JP2004080375A - Electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic apparatus capable of keeping electric continuity by preventing occurrence of solder cracks caused between an integrated circuit and a printed circuit board due to an external stress. <P>SOLUTION: The electronic apparatus is characterized by including: the board; a first surface mount component surface-mounted at a prescribed position on one board side of the board; a frame member fitted to the board in a way of covering the first surface mount component at a prescribed interval; and a second surface mount component surface-mounted on a side opposite to the side on which the first surface mount component is surface-mounted and in a region wherein the frame member is located when viewed from a normal direction of the board. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electronic device having a surface mounted component mounted on a substrate, and more particularly to an electronic device capable of preventing the occurrence of solder cracks between the surface mounted component and the substrate due to external stress.
[0002]
[Prior art]
In recent years, integrated circuits of mobile phone terminals have been fused with BGA (ball grid array) type solder balls, such as CSP (chip size package), as the mobile phone terminals have become smaller, thinner and more densely packaged. There are an increasing number of leadless and leadless bonded products such as QFNs (quad flat non-lead packages).
[0003]
[Problems to be solved by the invention]
However, these packages have a problem that when stress is generated between the substrate and the package due to leadless, the stress cannot be relieved at the soldering pad portion, causing a solder crack and interrupting conduction.
[0004]
This problem will be described with reference to the accompanying drawings. As shown in FIG. 5, the IC package 102 on the front surface side as viewed from the normal direction of the substrate 101 (perpendicular to the plate surface) is entirely or completely removed from the surface-mounted region. When the IC package 103 on the back side is surface-mounted so that the portion protrudes, or between two regions where the IC package 102 on the front side is surface-mounted when viewed from the normal direction of the substrate 101 as shown in FIG. When the IC package 103 on the back side is surface-mounted, if a strong pressing force of the key button 105 acts or a drop impact occurs, when a stress is generated between the substrate 101 and the IC package 103, In some cases, the stress could not be relieved at the soldering pad portion 103a, causing a solder crack and breaking the conduction (see FIGS. 6 and 8).
[0005]
Further, in the case of single-sided mounting of the substrate, the IC package is covered with a predetermined interval and reinforced by a metal frame (for example, 104 in FIG. 5 and 104 in FIG. 6) which also serves as a noise shield. In some cases, the occurrence of solder cracks is prevented and conduction is maintained. When such a frame is mounted on a board, it is necessary to create a through hole for positioning the shield on the board. However, if such a frame is applied to the case of mounting on both sides of the board, the through-holes of the board for mounting the frame on the back side of the board and the conductor pattern corresponding to the IC package mounted on the front side of the board may be in conflict. Therefore, there is a problem in that it is difficult to attach a shield to a substrate on which high-density mounting is performed, in terms of design.
[0006]
An object of the present invention is to provide an electronic device capable of preventing occurrence of solder cracks between an integrated circuit and a printed circuit board due to external stress and maintaining conduction.
[0007]
[Means for Solving the Problems]
In a first aspect of the present invention, in an electronic device, a substrate, a first surface-mounted component surface-mounted at a predetermined position on one plate surface of the substrate, and the first surface-mounted component A frame member attached to the substrate so as to cover at a predetermined interval, and a surface opposite to a surface on which the first surface-mounted component is surface-mounted, viewed from a normal direction of the substrate. And a second surface-mounted component that is surface-mounted in a region where the frame member is arranged.
[0008]
According to this configuration, the rigidity of the frame member that covers the first surface-mounted component causes the substrate to bend in a region outside the region surrounded by the frame member, so that the connection pad portion of the second surface-mounted component The applied stress can be suppressed. Further, if the second surface-mounted component is surface-mounted in a region where the first surface-mounted component is disposed when viewed from the normal direction of the substrate, the stress applied to the connection pad portion of the second surface-mounted component can be reduced. Can be further suppressed.
[0009]
According to a second aspect of the present invention, in the electronic device, in the electronic device, a first substrate, a first surface-mounted component surface-mounted at a predetermined position on one plate surface of the first substrate, and A frame member attached to the first substrate so as to cover the first surface-mounted component at a predetermined interval, and a surface opposite to a surface on which the first surface-mounted component is surface-mounted, A second surface-mounted component that is surface-mounted in a region where the frame member is disposed when viewed from a normal direction of the first substrate, and disposed on a surface of the substrate on which the frame member is mounted; One or more key buttons, and a second substrate that is disposed at least between the frame member and the key buttons and receives a pressing force of the key buttons when the key buttons are pressed. Features.
