Circuit substrate and electronic device

Abstract

To suppress peeling-off of a glass layer.SOLUTION: A circuit substrate 10 includes a substrate body 11, a pair of electrodes 41, 42, a resistive element 60, and a glass layer 70. The substrate body 11 is made of a ceramic. The pair of electrodes 41, 42 are spaced apart from each other on the substrate body 11. The resistive element 60 is positioned so as to cross the pair of electrode 41, 42. The glass layer 70 covers the pair of electrode 41, 42 and the resistive element 60. When in an area where the resistive element 60 and the glass layer 70 are arranged on the substrate body 11 between the pair of electrodes 41, 42, an area centered between the pair of electrodes 41, 42 is defined as a central part, a minimal distance T2 between the substrate body 11 and a surface of the glass layer 70 at the central part is shorter than a minimal distance T1 between the surface of the glass layer 70 and the substrate body 11 at a periphery P of the resistive element 60 located on the electrodes 41, 42.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to circuit boards and electronic devices. [Background technology]

[0002] Substrates made of ceramics have excellent insulating properties and thermal conductivity, and are therefore often used as circuit boards.

[0003] Patent Document 1 discloses a wiring board having a resistor that straddles a first wiring layer and a second wiring layer, and in which the first wiring layer, the second wiring layer, and the resistor are covered with a glass layer (overcoat glass). Patent Document 1 also describes a technique for adjusting the resistance value of the resistor by trimming a part of the resistor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2000-208895 A Summary of the Invention

[0005] A circuit board according to an embodiment of the present disclosure includes a substrate body, a pair of electrodes, a resistor, and a glass layer. The substrate body is made of ceramics. The pair of electrodes are spaced apart on the substrate body. The resistor is positioned so as to straddle the pair of electrodes. The glass layer covers the pair of electrodes and the resistor. In addition, when a region located at the center between the pair of electrodes among a region where the resistor and the glass layer are located on the substrate body between the pair of electrodes is defined as a central portion, the shortest distance between the substrate body and a surface of the glass layer in the central portion is shorter than the shortest distance between the substrate body and a surface of the glass layer at a periphery of the resistor located on the electrode. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic side view of the lighting device according to the first embodiment. [Diagram 2] FIG. 2 is a schematic perspective view of the socket according to the first embodiment. [Diagram 3] FIG. 3 is a schematic plan view of the circuit board according to the first embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view taken along line IV-IV in FIG. [Diagram 5] FIG. 5 is a schematic cross-sectional view of a circuit board according to the second embodiment. [Figure 6] FIG. 6 is a schematic cross-sectional view of a circuit board according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Hereinafter, a detailed description will be given of a form for carrying out a circuit board and an electronic device according to the present disclosure (hereinafter, referred to as an "embodiment") with reference to the drawings. Note that the circuit board and the electronic device according to the present disclosure are not limited to the embodiment. In addition, each embodiment can be appropriately combined as long as the processing contents are not contradictory. In addition, the same parts in each of the following embodiments are given the same reference numerals, and duplicated explanations are omitted.

[0008] In addition, in the embodiments described below, expressions such as "constant", "orthogonal", "vertical" and "parallel" may be used, but these expressions do not necessarily mean "constant", "orthogonal", "vertical" and "parallel" strictly. In other words, each of the above expressions allows for deviations due to, for example, manufacturing accuracy and installation accuracy.

[0009] In addition, in order to make the explanation easier to understand, each of the drawings referred to below may show an orthogonal coordinate system that defines an X-axis direction, a Y-axis direction, and a Z-axis direction that are perpendicular to each other, and has the positive Z-axis direction as the vertically upward direction.

[0010] In the embodiment described below, an example will be described in which a circuit board according to the present disclosure is applied to a lighting device, which is an example of an electronic device.

[0011] A circuit board is known that has a ceramic substrate, two wiring layers on the substrate, a resistor that electrically connects the two wiring layers, and a glass layer that covers the wiring layers and the resistor. In this type of circuit board, a technique is known for adjusting the resistance value of the resistor by trimming a part of the resistor.

[0012] The above-mentioned conventional techniques have room for further improvement in terms of preventing peeling of the glass layer. Therefore, it is desired to provide a circuit board and an electronic device capable of preventing peeling of the glass layer.

