Circuit board and manufacturing method

Abstract

To provide a circuit board capable of further improving heat dissipation of an electronic component such as a semiconductor chip mounted on an additional metal layer bonded to a circuit pattern by diverting an ultrasonic bonding technique, and to provide a method of manufacturing the same.SOLUTION: The circuit board 1 is provided with a circuit pattern 3 on a substrate 5, and an additional metal layer 9 is laminated and joined on the circuit pattern 3, wherein the additional metal layer 9 is provided with a mounting surface part 13 for fixing a semiconductor chip 11 with solder, and an engaging recessed and projecting part 17 for engaging a tool recessed and projecting part of a vibration transmitting tool for joining the additional metal layer 9 on the circuit pattern 3 by ultrasonic vibration.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a circuit board and a manufacturing method used to manufacture the same. [Background technology]

[0002] In recent years, the need for higher current in power devices has been increasing, while at the same time the need to reduce the cost of semiconductors has also been increasing. In response to this, there is a growing demand for the development of circuit boards that can handle high currents at low cost.

[0003] Patent Document 1 describes a conventional circuit board.

[0004] The circuit pattern of this circuit board is formed by wet etching of copper foil (Cu foil) or aluminum foil (Al foil).

[0005] In order to increase the current, it is essential to thicken the Cu foil to effectively dissipate the heat generated by electronic components such as semiconductor chips mounted on the circuit pattern. However, thickening the Cu foil increases the etching time and also reduces the dimensional accuracy of the circuit pattern.

[0006] In contrast, the wiring board described in Patent Document 2 has an overlay circuit pattern formed by cold spraying on a circuit pattern formed by etching a Cu foil. This wiring board improves heat dissipation while reducing the etching processing time by partially thickening the circuit pattern through overlaying.

[0007] However, the cold spray method is a technology that forms a coating by colliding spray material particles in a solid state with the substrate at high speed. This means that large residual stress and thermal stress tend to occur in the Cu layer of the overlay circuit pattern, raising concerns about substrate warping. Furthermore, the use of powder as the raw material leads to high costs.

[0008] In response to this problem, it is conceivable to apply the ultrasonic bonding technology described in Patent Document 3 to laminate and bond an additional metal layer such as Cu foil to a circuit pattern such as Cu foil. This bonding technology applies ultrasonic vibrations in the planar direction of the bonding surface with the circuit pattern while applying pressure to the electrode terminal with an ultrasonic horn, and the ultrasonic vibrations bond the electrode terminal to the circuit pattern.

[0009] A simple adaptation of such ultrasonic bonding technology involves applying ultrasonic vibrations in the planar direction of the bonding surface while applying pressure to the additional metal layer with an ultrasonic horn, thereby bonding the metal layer to the circuit pattern.

[0010] Therefore, there are advantages in that warping of the substrate is unlikely to occur as in the cold spray method of Patent Document 2, and expensive powder is not used.

[0011] However, the pressure applied by the ultrasonic horn leaves tool marks (grooves) on the surface of the additional metal layer, including the mounting surface of the electronic components. Therefore, when electronic components are mounted on the additional metal layer using solder, excess solder with low thermal conductivity accumulates in the tool marks and remains, limiting the improvement of the heat dissipation performance of the electronic components. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Publication No. 2002-012653 [Patent Document 2] Publication No. 2006-319146 [Patent Document 3] Publication No. 2016-096172 Summary of the Invention [Problem to be solved by the invention]

[0013] The problem to be solved is that when an additional metal layer is joined to a circuit pattern by ultrasonic bonding and electronic components are mounted on that additional metal layer by soldering, there is a limit to the improvement of the heat dissipation performance of the electronic components. [Means for solving the problem]

[0014] The circuit board of the present invention is a circuit board having a circuit pattern on a substrate, and an additional metal layer laminated and bonded on top of the circuit pattern, wherein the additional metal layer has a surface with relatively small irregularities and an engaging irregularity portion with relatively large irregularities that is provided adjacent to the relatively small irregularity surface and engages with a tool irregularity portion of a vibration transmission tool for bonding the additional metal layer onto the circuit pattern by ultrasonic vibration.

[0015] The manufacturing method for manufacturing the circuit board of the present invention includes stacking the additional metal layer on top of the circuit pattern, pressing a tool having a retracted portion and a tool asperity portion corresponding to the mounting surface portion and the engaging asperity portion against the surface of the additional metal layer and ultrasonically vibrating it, leaving the mounting surface portion on the surface of the additional metal layer in a range corresponding to the retracted portion, and forming the engaging asperity portion on the surface of the additional metal layer using the tool asperity portion, while transmitting the ultrasonic vibrations to join the additional metal layer onto the circuit pattern. [Effects of the Invention]

[0016] According to the circuit board of the present invention, an additional metal layer is laminated and bonded on top of the circuit pattern, so that the heat dissipation of electronic components fixed with solder to the relatively less uneven surface of the additional metal layer can be improved by the increased thickness of the metal layer.

[0017] The joining of the additional metal layer can be performed reliably by transmitting ultrasonic vibrations in the surface direction using a tool while the tool recesses and protrusions are engaged with the engagement recesses and protrusions of the metal layer.

[0018] Furthermore, when an electronic component is fixed to the surface of the additional metal layer with a relatively small amount of unevenness, the engaging uneven portion adjacent to the surface with a relatively small amount of unevenness can prevent the solder from flowing out.

[0019] According to the circuit board manufacturing method of the present invention, the surface of the additional metal layer has a relatively small unevenness, and the engaging unevenness used when joining by ultrasonic vibration can be utilized to suppress the outflow of solder that secures the electronic components.

