Circuit board and method for manufacturing mounting board

Abstract

Provided is a circuit board comprising: a base material; at least a pair of terminals provided on the base material; a bonding material that is disposed on the terminal and includes a metal element; and an inner wall of an insulating material that rises from the base material in a height direction orthogonal to a main surface of the base material. The pair of terminals and the bonding material are arranged in a cavity formed in the wall. At least one groove part penetrating from an inner peripheral surface to an outer peripheral surface is formed on the inner wall. On the inner wall on an outer circumferential side, an outer wall of an insulating material that rises from the base material in the height direction is provided so as to surround the cavity.

Description

Circuit board and method for manufacturing mounting board

[0001] The present disclosure relates to a circuit board and a method for manufacturing a mounting board.

[0002] In recent years, advances in electronics have led to the development of technologies for mounting electronic components on substrates. For example, technologies have been developed for mounting a large number of bare chips of semiconductor light-emitting elements, such as light-emitting diodes (hereinafter referred to as "LEDs") used in lighting, display devices, and the like, on wiring substrates. For example, Patent Document 1 discloses an invention in which semiconductor light-emitting elements are inserted and bonded into a cavity that allows for easy positioning and arrangement of multiple semiconductor light-emitting elements. Furthermore, Patent Document 2 also discloses a technology for preventing semiconductor light-emitting elements from being carried away or solder bridges from forming when mounting electronic components using a paste-like bonding material.

[0003] JP 2006-93523 A JP 2004-47772 A

[0004] In some circuit boards, terminals and bonding materials are placed inside walls made of insulating material. Electronic components are sometimes mounted on such circuit boards by filling the interior of the walls with components, mounting them using a holding member, and then using a pressure reflow machine to press the electronic components into the walls and heat them to bond them to the circuit board. In this case, excess components may remain inside the walls and on the upper part of the walls around the electronic components, preventing the electronic components from being sufficiently pressed in during the pressure reflow machine pressurization process, potentially resulting in poor connections between the bonding materials on the circuit board and the electronic components. Meanwhile, overflowing and spreading components on the substrate can contaminate the surface of the substrate.

[0005] An object of the present disclosure is to provide a circuit board and a method for manufacturing a mounting board that can suppress connection failure between the circuit board and electronic components and also suppress contamination of the substrate.

[0006] The circuit board according to the present disclosure is a circuit board comprising a substrate, at least a pair of terminals provided on the substrate, a bonding material containing a metal element arranged on the terminals, and an inner wall made of insulating material rising from the substrate in a height direction perpendicular to the main surface of the substrate, wherein the pair of terminals and the bonding material are arranged within a cavity formed in the wall, the inner wall has at least one groove formed therein that penetrates from the inner peripheral surface to the outer peripheral surface, and an outer wall made of insulating material rising from the substrate in a height direction to surround the cavity on the outer peripheral side of the inner wall.

[0007] The method for manufacturing a mounted substrate according to the present disclosure is a method for manufacturing a mounted substrate by mounting electronic components on the above-mentioned circuit board, in which components are arranged on a base material, the electronic components are arranged, and then the electronic components are joined to terminals using a pressure reflow device.

[0008] According to the present disclosure, it is possible to provide a circuit board and a method for manufacturing a mounting board that can suppress connection failure between the circuit board and electronic components and also suppress contamination of the substrate.

[0009] FIG. 1 is a schematic cross-sectional view showing an example of a mounting board including a circuit board according to an embodiment of the present disclosure. FIG. 2 is a schematic cross-sectional view showing an example of a circuit board according to an embodiment of the present disclosure. FIG. 3 is a plan view of the circuit board. FIGS. 4(a), 4(b), and 4(c) are views of a wall frame portion of an inner wall as viewed from the thickness direction. FIGS. 5(a) and 5(b) are cross-sectional views showing an example of a structure near a recessed portion. FIG. 6 is a cross-sectional view of an example of an outer wall. FIGS. 7(a), 7(b), and 7(c) are schematic views showing an example of a method for manufacturing a circuit board and a mounting board. FIG. 8 is a schematic view showing an example of a method for manufacturing a circuit board and a mounting board. FIGS. 9(a), 9(b), 9(c), 9(d), 9(e), and 9(f) are schematic views showing an example of a method for manufacturing a wall portion. FIG. 10 is a schematic cross-sectional view showing a circuit board according to a comparative example. FIG. 11 is a view showing a circuit board according to a modified example. FIG. 12 is a view showing a circuit board according to a modified example. FIG. 13 is a view showing a circuit board according to a modified example. FIGS. 14(a) and 14(b) are views showing a circuit board according to a modified example. 15(a), 15(b), and 15(c) are diagrams showing circuit boards according to modified examples; 16(a), 16(b), and 16(c) are diagrams showing circuit boards according to modified examples; and 17(a), 17(b), 17(c), and 17(d) are diagrams showing circuit boards according to modified examples.

[0010] A circuit board 3 according to an embodiment of the present disclosure will be described with reference to Figures 1 to 3. Figure 1 is a schematic cross-sectional view showing a mounting substrate 1 including a circuit board 3 according to an embodiment of the present disclosure. Figure 2 is a schematic cross-sectional view showing the circuit board 3 according to an embodiment of the present disclosure. Figure 3 is a plan view of the circuit board 3.

[0011] 1, the mounting substrate 1 includes an electronic component 2 and a circuit board 3. The mounting substrate 1 is configured by mounting the electronic component 2 on the circuit board 3 via a bonding material 4.

[0012] The electronic component 2 includes a main body 6 and a pair of terminals 7. The main body 6 is a member for fulfilling the function of the electronic component 2. The terminals 7 are metal portions formed on the main surface of the main body 6. The terminals 7 may be made of a metal such as Cu, Ti, Au, Ni, Sn, Bi, P, B, In, Ag, Zn, Pd, Mo, Pt, or Cr, or an alloy selected from at least two of these metals. The electronic component 2 may be formed, for example, of a micro LED. The micro LED is a component that emits light in response to input from the circuit board 3.

[0013] The circuit board 3 includes a substrate 8, an inner wall 9, an outer wall 40, and a pair of terminals 10 (a first terminal and a second terminal). The substrate 8 is a flat body of the circuit board 3. The substrate 8 has a main surface 8a. The substrate 8 may be a printed circuit board for mounting the conductor patterns and electronic components of the circuit board 3 on the main surface 8a. A known resin material or ceramic material used for printed circuit boards may be used as the material of the substrate 8. Note that the following description may be given using XYZ coordinates set for the circuit board 3. The X-axis direction (second direction) is a direction parallel to the main surface 8a of the substrate 8, the Y-axis direction (third direction) is a direction parallel to the main surface 8a of the substrate 8 and perpendicular to the X-axis direction, and the Z-axis direction (first direction, height direction) is a direction perpendicular to the main surface 8a of the substrate 8.

