circuit board

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 a circuit board. On the board Regarding. [Background technology]

[0002] Substrates made of ceramics are sometimes used as circuit boards because they have excellent insulating properties and thermal conductivity.

[0003] Patent Document 1 discloses a wiring board having a resistor spanning a first wiring layer and a second wiring layer, and the first wiring layer, the second wiring layer, and the resistor 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] Japanese Patent Application Laid-Open No. 2000-208895 Summary of the Invention

[0005] A circuit board according to one aspect of the present disclosure includes a substrate body, a pair of electrodes, a resistor, and a glass layer. The substrate body is made of ceramic. The pair of electrodes are positioned on the substrate body with a gap between them. The resistor is positioned so as to straddle the pair of electrodes. The glass layer covers the pair of electrodes and the resistor. Furthermore, when the region between the pair of electrodes, where the resistor and the glass layer are positioned on the substrate body, is defined as a central region, the shortest distance between the substrate body and the surface of the glass layer at the central region is shorter than the shortest distance between the substrate body and the surface of the glass layer at the periphery of the resistor positioned on the electrode. [Brief explanation of the drawings]

[0006] [Figure 1]FIG. 1 is a schematic side view of the lighting device according to the first embodiment. [Figure 2] FIG. 2 is a schematic perspective view of the socket according to the first embodiment. [Figure 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 the line IV-IV in FIG. [Figure 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 INVENTION

[0007] Hereinafter, embodiments for carrying out a circuit board and an electronic device according to the present disclosure (hereinafter referred to as "embodiments") will be described in detail with reference to the drawings. Note that the circuit board and electronic device according to the present disclosure are not limited to these embodiments. Furthermore, the embodiments can be appropriately combined as long as the processing content is not contradictory. Furthermore, the same components in the following embodiments will be assigned the same reference numerals, and redundant explanations will be omitted.

[0008] Furthermore, in the following embodiments, expressions such as "constant," "orthogonal," "perpendicular," or "parallel" may be used, but these expressions do not necessarily mean "constant," "orthogonal," "perpendicular," or "parallel" in the strict sense. In other words, the above expressions allow for deviations due to, for example, manufacturing precision, installation precision, etc.

[0009] In addition, in the drawings referred to below, for ease of understanding, an orthogonal coordinate system may be shown in which the X-axis, Y-axis, and Z-axis directions are defined as being perpendicular to each other, and the positive Z-axis direction is the vertically upward direction.

[0010] In the following embodiment, 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 known circuit board includes 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. A known technique for adjusting the resistance value of a resistor in this type of circuit board is to trim a portion 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 that can prevent 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 that has a generally circular outer shape in a plan view. The accommodation portion 21 may be located on the surface opposite to the surface on which the plurality of heat dissipation fins 23 of the flange portion 22, which will be described later, are located. The accommodation portion 21 may have a recess 210 that is recessed from one end surface of the socket 20, specifically, from the surface of the accommodation portion 21 opposite to the surface that contacts the flange portion 22, toward the other end 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 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 pair of sidewalls 211 adjacent to each other in the circumferential direction.

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

[0019] The plurality of heat dissipation fins 23 may be located on the surface of flange portion 22 opposite to the surface on which housing portion 21 is located. In this case, heat generated in circuit board 10 is mainly dissipated from the plurality of heat dissipation fins 23. Here, an example is shown in which socket 20 has four heat dissipation fins 23, but the number of heat dissipation fins 23 included in 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, circuit board 10 has substrate body 11 made of ceramic. 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. Substrate body 11 is stored in storage section 21 with the second surface facing the bottom surface of recess 210, in other words, with the first surface on which a circuit is formed facing outward.

[0022] 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 for the substrate body 11. The substrate body 11 made of aluminum oxide ceramics has excellent processability while maintaining the mechanical strength required of 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 or silver may be located on the first surface of substrate body 11. Wiring 40 is electrically connected to conductive terminal 30 via a conductive joining member (not shown) such as 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 between them. The pair of electrodes 41, 42 may also 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, part of the wiring 40. The pair of electrodes 41, 42 may be formed from the same material as the wiring 40 (for example, copper or silver). Note that the pair of electrodes 41, 42 may contain glass in order to improve bonding with the substrate body 11.

[0026] (Regarding resistors) A resistor 60 may be located between the pair of electrodes 41 and 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-adjusting component. Specifically, the resistor 60 may contain lanthanum hexaboride (LaB6) as the conductive component. Note that lanthanum hexaboride does not necessarily have to be the main component of the resistor 60. The resistor 60 may contain, as conductive components other than lanthanum hexaboride, for example, Cu, Ni, Al, Sn, Pd, Ru, RuO2, Ag, Bi2Ru2O7, Pd2Ru2O6, SrRuO3, CaRuO3, BaRuO3, Ta, TaN, Ta2N, WC, MoSi2, TaSi2, SnO2, and Ta2O5. The resistor 60 may also contain, for example, glass as a resistance-adjusting component.

