Circuit board manufacturing method

Abstract

To provide a method for manufacturing a circuit board that enables simple formation of the circuit board.SOLUTION: A method for manufacturing a circuit board includes a coating step S11 in which an inorganic adhesive 13 is applied to a base material 11, an adhesion step S14 in which conductive powder 14 is adhered to the inorganic adhesive 13, and a formation step S15 in which the base material 11 and conductive powder 14 are pressed together and the inorganic adhesive 13 is heated to cure to form wiring patterns 12.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a method for manufacturing a circuit board, a circuit board, and a light emitting device. [Background technology]

[0002] As a method for manufacturing a circuit board used in a light-emitting device or the like, a method has been disclosed in which an adhesive photosensitive resin layer is formed on a heat-resistant substrate, a circuit pattern is exposed to the photosensitive resin via a phototool, the photosensitive resin layer in the exposed areas is cured and loses its adhesiveness, circuit-forming particles, which are a mixture of heat-resistant conductive particles and glass particles, etc., are contacted with the substrate and adhered to the uncured photosensitive resin layer, the heat-resistant substrate is then placed in a sintering furnace, the glass particles, etc. are melted, and the heat-resistant conductive particles are fixed onto the heat-resistant substrate (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-74971 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of an embodiment of the present disclosure is to provide a method for manufacturing a circuit board that enables a circuit board to be easily formed, and a circuit board and a light emitting device. [Means for solving the problem]

[0005] A manufacturing method for a circuit board according to an embodiment of the present disclosure includes a coating step of coating an inorganic adhesive onto a substrate, an adhesion step of adhering a conductive powder to the inorganic adhesive, and a formation step of forming a wiring pattern by pressing the substrate and the conductive powder and heating and curing the inorganic adhesive.

[0006] Moreover, a circuit board according to an embodiment of the present disclosure comprises a substrate and a wiring pattern provided on at least one surface of the substrate, the wiring pattern including a conductive powder and an inorganic adhesive, and is configured such that the mass ratio of the conductive powder to the inorganic adhesive at the contact portion with the substrate is smaller than that at a surface portion.

[0007] A light source device according to an embodiment of the present disclosure includes the circuit board and a light source device provided on the circuit board. Effect of the Invention

[0008] According to the embodiments of the present disclosure, it is possible to provide a circuit board manufacturing method that enables a circuit board to be easily formed, as well as a circuit board and a light emitting device. [Brief description of the drawings]

[0009] [Figure 1A] FIG. 2 is a perspective view of a circuit board according to the first embodiment. [Figure 1B] FIG. 1B is a cross-sectional view taken along the line IB-IB in FIG. [Diagram 2] 4 is a flowchart showing a method for manufacturing a circuit board according to the first embodiment. [Figure 3A] 3 is a plan view illustrating a coating step in the method for manufacturing a circuit board according to the first embodiment. FIG. [Figure 3B] 4 is a side view showing a schematic diagram of a first squeegeeing step in the method for manufacturing a circuit board according to the first embodiment. FIG. [Figure 3C] 3 is a side view showing a schematic diagram of an attachment step in the method for manufacturing a circuit board according to the first embodiment. FIG. [Figure 3D] 3A to 3C are side views each showing a schematic diagram of a forming step in the method for manufacturing the circuit board according to the first embodiment. [Figure 4A] FIG. 11 is a side cross-sectional view of a circuit board according to a second embodiment. [Figure 4B] 11 is an enlarged side cross-sectional view of a wiring pattern portion of a circuit board according to a second embodiment. FIG. [Diagram 5]10 is a flowchart showing a method for manufacturing a circuit board according to a second embodiment. [Figure 6A] 13 is a perspective view showing a schematic diagram of a preparation step of preparing a substrate having a circuit groove formed therein in a method for manufacturing a circuit substrate according to a second embodiment. FIG. [Figure 6B] 10 is a side cross-sectional view that illustrates a coating step in a method for manufacturing a circuit board according to a second embodiment. FIG. [Figure 6C] 10 is a side cross-sectional view that typically illustrates an attachment step in a method for manufacturing a circuit board according to a second embodiment. FIG. [Figure 6D] 13 is a side cross-sectional view that typically illustrates a second squeegeeing step in the method for manufacturing a circuit board according to the second embodiment. FIG. [Figure 6E] 10A to 10C are side cross-sectional views that diagrammatically show a forming step in a method for manufacturing a circuit board according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present disclosure will be described in detail below with reference to the drawings. In the following description, terms indicating specific directions or positions (e.g., "upper", "lower", and other similar terms) are used as necessary, but the use of these terms is intended to facilitate understanding of the disclosure with reference to the drawings, and does not limit the technical scope of the present disclosure. In addition, parts with the same reference numerals appearing in multiple drawings indicate the same or equivalent parts, members, or elements, and descriptions thereof may be omitted as appropriate.

