Structure having conductive pattern

Abstract

In order to provide a space-saving structure having a conductive pattern in which a plurality of circuit boards are reliably electrically connected and connected at a sufficient mechanical strength, a structure 2 is provided, comprising two or more circuit boards 4 including: a substrate body 6 having a region formed by a planar member having a predetermined thickness and having a first surface 6A and a second surface 6B that is the back surface thereof; a hollow convex through-hole 10 that is formed by a planar member, has an outer surface 12A and an upper surface 14A having a truncated-cone shape in which the first surface 6A is convex, and an inner surface 12B and a ceiling surface 14B having a truncated-cone shape in which the second surface 6B is concave, the through-hole having an opening 16 passing through the upper surface 14A and the ceiling surface 14B; a connection layer 22 in which a conductive layer (outer surface-side connection layer) 22A formed on the outer surface 12A and the upper surface 14A of the convex through-hole 10, and a conductive layer (inner surface-side connection layer) 22B formed on the inner surface 12B and the ceiling surface 14B are connected by a conductive layer 22C formed in the opening 16; and a conductive pattern 20 that is formed on at least one among the first surface 6A and the second surface 6B, and is connected to the connection layer 22, wherein an insertion-side outer surface 12A (4A), which is the outer surface 12A of the convex through-hole 10 of one circuit board 4A, and an inserted-side inner surface 12B (4B), which is the inner surface 12B of the convex through-hole 10 of the other circuit board 4B, have the same taper angle θ, the insertion-side outer surface 12A (4A) is inserted into an inner space SB surrounded by the inserted-side inner surface 12B (4B), and the insertion-side outer surface 12A (4A) on which the connection layer 22 is formed and the inserted-side inner surface 12B (4B) have a fitting structure of the hollow convex through-holes in surface-contact with each other in a crimped state.

Description

Structure with conductive pattern

[0001] The present invention relates to a structure having a conductive pattern formed by connecting a plurality of circuit boards.

[0002] In order to realize a multifunctional circuit on a circuit board having a conductive pattern formed thereon, it is desirable to electrically connect multiple circuit boards. However, connecting multiple circuit boards may require complex wiring arrangements. To avoid this, a structure has been proposed in which a conductive pin is press-fitted into a convex through-hole provided in two circuit boards to connect them (see, for example, Patent Document 1).

[0003] JP 5-90747

[0004] However, in the structure described in Patent Document 1, two circuit boards are connected using pins that are separate from the circuit boards. Therefore, even if the circuit boards are electrically connected, it is difficult to connect the circuit boards with sufficient mechanical strength. In order to connect the circuit boards with sufficient mechanical strength, additional connecting members are required, which makes it impossible to achieve space savings and increases manufacturing costs. In particular, when using a circuit board with a three-dimensional shape known as an MID (molded interconnect device), it becomes more difficult to arrange the pins and connecting members. Therefore, it is difficult to obtain a compact structure that is electrically and mechanically connected with high reliability.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a space-saving structure having a conductive pattern in which a plurality of circuit boards are reliably electrically connected and connected with sufficient mechanical strength.

[0006] The present invention encompasses the following aspects: [1] A circuit board including two or more circuit boards, the circuit board including: a substrate body having a region formed of a planar member of a predetermined thickness having a first surface and a second surface opposite the first surface; a convex through hole formed of the planar member, the convex first surface having a truncated conical outer side and top surface, and the concave second surface having a truncated conical inner side and ceiling surface, the convex first surface being a truncated conical inner side and top surface, the convex second surface having an opening penetrating between the top surface and the ceiling surface; a connection layer formed by connecting conductive layers formed on the outer side and top surface of the convex through hole and the conductive layers formed on the inner side and ceiling surface with a conductive layer formed in the opening; and a conductive pattern formed on at least one of the first surface and the second surface and connected to the connection layer, wherein an insertion-side outer side surface which is the outer side surface of the convex through hole of one of the circuit boards and an insertion-side inner side surface which is the inner side surface of the convex through hole of the other circuit board have the same taper angle, A structure having a conductive pattern, in which the inserting side outer surface is inserted into an internal space surrounded by the inserted side inner surface, and the inserting side outer surface on which the connection layer is formed and the inserted side inner surface have a fitting structure in which they are in surface contact in a crimped state.

[0007] [2] The structure according to [1], wherein the taper angle is an angle of elevation relative to a virtual bottom surface of the truncated cone-shaped convex through hole, and the taper angle is in the range of 40° to 80°.

[0008] [3] The structure according to [1] or [2], wherein the modulus of elasticity of the convex through-hole of the one circuit board is different from the modulus of elasticity of the convex through-hole of the other circuit board.

[0009] [4] The structure according to [3], wherein the modulus of elasticity of the convex through-hole of the other circuit board is smaller than the modulus of elasticity of the convex through-hole of the one circuit board.

[0010] [5] The structure according to any one of [1] to [4], wherein the hardness of the convex through-hole of the one circuit board is different from the hardness of the convex through-hole of the other circuit board.

[0011] [6] The structure according to any one of [1] to [5], wherein the thickness of the planar member covering the internal space of the convex through hole of the one circuit board is different from the thickness of the planar member covering the internal space of the convex through hole of the other circuit board.

[0012] [7] A structure according to any one of [1] to [6], wherein the inner diameter of the ceiling surface of the convex through hole of the other circuit board is smaller than the outer diameter of the top surface of the convex through hole of one of the circuit boards, and when the insertion-side outer surface and the insertion-side inner surface are in surface contact in a crimped state, there is a clearance between the top surface and the ceiling surface, and the insertion-side inner surface is in surface contact in a crimped state over the entire area of ​​the insertion-side inner surface that is closer to the insertion direction than the clearance area.

[0013] [8] The structure described in [7], wherein the one circuit board and the other circuit board have the convex through holes of the same shape, and the inserting side outer surface is inserted into an internal space surrounded by the inserted side inner surface, which has an inner diameter smaller than the outer diameter of the outer surface due to the thickness of the planar member.

[0014] [9] A structure according to any one of [1] to [8], wherein the connection layer is composed of a plurality of divided connection layers divided in the circumferential direction and insulated from each other, and when the insertion side outer surface and the inserted side inner surface on which the divided connection layers are formed are in surface contact in a crimped state, the divided connection layers formed on the insertion side outer surface and the inserted side inner surface are arranged at the same position in the circumferential direction.

[0015]

[10] The structure described in [9], wherein the conductive pattern formed on the first surface is connected to one of the split connection layers, and the conductive pattern formed on the second surface is connected to the other of the split connection layers.

[0016]

[11] The structure according to any one of [1] to

[10] , comprising two or more connecting portions that connect an end of the board body of the one circuit board with an end of the board body of the other circuit board, wherein the distance between the one circuit board and the other circuit board at the positions of the connecting portions is shorter than the distance between the one circuit board and the other circuit board at the positions of the mated convex through holes.

[0017]

[12] The structure according to any one of [1] to

[11] , wherein a plurality of the convex through holes are formed in one of the circuit boards.

[0018]

[13] The structure according to any one of [1] to

[12] , wherein three or more of the circuit boards are connected by the convex through holes.

[0019]

[14] The structure according to any one of [1] to

[13] , wherein the circuit board is a molded interconnect device (MID) having a three-dimensional shape.

[0020]

[15] The structure according to any one of [1] to

[14] , wherein 70% or more of the area of ​​the outer surface of the insertion side is in surface contact with the inner surface of the inserted side in a crimped state.

[0021] According to one aspect of the present invention, it is possible to provide a space-saving structure having a conductive pattern in which a plurality of circuit boards are reliably electrically connected and connected with sufficient mechanical strength.