[0014] An inner wall 9 made of insulating material is provided on the main surface 8a of the substrate 8. The inner wall 9 protrudes from the substrate 8 toward the positive side in the Z-axis direction. As shown in FIG. 3 , in this embodiment, the inner wall 9 has wall frame portions 13A, 13B, 13C, and 13D provided on all four sides. The wall frame portions 13A and 13B face each other while being spaced apart in the X-axis direction and extend parallel to the Y-axis direction. The wall frame portion 13A is disposed on the positive side of the X-axis direction, and the wall frame portion 13B is disposed on the negative side. The wall frame portions 13C and 13D face each other while being spaced apart in the Y-axis direction and extend parallel to the X-axis direction. The wall frame portion 13C is disposed on the positive side of the Y-axis direction, and the wall frame portion 13D is disposed on the negative side. The wall frame portion 13A connects the positive ends of the wall frame portions 13C and 13D in the X-axis direction. The wall frame portion 13B connects the negative ends of the wall frame portions 13C and 13D in the X-axis direction. This results in the inner wall 9 having a rectangular frame-like structure when viewed in the height direction. The wall frame portions 13A and 13B form the short sides, and the wall frame portions 13C and 13D form the long sides. While the dimensions are not particularly limited, the dimension of the wall frame portions 13A and 13B in the Y-axis direction may be set to 10 μm to 60 μm. The dimension of the wall frame portions 13C and 13D in the X-axis direction may be set to 15 μm to 70 μm. The dimension of the short side of the inner peripheral surface of the interior of the inner wall 9 may be set to 8 μm or more and 44 μm or less. The dimension of the long side of the inner peripheral surface of the interior of the inner wall 9 may be set to 15 μm or more and 68 μm or less. The dimension of the short side of the inner circumferential surface of the interior of the inner wall 9 is the dimension in the Y-axis direction between the inner circumferential surface 13a of the wall frame portion 13C and the inner circumferential surface 13a of the wall frame portion 13D. The dimension of the long side of the inner circumferential surface of the interior of the inner wall 9 is the dimension in the X-axis direction between the inner circumferential surface 13a of the wall frame portion 13A and the inner circumferential surface 13a of the wall frame portion 13B. As the material for the inner wall 9, for example, a resin material such as epoxy resin, acrylic resin, phenol resin, melamine resin, urea resin, or alkyd resin is used. Epoxy resin or acrylic resin is particularly preferably used as the material for the inner wall 9.

[0015] The outer wall 40 made of insulating material is provided on the main surface 8a of the substrate 8. The inner wall 9 protrudes from the substrate 8 toward the positive side in the Z-axis direction. The outer wall 40 is formed on the outer periphery of the inner wall 9 to surround the cavity 11. As shown in FIG. 3 , in this embodiment, the outer wall 40 has wall frame portions 41A, 41B, 41C, and 41D provided on all four sides. The wall frame portions 41A and 41B face each other while being spaced apart in the X-axis direction and extend parallel to each other in the Y-axis direction. The wall frame portion 41A is disposed on the positive side of the X-axis direction, and the wall frame portion 41B is disposed on the negative side. The wall frame portion 41A faces the wall frame portion 13A of the inner wall 9 at a distance on the positive side of the X-axis direction. The wall frame portion 41B faces the wall frame portion 13B of the inner wall 9 at a distance on the negative side of the X-axis direction. The wall frame portions 41C and 41D face each other at a distance in the Y-axis direction and extend parallel to the X-axis direction. The wall frame portion 41C is located on the positive side of the Y-axis direction, and the wall frame portion 41D is located on the negative side. The wall frame portion 41C faces the wall frame portion 13C of the inner wall 9 at a distance on the positive side of the Y-axis direction. The wall frame portion 41D faces the wall frame portion 13D of the inner wall 9 at a distance on the negative side of the Y-axis direction. The wall frame portion 41A connects the ends of the wall frame portions 41C and 41D on the positive side in the X-axis direction. The wall frame portion 41B connects the ends of the wall frame portions 41C and 41D on the negative side in the X-axis direction. As a result, the outer wall 40 has a rectangular frame-like structure when viewed in the height direction. The wall frame portions 41A and 41B form the short sides, and the wall frame portions 41C and 41D form the long sides. The dimensions of the outer wall 40 in the XY plane are not particularly limited, but may be any size that satisfies the volumetric relationship between the outer wall 40 and the inner wall 9, etc., which will be described later. The material of the outer wall 40 may be the same as that described for the inner wall 9. However, different materials may be used for the outer wall 40 and the inner wall 9, depending on the manufacturing process.

[0016] 1 to 3, the terminal 10 is a metal portion provided on the main surface 8a of the substrate 8. The material of the terminal 10 may be Ni, Cu, Ti, Cr, Al, Mo, Pt, Au, or an alloy selected from at least two of these metals. A conductive film 12 is formed on the upper surface of the terminal 10. The material of the conductive film 12 may be a film of Ti, Cu, Ni, Al, Mo, Cr, Ag, or the like, or a film of a mixture of metal particles and a binder.

[0017] The bonding material 4 is a member that bonds the terminal 7 of the electronic component 2 to the terminal 10 of the circuit board 3. The bonding material 4 is formed by thermally bonding and integrating the bonding material 4A on the circuit board 3 side and the bonding material 4B on the electronic component 2 side (see FIG. 8 ). The bonding material 4 may contain Sn or may be composed of an alloy containing Sn. However, the bonding material 4 is not necessarily limited to Sn-containing materials. The bonding material 4 may be composed of an alloy containing an element that lowers the melting point of Sn, in addition to Sn. Examples of elements that lower the melting point of Sn include Bi. The bonding material 4 functions as solder. As a result, the terminal 10, the conductive film 12, the bonding material 4, and the terminal 7 are stacked between the substrate 8 and the main body 6 in this order from the top surface of the substrate 8. Note that the solder bonding is performed after the terminal 10, the conductive film 12, the bonding material 4, and the terminal 7 are stacked. Therefore, after soldering, a structure is formed in which the metals of the terminal 10, the conductive film 12, the bonding material 4, and the terminal 7 are melted and diffused. Such a structure after soldering may include a brittle intermetallic compound (IMC). If an intermetallic compound, which has a brittle structure, is present, it is prone to fracture due to external stress, and reliability is likely to decrease. Therefore, surrounding the electronic component 2 with the inner wall 9 has the effect of protecting the electronic component 2.

