Printed circuit board and its manufacturing method

Abstract

A printed circuit board that ensures reliability and smoothness and has sufficient thermal conductivity and heat dissipation effect, and a method for manufacturing the same, are provided. [Solution] The printed circuit board (10) of the embodiment comprises a first printed circuit board (11), a second printed circuit board (12), an intermediate member (13) provided between the first printed circuit board (11) and the second printed circuit board (12) and securing the first printed circuit board (11) and the second printed circuit board (12), a first through hole (14) passing through the first printed circuit board (11), the intermediate member (13), and the second printed circuit board (12), a heat conductive member (15) provided within the first through hole (14) and secured to the first through hole (14) by a part of the intermediate member (13), a first conductive layer (16) provided on the heat conductive member (15) exposed on the first printed circuit board (11) side and on the first printed circuit board (11), and a second conductive layer (17) provided on the heat conductive member (15) exposed on the second printed circuit board (12) side and on the second printed circuit board (12).

Description

[Technical Field]

[0001] FIELD OF THE INVENTION An embodiment of the present invention relates to a printed circuit board and a method for manufacturing the same. [Background technology]

[0002] Some printed circuit boards have copper pieces embedded in them, with the end faces of the copper pieces exposed on the surface of the board, thereby improving the thermal conductivity and heat dissipation effect of the board. One method of embedding copper pieces in a printed circuit board is to form through holes in the board and press-fit the copper pieces into the through holes.

[0003] However, discontinuities such as unevenness and gaps occur between the copper piece and the printed circuit board, reducing the smoothness of the printed circuit board and preventing sufficient thermal conductivity and heat dissipation. There are also problems with stress during press-fitting damaging the base material and reducing the reliability of the printed circuit board. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-231537 Summary of the Invention [Problem to be solved by the invention]

[0005] A printed circuit board that ensures reliability and smoothness and has sufficient thermal conductivity and heat dissipation effect, and a method for manufacturing the same, are provided. [Means for solving the problem]

[0006] According to one embodiment, the printed circuit board includes a first printed circuit board, a second printed circuit board, an intermediate member provided between the first printed circuit board and the second printed circuit board and fastening the first printed circuit board to the second printed circuit board, a first through hole penetrating the first printed circuit board, the intermediate member, and the second printed circuit board, a thermally conductive member provided in the first through hole and fastened to the first through hole by a part of the intermediate member, a first conductive layer provided on the thermally conductive member exposed on the first printed circuit board side and the first printed circuit board, and a second conductive layer provided on the thermally conductive member exposed on the second printed circuit board side and the second printed circuit board, The first conductive layer and the second conductive layer are smooth near and around the boundary between the first through hole and the thermally conductive member.

[0007] According to one embodiment, a method for manufacturing a printed circuit board includes the steps of: preparing a first printed circuit board and a second printed circuit board; stacking the first printed circuit board, an intermediate member, and the second printed circuit board, and forming a first through hole that penetrates the first printed circuit board, the intermediate member, and the second printed circuit board; inserting a thermally conductive member into the first through hole, and heating and pressurizing the first printed circuit board, the intermediate member, and the second printed circuit board with a release film interposed therebetween; polishing the thermally conductive member exposed in the first through hole; forming a first conductive film on the thermally conductive member and the first printed circuit board exposed on the first printed circuit board side, and forming a second conductive film on the thermally conductive member and the second printed circuit board exposed on the second printed circuit board side; and polishing the first conductive film and the second conductive film. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing a printed circuit board according to a first embodiment; [Figure 2] Cross-sectional photograph showing the printed circuit board according to the first embodiment [Figure 3] An enlarged cross-sectional photograph showing a main part of the printed circuit board according to the first embodiment. [Figure 4]Photographs showing the main part of the printed circuit board according to the first embodiment in comparison with a comparative example. [Figure 5] 1 is a cross-sectional view showing a heat-generating component mounted on a printed circuit board according to Embodiment 1. [Figure 6] 1 is a flowchart showing a method for manufacturing a printed circuit board according to a first embodiment. [Figure 7] 1A to 1C are cross-sectional views sequentially illustrating a manufacturing process of a printed circuit board according to the first embodiment; [Figure 8] 1A to 1C are cross-sectional views sequentially illustrating a manufacturing process of a printed circuit board according to the first embodiment; [Figure 9] 1A to 1C are cross-sectional views sequentially illustrating a manufacturing process of a printed circuit board according to the first embodiment; [Figure 10] 1A to 1C are cross-sectional views sequentially illustrating a manufacturing process of a printed circuit board according to the first embodiment; [Figure 11] 10 is a flowchart showing another method for manufacturing a main part of a printed circuit board according to the first embodiment. [Figure 12] 5A and 5B are cross-sectional views showing another manufacturing process of the main part of the printed circuit board according to the first embodiment; [Figure 13] 10 is a cross-sectional view showing a printed circuit board according to a second embodiment. [Figure 14] 10A to 10C are cross-sectional views sequentially illustrating a manufacturing process of a printed circuit board according to a second embodiment. [Figure 15] 10A to 10C are cross-sectional views sequentially illustrating a manufacturing process of a printed circuit board according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0010] (Embodiment 1) The printed circuit board according to this embodiment will be described with reference to Figures 1 to 4. Figure 1 is a cross-sectional view of the printed circuit board, Figure 2 is a cross-sectional photograph of the printed circuit board, Figure 3 is an enlarged cross-sectional photograph of a main part of the printed circuit board, and Figure 4 is a photograph showing the main part of the printed circuit board in comparison with a comparative example.

