when surface-mounted on a circuit board, the thermal stress acting on the solder joint can be relaxed by the stress relaxation layer, so that it has heat shock resistance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 123422 Summary of the Invention [Problem to be solved by the invention]

[0005] In the chip resistor described in Patent Document 1, the surface of the stress relaxation layer is entirely covered with a thin metal layer so that the external electrodes can be stably formed on the back electrodes by electrolytic plating. Therefore, although the external electrodes can be stably formed, there is a risk that the thin metal layer will hinder the relaxation of thermal stress by the stress relaxation layer, and there is still room for improvement in terms of heat shock resistance.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a chip resistor capable of improving heat shock resistance. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the present invention comprises an insulating substrate having a rectangular parallelepiped shape, a pair of surface electrodes provided at both longitudinal ends of the surface of the insulating substrate, a resistor provided so as to straddle the pair of surface electrodes, a pair of back electrodes provided at both longitudinal ends of the back surface of the insulating substrate and made of a synthetic resin material containing conductive particles, a pair of end surface electrodes provided on both longitudinal end faces of the insulating substrate and electrically connecting the surface electrodes and the back surface electrode, and an external electrode formed by electrolytic plating to cover the back surface electrodes and the end surface electrodes, wherein the back surface electrodes have at least a first back surface electrode provided on an inner side away from the end surface of the insulating substrate, and a second back surface electrode provided on an outer side near the end surface of the insulating substrate so as to be adjacent to the first back surface electrode, and the electrical resistivity of the first back surface electrode is lower than the electrical resistivity of the second back surface electrode.

[0008] According to the chip resistor configured in this manner, the flexibility of both the first back electrode and the second back electrode made of a synthetic resin material containing conductive particles can absorb and alleviate thermal stress during heat shock. This improves the heat shock resistance of the chip resistor. Moreover, the first back electrode serves as a starting point for forming external electrodes by electrolytic plating in the manufacturing process of the chip resistor, allowing the external electrodes to be stably formed around the back electrodes.

[0009] In the above configuration, if the first back surface electrode is configured to cover a portion of the second back surface electrode, it is possible to facilitate flow of current from the first back surface electrode to the second back surface electrode during electrolytic plating.

[0010] Furthermore, in the above configuration, if the first back surface electrode has at least a portion interposed between the insulating substrate and the second back surface electrode, it is possible to facilitate flow of current from the first back surface electrode to the second back surface electrode when performing electrolytic plating.

[0011] Furthermore, in the above configuration, if the first back surface electrode is provided on the insulating substrate and the second back surface electrode is provided on the first back surface electrode, it becomes easier to pass current from the first back surface electrode to the second back surface electrode when performing electrolytic plating.

[0012] Furthermore, in the above configuration, if the second back surface electrode is configured to be in contact with the insulating substrate on the outer side of the insulating substrate, it is possible to make it easier to divide the insulating substrate on which the back surface electrode is formed during the manufacturing process of the chip resistor.

[0013] Furthermore, in the above configuration, if the conductive particles contained in the first back surface electrode are metal particles and the conductive particles contained in the second back surface electrode are carbon particles, the first back surface electrode can form a starting point for forming an external electrode by electrolytic plating, and the second back surface electrode can relieve thermal stress during heat shock. Effect of the Invention

[0014] According to the present invention, heat shock resistance can be improved. [Brief description of the drawings]

[0015] [Figure 1] FIG. 2 is a plan view of the chip resistor according to the first embodiment. [Diagram 2] FIG. 2 is a cross-sectional view taken along line II-II of FIG. [Diagram 3] FIG. 2 is a plan view showing a back electrode of the chip resistor. [Figure 4] 1(a) to 1(d) are cross-sectional views showing a manufacturing process of a chip resistor. [Diagram 5] 5(e) to 5(h) are cross-sectional views showing a manufacturing process of the chip resistor. [Figure 6] 1(i) is a cross-sectional view showing a manufacturing process of a chip resistor. [Figure 7] 1 is a flowchart showing a manufacturing process of a chip resistor. [Figure 8] FIG. 2 is a cross-sectional view showing a mounted state of the chip resistor. [Figure 9] FIG. 6 is a cross-sectional view of a chip resistor according to a second embodiment. [Figure 10] FIG. 11 is a cross-sectional view of a chip resistor according to a modified example. [Figure 11] FIG. 11 is a cross-sectional view of a chip resistor according to a third embodiment. [Figure 12] FIG. 11 is a cross-sectional view of a chip resistor according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