[0020] The tool used in the method for manufacturing a circuit board of the present invention makes it possible to easily realize the method for manufacturing a circuit board. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic cross-sectional view of a circuit board before a semiconductor chip is mounted according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view of the circuit board after the semiconductor chip is mounted according to the first embodiment. [Figure 3] FIG. 3 is a schematic enlarged plan view of the additional copper plate after mounting the semiconductor chip according to the first embodiment. [Figure 4] FIG. 4 is a schematic enlarged cross-sectional view taken along the line IV-IV in FIG. [Figure 5] 5(A) is an enlarged schematic cross-sectional view of a main part of an additional copper plate according to a modification of Example 1, and FIG. 5(B) is an enlarged schematic cross-sectional view of a main part of an additional copper plate according to another modification of Example 1. FIG. [Figure 6] 6(A) and 6(B) are schematic cross-sectional views showing how an additional copper plate is ultrasonically bonded to a circuit pattern. [Figure 7] FIG. 7 is an enlarged cross-sectional view of a main part in a modified example of the first embodiment, showing a state in which a tool is pressed against an additional copper plate. [Figure 8] FIG. 8 is an enlarged cross-sectional view of a main part showing the mounting surface and engaging concave-convex portions of the additional copper plate according to a modified example of the first embodiment. [Figure 9] FIG. 9 is an enlarged cross-sectional view of a main part in another modification of the first embodiment, showing a state in which a tool is pressed against an additional copper plate. [Figure 10] FIG. 10 is an enlarged cross-sectional view of a main part showing the mounting surface and engaging concave-convex portions of the additional copper plate according to another modification of the first embodiment. [Figure 11]FIG. 11 is a schematic plan view of an additional copper plate before a semiconductor chip is mounted according to a second embodiment of the present invention. [Figure 12] 12A is an enlarged plan view of the main part at part XII in FIG. 11, and FIG. 12B is an enlarged cross-sectional view of the main part at part XII in FIG. [Figure 13] 13(A) and (B) relate to a modified example of the second embodiment, where FIG. 13(A) is an enlarged plan view of the main part at part XII in FIG. 11, and FIG. 13(B) is an enlarged cross-sectional view of the main part at part XII in FIG. 11. [Figure 14] 14(A) and (B) relate to a modified example of the second embodiment, where FIG. 14(A) is an enlarged plan view of the main part at part XII in FIG. 11, and FIG. 14(B) is an enlarged cross-sectional view of the main part at part XII in FIG. 11. [Figure 15] 15(A) and (B) relate to a modified example of the second embodiment, where FIG. 15(A) is an enlarged plan view of the main part at part XII in FIG. 11, and FIG. 15(B) is an enlarged cross-sectional view of the main part at part XII in FIG. 11. [Figure 16] FIG. 16 is a schematic plan view of an additional copper plate before a semiconductor chip is mounted according to the third embodiment. [Figure 17] 17(A) and 17(B) are, FIG. 17(A) is an enlarged plan view of the main part in part XVII of FIG. 16, and FIG. 17(B) is an enlarged cross-sectional view of the main part in part XVII of FIG. [Figure 18] 18(A) and (B) relate to a modified example of the third embodiment, where FIG. 18(A) is an enlarged plan view of the main part in part XVII of FIG. 16, and FIG. 18(B) is an enlarged cross-sectional view of the main part in part XVII of FIG. [Figure 19] 19(A) and (B) relate to Example 4 of the present invention, where FIG. 19(A) is a schematic plan view of an additional copper plate before a semiconductor chip is mounted, and FIG. 19(B) is a cross-sectional view of part XIX of FIG. 19(A). [Figure 20] Figures 20(A) and (B) relate to Example 4 of the present invention, where Figure 20(A) is a schematic plan view of an additional copper plate before the mounting surface portion is formed, and Figure 20(B) is a cross-sectional view of part XX in Figure 20(A). [Figure 21]21(A) and (B) relate to Example 5 of the present invention, where FIG. 21(A) is a schematic plan view of an additional copper plate before a semiconductor chip is mounted, and FIG. 21(B) is a cross-sectional view of part XXI of FIG. 21(A). [Figure 22] FIG. 22 is a schematic cross-sectional view showing a state in which an additional copper plate according to Example 5 of the present invention is ultrasonically bonded to a circuit pattern. [Figure 23] FIG. 23 is a schematic cross-sectional view showing a state in which an additional copper plate according to a modification of the fifth embodiment is ultrasonically bonded to a circuit pattern. [Figure 24] FIG. 24 is a schematic cross-sectional view showing a state in which an additional copper plate according to Example 6 of the present invention is ultrasonically bonded to a circuit pattern. DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention achieves the object of further improving the heat dissipation of a semiconductor chip mounted by soldering to an additional metal layer joined to a circuit pattern using ultrasonic bonding technology, as follows.

[0023] The circuit board of the present invention comprises a circuit pattern (3) on a substrate (5), and an additional metal layer (9) laminated and bonded onto the circuit pattern (3). The additional metal layer (9) comprises a mounting surface (13) for fixing an electronic component (11) with solder, and an engaging uneven portion (17) provided adjacent to the mounting surface (13) for engaging a tool uneven portion (15) of a vibration transmission tool (T) for bonding the additional metal layer (9) onto the circuit pattern (3) by ultrasonic vibration. The mounting surface (13) has a surface with smaller unevenness than the engaging uneven portion (17).

[0024] The mounting surface portion (13) may be a surface with less unevenness than the engaging uneven portion (17), and may be a flat surface or an uneven surface with less unevenness than the engaging uneven portion.

[0025] The engagement uneven portion (17) has an engagement protrusion (17b) that protrudes above the mounting surface portion (13). However, the protrusions and recesses of the engagement uneven portion (17) are relative, and the engagement protrusions (17b) can also be flush with the mounting surface portion (13) or lower than the mounting surface portion (13). The engagement protrusions (17b) that protrude above the mounting surface portion (13) can be raised above the mounting surface portion (13) by plastic deformation of the additional metal layer (9). The engagement protrusions (17b) can be realized as having a recess (17c) at their top or a flat surface (17d) at their top. The engagement uneven portion (17) may also have an inclined side surface (17e).

[0026] The engagement asperities (17) are impressions of the tool asperities (15). The engagement asperities (17) can also be formed by pressing a dedicated tool separate from the tool (T) for transmitting ultrasonic vibrations. The engagement asperities (17) can also be machined into the additional metal layer (9) by cutting or using a laser.

[0027] The engagement uneven portion (17) and the tool uneven portion (15) correspond 1:1 when the engagement uneven portion is formed by pressing the tool uneven portion (15), but when the engagement uneven portion (17) is processed by cutting or laser, etc., the tool uneven portion (15) can also be set to have fewer uneven portions than the engagement uneven portion (17).

[0028] The engagement unevenness 17 may be provided on the entire circumference or a part of the entire circumference surrounding the mounting surface 13. The engagement unevenness 17 may be capable of engaging with the tool unevenness 15 of the tool, transmitting ultrasonic vibrations to the additional metal layer 9, and suppressing even a part of the solder flow.

