Multilayer printed circuit boards and electronic devices

Abstract

A multilayer printed circuit board includes a plurality of conductive layers formed of conductive materials, wherein a blank area from which the conductive material is removed is formed in at least a portion of at least one intermediate conductive layer formed inside the multilayer printed circuit board, and in the plurality of conductive layers, a plurality of island areas are formed by the conductive material included in the intermediate conductive layer in the blank area, and each of the plurality of island areas is not electrically connected to other areas included in the intermediate conductive layer and is arranged to be dispersed from each other.

Description

Technical Field

[0001] The present invention relates to a multilayer printed circuit board and an electronic device comprising the multilayer printed circuit board. Background Art

[0002] Generally, electronic equipment includes a printed circuit board having various types of electronic components mounted on its front surface. In such a printed circuit board, a multilayer printed circuit board is provided, which has a conductive layer formed of a conductive material not only on its front surface but also inside thereof. Summary of the invention

[0003] [Technical issues]

[0004] In the above-mentioned technology, there may be a case where it is necessary to form an area (hereinafter referred to as a blank area) in which no conductive material is provided in a relatively wide range in the conductive layer inside the multilayer printed circuit board. For example, depending on the layout of the antenna in the electronic device, etc., the conductive layer formed in the multilayer printed circuit board may interfere with the propagation of the radio signal transmitted and received by the antenna. In this case, it is necessary to remove the conductive material from the conductive layer of the multilayer printed circuit board to form the blank area.

[0005] In the case of forming a multilayer printed circuit board having such a blank area formed in a conductive layer inside the multilayer printed circuit board, for example, the blank area is formed by removing part of the conductive material from the conductive layer formed by attaching a copper foil on the front surface of a core member, etc., by an etching process, etc. Then, the insulating layer is formed by a process of providing a layered insulating material (e.g., a prepreg) containing a resin on the upper side of the conductive layer formed with the blank area and applying pressure and heat thereto or other processes.

[0006] At this time, in the case where the blank area has a wide range, when forming the insulating layer, a flow of the insulating material from the peripheral area of ​​the blank area to the blank area occurs, thereby causing wrinkles and the like on the front surface of the insulating layer. As a result, in some cases, the front surface of the insulating layer may not be made flat. In particular, in the case of forming an insulating layer with a small thickness, the amount of insulating material to be filled is small, and the influence of the blank area becomes relatively large. Therefore, such a problem is likely to occur.

[0007] The present invention is made in view of the above situation, and an object of the present invention is to provide a multilayer printed circuit board having a blank area filled with insulating material, the blank area being formed in a conductive layer within the board, and an electronic device including the multilayer printed circuit board.

[0008] [Solution to the problem]

[0009] A multilayer printed circuit board according to one aspect of the present invention includes a plurality of conductive layers formed of a conductive material, wherein, among the plurality of conductive layers, a blank area from which the conductive material is removed is formed in at least a portion of at least an intermediate conductive layer formed inside the multilayer printed circuit board, a plurality of island areas are formed of the conductive material in the intermediate conductive layer included in the blank area, and each of the plurality of island areas is not electrically connected to other areas included in the intermediate conductive layer and is arranged to be dispersed from each other. In addition, an electronic device according to one aspect of the present invention includes the multilayer printed circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a view showing a state inside an electronic device according to an embodiment of the present invention.

[0011] Figure 2 is a schematic cross-sectional view showing a multilayer printed circuit board according to an embodiment of the present invention.

[0012] Figure 3 is a plan view showing an example of a conductive layer inside a multilayer printed circuit board according to an embodiment of the present invention.

[0013] Figure 4 is a plan view showing another example of a conductive layer inside a multilayer printed circuit board according to an embodiment of the present invention.

[0014] Figure 5 is a plan view showing an example of a multilayer printed circuit board panel.

[0015] Figure 6 is a plan view showing still another example of the conductive layer inside the multilayer printed circuit board according to the embodiment of the present invention.

[0016] Figure 7 is a plan view showing still another example of the conductive layer inside the multilayer printed circuit board according to the embodiment of the present invention. DETAILED DESCRIPTION

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0018] Figure 1 1 is a plan view showing the state of the inside of an electronic device 1 according to an embodiment of the present invention. The electronic device 1 is, for example, a home game device, etc., and Figure 1 As shown, it includes a multi-layer printed circuit board 10 , a main board 20 and an antenna 30 .