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

[0018] As shown in Figures 1 and 2, the chip resistor 1 comprises a rectangular insulating substrate 10, a pair of surface electrodes 11 provided at both longitudinal ends of the surface (top surface in Figure 2) of the insulating substrate 10, a resistor 12 provided so as to straddle the surface electrodes 11, a protective layer 13 of a two-layer structure provided so as to cover the resistor 12, a pair of back surface electrodes 14 provided at both longitudinal ends of the back surface (bottom surface in Figure 2) of the insulating substrate 10, a pair of end surface electrodes 15 provided on both longitudinal ends of the insulating substrate 10 and electrically connecting the surface electrode 11 and the back surface electrode 14, and a pair of external electrodes 16 of a two-layer structure provided so as to cover the back surface electrode 14 and the end surface electrode 15.

[0019] The insulating substrate 10 is made of a ceramic substrate mainly composed of alumina, for example. The insulating substrate 10 is obtained by breaking (dividing) a large-sized substrate (described later) along dividing grooves extending in a lattice pattern on the large-sized substrate (see FIG. 4) into a large number of pieces.

[0020] The pair of front electrodes 11 are formed by screen printing an Ag-based paste on the surface of a large-sized substrate, followed by drying and baking.

[0021] Resistor 12 is formed by screen printing resistor paste such as ruthenium oxide on the surface of a large-sized substrate, followed by drying and baking. Both longitudinal ends of resistor 12 overlap with a pair of surface electrodes 11. Although not shown, resistor 12 has a trimming groove formed therein for adjusting the resistance value.

[0022] The protective layer 13 has an undercoat layer 13a that covers the resistor element 12, and an overcoat layer 13b that covers the undercoat layer 13a. The undercoat layer 13a is formed by screen printing a glass paste, drying and baking it. The overcoat layer 13b is formed by screen printing an epoxy resin paste, and heat curing (baking it). The undercoat layer 13a is provided before the trimming groove is formed in the resistor element 12, and the overcoat layer 13b is provided after the trimming groove is formed in the resistor element 12.

[0023] The pair of back electrodes 14 are formed by screen printing a synthetic resin (e.g., epoxy resin) paste containing conductive particles on the back surface of the large-sized substrate and then heat-curing it. The back electrodes 14 are formed so as to extend from the end faces of the insulating substrate 10 toward the center of the insulating substrate 10. The details of the back electrodes 14 will be described later.

[0024] The pair of end electrodes 15 are formed by sputtering nickel (Ni) / chromium (Cr) or the like. The end electrodes 15 electrically connect the front electrode 11 and the back electrode 14, which are separated by the end faces of the insulating substrate 10. The end electrodes 15 extend to a midpoint in the longitudinal direction on the surface of the front electrode 11, exposing the overcoat layer 13b without covering it. The end electrodes 15 extend to a midpoint in the longitudinal direction on the surface of the back electrode 14, covering a portion of the back electrode 14 and exposing the remainder.

[0025] The pair of external electrodes 16 has a Ni plating layer 16a that functions as a barrier layer and a Sn plating layer 16b that functions as an external connection layer. The Ni plating layer 16a is formed by electrolytic plating so as to cover the back electrode 14 and the end electrode 15. The Sn plating layer 16b is formed by electrolytic plating so as to cover the Ni plating layer 16a. The external electrodes 16 are formed so as to cover the end electrode 15 and the back electrode 14 exposed from the end electrode 15.