[0013] (First embodiment) First, the configuration of the lighting device according to the first embodiment will be described with reference to Fig. 1 to Fig. 3. Fig. 1 is a schematic side view of the lighting device according to the first embodiment. Fig. 2 is a schematic perspective view of a socket according to the first embodiment. Fig. 3 is a schematic plan view of a circuit board according to the first embodiment.

[0014] 1, the lighting device 1 according to the first embodiment includes a circuit board 10, a socket 20 that houses the circuit board 10, and a plurality of conductive terminals 30 that are connected to the circuit board 10. The lighting device 1 according to the embodiment is used, for example, as an in-vehicle lighting device. For example, the lighting device 1 is used as a light source for a rear lamp, a turn lamp, a position lamp, a fog lamp, etc.

[0015] (About sockets) As shown in FIGS. 1 and 2, the socket 20 may have a housing portion 21, a flange portion 22, and a plurality of heat dissipation fins 23.

[0016] The accommodation portion 21 may be, for example, a cylindrical portion with a bottom having a generally circular outer shape in a plan view. The accommodation portion 21 may be located on a surface opposite to a surface on which a plurality of heat dissipation fins 23 of the flange portion 22 described later are located. The accommodation portion 21 may have a recess 210 recessed from one end surface of the socket 20, specifically, from a surface opposite to a surface of the accommodation portion 21 that contacts the flange portion 22, toward the other end side of the socket 20. The circuit board 10 may be accommodated in such a recess 210.

[0017] The recess 210 may have a plurality of sidewalls 211. The plurality of sidewalls 211 may have, for example, an arched shape in a plan view. In this case, the plurality of sidewalls 211 may be arranged along the circumferential direction around the circuit board 10 so as to surround the circuit board 10. A gap 212 may be provided between each two sidewalls 211 adjacent to each other in the circumferential direction.

[0018] The flange portion 22 may be, for example, a disk-shaped portion. The flange portion 22 may be located between the accommodation portion 21 and the plurality of heat dissipation fins 23. The flange portion 22 may have a larger diameter than the accommodation portion 21, and may be configured to abut against the periphery of a mounting hole provided in a vehicle body when the lighting device 1 is inserted into the mounting hole. For example, a bayonet (not shown) for a twist lock is located on the outer circumferential surface of the accommodation portion 21, and by rotating the socket 20 with the flange portion 22 abutting against the periphery of the mounting hole, the bayonet fits into a groove on the vehicle body side, and the lighting device 1 is fixed to the vehicle body.

[0019] The plurality of heat dissipation fins 23 may be located on the surface of the flange portion 22 opposite to the surface on which the accommodation portion 21 is located. In this case, heat generated in the circuit board 10 is mainly dissipated from the plurality of heat dissipation fins 23. Here, an example is shown in which the socket 20 has four heat dissipation fins 23, but the number of heat dissipation fins 23 included in the socket 20 is not limited to four.

[0020] A heat transfer member (not shown) made of a metal such as aluminum may be located between the bottom of recess 210 and circuit board 10. The heat transfer member is located so as to be in contact with circuit board 10 and the bottom of recess 210, and transfers heat generated in circuit board 10 to heat dissipation fins 23.

[0021] (About the circuit board) 3, the circuit board 10 has a substrate body 11 made of ceramics. The substrate body 11 may be, for example, a flat member having a first surface on which a circuit is formed, a second surface opposite the first surface, and a plurality of third surfaces (side surfaces) connected to each of the first and second surfaces. The substrate body 11 is stored in the storage section 21 with the second surface facing the bottom surface of the recess 210, in other words, with the first surface on which a circuit is formed facing outward.

[0022] For example, ceramics such as aluminum oxide ceramics, zirconium oxide ceramics, composite ceramics of aluminum oxide and zirconium oxide, silicon nitride ceramics, aluminum nitride ceramics, silicon carbide ceramics, and mullite ceramics may be used as the substrate body 11. The substrate body 11 made of aluminum oxide ceramics has excellent workability while having the mechanical strength required for the substrate body 11. Furthermore, the substrate body 11 made of aluminum nitride ceramics has high thermal conductivity and therefore excellent heat dissipation properties.