[0018] A cavity 11 is formed in the inner wall 9. The cavity 11 is formed by a through-hole that penetrates the inner wall 9 in the height direction. As a result, the top surface of the substrate 8 is exposed at the bottom side of the cavity 11. The cavity 11 is rectangular when viewed in the height direction (see FIG. 3 ). The terminals 7, 10, conductive film 12, and bonding material 4 are disposed in the cavity 11 surrounded by the inner wall 9, and are thereby surrounded by the inner wall 9 on all sides. Small gaps are formed between the terminals 7, 10, conductive film 12, and bonding material 4 and the inner circumferential surfaces 13 a of the four wall frame portions 13A, 13B, 13C, and 13D that constitute the cavity 11.

[0019] Within the cavity 11, a component 20 is disposed between the electronic component 2 and bonding material 4 and the inner wall 9. This supports the electronic component 2 with the component 20, making it less likely to peel off from the circuit board 3. Furthermore, the force applied to the electronic component 2, bonding material 4, and terminals 7 and 10 is alleviated, improving reliability. Examples of materials used for the component 20 include epoxy resin, acrylic resin, phenolic resin, melamine resin, urea resin, alkyd resin, and mixtures thereof, as well as mixtures of the above resin materials with SiOx, ceramics, and the like. Epoxy resin and acrylic resin are particularly preferred. The viscosity of the component 20 during filling is preferably 1 Pa to 20 Pa, and more preferably 5 Pa to 10 Pa.

[0020] As shown in Fig. 2, the circuit board 3 has a configuration in which the electronic component 2 and the constituent material 20 have been removed from the mounting board 1 shown in Fig. 1. In the circuit board 3, a bonding material 4A containing a metal element is disposed above the terminal 10 (on the upper surface of the conductive film 12). The circuit board 3 includes a bonding material 4A (first bonding material) disposed on the terminal 10 on the X-axis direction side, and a bonding material 4A (second bonding material) disposed on the terminal 10 on the negative side in the X-axis direction. As described above, these bonding materials 4A constitute part of the bonding material 4 in a stage prior to thermally bonding the electronic component 2 and the mounting board 1. In the state of the circuit board 3, the pair of terminals 10, the conductive film 12, and the bonding material 4A are disposed within an inner wall 9 formed by an insulating material.

[0021] As shown in FIG. 3 , each of the wall frame portions 13A, 13B, 13C, and 13D has at least one groove 30 that penetrates from the inner peripheral surface 13a to the outer peripheral surface 13b. The X-axis direction is the thickness direction of the wall frame portions 13A and 13B. Therefore, the groove 30 of the wall frame portions 13A and 13B extends in the X-axis direction and penetrates the wall frame portions 13A and 13B. The Y-axis direction is the thickness direction of the wall frame portions 13C and 13D. Therefore, the groove 30 of the wall frame portions 13C and 13D extends in the Y-axis direction and penetrates the wall frame portions 13C and 13D. It is sufficient that the groove 30 is formed in at least one of the wall frame portions 13A, 13B, 13C, and 13D. Furthermore, multiple grooves 30 may be formed in any one of the wall frame portions 13A, 13B, 13C, and 13D. Furthermore, grooves 30 may be formed in the corners of each of the wall frame portions 13A, 13B, 13C, and 13D (details will be described later).

[0022] Next, with reference to Figures 4(a), (b), and (c), the configuration of the wall frame portion 13D as viewed from the thickness direction will be described. Figure 4(a) is a view of the wall frame portion 13D as viewed from the Y-axis direction, which is the thickness direction. Note that while Figures 4(a), (b), and (c) illustrate the wall frame portion 13D, the same description applies to the other wall frame portions 13A, 13B, and 13C. As shown in Figure 4(a), when viewed from the Y-axis direction, which is the thickness direction of the wall frame portion 13D, the groove portion 30 extends from the tip portion 13c in the height direction of the wall frame portion 13D (in this embodiment, the Z-axis direction) toward the substrate 8 (the negative side in the Z-axis direction). The groove portion 30 has a bottom surface 30a and a pair of side surfaces 30b. The bottom surface 30a is formed on the negative side of the Z-axis direction relative to the tip portion 13c. The pair of side surfaces 30b extend from both ends of the bottom surface 30a in the X-axis direction to the tip portion 13c. 4A, the groove 30 extends to the main surface 8a of the substrate 8. In this case, the main surface 8a of the substrate 8 forms the bottom surface 30a of the groove 30. In this configuration, the groove 30 separates the region on the negative side in the X-axis direction of the wall frame 13D from the region on the positive side in the X-axis direction.

[0023] As shown in Fig. 4(b) , the width of the groove 30 in the X-axis direction (width direction) is greater on the tip 13c side than on the bottom 30a side. The width of the groove 30 at the tip 13c is greater than the width of the groove 30 at the bottom 30a. In the example shown in Fig. 4(b) , the groove 30 opens more in the X-axis direction toward the tip 13c side. The pair of side surfaces 30b are inclined so that the distance between them increases toward the positive side in the Z-axis direction.

[0024] 4(c), the bottom surface 30a of the groove portion 30 may be disposed at a position spaced apart from the substrate 8. A member of the wall frame portion 13D is present between the bottom surface 30a and the main surface 8a of the substrate 8. Note that the height dimension of the groove portion 30 when the bottom surface 30a is spaced apart from the substrate 8 is not particularly limited, and may be 1 μm or more.

[0025] The width of the groove 30 is not particularly limited as long as it is not too small to allow excess component material 20 to be discharged. For example, the width of the groove 30 may be 1 μm or more, or 4 μm or more. The wall frame 13 only needs to be large enough to position the electronic component 2, and the width of the groove 30 may be set large (see, for example, FIG. 17( d)). Even in this case, it is possible to hold the necessary component material 20 and discharge excess material. Furthermore, when the bottom surface 30 a is positioned away from the substrate 8, the bottom surface 30 a may be curved.

[0026] The relationship between the sizes of the inner wall 9 and the outer wall 40 will now be described. As shown in FIG. 2, the relationship between the thickness Ti of the inner wall 9 and the thickness To of the outer wall 40 is not particularly limited. As will be described later, in the case of an outer wall 40 formed in a pattern (approximately uniformly deposited) of a continuous insulating material covering the main surface 8a of the substrate 8, the thickness To will be very large. In the case of a frame-shaped outer wall 40 as shown in FIGS. 1 to 3, the thickness Ti of the inner wall 9 may be greater than or equal to the thickness To of the outer wall 40. The thicknesses Ti and To are the dimensions of the wall frame portions 13A, 13B, 41A, and 41B in the X-axis direction. The thicknesses Ti and To are the dimensions of the wall frame portions 13C, 13D, 41C, and 41D in the Y-axis direction. Although not particularly limited, the thickness Ti of the inner wall 9 may be set to be greater than or equal to 1 μm and less than the height Hi of the inner wall 9. The thickness To of the outer wall 40 may be set to be greater than or equal to 1 μm and less than the height Ho of the outer wall 40. As will be described later, the cross-sectional shapes of the wall frame portions 13A, 13B, 13C, 13D, 41A, 41B, 41C, and 41D may not be constant in the height direction (see, for example, Figure 5(a)), and when comparing thicknesses Ti and To, the thicknesses at the bottom, i.e., the position of the base material 8, may be compared.