[0022] 1A and 1B , showing an example of a convex through hole according to a first embodiment of the present invention, showing the cross section A-A of the cross section B-B ... FIG. 1 is a diagram schematically illustrating a first example of a structure having a conductive pattern in which circuit boards having convex through holes according to the first embodiment are stacked, in which the conductive pattern of one circuit board is electrically connected to the conductive pattern of the other circuit board. FIG. 2 is a diagram schematically illustrating a second example of a structure having a conductive pattern in which circuit boards having convex through holes according to the first embodiment are stacked, in which the conductive pattern of one circuit board is electrically connected to the conductive pattern of the other circuit board. FIG. 3 is a diagram schematically illustrating a third example of a structure having a conductive pattern in which circuit boards having convex through holes according to the first embodiment are stacked, in which the conductive pattern of one circuit board is electrically connected to the conductive pattern of the other circuit board. FIG. 4 is a diagram schematically illustrating a fourth example of a structure having a conductive pattern in which circuit boards having convex through holes according to the first embodiment are stacked, in which the conductive pattern of one circuit board is electrically connected to the conductive pattern of the other circuit board. FIG. 5 is a diagram schematically illustrating a fifth example of a structure having a conductive pattern in which circuit boards having convex through holes according to the first embodiment are stacked, in which the conductive pattern of one circuit board is electrically connected to the conductive pattern of the other circuit board.1A and 1B , showing an example in which conductive patterns are formed on the first and second surfaces. FIG. 6A is a cross-sectional plan view of a second embodiment of the present invention, showing a state in which a convex through hole of one circuit board having a convex through hole according to the second embodiment is fitted to a convex through hole of another circuit board, showing the fitted state from the position of cross-section D-D in FIG. 6A. FIG. 6B is a cross-sectional plan view of a second embodiment of the present invention, showing a state in which a convex through hole of one circuit board is fitted to a convex through hole of another circuit board, showing the fitted state from the position of cross-section D-D in FIG. 6A. FIG. 6C is a cross-sectional plan view of a second embodiment of the present invention, showing a state in which a conductive pattern of one circuit board is electrically connected to a conductive pattern of another circuit board, ... 1 is a side cross-sectional view schematically showing an example of a structure having a conductive pattern in which three or more circuit boards are connected by convex through holes, and FIG. 2 is a side cross-sectional view schematically showing an example of a structure having a conductive pattern in which three or more circuit boards are connected by convex through holes.

[0023] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In each drawing, corresponding components having the same function are assigned the same reference numerals. For convenience, the embodiments may be shown separately in consideration of ease of explanation or understanding of the main points, but partial substitution or combination of configurations shown in different embodiments is possible. In the embodiments described below, descriptions of matters common to the above-mentioned embodiments will be omitted, and only differences will be described. In particular, similar effects due to similar configurations will not be mentioned sequentially in each embodiment. The size and positional relationship of components shown in the drawings may be exaggerated for clarity of explanation.

[0024] (Circuit Board) In the present invention, a structure having a conductive pattern is formed by stacking multiple circuit boards. The conductive pattern may also be referred to as a pattern conductor. The stacked circuit boards have a substrate body having a flat plate shape or any other three-dimensional shape. The substrate body can be manufactured by molding, but can also be manufactured from a material of a certain shape by laser processing or the like.

[0025] First, an overview of a circuit board constituting a structure having a conductive pattern will be described with reference to FIGS. 1A and 1B. The following description will be given taking a flat-plate-shaped substrate body as an example. FIGS. 1A and 1B are perspective views schematically showing an example of a circuit board constituting a structure having a conductive pattern according to the present invention, with FIG. 1A showing the first surface side and FIG. 1B showing the second surface side. The second surface is the reverse side of the first surface, and the state shown in FIG. 1B is achieved by rotating the circuit board 180 degrees in the direction indicated by the arrow in FIG. 1A.

[0026] The circuit board 4 shown in Figures 1A and 1B includes a board main body 6 formed of a planar member of a predetermined thickness having a first surface 6A and a second surface 6B, which is the back surface of the first surface. A planar member has a non-block shape in which the distance (thickness) between the first surface and the second surface, which is the back surface of the first surface, is small compared to the size of the first surface and the second surface, which is the back surface of the first surface. The first surface 6A and the second surface 6B, which is the back surface of the first surface, may not only be flat, but may also have any curved surface, uneven surface, bent portion, etc. The predetermined thickness of the planar member is not limited to a constant thickness, and may vary depending on the region.

[0027] The substrate body 6 described below has a flat plate shape with all areas formed of planar members, but is not limited to this. As long as it has planar members at least in the areas where the convex through holes 10 described below are arranged, a substrate body having any other three-dimensional shape, including a blocky area, can be used.

[0028] The substrate main body 6 has convex through holes 10 formed integrally with the planar member. In the illustrated example, four convex through holes 10 (10P (10P(1), 10P(2)), 10Q, 10R) are formed integrally with the substrate main body 6. Here, the convex through hole is a general term for a structure that electrically connects conductive patterns formed on both sides of a circuit board or conductive patterns of multiple stacked circuit boards via a conductive portion formed in an opening. Multiple circuit boards 4 can be electrically and mechanically connected via the convex through holes 10 that are electrically connected to the conductive patterns.

[0029] The substrate body 6 can be made of inorganic or organic materials. Examples of inorganic materials include ceramics, and examples of organic materials include resins. Suitable ceramic materials include silicon nitride sintered body, sialon sintered body, silicon carbide sintered body, alumina sintered body, and aluminum nitride sintered body. In addition to these ceramics, metals molded with insulating surfaces may also be used.

[0030] As the resin, a thermosetting resin or a thermoplastic resin can be suitably used. Examples of the thermosetting resin include epoxy resin, melamine resin, phenol resin, urea resin, and unsaturated polyester resin. Examples of the thermoplastic resin include polyethylene, polypropylene, polystyrene, ABS resin, vinyl chloride resin, methyl methacrylate resin, nylon, polyester resin, fluororesin, polycarbonate, polyacetal, polyamide, polyphenylene ether, amorphous polyarylate, polysulfone, polyethersulfone, polyphenylene sulfide, polyetheretherketone, polyimide, polyetherimide, and liquid crystal polymer.

[0031] The convex through hole 10 has a first surface 6A that is convex and has a truncated cone-shaped outer side surface 12A and a top surface 14A, and a second surface 6B that is concave and has a truncated cone-shaped inner side surface 12B and a ceiling surface 14B, and has an opening 16 that penetrates between the top surface 14A and the ceiling surface 14B. Of these convex through holes 10, different types of convex through holes 10P, 10Q, and 10R are formed in the circuit board 4 shown in Figures 1A and 1B.

[0032] The following describes in detail each type of convex through hole 10P, 10Q, 10R. Note that for parts common to all types of convex through holes, such as those in Figures 3, 4, and 8 to 10, the convex through hole is designated by reference number 10, and in the description of each type, it is designated by reference numbers 10P, 10Q, 10R, respectively.

[0033] (Convex Through Hole According to First Embodiment) First, a convex through hole 10 according to a first embodiment of the present invention will be described with reference to FIGS. 2A and 2B. FIG. 2A is a side cross-sectional view schematically showing a convex through hole according to a first embodiment of the present invention, taken along cross section A-A in FIGS. 1A and 1B, and illustrating an example in which a conductive pattern is formed on the first surface. FIG. 2B is a side cross-sectional view schematically showing a convex through hole according to a first embodiment of the present invention, taken along cross section B-B in FIGS. 1A and 1B, and illustrating an example in which a conductive pattern is formed on the second surface. In both figures, the thicknesses of the connection layer and the conductive pattern are shown thicker than they actually are.

[0034] The convex through holes 10P, 10Q according to the first embodiment are integrally molded from the same material as the substrate main body 6. However, this is not limiting, and they can also be molded from a different material from the substrate main body 6 by two-color molding or the like. The convex through holes 10P, 10Q are formed from a planar member, with a side portion 12 constituting the side of a truncated cone and an upper surface portion 14 constituting the upper surface of the truncated cone. The side portion 12 of the convex through holes 10P, 10Q is formed to have a taper angle of angle θ. Here, the taper angle θ is the angle of elevation relative to the imaginary bottom surface of the truncated cone-shaped convex through hole 10. The taper angle is the angle between the imaginary bottom surface of an imaginary cone extending from the outer side of the convex through hole 10 and the center line of the cone perpendicular to the imaginary bottom surface. In this case, the angle is 90° - θ.

