1. Field of the Invention
The present invention relates to a circuit module. More particularly, the present invention relates to a circuit module including a case that is mounted so as to cover an electronic component mounted on a substrate.
2. Description of the Related Art
A circuit module of the related art includes a substrate, component lands provided on the substrate, an electronic component bonded to the component lands, case lands provided on the substrate, and a case bonded to the case lands so as to cover the electronic component.
In such a circuit module, the case is usually bonded to the case lands by heating and melting solder on the case lands in a reflow furnace. Therefore, when the width of the case lands is relatively large in order to provide a sufficient bonding strength of the case, the mounting position of the case is displaced. Accordingly, Japanese Unexamined Patent Application Publication No. 2004-186570 discloses a structure that attempts to prevent displacement of the mounting position of the case.
In the structure disclosed in Japanese Unexamined Patent Application Publication No. 2004-186570, as illustrated in
In the above-described structure, the shape of the case lands on the substrate must be optimized in accordance with the size and shape of the case. For this reason, the design must be changed for each circuit module. Further, the amount of solder during mounting is less at the narrow portions of the case lands of the case than at the wide portions. Therefore, the bonding strength between the case and the substrate is decreased. In addition, since the area of the case lands must be increased in order to increase the bonding strength, the overall size of the circuit module is increased.
In order to overcome the problems described above, preferred embodiments of the present invention provide a circuit module in which displacement of a case during mounting is prevented.
A circuit module according to a preferred embodiment of the present invention includes a substrate, a component land provided on the substrate, an electronic component bonded to the component land, a case land provided on the substrate, and a case bonded to the case land so as to cover the electronic component. The case includes a top plate and a leg that extends from a peripheral edge of the top plate in a direction substantially perpendicular to the top plate and that includes a groove in an end surface bonded to the case land.
Preferably, the groove communicates between an inside and an outside of a space defined by the top plate and the leg.
Preferably, the groove extends substantially parallel to a thickness direction of the leg.
In a preferred embodiment of the present invention, the groove allows solder, which is melted by being heated in a reflow furnace, to flow between both sides of the end surface of the leg. For this reason, unevenness in the amount of solder on both sides of the end surface of the leg is prevented, which significantly reduces the displacement amount.
Preferably, the case includes a plurality of the legs, the top plate is substantially rectangular, and the legs are substantially plate-shaped and extend from one side of the top plate, for example.
Preferably, the case includes a plurality of the legs, the top plate is substantially rectangular, and the legs are substantially plate-shaped and extend from corresponding sides of the top plate, for example. Since the moving directions of the legs are perpendicular or substantially perpendicular to one another in the case, the displacement amount of the case is further reduced.
Preferably, the top plate is substantially rectangular, and the leg is substantially plate-shaped and obliquely intersects two sides of the top plate that define a corresponding corner of the top plate. Accordingly, the displacement amount of the case is reduced.
Preferably, the case includes a plurality of the legs, and the end surfaces of the plurality of legs have different areas and respectively include the grooves. A width of the groove provided in the leg having the end surface with a larger area is greater than a width of the groove provided in the leg having the end surface with a smaller area. In this case, the width of the groove in the smaller end surface is small, and the width of the groove in the larger end surface is large. This allows solder to more smoothly flow while preventing a reduction of bonding strength.
Preferably, the leg includes a plurality of the grooves in the end surface, for example.
Preferably, a width of the groove closer to the center of the case land is greater than a width of the groove farther from the center of the case land. In this case, since the width of the groove closer to the center of the case land at which a greater amount of solder is provided has a large width, solder flows more smoothly.
In various preferred embodiments of the present invention, the groove is preferably provided in the end surface of the leg of the case that opposes the case land and is bonded to the case land. This groove allows solder, which is melted by being heated in the reflow furnace, to flow between both sides of the end surface of the leg. For this reason, unevenness in the amount of solder on both sides of the end surface of the leg is prevented so as to reduce the displacement amount.
The above and other features, elements, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention with reference to the attached drawings.
Preferred embodiments of the present invention will be described below with reference to the drawings.
The end surfaces 34 of the legs 33 of the case 30 preferably include the grooves 35. The grooves 35 allow a space defined by the top plate 31 and the legs 33, that is, a space where the case 30 covers the electronic components to communicate with the outside of the case 30.
