Printed Circuit Board and Method for Manufacturing the Same

Abstract

Provided are a printed circuit board having sufficient thermal conductivity and heat dissipation effect while ensuring reliability and smoothness, and a method for manufacturing the same. 【Solution means】The printed circuit board 10 of the embodiment includes 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 for fixing the first printed circuit board 11 and the second printed circuit board 12, a first through hole 14 penetrating the first printed circuit board 11, the intermediate member 13, and the second printed circuit board 12, a heat conduction member 15 provided in the first through hole 14 and fixed to the first through hole 14 by a part of the intermediate member 13, a first conductive layer 16 provided on the heat conduction member 15 exposed on the first printed circuit board 11 side and the first printed circuit board 11, and a second conductive layer 17 provided on the heat conduction member 15 exposed on the second printed circuit board 12 side and the second printed circuit board 12.

Description

Technical Field

[0001] Embodiments of the present invention relate to a printed circuit board and a method for manufacturing the same.

Background Art

[0002] Some printed circuit boards have improved thermal conductivity and heat dissipation effects by embedding copper pieces in the printed circuit board and exposing the end faces of the copper pieces on the surface of the printed circuit board. As a method of embedding copper pieces in a printed circuit board, there is a method of forming through holes in the printed circuit board and press-fitting and fitting copper pieces into the through holes.

[0003] However, there are problems that discontinuities such as unevenness and gaps occur between the copper pieces and the printed circuit board, the smoothness of the printed circuit board is reduced, and sufficient thermal conductivity and heat dissipation effects cannot be obtained, and damage is caused to the base material due to the stress during press-fitting, resulting in a reduction in the reliability of the printed circuit board.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] To provide a printed circuit board having sufficient thermal conductivity and heat dissipation effects while ensuring reliability and smoothness, and a method for manufacturing the same.

Means for Solving the Problems

[0006] According to one embodiment, a 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 for fixing the first printed circuit board and 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 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 conduction member exposed on the first printed circuit board side and the first printed circuit board, and a second conductive layer provided on the heat conduction member exposed on the second printed circuit board side and the second printed circuit board. The first conductive layer is provided with lands covering the heat conductive member and pads that are electrically insulated and spaced apart from the lands, and the second conductive layer on the side opposite to the lands and the pads is a continuous plane. In the vicinity and periphery of the boundary between the first through hole and the heat conduction member, The surface roughness of the first conductive layer and the surface roughness of the second conductive layer are 10 μm or less. .

[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, laminating the first printed circuit board, an intermediate member, and the second printed circuit board to form a first through hole penetrating the first printed circuit board, the intermediate member, and the second printed circuit board, inserting a heat conduction member into the first through hole, heating and pressing the first printed circuit board, the intermediate member, and the second printed circuit board through a release film, polishing the heat conduction 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, forming a second conductive film on the heat conduction member exposed on the second printed circuit board side and the second printed circuit board, and polishing the first conductive film and the second conductive film.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments 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 FIGS. 1 to 4. FIG. 1 is a cross-sectional view showing the printed circuit board, FIG. 2 is a cross-sectional photograph showing the printed circuit board, FIG. 3 is an enlarged cross-sectional photograph showing the main part of the printed circuit board, and FIG. 4 is a photograph showing the main part of the printed circuit board in comparison with a comparative example.

[0011] Note that this embodiment is merely an example, and the present invention is not limited thereto. The drawings are schematic, and the ratios of the respective dimensions and the like are different from 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 and the second printed circuit board 12. The first through hole 14 penetrates through the stacked first printed circuit board 11, the intermediate member 13, and the second printed circuit board 12.

[0014] The heat conduction member 15 is provided in the first through hole 14. A part of the intermediate member 13 surrounds the side surface of the heat conduction member 15. The heat conduction 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] The first conductive layer 16 is provided on the heat conduction member 15 exposed on the first printed circuit board 11 side and the first printed circuit board 11. The joint portion between the heat conduction member 15 and the first conductive layer 16 is integrated without any gap and the interposition of resin or the like which is a part of the intermediate member 13 therebetween.