[0029] The engaging uneven portion (17) is realized by providing engaging recesses (17a) and engaging protrusions (17b) intermittently or continuously. The intermittent engaging recesses (17a) and engaging protrusions (17b) can be realized in any of the following forms: adjacent engaging recesses (17a) and engaging protrusions (17b) are aligned in the entire circumferential direction surrounding the mounting surface and in the transverse direction to the circumferential direction; they are regularly offset from each other; or they are randomly arranged. The continuous engaging uneven portion (17) can be realized in any of the following forms: the engaging recesses (17a) and engaging protrusions (17b) are continuous all around the mounting surface portion (13) or are intermittently continuous.

[0030] The manufacturing method for manufacturing a circuit board uses a tool (T) equipped with a retracted portion (21) corresponding to the mounting surface portion (13) and the engaging recessed portion (17) and a tool recessed portion (15). That is, an additional metal layer (9) is laminated on a circuit pattern (3), and the tool (T) is pressed against the surface of the additional metal layer (9) and ultrasonically vibrates. As a result, the mounting surface portion (13) remains on the surface of the additional metal layer (9) in an area corresponding to the retracted portion (21), and the tool recessed portion (15) forms the engaging recessed portion (17) on the surface of the additional metal layer (9), while the ultrasonic vibration is transmitted to bond the additional metal layer (9) onto the circuit pattern (3).

[0031] During ultrasonic vibration, a friction-reducing material (27) may be interposed between the retracted portion (21) and the surface of the additional metal layer (9), and the retracted portion (21) may be pressed against the surface of the additional metal layer (9) via the friction-reducing material (27). Alternatively, the retracted portion (21) may have a reducing unevenness portion (25) that reduces friction between the retracted portion (21) and the surface of the additional metal layer (9), and the reducing unevenness portion (25) may be pressed against the surface of the additional metal layer (9).

[0032] In the method for manufacturing a circuit board, the pressing load of the tool (T) pressed against the surface of the additional metal layer (9) may be set to such an extent that the engaging convex portion (17b) of the engaging uneven portion (17) protrudes integrally from the additional metal layer (9) more than the mounting surface portion (13).

[0033] The pressing load of the tool may be set to such an extent that a recess (17c) or a flat surface (17d) is formed at the top of the engaging protrusion (17b).

[0034] The tool (T) used in the manufacturing method of the circuit board has a retraction portion (21) corresponding to the attachment surface portion (13) and the engagement concave-convex portion (17), and a tool concave-convex portion (15). [Example]

[0035] [Circuit board] Fig. 1 is a schematic cross-sectional view of a circuit board before a semiconductor chip is mounted according to Example 1. Fig. 2 is a schematic cross-sectional view of the circuit board after a semiconductor chip is mounted.

[0036] The circuit board 1 in FIGS. 1 and 2 has a circuit pattern 3 that is thickened in part by adding an additional metal layer to meet the needs for larger currents.

[0037] The circuit board 1 is a metal-based circuit board having a circuit pattern 3 on a metal substrate 5 via an insulating layer 7. However, the circuit board 1 may also be a ceramic circuit board in which the circuit pattern 3 is formed on a ceramic substrate. The circuit pattern 3 is formed by laminating and bonding an additional copper plate 9, which is an additional metal layer. This makes the circuit pattern 3 thicker in parts, improving heat dissipation.

[0038] The circuit pattern 3 is formed of a copper material for circuits with a thickness of, for example, 0.5 mm. The thickness of the circuit pattern 3 is set taking into consideration the etching processing time, and a thickness other than 0.5 mm can also be selected. The circuit pattern 3 can also be formed of aluminum or the like.

[0039] This circuit pattern 3 is formed by etching and includes a plurality of circuit conductors 3a. The configuration of the plurality of circuit conductors 3a depends on the required characteristics of the circuit pattern 3. Note that the circuit pattern 3 may be formed in advance by pressing or cutting and attached to the metal substrate 5 via an insulating layer 7.

[0040] The metal substrate 5 is made of, for example, a single metal or an alloy, and has a thickness of, for example, 2.0 mm. The metal substrate 5 may be flexible or inflexible. Examples of materials that can be used for the metal substrate 5 include aluminum, iron, copper, an aluminum alloy, and stainless steel. The metal substrate 5 may further contain a non-metal such as carbon. For example, the metal substrate 5 may contain aluminum composited with carbon. The metal substrate 5 may have a single-layer structure or a multi-layer structure.

[0041] The metal substrate 5 has high thermal conductivity. For example, copper has a thermal conductivity of 370 to 400 W·m-1·K-1, aluminum has a thermal conductivity of 190 to 220 W·m-1·K-1, and iron has a thermal conductivity of 60 to 80 W·m-1·K-1.

[0042] The circuit board 1 may also be a metal board in the shape of a heat sink.

[0043] The insulating layer 7 not only serves to electrically insulate the circuit pattern 3 from the metal substrate 5, but also serves as an adhesive to bond them together. For this reason, a resin is generally used for the insulating layer 7, and the thickness is set to, for example, 0.13 mm.

[0044] Furthermore, since the insulating layer 7 is required to have high heat resistance against the high heat generation of the elements mounted on the circuit pattern 3 and high thermal conductivity to transfer this heat to the metal substrate 5, it is preferable that the insulating layer 7 further contains an inorganic filler.

[0045] The insulating layer 7 can be made of epoxy resin, cyanate resin, or the like. Epoxy resin is combined with, for example, an amine-based curing agent, a phenol-based curing agent, an acid anhydride-based curing agent, or an imidazole-based curing agent. Cyanate resin is combined with, for example, dicyandiamide or a phenol resin as a curing agent. The insulating layer 7 may also be made of a liquid crystal polymer such as a thermoplastic resin, such as a wholly aromatic polyester, or other thermoplastic resin.

[0046] The inorganic filler contained in the insulating layer 7 is preferably one that has excellent electrical insulation properties and high thermal conductivity, and examples thereof include alumina, silica, aluminum nitride, boron nitride, silicon nitride, magnesium oxide, etc., and it is preferable to use one or more types selected from these.

[0047] The filling rate of the inorganic filler in the insulating layer 7 can be set appropriately depending on the type of inorganic filler. For example, it is preferably 85% by volume or less, and more preferably 30 to 85% by volume, based on the total volume of the resin contained in the insulating layer 7.

[0048] The insulating layer 7 may further contain, for example, a coupling agent, a dispersant, and the like.

[0049] Alternatively, a semi-cured insulating sheet may be used as the insulating layer 7.