[0035] An opening 16, which is a through hole, is formed in the upper surface portion 14 of the convex through holes 10P, 10Q. The bottom surface of the truncated cone is open, forming an internal space S. The outer surfaces of the convex through holes 10P, 10Q are composed of an outer surface 12A formed by the side surface portion 12 and an upper surface 14A formed by the upper surface portion 14. On the other hand, the inner surfaces of the convex through holes 10P, 10Q are composed of an inner surface 12B formed by the side surface portion 12 and a ceiling surface 14B formed by the upper surface portion 14. In other words, the internal space S is formed by being surrounded by the inner surface 12B and the ceiling surface 14B.

[0036] The convex through holes 10P, 10Q are formed with conductive connection layers 22. More specifically, as the connection layers 22, an outer surface side connection layer 22A is formed on the outer surface 12A of the convex through holes 10P, 10Q, an inner surface side connection layer 22B is formed on the inner surface 12B, and a conductive layer 22C connecting the outer surface side connection layer 22A and the inner surface side connection layer 22B is formed in the opening 16.

[0037] Furthermore, in the convex through hole 10P, a conductive pattern 20 is formed on the first surface 6A of the substrate body 6, and the conductive pattern 20 is connected to the outer surface side connection layer 22A that constitutes the connection layer 22. On the other hand, in the convex through hole 10Q, a conductive pattern 20 is formed on the second surface 6B of the substrate body 6, and the conductive pattern 20 is connected to the inner surface side connection layer 22B that constitutes the connection layer 22. In either conductive pattern 20, not only a circuit pattern but also electronic components electrically connected to the circuit pattern may be attached. Note that the conductive patterns 20 may be formed on both the first surface 6A and the second surface 6B of the substrate body 6, and the conductive patterns 20 on both surfaces may be connected by the connection layer 22. Here, the circuit pattern may also be referred to as a pattern circuit.

[0038] The conductive pattern 20 and the connection layer 22 can be formed from materials such as copper (Cu), nickel (Ni), palladium (Pd), silver (Ag), gold (Au), platinum (Pt), tin (Sn), iron (Fe), cobalt (Co), chromium (Cr), rhodium (Rh), and ruthenium (Ru), and are preferably copper-plated.

[0039] The thickness of the substrate main body 6 can be exemplified as being in the range of 0.2 mm to 5.0 mm. The thickness of the side surface portion 12 and the top surface portion 14 of the convex through holes 10P and 10Q can be exemplified as being in the range of 0.2 mm to 5.0 mm. The thickness of the top surface portion 14 of the convex through holes 10P and 10Q can be the same as or different from the thickness of the side surface portion 12. The thickness of the side surface portion 12 and the top surface portion 14 of the convex through holes 10P and 10Q can be the same as or different from the thickness of the substrate main body 6. The outer diameter of the top surface portion 14 of the truncated convex through holes 10P and 10Q can be exemplified as being in the range of 0.2 mm to 10.0 mm, and the height can be exemplified as being in the range of 0.2 mm to 10.0 mm.

[0040] (Interlocking Structure of Convex Through Hole) Next, the interlocking structure of the convex through hole 10 will be described with reference to Fig. 3. Fig. 3 is a side cross-sectional view that schematically shows the interlocking structure of the convex through hole of one circuit board and the convex through hole of the other circuit board. The connection layer formed on the outer surface of the convex through hole 10 is very thin, so it is not shown in the drawing. In Fig. 3, one circuit board 4A is shown with a light color rather than hatching to clearly show the arrows and the like.

[0041] FIG. 3 shows a portion of a structure 2 having a conductive pattern formed by connecting one circuit board 4A and another circuit board 4B by engaging a convex through hole 10. The outer surface of the convex through hole 10, i.e., the insertion-side outer surface 12A (4A), of the one circuit board 4A, is inserted into an internal space SB surrounded by the inner surface of the convex through hole 10, i.e., the receiving-side inner surface 12B (4B), of the other circuit board 4B. The shapes of the convex through hole 10 of the one circuit board 4A and the convex through hole 10 of the other circuit board 4B may be the same or different. Note that FIG. 3 shows a case where the shapes of the convex through holes 10 are different. In either case, the insertion-side outer surface 12A (4A) of the one circuit board 4A and the receiving-side inner surface 12B (4B) of the other circuit board 4B have the same taper angle θ.

[0042] Furthermore, in this embodiment, the inner diameter D2 (4B) of the ceiling surface 14B of the convex through hole 10 of one circuit board 4B is smaller than the outer diameter D1 (4A) of the top surface 14A of the convex through hole 10 of the inserted circuit board 4A. In other words, the inner diameter D2 (4B) of the end of the inserted-side inner surface 12B (4B) at the rear end in the insertion direction is smaller than the outer diameter D1 (4A) of the end of the inserted-side outer surface 12A (4A) at the rear end in the insertion direction. This ensures a predetermined clearance CT between the top surface 14A of the convex through hole 10 of one circuit board 4A and the ceiling surface 14B of the convex through hole 10 of the other circuit board 4B, even when the convex through hole 10 of one circuit board 4A is pushed all the way into the internal space SB.

[0043] Since the insertion side outer surface 12A (4A) and the inserted side inner surface 12B (4B) have the same taper angle θ, when the convex through hole 10 of one circuit board 4A is pushed to the deepest part of the internal space SB, the entire area of ​​the inserted side inner surface 12B (4B) on the insertion side closer to the insertion direction than the clearance CT area comes into surface contact with the insertion side outer surface 12A (4A) in a crimped state.

[0044] In other words, when the insertion side outer surface 12A (4A) of one circuit board 4A is inserted toward the back of the space SB surrounded by the insertion side inner surface 12B (4B) of the other circuit board 4B, the inner diameter id (h) of the insertion side inner surface 12B (4B) corresponding to the position h in the insertion direction (h = 0 at the insertion opening) becomes smaller along the taper, and when the inner diameter id (h) of the insertion side inner surface 12B (4B) matches the outer diameter D1 (4A) of the upper surface 14A of the insertion side outer surface 12A (4A), it becomes impossible to insert any further. At this time, a clearance CT is created between the upper surface 14A of the convex through hole 10 of one circuit board 4A and the ceiling surface 14B of the convex through hole 10 of the other circuit board 4B, and an interlocking structure is obtained in which the insertion side outer surface 12A (4A) on which the connection layer 22 is formed and the inserted side inner surface 12B (4B) are in face contact in a crimped state over the entire area where the insertion side outer surface 12A (4A) is inserted into the internal space SB.

[0045] This allows the first circuit board 4A and the second circuit board 4B to be connected with sufficient mechanical strength. Furthermore, since the connection layers 22 formed in the convex through holes 10 of the first circuit board 4A and the second circuit board 4B are pressure-bonded to each other, an efficient connection with low electrical contact resistance can be achieved, and additional work such as soldering is not required. Therefore, the first circuit board 4A and the second circuit board 4B can be connected at a short distance, thereby realizing a compact structure 2.

[0046] As described above, the inner diameter D2 (4B) of the ceiling surface 14B of the convex through hole 10 of the other circuit board 4B is smaller than the outer diameter D1 (4A) of the top surface 14A of the convex through hole 10 of one circuit board 4A, and when the insertion side outer surface 12A (4A) and the inserted side inner surface 12B (4B) are in surface contact in a crimped state, there is a clearance CT between the top surface 14A (4A) and the ceiling surface 14B (4B), and the entire area of ​​the inserted side inner surface 12B (4B) on the near side in the insertion direction than the area of ​​clearance CT is in surface contact with the insertion side outer surface 12A (4A) in a crimped state.