[0026] Next, a pair of back electrodes 14 of the chip resistor 1 will be described with reference to Fig. 3. Fig. 3 is a plan view showing the back electrode 14 of the chip resistor 1. Note that, in order to make the shape of the back electrode 14 easier to understand, the end electrodes 15 and external electrodes 16 are omitted from the illustration.

[0027] 3, each of the pair of back surface electrodes 14 includes a first back surface electrode 14a and a second back surface electrode 14b. The first back surface electrode 14a is provided on the inner side away from the end surface of the insulating substrate 10. The second back surface electrode 14b is provided on the outer side close to the end surface of the insulating substrate 10 so as to be in contact with (adjacent to) the first back surface electrode 14a.

[0028] The first back surface electrode 14a and the second back surface electrode 14b are both formed in a rectangular shape, and the surface area of ​​the second back surface electrode 14b is larger than the surface area of ​​the first back surface electrode 14a. Moreover, the second back surface electrode 14b is not covered by the first back surface electrode 14a and has its entire surface exposed.

[0029] As described above, the first back electrode 14a and the second back electrode 14b are made of a synthetic resin material containing conductive particles, and both have flexibility, so that they can absorb thermal stress during heat shock. The conductive particles contained in the first back electrode 14a are metal particles (e.g., Ag), and the conductive particles contained in the second back electrode 14b are carbon particles.

[0030] The carbon particle content of the second back surface electrode 14b is lower than the metal particle content of the first back surface electrode 14a. Therefore, the proportion of synthetic resin (e.g., epoxy resin) in the entire second back surface electrode 14b is higher than the proportion of synthetic resin in the entire first back surface electrode 14a, and the second back surface electrode 14b has higher flexibility than the first back surface electrode 14a. Although a part of the second back surface electrode 14b is covered by the end surface electrode 15, the rest is exposed, and therefore the relaxation of thermal stress by the second back surface electrode 14b is not hindered.

[0031] The surface roughness of the first back surface electrode 14a is larger than that of the second back surface electrode 14b, and the first back surface electrode 14a is firmly bonded to the external electrode 16 (Ni plating layer 16a). The electrical resistivity of the first back surface electrode 14a is lower than that of the second back surface electrode 14b (i.e., the electrical conductivity of the first back surface electrode 14a is higher than that of the second back surface electrode 14b). Specifically, the electrical resistivity of the first back surface electrode 14a is approximately 10 -3 [Ω·cm] or less, and the electrical resistivity of the second back surface electrode 14b is set to be approximately 10 -2 The resistivity is set within the range of [Ω·cm] or less. Therefore, a current flows more easily through the first back surface electrode 14a than through the second back surface electrode 14b, and serves as a starting point when forming the external electrode 16 (Ni plating layer 16a) by electrolytic plating in the manufacturing process of the chip resistor 1.

[0032] In this way, the back electrode 14 (first back electrode 14a and second back electrode 14b) absorbs and relieves thermal stress during heat shock, and the first back electrode 14a serves as a starting point for forming the external electrode 16 (Ni plating layer 16a) by electrolytic plating. Therefore, the back electrode 14 enables stable formation of the external electrode 16 while easing thermal stress.

[0033] Next, the manufacturing process of the chip resistor 1 will be described with reference to Figures 4 to 7. Figures 4(a) to (d), Figures 5(e) to (h), and Figure 6(i) are cross-sectional views showing the manufacturing process of the chip resistor 1, and Figure 7 is a flowchart showing the same process.

[0034] First, as shown in step S1 of Fig. 7, a sheet-like large substrate 17 from which a large number of insulating substrates 10 are to be cut is prepared (large substrate preparation process). This large substrate 17 is provided with primary division grooves and secondary division grooves (neither shown) that extend in a lattice pattern, and each of the squares divided by these division grooves becomes one chip formation area. Although Figs. 4 to 6 show cross-sectional views corresponding to one chip formation area, in reality, the steps described below are performed collectively on large substrate 17 corresponding to many chip formation areas.