[0050] [Additional Metal Layer] Fig. 3 is a schematic enlarged plan view of the additional metal layer after mounting the semiconductor chip. Fig. 4 is a schematic enlarged cross-sectional view of the additional metal layer after mounting the semiconductor chip, as seen from the arrows IV-IV in Fig. 3. Figs. 5(A) and (B) relate to a modified example of Example 1, where Fig. 5(A) is a schematic enlarged cross-sectional view of a main part of a state in which a semiconductor chip is mounted on an additional copper plate having a recess at the top of the engaging protrusion, and Fig. 5(B) is a schematic enlarged cross-sectional view of a main part of a state in which a semiconductor chip is mounted on an additional copper plate having a flat portion at the top of the engaging protrusion.

[0051] 1 to 4, the additional copper plate 9, which is an additional metal layer, is formed from a copper plate material and includes an attachment surface portion 13 and an engagement uneven portion 17. Note that the additional metal layer can be made of an appropriate material depending on the circuit pattern 3, and can also be made of, for example, an additional aluminum plate made from an aluminum plate material.

[0052] The additional copper plate 9 is bonded to a selected circuit conductor 3a of the circuit pattern 3. The additional copper plate 9 is, for example, 10 mm square and 1.0 mm thick. The additional copper plate 9 is used to increase the thickness of the circuit conductor 3a, and its dimensions depend on the dimensions of the target circuit conductor 3a and semiconductor chip 11.

[0053] The mounting surface portion 13 is used to mount the semiconductor chip 11, which is an electronic component, with solder. The mounting surface portion 13 has a surface with smaller irregularities than the engagement irregularity portion 17, and in this embodiment, is entirely flat. However, the mounting surface portion 13 can also be realized with recesses or the like present in part or all of it.

[0054] The planar shape of the mounting surface portion 13 is formed similarly to the outline shape in plan view of the mounted semiconductor chip 11. The mounting surface portion 13 is set to be larger than the square semiconductor chip 11 in plan view and is set to be approximately square.

[0055] However, the planar shape of the mounting surface portion 13 may be different from the outer shape of the semiconductor chip 11 in a planar view. For example, the mounting surface portion 13 may be circular in a planar view. Furthermore, the planar shape of the mounting surface portion 13 may be smaller than the semiconductor chip 11 or may be formed to be the same as the semiconductor chip 11.

[0056] The engaging uneven portion 17 is provided adjacent to the mounting surface portion 13 and engages with a tool uneven portion 15 (described later in FIG. 7) of a vibration transmitting tool T (described later in FIG. 7) for bonding the additional copper plate 9 onto the circuit pattern 3 by ultrasonic vibration in the surface direction. This engaging uneven portion 17 is already in use to engage with the tool uneven portion 15 when the additional copper plate 9 is bonded onto the circuit pattern 3. The engaging uneven portion 17 is also provided to prevent solder from flowing out of the additional copper plate 9.

[0057] The engagement uneven portion 17 may be adjacent to the mounting surface portion 13 either at a position in contact with the outer edge of the mounting surface portion 13 or at an outer position spaced apart from the outer edge of the mounting surface portion 13 .

[0058] The engagement uneven portion 17 includes engagement recesses 17a and engagement protrusions 17b. The engagement recesses 17a and engagement protrusions 17b are provided intermittently all around the periphery of the mounting surface portion 13.

[0059] The engagement recesses 17a and engagement protrusions 17b are disposed intermittently around the entire circumference of the mounting surface 13 means that the engagement recesses 17a and engagement protrusions 17b are regularly arranged at regular intervals along each side of the square mounting surface 13. The intervals between the engagement recesses 17a and engagement protrusions 17b can also be set randomly.

[0060] The engaging recesses 17a and engaging protrusions 17b are arranged in two or three rows between each side of the square outer edge of the additional copper plate 9 and the mounting surface portion 13. The number of rows is not particularly limited and can be increased or decreased. The number of rows can also be different on each side of the square.

[0061] The engaging recess 17 a and the engaging protrusion 17 b may be provided on a part of the entire periphery surrounding the periphery of the mounting surface portion 13 .

[0062] 3 and 4, the engaging recesses 17a of the engaging uneven portion 17 are formed in a quadrangular shape in a plan view and in an inverted quadrangular pyramid shape in cross section. As a result, the engaging uneven portion 17 has inclined side surfaces 17e. The inclination here means that the side surfaces are inclined with respect to the thickness direction of the additional copper plate 9.

[0063] 4, the bottom of the engaging recess 17a of the engaging uneven portion 17 is lower than the mounting surface portion 13. The engaging uneven portion 17 may be any portion that engages with the tool uneven portion 15 (described later in FIG. 7) and prevents the solder from flowing out, and the shape of the engaging recess 17a is not particularly limited, and it may be a recess formed by a curved surface, for example.

[0064] The engaging protrusions 17b of the engaging uneven portion 17 are set to protrude from the mounting surface portion 13. The engaging uneven portion 17, including the engaging recesses 17a and the engaging protrusions 17b, is an indentation of the tool uneven portion 15, which will be described later, and the engaging protrusions 17b are formed by plastic deformation of the additional copper plate 9, protruding from the mounting surface portion 13.

[0065] The engaging protrusion 17b may have a recess 17c at the top as in the modified example of FIG. 5(A), or may have a flat surface 17d at the top as in another modified example of FIG. 5(B).

[0066] The recess 17c in Figure 5(A) is formed by a raised portion 17ca on the periphery of the opening of the engagement recess 17a. The raised portion 17ca of the engagement recess 17a that is closest to the mounting surface portion 13 is adjacent to the mounting surface portion 13 in a plan view. At the outer edge of the additional copper plate 9, the raised portion 17ca is adjacent to the flat portion 19 on the outer edge. Note that the engagement uneven portion 17 may be formed up to the outer edge of the additional copper plate 9, and the flat portion 19 on the outer edge may not be provided. The flat portion 19 is a common surface of the additional copper plate 9 before the engagement uneven portion 17 is formed, and is at the same height as the mounting surface portion 13.

[0067] When the engaging protrusion 17b has a flat surface 17d at the top, as in the other modified example of Figure 5(B), the raised portion 17ca is adjacent to the mounting surface portion 13 and the flat portion 19 of the outer edge, as in the additional copper plate 9 of the modified example of Figure 5(A).

[0068] The semiconductor chip 11 is fixed by soldering to the mounting surface portion 13. The semiconductor chip 11 is connected to other circuit conductors 3a by aluminum wires or the like, not shown.

[0069] As described above, in the circuit board 1, the additional copper plate 9 is ultrasonically bonded onto the circuit conductor 3a, thereby making the circuit pattern 3 thicker in parts.