[0047] This ensures that one circuit board 4A and the other circuit board 4B are securely electrically connected, and a mating structure with sufficient mechanical strength can be obtained. Taking into account the manufacturing tolerances of the convex through hole 10, it is preferable to keep the clearance CT small within a range where the insertion-side outer surface 12A (4A) and the insertion-side inner surface 12B (4B) are securely in surface contact in a crimped state. Taking into account the elastic deformation of the convex through hole 10, there may be cases where there is no clearance and the top surface 14A of the convex through hole 10 of one circuit board 4A is in contact with the ceiling surface 14B of the convex through hole 10 of the other circuit board 4B when the insertion-side outer surface 12A (4A) and the insertion-side inner surface 12B (4B) are in surface contact in a crimped state. In this case, the conductive layer 22C formed on the upper surface 14A of the convex through hole 10 of one circuit board 4A and the conductive layer 22C formed on the ceiling surface 14B of the convex through hole 10 of the other circuit board 4B will be in electrical contact, and a more efficient electrical connection can be expected.

[0048] <Taper Angle> When the insertion-side outer surface 12A (4A) of the circuit board 4A is pressed deep into the internal space SB and presses against the insertion-side inner surface 12B (4B) of the other circuit board 4B, a wedge effect is generated by the taper angle θ. If the force pressing the insertion-side outer surface 12A (4A) deep into the internal space SB is F and the wedge effect force (full-circumferential force) perpendicular to the insertion-side outer surface 12A (4A) and the insertion-side inner surface 12B (4B) is P, then the following relationship holds: P = F / Sin(90°-θ) = F / Cos(θ). For simplicity, the friction term is omitted in the above equation. As is clear from the above equation, the larger the taper angle θ (closer to 90°), the greater the wedge effect, thereby increasing the surface pressure between the insertion-side outer surface 12A (4A) and the insertion-side inner surface 12B (4B).

[0049] On the other hand, if the specified clearance is CT, then the relationship is D1(4A) = D2(4B) + 2 × CT / Tan(θ), and therefore CT = (D1(4A) - D2(4B)) × Tan(θ) / 2 D1(4A) > D2(4B).

[0050] Furthermore, if the change in the inner diameter of the inner surface 12B is ΔD and the position change in the insertion direction (position change in the direction perpendicular to the imaginary bottom surface of the truncated cone) due to the change in inner diameter ΔD is Δh, then, as in the case of clearance CT, Δh = ΔD × Tan(θ) / 2.

[0051] As the taper angle θ increases (approaching 90°), the value of Tan(θ) increases, which increases the clearance CT and increases the positional change Δh in the insertion direction due to the change ΔD in the inner diameter of the insertion-side inner surface 12B (4B). Considering the tolerance of the resin molded body, when the taper angle θ is large, variation tends to occur in the position in the insertion direction where the inner diameter of the insertion-side inner surface 12B (4B) coincides with the outer diameter D1 (4A) of the upper surface 14A of the insertion-side outer surface 12A (4A).

[0052] For this reason, for example, when fitting circuit boards 4 having multiple convex through holes 10, there is a risk that the distance between one circuit board 4A and the other circuit board 4B will vary depending on the individual convex through holes 10. In this case, there is a risk that the circuit board 4 will bend, and the one circuit board 4A and the other circuit board 4B will not be properly connected.

[0053] Considering these conflicting factors, it can be said that the taper angle θ is preferably in the range of 40° to 80°, and more preferably in the range of 50° to 70°. When the convex through hole 10 has a taper angle θ in this range, a wedge effect can be achieved to bring the insertion-side outer surface 12A (4A) and the insertion-side inner surface 12B (4B) into strong surface contact, and variation in the distance between the one circuit board 4A and the other circuit board 4B into which the convex through hole 10 is fitted can be suppressed.

[0054] With the above-described structure, it is preferable that 70% or more of the area of ​​the insertion-side outer surface 12A (4A) is in surface contact with the insertion-side inner surface 12B (4B) in a crimped state, and it is even more preferable that 80% or more of the area is in surface contact with the insertion-side inner surface 12B (4B) in a crimped state. This allows for a strong connection between the circuit board 4A and the other circuit board 4B, and also reduces the distance between the circuit boards, resulting in a compact stacked structure.

[0055] <Elastic Modulus of Convex Through Hole> In a fitting structure in which the inserting side outer surface 12A (4A) and the inserted side inner surface 12B (4B) are in surface contact in a crimped state, it is believed that the mating convex through hole 10 elastically deforms within a small range that does not affect the connection layer 22. Therefore, to obtain a more stable fitting structure, it is preferable that the elastic modulus of the convex through hole 10 of one circuit board 4A is different from the elastic modulus of the convex through hole 10 of the other circuit board 4B. This allows the convex through hole 10 with the lower elastic modulus to be primarily elastically deformed when the convex through holes 10 are fitted together, resulting in a stable fitting structure.

[0056] Specific examples of the elastic modulus values ​​include one of the tensile elastic modulus being approximately 2000 to 25000 MPa and the other being approximately 1600 to 22000 MPa, but the present invention is not limited to this and any other elastic modulus can be used.

[0057] In this way, when the elastic modulus of the convex through hole 10 of one circuit board 4A is different from the elastic modulus of the convex through hole 10 of the other circuit board 4B, the inserting side outer surface 12A (4A) and the inserted side inner surface 12B (4B) can be made to come into surface contact in a more stable crimped state.

[0058] Since the elastic deformation is slight, it does not matter which of the mating convex through holes 10 has a smaller elastic modulus. However, deformation in the expanding direction is generally expected to result in more uniform deformation without buckling, compared to deformation in the contracting direction. From this perspective, it is more preferable that the elastic modulus of the convex through hole 10 of the other circuit board 4B, which undergoes elastic deformation in the expanding direction, be smaller than the elastic modulus of the convex through hole 10 of the one circuit board 4A. This allows more uniform elastic deformation to occur in the mating convex through holes 10, resulting in a fitting structure that provides more stable surface contact in a crimped state.

[0059] <Hardness of Convex Through Hole> The same effect as when the elastic modulus is different can be obtained by having the mating convex through holes 10 have different hardnesses. It is preferable that the hardness of the convex through holes 10 of one circuit board 4A is different from the hardness of the convex through holes 10 of the other circuit board 4B. For example, the tensile elastic modulus of one of them can be set to approximately Rockwell R65 to 100, and the tensile elastic modulus of the other can be set to approximately Rockwell R80 to 130. However, this is not limited to this, and resin materials of any hardness can be used.

[0060] In this way, when the hardness of the convex through hole 10 of one circuit board 4A is different from the hardness of the convex through hole 10 of the other circuit board 4B, the inserting side outer surface 12A (4A) and the inserted side inner surface 12B (4B) can be made to come into surface contact in a more stable crimped state.

[0061] As with the elastic modulus, it is more preferable that the hardness of the convex through-hole 10 of the other circuit board 4B, where elastic deformation in the expanding direction occurs, is lower than the hardness of the convex through-hole 10 of the one circuit board 4A.

[0062] <Thickness of the planar member covering the internal space of the convex through hole> Furthermore, the same effect as when the elastic moduli are different can be obtained by making the thickness of the planar member covering the internal space SA of the convex through hole 10 of one circuit board 4A different from the thickness of the planar member covering the internal space SB of the convex through hole 10 of the other circuit board 4B.

[0063] In this way, when the thickness of the planar member covering the internal space SA of the convex through hole 10 of one circuit board 4A is different from the thickness of the planar member covering the internal space SB of the convex through hole 10 of the other circuit board 4B, the inserting side outer surface 12A (4A) and the inserted side inner surface 12B (4B) can be made to come into surface contact in a more stable crimped state.