[0023] (About wiring) Wiring 40 mainly composed of a metal such as copper and silver may be located on the first surface of the substrate body 11. The wiring 40 is electrically connected to the conductive terminal 30 via a conductive joining member (not shown) such as a brazing material or solder.

[0024] A light-emitting element 50, which is an example of an electronic component, may be located on the wiring 40. The light-emitting element 50 is, for example, an LED (Light Emitting Diode) or an LD (Laser Diode). The wiring 40 electrically connects the conductive terminal 30 and the light-emitting element 50.

[0025] A pair of electrodes 41, 42 may be located in the middle of the wiring 40 (a part between the conductive terminal 30 and the light emitting element 50). The pair of electrodes 41, 42 may be located on the substrate body 11 with a gap therebetween. The pair of electrodes 41, 42 may extend parallel to each other. Note that here, an example is shown in which the pair of electrodes 41, 42 extend along the Y-axis direction. The pair of electrodes 41, 42 are, for example, a part of the wiring 40. The pair of electrodes 41, 42 may be formed of the same material as the wiring 40 (for example, copper, silver, etc.). Note that the pair of electrodes 41, 42 may contain glass in order to improve the bonding with the substrate body 11.

[0026] (Regarding resistors) A resistor 60 may be located between the pair of electrodes 41, 42. The resistor 60 has a higher electrical resistance than the wiring 40, and adjusts the voltage applied to the light-emitting element 50.

[0027] The resistor 60 may contain a conductive component and a resistance value adjusting component. Specifically, the resistor 60 may contain lanthanum hexaboride (LaB6) as a conductive component. Note that lanthanum hexaboride does not necessarily have to be the main component of the resistor 60. The resistor 60 may contain, for example, Cu, Ni, Al, Sn, Pd, Ru, RuO2, Ag, Bi2Ru2O7, Pd2Ru2O6, SrRuO3, CaRuO3, BaRuO3, Ta, TaN, Ta2N, WC, MoSi2, TaSi2, SnO2, and Ta2O5 as a conductive component other than lanthanum hexaboride. The resistor 60 may also contain, for example, glass as a resistance value adjusting component.

[0028] (About the glass layer) A glass layer 70 may be located on the pair of electrodes 41, 42 and the resistor 60. The glass layer 70 covers the resistor 60, thereby suppressing oxidation of the resistor 60. Therefore, by placing the glass layer 70 on the resistor 60, the electrical reliability of the resistor 60 can be improved.

[0029] The glass layer 70 may be made of, for example, a material mainly composed of R2O-B2O3-SiO2 (R: alkali metal element), R2O-SiO2-B2O3-Bi2O3 (R: alkali metal element), or R'O-B2O3-SiO2 (R': alkaline earth metal element). The glass layer 70 may also contain, for example, titanium oxide (TiO2) and zirconium oxide (ZrO2). In this case, the reflectance of the glass layer 70 can be improved.

[0030] Here, a specific configuration of the glass layer 70 according to the first embodiment will be described with reference to Fig. 4. Fig. 4 is a schematic cross-sectional view taken along line IV-IV in Fig. 3.

[0031] 4, the resistor 60 is located so as to straddle the pair of electrodes 41, 42. The glass layer 70 may be located so as to entirely cover the pair of electrodes 41, 42 and the resistor 60.

[0032] Here, the inventors of the present application have confirmed that in a circuit board equipped with a resistor containing lanthanum hexaboride, peeling of the glass layer occurs more frequently near the outer periphery of the resistor, where the resistor and the electrodes overlap, than in other locations. This is believed to be due to the effect of the reduction action of lanthanum hexaboride. That is, lanthanum hexaboride is known as a thermionic emitter, and emits electrons when heated. It is believed that the emitted electrons reduce the surrounding metal components, causing the peeling of the glass layer.

[0033] Specifically, when the circuit board is heated during the manufacturing process, the temperature near the electrodes containing Cu, which has a relatively high thermal conductivity, becomes higher than the temperature at other locations. This causes the temperature at the outer periphery of the resistor to become higher than the temperature at other locations. As a result, more electrons are emitted from the outer periphery of the resistor.

