JP2012019101A - Surface-mounted electronic circuit module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive surface-mounted electronic circuit module which has excellent flatness to a motherboard and is less likely to cause mounting failure.SOLUTION: An electronic circuit module 1 is a module article which is surface-mounted on a motherboard 7 for use. The electronic circuit module 1 mainly comprises: a circuit board 2 on which electronic components 4 are mounted; and a shield case 3 formed by folding a metal plate into a box shape. A pair of attachment legs 31 of the shield case 3 are inserted in and soldered to an attachment recess 21 formed on each of the four corners of the circuit board 2 so that the shield case 3 is attached to the circuit board 2 while covering the electronic components 4 or the like. The pairs of attachment legs 31 project downward from adjacent side plates 33 on the corners of the shield case 3, and both of the attachment legs 31 are adjacently arranged at right angles with a minute gap G2 of 0.1-0.5 mm formed therebetween. The gap G2 causes excess molten solder and flux to flow by capillarity.

Description

  The present invention relates to an electronic circuit module that is used by being surface-mounted on a motherboard such as a wireless communication device, and more particularly, a surface mounting in which a shield case that covers electronic components and the like is attached to a circuit board placed on the motherboard. Type electronic circuit module.

  In general, this type of surface-mounted electronic circuit module includes a rectangular circuit board on which a high-frequency circuit including electronic components is disposed, and a shield formed in a box shape that bends a metal plate to cover the electronic components and the like. And a case. In the shield case, the side plate portions are suspended from the four sides of the rectangular top plate portion toward the circuit board, and mounting legs project at appropriate positions at the lower ends of at least the plurality of side plate portions. When attaching the shield case to the circuit board, each mounting leg is inserted into the mounting recess of the circuit board, and the lower end of each side plate part is abutted against the upper surface of the circuit board, so that the upper surface of the circuit board is electromagnetically Cover the area that needs to be shielded with a shield case. The circuit board mounting recess is a through hole having an inner surface electrode or a side through hole having a side electrode. Apply cream solder in the vicinity of the upper edge of these mounting recesses, insert the corresponding mounting legs of the shield case into each mounting recess, and then heat in a reflow oven to install the corresponding mounting legs. Soldered into the recess. Thereby, the electronic circuit module which fixed the shield case to the circuit board is obtained. In addition, a plurality of land-like terminal portions are disposed on the lower surface of the circuit board. With these land-like terminal portions aligned with the corresponding land portions on the motherboard side, an electronic circuit module (with a shield case) is provided. Surface mount the circuit board on the motherboard. When the electronic circuit module is surface-mounted in this way, the shield case is electrically connected to the ground circuit on the motherboard side via the inner surface electrode and the side electrode, so that the electronic components on the circuit board are electromagnetically shielded. It becomes a state.

  By the way, in the general surface mount electronic circuit module described above, when soldering the mounting legs of the shield case to the mounting recesses of the circuit board, molten solder or flux flows out from the mounting recesses to the lower surface side. In this case, since the convex portion is formed on the lower surface of the circuit board, the flatness is deteriorated. As a result, the electronic circuit module may be tilted on the motherboard during surface mounting, and a part of the circuit board may be lifted up. When such floating occurs, the land-like terminal part of the circuit board and the land part on the motherboard side Since the reliability of the connection is reduced, mounting defects are likely to occur.

  Therefore, conventionally, by forming a fine slit in the mounting leg of the shield case in advance, excess molten solder or flux that is a concern during reflow in the mounting recess of the circuit board can easily enter the slit by capillary action. Thus, a surface mount electronic circuit module has been proposed in which the phenomenon that molten solder or flux flows out to the lower surface side of the circuit board is less likely to occur (see, for example, Patent Document 1). In such a conventional electronic circuit module, a narrow slit capable of causing capillary action is formed in the mounting leg of the shield case, and this slit is communicated with a hole or notch in the side plate portion. Therefore, when soldering the shield case mounting legs to the circuit board mounting recesses, even if excessive molten solder or flux flows into the mounting recesses, excess molten solder or flux is attached by capillary action. It can be introduced to the slits in the legs and led to the holes and notches in the side plates.