[0064] Furthermore, as in the case of elastic modulus, it is more preferable that the thickness of the planar member covering the internal space SB of the convex through hole 10 of the other circuit board 4B, where elastic deformation in the expanding direction occurs, is thinner than the thickness of the planar member covering the internal space SA of the convex through hole 10 of one circuit board 4A.

[0065] (Interlocking structure of convex through holes of the same shape) Next, a structure in which circuit boards 4 are connected by interlocking convex through holes 10 of the same shape will be described with reference to Fig. 4. Fig. 4 is a side cross-sectional view that schematically shows a structure in which a convex through hole of one circuit board is interlocked with a convex through hole of another circuit board in circuit boards having convex through holes of the same shape.

[0066] Figure 4 also shows a portion of a structure 2 having a conductive pattern formed by connecting one circuit board 4A and another circuit board 4B by fitting convex through holes 10. In Figure 4, convex through holes 10 of the same shape are fitted together to connect the circuit boards 4A and 4B. Therefore, the inner diameter of the inner surface 12B of the convex through hole 10 is smaller than the outer diameter of the outer surface 12A due to the thickness t of the planar member covering the internal space S. Therefore, when convex through holes 10 of the same shape are fitted together, it is believed that a predetermined clearance CT can be obtained.

[0067] To explain this in more detail, if the inner diameter of the ceiling surface 14B of the insertion-side inner surface 12B (4B) of the other circuit board 4B is D2 (4B), the outer diameter of the top surface 14A of the insertion-side outer surface 12A (4A) of one circuit board 4A is D1 (4A), and the thickness of the side portion 12 and top portion 14 of the convex through hole 10 is t, then the following relationship holds: D2 (4B) = D1 (4A) + 2 × t / Tan - 2 × t / Sin(θ).

[0068] To have clearance CT, the relationship D2(4B) < D1(4A) must be satisfied, and the relationship D1(4A) + 2 × t / Tan - 2 × t / Sin(θ) < D1(4A) must be satisfied. Rearranging the above equation, we obtain Cos(θ) < 1. Since the taper angle θ is never 90°, a predetermined clearance CT can always be maintained when convex through holes 10 of the same shape are mated. As described above, there may be cases where clearance CT is not provided, but when clearance CT is provided, unintended conduction (short circuit) between circuits can be suppressed, which is particularly effective when there is no solder resist.

[0069] In this way, when one circuit board 4A and the other circuit board 4B have convex through holes 10 of the same shape, the inserting side outer surface 12A (4A) is inserted into an internal space SB surrounded by the inserted side inner surface 12B (4B) which has an inner diameter smaller than the outer diameter of the outer surface 12A (4B) due to the thickness t of the planar member.

[0070] Since the structure 2 can be formed using the same circuit board 4, it is possible to reduce the manufacturing cost of the structure 2. At the same time, a predetermined clearance CT can be reliably secured, and the entire area of ​​the inserted-side inner surface 12B (4B) on the front side in the insertion direction of the area of ​​the clearance CT can be reliably brought into surface contact with the inserted-side outer surface 12A (4A) in a crimped state.

[0071] Although it is possible that the thickness of the top surface portion 14 of the convex through hole 10 is slightly thicker than the thickness of the side surface portion 12, it is unlikely that the top surface portion 14 would be significantly thicker from the perspective of forming the opening 16, which is a through hole. It is believed that the relationship D2(4B)<D1(4A) always holds true as long as the taper angle θ is in the range of 40° to 80°. The fitting structure described with reference to Figures 3 and 4 applies not only to the convex through hole 10 according to the first embodiment, but also to the convex through holes 10 according to all of the embodiments described below.

[0072] (Connection of Conductive Patterns Formed on Circuit Boards) Next, various modes in which the conductive pattern 20 of one circuit board 4A and the conductive pattern 20 of the other circuit board 4B are electrically connected by fitting the convex through hole 10 according to the first embodiment will be described with reference to Figures 5A to 5E. Figures 5A to 5E are diagrams that schematically show examples in which the conductive pattern of one circuit board is electrically connected to the conductive pattern of the other circuit board in a structure having a conductive pattern in which circuit boards having convex through holes according to the first embodiment are stacked, with Figure 5A showing a first example, Figure 5B showing a second example, Figure 5C showing a third example, Figure 5D showing a fourth example, and Figure 5E showing a fifth example.

[0073] 5A , both the inserting circuit board 4A and the receiving circuit board 4B have convex through holes 10P with conductive patterns 20 formed on the first surfaces 6A thereof as shown in FIG. 2A . This provides a structure 2 in which the conductive patterns 20 formed on the first surfaces 6A of the one circuit board 4A and the conductive patterns 20 formed on the first surfaces 6A of the other circuit board 4B are electrically connected.

[0074] 5B , both the circuit board 4A on the insertion side and the circuit board 4B on the receiving side have convex through holes 10Q with conductive patterns 20 formed on the second surfaces 6B as shown in FIG. 2B . This results in a structure 2 in which the conductive patterns 20 formed on the second surfaces 6B of the circuit board 4A on one side and the conductive patterns 20 formed on the second surfaces 6B of the circuit board 4B on the other side are electrically connected.

[0075] 5C , one circuit board 4A on the insertion side has a convex through hole 10Q on which a conductive pattern 20 is formed on the second surface 6B as shown in Fig. 2B , and the other circuit board 4B on the receiving side has a convex through hole 10P on which a conductive pattern 20 is formed on the first surface 6A as shown in Fig. 2A . This results in a structure 2 in which the conductive pattern 20 formed on the second surface 6B of one circuit board 4A and the conductive pattern 20 formed on the first surface 6A of the other circuit board 4B are electrically connected.

[0076] 5D , one circuit board 4A on the insertion side has a convex through hole 10P on which a conductive pattern 20 is formed on a first surface 6A as shown in Fig. 2A , and the other circuit board 4B on the receiving side has a convex through hole 10Q on which a conductive pattern 20 is formed on a second surface 6B as shown in Fig. 2B . This results in a structure 2 in which the conductive pattern 20 formed on the first surface 6A of one circuit board 4A and the conductive pattern 20 formed on the second surface 6B of the other circuit board 4B are electrically connected.

[0077] 5E , conductive patterns 20 are formed on both the first surface 6A and the second surface 6B of one circuit board 4A on the insertion side and connected by a connection layer 22, and conductive patterns 20 are formed on both the first surface 6A and the second surface 6B of the other circuit board 4B on the inserted side and connected by a connection layer 22. Thus, a structure 2 is obtained in which the conductive patterns 20 formed on both surfaces of one circuit board 4A and the other circuit board 4B are electrically connected by the mated convex through holes 10.

[0078] As described above, the convex through-hole 10 according to the first embodiment of the present invention makes it possible to obtain structures 2 having various circuit patterns.

[0079] (Convex Through Hole According to a Second Embodiment) Next, a convex through hole according to a second embodiment of the present invention will be described with reference to FIGS. 6A and 6B. FIG. 6A is a side cross-sectional view schematically illustrating a convex through hole according to a second embodiment of the present invention, showing cross section C-C in FIGS. 1A and 1B, and illustrating an example in which conductive patterns are formed on the first and second surfaces. FIG. 6B is a plan cross-sectional view, seen from cross section D-D in FIG. 6A, showing a state in which a convex through hole of one circuit board having a convex through hole according to the second embodiment is mated with a convex through hole of another circuit board. In both figures, the thicknesses of the connection layer and conductive pattern are shown thicker than they actually are. Even in this embodiment, as long as a mating structure in which surface contact is achieved in the crimped state, clearance CT may or may not exist.

[0080] As shown in Fig. 6B, the convex through hole 10R formed in the circuit board 4 according to this embodiment has a connection layer divided into two insulated split connection layers 24, 26 in the circumferential direction. A sufficient insulating space is secured between the two split connection layers 24, 26. Furthermore, the insulating space can be filled with an insulating material.