[0011] It should be noted that the present embodiment is merely an example, and the present invention is not limited to this. The drawings are schematic, and the ratios of dimensions and the like differ from those of the actual ones.

[0012] As shown in FIG. 1, the printed circuit board 10 includes a first printed circuit board 11, a second printed circuit board 12, an intermediate member 13, a first through hole 14, a heat conduction member 15, a first conductive layer 16, and a second conductive layer 17.

[0013] The intermediate member 13 is provided between the first printed circuit board 11 and the second printed circuit board 12, and fixes the first printed circuit board 11 to the second printed circuit board 12. The first through hole 14 penetrates through the stacked first printed circuit board 11, intermediate member 13, and second printed circuit board 12.

[0014] The heat conducting member 15 is provided in the first through hole 14. A part of the intermediate member 13 surrounds the side surface of the heat conducting member 15. The heat conducting member 15 is fixed to the first printed circuit board 11 and the second printed circuit board 12 by a part of the intermediate member 13.

[0015] First conductive layer 16 is provided on first printed circuit board 11 and heat conduction member 15 exposed on the side of first printed circuit board 11. The joint between heat conduction member 15 and first conductive layer 16 is integrated without any gap or resin or the like that is part of intermediate member 13 between them.

[0016] Second conductive layer 17 is provided on second printed circuit board 12 and heat conduction member 15 exposed on the side of second printed circuit board 12. The joint between heat conduction member 15 and second conductive layer 17 is integrated without any gap or resin or the like that is part of intermediate member 13 between them.

[0017] The surface of first conductive layer 16 is smooth near and around the boundary between first through hole 14 and heat conductive member 15. The surface of second conductive layer 16 is smooth near and around the boundary between first through hole 14 and heat conductive member 15.

[0018] "Smooth" means that the surface is flat and smooth, and has a glossy finish, e.g., a "smooth and shiny" state. The surfaces of the first conductive layer 16 and the second conductive layer 17 are polished surfaces with a mirror finish. The surface roughness of the first conductive layer 16 and the second conductive layer is 10 μm or less.

[0019] In this specification, the vicinity and periphery of the boundary between first through-hole 14 and heat conductive member 15 refers to an area that includes heat conductive member 15 and is about three times the size of heat conductive member 15. The definition of surface roughness is not particularly limited, and may be, for example, "arithmetic mean roughness (Ra)" or "maximum height (Rz)," which are parameters in the height direction.

[0020] Because the arithmetic mean roughness Ra uses an average value, it is less susceptible to the influence of a single protruding scratch and provides stable results when evaluating surface roughness. The maximum height Rz is calculated by extracting a portion of the roughness curve measured with a roughness meter over a reference length and adding the highest part (maximum peak height: Rp) and the deepest part (maximum valley depth: Rv). It is considered to be an indicator of stable quality, along with the arithmetic mean roughness Ra, by checking for the presence or absence of protruding irregularities and scratches.

[0021] The first printed circuit board 11 and the second printed circuit board 12 will be described.

[0022] The first printed circuit board 11 is formed by alternately stacking and fixing core materials 18 and intermediate materials 19. The number of layers of core materials 18 and intermediate materials 19 is arbitrary. In this example, two core materials 18 and three intermediate materials 19 are alternately stacked and fixed.