[0070] Therefore, the heat dissipation of the semiconductor chip 11 mounted on the mounting surface 13 of the additional copper plate 9 by soldering can be improved by the increased thickness of the additional copper plate 9 .

[0071] The central mounting surface 13 of the additional copper plate 9 is flat. Therefore, when the semiconductor chip 11 is mounted on the mounting surface 13, the solder between the semiconductor chip 11 and the mounting surface 13 is prevented from remaining more than necessary. This makes it possible to prevent a decrease in the heat dissipation performance of the circuit board 1.

[0072] When the solder that fixes the semiconductor chip 11 to the mounting surface portion 13 flows out from the mounting surface portion 13 to the surrounding area during mounting of the semiconductor chip 11, the engagement uneven portion 17 can suppress the solder from flowing out. In other words, the solder can be prevented from flowing out of the additional copper plate 9.

[0073] Furthermore, since the mounting surface portion 13 is surrounded by the engagement uneven portion 17, the mounting surface portion 13 can be easily recognized and the semiconductor chip 11 can be mounted.

[0074] The engagement uneven portion 17 provided on the additional copper plate 9 has a protruding portion 17ca that protrudes from the attachment surface portion 13 as a mountain with the attachment surface portion 13 as a reference plane.

[0075] Therefore, the function of the already used engagement uneven portion 17 that prevents the solder from flowing out of the additional copper plate 9 can be further improved.

[0076] [Circuit board manufacturing method] 6(A) and 6(B) are schematic cross-sectional views of ultrasonic bonding to a circuit pattern according to Example 1. FIG. 7 is an enlarged cross-sectional view of a main part in a state where a tool is pressed against an additional copper plate in a modified example of Example 1. FIG. 8 is an enlarged cross-sectional view of a main part showing an attachment surface portion and engaging concave-convex portions of an additional copper plate according to a modified example of Example 1. FIG. 9 is an enlarged cross-sectional view of a main part in a state where a tool is pressed against an additional copper plate in another modified example of Example 1. FIG. 10 is an enlarged cross-sectional view of a main part showing an attachment surface portion and engaging concave-convex portions of an additional copper plate according to another modified example of Example 1.

[0077] The manufacturing method of the circuit board according to the embodiment of the present invention will be described by taking the modified examples shown in FIGS. 7 and 8 and the other modified examples shown in FIGS. 9 and 10 as representative examples, but the manufacturing method is also common to the examples shown in FIGS.

[0078] As shown in Figure 6, this manufacturing method uses a tool T. Note that Figure 6(A) shows an example in which a larger 12 mm square tool T is used for a 10 mm square additional copper plate 9. Figure 6(B) shows an example in which a smaller 5.8 mm square tool T is used for a 10 mm square additional copper plate 9.

[0079] The tool T has, in the cross-sectional shape of FIG. 7, a retraction portion 21 corresponding to the attachment surface portion 13 and the engagement concave-convex portion 17, and a tool concave-convex portion 15.

[0080] The tool T corresponds to the planar shape and cross-sectional shape of the additional copper plate 9 in Figures 3 and 5(A), and a retraction portion 21 is formed in the center of the flat surface on the bottom, and a tool uneven portion 15 is formed around it.

[0081] The retracted portion 21 is flat and forms a gap with respect to the mounting surface portion 13 when the tool T is pressed against the additional copper plate 9. However, the retracted portion 21 may also come into contact with the mounting surface portion 13. The retracted portion 21 may be retracted relative to the tool uneven portion 15. The retracted portion 21 is retracted to such an extent that, after the tool T has been pressed against the surface of the additional copper plate 9, the mounting surface portion 13, which has a smaller unevenness than the engagement uneven portion 17, remains. In other words, the retracted portion 21 may press the additional copper plate 9 to form the mounting surface portion 13 during the process of pressing the tool T against the surface of the additional copper plate 9, and may come into contact with or form a gap with the mounting surface portion 13 after the pressing is completed. The surface shape of the retracted portion 21 may be any shape, including a curved surface, an uneven surface, or any other surface other than a flat surface, as long as the mounting surface portion 13 can be secured.

[0082] The tool concave-convex portion 15 has tool concave portions 15a and tool convex portions 15b that correspond to form the engaging convex portions 17b and engaging concave portions 17a of the engaging concave-convex portion 17, and are provided intermittently all around the periphery of the retraction portion 21. The cross sections of the tool concave portions 15a and the tool convex portions 15b are trapezoidal with their cross sections facing inversely relative to each other. The tip 15ba of the tool convex portion 15b is a flat surface corresponding to the bottom 17aa of the engaging concave portion 17a.

[0083] In the manufacturing method of this embodiment using this tool T, the additional copper plate 9 is stacked on top of the circuit pattern 3, and the tool T is pressed against the surface of the additional copper plate 9 to apply ultrasonic vibrations. As a result, the attachment surface portion 13 remains on the surface of the additional copper plate 9 in a range corresponding to the retracted portion 21, and the tool uneven portion 15 forms the engaging uneven portion 17 on the surface of the additional copper plate 9, while the ultrasonic vibrations are transmitted to bond the additional copper plate 9 onto the circuit conductors 3a of the circuit pattern 3.

[0084] Specifically, first, the metal substrate 5 is fixed and supported in advance by a jig or the like, and the additional copper plate 9 to be laminated on any one of the circuit conductors 3a of the circuit pattern 3 is positioned and placed.

[0085] Next, the tool T is pressed against the surface of the additional copper plate 9, and ultrasonic vibrations are transmitted in the surface direction of the circuit conductor 3a while applying pressure.

[0086] This ultrasonic vibration causes plastic flow at the joining surface, and the additional copper plate 9 is joined onto the circuit conductor 3a.

[0087] At this time, based on pressing the tool T against the surface of the additional copper plate 9, the mounting surface portion 13 is left on the surface of the additional copper plate 9 according to the retraction portion 21, and the tool uneven portion 15 forms an engaging uneven portion 17 on the surface of the additional copper plate 9.

[0088] The pressing load of the tool T against the additional copper plate 9 is set to such an extent that the engaging convex portion 17b of the engaging uneven portion 17 integrally protrudes above the mounting surface portion 13. In this case, the retracted portion 21 may form a gap with respect to the mounting surface portion 13 as shown in FIG.

[0089] 7, a protrusion 17ca is formed around the periphery of the opening of the engagement recess 17a as a mountain with the mounting surface 13 as the reference plane, and a depression 17c is left at the top of the engagement protrusion 17b as shown in Fig. 8. The engagement recess 17a is formed as a valley with the mounting surface 13 as the reference plane, and the bottom 17aa is formed flat.