[0081] 6A and 6B , the split connection layer 24 on the left side of the convex through hole 10R has an outer surface side connection layer 24A formed on the outer surface 12A thereof, an inner surface side connection layer 24B formed on the inner surface 12B thereof, and a conductive layer 24C connecting the outer surface side connection layer 24A and the inner surface side connection layer 24B formed in the opening 16. Similarly, the split connection layer 26 on the right side of the convex through hole 10R has an outer surface side connection layer 26A formed on the outer surface 12A thereof, an inner surface side connection layer 26B formed on the inner surface 12B thereof, and a conductive layer 26C connecting the outer surface side connection layer 26A and the inner surface side connection layer 26B formed in the opening 16.

[0082] 6A , the conductive pattern 20 formed on the first surface 6A of the circuit board 4 is connected to the split connecting layer 24, and the conductive pattern 20 formed on the second surface 6B is connected to the split connecting layer 26. However, this is not limited to this, and conversely, there may be cases where the conductive pattern 20 formed on the first surface 6A of the circuit board 4 is connected to the split connecting layer 26, and the conductive pattern 20 formed on the second surface 6B is connected to the split connecting layer 24. There may also be cases where two independent conductive patterns 20 are formed on either the first surface 6A or the second surface 6B of the circuit board 4, and each is connected to the split connecting layer 24 and the split connecting layer 26.

[0083] One circuit board 4A having a convex through hole 10R on which the split connection layers 24, 26 are formed is inserted into the internal space of the other circuit board 4B having a convex through hole 10R on which the split connection layers 24, 26 are formed. Then, as shown in Figure 6B, the insertion-side outer surface 12A (4A) and the insertion-side inner surface 12B (4B) on which the split connection layers 24, 26 are formed are brought into surface contact in a crimped state. At this time, the outer surface-side connection layer 24A (4A) of the split connection layer 24 formed on the insertion-side outer surface 12A (4A) and the inner surface-side connection layer 24B (4B) of the split connection layer 24 formed on the insertion-side inner surface 12B (4B) are positioned at the same position in the circumferential direction. Similarly, the outer surface side connection layer 26A (4A) of the split connection layer 26 formed on the insertion side outer surface 12A (4A) and the inner surface side connection layer 26B (4B) of the split connection layer 26 formed on the insertion side inner surface 12B (4B) are arranged at the same position in the circumferential direction.

[0084] The conductive patterns 20 formed on the circuit boards 4A and 4B can be electrically connected by joining the split connection layers 24 formed on one circuit board 4A and the other circuit board 4B, and the conductive patterns 20 formed on the circuit boards 4A and 4B can be electrically connected by joining the split connection layers 26 formed on one circuit board 4A and the other circuit board 4B. At this time, the split connection layers 24 and the split connection layers 26 are insulated from each other.

[0085] 7A and 7B, a description will be given of an embodiment in which the conductive pattern 20 of one circuit board 4A and the conductive pattern 20 of the other circuit board 4B are electrically connected by fitting the convex through hole 10R according to the second embodiment. Figures 7A and 7B are schematic diagrams showing examples in which the conductive pattern of one circuit board is electrically connected to the conductive pattern of the other circuit board in a structure having a conductive pattern in which circuit boards having convex through holes according to the second embodiment are stacked, with Figure 7A showing a first example and Figure 7B showing a second example.

[0086] <First Example> In the first example shown in Figure 7A, by joining the split connection layers 24 together, the conductive pattern 20 formed on the first surface 6A of one circuit board 4A on the insertion side is electrically connected to the conductive pattern 20 formed on the first surface 6A of the other circuit board 4B on the inserted side, and by joining the split connection layers 26 together, a structure 2 is obtained in which the conductive pattern 20 formed on the second surface 6B of one circuit board 4A is electrically connected to the conductive pattern 20 formed on the second surface 6B of the other circuit board 4B.

[0087] <Second Example> In the second example shown in FIG. 7B , the split connection layers 24 are joined together to electrically connect the conductive pattern 20 formed on the first surface 6A of one circuit board 4A on the insertion side to the conductive pattern 20 formed on the second surface 6B of the other circuit board 4B on the inserted side, and the split connection layers 26 are joined together to obtain a structure 2 in which the conductive pattern 20 formed on the second surface 6B of one circuit board 4A to the conductive pattern 20 formed on the first surface 6A of the other circuit board 4B is electrically connected.

[0088] 1A and 1B, when the plurality of convex through holes 10P, 10Q, and 10R are arranged at asymmetric positions in a plan view, the plurality of convex through holes 10P, 10Q, and 10R of one circuit board 4A and the other circuit board 4B are fitted together at only one relative position. Therefore, when the convex through holes 10R are fitted together, the divided connection layers 24 and 26 of the fitted convex through holes 10R are always arranged at the same position in the circumferential direction.

[0089] On the other hand, when only one convex through hole 10R is provided, or when multiple convex through holes 10P, 10Q, and 10R are arranged, for example, at point-symmetric positions, the convex through hole 10R can be fitted together with one circuit board 4A and the other circuit board 4B arranged at different rotational positions relative to each other. In this case, for example, the split connecting layer 24 of one circuit board 4A can be joined to the split connecting layer 26 of the other circuit board 4B, and the split connecting layer 26 of one circuit board 4A can be joined to the split connecting layer 24 of the other circuit board 4B.

[0090] In addition, while the illustrated example has two split connection layers 24, 26 divided in half in the circumferential direction, it is also possible to have three or more split connection layers divided in three or more in the circumferential direction. Each split connection layer may be divided equally or may be divided to have different central angles. For example, in the case of having four split connection layers divided in four in the circumferential direction, two conductive patterns 20 may be formed on each of the first surface 6A and the second surface 6B, and each conductive pattern 20 may be connected to a different split connection layer.

[0091] As described above, in the convex through hole 10R of the second embodiment of the present invention, the connection layer is divided circumferentially and is composed of a plurality of split connection layers 24, 26 that are insulated from each other, and when the insertion side outer surface 12A and the inserted side inner surface 12B on which the split connection layers 24, 26 are formed come into surface contact in a crimped state, the split connection layers 24, 26 formed on the insertion side outer surface 12A and the inserted side inner surface 12B are arranged in the same position circumferentially.

[0092] As a result, the divided connection layers 24, 26 electrically connect the conductive patterns 20 formed on one circuit board 4A and the other circuit board 4B, thereby making it possible to obtain a structure 2 having various circuit patterns.

[0093] In particular, the conductive pattern 20 formed on the first surface 6A of the circuit board 4 is connected to one split connection layer 24 (26), and the conductive pattern 20 formed on the second surface 6B is connected to the other split connection layer 26 (24), thereby realizing a structure 2 having a wide variety of circuit patterns.

[0094] As described above, when multiple convex through holes 10P, 10Q, 10R are formed in one circuit board 4, a structure 2 can be realized in which various conductive patterns are connected between the circuit boards 4 by the connection layer 22 or the divided connection layers 24, 26.

[0095] (Coupling Member) As described above, one circuit board 4A and the other circuit board 4B can be reliably connected electrically and mechanically without using any other members by fitting the convex through holes 10 formed in the circuit boards 4. However, in the embodiment described below with reference to Fig. 8, the connection between the one circuit board 4A and the other circuit board 4B can be further strengthened by using a coupling member. Fig. 8 is a side cross-sectional view that schematically shows a structure in which an end of one circuit board and an end of the other circuit board are coupled by a coupling member.

[0096] In the embodiment shown in Figure 8, two connecting portions 30 are provided, connecting both ends of the board body 6 of one circuit board 4A to both ends of the board body 6 of the other circuit board 4B. The connecting portions 30 may be formed of a resin or metal material and preferably have a U-shaped side cross-sectional shape. This structure externally constrains the first surface 6A of the one circuit board 4A and the second surface 6B of the other circuit board 4B, ensuring a distance CE between the one circuit board 4A and the other circuit board 4B. This distance CE is preferably set to be smaller than the distance CB between the one circuit board 4A and the other circuit board 4B at the position of the mated convex through-hole 10.