[0011] Furthermore, the embodiments shown below are intended to exemplify the contents of the present disclosure in order to embody the technical ideas of the present disclosure, and are not intended to limit the technical scope of the present disclosure. Furthermore, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the components described below are intended to exemplify the present disclosure, and are not intended to limit the scope of the present disclosure to those particulars.

[0012] First Embodiment [Circuit board] In the circuit board of the first embodiment, a wiring pattern 12 is formed so as to protrude from the upper surface of a flat substrate 11. This wiring pattern 12 contains conductive powder 14 and inorganic adhesive 13. The configuration of the circuit board will be described with reference to Figures 1A and 1B. Figure 1A is a perspective view of the circuit board according to the first embodiment. Figure 1B is a cross-sectional view taken along line IB-IB in Figure 1A. In the circuit board 10 of the first embodiment, a wiring pattern 12 is formed in a film thickness so as to cover a part of the upper surface of a flat substrate 11. This wiring pattern 12 contains conductive powder 14 and an inorganic adhesive 13.

[0013] The substrate 11 is preferably made of an insulating material, and is preferably made of a material that is difficult to transmit light emitted from the light emitting element and external light, and is preferably made of a material having a certain degree of strength. Specifically, the substrate 11 can be made of ceramics such as alumina, aluminum nitride, mullite, silicon nitride, zirconia, silicon carbide, and resins such as phenol resin, epoxy resin, polyimide resin, BT resin (bismaleimide triazine resin), and polyphthalamide. The substrate 11 may also be made of a silicon wafer or a glass material such as soda glass or quartz glass. The shape of the substrate 11 is not particularly limited, but may be formed into a shape suitable for the purpose, such as a rectangle.

[0014] The wiring pattern 12 has an inorganic adhesive 13 covering the conductive powder 14 on the side, and the inorganic adhesive 13 penetrates between the particles of the conductive powder 14, and is integrated by the adhesive force. The conductive powder 14 has various bonding forms depending on the location, such as a location in direct contact with the substrate 11 and a location where the conductive powder 14 is plastically deformed and the particles are bonded together by the adhesive force of the inorganic adhesive 13. When the conductive powder 14 is plastically deformed by applying pressure up to the pressure region where plastic deformation occurs, the contact area between the conductive powder particles 14 increases and the resistance decreases.

[0015] The conductive powder 14 can be appropriately selected and used as a metal powder. For example, the conductive powder 14 can be at least one of copper, iron, zinc, nickel, tungsten, chromium, aluminum, silver, gold, titanium, palladium, rhodium, or alloys thereof, or metals coated with these metals, or a combination of a plurality of these metals. In order to further reduce the resistance, the conductive powder 14 can be a scaly powder, or a suitable mixture of spherical particles and scaly particles. The particle size of the conductive powder 14 is preferably small, and in particular, a particle size of 1 μm to 10 μm is suitable. The most preferred particle size is 2 μm to 6 μm.

[0016] The mass ratio of the conductive powder 14 to the inorganic adhesive 13 in the wiring pattern 12 is smaller in the vicinity of the contact portion with the substrate 11 than in the surface layer portion separated from the substrate 11. That is, the amount of the inorganic adhesive 13 is greater relative to the total mass of the inorganic adhesive 13 and the conductive powder 14 in the vicinity of the contact portion with the substrate 11, and the amount of the conductive powder 14 increases toward the surface layer portion. There are no limitations on the type of inorganic adhesive 13 as long as it is a type that can exert adhesive strength by hardening the binder, and an appropriate selection can be made from alkali metal silicate adhesives, phosphate adhesives, silica sol adhesives, hydraulic adhesives, calcium silicate hydrate, and the like.