[0010]
According to this configuration, even when the pressing force of the key button is too strong and the second substrate is bent and the pressing force is applied to the frame member, the rigidity of the frame member causes the substrate to move in the region surrounded by the frame member. Since there is almost no bending, it is possible to suppress the stress applied not only to the first surface-mounted component but also to the connection pad portion of the second surface-mounted component.
[0011]
According to a third aspect of the present invention, in an electronic device, a substrate having two or more cutouts and one or more surface mounts mounted on one or both surfaces of the substrate other than a line connecting the cutouts And components.
[0012]
According to this configuration, a region on the substrate where stress is likely to be applied (a line connecting the notches) can be known in advance.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an exploded perspective view schematically showing a configuration of an electronic device according to one embodiment of the present invention.
[0014]
This electronic device is used for finished products and intermediate products such as a mobile phone terminal, a telephone, a facsimile, a remote controller, a portable game machine, a keyboard (FIG. 1 relates to a mobile phone terminal), and a substrate 1 and a first surface mount. It has a component 2, a second surface mount component 3, and a frame member 4.
[0015]
The substrate 1 is a printed wiring board (PWB) such as a multilayer board capable of high-density mounting and high-density wiring, and an ALIVH (Any Layer Inner Via Hole) board. The substrate 1 has a first conductor pattern (not shown) for electrically connecting to the first surface-mounted component 2 at a predetermined position on one plate surface (front surface), and the other plate surface (not shown). A second conductor pattern (not shown) for electrically connecting to the second surface mount component 3 is provided at a predetermined position (on the back side of the region where the first conductor pattern is arranged) on the back surface. The substrate 1 has a plurality of through holes 1a for attaching the frame member 4 at predetermined positions outside a region where the first conductor pattern is arranged when viewed from the normal direction of the substrate 1, and the frame member 4 A third conductor pattern (not shown) for soldering is provided at a predetermined position on the plate surface that comes into contact with the end surface of the frame member 4 when attached to the through hole 1a. The end surfaces of the substrate 1 and the frame member 4 may be bonded with an adhesive other than the solder.
[0016]
The first surface mount component 2 includes a QFP (Quad Flat Package), an SOP (Small Outline Package), a TSOP (Thin SOP), a SOJ (Small Outline J-leaded package), a TCP (Tape Carrier package such as a Tape Carrier, etc.). Area array terminal type packages such as packages, BGA (Ball Grid Array), LGA (Land Grid Array Package), CSP (Chip Size Package), QFN (Quad Flat Non-Leaded Package), flip chip, etc. , IC, LSI and the like. The first surface-mounted component 2 is surface-mounted at a corresponding position on the first conductor pattern of the substrate 1 using a connection material such as solder, conductive paste, anisotropic conductive material, or resin.
[0017]
The second surface mount component 3 is a surface mount component such as a peripheral terminal type package or an area array terminal type package, and includes one or a plurality of device elements such as an IC and an LSI. The second surface-mounted component 3 is smaller than the outer shape of the frame member 4 when viewed from the normal direction of the substrate 1 (preferably, the same outer shape as the first surface-mounted component 2 or smaller), and It is surface-mounted at a corresponding position on the second conductor pattern of the printed circuit board 1 within the area of the frame member 4 when viewed from the direction. The second surface mount component 3 is electrically connected to the substrate 1 using a connection material such as solder, conductive paste, anisotropic conductive material, and resin.
[0018]
The frame member 4 is a frame-shaped member that reinforces the first surface-mounted component 2, and includes a plurality of protrusions 4a (corner portions in FIG. 1) inserted into the through-hole 1a at positions corresponding to the through-hole 1a of the substrate 1. 4). The protrusion 4a and the corresponding through hole 1a are joined by solder. The frame member 4 is mounted on the substrate 1 so as to cover (enclose) the surface in the thickness direction and the side end surface of the first surface mount component 2 at a distance. The frame member 4 may be made of metal (stainless steel) also serving as a noise shield. The surface of the frame member 4 is plated with solder, and the end surface of the frame portion and the third conductor pattern of the substrate 1 in contact with the end surface are as follows. Joined by solder.
[0019]
【Example】
First Embodiment A first embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a partial cross-sectional view schematically illustrating a configuration in which the electronic device according to the first embodiment of the present invention is applied to a mobile phone terminal.