[0023] A plurality of wiring patterns L are provided on the core material 18 and the intermediate material 19. For example, from the first conductive layer 16 side, a wiring pattern L is provided on the first intermediate material 19, a wiring pattern L is provided on both sides of the first core material 18, a wiring pattern L is provided on both sides of the second core material 18, and a wiring pattern L is provided on the third intermediate material 19. Here, the layout of the wiring patterns L provided on each core material 18 and each intermediate material 19 is arbitrary and is not particularly limited.

[0024] A plurality of second through holes 20 penetrate the laminated core material 18 and intermediate material 19. A plurality of connection wirings (through-hole wirings) 21 are provided along the inner walls of the plurality of second through holes 20. The plurality of second through holes 20 are filled with a portion of the intermediate member 13. The plurality of second through holes 20 may be filled with a hole filling resin other than the portion of the intermediate member 13.

[0025] The plurality of wiring patterns L are electrically connected by a plurality of connection wires 21. Which of the plurality of wiring patterns L are electrically connected to each other by which connection wires 21 is arbitrary and is not particularly limited.

[0026] The configuration of the second printed circuit board 12 is similar to that of the first printed circuit board 11, and therefore a description thereof will be omitted.

[0027] When the first printed circuit board 11 and the second printed circuit board 12 are stacked, some of the multiple second through holes 20 provided in the first printed circuit board 11 overlap with some of the multiple second through holes 20 provided in the second printed circuit board 12 in a plan view. That is, the first printed circuit board 11 and the second printed circuit board 12 have overlapping second through holes 20 and non-overlapping second through holes 20. The overlapping second through holes 20 form penetrating through holes of the printed circuit board 10. The non-overlapping second through holes 20 form non-penetrating through holes of the printed circuit board 10.

[0028] The core material 18 and the intermediate material 19 are, for example, glass epoxy substrates having a thickness of about 100 to 200 μm. The wiring pattern L is, for example, copper wiring obtained by patterning a copper foil having a thickness of about 10 to 20 μm by etching. The connection wiring 21 is, for example, copper-plated wiring. The heat conduction member 15 is, for example, a coin-shaped copper plate having a thickness of about 1 to 2 mm and a diameter of about 2 to 5 mm. The first and second conductive layers 16, 17 are, for example, copper-plated layers having a thickness of about 30 to 100 μm.

[0029] The intermediate member 13 is originally a member (prepreg) made by impregnating glass fiber cloth with epoxy resin. As will be described later, when the prepreg is heated and pressurized, the epoxy resin that is part of the intermediate member 13 melts.

[0030] The molten epoxy resin is thermally cured, bonding first printed circuit board 11 and second printed circuit board 12. A portion of the molten epoxy resin bonds heat conductive member 15 to first through hole 14, filling second through hole 20. As described above, second through hole 20 may be filled with a resin other than the epoxy resin that is part of intermediate member 13.

[0031] Printed circuit boards that can electrically connect internal wiring patterns using non-penetrating vias that do not penetrate a part of the board are also called IVH (Internal via hole) boards.Printed circuit boards that have copper plates packed inside them as thermal conductive materials are also called copper inlay boards.

[0032] Fig. 2 is a cross-sectional photograph showing a printed circuit board 10. As shown in Fig. 2, the cross-sectional photograph of printed circuit board 10 reveals that the surfaces of first conductive layer 16 and second conductive layer 17 are smooth near and around the boundary between first through hole 14 and heat conductive member 15.

[0033] Fig. 3 is an enlarged cross-sectional photograph showing a main portion of the printed circuit board 10. As shown in Fig. 3, the enlarged cross-sectional photograph of the main portion of the printed circuit board 10 shows that the maximum height (Rz) of the surface smoothness of the first conductive layer 16 is 2.95 μm and 3.40 μm, and the maximum height (Rz) of the surface smoothness of the second conductive layer 17 is 5.58 μm and 5.58 μm, near and around the boundary between the first through hole 14 and the heat conductive member 15. The surface smoothness of the first conductive layer 16 and the second conductive layer 17 was approximately 4.3 μm on average, which was less than 10 μm.