[0034] In a region of the electrode in contact with the resistor, electrons emitted from the resistor are supplied to the electrode, causing the following reduction reaction in the electrode. CuO+2e - →Cu+O 2- The Cu element generated by the reduction reaction has a lower affinity with glass, which is an oxide, than CuO, and therefore the adhesion strength between the electrode and the glass layer is weakened in the region of the electrode that contacts the resistor, i.e., near the outer periphery of the resistor, making the glass layer more likely to peel off from the electrode.

[0035] In addition, in the region of the glass layer that contacts the resistor, particularly near the outer periphery of the resistor from which many electrons are emitted, the electrons emitted from the resistor are supplied to the glass layer, causing the following reduction reaction in the glass layer. SiO2+4e - →Si+2O 2- The Si element generated by the reduction reaction has a lower affinity with the resistor (lanthanum hexaboride) than SiO2, which weakens the adhesive strength between the resistor and the glass layer at the periphery of the resistor, making the glass layer more likely to peel off from the resistor.

[0036] Therefore, in the circuit board 10 according to the first embodiment, the thickness of the glass layer 70 at the outer periphery of the resistor 60 may be made thicker than the thickness of the glass layer 70 at the center of the resistor 60. This makes it possible to suitably suppress peeling of the glass layer 70.

[0037] That is, for example, peeling of the glass layer 70 can be suppressed to some extent by making the glass layer 70 thicker overall. This is because the weight of the glass layer 70 increases by the amount of the thickening of the glass layer 70, making it easier to physically suppress peeling.

[0038] On the other hand, the thermal stress caused by the difference in thermal expansion coefficient between the electrodes 41, 42 and the resistor 60 and the glass layer 70 increases as the glass layer 70 becomes thicker. This thermal stress may weaken the effect of preventing peeling by the weight of the glass layer 70 described above.

[0039] Here, the weight of the glass layer 70 in the center of the resistor 60 is not directly applied to the outer periphery of the resistor 60. In other words, the contribution of increasing the thickness of the glass layer 70 in the center of the resistor 60 to the effect of suppressing peeling is small. In addition, the thermal stress increases by the amount of the thickness of the glass layer 70 in the center of the resistor 60, which results in the weight of the glass layer 70 rather weakening the effect of suppressing peeling.

[0040] In contrast, according to the circuit board 10 of the first embodiment, it is possible to suppress an unnecessary increase in thermal stress by making the thickness of the glass layer 70 relatively thin at the center of the resistor 60. Therefore, the circuit board 10 of the first embodiment can suitably suppress peeling of the glass layer 70.

[0041] In addition, in the circuit board, in order to adjust the resistance value of the resistor, for example, after product shipment, the resistor may be subjected to trimming. Trimming is a method of adjusting the resistance value of the resistor by forming a groove by a laser or the like in the center part of the resistor or in its vicinity to narrow the resistance width of the resistor. According to the circuit board 10 of the first embodiment, the thickness of the glass layer 70 in the center part of the resistor 60 is relatively thin, so that peeling of the glass layer 70 can be suitably suppressed while ensuring the ease of trimming. Furthermore, according to the circuit board 10 of the first embodiment, the thickness of the glass layer 70 in the center part of the resistor 60 is relatively thin, so that the material cost required for the glass layer 70 can be suppressed.

[0042] In order to make the thickness of the glass layer 70 on the outer periphery of the resistor 60 relatively thicker, the number of times that the glass layer 70 is applied to the outer periphery of the resistor 60 may be relatively increased. For example, after applying one layer of glass to the pair of electrodes 41, 42 and the resistor 60, another layer of glass may be applied to the outer periphery of the resistor 60. At this time, by using a mask member having an opening at a position corresponding to the outer periphery of the resistor 60, the glass can be appropriately applied only to the outer periphery of the resistor 60.

[0043] The thickness of the glass layer 70 will be described in more detail. As shown in FIG. 4, the thickness T1 of the glass layer 70 at the position where the electrode 41 (42), the resistor 60, and the glass layer 70 contact each other, specifically, at the periphery P of the resistor 60 located on the electrode 41 (42), may be thicker than the thickness T2 of the glass layer 70 at the center of the resistor 60. The position where the electrode 41 (42), the resistor 60, and the glass layer 70 contact each other is more likely to peel off due to thermal stress than other positions. Therefore, by increasing the thickness of the glass layer 70 at the position where the above three contact each other, particularly among the outer periphery of the resistor 60, the peeling of the glass layer 70 can be more suitably suppressed.

