U.S. patent application number 13/431305 was filed with the patent office on 2012-07-19 for electronic device and fabrication method thereof.
This patent application is currently assigned to RENESAS ELECTRONICS CORPORATION. Invention is credited to Kenji UCHIDA.
Application Number | 20120180311 13/431305 |
Document ID | / |
Family ID | 43898286 |
Filed Date | 2012-07-19 |
United States Patent
Application |
20120180311 |
Kind Code |
A1 |
UCHIDA; Kenji |
July 19, 2012 |
ELECTRONIC DEVICE AND FABRICATION METHOD THEREOF
Abstract
Provided is an electronic device of high reliability having an
exposed functional portion. An electronic device 10 comprises an
electronic element 11 having an exposed functional portion 11a on a
first surface, a frame member 12 having a first penetration hole
12a, and a board 13 having a second penetration hole 13a. The frame
member 12 is provided on the first surface of the electronic
element 11 such that the first penetration hole 12a faces at least
a part of the functional portion 11a. The electronic element 11 is
mounted on the board 13 such that at least a part of the functional
portion 11a faces the second penetration hole 13a. The frame member
12 does not contact with the board 13.
Inventors: |
UCHIDA; Kenji; (Kanagawa,
JP) |
Assignee: |
RENESAS ELECTRONICS
CORPORATION
Kanagawa
JP
|
Family ID: |
43898286 |
Appl. No.: |
13/431305 |
Filed: |
March 27, 2012 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12911574 |
Oct 25, 2010 |
8169793 |
|
|
13431305 |
|
|
|
|
Current U.S.
Class: |
29/837 ;
29/832 |
Current CPC
Class: |
H01L 2224/97 20130101;
H01L 2924/181 20130101; H01L 2924/351 20130101; H01L 2924/1461
20130101; Y10T 29/4913 20150115; H01L 24/97 20130101; H01L
2224/16225 20130101; H01L 24/16 20130101; B81C 1/00261 20130101;
H01L 2224/97 20130101; H01L 27/14618 20130101; Y10T 29/49139
20150115; H01L 2924/351 20130101; H01L 21/561 20130101; H01L
2924/181 20130101; H01L 2224/81 20130101; H01L 2924/00 20130101;
H01L 2924/00 20130101; H01L 2924/1461 20130101; H01L 2924/00
20130101 |
Class at
Publication: |
29/837 ;
29/832 |
International
Class: |
H05K 3/32 20060101
H05K003/32; H05K 3/30 20060101 H05K003/30 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 26, 2009 |
JP |
2009-245655 |
Claims
1. A method for fabricating an electronic device comprising: making
a frame member on a surface of an electronic element having an
exposed functional portion on the surface such that the frame
member surrounds at least a part of the functional portion; and
mounting the electronic element on a board having a penetration
hole such that the penetration hole exposes the frame and the part
of the functional portion.
2. The method for fabricating an electronic device according to
claim 1, wherein the electronic element is mounted on the board
such that the frame member is inserted into the penetration hole in
the mounting the electronic element on a board.
3. The method for fabricating an electronic device according to
claim 1, wherein the making a frame member comprises: forming a
precursor film for a frame member on the electronic element; and
processing the precursor film for a frame member such that at least
a part of the functional portion is exposed.
4. The method for fabricating an electronic device according to
claim 1, wherein mounting the electronic element on a board further
comprises: attaching the electronic element and the board via an
electronic conductive member formed on the surface of the
electronic element; and providing an underfill resin around the
electronic conductive member and between the electronic element and
the board, wherein the underfill resin is blocked from reaching to
the electronic element by the frame member.
5. The method for fabricating an electronic device according to
claim 4, wherein mounting the electronic element on a board further
comprises: sandwiching the electronic element and the board between
a first sealing die and a second sealing die after the providing an
underfill resin; and providing a sealing resin in a apace formed by
the electronic element, the board and one of the first sealing die
and the second sealing die such that the sealing resin is blocked
from reaching to the electronic element by the frame member.
6. The method for fabricating an electronic device according to
claim 5, wherein a gap is formed between an outer surface of the
frame member and an internal surface of the penetration hole of the
board.
7. The method for fabricating an electronic device according to
claim 5, wherein a buffer sheet is provided between the electronic
element and one of the first sealing die and the second sealing
die.
8. The method for fabricating an electronic device according to
claim 1, wherein mounting the electronic element on a board further
comprises: attaching the electronic element and the board via an
electronic conductive member formed on the surface of the
electronic element; sandwiching the electronic element and the
board between a first sealing die and a second sealing die after
the providing an underfill resin; and providing a sealing resin in
a space formed by the electronic element, the board and one of the
first sealing die and the second sealing die such that the sealing
resin is blocked from reaching to the electronic element by the
frame member.
9. The method for fabricating an electronic device according to
claim 8, wherein the sealing resin is formed between an outer
surface of the frame member and an internal surface of the
penetration hole of the board.
10. The method for fabricating an electronic device according to
claim 1, wherein the frame member has a height of 0.03 mm or
more.
11. The method for fabricating an electronic device according to
claim 1, wherein the frame member is made of resin.
Description
REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of U.S. patent application
Ser. No. 12/911,574, filed Oct. 25, 2010, now published, based upon
and claims the benefit of priority of Japanese patent application
No. 2009-245655, filed on Oct. 26, 2009, the disclosure of which is
incorporated herein in its entirety by reference thereto, the
contents of all of which are incorporated herein by reference in
their entirety.
TECHNICAL FIELD
[0002] This invention relates to an electronic device having an
exposed functional portion and a fabrication method thereof.