[0034] Next, the smoothness of the printed circuit board of this embodiment will be explained in comparison with a comparative example. Figure 4 is a diagram comparing the printed circuit board of this embodiment with a comparative example. Figures 4(a) and 4(b) are planar photographs of the front and back surfaces of the printed circuit board, Figure 4(c) is a cross-sectional photograph of the printed circuit board, and Figures 4(d) and 4(e) are enlarged cross-sectional photographs of the front and back surfaces. Figure 4(f) shows the smoothness of the center and edges near and around the boundary between the through hole and the heat conductive member.

[0035] Here, the printed circuit board of the comparative example means a printed circuit board in which a through hole is formed and a coin-shaped copper plate is press-fitted into the through hole. The difference between Comparative Example 1 and Comparative Example 2 is the difference in the manufacturing lot.

[0036] As shown in Figures 4(a) to 4(f), the printed circuit board of this embodiment has a smooth front surface (surface of first conductive layer 16) and a smooth back surface (surface of second conductive layer 17). No steps or irregularities are observed near or around the boundary between first through-hole 14 and heat conductive member 15. The smoothness (height difference Rz) is 0 to 10 µm, and is 10 µm or less, at both the center and the end portions.

[0037] On the other hand, in Comparative Example 1, ring-shaped discontinuities, scratches, dents, etc. were observed near and around the boundaries between the through holes and the heat conductive members on both the front and back surfaces of the printed circuit board. The ring-shaped discontinuities on the front surface side were caused by the ends of the heat conductive members protruding from the through holes. The ring-shaped discontinuities on the back surface side were caused by the ends of the heat conductive members being inside the through holes. The smoothness (height difference Rz) was -210 to 44 μm, greater than 10 μm.

[0038] In Comparative Example 2, as in Comparative Example 1, ring-shaped discontinuities were observed near the boundaries between the through holes and the heat conductive members on both the front and back surfaces of the printed circuit board. The ring-shaped discontinuities on the front surface side were steps caused by the end of the heat conductive member protruding from the through holes, and gaps caused by the side surfaces of the end of the heat conductive member being spaced apart from the inner walls of the through holes. The ring-shaped discontinuities on the back surface side were steps caused by the end of the heat conductive member being inside the through holes. The smoothness (height difference Rz) was -284 to 27 μm, greater than 10 μm.

[0039] The decrease in smoothness in the printed circuit boards of Comparative Examples 1 and 2 is due to the heat conductive member being press-fitted into the through-hole. Specifically, in Comparative Examples 1 and 2, to prevent the heat conductive member from slipping through the through-hole and falling out, the outer diameter of the heat conductive member is set to be approximately the same as the inner diameter of the through-hole. When the heat conductive member is press-fitted into the through-hole, it is inserted in such a way that it rubs against the inner wall of the through-hole and pushes the through-hole open. This deforms the copper heat conductive member, causing uneven insertion speeds between the center and end of the heat conductive member, presumably resulting in the ring-shaped discontinuity described above.

[0040] On the other hand, in the printed circuit board of this embodiment, after inserting heat conductive member 15 into first through hole 14 as described below, heat conductive member 15 is fixed to first through hole 14 using a part of intermediate member 13, the surface of heat conductive member 15 is polished, and the surfaces of first and second conductive layers 16, 17 are polished. This prevents undue stress from being applied to first and second printed circuit boards 11, 12 when inserting heat conductive member 15, and makes it possible to correct variations in the fixing position of heat conductive member 15.

[0041] Therefore, the printed circuit board 10 can be obtained that ensures reliability and smoothness, and has sufficient thermal conductivity and heat dissipation effect.

[0042] 5 is a diagram showing a heat-generating component, such as a semiconductor integrated circuit (IC), mounted on a printed circuit board according to this embodiment. As shown in FIG. 5, a heat-generating component 25 is mounted on a first conductive layer 16 of the printed circuit board 10. A heat sink 26 is attached to a second conductive layer 17 of the printed circuit board 10.

[0043] Lands 16a are formed on the first conductive layer 16 so as to cover the heat conduction member 15, and pads 16b are formed so as to cover the connection wiring 21. The lands 16a and the pads 16b are spaced apart and electrically insulated. The lands 16a and the pads 16b are formed by patterning the first conductive layer 16.

[0044] A heat-generating component 25 is placed on the land 16a. A lead 25a of the heat-generating component 25 is electrically connected to the pad 16b. The lead 25a is, for example, soldered to the pad 16b. The pad 16b is electrically connected to the wiring pattern L via a connection wiring 21.