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

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

[0018] Smoothing means flat and smooth, with a shiny surface, for example in the state of "slippery and shiny". The surfaces of the first conductive layer 16 and the second conductive layer 17 are mirror-finished polished surfaces. The surface roughness of the first conductive layer 16 and the surface roughness of the second conductive layer are 10 μm or less.

[0019] In this specification, the vicinity and periphery of the boundary between the first through-hole 14 and the heat conduction member 15 mean a region that includes the heat conduction member 15 and is about three times the size of the heat conduction member 15. Also, the definition of surface roughness is not particularly limited, but for example, it may be the "arithmetic mean roughness (Ra)" which is a parameter in the height direction or the "maximum height (Rz)".

[0020] Since the arithmetic mean roughness Ra uses an average value, it is not easily affected by a single protruding scratch and can obtain stable results in evaluating the surface roughness. The maximum height Rz is obtained by extracting a part of the roughness curve measured with a roughness meter by a reference length and adding the value of the highest part (maximum peak height: Rp) and the deepest part (maximum valley depth: Rv). It is regarded as an index for quality stability together with the arithmetic mean roughness Ra, such as to confirm the presence or absence of protruding unevenness 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 has a core material 18 and an intermediate material 19 alternately laminated and fixed. The number of laminations of the core material 18 and the intermediate material 19 is arbitrary. Here, two core materials 18 and three intermediate materials 19 are alternately laminated and fixed.

[0023] A plurality of wiring patterns L are provided on the core material 18 and the intermediate material 19. For example, starting from the side of the first conductive layer 16, a wiring pattern L is provided on the first intermediate material 19, wiring patterns L are provided on both sides of the first core material 18, wiring patterns L are 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 through the stacked core material 18 and the intermediate material 19. Along the inner walls of the plurality of second through-holes 20, a plurality of connection wirings (through-hole wirings) 21 are provided. A part of the intermediate member 13 fills the inside of the plurality of second through-holes 20. The inside of the plurality of second through-holes 20 may be filled with a resin for filling holes different from a part of the intermediate member 13.

[0025] The plurality of wiring patterns L are electrically connected by the plurality of connection wirings 21. Among the plurality of wiring patterns L, which wiring patterns L are electrically connected by which connection wiring 21 is arbitrary and not particularly limited.

[0026] The configuration of the second printed circuit board 12 is the same as that of the first printed circuit board 11, and the description thereof is omitted.

[0027] When the first printed circuit board 11 and the second printed circuit board 12 are overlapped, a part of the plurality of second through-holes 20 provided in the first printed circuit board 11 overlaps with a part of the plurality of 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 second through-holes 20 that overlap and second through-holes 20 that do not overlap. The overlapping second through-holes 20 form through-holes of the printed circuit board 10. The non-overlapping second through-holes 20 form non-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, a 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, a copper-plated wiring. The heat conduction member 15 is, for example, a coin-shaped copper plate having a thickness of 1 to 2 mm and a diameter of about 2 to 5 mm. The first and second conductive layers 16 and 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) in which a glass fiber cloth is impregnated with an epoxy resin. As will be described later, when the prepreg is heated and pressed, the epoxy resin, which is a part of the intermediate member 13, melts.

[0030] The melted epoxy resin thermosets, and the first printed circuit board 11 and the second printed circuit board 12 are fixed together. The heat conduction member 15 is fixed to the first through hole 14 by a part of the melted epoxy resin, and the inside of the second through hole 20 is filled. As described above, the inside of the second through hole 20 may be filled with a resin different from the epoxy resin that is a part of the intermediate member 13.

[0031] A printed circuit board that can electrically connect internal wiring patterns with non-through vias that do not penetrate a part of such a board is also called an IVH (Internal via hole) board. A printed circuit board with a copper plate packed as a heat conduction member is also called a copper inlay board.

