JP2009182204A - Substrate fitting structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate fitting structure capable of lowering the impedance of a specified inner-layer conductor pattern without adding a via. <P>SOLUTION: The substrate fitting structure comprises a chassis 4 and a multilayer substrate 1 fixed on the chassis 4 with a screw. The multilayer substrate 1 has a plurality of insulating layers 11 to 15 which are laminated, and a plurality of conductor patterns 20 to 25 to form a ground layer or electric circuit are formed on top surfaces or/and back surfaces of a plurality of insulating layers including at least one insulating layer disposed as an inner layer among the plurality of insulating layers. A spot facing portion is recessed in the top or reverse surface of the multilayer substrate 1, the head 51 of the screw 5 is installed in the spot facing portion 16, and the screw body 52 of the screw 5 is screwed in the chassis 4, so that the head 51 of the screw 5 comes into contact with the conductor pattern 23 exposed on the bottom surface of the spot facing portion 16. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a board mounting structure for mounting a multilayer board on a chassis in various electronic devices.

  Conventionally, in various electronic devices such as portable terminals, a board mounting structure has been proposed in which a multilayer board is installed on a metal chassis and electromagnetic noise generated from the multilayer board is blocked by the chassis (for example, Patent Document 1). reference).

  For example, in the board mounting structure shown in FIG. 3, a multilayer board (10) is installed on a boss portion (41) projecting from the chassis (4), and the multilayer board (10) is screwed (5). ) To the boss portion (41) of the chassis (4).

  The multilayer substrate (10) includes a plurality of insulating layers (11) to (15) stacked on each other, and a plurality of conductor patterns (20) to (20) to be ground layers and circuit patterns on the front and back surfaces of each insulating layer. (25) is formed. Further, vias (31) to (35) are formed in the plurality of insulating layers (11) to (15), and the plurality of conductor patterns (20) to (25) are connected to each other.

In the substrate mounting structure shown in FIG. 3, the conductor pattern (25) on the front surface and the conductor patterns (21) to (24) on the inner layer are connected to the conductor pattern (20) on the back surface via the vias (31) to (35). The plurality of conductor patterns (20) to (25) are connected to the chassis (4) by connecting the back conductor pattern (20) to the boss portion (41) of the chassis (4).
According to the board mounting structure, electromagnetic noise generated from the multilayer board (10) is shielded by the shielding effect of the chassis (4).
JP-A-9-163193

FIG. 4 shows an equivalent circuit diagram relating to the plurality of conductor patterns (21) to (25) of the multilayer substrate (10). A power source (7) is connected to the plurality of conductor patterns (21) to (25), and vias (31) to (35) formed in the respective insulating layers are resistors interposed on the ground side of the power source (7). R1 to R5.
However, since one via has a resistance value of about 80 mΩ, for example, there is a potential difference between the resistors R1 to R5. As a result, there is a problem that the impedance of each of the conductor patterns (21) to (25) is not sufficiently lowered. .

Since the conductor pattern (25) on the surface of the multilayer substrate (10) shown in FIG. 3 is connected to the chassis (4) via the screw (5), the impedance of the conductor pattern (25) is lowered to some extent. Although it is possible, for example, even if one conductor pattern (23) in the inner layer needs to lower the impedance in particular, the screw (5) is sufficient to lower the impedance of the conductor pattern (23). It is not what you do.
Conventionally, with respect to the inner layer conductor pattern (23) which is highly required to lower the impedance, vias for connecting the conductor pattern (23) to the chassis (4) have been added. There is a problem that the manufacturing cost increases due to the expansion.

  In addition, in the board mounting structure shown in FIG. 3, when a component such as a battery pack (6) is installed along the surface of the multilayer board (10), the head of the screw (5) from the surface of the multilayer board (10). Since (51) protrudes, there must be a gap between the multilayer substrate (10) and the battery pack (6), and as a result, there is a problem in that the electronic device can be made thin.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a board mounting structure that can reduce the impedance of a specific inner layer conductor pattern without adding vias and can reduce the thickness of the device.

  A substrate mounting structure according to the present invention includes a chassis (4) having at least a surface layer portion having conductivity, and a multilayer substrate (1) fixed on the chassis (4) by screws (5). The substrate (1) includes a plurality of laminated insulating layers, and a ground layer or a back surface or both surfaces of the plurality of insulating layers including at least one insulating layer located in the inner layer among the plurality of insulating layers. A plurality of conductor patterns serving as an electric circuit are formed.