[0017] [Circuit board manufacturing method] The method for manufacturing the circuit board will be described below with reference to FIG. 2 and FIG. 3A to FIG. 3D. Fig. 2 is a flow chart showing a method for manufacturing a circuit board according to the first embodiment. Fig. 3A is a plan view showing a coating step in the method for manufacturing a circuit board according to the first embodiment. Fig. 3B is a side view showing a first squeegeeing step in the method for manufacturing a circuit board according to the first embodiment. Fig. 3C is a side view showing a bonding step in the method for manufacturing a circuit board according to the first embodiment. Fig. 3D is a side view showing a forming step in the method for manufacturing a circuit board according to the first embodiment.

[0018] In the method for manufacturing the circuit board 10 according to the first embodiment, the base material 11 constituting the board and the conductive powder 14 constituting the wiring are integrated with the inorganic adhesive 13. This method for manufacturing a circuit board includes each of the steps required depending on the implementation situation, among (1) a coating step S11, (2) a first squeegeeing step S12, (3) a first removal step S13, (4) an adhesion step S14, (5) a formation step S15, (6) a wiring pattern removal step S16, (7) a planarization step S17, and (8) an acid treatment step S18. Each step will be described in detail below.

[0019] (1) Coating process The coating step S11 is a step of coating the base material 11 with an inorganic adhesive 13. The inorganic adhesive 13 may be coated to precise dimensions so that the coated area has the shape of the wiring pattern 12. Alternatively, the adhesive may be coated over an area larger than the wiring pattern 12 to be formed, and unnecessary portions may be removed in the wiring pattern removal step S16 described below. In this coating step S11, a sheet 16 is provided on the lower surface of the base material 11 (hereinafter, may be referred to as the "upper member").

[0020] There is no limitation on the method of applying the inorganic adhesive 13, and any method can be appropriately selected and used, such as application with an application device 31 (including a brush, etc.), spraying with a sprayer, or extrusion with an extrusion device. Furthermore, it is preferable that the inorganic adhesive 13 be formed as thin as possible while still ensuring the adhesive strength required for forming the wiring pattern 12, and the thickness of the adhesive layer is preferably 50 μm or less.

[0021] (2) First squeegee process The first squeegeeing step S12 is a step of applying conductive powder 14 onto metal mask 32 placed on sheet 17 (film) and performing squeegeeing. In the first squeegeeing step S12, conductive powder 14 is provided in the openings of metal mask 32 with a substantially uniform thickness. In the first squeegeeing step S12, for example, first, a metal mask 32 having openings formed therein corresponding to the positions where the conductive powder 14 constituting the wiring pattern 12 is to be attached is provided on the sheet 17. Then, the conductive powder 14 is scattered on the metal mask 32, and a metal squeegee 33 is slid to smooth out the conductive powder 14 to a substantially uniform thickness. The metal squeegee 33 may be a rubber squeegee, and any other metal squeegee capable of squeegeeing the scattered conductive powder 14 may be used. Furthermore, the metal mask 32 is not limited to one made of metal, and a mask made of a film, a screen, rubber, or the like may be used depending on the viscosity of the inorganic adhesive 13 used and the amount of conductive powder 14. The term "substantially uniform" used here includes cases where there is an error that is not adversely affected on the circuit board and can be regarded as uniform.

[0022] The shape of the opening in metal mask 32 may be a wiring pattern of precise dimensions from the beginning, or may be a shape of an area larger than the wiring pattern 12 to be formed, and unnecessary portions may be removed in the wiring pattern removal process S16 described below.

[0023] (3) First removal process The first removing step S13 is a step of removing the metal mask 32 from the sheet 17 used in the first squeegeeing step S12. As a result, the conductive powder 14 is spread evenly on the sheet 17 in a substantially uniform thickness in the shape of the openings of the metal mask 32 (hereinafter, may be referred to as the "lower member"). The term "substantially uniform" as used here includes cases where there is an error to the extent that it is considered to be uniform, as long as it does not adversely affect the circuit board.

[0024] (4) Attachment process The adhering step S14 is a step of adhering the conductive powder 14 to the inorganic adhesive 13 on the substrate 11. In this adhesion step S14, the inorganic adhesive 13 of the upper member and the conductive powder 14 of the lower member are placed on top of each other so that they face each other, and the inorganic adhesive 13 and the conductive powder 14 are adhered to each other. When performing the adhesion step S14, the upper member is placed so that the inorganic adhesive 13 is located on the lower surface of the upper member. In addition, it is preferable that the lower member is placed so that the conductive powder 14 is scattered on the upper surface of the lower member and a sheet 17 is provided on the lower surface of the lower member.