[0020]
The first embodiment is an example in which the substrate 1 on which the first surface mount component 2, the second surface mount component 3, and the frame member 4 shown in FIG. 1 are mounted is applied to a mobile phone terminal. In the first embodiment, a BGA type CSP is used for the first surface mount component 2 and QFN is used for the second surface mount component 3.
[0021]
This mobile phone terminal is housed in the housing of the mobile phone terminal with the plate surface of the main board 1 on which the frame member 4 is attached facing the key operation side, and includes a key button 5, a front case 6, It has a key operation board 7 and a metal dome 8. The key button 5 is a button pressed from outside the front case 6. The front case 6 is a housing that houses the key buttons 5, the key operation board 7, the metal dome 8, and the like. The key operation board 7 is arranged between the main board 1 and the key buttons 5, receives the pressing force of the key buttons 5 when the key buttons 5 are pressed, and is connected to the board 1 via a connector or the like. The metal dome 8 transmits a pressing signal from the key button 5 to the key operation board 7.
[0022]
The operation of the first embodiment will be described with reference to the drawings. FIG. 3 is a partial cross-sectional view schematically showing a state in which a key button is pressed when the electronic device according to the first embodiment of the present invention is applied to a mobile phone terminal.
[0023]
According to the configuration of the mobile phone terminal according to the first embodiment, when the key button 5 is pressed in the direction of arrow A in FIG. 3, the metal dome 8 bends due to the load, and the metal dome 8 comes into contact with the key operation board 7 to transmit a signal. Tell When the pressing force of the key button 5 is very large, the key operation board 7 is bent by being pressed by the key button 5, the bottom surface of the bent key operation board 7 contacts the frame member 4, and the substrate 1 is moved through the frame member 4. When pressed, the substrate 1 bends in the direction of arrow B.
[0024]
In this case, due to the rigidity of the first surface mount component 2 and the frame member 4, bending occurs in a region outside the region where the frame member 4 is disposed on the substrate 1, and the frame member 4 on the substrate 1 is disposed. Bending is suppressed in the region. The second surface-mounted component 3 has a smaller outer shape than the first surface-mounted component 2 and the frame member 4 and is mounted in a region of the substrate 1 where the frame member 4 is arranged. Almost no stress is applied to the connection pad 3a of the mounted component 3.
[0025]
Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 4A is a partial plan view schematically showing the configuration of the electronic device according to Comparative Example 3. FIG. 4B is a partial plan view schematically illustrating the configuration of the electronic device according to the second embodiment of the present invention.
[0026]
In the second embodiment (see FIG. 4B), the substrate 1 is provided with a plurality of notches 9 and 10 for positioning on a boss (not shown) provided on the front case. In the vicinity of a line which is the shortest distance between the side end surface of the notch 9 and the side end surface of the notch 10, a line 11 in which stress is easily applied is generated. The surface mounting component 12 is not mounted on the line 11. The line 11 varies in line width depending on the material, thickness, size, weight, etc. of the substrate 1. For example, if the line 11 is applied to a mobile phone terminal, the line 11 has a width of about 3 mm from the shortest line. is there. In the second embodiment, both the single-sided mounting and the double-sided mounting are assumed.
[0027]
In the second embodiment, since stress is easily applied to the line 11 connecting the notch 9 and the notch 10 in the substrate 1, the surface mount component 12 is placed at a position on the line 11 as shown in FIG. The surface mounting component 12 is mounted at a position other than the line 11 as shown in FIG. 4B according to the second embodiment, avoiding mounting. According to such a configuration, when an external stress is applied to the device, the external stress is concentrated (guided) on the line 11 on the substrate 1 and is absorbed by the elastic force of the substrate 1. As a result, the stress applied to the connection pad portion (not shown) of the surface mount component 12 is suppressed, and the occurrence of solder cracks in the surface mount component 12 can be suppressed.
[0028]
【The invention's effect】
According to the present invention, the following effects can be obtained.
[0029]
A first effect of the present invention is that even if a key button is continuously pressed strongly, generation of a solder crack in an IC package can be suppressed.
[0030]
The reason is that the IC package mounted on the front surface side of the board is directly behind the IC package with a smaller external size mounted on the back side of the board, so the frame is surrounded by the rigidity of the frame covering the IC package on the front side. This is because the substrate is bent in a region outside the bent region, so that no stress is applied to the connection pad portion of the IC package on the back surface side.
[0031]
The second effect of the present invention is that the reinforcing frame of the IC package mounted on the back surface side of the substrate is not required, and the mounting area and the mass can be reduced.