[0035] 7, an Ag-based paste is screen-printed in the area between the secondary dividing grooves on the surface of the large-sized substrate 17 so as to straddle each of the primary dividing grooves, and then dried and fired. As a result, a pair of surface electrodes 11 facing each other across the chip forming area are formed on the surface of the large-sized substrate 17, as shown in FIG. 4(a) (surface electrode forming process).

[0036] 7, a resistor paste such as ruthenium oxide is screen-printed on the surface of the large-sized substrate 17, and then dried and fired, thereby forming a resistor 12 spanning the pair of surface electrodes 11 as shown in FIG.

[0037] Next, in step S4 of Fig. 7, a glass paste is screen-printed, dried, and fired. As a result, an undercoat layer 13a that covers the resistor 12 is formed (undercoat layer forming step) as shown in Fig. 4(c). Thereafter, a trimming groove (not shown) is formed in the resistor 12 from above the undercoat layer 13a to adjust the resistance value.

[0038] Next, in step S5 of Fig. 7, an epoxy resin paste is screen-printed on the undercoat layer 13a and then heat-cured. As a result, as shown in Fig. 4(d), an overcoat layer 13b is formed that covers a part of the surface electrode 11 and the entire undercoat layer 13a (overcoat layer forming step). The undercoat layer 13a and the overcoat layer 13b form the protective layer 13.

[0039] 7, an epoxy resin paste containing carbon particles is screen-printed and heated to harden in the area between the secondary dividing grooves on the rear surface of the large-sized substrate 17 so as to straddle each of the primary dividing grooves, and then the paste is heated to harden. As a result, as shown in FIG. 5(e), a second rear surface electrode 14b is formed on the outer side of the large-sized substrate 17 (second rear surface electrode forming step).

[0040] Next, in step S7 of Fig. 7, an epoxy resin paste containing metal particles (e.g., Ag) is screen-printed and heat-cured. As a result, as shown in Fig. 5(f), a first back surface electrode 14a is formed on the inner side of the large-sized substrate 17 with respect to the second back surface electrode 14b (first back surface electrode forming step). In this case, the first back surface electrode 14a is formed so as to be in contact with (adjacent to) the second back surface electrode 14b, so that a current can reliably flow to the second back surface electrode 14b via the first back surface electrode 14a.

[0041] The steps up to this point are a batch process for the large-sized substrate 17, but next, the large-sized substrate 17 is primarily broken (primarily divided) along the primary dividing grooves to obtain rectangular substrates 18.

[0042] Thereafter, in step S8 of FIG. 7, Ni—Cr is sputtered on the divided surfaces of the strip-shaped substrates 18. At this time, a plurality of strip-shaped substrates 18 on which the back electrodes 14 are formed are stacked vertically on a predetermined jig. Then, the back electrode 14 of one strip-shaped substrate comes into contact with the overcoat layer 13b of the other strip-shaped substrate arranged below it, forming a predetermined gap on both ends of both strip-shaped substrates, and sputtering is performed on the divided surfaces of these strip-shaped substrates 18. As a result, as shown in FIG. 5(g), end surface electrodes 15 are formed on both end surfaces of the strip-shaped substrate 18 and from both end surfaces to the surfaces of the front surface electrode 11 and the back surface electrode 14 so as to electrically connect them (end surface electrode forming process). The end surface electrodes 15 cover a part of the front surface electrode 11 to expose the remainder, and also cover a part of the back surface electrode 14 (second back surface electrode 14b) to expose the remainder. Moreover, instead of forming the end electrode 15 by sputtering as described above, the end electrode 15 may be formed by dip-coating, for example, an Ag-based paste and then heating and curing it.

[0043] Next, by secondary breaking (secondary division) along the secondary division grooves of the rectangular substrate 18, individual chips 1a having the same size as the chip resistor 1 are obtained.