[0090] In another modification of Fig. 9, the pressing load of the tool T is stronger than that in Fig. 7. With the degree of pressure applied by the pressing load of Fig. 9, the raised portion 17ca comes into contact with the flat surface in the tool recessed portion 15a, which is the lower surface of the tool T, and the top of the engaging protrusion 17b becomes the flat surface 17d.

[0091] As described above, in the manufacturing method of Example 1, ultrasonic vibrations are transmitted in the planar direction to the additional copper plate 9 while forming the engaging uneven portion 17 using the tool T, and the additional copper plate 9 is joined onto one of the circuit conductors 3a of the circuit pattern 3.

[0092] Therefore, the tool T can be pressed against the surface of the additional copper plate 9, leaving the attachment surface portion 13 on the surface of the additional copper plate 9 within a range corresponding to the retracted portion 21. The tool asperity portion 15 of the tool T forms the engagement asperity portion 17 on the surface of the additional copper plate 9, while transmitting ultrasonic vibrations to the additional copper plate 9 using the tool T, thereby bonding the additional copper plate 9 onto the circuit conductor 3a.

[0093] The tool T has tool recesses 15 on the outer periphery of the retracted portion 21 that firmly bite into the surface of the additional copper plate 9, so that good bonding between the additional copper plate 9 and the circuit conductor 3a can be achieved during ultrasonic bonding.

[0094] The circuit board 1 manufactured by this manufacturing method can be provided with the engagement concave-convex portions 17 that have already been used when transmitting ultrasonic vibrations in order to prevent the solder from flowing out.

[0095] Therefore, the mounting surface 13 of the additional copper plate 9 on which the semiconductor chip 11 is mounted can be made flat so as not to leave any more solder than necessary. A structure that prevents the solder from flowing out of the additional copper plate 9 with the already used engagement unevenness 17 can be easily obtained together with the flat mounting surface 13.

[0096] The used engagement asperities 17 left on the additional copper plate 9 by the indentation made by the tool asperities 15 can be generated by plastic deformation of the surface of the additional copper plate 9. This plastic deformation can generate protrusions 17ca around the openings of the engagement recesses 17a. These protrusions 17ca can protrude beyond the mounting surface 13 as mountains with the mounting surface 13 as a reference plane.

[0097] The additional copper plate 9 is ultrasonically bonded to the circuit conductor 3a, and therefore the processing time can be shortened compared to when the entire circuit pattern 3 is thickened and then etched.

[0098] The additional copper plate 9 generates heat due to friction between it and the circuit conductor 3a during ultrasonic bonding. However, this heat generation is localized and instantaneous, and no residual stress is generated, or at least it can be suppressed compared to the cold spray method. Therefore, warping of the substrate after bonding does not occur, or at least it can be suppressed compared to the cold spray method.

[0099] Since a bulk additional copper plate 9 is used, production can be performed at a lower cost than in the cold spray method that uses powder. [Example]

[0100] Fig. 11 relates to Example 2 of the present invention and is a schematic plan view of an additional copper plate before mounting a semiconductor chip. Fig. 12(A) is an enlarged plan view of a main part of the additional copper plate at part XII in Fig. 11, and Fig. 12(B) is an enlarged cross-sectional view of a main part of the additional copper plate at part XII in Fig. 11. Figs. 13(A) and (B) relate to a modification of Example 2, and Fig. 13(A) is an enlarged plan view of a main part of the additional copper plate at part XII in Fig. 11, and Fig. 13(B) is an enlarged cross-sectional view of a main part of the additional copper plate at part XII in Fig. 11. Figs. 14(A) and (B) relate to another modification, and Fig. 14(A) is an enlarged plan view of a main part of the additional copper plate at part XII in Fig. 11, and Fig. 14(B) is an enlarged cross-sectional view of a main part of the additional copper plate at part XII in Fig. 11. Figures 15(A) and (B) relate to yet another modified example, where Figure 15(A) is an enlarged plan view of the main part of the additional copper plate at part XII in Figure 11, and Figure 15(B) is an enlarged cross-sectional view of the main part of the additional copper plate at part XII in Figure 11.

[0101] 11, in the additional copper plate 9 of this Example 2, the adjacent engaging recesses 17a and engaging protrusions 17b of the intermittently provided engaging uneven portions 17 are arranged with misalignment. Both the engaging recesses 17a and the engaging protrusions 17b are arranged at a substantially regular pitch.

[0102] If the engaging recessed portion 17a and the engaging protruding portion 17b are arranged in a misaligned position, the outflow of solder can be more reliably prevented.

[0103] The individual shapes of the engaging uneven portions 17 of the second embodiment are as shown in FIGS.

[0104] The engaging recess 17a of the engaging uneven portion 17 in Fig. 12 is square in plan view in Fig. 12(A) and has an inverted trapezoidal cross section in Fig. 12(B). The bottom 17aa of the engaging recess 17a is formed flat, and the top of the engaging protrusion 17b is a flat surface 17d. A recess 17c similar to that in Example 1 can also be formed at the top of the engaging protrusion 17b.

[0105] 13A has a square shape in the plan view, and has an inverted pyramidal shape in the cross section of FIG. 13B. The top of the engaging protrusion 17b is the same as in FIG.

[0106] 14A is circular in the plan view of Fig. 14A, and is in the shape of an inverted cone in the cross section of Fig. 14B. The top of the engaging protrusion 17b is the same as in Fig. 12.

[0107] 15A has a circular shape in the plan view of Fig. 15A, and a curved cone shape in the cross section of Fig. 15B. The top of the engaging protrusion 17b is the same as in Fig. 12.

[0108] The tool T has tool concave-convex portions 15 formed to correspond to the engaging concave-convex portions 17 of the additional copper plate 9 .

[0109] In the second embodiment, the same effects as those in the first embodiment can be achieved.

[0110] The shape of the engaging uneven portion 17 in FIGS. 12 to 15 can also be applied to the first embodiment. [Example]

[0111] 16 to 18 relate to Example 3. Fig. 16 is a schematic plan view of the additional copper plate before mounting a semiconductor chip. Fig. 17(A) is an enlarged plan view of a main part of the additional copper plate at part XVII in Fig. 16, and Fig. 17(B) is an enlarged sectional view of a main part of the additional copper plate at part XVII in Fig. 16. Figs. 18(A) and (B) relate to a modified example of Example 3, and Fig. 18(A) is an enlarged plan view of a main part of the additional copper plate at part XVII in Fig. 16, and Fig. 18(B) is an enlarged sectional view of a main part of the additional copper plate at part XVII in Fig. 16.