[0097] In addition, when the circuit board 4A and the other circuit board 4B have a flat plate shape, the distance between the one circuit board 4A and the other circuit board 4B can also be referred to as the distance between the first surface 6A of the one circuit board 4A and the second surface 6B of the other circuit board 4B.

[0098] This may cause a bending moment in the board bodies 6 of the one circuit board 4A and the other circuit board 4B. In this case, a force is applied that narrows the distance CB between the first surface 6A of the one circuit board 4A and the second surface 6B of the other circuit board 4B at the position of the mated convex through hole 10. This force can further strengthen the mating between the convex through hole 10 of the one circuit board 4A and the convex through hole 10 of the other circuit board 4B.

[0099] The number of connecting portions 30 attached to the circuit board 4A and the other circuit board 4B is not limited to two, and any number of connecting portions 30 equal to or greater than three may be arranged. Furthermore, the structure of the connecting portions 30 is not limited to that shown in the figure. Any other structure may be adopted as long as it can restrain the one circuit board 4A and the other circuit board 4B and determine the distance CB between the one circuit board 4A and the other circuit board 4B.

[0100] As described above, in this embodiment, two or more connecting portions 30 are provided to connect the end of the board body 6 of one circuit board 4A to the end of the board body 6 of the other circuit board 4B, and it is preferable that the distance CE between the one circuit board 4A and the other circuit board 4B at the position of the connecting portions 30 is shorter than the distance CB between the one circuit board 4A and the other circuit board 4B at the position of the mated convex through hole 10.

[0101] This makes it possible to effectively strengthen the fit between the convex through-hole 10 of one circuit board 4A and the convex through-hole 10 of the other circuit board 4B by using the bending moment generated in the one circuit board 4A and the other circuit board 4B.

[0102] In the above description, the connecting portion 30 is applied to the circuit board 4 having a flat plate shape, but the present invention is not limited to this. The connecting portion can be applied to circuit boards having other three-dimensional shapes, and the distance CE between the two circuit boards at the position of the connecting portion can be shorter than the distance CB between the two circuit boards at the position of the mated convex through-hole 10.

[0103] (Structure with Three or More Stacked Circuit Boards) In the above embodiment, the structure 2 is basically formed by stacking two circuit boards 4A, 4B, but is not limited to this. It is also possible to realize a structure 2 with any number of two circuit boards 4, three or more, stacked. Figure 9 is a side cross-sectional view that schematically shows an example of a structure having a conductive pattern in which three or more circuit boards are connected by convex through holes.

[0104] 9 illustrates a structure 2 in which four circuit boards 4 are stacked by engaging the convex through holes 10. Connection is possible simply by engaging the convex through holes 10, and the distance between the stacked circuit boards 4 can be shortened, resulting in a compact structure 2. In this way, a stacked structure in which three or more circuit boards 4 are connected by the convex through holes 10 can realize a compact structure 2 with a variety of circuit patterns.

[0105] For example, it is possible that the convex through hole 10 of the circuit board 4 stacked at an intermediate position has a plurality of divided connection layers, some of which are not connected to the conductive pattern 20 formed on this circuit board 4, but function to electrically connect the divided connection layer of the convex through hole 10 of another circuit board 4 connected to the first surface 6A with the divided connection layer of the convex through hole 10 of another circuit board 4 connected to the second surface 6B. In that case, for example, it is possible that the conductive pattern of the bottom circuit board 4 and the conductive pattern of the top circuit board 4 of the structure 2 shown in Figure 9 are electrically connected via divided connection layers connected in multiple stages, without being connected to other conductive patterns.

[0106] (Structure in which circuit boards having a three-dimensional shape are stacked) In the above embodiment, a structure 2 in which flat circuit boards 4A and 4B are stacked is shown, but this is not limited to this. A structure 2 in which circuit boards having a three-dimensional shape are stacked as shown in FIG. 10 can also be formed. FIG. 10 is a side cross-sectional view that schematically shows an example of a structure in which three-dimensional circuit boards have conductive patterns connected by convex through holes. FIG. 10 illustrates a structure 2 in which three three-dimensional circuit boards 4 are stacked by fitting together the convex through holes 10.

[0107] A circuit board having a three-dimensional shape is also called an MID (Molded Interconnect Device). The substrate body 6 of the circuit board 4 having a three-dimensional shape is preferably made of a resin molded product. Engineering plastics can be used as the resin material used for the resin molded product. As the engineering plastic, those with excellent heat resistance are preferred, and examples of usable materials include fluororesin, polycarbonate, polyacetal, polyamide, polyphenylene ether, amorphous polyarylate, polysulfone, polyethersulfone, polyphenylene sulfide, polyetheretherketone, polyimide, polyetherimide, and liquid crystal polymer.

[0108] In the case of a circuit board 4 having a three-dimensional shape, for example, a non-conductive metal complex is dispersed in a molding resin, which is the material of the board body 6, and after this molding resin is used to mold a three-dimensional board, a laser beam is irradiated in accordance with the circuit pattern to generate metal nuclei, and then plating is applied to form a circuit.

[0109] In this way, when the circuit board 4 is an MID having a three-dimensional shape, stacking the MID circuit boards 4 makes it possible to realize a compact structure 2 with a wide variety of uses that can be used for a variety of purposes.

[0110] As described above, the structure 2 having the conductive pattern 20 according to the above embodiment of the present invention includes the substrate main body 6 having an area formed of a planar member of a predetermined thickness having a first surface 6A and a second surface 6B that is the back surface thereof, the convex through hole 10 formed of the planar member, the convex first surface 6A having a truncated cone-shaped outer side surface 12A and top surface 14A, and the truncated cone-shaped inner side surface 12B and ceiling surface 14B having a concave second surface 6B, and the convex through hole 10 having an opening 16 penetrating between the top surface 14A and the ceiling surface 14B, and the conductive layer (outer surface side connection layer) 22A formed on the outer side surface 12A and top surface 14A of the convex through hole 10 and the conductive layer (inner surface side connection layer) 22B formed on the inner side surface 12B and ceiling surface 14B and a conductive pattern 20 formed on at least one of the first surface 6A and the second surface 6B and connected to the connection layer 22. The circuit board 4 has two or more circuit boards 4, each including an insertion-side outer surface 12A (4A), which is the outer surface 12A of the convex through-hole 10 of one circuit board 4A, and an insertion-side inner surface 12B (4B), which is the inner surface 12B of the convex through-hole 10 of the other circuit board 4B, which have the same taper angle θ. The insertion-side outer surface 12A (4A) is inserted into an internal space SB surrounded by the insertion-side inner surface 12B (4B), and the insertion-side outer surface 12A (4A) on which the connection layer 22 is formed and the insertion-side inner surface 12B (4B) are in surface contact in a crimped state, thereby forming a fitting structure.

[0111] In the structure 2 described above, the insertion-side outer surface 12A (4A) and the insertion-side inner surface 12B (4B) of the truncated cone-shaped convex through hole 10 have the same taper angle θ, so the insertion-side outer surface 12A (4A) and the insertion-side inner surface 12B (4B) on which the connection layer 22 is formed can be brought into surface contact in a crimped state. Therefore, the circuit boards 4A and 4B can be connected simply by fitting the convex through hole 10, shortening the distance between the stacked circuit boards 4A and 4B, thereby achieving a compact structure 2. This makes it possible to provide a space-saving structure 2 having conductive patterns 20 in which one circuit board 4A and the other circuit board 4B are reliably electrically connected and connected with sufficient mechanical strength.

[0112] Although the embodiments and modes of implementation of the present invention have been described, the disclosed contents may vary in the details of the configuration, and changes in the combination and order of elements in the embodiments and modes of implementation may be realized without departing from the scope and spirit of the claimed invention.

