JP2011049378A - Multilayer substrate and electronic apparatus - Google Patents

Abstract

A flexible layout design is realized while maintaining an electromagnetic shield in a multilayer substrate.
[Solution]
The electromagnetic shield S includes a ground multilayer L3 layer and an L2 layer at the bottom of the substrate. The L3 layer includes a first ground layer 32 formed in a solid shape leaving the first region P1. The L2 layer includes a second ground layer 34 formed by sandwiching the first ground layer 32 and the insulating layer 16 in a second region Q1 that includes the first region P1 in a plan view and is a part of the layer. The first ground layer 32 and the second ground layer 34 are electrically connected by a large number of through holes 50 arranged so as to surround the first region P1.
[Selection] Figure 1

Description

  The present invention relates to a technique for shielding unnecessary radiation in a multilayer substrate.

  Conventionally, there are multilayer substrates in which wiring patterns for power and signals are laminated. FIG. 6 is a cross-sectional view of the multilayer printed circuit board disclosed in Patent Document 1. In the multilayer printed board, signal layers S1 to S4, power supply layers E1 and E2, and ground layers G1 and G2 are formed, and these wiring patterns are insulated by insulating layers 111 to 117. The ground layers G1 and G2 are entirely connected by a shield G3 so as to enclose the power supply layers E1 and E2 and the signal layers S2 and S3. As a result, the electromagnetic field generated between the power source and the ground layer can be confined, and radiation to the outside can be suppressed.

JP 2004-363347 A

However, since the ground layers G1 and G2 occupy all the specific layers, it can be a restriction on the layout design of the multilayer board.
The present invention has been made under such a background, and an object thereof is to provide a technique capable of realizing a more flexible layout design while maintaining an electromagnetic shield in a multilayer board.

  The multilayer substrate according to the present invention is a multilayer substrate including an electromagnetic shield body that shields a wiring disposed therein, and the electromagnetic shield body includes a ground multilayer in the substrate, and the ground multilayer includes a first region. A first ground layer formed so as to surround the first ground layer, and a second region that includes the first region in plan view and is a part of the layer, with the first ground layer and the insulating layer being separated from each other. And a plurality of through-holes that are arranged so as to surround the first region and electrically connect the first ground layer and the second ground layer.

In addition, in the region outside the second region where the second ground layer is formed, wiring having an operation frequency lower than that of the wiring disposed inside the electromagnetic shield body is disposed. It doesn't matter if you have.
In addition, the wiring disposed inside the electromagnetic shield body includes a high-frequency signal wiring, and the interval in the direction parallel to the second ground layer in the arrangement of the plurality of through holes is the insulation of the high-frequency signal. It does not matter even if it is 1/4 or less of the wavelength in the layer.

  The second ground layer is formed so as to surround the third region in the second region, and the ground multilayer further includes the third region in a plan view and is a part of the layer. The fourth region includes a third ground layer formed by separating the second ground layer and the insulating layer, and is arranged so as to surround the third region, and the second ground layer and the third ground layer are arranged. A plurality of through holes that are electrically connected may be provided.

  In addition, an electronic device according to the present invention includes the multilayer substrate.

  According to the multilayer substrate according to the present invention, a more flexible layout design can be realized while maintaining the electromagnetic shield in the multilayer substrate.

1 is a sectional view conceptually showing a multilayer substrate 1. 2 is a plan view conceptually showing an L3 layer of the multilayer substrate 1. FIG. 2 is a plan view conceptually showing an L2 layer of the multilayer substrate 1. FIG. 2 is a cross-sectional view conceptually showing a multilayer substrate 2. FIG. It is a top view which shows the multilayer substrate 2 notionally, (a) shows L4 layer, (b) shows L3 layer, (c) shows L2 layer. It is sectional drawing which shows notionally the conventional multilayer printed circuit board (patent document 1).

(Embodiment 1)
Hereinafter, embodiments will be described with reference to the drawings.
FIG. 1 is a sectional view conceptually showing a multilayer substrate 1 according to the first embodiment.
The multilayer substrate 1 is built in a housing of a general mobile phone. In particular, it is located directly below the operation key portion on the surface of the casing of the mobile phone.