[0045] Because first conductive layer 16 is smooth, heat-generating component 25 and first conductive layer 16 are in close contact. Similarly, because second conductive layer 17 is smooth, heat sink 26 and second conductive layer 17 are in close contact. As shown by the dashed lines, heat generated by heat-generating component 25 is quickly conducted to heat conduction member 15 via first conductive layer 16. Heat that passes through heat conduction member 15 is quickly conducted to heat sink 26 via second conductive layer 17. Heat that flows into heat sink 26 is dissipated into the atmosphere from the fins of heat sink 26.

[0046] Therefore, the amount of heat that diffuses in the lateral direction parallel to first printed circuit board 11 and second printed circuit board 12 and the amount of heat that dissipates from the top and side surfaces of heat-generating component 25 are extremely small.

[0047] The heat conducting member 15 is provided directly below the heat generating component 25 mounted on the printed circuit board 10, and the heat generating component 25 and the heat conducting member 15 are in close contact with each other, so that the heat dissipation characteristics of a part of the printed circuit board 10 are substantially improved.

[0048] Next, a method for manufacturing a printed circuit board according to this embodiment will be described. Figure 6 is a flowchart showing the steps for manufacturing a printed circuit board, and Figures 7 to 10 are cross-sectional views showing the steps in sequence.

[0049] 7(a), a first printed circuit board 11 and a second printed circuit board 12 are prepared (step S1). As described above, the first printed circuit board 11 and the second printed circuit board 12 are formed by alternately laminating core materials 18 and intermediate materials 19, and a plurality of wiring patterns L are formed in the core materials 18 and the intermediate materials 19.

[0050] As shown in FIG. 7(b), a plurality of second through holes 20 are formed in the first printed circuit board 11 and the second printed circuit board 12, and the inner walls of the second through holes are copper-plated to form connection wiring (through-hole wiring) 21 for electrically connecting a plurality of wiring patterns L (step S2).

[0051] 7(c), through holes are formed in the first printed circuit board 11, the intermediate member (prepreg) 13, and the second printed circuit board 12 so as to obtain first through holes 14 that penetrate the first printed circuit board 11, the intermediate member 13, and the second printed circuit board 12 (step S3). In the drawing, for ease of viewing, they are depicted as if they are spaced apart from each other.

[0052] The through holes may be formed at once by stacking first printed circuit board 11, intermediate member 13, and second printed circuit board 12, or may be formed individually.

[0053] 8(a), first printed circuit board 11, intermediate member 13, and second printed circuit board 12 are stacked on top of each other with release film 41 underneath, and heat conductive member 15 is inserted into first through hole 14 and covered with release film 42 (step S4). In the drawing, for ease of viewing, they are depicted as if they are spaced apart.

[0054] The outer diameter of the heat conducting member 15 is preferably made slightly smaller than the diameter of the first through hole 14. For example, it is made smaller by about 100 μm. This allows the heat conducting member 15 to be smoothly inserted into the first through hole 14, and also ensures a gap that allows part of the intermediate member 13 to smoothly enter between the first through hole 14 and the heat conducting member 15 in the next step.

[0055] As shown in FIG. 8(b), the first printed circuit board 11, the intermediate member 13 and the second printed circuit board 12, which are sandwiched between release films 41 and 42 and laminated together, are heated and pressurized (hot pressed) (step S5).

[0056] The hot pressing is performed, for example, at a temperature of about 100 to 200°C and a pressure of about 0.5 to 5 MPa. If the release films 41, 42 are made of a material that softens at about 80°C, they will soften before the epoxy resin of the intermediate member 13 during hot pressing, and will follow the first printed circuit board 11 and the second printed circuit board 12. As a result, filling of the epoxy resin into the gap between the first through hole 14 and the heat conductive member 15 is assisted, and the epoxy resin is prevented from spilling out of the gap.

[0057] The hot press melts the epoxy resin in intermediate member 13, and the molten epoxy resin fills the gap between first through hole 14 and heat conductive member 15, and also fills second through hole 20. When the epoxy resin solidifies, first printed circuit board 11 and second printed circuit board 12 are fixed together by intermediate member 13, and heat conductive member 15 is fixed to first through hole 14 by a part of intermediate member 13.

[0058] Since the hot pressing reduces the total thickness of first printed circuit board 11, intermediate member 13, and second printed circuit board 12, the total thickness after hot pressing is set in advance to be the same as the thickness of heat conductive member 15. Furthermore, it is preferable that heat conductive member 15 and the epoxy resin that is part of intermediate member 13 protrude somewhat beyond first printed circuit board 11 and second printed circuit board 12 after hot pressing. For example, they should protrude by about 50 μm.