[0044] Finally, in step S9 of FIG. 7, electrolytic plating is performed twice on the individual chip unit 1a. Specifically, the first electrolytic plating forms a Ni plating layer 16a on the entire surface of the back electrode 14 and the end electrode 15 as shown in FIG. 5(h). In this case, around the back electrode 14, the first back electrode 14a serves as the starting point of electrolytic plating, and a sufficient current flows through the first back electrode 14a, so that the Ni plating layer 16a can be formed to cover the first back electrode 14a. At the same time, a sufficient current also flows through the second back electrode 14b via the first back electrode 14a, so that the Ni plating layer 16a can be formed to cover the second back electrode 14b. Thereafter, the second electrolytic plating forms a Sn plating layer 16b covering the Ni plating layer 16a as shown in FIG. 6(i). The Ni plating layer 16a and the Sn plating layer 16b form a pair of external electrodes 16.

[0045] Next, the mounted state of the chip resistor 1 will be described with reference to Fig. 8. Fig. 8 is a cross-sectional view showing the mounted state of the chip resistor 1.

[0046] As shown in Fig. 8, the chip resistor 1 is mounted on a land 20 provided on a circuit board 19 with the back electrode 14 facing downward. At this time, a pair of external electrodes 16 attached to the back electrode 14 and the end electrode 15 are joined to the corresponding lands 20 via solder 21, so that the chip resistor 1 is surface-mounted on the circuit board 19. At this time, both the first back electrode 14a and the second back electrode 14b, which are flexible, face the circuit board 19. Therefore, even if thermal stress occurs during a heat shock, the thermal stress can be absorbed and alleviated by the first back electrode 14a and the second back electrode 14b.

[0047] The chip resistor 1 configured as above can provide the following advantages.

[0048] The flexibility of both the first back electrode 14a and the second back electrode 14b made of a synthetic resin material containing conductive particles can absorb and reduce thermal stress during a heat shock, thereby improving the heat shock resistance of the chip resistor 1.

[0049] In addition, when the chip resistor 1 is surface-mounted on the circuit board 19, the second back electrode 14b, which has high flexibility, is disposed on the side where the amount of solder 21 that joins them is relatively large, that is, on the outer side close to the end face of the insulating substrate 10. This makes it possible to effectively absorb the thermal stress that the solder 21 receives during a heat shock. Furthermore, since the surface area of ​​the second back electrode 14b is larger than the surface area of ​​the first back electrode 14a, the second back electrode 14b can extremely effectively relieve the thermal stress.

[0050] Moreover, since the electrical resistivity of the first back surface electrode 14a is lower than that of the second back surface electrode 14b, the first back surface electrode 14a serves as a starting point for forming the external electrode 16 (Ni plating layer 16a) by electrolytic plating in the manufacturing process of the chip resistor 1. Therefore, the external electrode 16 can be stably formed around the back surface electrode 14. In particular, since the first back surface electrode 14a is provided on the inner side away from the end face of the insulating substrate 10, the external electrode 16 can be stably formed even on the inner side of the insulating substrate 10 where it is difficult to form the external electrode 16 by electrolytic plating.

[0051] Furthermore, although a current does not flow easily through the second back surface electrode 14b that relieves thermal stress as described above compared to the first back surface electrode 14a during electrolytic plating, a sufficient current can be passed through the second back surface electrode 14b via the first back surface electrode 14a. Therefore, the external electrode 16 can be stably formed around the second back surface electrode 14b as well.

[0052] Thus, in the chip resistor 1, the second back surface electrode 14b can alleviate thermal stress during heat shock, and the first back surface electrode 14a can stably form the external electrode 16 during electrolytic plating.

[0053] In addition, since both the first back electrode 14a and the second back electrode 14b are made of synthetic resin material, the difference in thermal expansion coefficient between the two can be made smaller and thermal stress during heat shock can be suppressed compared to when the first back electrode 14a is made of baked silver and the second back electrode 14b is made of synthetic resin material. In addition, since the bonding strength between the synthetic resins is high, the occurrence of cracks at the interface between the two can be suppressed.