[0032] Figure 2 is a cross-sectional photograph showing a printed circuit board. As shown in Figure 2, according to the cross-sectional photograph of the printed circuit board 10, it can be seen that the surfaces of the first conductive layer 16 and the second conductive layer 17 are smooth in the vicinity and periphery of the boundary between the first through hole 14 and the heat conduction member 15.

[0033] Figure 3 is an enlarged cross-sectional photograph showing a main part of the printed circuit board. As shown in Figure 3, according to the enlarged cross-sectional photograph of the main part of the printed circuit board 10, in the vicinity and periphery of the boundary between the first through hole 14 and the heat conduction member 15, at the maximum height (Rz), the surface smoothness of the first conductive layer 16 is 2.95μm and 3.40μm, and the surface smoothness of the second conductive layer 17 is 5.58μm and 5.58μm. The average surface smoothness of the first conductive layer 16 and the second conductive layer 17 is about 4.3μm and is 10μm or less.

[0034] Next, the smoothness of the printed circuit board of the present embodiment will be described in comparison with a comparative example. FIG. 4 is a diagram showing a comparison between the printed circuit board of the present embodiment and that of the comparative example. FIGS. 4(a) and 4(b) are plan photographs of the front and back surfaces of the printed circuit board, FIG. 4(c) is a cross-sectional photograph of the printed circuit board, and FIGS. 4(d) and 4(e) are enlarged cross-sectional photographs of the front and back surfaces. FIG. 4(f) shows the smoothness of the central portion and the end portion in the vicinity and periphery of the boundary between the through hole and the heat conduction member.

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

[0036] As shown in FIGS. 4(a) to 4(f), the printed circuit board of the present embodiment is smooth on both the front surface (the surface of the first conductive layer 16) and the back surface (the surface of the second conductive layer 17). No steps, unevenness, etc. are seen in the vicinity and periphery of the boundary between the first through hole 14 and the heat conduction member 15. The smoothness (height difference Rz) is 0 to 10 μm, both at the central portion and the end portion, and is 10 μm or less.

[0037] On the other hand, in Comparative Example 1, ring-shaped discontinuities, scratches, depressions, etc. are seen on both the front and back surfaces of the printed circuit board in the vicinity and periphery of the boundary between the through hole and the heat conduction member. The ring-shaped discontinuity on the front surface side is a step caused by the end portion of the heat conduction member protruding from the through hole. The ring-shaped discontinuity on the back surface side is a step caused by the end portion of the heat conduction member being inside the through hole. The smoothness (height difference Rz) is -210 to 44 μm, and is greater than 10 μm.

[0038] Also in Comparative Example 2, as in Comparative Example 1, ring-shaped discontinuities are observed near the boundary between the through-holes and the heat conduction members on both the front and back surfaces of the printed circuit board. The ring-shaped discontinuity on the front surface side is a step due to the end of the heat conduction member protruding from the through-hole and a gap due to the side surface of the end of the heat conduction member being separated from the inner wall of the through-hole. The ring-shaped discontinuity on the back surface side is a step due to the end of the heat conduction member being inside the through-hole. The smoothness (height difference Rz) is -284 to 27 μm, which is 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 conduction member being press-fitted into the through-holes. That is, in Comparative Examples 1 and 2, in order to prevent the heat conduction member from slipping through the through-hole and falling off, for example, the outer shape of the heat conduction member is set to be approximately equal to the inner diameter of the through-hole. When the heat conduction member is press-fitted into the through-hole, the heat conduction member is inserted while expanding the through-hole by rubbing against the inner wall of the through-hole. As a result, the copper that is the heat conduction member is deformed, and there is unevenness in the insertion speed between the central part and the end part of the heat conduction member, and it is presumed that the ring-shaped discontinuity as described above is generated.

