JP2006114646A - Circuit board equipment - Google Patents

Abstract

A shield case for covering an electronic component on a circuit board and a circuit board device capable of improving a shielding effect in a shield structure are provided.
In a circuit board device in which a shield case 2 is covered on a circuit board 1 on which an electronic component 13 is mounted, and the shield case 2 is engaged and held by a holding member 14a on the circuit board 1, a holding member 14a, Is made of a shape memory alloy having a predetermined shape when the temperature is higher than a predetermined temperature, and the engagement state between the shield case 2 and the holding member 14a is set to a predetermined state when the temperature is higher than the predetermined temperature.
[Selection] Figure 1

Description

  The present invention relates to a circuit board device in which an electronic component disposed on a circuit board is covered with a shield case.

Conventionally, electronic components are mounted on circuit boards constituting high-frequency radios and portable communication devices, and some of them handle high frequencies. Then, a circuit board is used to shield the electronic component from the outside so as to shield the external component from being disturbed, or conversely to prevent the high frequency radiated from the electronic component from affecting other circuits. A shield case is installed on the top to cover the electronic components.
This shield case has a substantially casing shape with an open bottom, and is provided with metal plating on the outer surface or the shield case itself is made of a metal member in order to have conductivity on the surface.
The shield case covers the electronic components on the circuit board and is installed on the circuit board so as to be conductively joined to an earth site such as an earth pattern provided on the circuit board.

Conventionally, this shield case is joined to the ground pattern on the circuit board by solder joint, and the ground part on the circuit board and the shield case are conductively joined.
Alternatively, in order to facilitate installation of the shield case on the circuit board, a holding member such as a shield tab is provided on the circuit board, and the shield case is held by the shield tab and installed on the circuit board. In this case, since the shield tab is fixed to the ground pattern of the circuit board by soldering, and the shield case is engaged and held by sandwiching the partition plate of the shield case, the shield case is interposed via the shield tab. Then, electrical connection is made with the ground pattern on the circuit board (see, for example, Patent Document 1).
JP-A-6-90093

However, in the configuration in which the shield case is fixed on the circuit board by soldering, there is a problem that the shield case is not easily attached and detached and requires man-hours.
In addition, in the case where the shield case is held by the shield tab, since this shield tab is manufactured by a normal metal plate, the shield case has sufficient elasticity at the beginning of use, that is, the shield case holding force, that is, the shield case. The contact pressure is large, and the shielding effect by the shielding case can be sufficiently obtained. However, metal fatigue may occur or plastic deformation may occur due to long-term use, and the elasticity of the shield tab may be weakened and the holding force of the shield case may be reduced. In this case, the contact pressure of the shield tab against the shield case is weakened, the contact resistance is increased, and the shield effect of the shield case is deteriorated.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a circuit board device capable of easily attaching and detaching a shield case to a circuit board and improving the shielding effect of the shield case. is there.

In order to solve the above-described problems, a circuit board device of the present invention is formed in a circuit board on which electronic components are mounted and a substantially casing shape with an open bottom, and at least a surface portion is made of a conductive material. A shield case disposed on the circuit board so as to cover the electronic component; and a holding member that is installed on the circuit board and engages and holds the shield case on the circuit board. In the circuit board device, the holding member is made of a shape memory alloy having a predetermined shape when a predetermined temperature or higher is reached.
Therefore, when the holding member reaches or exceeds a predetermined temperature, the shield case is engaged and held in a predetermined state, and the contact pressure of the holding member with respect to the shield case becomes a desired high state, so that the holding member can reliably hold the shield case engaged. The shielding effect of the shielding case can be improved.

The shield case includes a partition plate that partitions the circuit block on the circuit board, and the holding member engages and holds the shield case with the partition plate interposed therebetween.
Accordingly, the shield case can be reliably engaged and held by the holding member, and the shield effect of the shield case can be further improved.

Further, the holding member is joined to a ground part of the circuit board, and the shield case is conductively joined to the ground part on the circuit board via the holding member.
Therefore, the ground connection of the shield case can be reliably performed with a simple structure, and the shield effect of the shield case can be further improved.

Further, the holding member is configured to bias the shield case toward the circuit board when the holding member is deformed so as to have the predetermined temperature or higher and to have the predetermined shape.
Therefore, the shielding effect of the shielding case can be improved, and the shielding effect of the shielding case can be further improved.

According to the circuit board device of the present invention, since the shield case is engaged and held by the holding member and installed on the circuit board, the shield case can be easily and reliably installed on the circuit board.
Furthermore, since the holding member is made of a shape memory alloy having a predetermined shape when the temperature is higher than a predetermined temperature, the shield case can be reliably engaged and held by the holding member, and on the circuit board by the shield case. Therefore, it is possible to suitably shield the electronic component, and to improve the shielding effect of the shielding case.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 is a schematic perspective view of a circuit board device of the present invention, FIG. 2 is a perspective view showing the shape of a shield tab as a holding member, FIG. 3 is a schematic sectional view of the shield tab in FIG. 1, and FIG. FIG. 5 is a schematic sectional view showing a second embodiment, and FIG. 5 is a schematic side view showing a third embodiment of the present invention.