[0025] (5) Forming process The forming step S15 is a step of forming the wiring pattern 12 by pressing the base material 11 and the conductive powder 14 together and heating and curing the inorganic adhesive 13. In this forming step S15, the upper member, in which the inorganic adhesive 13 is applied to the base material 11, and the lower member, in which the conductive powder 14 is evenly spread, which are superimposed on each other, are pressurized and heated from above and below using a hot press device 34, and the two components are brought into close contact and cured. As a result, the base material 11 and the conductive powder 14 are integrated via the inorganic adhesive 13. The wiring pattern 12 formed in the forming step S15 is cured in a state in which the inorganic adhesive 13 has penetrated between the particles of the conductive powder 14 and is in close contact with each other. After this process is completed, the sheets 16 and 17 are peeled off. The sheets 16 and 17 used here are mainly used to protect the base material 11 and the like from being scratched during each process.

[0026] The pressure and heating temperature can be appropriately determined within a range in which the inorganic adhesive 13 can react and exhibit adhesive strength, and for example, the pressure is set to 0.1 MPa to 2.0 MPa and the heating temperature to 150°C to 300°C. Although it varies depending on the area to which pressure is applied, a pressure of 0.1 Pa to 1.0 Pa is more preferable. The forming step can be performed in air or in a vacuum, but is more preferably performed in a vacuum. By performing the work in a vacuum, oxidation of the conductive powder 14 can be suppressed and the resistance can be reduced.

[0027] (6) Wiring pattern removal process The wiring pattern removing step S16 is a step that is performed as necessary, and is a step of removing an unnecessary portion of the wiring pattern 12 formed in the forming step S15 so as to fit the wiring pattern 12 to be formed. In this wiring pattern removal step S16, laser etching is preferably used, and necessary operations such as narrowing the line width of the wiring pattern 12 and dividing the wiring pattern 12 into two or more parts are performed.

[0028] (7) Flattening process The planarization step S17 is a step of polishing and planarizing the surface of the wiring pattern 12 with an abrasive. As a polishing method, a method of spraying a solution containing an abrasive, etc. can be used. When the conductive powder 14 on the surface of the wiring pattern 12 is polished, the chips undergo shear deformation and generate streamlined chips, resulting in a ductile mode. Polishing in the ductile mode improves the contact between the conductive powder particles 14.

[0029] (8) Acid treatment process The acid treatment step S18 is a step that is performed as necessary, and is a step of performing an acid treatment on the wiring pattern 12 after the formation step S15 or the planarization step S17. In this acid treatment step S18, when an oxide film is formed on the conductive powder 14 on the surface of the wiring pattern 12, the oxide film is removed by performing an acid treatment using hydrochloric acid, sulfuric acid (dilute sulfuric acid), nitric acid (dilute nitric acid), or the like.

[0030] <Modification> As another method of the circuit board manufacturing method according to the first embodiment described above, a preparation step of preparing a substrate 11 provided with a mask for preparing a metal mask 32 to be placed on the substrate 11 may be performed before the application step S11, and in the application step S11, an inorganic adhesive 13 may be applied from above the metal mask 32, and then a second removal step of removing the metal mask 32 from the substrate 11 may be performed.

[0031] When the second removing step is performed, in the first squeegeeing step S12, the conductive powder 14 may be directly scattered on the sheet 17 without placing the metal mask 32 on the sheet 17. At this time, it is preferable to spread the conductive powder 14 to a substantially uniform thickness from the viewpoint of resistance and thermal conduction. When such a step is performed, the metal mask 32 is not placed on the sheet 17, so that the subsequent first removing step S13 can be omitted. Furthermore, after the second removing step, the conductive powder 14 may be sprinkled directly onto the base material 11 to which the inorganic adhesive 13 has been applied. Since the conductive powder is applied without using the sheet 17, the subsequent first squeegeeing step S12 and first removing step S13 can be omitted.