The multilayer substrate 1 is formed by sequentially stacking six layers from the surface to L6 to L1 and insulating layers 10, 12, 14, 16, and 18 interposed between the layers.
The insulating layers 10, 12, 14, 16, 18 interposed between the respective layers are made of, for example, a silicon oxide (SiO ₂ ) material.
The structure of each layer of L6 to L1 is as follows.

The L6 layer includes various electronic components 20 such as an LSI (Large Scale Integrated circuit) and a capacitor, and includes a wiring layer 22 that is a digital signal wiring (high-speed bus, low-speed bus, various signals). As a material for the digital signal wiring of the wiring layer 22, for example, copper (Cu) or polysilicon is used.
Here, the high-speed bus has a bus clock frequency of several tens of MHz or more, and is used, for example, as a transmission path for images taken by a mobile phone camera. Such a high-speed bus tends to emit unnecessary radiation. When unnecessary radiation reaches the antenna of the mobile phone, it adversely affects reception sensitivity and call quality.

In contrast, a low-speed bus has a bus clock frequency of several MHz or less, and is relatively less affected by unnecessary radiation than a high-speed bus.
The surface of the L6 layer is covered with a rectangular shield upper lid 23, and the shield upper lid 23 shields radiation from the L6 layer in the upward direction.
The L5 layer includes a wiring layer 24 that is a digital signal wiring similar to the wiring layer 22.

The L4 layer includes a wiring layer 26 that is a digital signal wiring similar to the wiring layer 22.
Further, a through hole 48 penetrating from the L6 layer to the L3 layer is formed. A large number of through-holes 48 are formed so that the upper side is in electrical contact with the shield upper lid 23 and the lower side is in electrical contact with the ground layer 32 of the L3 layer, and the L6 layer to the L3 layer are surrounded from the side. Has been. The diameter of the through hole 48 is, for example, about 100 μm. Further, when the L6 layer of the through hole 48 is viewed in plan, the interval between the adjacent through holes 48 is, for example, about 2 mm, and is formed with a close interval so as not to leak electromagnetic waves to the outside.

FIG. 2 is a plan view conceptually showing the L3 layer. Although a part of the cross section cut along the line AA in FIG. 2 generally corresponds to FIG. 1, the dimensions do not correspond accurately.
As shown in FIG. 2, the L3 layer includes a wiring layer 30 formed in the region P1 and a ground layer 32 formed in a solid shape on the most surface, which is the remaining portion of the region P1.
Then, 34 through holes 50 are formed at predetermined intervals l (for example, the interval l is about 2 mm) so as to surround the region P1 at the peripheral edge of the region P1. The through hole 50 is formed, for example, by opening a hole for a through hole in the insulating layer 16 and embedding copper powder in the hole.

The diameter of the through hole 50 is, for example, about 100 μm to 200 μm. Through the through hole 50, the ground layer 32 of the L3 layer and the ground layer 34 of the L2 layer are electrically connected.
FIG. 3 is a plan view conceptually showing the L2 layer. A part of a cross section taken along the line BB in FIG. 2 substantially corresponds to FIG.

  As shown in FIG. 3, the L2 layer has a size slightly larger than the region P1 when the L2 layer is viewed in plan (when the multilayer substrate 1 is viewed in plan) (this ensures the area of the through hole 50). The ground layer 34 formed in the region Q 1, the key matrix circuit for the operation keys and the wiring layer 36 for the low-speed bus, and the ground layer 38 formed separately from the ground layer 34. Prepare.

The L1 layer includes a key matrix circuit of operation keys similar to the wiring layer 36 and a wiring layer 38 for a low-speed bus.
As shown in FIG. 1, in the multilayer substrate 1, the upper direction radiated from the wiring layers 24, 26, 30 and the like by the shield upper lid 23 on the surface of the L6 layer and the through holes 48 on the side surfaces from the L6 layer to the L3 layer Shield unwanted radiation in the horizontal direction. Further, unnecessary radiation downward is shielded by a part of the ground layer 32 of the L3 layer and the ground layer 34 of the L2 layer. Furthermore, the 34 through holes 50 can shield unnecessary radiation in the gap direction between the ground layer 32 of the L3 layer and the ground layer 34 of the L2 layer.