[0019] The multilayer printed circuit board 10 is arranged along a vertical plane so that the front surface of the multilayer printed circuit board 10 faces the front side of the electronic device 1, and has an operation button 11 arranged on the front surface thereof. The operation button 11 is exposed on the front side of the electronic device 1 and can be operated from the front side by a user of the electronic device 1. The details of the structure of the multilayer printed circuit board 10 will be described later.

[0020] The main board 20 is disposed along a horizontal plane inside the electronic device 1, and has various types of circuit elements required for operating the electronic device 1 disposed on a front surface thereof. In addition, an antenna 30 is connected to the main board 20.

[0021] The antenna 30 is a conductive member that transmits and receives radio signals (electromagnetic waves) in a predetermined frequency band and is used to perform wireless communication between the electronic device 1 and another communication device. The antenna 30 may be a metal sheet antenna or the like. In the present embodiment, in a plan view, the antenna 30 is disposed between the main board 20 and the multilayer printed circuit board 10, and is hidden behind the multilayer printed circuit board 10 as viewed from the front side of the electronic device 1. Therefore, at least a portion of the electromagnetic waves radiated from the antenna 30 in a direction toward the front side of the electronic device 1 passes through the multilayer printed circuit board 10, as indicated by the dotted arrow in the figure.

[0022] Next, we will refer to Figure 2 and Figure 3 The structure of the multilayer printed circuit board 10 is described. Figure 2 shows a schematic cross-sectional shape of a multilayer printed circuit board 10, Figure 3 An example of a planar shape of a conductive layer inside the multilayer printed circuit board 10 is shown.

[0023] In the present embodiment, the multilayer printed circuit board 10 includes a total of four conductive layers, a conductive layer L1 on the front surface thereof, a conductive layer L4 on the rear surface thereof, and conductive layers L2 and L3 (intermediate conductive layers) disposed between the conductive layers L1 and L4 inside the multilayer printed circuit board 10. The conductive layers L2 and L3 are disposed on both sides of the core member C, and the insulating layers P1 and P2 are formed between the conductive layers L1 and L2 and between the conductive layers L3 and L4, respectively. Each conductive layer is formed of a conductive material such as copper foil, and each insulating layer is formed of an insulating material such as prepreg.

[0024] As described above, in order for the antenna 30 to wirelessly communicate with another communication device in front of the electronic device 1, the radio signal needs to pass through the multilayer printed circuit board 10. Therefore, the multilayer printed circuit board 10 has a structure in which electromagnetic waves transmitted and received by the antenna 30 are not blocked. Specifically, in the present embodiment, at least a portion of the conductive layers L2 and L3 is used as a blank area S, which is in a state where the conductive material is removed.

[0025] The blank area S may be an area overlapping with the antenna 30 when viewed from the front side of the electronic device 1. However, the conductive material in the blank area S is not completely removed, and there are some island-shaped areas, so that the conductive material is still scattered in multiple locations in the blank area S. Hereinafter, each area including the conductive material in the blank area S is referred to as an island area A.

[0026] Each island region A is completely surrounded by insulating material in a plan view, is not connected to other regions formed of conductive material in the conductive layer L2, such as other island regions A, and is electrically isolated. Therefore, all island regions A are not connected to the ground of the circuit and are in a floating state with a potential independent of other components.

[0027] The plurality of island regions A are arranged in a dispersed manner at substantially fixed distances from each other. Figure 3 In the example of , a plurality of island regions A are arranged in a grid manner at substantially equal intervals. More specifically, a plurality of island regions A are arranged in a straight line along a predetermined first direction and a second direction intersecting the first direction. Note that these first and second directions may be orthogonal to each other, and may be directions along the periphery of the multilayer printed circuit board 10 (i.e., along the long side direction and the short side direction of the multilayer printed circuit board 10). In addition, the blank area S is an area that is a portion of the multilayer printed circuit board 10, and in the case where the blank area S has a substantially rectangular shape, the first and second directions may be directions along the periphery of the blank area S (i.e., along the long side direction and the short side direction of the blank area S).

[0028] Note that although it is assumed here that the island areas A are arranged in a grid manner, the layout of the island areas A is not limited thereto. For example, in the case where there are plated through holes, non-plated through holes, etc. in the blank area S and the island areas A arranged at equal intervals overlap these through holes, etc., each island area A may be arranged at an offset position in a manner that does not overlap with each other. Figure 3 In the example shown, the island areas A are arranged around the through hole T, avoiding the through hole T. Furthermore, the island areas A may be arranged not only in a grid manner but also in various types of patterns, such as side by side or random arrangement.