[0113] 2 Structure 4 Circuit board 4A One circuit board 4B Other circuit board 6 Board body 6A First surface 6B Second surface 10 Convex through hole 12 Side portion 12A Outer surface 12B Inner surface 14 Upper surface portion 14A Upper surface 14B Ceiling surface 16 Opening 20 Conductive pattern 22 Connection layer 22A Outer surface side connection layer 22B Inner surface side connection layer 22C Conductive layer 24 Divided connection layer 24A Outer surface side connection layer 24B Inner surface side connection layer 24C Conductive layer 26 Divided connection layer 26A Outer surface side connection layer 26B Inner surface side connection layer 26C Conductive layer 30 Connection portion S, SA, SB Internal space

Claims

a hollow convex through hole formed of said planar member, said first surface being a convex outer surface and top surface, and said second surface being a concave inner surface and ceiling surface, said hollow through hole having an opening penetrating between said top surface and said ceiling surface; a connection layer formed by connecting a conductive layer formed on said outer surface and top surface of said convex through hole and a conductive layer formed on said inner surface and ceiling surface by a conductive layer formed in said opening; and a conductive pattern formed on at least one of said first surface and said second surface and connected to said connection layer, wherein an insertion side outer surface which is the outer surface of said convex through hole of one of said circuit boards and an insertion side inner surface which is the inner surface of said convex through hole of the other circuit board have the same taper angle, A structure having a conductive pattern, the insertion side outer surface being inserted into an internal space surrounded by the inserted side inner surface, and the insertion side outer surface on which the connection layer is formed and the inserted side inner surface having a fitting structure in which the hollow convex through holes are in surface contact in a crimped state.

2. Two or more circuit boards including: a substrate body having an area formed of a planar member of a predetermined thickness having a first surface and a second surface which is an underside of the first surface; a hollow convex through hole formed of the planar member, the first surface being a convex truncated cone-shaped outer surface and top surface, and the second surface being a concave truncated cone-shaped inner surface and ceiling surface, the hollow through hole having an opening penetrating between the top surface and the ceiling surface; a connection layer formed by connecting a conductive layer formed on the outer surface and top surface of the convex through hole and a conductive layer formed on the inner surface and ceiling surface by a conductive layer formed in the opening; and a conductive pattern formed on at least one of the first surface and the second surface and connected to the connection layer, wherein an insertion side outer surface which is the outer surface of the convex through hole of one of the circuit boards and an insertion side inner surface which is the inner surface of the convex through hole of the other circuit board have the same taper angle, A structure having a conductive pattern, the structure having an insertion side outer surface inserted into an internal space surrounded by the inserted side inner surface, and a fitting structure between the hollow convex through holes in which the insertion side outer surface on which the connection layer is formed and the inserted side inner surface are in surface contact in a crimped state, and the elastic modulus of the convex through hole of one circuit board is different from the elastic modulus of the convex through hole of the other circuit board.

3. The structure according to claim 2, wherein the elastic modulus of said convex through-hole of said other circuit board is smaller than the elastic modulus of said convex through-hole of said one circuit board.

4. A circuit board comprising two or more circuit boards including: a substrate body having an area formed of a planar member of a predetermined thickness having a first surface and a second surface which is an underside thereof; a convex through hole formed of the planar member, the first surface being a convex truncated cone-shaped outer surface and top surface, the second surface being a convex truncated cone-shaped inner surface and ceiling surface, the convex through hole having an opening penetrating between the top surface and the ceiling surface; a connection layer formed by connecting a conductive layer formed on the outer surface and top surface of the convex through hole and a conductive layer formed on the inner surface and ceiling surface by a conductive layer formed in the opening; and a conductive pattern formed on at least one of the first surface and the second surface and connected to the connection layer, wherein an insertion side outer surface which is the outer surface of the convex through hole of one of the circuit boards and an insertion side inner surface which is the inner surface of the convex through hole of the other circuit board have the same taper angle, A structure having a conductive pattern, the structure having an interlocking structure in which the insertion side outer surface is inserted into an internal space surrounded by the inserted side inner surface, and the insertion side outer surface on which the connection layer is formed and the inserted side inner surface are in surface contact in a crimped state, the connection layer being composed of a plurality of split connection layers that are divided in the circumferential direction and insulated from each other, and when the insertion side outer surface and the inserted side inner surface on which the split connection layer is formed are in surface contact in a crimped state, the split connection layers formed on the insertion side outer surface and the inserted side inner surface are arranged at the same position in the circumferential direction.

5. The structure of claim 4, wherein the conductive pattern formed on the first surface is connected to one of the split connection layers, and the conductive pattern formed on the second surface is connected to the other of the split connection layers.

6. A circuit board comprising two or more circuit boards including: a substrate body having an area formed of a planar member of a predetermined thickness having a first surface and a second surface which is the reverse surface of the first surface; a convex through hole formed of the planar member, the first surface being a convex truncated cone-shaped outer surface and top surface, the second surface being a convex truncated cone-shaped inner surface and ceiling surface, the convex through hole having an opening penetrating between the top surface and the ceiling surface; a connection layer formed by connecting a conductive layer formed on the outer surface and top surface of the convex through hole and a conductive layer formed on the inner surface and ceiling surface by a conductive layer formed in the opening; and a conductive pattern formed on at least one of the first surface and the second surface and connected to the connection layer, wherein an insertion side outer surface which is the outer surface of the convex through hole of one of the circuit boards and an insertion side inner surface which is the inner surface of the convex through hole of the other circuit board have the same taper angle, a structure having an interlocking structure in which the insertion side outer surface is inserted into an internal space surrounded by the inserted side inner surface, and the insertion side outer surface on which the connection layer is formed and the inserted side inner surface are in surface contact in a crimped state, the structure having two or more connecting portions connecting an end of the board body of the one circuit board to an end of the board body of the other circuit board, and the distance between the one circuit board and the other circuit board at the positions of the connecting portions is shorter than the distance between the one circuit board and the other circuit board at the position of the mated convex through hole.

7. The structure according to any one of claims 1 to 6, wherein the taper angle is an elevation angle of the truncated cone-shaped convex through hole relative to a virtual bottom surface, and the taper angle is in the range of 40° to 80°.

8. The structure according to any one of claims 1 to 6, wherein the hardness of the convex through-hole of the one circuit board is different from the hardness of the convex through-hole of the other circuit board.

9. A structure described in any one of claims 1 to 6, wherein the thickness of the planar member covering the internal space of the convex through hole of the one circuit board is different from the thickness of the planar member covering the internal space of the convex through hole of the other circuit board.

10. A structure as claimed in any one of claims 1 to 6, wherein the inner diameter of the ceiling surface of the convex through hole of the other circuit board is smaller than the outer diameter of the top surface of the convex through hole of one of the circuit boards, and when the insertion side outer surface and the inserted side inner surface are in surface contact in a crimped state, there is a clearance between the top surface and the ceiling surface, and the entire area of ​​the inserted side inner surface on the near side in the insertion direction relative to the clearance area is in surface contact with the insertion side outer surface in a crimped state.

11. The structure according to claim 10, wherein the one circuit board and the other circuit board have the convex through-holes of the same shape, and the insertion side outer surface is inserted into an internal space surrounded by the inserted side inner surface, which has an inner diameter smaller than the outer diameter of the outer surface due to the thickness of the planar member.

12. The structure according to any one of claims 1 to 6, wherein a plurality of said convex through holes are formed in one said circuit board.

13. The structure according to any one of claims 1 to 6, wherein three or more of said circuit boards are connected by said convex through holes.

14. The structure according to any one of claims 1 to 6, wherein the circuit board is a molded interconnect device (MID) having a three-dimensional shape.

15. A structure according to any one of claims 1 to 6, wherein 70% or more of the area of ​​the outer surface of the insertion side is in surface contact with the inner surface of the receiving side in a pressed state.

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