[0059] As shown in FIG. 9(a), the end face of the heat conductive member 15 on the side of the first printed circuit board 11 and the end face on the side of the second printed circuit board 12 are mechanically polished (step S6). When the total thickness of the first printed circuit board 11, the intermediate member 13, and the second printed circuit board 12 is reduced by hot pressing, the end of the heat conductive member 15 may protrude slightly and the outer periphery may sag, resulting in a gentle convex shape, for example, as shown by the dashed line. The height of the convex portion may be, for example, approximately 10 to 100 μm. By removing as much of the convex portion as possible, the final smoothness is improved.

[0060] The mechanical polishing method is not particularly limited, but for example, surface grinding is performed using a disk-type grindstone 43. Alternatively, polishing using a slurry containing abrasive grains such as silica or alumina may also be performed.

[0061] 9(b), copper plating is performed on the heat conductive member 15 exposed on the first printed circuit board 11 side and the first printed circuit board 11, and on the heat conductive member 15 exposed on the second printed circuit board 12 side and the second printed circuit board 12, to form the first conductive layer 16 and the second conductive layer 17 (step S7). The copper plating method is not particularly limited, but an electrolytic plating method capable of forming a thick film is preferable, for example.

[0062] As shown in FIG. 10, the first conductive layer 16 and the second conductive layer 17 are mechanically polished (step S7). Mechanical polishing is performed until the surface roughness of the first conductive layer 16 and the surface roughness of the second conductive layer 17 become 10 μm or less. The mechanical polishing method is not particularly limited, but may be performed, for example, by a method similar to that of step S7. A roller type grindstone 44 is preferable so that a wide area can be polished. Slurry polishing may also be used. Furthermore, chemical mechanical polishing (CMP) may be added. CMP can provide a more precisely smooth surface.

[0063] As described above, in the printed circuit board 10 of this embodiment, the heat conductive member 15 is fixed to the first through hole 14 that penetrates the stacked first printed circuit board 11, intermediate member 13, and second printed circuit board 12, the first conductive layer 16 is provided on the heat conductive member 15 exposed on the first printed circuit board 11 side and on the first printed circuit board 11, and the second conductive layer 17 is provided on the heat conductive member 15 exposed on the second printed circuit board 12 side and on the second printed circuit board 12.

[0064] First, the heat conduction member 15 exposed on the first and second printed circuit boards 11 and 12 is polished, and then the first conductive layer 16 and the second conductive layer 17 are polished, which is called two-step polishing.This results in a smooth surface finish of the first conductive layer 16 and the second conductive layer 17 near and around the boundary between the first through hole 14 and the heat conduction member 15.

[0065] As a result, the adhesion between the first conductive layer 16 and the heat generating component 25 and the adhesion between the second conductive layer 17 and the heat sink 26 are high.

[0066] Furthermore, since the outer diameter of the heat conductive member 15 is slightly smaller than the diameter of the first through hole 14, no stress is applied when inserting the heat conductive member 15 into the first through hole 14. This prevents warping, deformation, etc. of the printed circuit board.

[0067] Therefore, a printed circuit board having sufficient thermal conductivity and heat dissipation effect while ensuring reliability and flatness, and a method for manufacturing the same can be obtained.

[0068] Here, the case where the printed circuit board has a two-layered IVH structure has been described, but it may also have a multi-layered IVH structure.

[0069] Although the heat conducting component 15 is described as being a coin-shaped copper plate, stripe-shaped grooves (so-called coin-like serrations) may be provided on the side of the copper plate along the thickness direction.

[0070] If the convex portion on the side surface of the copper plate is inscribed in the first through hole 14, it is easy to center the first through hole 14 and the copper plate, and the gap between the first through hole 14 and the copper plate is kept uniform. In step S5, the molten epoxy resin is easily filled into the gap between the first through hole 14 and the heat conductive member 15.

[0071] Furthermore, since the surfaces of the first conductive layer 16 and the second conductive layer 17 are smooth, the contact resistance between the outer layer conductor and the heat conducting member 15 is reduced, allowing a stable current flow. The heat conducting member 15 can also be used as a current conductor.