[0040] On the other hand, in the printed circuit board of the present embodiment, after inserting the heat conduction member 15 into the first through-hole 14 as described later, a part of the intermediate member 13 fixes the heat conduction member 15 to the first through-hole 14, polishes the surface of the heat conduction member 15, and polishes the surfaces of the first and second conductive layers 16 and 17. As a result, excessive stress is not applied to the first and second printed circuit boards 11 and 12 when the heat conduction member 15 is inserted, and variations in the fixing position of the heat conduction member 15 can be corrected.

[0041] Therefore, a printed circuit board 10 having sufficient reliability, smoothness, heat conductivity, and heat dissipation effect can be obtained.

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

[0043] On the first conductive layer 16, a land 16a is formed so as to cover the heat conduction member 15, and a pad 16b is formed so as to cover the connection wiring 21. The land 16a and the pad 16b are spaced apart and electrically insulated from each other. The land 16a and the pad 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 soldered to the pad 16b, for example. The pad 16b is electrically connected to the wiring pattern L via the connection wiring 21.

[0045] Since the first conductive layer 16 is smooth, the heat generating component 25 and the first conductive layer 16 are in close contact. Similarly, since the second conductive layer 17 is smooth, the heat sink 26 and the second conductive layer 17 are in close contact. As shown by the dashed line, the heat generated by the heat generating component 25 is quickly transmitted to the heat conduction member 15 through the first conductive layer 16. The heat that has passed through the heat conduction member 15 is quickly transmitted to the heat sink 26 through the second conductive layer 17. The heat that has flowed into the heat sink 26 is dissipated into the atmosphere from the fins of the heat sink 26.

[0046] Therefore, the heat diffusing in the horizontal direction parallel to the first printed circuit board 11 and the second printed circuit board 12, and the heat dissipated from the upper surface and the side surfaces of the heat generating component 25 are extremely small.

[0047] Since the heat conduction 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 conduction member 15 are in close contact, the exhaust heat characteristics of a part of the printed circuit board 10 are substantially improved.

[0048] Next, a method for manufacturing the printed circuit board according to the present embodiment will be described. FIG. 6 is a flowchart showing the manufacturing process of the printed circuit board, and FIGS. 7 to 10 are cross-sections sequentially showing the manufacturing process of the printed circuit board.

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

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

[0051] As shown in FIG. 7(c), form through-holes in the first printed circuit board 11, the intermediate member 13, and the second printed circuit board 12 so as to obtain a first through-hole 14 penetrating the first printed circuit board 11, the intermediate member 13, and the second printed circuit board 12 (step S3). In the figure, for clarity, they are shown as being separated from each other.

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

[0053] As shown in FIG. 8(a), lay a release film 41, stack the first printed circuit board 11, the intermediate member 13, and the second printed circuit board 12, insert a heat conduction member 15 into the first through-hole 14, and cover it with a release film 42 (step S4). In the figure, for clarity, they are shown as being separated from each other.

[0054] The outer diameter of the heat conduction member 15 is preferably made slightly smaller than the diameter of the first through-hole 14. For example, it is made about 100 μm smaller. Thereby, the heat conduction member 15 can be smoothly inserted into the first through-hole 14, and in the next step, a gap is secured through which a part of the intermediate member 13 can smoothly penetrate between the first through-hole 14 and the heat conduction member 15.

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

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

[0057] By hot pressing, the epoxy resin of the intermediate member 13 melts, and the melted epoxy resin is filled into the gap between the first through hole 14 and the heat conduction member 15 and is filled into the second through hole 20. When the epoxy resin solidifies, the first printed circuit board 11 and the second printed circuit board 12 are fixed by the intermediate member 13, and the heat conduction member 15 is fixed to the first through hole 14 by a part of the intermediate member 13.

[0058] Since 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, it is set in advance so that the total thickness after hot pressing is aligned with the thickness of the heat conduction member 15. Further, after hot pressing, the heat conduction member 15 and a part of the epoxy resin of the intermediate member 13 may protrude slightly from the first printed circuit board 11 and the second printed circuit board 12. For example, it is made to protrude by about 50 μm.