JP 2005-38929 A

  As in the conventional example disclosed in Patent Document 1, a slit having a narrow groove width is formed on the mounting leg of a shield case made of a thin metal plate (for example, around 0.2 mm) to the extent that capillary action can occur. In this case, since there is a limit to the reduction of the slit width in the punching using a mold, a method of forming a fine slit on the mounting leg using a cutting tool having a very thin blade is employed. However, if the mounting legs of the shield case are reduced with the miniaturization of the electronic circuit module, the work of forming such slits on the mounting legs is likely to be complicated, and a cutting tool with a very thin blade is difficult to endure. Therefore, the cutting tool has to be changed frequently. Therefore, the conventional technique of forming fine slits in the mounting legs of the shield case inevitably increases the unit price of the shield case and increases the cost of the electronic circuit module.

  The present invention has been made in view of the actual situation of the prior art, and an object of the present invention is to provide a surface-mounting type electronic circuit module having good flatness with respect to a mother board and less likely to cause mounting defects at a low cost.

  To achieve the above object, the present invention comprises a rectangular circuit board on which electronic components are mounted, and a shield case formed in a box shape that covers the electronic components by bending a metal plate, The shield case has four side plate portions that respectively hang down from the four sides of the rectangular top plate portion to the circuit board side, and mounting legs that protrude from the side plate portions and are inserted into the mounting recesses of the circuit board, In the surface mount type electronic circuit module in which the shield case is attached to the circuit board by soldering the attachment legs to the attachment recesses, from the corners of the pair of side plate portions adjacent to the shield case, respectively. The mounting legs are protruded and the pair of mounting legs are adjacent to each other at a substantially right angle with a gap of 0.1 to 0.5 mm so that both mounting legs are inserted into the common mounting recess. It was constructed to so that.

  In the surface mount electronic circuit module configured as described above, a pair of mounting legs provided at the corners of the shield case and inserted into a common mounting recess have a fine gap (0.1 to 0.5 mm). When the shield case is attached to the circuit board, even if more molten solder or flux than necessary flows into the mounting recess, the excess molten solder or flux is capillaryed. It is possible to flow into this gap due to a phenomenon. In addition, since this gap communicates with the gap between the side plate portions adjacent to each other at a substantially right angle, molten solder and flux can be sufficiently accumulated in both the gaps. Therefore, it is difficult for molten solder or flux to flow out to the lower surface side of the circuit board when the shield case is attached, and the flatness with respect to the motherboard is improved. In addition, the gap between the mounting legs adjacent to each other at a substantially right angle can be formed by a bending process when forming the shield case, and a cutting process using a special tool is not necessary, so that the unit price of the shield case can be suppressed. .

  In the above configuration, when the shield case makes the inner wall surface of one side plate portion and the side end surface of the other side plate portion face each other at a corner portion between a pair of adjacent side plate portions, the shield case projects from the both side plate portions, respectively. Because the inner wall surface of one mounting leg and the side end surface of the other mounting leg that are adjacent to each other at a substantially right angle can be opposed to each other with a predetermined gap, the depth of this gap is only the thickness of the shield case. As a result, it becomes easy to allow molten solder or flux to flow in due to a capillary phenomenon.