[0032] In addition, in the method for manufacturing a circuit board described above (the same applies to the method for manufacturing a circuit board described below), it is possible to add other steps in addition to those described above, if necessary. [Effects] According to the wiring pattern 12 of the circuit board 10 according to the first embodiment, the mass ratio of the conductive powder 14 to the inorganic adhesive 13 in the vicinity of the contact portion with the substrate 11 is smaller than the value in the surface layer portion separated from the substrate 11. Therefore, since the amount of the inorganic adhesive 13 is large in the contact portion with the substrate 11, it is possible to improve the adhesion of the wiring pattern 12 to the substrate 11. Furthermore, since the amount of the conductive powder 14 increases toward the surface layer portion, it is possible to obtain a circuit board 10 having good thermal conductivity.

[0033] Furthermore, since the conductive powder 14 is adhered to the substrate 11 using the inorganic adhesive 13, it is possible to obtain a circuit board 10 having a wiring pattern 12 that is highly hard and resistant to scratches. High hardness refers to a pencil hardness of 6H to 9H. In terms of Mohs hardness, it refers to a hardness of 4 or higher. In addition, it is also possible to perform pattern plating of Cu, Au, Ni, etc. on the conductive powder 14 that forms the wiring pattern 12, so that wiring with lower resistance can be formed.

[0034] Furthermore, according to the method for manufacturing the circuit board 10 in the first embodiment, the circuit board 10 can be manufactured by overlapping the base material 11 coated with the inorganic adhesive 13 and the conductive powder 14, pressurizing the base material 11 and the conductive powder 14, and heating and curing the inorganic adhesive 13. Therefore, the circuit board 10 can be manufactured easily without using large-scale equipment.

[0035] Furthermore, by applying the conductive powder 14 onto the sheet 17 using the metal mask 32, it becomes possible to easily provide the conductive powder 14 so as to form a desired wiring pattern. Moreover, by performing squeegeeing on the metal mask after applying the conductive powder 14, it becomes possible to provide a substantially uniform conductive powder 14 in a simple manner.

[0036] The heating temperature in the formation step S15 can be appropriately determined within a range in which the inorganic adhesive 13 can exert its adhesive strength. The heating temperature in this embodiment is preferably 150°C to 300°C. The heating temperature in this embodiment can be set at a temperature at which the inorganic adhesive 13 hardens, and the temperature difference from room temperature can be reduced. This prevents warping and the like from occurring in the circuit board, and enables the manufacture of a flat circuit board, thereby improving the reliability of quality.

[0037] <Second embodiment> [Circuit board] Hereinafter, a circuit board 20 according to the second embodiment will be described with reference to FIGS. 4A and 4B. Fig. 4A is a side cross-sectional view of a circuit board according to a second embodiment, and Fig. 4B is an enlarged side cross-sectional view of a wiring pattern portion of the circuit board according to the second embodiment. The circuit board 20 has a flat base material 21 and a desired wiring pattern 22. This wiring pattern 22 contains conductive powder 24 and an inorganic adhesive 23. Therefore, the wiring pattern 22 does not protrude from the surface of the circuit board 20, and the surface of the base material 21 is formed to be approximately flat. The circuit groove 21a is formed by laser processing and is formed as a processing mark having a certain width and depth. Alternatively, the circuit groove 21a may be formed by mechanical processing such as cutting.

[0038] The wiring pattern 22 is formed by integrating the conductive powder 24 with the inorganic adhesive 23. The conductive powder 24 has various bonding forms depending on the location, such as portions where the conductive powder 24 is in direct contact with the wall surface or bottom surface of the circuit groove 21a due to the inorganic adhesive 23, and portions where the conductive powder 24 is plastically deformed and bonded between particles by the adhesive force of the inorganic adhesive 23. In the wiring pattern 22, the mass ratio of the conductive powder 24 to the inorganic adhesive 23 is smaller as it approaches the wall and bottom surfaces of the circuit groove 21a, which are the contact surfaces with the substrate 21, and is larger as it moves away from the wall and bottom surfaces of the circuit groove 21a.

[0039] [Circuit board manufacturing method] Next, a method for manufacturing a circuit board will be described with reference to FIG. 5 and FIG. 6A to FIG. 6E. FIG. 5 is a flow chart showing a method for manufacturing a circuit board according to a second embodiment. FIG. 6A is a perspective view showing a preparation step of preparing a base material having a circuit groove formed therein in the method for manufacturing a circuit board according to the second embodiment. FIG. 6B is a side cross-sectional view showing a coating step in the method for manufacturing a circuit board according to the second embodiment. FIG. 6C is a side cross-sectional view showing a bonding step in the method for manufacturing a circuit board according to the second embodiment. FIG. 6D is a side cross-sectional view showing a second squeegeeing step in the method for manufacturing a circuit board according to the second embodiment. FIG. 6E is a side cross-sectional view showing a formation step in the method for manufacturing a circuit board according to the second embodiment.