[0054] Furthermore, since the first back surface electrode 14a is firmly bonded to the external electrode 16 (Ni plating layer 16a), even if the back surface electrode 14 includes the second back surface electrode 14b that relieves thermal stress, peeling of the Ni plating layer 16a from the back surface electrode 14 can be prevented.

[0055] In the first embodiment, the first back surface electrode 14a is formed on the inner side of the insulating substrate 10 relative to the second back surface electrode 14b, but the present invention is not limited to this configuration. The first back surface electrode 14a only needs to be formed on at least the inner side of the insulating substrate 10, and for example, the first back surface electrode 14a may be formed in a channel shape (U-shape) so as to surround the periphery of the second back surface electrode 14b. Even in this case, the same effects as those of the first embodiment can be achieved.

[0056] Second embodiment Next, a chip resistor 2 according to a second embodiment will be described with reference to Fig. 9. Fig. 9 is a cross-sectional view of the chip resistor 2 according to the second embodiment. The chip resistor 2 differs from the first embodiment in that the first back surface electrode 14a covers a portion of the second back surface electrode 14b.

[0057] As shown in FIG. 9, the first back surface electrode 14a is formed by screen printing a synthetic resin (e.g., epoxy resin) paste containing metal particles (e.g., Ag) on ​​the back surface of a large-sized substrate multiple times and then heating and hardening the paste. The first back surface electrode 14a protrudes downward from the second back surface electrode 14b and covers the inner end of the second back surface electrode 14b. The film thickness T1 of the first back surface electrode 14a is larger than the film thickness T2 of the second back surface electrode 14b. Since most of the second back surface electrode 14b is exposed without being covered by the first back surface electrode 14a, the second back surface electrode 14b sufficiently relieves thermal stress during heat shock.

[0058] In the manufacturing process of such a chip resistor 2, when the back electrode forming process (second back electrode forming process and first back electrode forming process) is completed, the back electrode 14 has a step portion 14c having a size corresponding to the difference between the film thicknesses T1 and T2. When performing sputtering in the end electrode forming process, similarly to the first embodiment, if a plurality of strip-shaped substrates (see FIG. 4(g)) are stacked vertically on a predetermined jig, a sufficient gap is ensured by the step portion 14c on both ends of the two strip-shaped substrates that contact each other vertically. Therefore, the second back electrode 14b of the upper strip-shaped substrate and the front electrode 11 of the lower strip-shaped substrate are sufficiently separated from each other. Therefore, the end electrodes 15 can be easily formed by sputtering so as to wrap around from both end faces of the strip-shaped substrate to the front surface of the front electrode 11 and the front surface of the back electrode 14.

[0059] The chip resistor 2 thus configured can achieve the same effect as the first embodiment. In addition, when performing sputtering in the end face electrode forming process, a sufficient gap can be secured between the surface of the second back surface electrode 14b of one of the multiple strip-shaped substrates (insulating substrates) stacked vertically and the surface electrode 11 of the other strip-shaped substrate arranged below it. This can prevent the second back surface electrode 14b of one strip-shaped substrate from adhering to the surface electrode 11 of the other strip-shaped substrate. In particular, since the second back surface electrode 14b is made of a synthetic resin material containing carbon particles and is therefore easily attached to other substrates, this effect is extremely beneficial.

[0060] Furthermore, since a sufficient gap is ensured as described above when sputtering both end faces of the rectangular substrate, the end electrodes 15 can be easily formed so as to wrap around from both end faces of the rectangular substrate to the surfaces of the front electrode 11 and the back electrode 14. Therefore, the end electrodes 15 can be formed sufficiently on the inner side away from the end faces of the rectangular substrate.

[0061] Furthermore, since the first back surface electrode 14a covers the inner end of the second back surface electrode 14b, it is possible to facilitate flow of current from the first back surface electrode 14a to the second back surface electrode 14b during electrolytic plating.