[0112] As shown in Figure 16, the additional copper plate 9 of this Example 3 is provided with a continuous series of engaging recesses 17a and engaging protrusions 17b of the engaging uneven portion 17. In this Example, three similar rectangular frame-shaped engaging recesses 17a are provided so as to surround the entire periphery of the mounting surface portion 13, and the engaging protrusions 17b are formed between the engaging recesses 17a. The tops of the engaging protrusions 17b in this Example 3 are formed flat, but they can also be formed with recesses as in Example 1.

[0113] The individual shapes of the engagement concave-convex portions 17 of the third embodiment are as shown in FIGS.

[0114] The engagement recesses 17a of the engagement uneven portion 17 in Fig. 17 are formed to have a substantially uniform width in the plan view of Fig. 17(A) and have an inverted trapezoidal shape in the cross section of Fig. 17(B). The bottoms 17aa of the engagement recesses 17a are formed flat, and the tops of the engagement protrusions 17b form flat surfaces 17d. A recess 17c similar to that in Example 1 can also be formed at the tops of the engagement protrusions 17b.

[0115] The engaging recesses 17a of the engaging uneven portion 17 in Fig. 18 are formed to have a substantially uniform width in the plan view of Fig. 18(A) and have an inverted triangular shape in the cross section of Fig. 18(B). The tops of the engaging protrusions 17b are the same as in Fig. 17.

[0116] In the third embodiment, the same effects as those in the first embodiment can be achieved. [Example]

[0117] 19(A) and (B) relate to Example 4 of the present invention, where Fig. 19(A) is a schematic plan view of the additional copper plate before mounting a semiconductor chip, and Fig. 19(B) is a cross-sectional view of part XIX in Fig. 19(A). Fig. 20(A) and (B) are a schematic plan view of the additional copper plate before forming the mounting surface, and Fig. 20(B) is a cross-sectional view of part XX in Fig. 20(A). Note that Example 4 shares the basic configuration with Example 1, and therefore corresponding components are designated by the same reference numerals and redundant explanations will be omitted.

[0118] In this embodiment, as shown in FIGS. 19(A) to 20(B), the mounting surface portion 13 on the surface of the additional copper plate 9 is formed by cutting.

[0119] That is, in this embodiment, as shown in Figures 20(A) and (B), a tool T in which the tool uneven portion 15 is formed on the entire surface or the entire area in contact with the surface of the additional copper plate 9 is pressed against the additional copper plate 9 so that the tool uneven portion 15 is in contact with the entire surface of the additional copper plate 9, and ultrasonic vibration is applied.

[0120] As a result, the entire surface of the additional copper plate 9 is pressed and the engaging uneven portions 17 are formed, and the ultrasonic vibrations are transmitted to bond the additional copper plate 9 onto the circuit conductors 3a of the circuit pattern 3. This makes it possible to more reliably bond the additional copper plate 9 to the circuit conductors 3a while minimizing damage to the insulating layer 7.

[0121] 19(A) and 19(B), the mounting surface portion 13 is formed by cutting. In this embodiment, the mounting surface portion 13 has the same planar shape and cross-sectional shape as in Example 1, but is positioned lower than the bottom of the engaging recess 17a of the engaging uneven portion 17.

[0122] In this embodiment, the mounting surface portion 13 is cut into a flat surface. However, since the mounting surface portion 13 only needs to have a surface with smaller irregularities than the engaging irregularities 17, some of the engaging irregularities 17 may remain. For example, the tips of the engaging protrusions 17b may be cut off to reduce their height, and remain on the mounting surface portion 13.

[0123] In addition, the fourth embodiment can also achieve the same effects as the first embodiment. [Example]

[0124] 21(A) and (B) relate to Example 5 of the present invention, where Fig. 21(A) is a schematic plan view of the additional copper plate before mounting the semiconductor chip, and Fig. 21(B) is a cross-sectional view of part XXI in Fig. 21(A). Fig. 22 is a schematic cross-sectional view of the situation in which the additional copper plate is ultrasonically bonded to the circuit pattern. Note that Example 5 has the same basic configuration as Example 1, so corresponding configurations are assigned the same reference numerals and redundant explanations will be omitted.

[0125] 21(A) and 21(B), the mounting surface portion 13 is an uneven surface having smaller unevenness than the engagement uneven portion 17. The rest is the same as in the first embodiment.

[0126] The mounting surface 13 of this embodiment has recesses 23a and protrusions 23b that form an uneven surface. The recesses 23a and protrusions 23b are configured similarly to the engaging recesses 17a and engaging protrusions 17b, respectively, but are smaller than the engaging recesses 17a and engaging protrusions 17b. Here, "small" refers to both a small planar shape and a small cross-sectional shape, but it may also be that only one of them is small.

[0127] The protrusions 23b of the mounting surface portion 13 correspond to smaller engaging protrusions 17b in Fig. 5(A), and are formed to protrude higher than the mounting surface portion 13 due to plastic deformation of the additional copper plate 9. However, the top of the protrusions 23b of the mounting surface portion 13 is lower than the top of the engaging protrusions 17b. The protrusions 23b of the mounting surface portion 13 may also be smaller engaging protrusions 17b in Figs. 4, 5(B), and 12 to 18(B).

[0128] 22, the attachment surface portion 13 is formed when the additional copper plate 9 is bonded onto the circuit conductor 3a of the circuit pattern 3 by ultrasonic vibration using a tool T. That is, the tool T has a retracted portion 21 and a tool uneven portion 15 surrounding the retracted portion 21, as well as a reducing uneven portion 25 for reducing friction with the surface of the additional copper plate 9.

[0129] The reducing concave-convex portion 25 includes a reducing concave portion 25a and a reducing convex portion 25b. The reducing concave portion 25a and the reducing convex portion 25b are configured similarly to the tool concave portion 15a and the tool convex portion 15b, with the cross section of the reducing convex portion 25b being trapezoidal and the cross section of the reducing concave portion 27b being an inverted trapezoid.

[0130] However, the reduction recess 25a and the reduction protrusion 25b are smaller than the tool recess 15a and the tool protrusion 15b in accordance with the recess 23a and the protrusion 23b of the mounting surface portion 13. Here, "small" means that both the planar shape and the cross-sectional shape are small, as with the recess 23a and the protrusion 23b, but it may also be that only one of them is small.