  According to the surface mount electronic circuit module of the present invention, the pair of mounting legs provided at the corners of the shield case and inserted into the common mounting recess have a fine gap (a gap of 0.1 to 0.5 mm). Therefore, even if more molten solder or flux than necessary flows into the mounting recess when the shield case is attached to the circuit board, excess molten solder or flux is capillarized. It can flow into this gap. Further, since this gap communicates with the gap between the side plate portions adjacent to each other at a substantially right angle, molten solder and flux can be sufficiently accumulated in both the gaps. Therefore, it is difficult to cause a problem that molten solder or flux flows out to the lower surface side of the circuit board when the shield case is attached. In addition, the gap between the mounting legs adjacent to each other at a substantially right angle can be easily formed by bending when forming the shield case, and cutting with a special tool is not required, thus reducing the unit price of the shield case. Can do. Therefore, an electronic circuit module having good flatness with respect to the mother board and less likely to cause mounting failure can be manufactured at low cost.

1 is an external view of a surface mount electronic circuit module according to a first embodiment of the present invention. It is a disassembled perspective view of the electronic circuit module shown in FIG. It is the principal part enlarged view which looked at the one corner part of the electronic circuit module shown in FIG. 1 from the downward direction. It is a principal part enlarged view which shows the one corner part of the shield case shown in FIG. It is an expanded view of the shield case shown in FIG. It is a side view which shows the state which surface-mounted the electronic circuit module shown in FIG. 1 on the motherboard. It is a disassembled perspective view of the electronic circuit module which concerns on the example of 2nd Embodiment of this invention. It is the principal part enlarged view which looked at the one corner part of the shield case shown in FIG. 7 from the downward direction.

  Hereinafter, a surface mount electronic circuit module according to an embodiment of the present invention will be described. First, a first embodiment will be described with reference to FIGS. The electronic circuit module 1 shown in these drawings is mainly configured by a rectangular circuit board 2 on which a high-frequency circuit including an electronic component 4 is disposed, and a shield case 3 formed by bending a metal plate into a box shape. Has been. Since a pair of mounting legs 31 of the shield case 3 are inserted and soldered into the side through holes 21 at the four corners of the circuit board 2 respectively, the circuit board 2 is covered with the shield case 3 covering the electronic component 4 and the like. Is attached. As shown in FIG. 6, the electronic circuit module 1 is used by being surface-mounted on a mother board 7 such as a wireless communication device. 1 and 6, solder in the side through hole 21 of the circuit board 2 is not shown.

  The circuit board 2 is obtained by dividing a large-sized board (not shown) along vertical and horizontal dividing grooves. In this large substrate, round holes are formed at the intersections of the vertical and horizontal dividing grooves, and electrodes are formed on the inner wall surface of each of the round holes, so that the four corners of the circuit board 2 obtained by division are rounded. The side through hole 21 has a size obtained by dividing the hole into four. The side through hole 21 is a mounting recess for inserting and soldering the mounting legs 31 forming a pair of the shield case 3, and the electrode is divided into four parts on the curved wall surface of the side through hole 21. A side electrode 21a is provided. An electronic component 4 connected to a wiring pattern (not shown) is mounted on the upper surface of the circuit board 2, and land terminals (not shown) derived from the wiring pattern are arranged on the lower surface of the circuit board 2. ing. These land-like terminal portions are arranged corresponding to land portions (not shown) provided on the mother board 7.

  The shield case 3 includes a rectangular top plate portion 32, four side plate portions 33 hanging from the four sides of the top plate portion 32, a lower end of one side portion of each side plate portion 33, and a lower end of the other side portion, respectively. A mounting leg 31 protruding downward is provided. The shield case 3 is formed into a box shape with its lower surface open as shown in FIG. 2 by bending a developed metal plate as shown in FIG. Of the four side plate portions 33, the two side plate portions 33a hanging from the short side of the top plate portion 32 are connected to the remaining two side plate portions 33b hanging from the long side of the top plate portion 32 with a fine gap G1 ( (See FIG. 4). That is, in the shield case 3, the inner wall surface of one side plate portion 33a and the side end surface of the other side plate portion 33b are opposed to each other at the corner where the side plate portions 33 (side plate portion 33a and side plate portion 33b) are adjacent to each other. . Therefore, the pair of mounting legs 31 that protrude from the side plate portion 33a and the side plate portion 33b and are adjacent to each other at a substantially right angle have a fine gap G2 between the inner wall surface of one mounting leg 31a and the side end surface of the other mounting leg 31b (see FIG. 3)).