[0044] The thickness T3 of the glass layer 70 located only on the electrode 41 (42) may be thinner than the thickness T4 of the glass layer 70 at the outer periphery of the resistor 60. Specifically, the thickness T3 is, for example, the thickness of the glass layer 70 at the center of the electrode 41 (42). The thickness T4 is, for example, the thickness of the glass layer 70 at the position where the total thickness of the electrode 41 (42) and the resistor 60 is the thickest. The position where the total thickness of the electrode 41 (42) and the resistor 60 is the thickest is the position where stress due to repeated thermal expansion and thermal contraction is most likely to be applied. By increasing the thickness T4 of the glass layer 70 at such a position, peeling of the glass layer 70 can be suitably suppressed. In addition, the electrode 41 (42) containing Cu has a higher thermal conductivity than the resistor 60. Therefore, by making the thickness T3 of the glass layer 70 located only on the electrode 41 (42) relatively thin, the heat transferred from the resistor 60 to the electrode 41 (42) can be efficiently released to the outside.

[0045] As an example, the thickness of electrodes 41, 42 may be 10 μm or more and 30 μm or less, the thickness of resistor 60 may be 15 μm or more and 35 μm or less, and the thickness of glass layer 70 may be 10 μm or more and 40 μm or less. The thicknesses of electrodes 41, 42, resistor 60, and glass layer 70 can be determined, for example, by cutting circuit board 10 so as to obtain cross sections of electrodes 41, 42, resistor 60, and glass layer 70, and observing the cut surfaces using a SEM (scanning electron microscope).

[0046] The void fraction in the center of the resistor 60 may be higher than the void fraction in the outer periphery of the resistor 60. As described above, trimming may be performed near the center of the resistor 60. By making the void fraction in the center of the resistor 60 higher than the void fraction in the outer periphery, the ease of trimming can be improved.

[0047] Furthermore, the resistor 60 may have voids in the outer periphery. By having voids in the outer periphery of the resistor 60, thermal stress occurring near the outer periphery of the resistor 60 is alleviated, and the reliability of the circuit board 10 can be improved.

[0048] The resistor 60 is formed after the electrode 41 (42) is formed on the substrate body 11. When the electrode 41 (42) is heated during the formation of the resistor 60, gas present in the resistor 60 near the electrode 41 (42) is easily released and sintering is promoted, which is thought to result in a relatively low void ratio in the outer periphery of the resistor 60.

[0049] The void diameter in the center of resistor 60 may be larger than the void diameter in the outer periphery of resistor 60. By making the void diameter in the center of resistor 60 larger than the void diameter in the outer periphery, the ease of trimming can be improved.

[0050] The void fraction of resistor 60 can be obtained, for example, as follows. First, circuit board 10 is cut so as to obtain a cross section of resistor 60, and the cut surface is observed using SEM to capture an image at a predetermined magnification. Then, the obtained image (SEM image) is subjected to image processing to calculate the total area of ​​voids relative to the area of ​​the entire image, thereby obtaining the void fraction of resistor 60.

[0051] As an example, the void ratio of the resistor 60 may be 5% by area or more and 40% by area or less. As an example, the void diameter (equivalent circle diameter) at the center of the resistor 60 may be 5 μm or more and 11 μm or less, and the void diameter (equivalent circle diameter) at the outer periphery of the resistor 60 may be 3 μm or more and 6 μm or less. The equivalent circle diameter of the voids can also be obtained by analyzing the SEM image. For example, the voids are traced in the SEM image, and the traced image is subjected to image analysis using a particle analysis method of the image analysis software "Azo-kun" (registered trademark, manufactured by Asahi Kasei Engineering Co., Ltd.; hereinafter, when the image analysis software "Azo-kun" is referred to, it refers to the image analysis software manufactured by Asahi Kasei Engineering Co., Ltd.), to calculate the average value of the equivalent circle diameter of the voids.

[0052] Second embodiment Next, the configuration of the circuit board according to the second embodiment will be described with reference to Fig. 5. Fig. 5 is a schematic cross-sectional view of the circuit board according to the second embodiment.