[0062] (Modification) Next, a chip resistor 2-1 according to a modification of the second embodiment will be described with reference to Fig. 10. Fig. 10 is a cross-sectional view of the chip resistor 2-1 according to the modification. The chip resistor 2-1 differs from the second embodiment in that the film thickness of the first back surface electrode 14a is slightly thicker than the film thickness of the second back surface electrode 14b.

[0063] 10, the first back surface electrode 14a thinly covers the inner end portion of the second back surface electrode 14b. The film thickness of the first back surface electrode 14a is slightly larger than the film thickness of the second back surface electrode 14b.

[0064] According to the chip resistor 2-1 configured in this manner, it is possible to minimize the amount of the first back surface electrode 14a required while making it easier to pass current from the first back surface electrode 14a to the second back surface electrode 14b during electrolytic plating.

[0065] In the second embodiment, the first back electrode 14a and the second back electrode 14b are made of different materials, but the present invention is not limited to this configuration, and both electrodes may be made of the same material. In this case, the resistance value [Ω] of the first back electrode 14a can be made smaller than the resistance value [Ω] of the second back electrode 14b by making the film thickness T1 of the first back electrode 14a larger than the film thickness T2 of the second back electrode 14b. This configuration can facilitate the manufacture of the chip resistor, and can facilitate the flow of current from the first back electrode 14a to the second back electrode 14b during electrolytic plating.

[0066] Third embodiment Next, a chip resistor 3 according to a third embodiment will be described with reference to Fig. 11. Fig. 11 is a cross-sectional view of the chip resistor 3 according to the third embodiment. The chip resistor 3 differs from the first embodiment in that the first back surface electrode 14a has a portion interposed between the insulating substrate 10 and the second back surface electrode 14b.

[0067] 11, the first back surface electrode 14a is provided on the back surface of the insulating substrate 10 so as to extend inward from its end face. The second back surface electrode 14b is provided on the front surface of the first back surface electrode 14a so as to extend inward from its end face. The second back surface electrode 14b covers most of the first back surface electrode 14a and leaves the remainder exposed.

[0068] In the manufacturing process of the chip resistor 3, after the overcoat layer formation process described in the first embodiment above (see step S5 in Figure 7), a first back surface electrode formation process (see step S7 in Figure 7) is performed, and then a second back surface electrode formation process (see step S6 in Figure 7) is performed.

[0069] The chip resistor 3 configured in this manner can achieve the same effects as those of the first embodiment. In addition, since the entire surface of the second back surface electrode 14b on the first back surface electrode 14a side is in contact with the first back surface electrode 14a, it is possible to make it easier to pass a current from the first back surface electrode 14a to the second back surface electrode 14b during electrolytic plating.

[0070] (Modification) Next, a chip resistor 3-1 according to a modification of the second embodiment will be described with reference to Fig. 12. Fig. 12 is a cross-sectional view of the chip resistor 3-1 according to the modification. The chip resistor 3-1 differs from the third embodiment in that the second back electrode 14b is in contact with the insulating substrate 10 on the outer side of the insulating substrate 10.

[0071] As shown in Fig. 12, the first back surface electrode 14a is provided on the inner side from the end face of the insulating substrate 10 at a predetermined distance D. In other words, the first back surface electrode 14a is not formed across the primary division groove extending on the large-sized substrate (see Fig. 4). The second back surface electrode 14b contacts the insulating substrate 10 on the outer side of the insulating substrate 10, covers a part of the first back surface electrode 14a on the inner side of the insulating substrate 10, and leaves the remainder exposed.

[0072] According to the chip resistor 3-1 configured in this manner, the first back electrode 14a is not formed across the primary division groove extending on the large-sized substrate, making it easier to perform a primary break (primary division) of the large-sized substrate along the primary division groove during the manufacturing process of the chip resistor 3.