  Since the size of the gap G2 is set to 0.1 to 0.5 mm (preferably 0.1 to 0.3 mm), when the shield case 3 is attached to the circuit board 2 as described later, the side through hole The molten solder or flux in 21 can be caused to flow into the gap G2 by capillary action. The gap G2 communicates with the gap G1 between the side plate portions 33 (side plate portion 33a and side plate portion 33b) adjacent to each other at a substantially right angle, and both the gaps G1, G2 have the same dimensions. A sufficient amount of molten solder and flux can be stored in G2.

  When attaching the shield case 3 to the circuit board 2, first, a region that needs to be electromagnetically shielded on the upper surface of the circuit board 2 is covered with the shield case 3, and side through holes at four corners of the circuit board 2 ( A pair of mounting legs 31 of the shield case 3 are inserted into the mounting recesses 21, and the lower ends of the side plate portions 33 are brought into contact with the upper surface of the circuit board 2. In the vicinity of the upper edge of each side through hole 21, cream solder (not shown) is applied in advance so as to overlap the upper end portion of the side electrode 21 a, so a pair of mounting legs 31 are inserted into each side through hole 21 one by one. After the shield case 3 is mounted on the circuit board 2 and heated in a reflow furnace, the mounting legs 31 and the corresponding side electrodes 21a of the side through holes 21 are electrically and soldered by the solder 5 as shown in FIG. Mechanically connected. Thereby, the shield case 3 is fixed to the circuit board 2, and the electronic circuit module 1 as shown in FIG. 1 is obtained.

  As shown in FIG. 6, the electronic circuit module 1 configured as described above has the land-like terminal portions arranged on the lower surface of the circuit board 2 aligned with the corresponding land portions of the mother board 7. Surface mounted on the mother board 7. When the electronic circuit module 1 is thus surface-mounted, the shield case 3 is electrically connected to the ground circuit on the motherboard 7 side via the side electrode 21a of the side through hole 21, so that the electronic component 4 on the circuit board 2 is provided. Etc. are electromagnetically shielded.

  As described above, in the surface-mount type electronic circuit module 1 according to the present embodiment, the pair of mounting legs 31 that are respectively inserted into the common side through holes 21 are provided at the four corners of the shield case 3. Since the gap G2 between the legs 31 is set to 0.1 to 0.5 mm (preferably 0.1 to 0.3 mm), it is more than necessary in the side through hole 21 when the shield case 3 is attached to the circuit board 2. Even when the molten solder or flux flows in, excess molten solder or flux can flow into the gap G2 by capillary action. Further, since the gap G2 communicates with the gap G1 between the side plate portions 33 adjacent to each other at a substantially right angle, molten solder and flux can be sufficiently accumulated in both the gaps G1 and G2. Therefore, it is difficult for molten solder or flux to flow out to the lower surface side of the circuit board 2 when the shield case 3 is attached, and the flatness with respect to the mother board 7 is improved. Moreover, the gap G2 between the mounting legs 31 adjacent to each other at a substantially right angle can be easily formed by a bending process when forming the shield case 3 in the same manner as the gap G1 between the side plates 33 adjacent at a substantially right angle. Since the cutting process using a tool is unnecessary, the unit price of the shield case 3 can be suppressed. Therefore, the electronic circuit module 1 having good flatness with respect to the mother board 7 and less likely to cause mounting failure can be manufactured at low cost.