[0131] The reduction protrusions 25b of this embodiment correspond to the tool protrusions 25b in Fig. 7 which are made smaller in size in accordance with the recesses 23a of the mounting surface 13. However, the reduction protrusions 25b may be made smaller in size in accordance with the recesses 23a of the mounting surface 13, or may have other shapes, such as the tool protrusions 25b in Fig. 9, etc. For example, as shown in Fig. 23, the reduction unevenness portion 25 may be in a dimple shape having convex spherical reduction protrusions 25b.

[0132] This reducing unevenness portion 25 comes into contact with the surface of the additional copper plate 9 together with the tool unevenness portion 15 when the tool T is pressed against the surface of the additional copper plate 9 laminated on the circuit pattern 3 and ultrasonic vibration is applied.

[0133] At the beginning of the ultrasonic vibration, the additional copper plate 9 is ultrasonically vibrated together with the tool T against the circuit conductor 3a. At this time, the surrounding tool concave-convex portions 15 pressurize the additional copper plate 9 while forming the engaging concave-convex portions 25, and the retracted portions 21 pressurize the additional copper plate 9 with the reducing concave-convex portions 25. As a result, the tool T applies ultrasonic vibration while applying pressure to the entire area of ​​the additional copper plate 9, thereby ensuring reliable joining of the additional copper plate 9 to the circuit conductor 3a.

[0134] When the additional copper plate 9 and the circuit conductor 3a are joined, the tool T ultrasonically vibrates against the additional copper plate 9, and the friction between the retracted portion 21 of the tool T and the additional copper plate 9 at this time can be reduced by the friction reducing uneven portion 25. As a result, the temperature rise of the additional copper plate 9 can be suppressed, and damage to the insulating layer 7 can be reduced.

[0135] In addition, the fifth embodiment can also achieve the same effects as the first embodiment. [Example]

[0136] 24 is a schematic cross-sectional view of ultrasonically bonding an additional copper plate to a circuit pattern according to Example 6 of the present invention. Note that Example 6 has a basic configuration in common with Example 1, and therefore the same reference numerals are used to designate corresponding components, and redundant explanations will be omitted.

[0137] 24 , in this embodiment, the retracted portion 21 is pressed against the surface of the additional copper plate 9 via the friction reducing material 27 during ultrasonic vibration for ultrasonically bonding the additional copper plate 9 to the circuit pattern 3. The rest is the same as in the first embodiment.

[0138] In this embodiment, the retracted portion 21 is positioned to protrude further than the bottom of the tool recessed portion 15a of the tool uneven portion 15. The friction reducing material 27 can be formed of a lubricant such as grease, or a sheet that undergoes shear deformation between the retracted portion 21 and the mounting surface portion 13. This sheet can be made of ceramic fiber paper or the like, which is made by molding ceramic fibers into a sheet.

[0139] This friction reducing material 27 is interposed between the retracted portion 21 of the jig T and the surface of the additional copper plate 9 when the tool T is pressed against the surface of the additional copper plate 9 laminated on the circuit pattern 3 and ultrasonic vibration is applied.

[0140] At the beginning of the ultrasonic vibration, the additional copper plate 9 is ultrasonically vibrated together with the tool T against the circuit conductor 3a. At this time, the surrounding tool concave-convex portions 15 pressurize the additional copper plate 9 while forming the engaging concave-convex portions 25, and the retracted portion 21 presses the additional copper plate 9 via the friction reducing material 27. As a result, the tool T applies ultrasonic vibration while applying pressure to the entire area of ​​the additional copper plate 9, thereby ensuring reliable joining of the additional copper plate 9 to the circuit conductor 3a.

[0141] When the additional copper plate 9 and the circuit conductor 3a are joined, the tool T ultrasonically vibrates against the additional copper plate 9, and the friction between the retracted portion 21 of the tool T and the additional copper plate 6 at this time can be reduced by the friction-reducing material 27. As a result, the temperature rise of the additional copper plate 6 can be suppressed, and damage to the insulating layer 7 can be reduced.

[0142] In addition, the sixth embodiment can also achieve the same effects as the first embodiment. [Explanation of symbols]

[0143] 1 circuit board 3 Circuit Pattern 3a Circuit conductor 5 Metal substrate (substrate) 7. Insulation layer 9 Additional copper plate (additional metal layer) 11 Semiconductor chips 13 Mounting surface 15 Tool unevenness 15a Tool recess 15b Tool protrusion 17 Engagement uneven part 17a Engagement recess 17aa bottom 17b Engagement protrusion 17c dent 17ca ridge 17d flat surface 19 Plane part 21 Evacuation area 25 Reduced unevenness 27 Friction reducing materials T-tool

Claims

1. A circuit board having a circuit pattern on a substrate and an additional metal layer laminated and bonded on the circuit pattern, The additional metal layer is A surface with relatively small irregularities, an engaging uneven portion having a relatively large unevenness, which is provided adjacent to the surface having a relatively small unevenness and which engages with a tool uneven portion of a vibration transmitting tool for bonding the additional metal layer onto the circuit pattern by ultrasonic vibration; Equipped with Circuit board.

2. 2. The circuit board according to claim 1, The relatively less uneven surface is flat. Circuit board.

3. 2. The circuit board according to claim 1, The surface with relatively small irregularities is an irregular surface having smaller irregularities than the engagement irregularity portion. Circuit board.

4. The circuit board according to any one of claims 1 to 3, The engagement uneven portion is provided on the entire circumference or a part of the entire circumference surrounding the periphery of the surface with relatively small unevenness, Circuit board.

5. The circuit board according to any one of claims 1 to 4, The engagement concave-convex portion is provided with engagement concave portions and engagement convex portions intermittently or continuously, Circuit board.

6. 6. The circuit board according to claim 5, The engaging recesses and engaging protrusions are provided intermittently, The intermittently provided engaging recesses and engaging protrusions are arranged such that adjacent engaging recesses and engaging protrusions are aligned or misaligned with each other. Circuit board.

7. The circuit board according to any one of claims 1 to 6, The engagement uneven portion includes an engagement protrusion that protrudes from the surface with the relatively smaller unevenness. Circuit board.

8. 8. The circuit board according to claim 7, the engaging protrusions are raised above the surface with the relatively smaller irregularities due to plastic deformation of the additional metal layer.

9. The circuit board according to any one of claims 1 to 8, The engagement concave-convex portion is an indentation of the tool concave-convex portion. Circuit board.

10. The circuit board according to any one of claims 1 to 9, The engagement irregularities have inclined sides. Circuit board.

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