In FIG. 1, a box-like portion to which the shield upper lid 23 for shielding such unnecessary radiation, the through hole 48, a part of the ground layer 32, the ground layer 34 of the L2 layer, and the through hole 50 is connected is electromagnetically shielded. Shown as body S.
Further, as shown in FIG. 2, the specific layer is not occupied entirely by the ground layer as in the prior art, and the wiring layer 30 is provided in the region P1 that is surrounded by the ground layer 32 of the L3 layer. Therefore, the L3 layer can be used effectively.

Further, also in the L2 layer, the wiring layer 36 and the ground layer 38 are provided in the region R1 which is a portion other than the region Q1 of the ground layer 34. Compared to the conventional case where all the specific layers are occupied only by the ground layer, it is possible to contribute to a flexible layout design. As a result, it can be expected to contribute to thinning and cost reduction of the multilayer substrate.
As described above, a high-speed bus that easily emits unnecessary radiation is preferably accommodated in the electromagnetic shield body S. On the other hand, a low-speed bus that is less affected by unnecessary radiation may be arranged outside the electromagnetic shield body S. As described above, according to the present embodiment, since a flexible layout design can be performed, the high-speed bus that should be put inside the electromagnetic shield body S is inserted inside, and the low-speed bus that does not need to be put inside is designed to go outside. Easy to do.

Further, it can be said that the L2 layer and the L3 layer are layers (ground multilayer) constituting the lower part (bottom part) of the electromagnetic shield body S.
(Embodiment 2)
In the first embodiment, the ground multilayer constituting the lower part of the electromagnetic shield body S is two layers of the L2 layer and the L3 layer, whereas in the second embodiment, the lower part of the electromagnetic shield body S is constituted. The ground multilayer is composed of three layers from L4 layer to L2 layer, thereby enabling more various layouts.

FIG. 4 is a sectional view conceptually showing the multilayer substrate 2 according to the second embodiment. Since it is basically the same as the multilayer substrate 1 shown in FIG. 1 except that the configuration of the ground multilayer is different, the same members are denoted by the same reference numerals and description thereof is omitted. In addition, although not illustrated in the electromagnetic shield body S, the wiring layer is formed like FIG.
As shown in FIG. 4, a through hole 52 penetrating from the L6 layer to the L4 layer is formed. A large number of through-holes 52 are formed so that the upper side is in electrical contact with the shield upper lid 23 and the lower side is in electrical contact with the ground layer 62 of the L4 layer, and the L6 layer to the L4 layer are surrounded from the side. Has been.

As shown in FIG. 5A, in the L4 layer, 34 through holes 54 are formed side by side so as to surround the region P2 in the peripheral portion of the region P2. The interval between adjacent through holes 54 is, for example, about 2 mm, similarly to the through hole 50 (FIG. 2).
As shown in FIG. 5B, in the L3 layer, the ground layer 64 is formed in the region Q2 (one size larger than the region P2). The ground layer 64 is hollow in the region T. That is, the region Q2 has a positional relationship of surrounding the region T.

Ten through holes 56 are formed at the periphery of the region T so as to surround the region T, for example, at intervals of about 2 mm.
As shown in FIG. 5C, in the L2 layer, the ground layer 66 is formed in the region U (one size larger than the region T).
In the multilayer substrate 2, unnecessary radiation radiated from an internal wiring layer or the like can be shielded by the shield body S. Unnecessary radiation from the inside upward or laterally is shielded by the shield upper lid 23 and the through hole 52. Further, unnecessary downward radiation is shielded by a part of the ground layer 62 of the L4 layer, the ground layer 64 of the L3 layer, and the ground layer 66 of the L2 layer. Furthermore, unnecessary radiation in the gap direction between the ground layer 62 of the L4 layer and the ground layer 64 of the L3 layer is shielded by the through hole 54, and the ground layer 64 of the L3 layer and the L2 layer of the L2 layer are shielded by the through hole 56. Unwanted radiation in the gap direction with the ground layer 66 can be shielded.