[0028] (About the glass layer) A glass layer 70 may be positioned 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 positioning 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 whose main component is an R2O-B2O3-SiO2 system (R: alkali metal element), an R2O-SiO2-B2O3-Bi2O3 system (R: alkali metal element), or an R'O-B2O3-SiO2 system (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 the line IV-IV in Fig. 3 .

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

[0032] The inventors of the present application have confirmed that in circuit boards equipped with resistors containing lanthanum hexaboride, glass layer peeling occurs more frequently near the periphery of the resistor, where the resistor and electrodes overlap, than in other areas. This is believed to be due to the reducing action of lanthanum hexaboride. Specifically, lanthanum hexaboride is known as a thermionic emitter, emitting electrons when heated. These emitted electrons are thought to reduce surrounding metal components, causing the glass layer to peel.

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

[0034] In the region of the electrode that is 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 produced by the reduction reaction has a lower affinity with glass, an oxide, than CuO, which weakens the adhesive strength between the electrode and the glass layer 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 where 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 elemental silicon produced 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 prevent peeling of the glass layer 70.

[0037] That is, for example, it is possible to suppress peeling of the glass layer 70 to some extent by increasing the overall thickness of the glass layer 70. This is because the weight of the glass layer 70 increases by the amount of thickness 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 the weight of the glass layer 70 in preventing peeling.

[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, increasing the thickness of the glass layer 70 in the center of the resistor 60 has little effect on the effect of preventing peeling. Furthermore, the thermal stress increases by the amount of thickness increase in the glass layer 70 in the center of the resistor 60, which ends up weakening the effect of preventing peeling due to the weight of the glass layer 70.

[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] Furthermore, in circuit boards, resistors may be trimmed after product shipment in order to adjust their resistance values. Trimming is a technique for adjusting the resistance value of a resistor by forming a groove in the center of the resistor or its vicinity using a laser or the like to narrow the resistor width. According to the circuit board 10 of the first embodiment, the thickness of the glass layer 70 in the center of the resistor 60 is relatively thin, thereby ensuring ease of trimming and suitably suppressing peeling of the glass layer 70. Furthermore, according to the circuit board 10 of the first embodiment, the thickness of the glass layer 70 in the center of the resistor 60 is relatively thin, thereby reducing the material cost required for the glass layer 70.

[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 can be increased. For example, after applying one layer of glass to the pair of electrodes 41, 42 and the resistor 60, another layer of glass can be applied to the outer periphery of the resistor 60. In this case, by using a mask member having an opening in 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 susceptible to peeling due to thermal stress than other positions. Therefore, by increasing the thickness of the glass layer 70 at the peripheral portion of the resistor 60, particularly at the position where the above three elements contact each other, peeling of the glass layer 70 can be more effectively 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 location most susceptible to stress due to repeated thermal expansion and contraction. By increasing the thickness T4 of the glass layer 70 at this position, peeling of the glass layer 70 can be suitably suppressed. Furthermore, 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, heat transferred from the resistor 60 to the electrode 41 (42) can be efficiently dissipated 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 scanning electron microscope (SEM).

[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] The resistor 60 may have voids in the outer periphery thereof. The presence of voids in the outer periphery of the resistor 60 alleviates thermal stress occurring near the outer periphery of the resistor 60, thereby improving the reliability of the circuit board 10.

[0048] The resistor 60 is formed after the electrodes 41 (42) are formed on the substrate body 11. When the resistor 60 is formed, the electrodes 41 (42) are heated, which facilitates the escape of gas present in the resistor 60 near the electrodes 41 (42) and promotes sintering, which is thought to result in a relatively low void fraction in the outer periphery of the resistor 60.

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

[0050] The void fraction of the resistor 60 can be determined, for example, as follows: First, the circuit board 10 is cut so as to obtain a cross section of the resistor 60, and the cut surface is observed using an 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 determining the void fraction of the resistor 60.

[0051] For example, the void fraction of resistor 60 may be 5% by area or more and 40% by area or less. For example, the void diameter (equivalent circle diameter) at the center of resistor 60 may be 5 μm to 11 μm, and the void diameter (equivalent circle diameter) at the periphery of resistor 60 may be 3 μm to 6 μm. The equivalent circle diameter of the voids can also be determined by analyzing the SEM image. For example, the voids in the SEM image may be traced, and the traced image may be analyzed using a particle analysis technique in the image analysis software "Azo-kun" (registered trademark, manufactured by Asahi Kasei Engineering Co., Ltd.; hereinafter, the image analysis software "Azo-kun" refers to the image analysis software manufactured by Asahi Kasei Engineering Co., Ltd.), to calculate the average equivalent circle diameter of the voids.

[0052] (Second embodiment) Next, the configuration of a circuit board according to a 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 may be formed in the resistor 60A and the glass layer 70A, penetrating the resistor 60A and the glass layer 70A from top to bottom. 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 refers to the center in the cross-sectional view shown in FIG. 5, i.e., 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 offset from the center of the resistor 60A. The trimming groove 80 extends linearly in parallel to the pair of electrodes 41, 42, for example. Alternatively, the trimming groove 80 may be L-shaped, having a portion that extends linearly in parallel to the pair of electrodes 41, 42 and a portion that extends perpendicular to the pair of electrodes 41, 42.