[0029] When manufacturing the multilayer printed circuit board 10, a conductive layer L2 is formed on the entire front surface of the core member C using a conductive material. Then, from the conductive layer L2 formed by the conductive material, the conductive material in the blank area S is removed by etching, leaving a plurality of island areas A. Thereafter, an insulating material such as a prepreg is disposed on the conductive layer L2 to be pressurized, heated, etc., thereby forming an insulating layer P1 covering the conductive layer L2. At this time, the insulating material in a liquid state flows into the blank area S from which the conductive material is removed, and fills the blank area S. Here, the island area A is disposed in the blank area S so that the flow of the insulating material is dispersed, thereby preventing the flow of the insulating material from becoming faster. Therefore, wrinkles can be prevented from being generated in the insulating layer P1, and an insulating layer P1 having a uniform surface is formed.

[0030] In order to prevent wrinkles from being generated in the insulating layer P1, it is preferable to arrange the island regions A as uniformly as possible so that the distance between adjacent island regions A does not become too large and no portion other than any one island region A exists in the blank region S. Specifically, for example, in a case where the average value of the distance from each island region A to the nearest island region A (adjacent island region A) is set to rm, the island regions A are arranged uniformly so that a point where the distance to the nearest island region A exceeds rm does not exist in the blank region S. In other words, an area that does not include the island region A in a circular area with a radius of rm should not be included in the blank region S. In this way, a plurality of island regions A are uniformly arranged in the blank region S at predetermined intervals to some extent, and therefore, when an insulating material is filled in the blank region S to form the insulating layer P1 covering the conductive layer L2, the flow of the insulating material is dispersed, making it less likely that the insulating layer P1 will wrinkle.

[0031] Since each island region A is formed of a conductive material, a radio signal transmitted and received by the antenna 30 cannot pass through the area occupied by the island region A. Therefore, it is preferable that the area occupied by the island region A is sufficiently small relative to the entire blank region S.

[0032] In addition, in order not to interfere with the propagation of the radio signal received and transmitted by the antenna 30, each island area A preferably has a size that does not resonate with the frequency of the radio signal transmitted and received by the antenna 30. Specifically, when the wavelength of the electromagnetic wave undergoing wireless communication performed by the antenna 30 is set to λ, the electrical length L in the multilayer printed circuit board 10 corresponding to the wavelength of the electromagnetic wave is calculated by the following calculation formula:

[0033] L=λ / √ε

[0034] Here, ε is the relative dielectric constant of the insulating layer P1.

[0035] It is preferred that the size of each island region A (the length from one end to the other end thereof in the longest direction) is sufficiently small relative to the electrical length L corresponding to the wavelength of the electromagnetic wave. Specifically, the size of each island region A is preferably less than L / 4, and more preferably equal to or less than L / 10. In this way, by setting the size of each island region A to be relatively smaller than the electrical length L, the conductor included in each island region A can be prevented from resonating with the radio signal received and transmitted by the antenna 30, thereby preventing each island region A from interfering with the wireless communication performed by the antenna 30.

[0036] Note that although Figure 3 In the example shown, each island region A has a circular shape, but the shape of the island region A in a plan view is not limited thereto and various shapes may be adopted as long as the conditions regarding the above-mentioned size are satisfied. In addition, a plurality of island regions A may have shapes different from each other.

[0037] In the above description, it is assumed that the island area A is arranged in the blank area S in a substantially uniformly dispersed manner. However, in a specific area, the island area A can be arranged more densely than other areas. Specifically, for example, first, the radio signal cannot pass through the area where the signal line is arranged in each of the conductive layer L1 and the conductive layer L4, the area where the metal circuit component is mounted on the front surface of the multilayer printed circuit board 10, etc. Therefore, at the position overlapping with these areas, even if the conductive material remains inside the conductive layers L2 and L3, the effect on the radio signal is also small. In view of this, the island area A can be arranged more densely in these areas than other areas. In the following, the area in which the island area A is arranged more densely than other areas in the blank area S is referred to as the concentrated area X. Here, the dense arrangement of the island area A means that the area of ​​the island area A is large relative to the same unit area. For example, in the concentrated area X, it is assumed that the island area A is arranged so that the area ratio of the island area A in the concentrated area X becomes at least twice the area ratio of the island area A in other areas.

[0038] Note that, as described above, since each of the island regions A becomes an electrically independent floating state, when the size of each island region A is large, each island region A may resonate with the radio signal. Therefore, even in the concentrated area X, it is preferable that the size of each island region A to be set is sufficiently small relative to the electrical length L.