[0027] The height Hi of the inner wall 9 may be equal to or greater than the height Ho of the outer wall 40. The heights Hi and Ho are height-direction dimensions of the wall frame portions 13A, 13B, 13C, 13D, 41A, 41B, 41C, and 41D. Although not particularly limited, the height Hi of the inner wall 9 may be set to be equal to or greater than 4 μm and equal to or less than 10 μm. The height Ho of the outer wall 40 may be set to be equal to or greater than 1 μm and equal to or less than the height Hi of the inner wall 9. When the heights of the tip portions 13c and 41c of the walls are not uniform, the heights Hi and Ho are defined as the maximum heights.

[0028] As shown in Fig. 3, a rectangular reference shape T1 is set as the smallest area circumscribing the inner peripheral surface 13a of the cavity 11 of the inner wall 9 when viewed from the height direction. A rectangular reference shape T2 is set as the largest area inscribing the outer peripheral surface 13b of the inner wall 9 when viewed from the height direction. In this embodiment, the reference shapes T1 and T2 are rectangular. These reference shapes T1 and T2 are set imaginarily and are shown by imaginary lines in Fig. 3. The volume S1 inside the cavity 11 is determined by multiplying the reference shape T1 by the height Hi of the inner wall 9 (see Fig. 2).

[0029] A rectangular annular space SP is formed between the inner wall 9 and the inner peripheral surface 41a of the outer wall 40. The component 20 discharged from the cavity 11 is accommodated in the space SP. The area of ​​the space SP when viewed from the height direction is the area of ​​the region between the rectangle formed by the inner peripheral surface 41a of the outer wall 40 and the reference shape T2 on the outer peripheral side of the inner wall 9. The height of the space SP is the height of the lower of the inner wall 9 and the outer wall 40. In the example shown in FIG. 2 , the relationship between the heights of the inner wall 9 and the outer wall 40 is "Hi≧Ho." The region lower than the reference position SP1 indicating the height Ho of the outer wall 40 becomes the space SP. Therefore, the volume of the space SP, calculated by multiplying the area by the height Ho of the outer wall 40, is defined as S2.

[0030] 1 , an electronic component 2 is mounted in the cavity 11. This electronic component 2 is a member that pushes out a component 20 that was filled in the cavity 11 before bonding. The maximum volume of the pushed-out component 20 can be considered to be the volume that the electronic component 2 occupies in the cavity 11 after bonding. The volume of the portion of the electronic component 2 that enters the cavity 11, i.e., the volume of a region (denoted as PE) that is positioned lower than the tip end 9 a of the inner wall 9, is defined as the volume that the electronic component 2 occupies in the cavity 11, and this volume is defined as S3.

[0031] As described above, the volume inside the cavity 11 is S1, the volume of the space SP between the inner wall 9 and the outer wall 40 is S2, and the volume occupied by the electronic components mounted in the cavity 11 is S3. In this case, S2 may be equal to or smaller than S1 (S2≦S1), or may be equal to or larger than S3 (S2≧S3).

[0032] As shown in FIG. 5A , one of the surfaces extending in the height direction of at least one of the inner wall 9 and the outer wall 40 has a recessed portion 45 located closer to the substrate 8 in the height direction. A cavity material 46 covering the substrate 8 may be provided at the position of the recessed portion 45. The surfaces extending in the height direction of the inner wall 9 are the inner circumferential surface 13 a, the outer circumferential surface 13 b, and the side surface 30 b of the groove portion 30. The surfaces extending in the height direction of the outer wall 40 are the inner circumferential surface 41 a and the outer circumferential surface 41 b. Any one of these surfaces 13 a, 13 b, 30 b, 41 a, and 41 b may have the recessed portion 45. Furthermore, the recessed portion 45 does not need to be provided over the entire area of ​​each surface 13 a, 13 b, 30 b, 41 a, and 41 b; it may be provided only partially. The recessed portion 45 is formed closer to the substrate 8 in the height direction than the tip portions 13 c and 41 c. The recessed portion 45 is formed at a position spaced upward from the main surface 8a of the substrate 8. Thus, a cavity material 46 is formed between the recessed portion 45 and the main surface 8a of the substrate 8. The recessed portion 45 may extend in the direction in which the surfaces 13a, 13b, 30b, 41a, and 41b extend along the planar direction of the substrate 8. For example, when the inner peripheral surface 13a of the wall frame portion 13A has the recessed portion 45, the recessed portion 45 may be formed to extend in the Y-axis direction. Furthermore, when the side surface 30b of the groove portion 30 of the wall frame portion 13A has the recessed portion 45, the recessed portion 45 may be formed to extend in the X-axis direction.

[0033] The opening width of the recess 45, i.e., the height dimension w1 of the opening, is not particularly limited but may be set to 0 μm or more and 3 μm or less. The thickness of the cavity material 46, i.e., the height dimension w2, is not particularly limited but may be set to 0 μm or more and 1 μm or less. The depth dimension D1 of the recess 45 is not particularly limited but may be set to 0 μm or more and 3 μm or less. In the example shown in FIG. 5( b ), the recess 45 is formed directly above the substrate 8, and no cavity material 46 is formed. Such a structure reduces the bonding strength between the walls 9, 40 and the substrate 8, so the structure shown in FIG. 5( a ) is preferable. However, the structure shown in FIG. 5( b ) is not excluded.

[0034] The cross-sectional shape of the frame-shaped outer wall 40 will be described with reference to Figure 6. The thickness of the wall frame portion 41 of the outer wall 40 at the tip 41c in the height direction is Tto, the thickness at the end 41d on the substrate 8 side is Tbo, and the height of the wall frame portion of the outer wall is Ho. In the case of a tapered shape in which the end 41d on the substrate 8 side is thicker than the tip 41c as shown in Figure 6, the condition for the tapered shape is that Tbo is equal to or greater than Tto and is equal to or greater than Ho. Note that in the case of a shape such as that shown in Figure 5(b), the tip 41c may be thicker than the end 41d on the substrate 8 side. In this case, the condition for the tapered shape is that Tto is equal to or greater than Tbo and is equal to or greater than Ho.