[0072] 11 and 12, a description will be given of a case where the above-mentioned second through hole 20 is filled with a hole filling resin other than the part of the intermediate member 13. Fig. 11 is a flowchart showing a method of filling the second through hole 20 with a hole filling resin other than the part of the intermediate member 13, and Fig. 12 is a cross-sectional view showing a process of filling the second through hole 20 with a hole filling resin other than the part of the intermediate member 13.

[0073] 11, after step S2 shown in FIG. 6, the second through-hole 20 is filled with a hole-filling resin separate from the part of the intermediate member 13 (step S21). After step S21 is completed, the process proceeds to step S3 shown in FIG.

[0074] 12(a), a thermosetting resin 31 in a fluid raw material state is injected into the second through-hole 20 of the first printed circuit board 11, and then the resin 31 is heated and cured. The resin 31 is suitably made of the same material as a part of the intermediate member 13, but a different material may also be used. For example, the resin 31 is the same type of epoxy resin as the epoxy resin that is a part of the intermediate member 13.

[0075] Once the thermosetting resin is hardened, it will not soften or flow even if it is reheated, and therefore it will not affect step S5 shown in Fig. 6. As shown in Fig. 12(b), the same process is carried out for the second printed circuit board 12 as for the first printed circuit board 11.

[0076] By filling the second through-hole 20 with a material other than the part of the intermediate member 13 in advance, the amount of the intermediate member 13 used can be reduced.

[0077] (Embodiment 2) The printed circuit board according to this embodiment will be described with reference to Fig. 13. Fig. 13 is a cross-sectional view showing the printed circuit board according to this embodiment. Explanation of the parts of this embodiment that are the same as those of embodiment 1 will be omitted, and only differences will be described. This embodiment differs from embodiment 1 in that the first printed circuit board and the second printed circuit board have different configurations.

[0078] 13 , in this embodiment, the first printed circuit board 51 and the second printed circuit board 52 are core materials 18 provided with wiring patterns L. The intermediate member 13 is provided between the first printed circuit board 51 and the second printed circuit board 52 and fixes the first printed circuit board 51 and the second printed circuit board 52 together. Here, the stacked first printed circuit board 51, the intermediate member 13, and the second printed circuit board 52 are referred to as a printed circuit board 54.

[0079] The printed circuit board 50 of this embodiment includes two printed circuit boards 54 and an intermediate member 13 that is provided between the two printed circuit boards 54 and fastens the printed circuit boards 54. That is, the printed circuit board 50 is formed by stacking two printed circuit boards 54, and other configurations are the same as those of the printed circuit board 10. Furthermore, the number of printed circuit boards 54 to be stacked is optional and is not particularly limited.

[0080] Next, a method for manufacturing a printed circuit board according to this embodiment will be described. Figures 14 and 15 are cross-sectional views showing the steps of manufacturing a printed circuit board in order.

[0081] As shown in FIG. 14(a), a first printed circuit board 51 and a second printed circuit board 52 are prepared. Through holes are formed in the first printed circuit board 51, the intermediate member 13, and the second printed circuit board 52 so as to obtain first through holes 14 that penetrate the first printed circuit board 51, the intermediate member 13, and the second printed circuit board 52. In the drawing, for ease of viewing, they are depicted as if they are spaced apart from each other. The through holes may be formed individually or may be formed in a stacked manner at once.

[0082] As shown in Figure 14(b), two printed circuit boards 54 and an intermediate member 13 are stacked on top of each other with a release film 41 underneath, a heat conduction member 15 is inserted into the first through hole 14, and the member is covered with a release film 42. In this figure, for ease of viewing, each member is shown as being spaced apart.

[0083] As shown in FIG. 14(c), the laminated printed circuit board 54, intermediate member 13, and printed circuit board 54 sandwiched between release films 41 and 42 are heated and pressed (hot pressed).

[0084] As shown in FIG. 15(a), the end faces of the heat conducting member 15 on the first printed circuit board 51 side and the second printed circuit board 52 side are mechanically polished.

[0085] As shown in Figure 15(b), copper plating is applied to the heat conduction member 15 exposed on the first printed circuit board 51 side and the first printed circuit board 11, and to the heat conduction member 15 exposed on the second printed circuit board 52 side and the second printed circuit board 52, to form a first conductive layer 16 and a second conductive layer 17.

[0086] 15(c), the first conductive layer 16 and the second conductive layer 17 are mechanically polished. The mechanical polishing is carried out until the surface roughness of the first conductive layer 16 and the surface roughness of the second conductive layer 17 become 10 μm or less.