[0039] Figure 4An example of a conductive layer L2 having a concentrated area X is shown, in which the island areas A are densely arranged in the above-described manner. In the figure, a concentrated area X in which a plurality of island areas A are densely arranged is shown by a dotted line. The concentrated area X in the figure is an area overlapping with a signal line formed in the conductive layer L1 and a circuit component (operation button 11, etc.) connected to the signal line in a plan view. In the concentrated area X, the distance between adjacent island areas A becomes smaller than in other areas. Densely arranging the island areas A in this manner makes it more difficult to cause wrinkles in the insulating material when forming the insulating layer P1. Note that with respect to the average value rm of the distance between adjacent island areas A, the island areas A arranged in such a concentrated area X are not included, and it is preferred to calculate the average value rm of the distance between adjacent island areas A in an area outside the concentrated area X.

[0040] Note that although the layout of the island region A in the conductive layer L2 has been described so far, in a similar manner, the island region A may also be provided in the blank region S in the conductive layer L3. Furthermore, in the case where the island region A is provided in the conductive layer L3, it is preferred that the island region A be provided at a corresponding position in the conductive layer L3 that overlaps with the island region A in the conductive layer L2 in a plan view. As a result, in a plan view, an area where the radio signal from the antenna 30 is interfered with can be prevented from increasing, and the island region A may also be provided in the conductive layer L3.

[0041] The blank area S may be a partial area of ​​the multilayer printed circuit board 10, and may be an area covering the entire surface of the multilayer printed circuit board 10 to be installed in the electronic device 1. In the case of manufacturing a printed circuit board, in some cases, a plurality of printed circuit boards are manufactured simultaneously by a manufacturing method called panelization or the like. In this manufacturing method, first, a conductive layer and an insulating layer are stacked on a core member C having a large size to form a multilayer printed circuit board panel 50, and by partially cutting the multilayer printed circuit board panel 50, a plurality of printed circuit boards to be installed in an electronic device actually used are manufactured. In the case where the multilayer printed circuit board 10 to be installed in the electronic device 1 is manufactured in the above-mentioned method, according to the specifications of other types of printed circuit boards manufactured at the same time, even if the multilayer printed circuit board 10 does not need to have a conductive layer L2 and a conductive layer L3 inside, these layers are formed therein. In this case, in the case where the area covering the entire surface of the multilayer printed circuit board 10 is set as a blank area, the conductive material is removed from the blank area S of each of the conductive layer L2 and the conductive layer L3. Also in this case, in order to restrict the flow of the insulating material when the insulating layer P1 is formed in the manufacturing process of the multilayer printed circuit board panel 50, it is preferred to form a plurality of island areas A in the blank area S.

[0042] Figure 5An example of a multilayer printed circuit board panel 50 formed in the process of manufacturing a multilayer printed circuit board 10 by such a panelization manufacturing method is shown. In the example shown in the figure, four printed circuit boards including the multilayer printed circuit board 10 in the multilayer printed circuit board panel 50 are formed. Here, along the periphery of each multilayer printed circuit board, slits 51 penetrating the multilayer printed circuit board panel 50 are provided by a router or the like except for some connection points. Thereafter, each multilayer printed circuit board is separated from the multilayer printed circuit board panel 50 along the slits 51.

[0043] In this example, in the case where the entire surface of each multilayer printed circuit board 10 is set as the blank area S, the island area A may be arranged along the inner periphery of the blank area S. Figure 6 An example of this case is shown, and the island areas A each having an elongated strip shape are arranged adjacent to each other along the inner periphery of the multilayer printed circuit board 10 (i.e., along the inner periphery of the blank area S). By providing such island areas A, when the insulating layer P1 is formed in the multilayer printed circuit board panel 50, it is possible to restrict the insulating material from flowing from the outside to the inside of the blank area S. Note that although illustration is omitted in this figure, in this case as well, in addition to the island areas A provided along the outer periphery of the blank area S, the island areas A such as Figure 3 Or dispersed island areas A as shown in other figures can be set in the blank area S.