According to the multilayer substrate 2 of the second embodiment, the wiring layer can be provided not only in the region P2 but also in the region T while maintaining the electromagnetic shield, which can contribute to a more flexible layout design.
<Supplement>
As mentioned above, although embodiment of this invention was described, this invention is not limited to said content, It can implement also in the various forms for achieving the objective of this invention, its related or incidental object, for example, The following may also be used.
(1) Although not particularly shown in FIG. 1 and the like, the power supply layer may be included in the L6 to L1 layers, and the ground layer may be included in the L6 to L4 and L1 layers as necessary. .
(2) The shape of the region P1 is not limited to that shown in FIG. It can be changed depending on the wiring scale (number, length, etc.) of the wiring layer to be formed in the region P1.
(3) The region Q1 has been described as having a size that is slightly larger than the region P1, but if the region Q1 is large enough to enclose (include) the region P1 when the multilayer substrate 1 is viewed in plan, the electromagnetic shield body It can serve as the bottom part of S.
(4) When the ground potential of the ground layer 32 and the ground layer 34 is set to a potential corresponding to the ground of the antenna by being electrically connected to the ground line of the antenna of the mobile phone, particularly unnecessary radiation to the antenna. It is effective because it can prevent.
(5) Although it has been described that the ground layer connected to the ground layer 32 of the L3 layer is formed in the L2 layer, the ground layer is not necessarily adjacent to the insulating layer. For example, it may be formed in the L1 layer, and the ground layer of the L3 layer and the ground layer of the L1 layer may be connected by a through hole.
(6) The predetermined interval l (L) for arranging the through holes 50 is ¼ or less, particularly ¼ of the wavelength of the high frequency signal of the wiring layers 24, 26, and 30 that are wirings that may include a high-speed bus. If it is narrow enough, a shielding effect can be obtained.

Specifically, the wavelength λ of the high-frequency signal is obtained from an equation of λ = C / {f · (ε _r ) ^1/2 } (C: speed of light, f: frequency, ε _r : relative dielectric constant of the insulating layer). It is done.
As an example, if the frequency f of the high-frequency signal is 2 GHz, if ε _r = 1, the wavelength λ is 150 mm from the above equation, so the interval l should be set sufficiently narrow with respect to ¼ of 38 mm. Is preferred.
(7) In the embodiment, the multilayer substrate 1 mounted in the mobile phone has been described as an example. However, the multilayer substrate 1 is not limited to the mobile phone and is mounted on various electronic devices (especially communication devices in which noise is likely to be a problem). It can be applied to a multilayer substrate.

  The multilayer substrate according to the present invention contributes to a layout design with a high degree of freedom.

1 Multilayer substrate 10, 12, 14, 16, 18 Insulating layer 24, 26, 30 Wiring layer 32 Ground layer (first ground layer)
34 Ground layer (second ground layer)
50 through holes (multiple through holes)
One of the L2 ground multilayers (Figures 1 and 4)
One of the L3 ground multilayers (Figures 1 and 4)
One of the L4 ground multilayers (Figure 4)
P1 area (first area)
P2 area (first area)
Q1 area (second area)
Q2 area (second area)
T region (third region)
U area (4th area)
R1 region (region surrounding the second region Q1)
S Electromagnetic shield body l Interval

Claims (5)

A multilayer substrate including an electromagnetic shield body that shields wiring disposed inside,
The electromagnetic shield includes a ground multilayer in a substrate,
The ground multilayer is
A first ground layer formed so as to surround the first region;
The second region that includes the first region in a plan view and is a part of the layer is configured by a second ground layer that is formed by separating the first ground layer and the insulating layer,
A multilayer substrate comprising a plurality of through-holes arranged so as to surround the first region and electrically connecting the first ground layer and the second ground layer. Wiring having a lower operating frequency than the operating frequency of the wiring arranged inside the electromagnetic shield body is arranged in a region outside the second region where the second ground layer is formed. The multilayer substrate according to claim 1. The wiring disposed inside the electromagnetic shield body includes high-frequency signal wiring,
2. The multilayer according to claim 1, wherein in the arrangement of the plurality of through holes, an interval in a direction parallel to the second ground layer is ¼ or less of a wavelength of the high-frequency signal in the insulating layer. substrate. The second ground layer is formed so as to surround a third region in the second region,
The ground multilayer further includes a third ground layer formed in a fourth region that includes the third region in a plan view and is a part of the layer with the second ground layer and the insulating layer separated from each other,
The multilayer substrate according to claim 1, further comprising a plurality of through holes that are arranged so as to surround the third region and electrically connect the second ground layer and the third ground layer.   An electronic device comprising the multilayer substrate according to any one of claims 1 to 4.

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