[0053] 5, the circuit board 10A according to the second embodiment may have a resistor 60A and a glass layer 70A. Trimming grooves 80 that vertically penetrate the resistor 60A and the glass layer 70A may be formed in the resistor 60A and the glass layer 70A. The trimming grooves 80 are formed to adjust the resistance value of the resistor 60A.

[0054] The trimming groove 80 may be located in the center of the resistor 60A. The center of the resistor 60A means the center in the cross-sectional view shown in FIG. 5, that is, the center in the arrangement direction of the pair of electrodes 41, 42 (here, the X-axis direction). The position of the trimming groove 80 does not need to be strictly in the center of the resistor 60A, and may be slightly shifted from the center of the resistor 60A. The trimming groove 80 extends linearly in parallel to the pair of electrodes 41, 42, for example. The trimming groove 80 may also be L-shaped, having a portion extending linearly in parallel to the pair of electrodes 41, 42 and a portion extending in a direction perpendicular to the pair of electrodes 41, 42, for example.

[0055] Furthermore, the circuit board 10A according to the second embodiment may have a resin layer 90. In the second embodiment, the resin layer 90 covers all of the pair of electrodes 41, 42, the resistor 60A, and the glass layer 70A. The inside of the trimming groove 80 is filled with resin.

[0056] In this manner, by further positioning the resin layer 90 on the glass layer 70A, the weight of the resin layer 90 can enhance the effect of physically suppressing peeling.

[0057] Furthermore, in the circuit board 10A according to the second embodiment, the total thickness T5 of the glass layer 70A and the resin layer 90 at the outer periphery of the resistor 60A, specifically, at the periphery P of the resistor 60, may be thicker than the total thickness T6 of the glass layer 70A and the resin layer 90 at the center of the resistor 60A. By making the total thickness T6 of the glass layer 70A and the resin layer 90 at the center of the resistor 60A relatively thin in this manner, an unnecessary increase in thermal stress is suppressed, and peeling of the glass layer 70A can be suitably suppressed.

[0058] For example, the thickness of resin layer 90 is 10 μm or more and 40 μm or less. The thickness of resin layer 90 can be determined, for example, by cutting circuit board 10A so as to obtain cross sections of electrodes 41, 42, resistor 60A, glass layer 70A, and resin layer 90, and observing the cut surface using an SEM.

[0059] Third embodiment Next, the configuration of a circuit board according to a third embodiment will be described with reference to Fig. 6. Fig. 6 is a schematic cross-sectional view of the circuit board according to the third embodiment.

[0060] 6, the circuit board 10B according to the third embodiment may have a resin layer 90B. The resin layer 90B according to the third embodiment may cover only a part of the pair of electrodes 41, 42, the resistor 60A, and the glass layer 70A, including the center of the resistor 60A. Specifically, the resin layer 90B may be located inside the area sandwiched between the periphery P of the resistor 60A located on one electrode 41 and the periphery P of the resistor 60A located on the other electrode 42.

[0061] In this way, it is sufficient that the resin layer 90B covers at least the trimming groove 80, and it is not necessary for the resin layer 90B to cover the pair of electrodes 41, 42, the resistor 60A, and the glass layer 70A entirely.

[0062] Furthermore, in the circuit board 10B according to the third embodiment, the total thickness T7 (corresponding to the thickness T1 of the glass layer 70A at the periphery P) of the glass layer 70A and the resin layer 90B at the electrode 41 (42) of the resistor 60 may be thicker than the total thickness T8 of the glass layer 70A and the resin layer 90B at the center of the resistor 60A. By making the total thickness T8 of the glass layer 70A and the resin layer 90B at the center of the resistor 60A relatively thin in this manner, an unnecessary increase in thermal stress is suppressed, and peeling of the glass layer 70A can be suitably suppressed.

[0063] As described above, the circuit board according to the embodiment (for example, circuit boards 10, 10A, 10B) has a substrate body (for example, substrate body 11), a pair of electrodes (for example, a pair of electrodes 41, 42), a resistor (for example, resistors 60, 60A), and a glass layer (for example, glass layers 70, 70A). The substrate body is made of ceramics. The pair of electrodes are positioned at a distance from each other on the substrate body. The resistor is positioned so as to straddle the pair of electrodes. The glass layer covers the pair of electrodes and the resistor. The resistor contains lanthanum hexaboride. The thickness of the glass layer at the outer periphery of the resistor is thicker than the thickness of the glass layer at the center of the resistor.