[0044] Furthermore, when manufacturing the multilayer printed circuit board panel 50, the island area A may be provided in the area where the slit 51 is formed. Since the slit 51 is located outside the multilayer printed circuit board 10 and is not used for the electronic device 1 in the final product, it is not necessary to limit the size of the island area A to a size corresponding to the electrical length L in the area corresponding to the slit 51. Therefore, one island area A surrounding the entire periphery of the multilayer printed circuit board 10 along the periphery of the multilayer printed circuit board 10 may be formed. Figure 7 A specific example of such an island region A is shown, and an example of the island region A formed in a region including the multilayer printed circuit board 10 and the slit 51 around the multilayer printed circuit board 10 from which the slit 51 is finally separated is shown.

[0045] As described above, according to the electronic device 1 of the present embodiment, the island area A is set in the blank area S so that wrinkles are not generated in the insulating layers P1 and P2, and the blank area S in which the conductive material is removed can be ensured in the conductive layers L2 and L3 inside the multilayer printed circuit board 10.

[0046] Note that the embodiments of the present invention are not limited to those described above. For example, the shape and layout of the island region A in the above description are merely examples, and the island region A can be formed into various shapes and layouts, depending on the overall shape of the multilayer printed circuit board 10 and the layout of signal lines, circuit components, through holes, etc.

[0047] In addition, in the above description, the multilayer printed circuit board 10 is a printed circuit board having four layers. However, the multilayer printed circuit board 10 is not limited thereto, and the present invention can be applied to various types of multilayer printed circuit boards as long as the multilayer printed circuit board 10 is a printed circuit board having a conductive layer inside.

[0048] In addition, in the above description, the blank area S is provided in the multilayer printed circuit board 10 so as to allow the transmission and reception of radio signals by the antenna 30, but the present invention is not limited thereto. Due to various other reasons, the present invention is applicable to the case where the blank area S is provided in the conductive layer inside the multilayer printed circuit board 10.

[0049] Reference numerals list

[0050] 1: Electronic equipment

[0051] 10:Multilayer printed circuit board

[0052] 11: Operation button

[0053] 20: Motherboard

[0054] 30: Antenna

[0055] 50:Multilayer printed circuit board panel

[0056] 51: Slit

[0057] L1, L2, L3, L4: Conductive layer

[0058] P2 P1: Insulation layer

[0059] C: Core component

Claims

1. A multilayer printed circuit board, comprising: A plurality of conductive layers formed of conductive material, wherein Among the plurality of conductive layers, a blank area where conductive material is removed is formed in at least a portion of at least one intermediate conductive layer formed inside the multilayer printed circuit board, The plurality of island regions are formed of a conductive material included in the intermediate conductive layer in the blank region, and Each of the plurality of island regions is not electrically connected to other regions included in the intermediate conductive layer and is disposed to be dispersed from one another, in A portion of the concentrated area in the blank area is formed with a plurality of island areas that are denser than areas outside the concentrated area. In the concentrated area, the island areas are arranged so that the area ratio of the island areas in the concentrated area becomes at least twice the area ratio of the island areas in the other areas.

2. The multilayer printed circuit board according to claim 1, wherein The concentrated area includes an area overlapping with an area where the signal line is provided in another conductive layer in a plan view.

3. The multilayer printed circuit board according to claim 1, wherein The concentrated area includes an area overlapping with circuit components arranged on the front surface of the multilayer printed circuit board in plan view.

4. The multilayer printed circuit board according to claim 1, wherein The plurality of island regions include a plurality of island regions arranged along the inner circumference of the blank region.

5. The multilayer printed circuit board according to claim 1, wherein The plurality of island regions include a plurality of island regions arranged in a grid manner in a blank area.

6. An electronic device comprising: A multilayer printed circuit board comprising: A plurality of conductive layers formed of conductive material, wherein Among the plurality of conductive layers, a blank area where conductive material is removed is formed in at least a portion of at least one intermediate conductive layer formed inside the multilayer printed circuit board, The plurality of island regions are formed of a conductive material included in the intermediate conductive layer in the blank region, and Each of the plurality of island regions is not electrically connected to other regions included in the intermediate conductive layer and is disposed to be dispersed from one another, A portion of the concentrated area in the blank area is formed with a plurality of island areas that are denser than areas outside the concentrated area. In the concentrated area, the island areas are arranged so that the area ratio of the island areas in the concentrated area becomes at least twice the area ratio of the island areas in other areas.

7. The electronic device according to claim 6, further comprising: An antenna for performing wireless communications, wherein Each of the plurality of island regions is smaller in size than 1 / 4 of an electrical length in the multilayer printed circuit board, the electrical length corresponding to a wavelength of wireless communication.

8. The electronic device according to claim 7, wherein Each of the plurality of island regions is smaller in size than 1 / 10 of the electrical length.

Images