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

[0056] In this way, 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 60A, 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 way, unnecessary increases in thermal stress are 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 include a resin layer 90B. The resin layer 90B according to the third embodiment may cover only a portion of the pair of electrodes 41, 42, the resistor 60A, and the glass layer 70A, including the central portion of the resistor 60A. Specifically, the resin layer 90B may be located inside a region 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 that the resin layer 90B entirely covers the pair of electrodes 41, 42, the resistor 60A, and the glass layer 70A.

[0062] Furthermore, in the circuit board 10B according to the third embodiment, the total thickness T7 of the glass layer 70A and the resin layer 90B at the periphery P of the resistor 60 in the electrode 41 (42) (corresponding to the thickness T1 of the glass layer 70A at the periphery P) 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 way, 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, and 10B) includes 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, resistors 60 and 60A), and a glass layer (for example, glass layers 70 and 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 greater than the thickness of the glass layer at the center of the resistor.

[0064] Furthermore, a circuit board (for example, circuit boards 10A and 10B) according to the embodiment includes 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 greater 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] The electronic device on which the circuit board according to the present disclosure is mounted is not limited to a lighting device, but can be applied to various electronic devices other than lighting devices.

[0067] For example, electronic devices 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 components, secondary battery components, air conditioners (particularly for in-vehicle use), optical communication devices, laser projectors such as laser cinema machines, laser processing machines, various sensor components, optical pickup components used for reading and writing DVDs (Digital Versatile Disks) and CDs (Compact Disks), laser diode components, CPUs (Central Processing Units), GPUs (Graphics Processing Units), TPUs (Tensor Processing Units), etc.

[0068] Further advantages and modifications will readily occur to those skilled in the art. Therefore, 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 their equivalents. [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 layers 80 trimming groove 90 Resin layer

Claims

1. a substrate body made of ceramic; a pair of electrodes spaced apart on the substrate body; a resistor positioned across the pair of electrodes; a glass layer covering the pair of electrodes and the resistor; and 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, the shortest distance between the substrate body and the surface of the glass layer at the central portion is shorter than the shortest distance between the surface of the glass layer and the substrate body at the periphery of the resistor located on the electrode, A circuit board, wherein the void fraction in the central portion of the resistor is higher than the void fraction in the outer periphery of the resistor.

2. A substrate body made of ceramics; a pair of electrodes spaced apart on the substrate body; a resistor positioned across the pair of electrodes; a glass layer covering the pair of electrodes and the resistor; and 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, the shortest distance between the substrate body and the surface of the glass layer at the central portion is shorter than the shortest distance between the surface of the glass layer and the substrate body at the periphery of the resistor located on the electrode, A circuit board, wherein a void diameter in the central portion of the resistor is larger than a void diameter in the outer periphery of the resistor.

3. A substrate body made of ceramics; a pair of electrodes spaced apart on the substrate body; a resistor positioned across the pair of electrodes; a glass layer covering the pair of electrodes and the resistor; and 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, the shortest distance between the substrate body and the surface of the glass layer at the central portion is shorter than the shortest distance between the surface of the glass layer and the substrate body at the periphery of the resistor located on the electrode, the void fraction in the central portion of the resistor is higher than the void fraction in the outer periphery of the resistor; A circuit board, wherein a void diameter in the central portion of the resistor is larger than a void diameter in the outer periphery of the resistor.

4. a substrate body made of ceramic; a pair of electrodes spaced apart on the substrate body; a resistor positioned 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; and 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, the shortest distance between the substrate body and the surface of the glass layer at the central portion is shorter than the shortest distance between the surface of the glass layer and the substrate body at the periphery of the resistor located on the electrode, A circuit board, wherein the void fraction in the central portion of the resistor is higher than the void fraction in the outer periphery of the resistor.

5. A substrate body made of ceramics; a pair of electrodes spaced apart on the substrate body; a resistor positioned 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; and 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, the shortest distance between the substrate body and the surface of the glass layer at the central portion is shorter than the shortest distance between the surface of the glass layer and the substrate body at the periphery of the resistor located on the electrode, A circuit board, wherein a void diameter in the central portion of the resistor is larger than a void diameter in the outer periphery of the resistor.

6. A substrate body made of ceramics; a pair of electrodes spaced apart on the substrate body; a resistor positioned 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; and 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, the shortest distance between the substrate body and the surface of the glass layer at the central portion is shorter than the shortest distance between the surface of the glass layer and the substrate body at the periphery of the resistor located on the electrode, the void fraction in the central portion of the resistor is higher than the void fraction in the outer periphery of the resistor; A circuit board, 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. 7. The circuit board according to claim 1, wherein the resistor contains lanthanum hexaboride.

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