[0032]
The reason is that there is a case where it is difficult to mount, for example, a through hole for positioning the shield on the substrate when mounting on both sides in the past (when a shield is attached to the back side IC package, a through hole for positioning must be created) Therefore, if there is an IC package on the front surface side, a through hole cannot be formed in the substrate). Further, since the occurrence of solder cracks can be suppressed as in the first effect, a reinforcing frame is not required. It is.
[0033]
The third effect of the present invention is that, by setting in advance lines on which stress is likely to be applied on the substrate and mounting the IC package at a position other than the lines, the stress applied to the connection pad portion of the IC package is suppressed, Generation of solder cracks in the IC package can be suppressed.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view schematically showing a configuration of an electronic device according to an embodiment of the present invention.
FIG. 2 is a partial cross-sectional view schematically illustrating a configuration in which the electronic device according to the first embodiment of the present invention is applied to a mobile phone terminal.
FIG. 3 is a partial cross-sectional view schematically illustrating a state in which a key button is pressed when the electronic apparatus according to the first embodiment of the present invention is applied to a mobile phone terminal.
FIG. 4A is a partial plan view schematically illustrating a configuration of an electronic device according to Comparative Example 3, and FIG. 4B is a plan view of an electronic device according to Example 2 of the present invention. It is the partial top view which showed the structure typically.
FIG. 5 is a partial cross-sectional view schematically showing a configuration in which the electronic device according to Comparative Example 1 of the present invention is applied to a mobile phone terminal.
FIG. 6 is a partial cross-sectional view schematically showing a state in which a key button is pressed when the electronic device according to Comparative Example 1 of the present invention is applied to a mobile phone terminal.
FIG. 7 is a partial cross-sectional view schematically showing a configuration in a case where an electronic device according to Comparative Example 2 of the present invention is applied to a mobile phone terminal.
FIG. 8 is a partial cross-sectional view schematically showing a state in which a key button is pressed when the electronic device according to Comparative Example 2 of the present invention is applied to a mobile phone terminal.
[Explanation of symbols]
1, 101 substrate 1a hole 2, 102 first surface mount component (IC package)
3,103 Second surface mount component (IC package)
3a, 103a Pad portion 4, 104 Frame member 4a Projection portion 5, 105 Key button 6, 106 Front case 7, 107 Key operation board 8, 108 Metal dome 9, 10 Notch portion 11, Line 12, Surface mounting component

Claims (8)

Board and
A first surface-mounted component that is surface-mounted at a predetermined position on one plate surface of the substrate,
A frame member attached to the substrate so as to cover the first surface mount component at a predetermined interval;
A second surface mount, which is a surface opposite to the surface on which the first surface mount component is surface-mounted, and which is surface-mounted in a region where the frame member is arranged when viewed from a normal direction of the substrate; Parts and
An electronic device comprising: 2. The electronic device according to claim 1, wherein the second surface-mounted component is surface-mounted in a region where the first surface-mounted component is arranged as viewed from a normal direction of the substrate. 3. The substrate has a plurality of through holes outside a region where the first surface mount component is surface mounted,
The frame member has a plurality of protrusions inserted into the through hole,
The electronic device according to claim 1, wherein the through hole and the projection are soldered. The substrate has a conductor pattern at a predetermined position on a plate surface that is in contact with an end surface of the frame member,
4. The electronic device according to claim 1, wherein an end face of the frame member and the conductor pattern are joined by soldering. 5. 5. The electronic device according to claim 1, wherein one or both of the first surface mount component and the second surface mount component are an area array terminal type package. 6. A first substrate;
A first surface-mounted component surface-mounted at a predetermined position on one plate surface of the first substrate;
A frame member attached to the first substrate so as to cover the first surface mount component at a predetermined interval;
A second surface, which is a surface opposite to the surface on which the first surface-mounted component is mounted, and which is surface-mounted in a region where the frame member is arranged when viewed from a normal direction of the first substrate; Surface mount components,
One or more key buttons arranged on the side of the substrate on which the frame member is attached;
A second substrate that is disposed at least between the frame member and the key button, and that receives a pressing force of the key button when the key button is pressed,
An electronic device comprising: A substrate having two or more notches;
One or more surface-mounted components that are surface-mounted on one or both sides of the board other than the line connecting the notches,
An electronic device comprising: The electronic device according to claim 1, wherein the electronic device is a mobile phone terminal.

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