[0035] A manufacturing method for the circuit board 3 and the mounting board 1 will be described with reference to FIGS. 7( a), 7( b), 7(c), and 8. First, as shown in FIG. 7( a), terminals 10 are formed on the upper surface of the substrate 8. Next, as shown in FIG. 7( b), inner walls 9 and outer walls 40 are formed on the substrate 8. This completes the circuit board 3. In FIG. 7( b), a conductive film 12 and a bonding material 4A are formed on the upper surface of the terminal 10. Next, as shown in FIG. 7( c), the component 20 is filled into the cavity 11, thereby placing the component 20 on the substrate 8. Then, the electronic component 2 is held by a holding member and mounted in the cavity 11. Next, as shown in FIG. 8, the electronic component 2 is pressed into the cavity 11 using a pressure reflow device 49, bringing the bonding material 4A and the bonding material 4B into contact inside the component 20. At this time, a portion of the component 20 is pushed into the groove 30 (see FIG. 3). At this time, the extruded component material 20 is received in the space SP between the outer wall 40 and the inner wall 9. Next, by heating, the bonding material 4B of the electronic component 2 and the bonding material 4A of the base material 8 are bonded together. In this way, the mounting substrate 1 is completed.

[0036] Next, a method for forming the inner wall 9 and the outer wall 40 having the groove portion 30 will be described with reference to Figures 9(a), (b), (c), (d), (e), and (f). First, as shown in Figure 9(a), the inner wall 9 and the outer wall 40 are formed on the substrate 8. Next, as shown in Figure 9(b), a laser is irradiated onto the inner wall 9 using a laser device 51, thereby processing a portion of the inner wall 9. As a result, the groove portion 30 is formed in the inner wall 9 as shown in Figure 9(c).

[0037] Alternatively, as shown in Fig. 9(d), a resist 52 is formed on the substrate 8. Next, as shown in Fig. 9(e), exposure is performed using a glass mask 53 having a pattern corresponding to the shape of the inner wall 9 having the groove portion 30 and the shape of the outer wall 40. As shown in Fig. 9(f), the exposed resist 52 is developed to form the inner wall 9 having the groove portion 30 and the outer wall 40.

[0038] Next, the functions and effects of the method for manufacturing the circuit board 3 and the mounting board 1 according to this embodiment will be described.

[0039] First, a circuit board 103 according to a comparative example will be described with reference to Figure 10. The inner wall 9 of the circuit board 103 does not have the groove 30 or outer wall 40 described above. After filling the interior of the inner wall 9 with the component 20, if an electronic component 2 is mounted inside the inner wall 9 using a holding member and an attempt is made to press the electronic component 2 into the inner wall 9 using a pressure reflow device, the electronic component 2 cannot be pressed in sufficiently due to the influence of the excess component 20. In this case, reflow is performed with the bonding material 4B of the electronic component 2 and the bonding material 4A of the circuit board 3 still spaced apart, which may result in poor connection between the bonding material 4A of the circuit board 3 and the electronic component 2.

[0040] In contrast, in the circuit board 3 according to this embodiment, a pair of terminals 10 (first and second terminals) are disposed within a cavity 11 surrounded by an inner wall 9. The inner wall 9 has at least one groove 30 extending from the inner peripheral surface 13 a to the outer peripheral surface 13 b. In this case, a component 20 is disposed within the cavity 11, an electronic component 2 is mounted using a holding member, and the electronic component 2 is pressed into the cavity 11 using a pressure reflow soldering apparatus and heated and bonded to the circuit board 3. When the electronic component 2 is mounted on the circuit board 3, excess component 20 can be expelled through the groove 30 to the outside of the inner wall 9. This allows the electronic component 2 to be sufficiently pressed into the cavity 11 and brought into contact with the bonding material 4 during the pressure application process using the pressure reflow soldering apparatus. Furthermore, an outer wall 40 made of an insulating material is provided on the outer peripheral side of the inner wall 9, rising from the substrate 8 in the Z-axis direction (first direction) to surround the cavity 11. Therefore, the outer wall 40 can block the excess component material 20 discharged through the groove 30, thereby preventing the component material 20 from spreading onto the main surface 8a of the base material 8. As a result, poor connection between the bonding material 4 of the circuit board 3 and the electronic component 2 can be prevented, and contamination of the base material 8 can also be prevented.

[0041] The circuit board 3 may include a bonding material 4A (first bonding material) containing a metal element disposed on the terminal 10A, and a bonding material 4A (second bonding material) containing a metal element disposed on the terminal 10B. In this case, the electronic component 2 can be mounted on the terminals 10A and 10B via the bonding material 4A.

[0042] The height Hi of the inner wall 9 may be equal to or greater than the height Ho of the outer wall 40. In this case, by increasing the height of the inner wall 9, it becomes easier to pressurize the electronic component 2 against the cavity 11 of the inner wall 9.

[0043] If the volume of the space between the inner wall 9 and the outer wall 40 is S2 and the volume occupied by the electronic components mounted in the cavity is S3, S2 may be equal to or greater than S3. In this case, the space SP between the outer wall 40 and the inner wall 9 can have a volume sufficient to accommodate the component 20 discharged from the cavity 11.

[0044] A recess 45 may be formed on the surface extending in the Z-axis direction of at least one of the inner wall 9 and the outer wall 40, on the substrate 8 side in the Z-axis direction, and a cavity material 46 covering the substrate 8 may be provided at the position of the recess 45. With this shape, the recess 45 can function as a guide groove through which the component 20 passes, on the substrate 8 side. This improves the fluidity of the component 20.

[0045] When the thickness of the wall frame portion 41 of the outer wall 40 at the tip end 41 c in the Z-axis direction is Tto, the thickness at the end 41 d on the base material side is Tbo, and the height of the wall frame portion 41 of the outer wall 40 is Ho, the condition for a tapered shape may be satisfied where Tbo is equal to or greater than Tto and equal to or greater than Ho. This configuration may be adopted when the outer wall 40 is formed in a frame shape.

[0046] When viewed from the thickness direction of the wall frame 13 of the inner wall 9, the groove 30 extends from the tip of the wall frame 13 in the Z-axis direction toward the base material 8, and the width of the groove 30 in the width direction perpendicular to the thickness direction and the Z-axis direction may be larger on the tip 13c side than on the bottom surface 30a side. In this case, narrowing the groove 30 on the base material 8 side increases the flow resistance, allowing the necessary components to be retained, and widening the groove 30 on the tip side makes it easier to discharge excess components.