[0059] As shown in Fig. 9(a), the end faces of the heat conduction member 15 on the side of the first printed circuit board 11 and 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 portion of the heat conduction member 15 may protrude slightly, and the outer peripheral portion may sag, for example, to form a gentle convex shape as shown by the broken line. The height of the convex portion may be, for example, about 10 to 100 μm. By removing the convex portion as much as possible, the final smoothness is improved.

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

[0061] As shown in Fig. 9(b), copper plating is performed on the heat conduction member 15 exposed on the side of the first printed circuit board 11 and the first printed circuit board 11, and on the heat conduction member 15 exposed on the side of the second printed circuit board 12 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. For example, an electrolytic plating method capable of forming a thick film is preferable.

[0062] As shown in Fig. 10, the first conductive layer 16 and the second conductive layer 17 are mechanically polished (step S7). The 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. For example, it is performed in the same manner as the method in step S7. A roller type grindstone 44 is preferable so that a large area can be polished. Alternatively, slurry polishing may be used. Furthermore, chemical mechanical polishing (CMP) may be added. According to CMP, a more precise smooth surface can be obtained.

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

[0064] First, the heat conductive member 15 exposed on the first and second printed circuit board 11 and 12 sides is polished, and then the first conductive layer 16 and the second conductive layer 17 are polished. By the so-called two-step polishing, the surfaces of the first conductive layer 16 and the second conductive layer 17 are smoothly finished in the vicinity and periphery of the boundary between the first through hole 14 and the heat conductive 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] In addition, 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 the heat conductive member 15 is inserted into the first through hole 14. Therefore, warping, deformation, etc. of the printed circuit board are suppressed.

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

[0068] Here, the case where the printed circuit board has a two-layer laminated IVH structure has been described, but a multi-layer IVH structure may be further adopted.

[0069] Although the case where the heat conductive component 15 is a coin-shaped copper plate has been described, striped grooves (so-called coin serrations) may be provided along the thickness direction on the side surface of the copper plate.

[0070] If the convex portion on the side of the copper plate is inscribed in the first through hole 14, centering between the first through hole 14 and the copper plate becomes easy, 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 conduction member 15.

[0071] Also, 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 conduction member 15 is reduced, and current can flow stably. It is also possible to use the heat conduction member 15 as a current-carrying body.

[0072] The case of filling the second through hole 20 described above with a resin for hole filling different from a part of the intermediate member 13 will be described with reference to FIGS. 11 and 12. FIG. 11 is a flowchart showing a method of filling the second through hole 20 with a resin for hole filling different from a 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 resin for hole filling different from a part of the intermediate member 13.

[0073] As shown in FIG. 11, after step S2 shown in FIG. 6, a resin 31 for hole filling different from a part of the intermediate member 13 is filled into the second through hole 20 (step S21). When step S21 ends, the process proceeds to step S3 shown in FIG. 6.

[0074] As shown in FIG. 12(a), after injecting a thermosetting resin 31 in a fluid raw material state into the second through hole 20 of the first printed circuit board 11, the resin 31 is heated and cured. Although a member of the same type as a part of the intermediate member 13 is suitable for the resin 31, a different type of member may also be used. For example, the resin 31 is an epoxy resin of the same type as the epoxy resin that is a part of the intermediate member 13.

[0075] Since the thermosetting resin does not soften or flow even when reheated after being cured once, it does not affect step S5 shown in FIG. 6. As shown in FIG. 12(b), the second printed circuit board 12 is also processed in the same manner as the first printed circuit board 11.

[0076] By previously filling the second through-hole 20 with a member separate from a part of the intermediate member 13, 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 of this embodiment. The description of the parts that are the same as those in Embodiment 1 in this embodiment will be omitted, and the different points will be described. The difference between this embodiment and Embodiment 1 is that the configurations of the first printed circuit board and the second printed circuit board are different.