[0087] As described above, according to this embodiment, similar to the first embodiment, reliability and flatness are ensured, and a printed circuit board having sufficient thermal conductivity and heat dissipation effect, and a method for manufacturing the same, can be obtained.

[0088] Although several embodiments have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0089] 10, 50 printed circuit board 11, 51 First printed circuit board 12, 52 Second printed circuit board 13 Intermediate parts 14, 20 First and second through holes 15 Thermal Conduction Materials 16, 17 First and second conductive layers 18 Core material 19 Intermediate materials 21 Connection wiring 25 Heat-generating parts 26 Heat sink 31 Resin 41, 42 Release film 43, 44 Grindstone L wiring pattern

Claims

1. a first printed circuit board; a second printed circuit board; an intermediate member provided between the first printed circuit board and the second printed circuit board and configured to fix the first printed circuit board and the second printed circuit board together; a first through hole that penetrates the first printed circuit board, the intermediate member, and the second printed circuit board; a heat conduction member provided in the first through hole and fixed to the first through hole by a part of the intermediate member; a first conductive layer provided on the heat conductive member exposed on the first printed circuit board and on the first printed circuit board; a second conductive layer provided on the heat conductive member exposed on the second printed circuit board and on the second printed circuit board; Equipped with The printed circuit board is characterized in that the first conductive layer and the second conductive layer are smooth near and around the boundary between the first through hole and the heat conduction member.

2. 2. The printed circuit board according to claim 1, wherein the surfaces of the first conductive layer and the second conductive layer are mechanically polished surfaces.

3. 2. The printed circuit board according to claim 1, wherein the surface roughness of the first conductive layer and the surface roughness of the second conductive layer are 10 [mu]m or less.

4. the first and second printed circuit boards are formed by alternately stacking and fixing core materials and intermediate materials, a plurality of wiring patterns are provided on the core materials and the intermediate materials, a plurality of second through holes are provided penetrating the core materials and the intermediate materials, and a plurality of connection wires are provided in the plurality of second through holes for electrically connecting the plurality of wiring patterns; The printed circuit board according to claim 1, characterized in that when the first printed circuit board and the second printed circuit board are stacked, in a planar view, some of the plurality of second through holes provided in the first printed circuit board overlap with some of the plurality of second through holes provided in the second printed circuit board.

5. 2. The printed circuit board according to claim 1, wherein the first and second printed circuit boards are core materials on which wiring patterns are provided.

6. 5. The printed circuit board according to claim 4, wherein the connection wiring is provided along an inner wall of the second through hole, and the second through hole is filled with a part of the intermediate member.

7. 5. The printed circuit board according to claim 4, wherein the connection wiring is provided along an inner wall of the second through hole, and the second through hole is filled with a material other than a part of the intermediate member.

8. 6. The printed circuit board according to claim 4, wherein the core material and the intermediate material are glass epoxy materials.

9. 2. The printed circuit board according to claim 1, wherein the intermediate member is a prepreg made of glass fiber cloth impregnated with epoxy resin.

10. 2. The printed circuit board according to claim 1, wherein the heat conducting member is a copper plate, and the first conductive layer and the second conductive layer are copper plated layers.

11. providing a first printed circuit board and a second printed circuit board; a step of stacking the first printed circuit board, an intermediate member, and the second printed circuit board, and forming a first through hole that penetrates the first printed circuit board, the intermediate member, and the second printed circuit board; a step of inserting a thermally conductive member into the first through hole, and applying heat and pressure to the first printed circuit board, the intermediate member, and the second printed circuit board via a release film; polishing the heat conducting member exposed in the first through hole; forming a first conductive film on the heat conduction member exposed on the first printed circuit board side and the first printed circuit board, and forming a second conductive film on the heat conduction member exposed on the second printed circuit board side and the second printed circuit board; polishing the first conductive film and the second conductive film; A method for manufacturing a printed circuit board, comprising:

12. 12. The method for manufacturing a printed circuit board according to claim 11, wherein the heating and pressurizing step is performed so that the thermally conductive member and a portion of the intermediate member protrude by a predetermined height from the first printed circuit board and the second printed circuit board.

13. 12. The method for manufacturing a printed circuit board according to claim 11, wherein the heat conducting member is polished by mechanical polishing, and the first conductive film and the second conductive film are polished by mechanical polishing.

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