[0047] The method for manufacturing the mounting board 1 according to this embodiment is a method for manufacturing the mounting board 1 by mounting the electronic components 2 on the circuit board 3 described above, in which the components 20 are placed on the base material 8, the electronic components 2 are placed, and then the electronic components 2 are joined to the terminals 10 using a pressure reflow device 49.

[0048] In this case, the same functions and effects as those of the circuit board 3 described above can be obtained.

[0049] The present disclosure is not limited to the above-described embodiment. For example, the number and arrangement of terminals on the circuit board are not particularly limited. Furthermore, although one electronic component 2 is arranged within the inner wall 9 in the above-described embodiment, multiple electronic components 2 may be arranged. The arrangement of the multiple electronic components 2 is not particularly limited.

[0050] In the above-described embodiment, the grooves 30 are formed in each of the wall frame portions 13A, 13B, 13C, and 13D. Alternatively, or in addition, the grooves 30 may be formed in the corners of the inner wall 9. For example, the configuration shown in FIG. 11 may be employed. In the example shown in FIG. 11 , the grooves 30 are formed in the four corners of the rectangular frame-shaped inner wall 9. A reference line SL is a line connecting the corners of imaginary reference shapes T1 and T2 set for the inner wall 9. In this case, the grooves 30 may extend along the direction of the reference line SL. As a result, the grooves 30 penetrate the inner wall 9 at the corners of the reference shape T1 on the inner periphery and the corners of the reference shape T2 on the outer periphery. Note that recesses 45, as shown in FIGS. 5( a ) and 5 ( b ), may also be formed in the corners of the grooves 30.

[0051] The structure of the outer wall 40 is not particularly limited, and the structure shown in FIG. 12 may be employed. In the example shown in FIG. 12 , instead of having a frame-like shape, the outer wall 40 has a pattern (approximately uniformly formed) formed of a continuous insulating material covering the main surface 8a of the substrate 8. This pattern is formed by continuously applying the insulating material to the main surface 8a of the substrate 8. In the following description, such a pattern may be referred to as a continuous pattern, and a film formed with such a pattern may be referred to as a continuous film. For example, as shown in FIG. 15( c), the outer wall 40 of the continuous pattern extends to the outer wall 40 of the adjacent cavity 11 and has an integrated shape. In other words, there is no gap in the outer wall 40 between the adjacent cavities 11. When covering a wide area of ​​the surface of the substrate 8, not just the periphery of the cavity 11, the surface of the substrate 8 can be protected by the outer wall 40. When the regions between the cavities 11 are covered without any gaps by the outer wall 40, the surface of the substrate 8 in those regions can be protected by the outer wall 40. The vicinity of the edge of the substrate 8 may or may not be covered by the outer wall 40.

[0052] Here, when the outer wall 40 is configured by a wide film, a continuous film, or the like, an end 41d on the inner circumferential surface 41a of the outer wall 40 that is on the substrate 8 side in the height direction may be located more inward than the tip 41c, as shown in Fig. 13. In Fig. 13, a position PG2 of the end 41d on the inner circumferential surface 41a that is on the substrate 8 side is located more inward than a position PG1 of the tip 41c. In this case, on the outer circumferential surface 13b of the inner wall 9, an end 13d on the substrate 8 side is located more outward than the tip 13c.

[0053] As shown in Figures 14(a) and 14(b) and 15(a), 15(b), and 15(c), various variations may be adopted for the structure of the outer wall 40. As shown in Figure 14(a), multiple inner walls 9 may be provided within the outer wall 40. That is, the outer wall 40 may collectively surround the cavities 11 of the multiple inner walls 9. Specifically, multiple (three) inner walls 9 are arranged in parallel between the wall frame portion 41C and the wall frame portion 41D. The wall frame portion 41A and the wall frame portion 41B sandwich the multiple inner walls 9 arranged in series in the opposing direction.

[0054] In FIG. 14( a ), when viewed from the height direction, SA1 denotes the area of ​​the cavity 11 within each inner wall 9, and SA2 denotes the total area between the n number of inner walls 9 and the outer wall 40. Area SA1 is the area of ​​the reference shape T1 on the inner periphery side relative to the inner wall 9. SA2 is the value obtained by subtracting the total area of ​​n number of reference shapes T2 on the outer periphery side of the inner wall 9 from the area of ​​the rectangle defined by the inner periphery 41 a of the outer wall 40. In FIG. 14( a ), three inner walls 9 are provided, so “n = 3.” In this case, the following formulas (1) and (2) may be satisfied. In this case, the outer wall 40 can simultaneously receive the components 20 discharged from the multiple inner walls 9. Furthermore, the space between the outer wall 40 and the multiple inner walls 9 can secure a volume necessary to receive the discharged components 20. SA2≧(n×SA1) / 3 (1) SA2≦n×SA1 (2)

[0055] As shown in Fig. 14(b), an outer wall 40B made of a continuous film may be combined with a frame-shaped outer wall 40A. In Fig. 14(b), two inner walls 9 are surrounded by outer walls 40A made of a continuous film, and one inner wall 9 is surrounded by a frame-shaped outer wall 40B. In the outer walls 40A made of a continuous film, an outer wall 40Aa corresponding to one inner wall 9 and an outer wall 40Ab corresponding to the other inner wall 9 are connected to each other. As a result, the outer wall 40A is configured as a single film pattern including a plurality of outer walls 40Aa, 40Ab.

[0056] 14(a) and 14(b) illustrate a configuration in which inner walls 9 arranged in a single row are surrounded by outer walls 40. As shown in FIGS. 15(a), 15(b), and 15(c), inner walls 9 arranged in multiple rows may be surrounded by outer walls 40. The number of inner walls 9 per row and the number of rows are not limited, but here, two rows of three inner walls 9 are provided. In the example shown in FIG. 15(a), multiple rows of inner walls 9 are surrounded together by a single outer wall 40.

[0057] In the example shown in Figure 15(b), one row of inner walls 9 is surrounded by a continuous film outer wall 40C, and the other row of inner walls 9 is surrounded by a continuous film outer wall 40D. The outer wall 40C is configured as a continuous film pattern including multiple outer walls 40Ca, 40Cb, and 40Cc. The outer wall 40D is configured as a continuous film pattern including multiple outer walls 40Da, 40Db, and 40Dc. In the example shown in Figure 15(c), two rows of inner walls 9 are surrounded by a continuous film outer wall 40E. The outer wall 40E is configured as a continuous film pattern including multiple outer walls 40Ea, 40Eb, 40Ec, 40Ed, 40Ee, and 40Ef.