  As shown in FIG. 1, the circuit board 1 (hereinafter referred to as the board 1) is provided with various circuit blocks 11 such as a transmission block and a reception block. It is delimited by a certain earth pattern 12. Wiring patterns such as wiring conductors constituting a predetermined circuit, electrode pads for mounting electronic components 13 and terminal electrodes for connecting to external circuits are formed on the surface of various circuit blocks 11. An electronic component 13 or the like is soldered on such a wiring pattern.

  In addition, a shield case 2 is disposed on the substrate 1 so as to cover the electronic components 13 and the like of the various circuit blocks 11. When high frequency noise is generated from a circuit formed on the substrate 1, the shield case 2 blocks the noise, or blocks high frequency noise jumping from an external circuit or an adjacent circuit. The stable operation of the predetermined circuit formed in the above is achieved.

  The shield case 2 is formed in a substantially housing shape having an open bottom so as to cover the electronic components 13 of the various circuit blocks 11. The shield case 2 is formed of a resin member, and metal plating is applied to the entire surface. On the upper and lower surfaces of the shield case 2, partition plates 21 for partitioning various circuit blocks 11 are provided so as to project in a substantially vertical direction. Although the partition plate on the lower surface side is not shown, its shape is provided at a position where it faces the ground pattern 12 of the substrate 1 when the shield case 2 is put on the substrate 1. The reason why the partition plate 21 is provided also on the upper surface side of the shield case 2 is that another substrate is turned over and attached to the upper surface side.

  Further, a shield tab 14a as a holding member that is engaged with the shield case 2 and holds the shield case 2 on the substrate 1 is fixed to a predetermined position on the ground pattern 12 of the substrate 1 by soldering. The shield tab 14a is manufactured by processing a single metal plate, and the structure thereof is configured by standing a sandwiching portion 16 from a planar bottom surface 15 as shown in FIG. Yes.

  Specifically, the shield tab 14a includes a bottom surface 15 that is fixed to the ground pattern 12 of the substrate 1 by solder, a sandwiching portion 16 that is erected by bending both sides of the bottom surface 15 upward at substantially right angles, A press-contact portion 18 formed by bending the vicinity of the upper end inwardly in a U-shape is provided. When the shield tab 14 a is processed and formed, it is formed in a cross-sectional shape as shown by a broken line in FIG. 3, and the gap width a of each press-contact portion 18 of the holding portion 16 is fitted into the holding portion 16. It is formed to be shorter than the thickness width b of the partition plate 21 of the shield case 2 to be joined.

  The shield tab 14a is made of a conductive shape memory alloy, has a normal elastic force, and has a shape (predetermined shape) as shown by a broken line in FIG. Shape). That is, the shield tab 14a is configured such that when the temperature exceeds a predetermined temperature, the gap width of the pressure contact portion 18 in the sandwiching portion 16 becomes a predetermined width a set to be shorter than the thickness width b of the partition plate 21 of the shield case 2. Has been.

Next, a method for manufacturing a circuit board device according to the present invention will be described.
First, the shield tab 14a as a holding member is mounted at a predetermined position on the ground pattern 12 of the substrate 1 shown in FIG. Then, the substrate 1 is reflowed and the bottom surface 15 (see FIG. 1) of the shield tab 14a is soldered to the ground pattern 12.

  Then, the shield case 2 is put on the substrate 1, and the partition plate 21 of the shield case 2 is fitted to the shield tab 14a. At this time, as indicated by a solid line in FIG. 3, the gap between the press contact portions 18 is expanded and the clamping portion 16 is elastically deformed, and the press contact portion 18 is pressed against the side surface of the partition plate 21 by the elastic force of the shield tab 14a. To do. Therefore, the partition plate 21 is clamped by the clamping part 16 of the shield tab 14a, and the shield case 2 and the shield tab 14a are securely connected electrically and mechanically. With this configuration, the shield case 2 is engaged and held by the shield tab 14a and is electrically connected to the ground pattern 12 on the substrate 1 via the shield tab 14a.