[0073] The present invention is not limited to the above-mentioned embodiment and modifications, 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 and modifications are preferred examples, 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.

[0074] For example, in the first embodiment, the first back surface electrode 14a and the second back surface electrode 14b are in contact with each other, but this is not limited to the configuration. In the manufacturing process of the chip resistor 1, the first back surface electrode 14a and the second back surface electrode 14b may be arranged adjacent to each other within a range where the Ni plating layer 16a can be sufficiently formed by electrolytic plating so as to cover the back surface electrode 14. The second back surface electrode 14b arranged in this manner is also included in the second back surface electrode constituting the present invention.

[0075] In addition, in the above embodiment, the metal particles contained in the first back surface electrode 14a are described as being, for example, Ag, but this configuration is not limited to this, and various metal particles having electrical conductivity (for example, Cu, etc.) can be used.

[0076] In the above embodiment, the second back electrode 14b is made of a synthetic resin material containing carbon particles, but is not limited to this. As long as the electrical resistivity of the first back electrode 14a is within a range smaller than that of the second back electrode 14b, the synthetic resin material of the second back electrode 14b may contain metal particles (e.g., Ag) in addition to carbon particles.

[0077] In the above embodiment, the synthetic resin contained in the back electrode 14 is described as being an epoxy resin, but the present invention is not limited to this configuration, and various synthetic resins having flexibility (such as phenolic resin) can be used.

[0078] Furthermore, in the above embodiment, the first back electrode 14a and the second back electrode 14b are configured to use the same type of synthetic resin material (e.g., epoxy resin), but this is not limited thereto, and different types of synthetic resin materials may be used. For example, the first back electrode 14a may be made of epoxy resin, and the second back electrode 14b may be made of phenol resin.

[0079] In addition, in the above embodiment, the second back surface electrode 14b is configured to be more flexible than the first back surface electrode 14a, but this is not limited to the above, and the flexibility of the first back surface electrode 14a may be made greater than the flexibility of the second back surface electrode 14b. [Explanation of symbols]

[0080] 1,2,3,2-1,3-1 Chip resistors 10 Insulating substrate 11 Surface electrode 12 Resistor 14 Back electrode 14a First rear electrode 14b 2nd back electrode 15 End electrode 16 External electrode

Claims

1. A rectangular insulating substrate; a pair of surface electrodes provided at both ends in a longitudinal direction on a surface of the insulating substrate; a resistor provided across the pair of surface electrodes; a pair of back electrodes provided at both longitudinal ends of a back surface of the insulating substrate and made of a synthetic resin material containing conductive particles; a pair of end surface electrodes provided on both longitudinal end surfaces of the insulating substrate and electrically connecting the front surface electrode and the back surface electrode; an external electrode formed by electrolytic plating so as to cover the back surface electrode and the end surface electrode; The back electrode is a first back electrode provided on an inner side away from at least an end surface of the insulating substrate; a second back surface electrode provided on an outer side near an end surface of the insulating substrate so as to be adjacent to the first back surface electrode; A chip resistor, wherein the electrical resistivity of the first back surface electrode is lower than the electrical resistivity of the second back surface electrode.

2. 2. The chip resistor according to claim 1, The chip resistor, wherein the first back surface electrode covers a portion of the second back surface electrode.

3. 2. The chip resistor according to claim 1, A chip resistor, wherein the first back surface electrode has at least a portion interposed between the insulating substrate and the second back surface electrode.

4. 4. The chip resistor according to claim 3, the first back electrode is provided on the insulating substrate, The chip resistor, wherein the second back surface electrode is provided on the first back surface electrode.

5. 4. The chip resistor according to claim 3, The chip resistor, wherein the second back electrode is in contact with the insulating substrate on an outer side of the insulating substrate.

6. The chip resistor according to any one of claims 1 to 5, the conductive particles contained in the first back surface electrode are metal particles, The chip resistor, wherein the conductive particles contained in the second back electrode are carbon particles.

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