[0040] The method for manufacturing the circuit board 20 according to the second embodiment includes a "second preparation step S21" before the "coating step S11" and a "second squeegee step S24" after the "attaching step S14" in the method for manufacturing the circuit board according to the first embodiment, and does not include a "first squeegee step S12" and a "first removal step S13". That is, the method for manufacturing the circuit board 20 according to the second embodiment is configured by including each step among (1) the second preparation step S21, (2) the coating step S22, (3) the attaching step S23, (4) the second squeegee step S24, (5) the forming step S25, (6) the flattening step S26, and (7) the acid treatment step S27, which are necessary depending on the implementation situation. Each step will be described in detail below. The description of the same configuration as the method for manufacturing the circuit board according to the first embodiment may be omitted.

[0041] (1)Second preparation process The second preparation step S21 is a preparation step for preparing a substrate 21 having circuit grooves 21a formed therein so as to have the shape of the wiring pattern 22 to be formed. The shape (cross-sectional shape and planar shape) and dimensions (width, depth, etc.) of the circuit groove 21a are not limited and can be determined appropriately. The circuit groove 21a can be formed by laser or other processing methods. The circuit groove 21a is formed by, for example, laser processing or the like, and is formed as a processing mark having a certain width and depth. The circuit groove 21a may also be formed by mechanical processing such as cutting.

[0042] (2) Coating process The application step S22 is a step of applying an inorganic adhesive 23 to the inside of the circuit groove 21a of the substrate 21. Therefore, in the case of a circuit groove 21a having a rectangular cross section, it is preferable to apply the inorganic adhesive 23 along the wall and bottom surfaces of the circuit groove 21a. At this time, a method of applying the inorganic adhesive 23 to the circuit groove 21a using a device such as a jet dispenser, or masking the substrate 21 with a film to expose the groove circuit 21a, applying the inorganic adhesive 23 by a dip method, and removing the excess by air blowing, etc. may be used.

[0043] (3) Attachment process The adhering step S23 is a step of adhering the conductive powder 24 to the inorganic adhesive 23. In this attachment step S23, first, the conductive powder 24 is scattered from above the circuit groove 21a to fill the circuit groove 21a with the conductive powder 24.

[0044] (4) Second squeegee process The second squeegeeing step S24 is a step that is performed as necessary, and involves the task of removing the conductive powder 24 that has overflowed from the circuit grooves 21a by squeegeeing.

[0045] (5) Forming process The forming step S25 is a step of pressing the base material 21 and the conductive powder 24 together and heating and curing the inorganic adhesive 23 to form the wiring pattern 22. In this forming step S25, the base material 21, in which the circuit grooves 21a are filled with the conductive powder 24, is pressed and heated using a hot press device 34 to bond the two components together and cure them.

[0046] (6) Planarization process and acid treatment process The planarization step S26 and the acid treatment step S27 are steps that are performed as necessary, and are performed in the same manner as in the method for manufacturing the circuit board 10 described above.

[0047] [Effects] According to the circuit board 20 of the second embodiment, the circuit wiring is formed by the wiring pattern 22 in which the conductive powder 24 and the inorganic adhesive 23 are integrated and filled in the circuit groove 21a of the base material 21. Therefore, it is possible to achieve a structure in which the circuit wiring does not protrude from the surface of the base material 21. Also, the circuit board 20 can have good thermal conductivity, similar to the circuit board 10 of the first embodiment described above.

[0048] Moreover, according to the method for manufacturing circuit board 20 according to the second embodiment, like the method for manufacturing circuit board 10 according to the first embodiment, circuit board 20 can be manufactured easily without using large-scale equipment. Furthermore, since it is possible to form circuit board 20 at a temperature at which inorganic adhesive 13 hardens, like the method for manufacturing circuit board 10 according to the first embodiment, the reliability of the quality of circuit board 20 can be improved.