Next, the operation of the circuit board device according to the present invention will be described.
First, since the electronic components 13 mounted on the various circuit blocks 11 of the substrate 1 covered with the shield case 2 generate heat when power is supplied, the temperature in the various circuit blocks 11 rises.
When the temperature of the shield tab 14a itself rises to a predetermined temperature or more due to heat generation of the electronic component 13, etc., the shield tab 14a has a shape at the time of processing formation, that is, the gap width in the clamping portion 16 is the partition plate 21. It is deformed so as to have a predetermined width a shorter than the thickness width b. However, since the partition plate 21 is fitted to the pressure contact portion 18, the deformation of the shield tab 14 a is suppressed in a state where the pressure contact portion 18 is in contact with the side surface of the partition plate 21, and the pressure contact portion 18 is separated from the pressure contact portion 18. The plate 21 is pressed against the side surface. Therefore, the holding force of the partition plate 21 of the shield case 2 by the shield tab 14a can be increased, and the contact pressure to the shield case 2 at the press contact portion 18 of the shield tab 14a can also be increased.
Therefore, the shield tab 14a and the shield case 2 can be securely connected to each other, and the shield effect can be improved by the shield case 2.

  Even when the elastic force of the shield tab 14a is reduced due to metal fatigue or plastic deformation in the shield tab 14a, the heat generation of the electronic component 13 on the substrate 1 is used to make the temperature higher than a predetermined temperature. When the shield tab 14a is deformed to have a predetermined shape, a large clamping force can be generated in the shield tab 14a, and the pressure contact portion 18 of the shield tab 14a contacts the partition plate 21 of the shield case 2 The pressure can also be increased.

Next, a second embodiment of the present invention will be described.
In the second embodiment, the shape of the shield tab 14a and the configuration in which the partition plate 21 of the shield case 2 is sandwiched by the sandwiching portion 16 of the shield tab 14a are the same as those of the first embodiment described above, but are shown in FIG. As described above, the second embodiment is different from the first embodiment in that a recess 22 is formed on the side surface of the partition plate 21 of the shield case 2.

Also in the present embodiment, the shield tab 14 a is processed and molded so that the gap width of the pressure contact portion 18 is shorter than the thickness width b of the partition plate 21, so that the partition plate 21 is fitted to the sandwiching portion 16. Then, the clamping part 16 is elastically deformed so as to be spread, and the partition plate 21 is clamped by this elastic force.
However, since the concave portion 22 is formed on the side surface of the sandwiching portion 16 that faces the press contact portion 18, the inclined portion 23 formed below the press contact portion 18 abuts on the step portion 24 of the recess 22 and the shield tab 14a. Due to the elastic force, the step portion 24 receives a stress in the obliquely downward direction from the inclined portion 23.
Therefore, the shield tab 14a abuts on the stepped portion 24 and sandwiches the partition plate 21, thereby engaging and holding the shield case 2 and urging it toward the substrate 1 side.

Also in the present embodiment, the shield tab 14a is formed of a shape memory alloy, and is configured to have a shape at the time of processing as shown by a broken line in FIG.
When the shield tab 14a is heated to a predetermined temperature or more due to heat generated by the electronic component 13 in the electronic block 11, the shield tab 14a tends to be deformed into a shape indicated by a broken line in FIG. While being in contact with the stepped portion 24, it is held by the shield tab 14 a and urged toward the substrate 1 side.
Therefore, even if metal fatigue or plastic deformation occurs in the shield tab 14a and the elasticity of the shield tab 14a is weakened, and the contact pressure to the partition plate 21 of the shield case 2 is reduced, the shield tab 14a is not attached to the electronic component 13. When the temperature rises above a predetermined temperature due to heat generation, etc., it is deformed so as to have a predetermined shape, so that the partition plate 21 of the shield case 2 is securely clamped and the shield case 2 is engaged and held as in the first embodiment. be able to.

In the present embodiment, since the shield tab 14a is configured to bias the shield case 2 toward the substrate 1, the generation of a gap between the shield case 2 and the substrate 1 can be suppressed, and various types of shield case 2 can be performed. The circuit block can be effectively shielded from the outside and other circuit blocks, and the shielding effect of the shield case 2 can be further improved.
As in the first embodiment, the shield tab 14a is joined to the ground pattern 12 by soldering or the like, and the shield case 2 is electrically connected to the ground pattern 12 on the substrate 1 via the shield tab 14a. Although configured, the shield case 2 may be configured to be directly joined to the ground pattern 12 on the substrate 1 by using a force for urging the shield case 2 of the shield tab 14a toward the substrate 1 side.

  In the present embodiment, the recess 22 is provided on the side surface of the partition plate 21 of the shield case 2 and the shield tab 14a abuts the stepped portion 24 so that the shield tab 14a biases the shield case 2 toward the substrate side. However, the present invention is not limited to such a configuration, and any configuration may be used as long as the shield tab 14a engages and holds the shield case 2 and urges the shield case 2 toward the substrate 1 side.