  Here, a counterbore part (16) is recessed in the front or back surface of the multilayer substrate (1) through one or a plurality of insulating layers, and the screw (5) is formed in the counterbore part (16). The head (51) is installed, and the screw portion (52) of the screw (5) is screwed into the chassis (4), and the head (51) of the screw (5) is turned into the counterbore portion (16). The conductor pattern is in electrical communication with the chassis (4) through screws (5) in contact with the conductor pattern exposed on the bottom surface of the chassis.

  Specifically, the conductor pattern in contact with the screw portion (52) of the screw (5) constitutes a ground layer, the chassis (4) constitutes a ground potential portion, and the conductor pattern becomes the chassis (4). The conductive pattern is kept at the ground potential by conducting to the ground.

According to the substrate mounting structure of the present invention, the conductor pattern exposed on the bottom surface of the spot facing portion (16) of the multilayer substrate (1) is connected to the chassis (4) via the screw (5). Here, since the resistance value of the screw (5) is much smaller than that of the via, there is only a slight voltage drop between the conductor pattern and the chassis (4). As a result, the impedance of the conductor pattern Will drop sufficiently.
Therefore, the impedance of a specific inner layer conductor pattern can be lowered by forming a conductor pattern that needs to lower the impedance particularly on the exposed surface of the insulating layer that is exposed from the spot facing portion (16).

  Further, the counterbore part (16) of the multi-layer substrate (1) accommodates all or part of the head (51) of the screw (5), so that the head (51) of the screw (5) is accommodated. When the components are arranged along the gap, the gap between the multilayer substrate (1) and the components can be made smaller than before.

  According to the substrate mounting structure of the present invention, the impedance of a specific inner layer conductor pattern can be lowered without adding vias, and the device can be made thinner.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
In the substrate mounting structure according to the present invention, as shown in FIG. 1, a multilayer substrate (1) is installed on a boss portion (41) projecting from a magnesium chassis (4), and the multilayer substrate (1). Is fixed to the boss portion (41) of the chassis (4) with a metal screw (5).

  The multilayer substrate (1) is formed by laminating a first insulating layer (11), a second insulating layer (12), a third insulating layer (13), a fourth insulating layer (14), and a fifth insulating layer (15). Constructed on the front and back of each insulating layer are a back conductor pattern (20), a first inner conductor pattern (21), a second inner conductor pattern (22), and a third inner conductor pattern, which are ground and circuit patterns. (23) A fourth inner layer conductor pattern (24) and a surface conductor pattern (25) are formed. Further, vias (31) to (35) are formed in the first to fifth insulating layers (11) to (15), and the plurality of conductor patterns (20) to (25) are connected to each other.

A counterbore part (16) penetrating the fifth insulating layer (15) and the fourth insulating layer (14) is recessed in the surface of the multilayer substrate (1). The third inner layer conductor pattern (23) on the third insulating layer (13) is exposed.
The screw (5) has a head portion (51) housed in a counterbore portion (16) of the multilayer substrate (1), a screw portion (52) having a third insulating layer (13), and a second insulating layer. (12) and the 1st insulating layer (11) are penetrated, The front-end | tip part is screwed in the boss | hub part (41) of a chassis (4).

As a result, the head (51) of the screw (5) comes into contact with the third inner layer conductor pattern (23), and the third inner layer conductor pattern (23) is electrically connected to the chassis (4) via the screw (5). Is conductive.
Further, a battery pack (6) is installed on the surface of the multilayer substrate (1) so as to cover the spot facing (16), and the gap between the multilayer substrate (1) and the battery pack (6) is almost zero. It has become.

  FIG. 2 is an equivalent circuit diagram relating to the first to fifth conductor patterns (21) to (25) of the multilayer substrate (1). A power source (7) is connected to these conductor patterns (21) to (25), and vias (31) to (35) formed in the respective insulating layers are resistors interposed on the ground side of the power source (7). R1 to R5.