[0049] The method for manufacturing a circuit board may include other steps between, before, or after each of the steps, as long as they do not adversely affect the steps. For example, the method may include a foreign matter removal step for removing foreign matter that has been mixed in during the manufacturing process, a step for plating the formed wiring, etc. [Light source device] The circuit board 10 according to the first embodiment or the circuit board 20 according to the second embodiment can be used together with a light emitting element as a light source device. A light emitting element can be electrically connected to the wiring pattern 12 of the circuit board 10 according to the first embodiment or the wiring pattern 22 of the circuit board 20 according to the second embodiment, and covered with a sealing member as necessary to form a light source device. With such a light source device, the wiring pattern has excellent thermal conductivity, so that the cause of deterioration of the light source device due to heat can be suppressed. [Explanation of symbols]

[0050] 10, 20 Circuit board 11,21 Base material 21a circuit groove 12,22 Wiring pattern 13,23 Inorganic adhesives 14,24 Conductive powder 16,17 seats 32 Metal Mask 34 Heat press device S11, S22 Coating process S12 First squeegee process S13 1st removal process S14, S23 Adhesion process S15,S25 Forming process S16 Wiring pattern removal process S17,S26 Flattening process S18, S27 Acid treatment process S21 2nd preparation process S24 Second squeegee process

Claims

1. a coating step of forming an upper member by coating a base material with an inorganic adhesive; forming a lower member on a sheet by adhering conductive powder via a mask for forming a wiring pattern; an adhesion step of arranging the inorganic adhesive of the upper member and the conductive powder of the lower member so as to face each other and adhering the inorganic adhesive to the conductive powder; a forming step of pressing the base material and the conductive powder together and heating the inorganic adhesive to harden the adhesive, thereby forming a wiring pattern; A method for manufacturing a circuit board, wherein the process for forming the lower member includes a first squeegeeing process for applying the conductive powder onto the sheet on which the mask is provided and squeegeeing the applied powder, and a first removal process for removing the mask from the sheet.

2. The method for manufacturing a circuit board according to claim 1 , further comprising, after the forming step, a planarizing step of polishing and planarizing the hardened conductive powder.

3. 3. The method for manufacturing a circuit board according to claim 1, wherein the conductive powder contains at least one powder of gold, silver, copper, zinc, nickel, iron, alloys thereof, or metals coated with these metals.

4. 4. The method for manufacturing a circuit board according to claim 1, wherein the coating step coats the inorganic adhesive so that the coated shape of the inorganic adhesive has a shape of a wiring pattern.

5. a preparation step of preparing a substrate having a circuit groove formed in a shape corresponding to a wiring pattern to be formed; a coating step of coating an inorganic adhesive in the circuit groove; a step of scattering conductive powder so as to overflow from the circuit groove of the base material to which the inorganic adhesive has been applied in the coating step, thereby filling the circuit groove with the conductive powder; removing the conductive powder that has overflowed from within the circuit groove; and a forming step of pressing the base material and the conductive powder together using a hot press device and heating and curing the inorganic adhesive to form a wiring pattern that does not protrude from the surface of the base material, The method for manufacturing a circuit board, wherein the step of removing the conductive powder includes a second squeegeeing step of squeegeeing.

6. 6. The method for manufacturing a circuit board according to claim 5, further comprising the steps of: masking the circuit grooves with a film so as to expose the circuit grooves before the step of filling the conductive powder; and then, performing the step of filling the conductive powder.

7. 7. The method for manufacturing a circuit board according to claim 1, further comprising, after the forming step, a wiring pattern removing step of removing a part of the wiring pattern.

8. The method for manufacturing a circuit board according to claim 7 , wherein the wiring pattern removing step uses a laser.

9. 9. The method for manufacturing a circuit board according to claim 7, wherein in the wiring pattern removing step, a line width of the wiring pattern is narrowed.

10. 9. The method for manufacturing a circuit board according to claim 7, wherein the wiring pattern is divided into two or more parts in the wiring pattern removing step.

11. The method for manufacturing a circuit board according to claim 1 , further comprising, after the forming step, an acid treatment step of subjecting the hardened conductive powder to an acid treatment.

12. The method for producing a circuit board according to claim 2 , further comprising, after the planarizing step, an acid treatment step of treating the hardened conductive powder with an acid.

13. 13. The method for manufacturing a circuit board according to claim 5, wherein in the coating step, the inorganic adhesive is coated so as to form a recess along a wall surface and a bottom surface of the circuit groove.

14. The method for manufacturing a circuit board according to claim 1 , wherein in the forming step, the base material and the conductive powder are pressed to a pressure range where the conductive powder is plastically deformed.

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