Next, a third embodiment of the present invention will be described.
In the present embodiment, as shown in FIG. 5, a shield tab 14 b that engages and holds the shield case 2 is disposed between the shield case 2 and the substrate 1. Specifically, the shield tab 14b is disposed in the groove 25 formed on the lower end side of the partition plate 21, the lower end of the shield tab 14b is fixed to the ground pattern 12 on the substrate 1 by soldering or the like, and the upper end is the partition plate. 21 is engaged with and fixed to the upper surface of the groove portion 25. The shield case 2 is electrically connected to the ground pattern 12 on the substrate 1 through the shield tab 14b.
And the shield tab 14b is processed and shape | molded with the shape memory alloy, and when it becomes more than predetermined temperature, it is comprised so that it may shrink | contract in the up-down direction.

When the shield tab 14b reaches a predetermined temperature or more due to heat generated by the electronic component 13, the shield tab 14b contracts in the vertical direction and urges the shield case 2 toward the substrate 1 side. The shield tab 14b is configured such that the upper and lower ends do not separate from the partition plate or the ground pattern 12 when contracted.
Therefore, in the present embodiment, the shield tab 14b is formed by shape memory and is configured to contract in the vertical direction when the temperature is equal to or higher than a predetermined temperature. Therefore, when the shield tab 14b is equal to or higher than the predetermined temperature, the shield case 2 Receives a biasing force toward the substrate 1 from the shield tab 14b, and can effectively shield various circuit blocks from the outside and other circuit blocks by the shield case 2. It can be improved further.
The shield case 2 may be directly joined to the ground pattern 12 on the substrate 1, and in this case, the conductive joining of the shield case 2 to the ground pattern 12 is preferably performed by the biasing force of the shield tab 14b. be able to.

  In the above-described embodiment, the shield tab 14b is configured to contract in the vertical direction when the temperature exceeds a predetermined temperature. However, the shield tab 14b may be configured to extend in the vertical direction. In this case, since the shield tab 14b extends in the vertical direction when the temperature exceeds a predetermined temperature, the joint between the upper end portion of the shield tab 14b and the shield case 2 and the joint between the seal and the lower end portion of the tab 14b and the ground pattern 12 are further strengthened. Is done. Therefore, the conductive bonding of the shield case 2 to the ground pattern 12 is more reliably and effectively performed, and the shield effect of the shield case 2 can be improved. In this case, a holding member for holding the shield case 2 on the substrate 1 is separately provided in order to prevent a gap from being generated between the shield case 2 and the substrate 1.

This is the end of the description of the circuit board device of the present invention. However, the present invention is not limited to the above-described embodiment, and can be changed without departing from the present invention.
For example, in the first and second embodiments, the partition plate 21 of the shield case 2 is sandwiched by the sandwiching portion 16 of the shield tab 14a. However, even if the shield tab 14a does not sandwich the partition plate 21, the partition plate 21 The shield case 2 may be held by being engaged with the shield tab 2 and when the shield tab 14a reaches a predetermined temperature or higher, the contact of the shield tab 14a with the shield case 2 may be in a predetermined state.
The shield case 2 is made of a resin member and has a surface plated with metal. However, at least the surface portion may be made of a conductive material. For example, the shield case 2 itself is made of aluminum or the like. You may make it form with a metal member.

1 is a schematic perspective view of a circuit board device according to a first embodiment of the present invention. It is a schematic perspective view which shows the shape of the shield tab concerning 1st Embodiment of this invention. It is a schematic sectional drawing which shows the holding structure of the shield case concerning 1st Embodiment of this invention. It is a schematic sectional drawing which shows the holding structure of the shield case concerning 2nd Embodiment of this invention. It is a schematic side view which shows the holding structure of the shield case concerning 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Circuit board, 2 Shield case, 11 Circuit block, 12 Ground pattern, 13 Electronic component, 14a, 14b Shield tab, 15 Bottom face, 16 Clamping part, 18 Pressure contact part, 21 Partition plate, 22 Recessed part, 23 Inclined part, 24 Step Part, 25 groove part

Claims (4)

A circuit board on which electronic components are mounted;
A shield case formed on the circuit board so as to cover at least the surface part, which is formed of a conductive material at least at the surface part, and is formed in a substantially casing shape with an open bottom surface;
A circuit board device comprising: a holding member that is installed on the circuit board and engages and holds the shield case on the circuit board.
The holding member is made of a shape memory alloy that has a predetermined shape when the temperature exceeds a predetermined temperature.
A circuit board device. The shield case has a partition plate that partitions the circuit block on the circuit board;
The holding member engages and holds the shield case with the partition plate interposed therebetween.
The circuit board device according to claim 1. The holding member is bonded to the ground portion of the circuit board,
The shield case is conductively joined to a ground portion on the circuit board via the holding member.
The circuit board device according to claim 1, wherein the circuit board device is a circuit board device. The holding member is configured to urge the shield case toward the circuit board when the holding member is deformed so as to have the predetermined temperature or higher and to have the predetermined shape.
4. The circuit board device according to claim 1, wherein the circuit board device is a circuit board device.

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