Further, the third inner layer conductor pattern (23) of the multilayer substrate (1) shown in FIG. 1 is connected to the chassis (4) through the screws (5), and the screws (5) are connected as shown in FIG. A bypass line resistor Rx is formed in parallel with the resistors R1 to R3 interposed on the ground side of the third inner layer conductor pattern (23) and the power source (7).
The screw (5) has a much larger diameter than the via, and its resistance value is much smaller than the resistance value of the via. Therefore, the potential difference generated in the resistor Rx is extremely small. The impedance of the three inner layer conductor pattern (23) is sufficiently lowered.

Therefore, the third inner layer conductor pattern (23) is set to have a higher necessity of lowering the impedance than the other conductor patterns (21), (22), (24), and (25).
Thus, for example, when the third inner layer conductor pattern (23) is a ground layer, a high shielding effect is obtained against electromagnetic waves generated from the multilayer substrate (1). Further, when the third inner layer conductor pattern (23) is a circuit pattern, effects such as stabilization of circuit operation and reduction of voltage drop can be obtained due to a decrease in impedance.

  Further, since the head (51) of the screw (5) is completely accommodated in the counterbore (16) of the multilayer substrate (1), there is almost no gap between the multilayer substrate (1) and the battery pack (6). As a result, the thickness of the electronic device can be reduced.

In addition, each part structure of this invention is not restricted to the said embodiment, A various deformation | transformation is possible within the technical scope as described in a claim. For example, the chassis (4) is not limited to one that is entirely formed of metal, and it is possible to adopt one in which only the surface layer portion is made of metal.
In addition, the multilayer substrate (1) is not limited to the one having a five-layer laminated structure as shown in FIG.

Further, the surface conductor pattern (25) and the back conductor pattern (20) of the multilayer substrate (1) can be omitted, and the plurality of inner layer conductor patterns (21) to (24) are at least a single inner layer. The present invention can be implemented in a configuration in which a conductor pattern is formed.
Furthermore, the vias (31) to (35) need not be formed in all the insulating layers, but may be formed in the minimum necessary insulating layer.

It is sectional drawing of the board | substrate attachment structure which concerns on this invention. It is an equivalent circuit diagram regarding the conductor pattern of the board mounting structure. It is sectional drawing of the conventional board | substrate attachment structure. It is an equivalent circuit diagram regarding the conductor pattern of the board mounting structure.

Explanation of symbols

(1) Multilayer substrate
(11) First insulation layer
(12) Second insulation layer
(13) Third insulation layer
(14) Fourth insulation layer
(15) Fifth insulating layer
(16) Counterbore
(21) First inner layer conductor pattern
(22) Second inner layer conductor pattern
(23) Third inner layer conductor pattern
(24) 4th inner layer conductor pattern
(25) Surface conductor pattern
(4) Chassis
(41) Boss
(5) Screw
(51) Head
(52) Screw
(6) Battery pack

Claims (3)

A chassis (4) having at least a surface layer portion having conductivity and a multilayer substrate (1) fixed on the chassis (4) by screws (5) are formed. The multilayer substrate (1) is laminated. A plurality of conductor patterns that comprise a plurality of insulating layers and that are ground layers or electrical circuits are provided on the front surface, back surface, or both surfaces of the plurality of insulating layers including at least one insulating layer located in the inner layer among the plurality of insulating layers. In the board mounting structure being formed,
A counterbore part (16) is recessed in the front surface or the back surface of the multilayer substrate (1) through one or a plurality of insulating layers, and the head part (16) of the screw (5) is formed in the counterbore part (16). 51) is installed, the screw portion (52) of the screw (5) is screwed into the chassis (4), and the head portion (51) of the screw (5) is placed on the bottom surface of the counterbore portion (16). A board mounting structure, wherein the conductive pattern comes into contact with an exposed conductive pattern and is electrically connected to the chassis (4) through a screw (5).   The conductor pattern in contact with the screw portion (52) of the screw (5) constitutes a ground layer, the chassis (4) constitutes a ground potential portion, and the conductor pattern is electrically connected to the chassis (4). 2. The board mounting structure according to claim 1, wherein the conductor pattern is maintained at a ground potential.   The head portion (51) of the screw (5) is entirely accommodated in the counterbore portion (16) of the multilayer substrate (1), and covers the counterbore portion (16) of the multilayer substrate (1). The board mounting structure according to claim 1 or 2, wherein the board is installed.

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