The case 30 may be displaced by the following mechanism. That is, when the legs 33 of the case 30 are mounted on the case lands 22, the amount of solder often becomes uneven on the sides of the end surfaces of the legs 33, as illustrated in
In the first preferred embodiment, the grooves 35 of the end surfaces 34 of the legs 33 extend substantially parallel to the thickness direction of the legs 33, as illustrated in
In the first preferred embodiment, the case 30 preferably includes four legs 33 on long side surfaces, as illustrated in
Displacement of the case 30 is influenced by the dimensional accuracy during mounting, the bonding strength between the case 30 and the case lands 22, the material and weight of the case 30, the composition of the solder 23, the surface state of the substrate 11, and the area of the case lands 22. Therefore, the size of the grooves is preferably appropriately determined based on these factors.
Displacement of the case 30 after heating in the reflow furnace is influenced by the dimensional accuracy of the case 30, the positional accuracy during mounting, the material and weight of the case 30, the composition of the solder 23, the surface state of the substrate 11, and the shape of the case lands 22, for example. In contrast, the bonding strength between the case 30 and the case lands 22 after heating in the reflow furnace is influenced by the material and weight of the case 30, the composition of the solder 23, the surface state of the substrate 11, the shape of the case lands 22, and the size of the grooves 35, for example. Therefore, the size of the grooves 35 is preferably appropriately determined in consideration of these factors so as to minimize or prevent the displacement and to obtain a required bonding strength.
In the fifth preferred embodiment, the width of the grooves 35a of the smaller end surfaces 34a is preferably small, and the width of the grooves 35b of the larger end surfaces 34b is preferably large. By making the width of the grooves in the smaller end surfaces small, solder can more smoothly flow while not significantly reducing the bonding strength thereof.
In the sixth preferred embodiment, preferably, the case 30 includes legs 33 each including a plurality of grooves 35c and 35d on an end surface. The width of the groove 35c closer to the center of the corresponding case land 22 is greater than the width of the grooves 35d farther from the center of the case land 22. In this case, since the width of the groove closer to the center of the case land 22, where a large amount solder 23 is provided, is large, the solder 23 can flow more smoothly.
A circuit module in which the case of the first preferred embodiment was mounted on a substrate was produced, and displacement of the case was measured. That is, a case having a shape illustrated in the six-surface view of
Regarding the size variations in the Y-direction, that is, at the positions (1) and (2), the standard deviation of the circuit modules including the cases that included the grooved legs was reduced to about half the standard deviation of the circuit modules including the cases that included no grooved leg. In contrast, regarding the size variations in the X-direction, that is, at the position (3), the standard deviation of the circuit modules including the cases that included the grooved legs was equivalent to the standard deviation of the circuit modules including the cases that included no grooved legs. This is likely because the grooves are provided so that the solder flows in the Y-direction.
While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.
Number | Date | Country | Kind |
---|---|---|---|
2010-029063 | Feb 2010 | JP | national |
Number | Name | Date | Kind |
---|---|---|---|
4628412 | Nigorikawa | Dec 1986 | A |
4987278 | Tsutsumi | Jan 1991 | A |
4990880 | Albert | Feb 1991 | A |
5453017 | Belopolsky | Sep 1995 | A |
5792994 | Akahane | Aug 1998 | A |
6000968 | Hagiwara | Dec 1999 | A |
6080016 | Ho et al. | Jun 2000 | A |
6285272 | Boytor et al. | Sep 2001 | B1 |
6297967 | Davidson et al. | Oct 2001 | B1 |
6344609 | Nakano | Feb 2002 | B1 |
6353258 | Inoue et al. | Mar 2002 | B1 |
6488513 | Neidich et al. | Dec 2002 | B1 |
7095624 | Daoud et al. | Aug 2006 | B2 |
7859852 | Wetzel et al. | Dec 2010 | B2 |
7924571 | Tsubono | Apr 2011 | B2 |
20020139574 | Hosaka et al. | Oct 2002 | A1 |
20030132885 | Kuramoto et al. | Jul 2003 | A1 |
20030134530 | Yu-Feng | Jul 2003 | A1 |
20030203658 | Zhao et al. | Oct 2003 | A1 |
20040017267 | Kane et al. | Jan 2004 | A1 |
20060063432 | Chen | Mar 2006 | A1 |
20070096317 | Kiyohara | May 2007 | A1 |
20070221399 | Nishizawa et al. | Sep 2007 | A1 |
20080068816 | Han et al. | Mar 2008 | A1 |
20080174984 | Miyamoto et al. | Jul 2008 | A1 |
20090016039 | Imamura | Jan 2009 | A1 |
20100207255 | Fenoglio et al. | Aug 2010 | A1 |
20110090664 | Sumida et al. | Apr 2011 | A1 |
Number | Date | Country |
---|---|---|
2003-309397 | Oct 2003 | JP |
2008-182007 | Aug 2008 | JP |
2011-165685 | Aug 2011 | JP |
Number | Date | Country | |
---|---|---|---|
20110199744 A1 | Aug 2011 | US |