[0058] In the above-described embodiment and modified example, the outer wall 40 does not contact the inner wall 9. However, the outer wall 40 may partially contact the inner wall 9 as long as the effects of the present disclosure are obtained. In this case, the outer wall 40 can support the inner wall 9 that is subjected to pressure. For example, the structures shown in FIGS. 16( a), (b), (c) and 17( a), (b), (c), and (d) may be adopted. Note that FIGS. 16( a), (b), (c) and 17( a), (b), (c), and (d) illustrate configurations in which one outer wall 40 surrounds one inner wall 9, but these structures may also be adopted in structures such as those shown in FIGS. 14( a), (b), and 15( a), (b), and (c).

[0059] At least one of the four wall frame portions 41 of the outer wall 40 may contact and support the wall frame portion 13 of the inner wall 9. In the example shown in FIG. 16( a), the wall frame portion 41B supports the wall frame portion 13B. In this configuration, no space SP is formed between the wall frame portion 41B and the wall frame portion 13B. In this state, the outer wall 40 surrounds the cavity 11 while partially contacting the inner wall 9. In this case, the area of ​​contamination of the substrate 8 by the component 20 outside the wall frame portion 13B can be narrowed. In the example shown in FIG. 16( b), the wall frame portion 41B contacts the wall frame portion 13B via a spacer 49. In this configuration, a space SP is formed between the wall frame portion 41B and the wall frame portion 13B. In the example shown in FIG. 16( c), the width of the wall frame portion 13B supported by the spacer 49 is narrowed to match the shape of the spacer 49. Therefore, the width of the grooves 30 on both sides of the wall frame portion 13B is increased.

[0060] As shown in Figures 17(a), 17(b), 17(c), and 17(d), among the four wall frame portions 41, multiple wall frame portions 41 may contact the wall frame portion 13 of the inner wall 9. In the example shown in Figure 17(a), wall frame portions 41A and 41B on two sides support the wall frame portions 13A and 13B. In this configuration, a space SP is formed at two locations: the wall frame portions 41C and 41D and the wall frame portions 13C and 13D. In this state, the outer wall 40 surrounds the cavity 11 while contacting the inner wall 9 on two sides. In the example shown in Figure 17(b), wall frame portions 41A, 41B, and 41C on three sides support the wall frame portions 13A, 13B, and 13C. In this configuration, a space SP is formed at one location: the wall frame portion 41D and the wall frame portion 13D. In this state, the outer wall 40 surrounds the cavity 11 while contacting the inner wall 9 on three sides. In the example shown in Fig. 17(c), the four wall frame portions 41A, 41B, 41C, and 41D are in contact with the wall frame portions 13A, 13B, 13C, and 13D via spacers 49. In this configuration, a space SP is formed between the four wall frame portions 41 and the wall frame portion 13. In the example shown in Fig. 17(c), the widths of the wall frame portions 13A, 13B, 13C, and 13D supported by the spacers 49 are reduced to match the shape of the spacers 49.

[0061] [Examples] Examples of the mounting board according to the present disclosure will be described below, but the present disclosure is not limited to the following examples.

[0062] First, the mounting boards of Examples 1 to 7 were fabricated using the following manufacturing method. First, an inner wall 9 having a groove 30 and an outer wall 40 were formed on a substrate 8 so as to surround the terminals 10 and the bonding material 4, thereby obtaining a circuit board 3. Next, a component 20 was filled into the circuit board 3, and an LED chip was mounted as the electronic component 2. Next, the mounting board 1 in this state was pressurized at 0.01 MPa in a pressure reflow device 49 and reflowed at 150°C to 190°C. This resulted in bonding of the circuit board 3 and the electronic component 2. The various conditions for Examples 1 to 7 are shown in Tables 1 and 2 below. In Table 1, the "inner wall (inner) opening width W1" refers to the longitudinal dimension of the reference shape T1 on the inner periphery side of the inner wall 9 (see FIG. 3). The "inner wall (inner) opening width L1" refers to the lateral dimension of the reference shape T1 on the inner periphery side of the inner wall 9 (see FIG. 3). The "inner wall frame width (bottom)" is the thickness Ti of the wall frame portion 13 of the inner wall 9 at the position of the base material 8 (see FIG. 2). The "inner wall (outer) opening width W2" is the longitudinal dimension of the reference shape T2 on the outer periphery of the inner wall 9 (see FIG. 3). The "inner wall (outer) opening width L2" is the lateral dimension of the reference shape T2 on the outer periphery of the inner wall 9 (see FIG. 3). The "inner wall height" is the height Hi of the inner wall 9 (see FIG. 2). The "groove opening position" indicates the position of the groove 30. "Top, bottom, left, right" means that the groove 30 is located at the center of each of the wall frame portions 13A, 13B, 13C, and 13D, and "square" means that the groove 30 is located at the corner where the wall frame portions 13A, 13B, 13C, and 13D intersect. The "groove opening top width" is the width dimension of the groove 30 at the tip 13c. In Table 2, "Resist Opening Bottom" refers to the bottom width of the groove portion 30. "Margin" refers to the distance between the inner wall 9 and the outer wall 40. "Outer wall (inner) opening width W1" refers to the longitudinal dimension of the rectangle formed by the inner peripheral surface 41a of the outer wall 40 (see Figure 3). "Outer wall (inner) opening width L1" refers to the lateral dimension of the rectangle formed by the inner peripheral surface 41a of the outer wall 40 (see Figure 3). "Outer wall frame width bottom" refers to the thickness To of the wall frame portion 41 of the outer wall 40 at the position of the substrate 8 (see Figure 2). Note that examples (other than Example 7) for which dimensions are listed have the configuration shown in Figure 11. Examples 3 and 6, which are described as "solid film," have the configuration shown in Figure 12, which has a continuous film. "Outer wall height" refers to the height Ho of the outer wall 40 (see Figure 2)."Inner wall / outer wall joint" indicates whether or not there is a portion where the outer wall 40 is joined to the inner wall 9. Example 7 has the configuration shown in Fig. 17(a).