[0064] Moreover, the circuit board according to the embodiment (for example, circuit boards 10A and 10B) has a substrate body (for example, substrate body 11), a pair of electrodes (for example, a pair of electrodes 41 and 42), a resistor (for example, resistor 60A), a glass layer (for example, glass layer 70A), and a resin layer (for example, resin layer 90). The substrate body is made of ceramics. The pair of electrodes are positioned on the substrate body at a distance from each other. The resistor is positioned so as to straddle the pair of electrodes, and has a trimming groove (for example, trimming groove 80). The glass layer covers the pair of electrodes and the resistor. The resin layer covers at least the trimming groove. The resistor contains lanthanum hexaboride. The thickness of the glass layer at the outer periphery of the resistor is thicker than the thickness of the glass layer at the center of the resistor.

[0065] Therefore, according to the circuit board according to the embodiment, peeling of the glass layer can be suitably suppressed.

[0066] It should be noted that the electronic device on which the circuit board according to the present disclosure is mounted is not limited to a lighting device, and the circuit board can be applied to various electronic devices other than lighting devices.

[0067] For example, the electronic device according to the present disclosure can be applied to flow meters, display monitors mounted on smart watches and the like, power modules such as inverters and converters, power semiconductors such as in-vehicle power control units, battery parts, secondary battery parts, air conditioners (particularly for in-vehicle use), optical communication devices, laser projectors such as laser cinema machines, laser processing machines, various sensor parts, optical pickup parts used for reading and writing DVDs (Digital Versatile Disks) and CDs (Compact Disks), laser diode parts, CPUs (Central Processing Units), GPUs (Graphics Processing Units), TPUs (Tensor Processing Units), etc.

[0068] Further advantages and modifications may readily occur to those skilled in the art. Thus, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and equivalents thereof. [Explanation of symbols]

[0069] 1 Lighting equipment 10 Circuit Board 11 Board body 20 Sockets 21 Storage unit 22 Flange 23 Heat dissipation fin 30 Conductive terminal 40 Wiring 41,42 electrode 50 Light emitting element 60 Resistor 70 Glass Layer 80 Trimming groove 90 Resin layer

Claims

1. A substrate body made of ceramics; a pair of electrodes spaced apart from one another on the substrate body; A resistor located across the pair of electrodes; a glass layer covering the pair of electrodes and the resistor; having When the region between the pair of electrodes, in which the resistor and the glass layer are located on the substrate body, is defined as a central region, the region being located at the center between the pair of electrodes, a shortest distance between the substrate body and a surface of the glass layer in the central portion is shorter than a shortest distance between the substrate body and a surface of the glass layer in a peripheral portion of the resistor located on the electrode; Circuit board.

2. 2. The circuit board of claim 1, wherein the resistor comprises lanthanum hexaboride.

3. A substrate body made of ceramics; a pair of electrodes spaced apart from one another on the substrate body; a resistor located across the pair of electrodes and having a trimming groove; a glass layer covering the pair of electrodes and the resistor; a resin layer covering at least the trimming groove; having When the region between the pair of electrodes, in which the resistor and the glass layer are located on the substrate body, is defined as a central region, the region being located at the center between the pair of electrodes, a shortest distance between the substrate body and a surface of the glass layer in the central portion is shorter than a shortest distance between the substrate body and a surface of the glass layer in a peripheral portion of the resistor located on the electrode; Circuit board.

4. 4. The circuit board of claim 3, wherein the resistor comprises lanthanum hexaboride.

5. 5. The circuit board according to claim 1, wherein the void fraction in the central portion of the resistor is higher than the void fraction in the peripheral portion of the resistor.

6. 6. The circuit board according to claim 1, wherein a void diameter in the central portion of the resistor is larger than a void diameter in the outer periphery of the resistor.

7. A circuit board according to any one of claims 1 to 6, an electronic component located on the substrate body and connected to the pair of electrodes; An electronic device comprising:

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