[0078] That is, as shown in FIG. 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. Here, the laminated first printed circuit board 51, intermediate member 13, and 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 provided between the two printed circuit boards 54 and fixing the printed circuit boards 54. That is, the printed circuit board 50 is a laminate of two printed circuit boards 54, and the other configurations are the same as those of the printed circuit board 10. Also, the number of printed circuit boards 54 to be laminated is arbitrary and is not particularly limited.

[0080] Next, the manufacturing method of the printed circuit board of this embodiment will be described. FIGS. 14 and 15 are cross-sections sequentially showing the main parts of the manufacturing process of the printed circuit board.

[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 that a first through hole 14 penetrating the first printed circuit board 51, the intermediate member 13, and the second printed circuit board 52 is obtained. In the figure, for ease of viewing, they are described as being separated from each other. The through holes may be formed individually or may be formed by overlapping them at once.

[0082] As shown in FIG. 14(b), with a release film 41 laid underneath, two printed circuit boards 54 and the intermediate member 13 are laminated, a heat conduction member 15 is inserted into the first through hole 14, and covered with a release film 42. In the figure, for ease of viewing, they are described as being separated from each other.

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

[0084] As shown in FIG. 15(a), the end faces of the heat conduction 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 FIG. 15(b), copper plating is performed on the heat conduction member 15 exposed on the first printed circuit board 51 side and the first printed circuit board 11, and on 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] As shown in FIG. 15(c), the first conductive layer 16 and the second conductive layer 17 are mechanically polished. The 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.

[0087] As described above, according to the present embodiment, similar to the aforementioned Embodiment 1, a printed circuit board having sufficient reliability, flatness, sufficient thermal conductivity, and a heat dissipation effect, and a method for manufacturing the same can be obtained.

[0088] Although some embodiments have been described above, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof.

Explanation of Reference Numerals

[0089] 10, 50 Printed Circuit Board 11, 51 First Printed Circuit Board 12, 52 Second Printed Circuit Board 13 Intermediate Member 14, 20 First, Second Through-Holes 15 Heat Conductive Member 16, 17 First, Second Conductive Layers 18 Core Material 19 Intermediate Material 21 Connection Wiring 25 Heat Generating Component 26 Heat Sink 31 Resin 41, 42 Release Film 43, 44 Grinding Stone 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; a first through hole penetrating the first printed circuit board, the intermediate member, and the second printed circuit board; a heat conductive 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 thermally 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 first conductive layer is provided with lands and pads that are spaced apart from the lands and electrically insulated from the lands so as to cover the heat conductive member; the second conductive layer opposite the lands and the pads is a continuous plane; A printed circuit board, characterized in that the surface roughness of the first conductive layer and the surface roughness of the second conductive layer are 10 μm or less in the vicinity and around the boundary between the first through hole and the thermal conductive 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. 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 material and the intermediate material, a plurality of second through holes are provided penetrating the core material and the intermediate material, 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 multiple second through holes provided in the first printed circuit board overlap with some of the multiple second through holes provided in the second printed circuit board.

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

5. 4. The printed circuit board according to claim 3, 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.

6. 4. The printed circuit board according to claim 3, 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.

7. 4. The printed circuit board according to claim 3, wherein the core material and the intermediate material are made of glass epoxy.

8. 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.

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

10. 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 penetrating 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 conductive member exposed in the first through hole; forming a first conductive film on the heat conductive member exposed on the first printed circuit board side and the first printed circuit board, and forming a second conductive film on the heat conductive 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:

11. 11. The method for manufacturing a printed circuit board according to claim 10, wherein the heating and pressurizing step is performed so that the thermally conductive member and a part of the intermediate member protrude by a predetermined height from the first printed circuit board and the second printed circuit board.

12. 11. The method for manufacturing a printed circuit board according to claim 10, wherein the heat conductive 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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