[0063] Table 3 below shows the evaluation results for Examples 1 to 7. The evaluation results shown in Table 3 are for the number of sample circuit boards 3 shown in the "Number of Mounted" column, which were then mounted with electronic components 2. The "Component Material Flow-Out of Outer Wall" column in Table 3 indicates whether or not there were any samples in which the component material 20 flowed out onto the outer wall 40. There was no flow-out in any of Examples 1 to 7. The "Electronic Component Mounting Failure" column indicates whether or not there were any defective products in which electronic components 2 could not be mounted on the circuit board 3. There were no defective products in any of Examples 1 to 7. The "Electronic Component Mounting Rate" column indicates the percentage of samples in which electronic components 2 could be mounted on the circuit board 3. The mounting rate was 100% in all of Examples 1 to 7. The "OK" column indicates the number of samples that met all evaluation criteria. All 28 samples met the OK criteria in all of Examples 1 to 7. The "Volume Within Inner Wall" column in Table 3 indicates the volume S1 within the cavity 11. "Chip occupied volume" refers to the volume S3 occupied by the electronic component 2 within the cavity 11. "Inner-outer wall volume" refers to the volume S2 of the space SP (see FIG. 3) between the inner wall 9 and the outer wall 40. All of Examples 1 to 7 satisfy the conditions "S2≦S1" and "S2≧S3."

[0064] [Mode 1] A circuit board comprising: a substrate having a main surface; first and second terminals provided on the main surface of the substrate; and an inner wall made of an insulating material provided on the main surface of the substrate, wherein the first and second terminals are arranged in a cavity surrounded by the inner wall, the inner wall has at least one groove penetrating from the inner peripheral surface to the outer peripheral surface, and an outer wall made of an insulating material is provided on the main surface of the substrate on the outer peripheral side of the inner wall so as to surround the cavity. [Mode 2] The circuit board according to Mode 1, wherein the height of the inner wall is equal to or greater than the height of the outer wall. [Mode 3] The circuit board according to Mode 1 or 2, wherein, when the volume of the space between the inner wall and the outer wall is S2 and the volume occupied by an electronic component mounted in the cavity is S3, S2 is equal to or greater than S3. [Mode 4] The circuit board according to any one of Modes 1 to 3, wherein a surface of at least one of the inner wall and the outer wall extending in a first direction orthogonal to the main surface of the substrate has a recessed portion located on the substrate side in the first direction, and a cavity material covering the substrate is provided at the position of the recessed portion. [Mode 5] The circuit board according to any one of Modes 1 to 4, wherein an end portion of the inner peripheral surface of the outer wall that is located on the substrate side in the first direction orthogonal to the main surface of the substrate is located more inward than the tip portion. [Mode 6] The circuit board according to any one of Modes 1 to 5, wherein a condition for a tapered shape is satisfied in which Tbo is equal to or greater than Tto and equal to or greater than Ho, where Tto is the thickness of the wall frame portion of the outer wall at the tip end in the first direction orthogonal to the main surface of the substrate, Tbo is the thickness of the wall frame portion of the outer wall at the end end on the substrate side, and Ho is the height of the wall frame portion of the outer wall. [Mode 7] The circuit board according to any one of Modes 1 to 6, wherein a plurality of n inner walls are provided within the outer wall, and when viewed from a first direction orthogonal to the main surface of the base, the area within each inner wall is SA1 and the total area between the plurality of inner walls and the outer wall is SA2, the following equations (1) and (2) hold: SA2≧(n×SA1) / 3 (1) SA2≦n×SA1 (2) [Mode 8] The circuit board according to any one of Modes 1 to 7, wherein at least a portion of the outer wall contacts the inner wall.[Mode 9] The circuit board according to any one of Modes 1 to 8, wherein, as viewed in a thickness direction of the wall frame portion of the inner wall, the groove portion extends from a tip end of the wall frame portion in a first direction orthogonal to the main surface of the base toward the base, and the width of the groove portion in a width direction orthogonal to the thickness direction and the first direction is larger on the tip end side than on the bottom side. [Mode 10] A method for manufacturing a mounted board by mounting electronic components on the circuit board according to any one of Modes 1 to 9, comprising: arranging components on the base, arranging the electronic components, and then bonding the electronic components to the terminals using a pressure reflow machine.

[0065] 1...mounting board, 2...electronic component, 3...circuit board, 4A...bonding material, 8...substrate, 9...inner wall, 10...terminals (first terminal, second terminal), 11...cavity, 20...component, 30...groove portion, 40...outer wall, 41...wall frame portion, 41c...tip portion, 41d...end portion, 49...pressure reflow device.

Claims

1. A circuit board comprising: a substrate having a main surface; a first terminal and a second terminal provided on the main surface of the substrate; and an inner wall made of an insulating material provided on the main surface of the substrate, wherein the first and second terminals are disposed within a cavity surrounded by the inner wall, the inner wall has at least one groove portion extending from the inner peripheral surface to the outer peripheral surface, and an outer wall made of an insulating material is provided on the main surface of the substrate on the outer peripheral side of the inner wall so as to surround the cavity.

2. The circuit board according to claim 1, wherein the height of said inner wall is equal to or greater than the height of said outer wall.

3. The circuit board according to claim 1, wherein, when the volume of the space between the inner wall and the outer wall is S2 and the volume occupied by the electronic component mounted in the cavity is S3, S2 is equal to or greater than S3.

4. A circuit board as described in claim 1, wherein at least one of the inner wall and the outer wall has a surface extending in a first direction perpendicular to the main surface of the base material, the surface having a recessed portion on a side of the base material in the first direction, and a cavity material covering the board is provided at the position of the recessed portion.

5. The circuit board according to claim 1, wherein an end portion of the inner peripheral surface of the outer wall facing the substrate in a first direction perpendicular to the main surface of the substrate is positioned more inward than the tip portion.

6. The circuit board described in claim 1, wherein the condition for a tapered shape is satisfied such that Tbo is equal to or greater than Tto and equal to or greater than Ho, where Tto is the thickness of the wall frame portion of the outer wall at the tip end in a first direction perpendicular to the main surface of the base material, Tbo is the thickness of the wall frame portion of the outer wall at the end on the base material side, and Ho is the height of the wall frame portion of the outer wall.

7. The circuit board according to claim 1, wherein a plurality of n inner walls are provided within the outer wall, and when viewed from a first direction perpendicular to the main surface of the base material, the area within each inner wall is SA1, and the total area between the plurality of inner walls and the outer wall is SA2, the following formulas (1) and (2) hold: SA2≧(n×SA1) / 3 ... (1) SA2≦n×SA1 ... (2) 8. The circuit board according to claim 1, wherein the outer wall is in contact with a portion of the inner wall.

9. The circuit board according to claim 1, wherein, when viewed in a thickness direction of the wall frame portion of the inner wall, the groove portion extends from a tip end of the wall frame portion in a first direction perpendicular to the main surface of the base material toward the base material, and the width of the groove portion in a width direction perpendicular to the thickness direction and the first direction is larger on the tip end side than on the bottom surface side.

10. A method for manufacturing a mounted board by mounting electronic components on a circuit board according to any one of claims 1 to 9, comprising arranging components on the base material, arranging the electronic components, and then bonding the electronic components to the terminals using a pressure reflow device.

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