  Further, in the electronic circuit module 1 according to the present embodiment, the shield case 3 includes the inner wall surface of the one side plate portion 33a and the other side plate at the corners adjacent to each other between the side plate portions 33 (side plate portion 33a and side plate portion 33b). Since the side end surface of the portion 33b is opposed to each other with a gap G1, the inner wall surface of one mounting leg 31a and the other mounting leg 31b that protrude from both side plate portions 33a and 33b and are adjacent to each other at a substantially right angle are provided. The side end faces the gap G2 having the same dimensions as the gap G1. Therefore, as shown in FIG. 3, the depth of the gap G2 (same for the gap G1) can be secured by the plate thickness dimension of the shield case 3, and it is easy to allow molten solder or flux to flow in by capillary action. .

  In the above-described embodiment, the case where the paired mounting legs 31 are inserted into the side through holes 21 of the circuit board 2 and soldered is described, but the circuit board 2 is used as a mounting recess for the mounting legs 31. Alternatively, a through hole having a round hole shape may be provided, and a pair of mounting legs 31 may be soldered to the inner surface electrode of the through hole.

  FIG. 7 is an exploded perspective view of the electronic circuit module according to the second embodiment of the present invention, and FIG. 8 is an enlarged view of a main part when one corner of the shield case shown in FIG. 7 is viewed from below. Portions corresponding to FIGS. 1 to 6 used in the description of the first embodiment are given the same reference numerals.

  As in the electronic circuit module 10 of the second embodiment shown in FIGS. 7 and 8, the shield case 3 has one side plate portion 33a at the adjacent corner of the side plate portions 33 (side plate portion 33a and side plate portion 33b). Even when the side end surface of the other side plate portion 33b and the side end surface of the other side plate portion 33b are arranged like the inclined surface of the V-groove, the mounting legs 31a, 31b protruding from the both side plate portions 33a, 33b are connected to each other with a predetermined gap G3. And can be inserted into a common side through hole (mounting recess) 21 adjacent to each other at a substantially right angle. Also in the second embodiment, since one side plate portion 33a and the other side plate portion 33b are adjacent to each other at a substantially right angle with a gap having the same dimensions as the gap G3 at the corner of the shield case 3. When the shield case 3 is attached to the circuit board 2, excess molten solder or flux can be caused to flow into these gaps G3 and the like by capillary action.

  However, in the case of the electronic circuit module 10 provided with such a shield case 3, the side end surface of one of the adjacent mounting legs 31a and the side end surface of the other mounting leg 31b are outwardly widened. Therefore, although a gap G3 that is likely to cause capillary action can be provided between the inner edge parts closest to each other on both side end faces, the gap becomes too wide at locations other than the inner edge parts on both side end faces, so that capillary action occurs. Is less likely to occur. Therefore, when compared with the electronic circuit module 1 of the first embodiment example and the second embodiment example, the first embodiment example can more sufficiently secure the inflow amount of molten solder or flux.

1,10 Electronic circuit module 2 Circuit board 3 Shield case 4 Electronic component 5 Solder 7 Motherboard 21 Side through hole (mounting recess)
21a Side electrode 31, 31a, 31b Mounting leg 32 Top plate part 33, 33a, 33b Side plate part G2, G3 Gap

Claims (2)

A square circuit board on which electronic components are mounted, and a shield case formed in a box shape that covers the electronic components by bending a metal plate, each of the shield cases from four sides of the square top plate portion. Four side plate portions depending on the circuit board side, and mounting legs protruding from the side plate portions and inserted into the mounting recesses of the circuit board, and soldering the mounting legs to the mounting recesses In the surface-mount type electronic circuit module in which the shield case is attached to the circuit board,
The mounting legs protrude from the corners of the pair of side plates adjacent to the shield case, and the pair of mounting legs are adjacent to each other at a substantially right angle with a gap of 0.1 to 0.5 mm. The surface mounting type electronic circuit module is characterized in that both mounting legs are inserted into the common mounting recess.   2. The shield case according to claim 1, wherein an inner wall surface of one side plate portion and a side end surface of the other side plate portion are opposed to each other at a corner portion between a pair of adjacent side plate portions. Surface mount electronic circuit module.

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