BACKGROUND
[0003] An electronic device for converting an optical signal from
outside into an electric signal, for example, is provided with an
electronic element having a light receiving portion as a functional
portion. In a case where resin is present on an optical path of the
optical signal in such an electronic device, the optical signal is
attenuated. Besides that a black resin, which can adapt an
electronic device to a lead-free reflow conditions by improving a
humidity resistance of the electronic device, cannot be used on an
optical path of an optical signal. In addition, as for an
electronic device relating to an optical recording technology using
a blue light for the optical signal, when an epoxy resin is used on
an optical path, the epoxy resin on the optical path is degraded by
the blue light and light transmittance of the epoxy resin is
decreased. Thus some of such electronic devices are structured such
that no resin is provided on an optical path, that is, a light
receiving portion is exposed (Patent Document 1, for example). It
is expected that an electronic device having an exposed functional
portion can be applied to MEMS (Micro Electro-Mechanical Systems),
a device in which a moving part of a functional element
(electro-acoustic filter, for example) cannot be coated with resin,
solid image sensing element for a camera, and the like.
[0004] Patent Document 1 discloses a semiconductor device having a
protruding portion for preventing contamination of an exposed light
receiving element. As to the semiconductor device disclosed in
Patent Document 1, a semiconductor bare chip having a light
receiving portion is mounted on a circuit board by flip chip
attachment, a penetration hole is provided on the circuit board at
a position corresponding to the light receiving element, and
sealing resin is applied between the semiconductor bare chip and
the circuit board. The frame-shaped protruding portion is provided
around the penetration hole on the circuit board and the
semiconductor bare chip is mounted in contact with the top of the
protruding portion.
[Patent Document 1]
[0005] Japanese Patent Kokai Publication No. JP-P2003-68939A
SUMMARY
[0006] The entire disclosure of Patent Document 1 is incorporated
herein by reference thereto. The following analyses are given by
the present invention.
[0007] According to the semiconductor device of Patent Document 1,
the protruding portion is provided between the electronic element
and the circuit board, and at the same time, in contact with the
electronic element. Thus there may be a risk that the protruding
portion exerts local pressure and causes a breakage of the
electronic element. Particularly, the pressure exerted to the
electronic element may increase when the electronic element is
mounted on a board or when the protruding portion expanded during a
heat processing.
[0008] For preventing the breakage of the electronic element due to
the local pressure (or load) by the protruding portion at the flip
chip attachment, a pressure control will become necessary. However,
when controlling of the local pressure is necessary, it is
difficult to mount electronic elements rapidly and therefore,
productivity will become worse.
[0009] In addition, the semiconductor device according to Patent
Document 1 requires high dimensional precision of heights of the
protruding portion and the bump. If the dimensional precision is
low for these elements, an electric contact between the electronic
element and the board cannot be secured or the electronic element
may be damaged due to local pressure by the protruding portion. On
the other hand, for improving the dimensional precision of the
elements, additional equipments for improving the high precision
become necessary and it causes decrease of the productivity and
increase of the production cost. Thus there is much desired in the
art.
[0010] According to a first aspect of the present invention, there
is provided an electronic device comprising: an electronic element
having an exposed functional portion on a first surface; a frame
member having a first penetration hole; and a board having a second
penetration hole. The frame member is provided on the first surface
of the electronic element such that the first penetration hole
faces at least a part of the functional portion. The electronic
element is mounted on the board such that at least a part of the
functional portion faces the second penetration hole. The frame
member does not contact with the board.
[0011] According to a second aspect of the present invention, there
is provided a method for fabricating an electronic device
comprising: making a frame member on a first surface of an
electronic element having an exposed functional portion on the
first surface such that the frame member surrounds at least a part
of the functional portion; and mounting the electronic element on a
board having a penetration hole such that the penetration hole
faces at least a part of the functional portion.
[0012] The present invention has at least one effect described
below.
[0013] According to the present invention, the frame member does
not contact with the board. Thus a local pressure exerted to the
electronic element by the frame member can be avoided. As a result,
the present invention provides a high functional and high reliable
electronic device.
[0014] According to the present invention, there is no need to
fabricate the frame and an electrically conductive member (bump)
between the electronic element and the board with high precision.
Therefore, it is possible to fabricate such electronic devices
without decreasing productivity and increasing production cost.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a perspective view of an electronic device
according to a first exemplary embodiment of the present
invention.
[0016] FIG. 2 is a cross sectional view along II-II line in FIG.
1.
[0017] FIGS. 3A to 3F are process flow diagrams for illustrating
fabrication manner of an electronic device according to a first
exemplary embodiment of the present invention.
[0018] FIGS. 4A to 4D are process flow diagrams for illustrating
fabrication manner of an electronic device according to a first
exemplary embodiment of the present invention.
[0019] FIG. 5 is a cross sectional view of an electronic device
according to a second exemplary embodiment of the present
invention.
[0020] FIG. 6 is a process flow diagram for illustrating
fabrication manner of an electronic device according to a second
exemplary embodiment of the present invention.
[0021] FIG. 7 is a cross sectional view of an electronic device
according to a third exemplary embodiment of the present
invention.
[0022] FIG. 8 is a cross sectional view of an electronic device
according to a fourth exemplary embodiment of the present
invention.
[0023] FIG. 9 is a process flow diagram for illustrating
fabrication manner of an electronic device according to a fourth
exemplary embodiment of the present invention.
PREFERRED MODES
[0024] Followings are preferred modes of each aspect of the present
invention.
[0025] According to a preferred mode of a first aspect of the
present invention, the frame member is inserted into the second
penetration hole of the board.
[0026] According to a preferred mode of a first aspect of the
present invention, a gap is formed between an outer surface of the
frame member and an internal surface of the second penetration hole
of the board.
[0027] According to a preferred mode of a first aspect of the
present invention, the frame member has a height of 0.03 mm or
more.
[0028] According to a preferred mode of a first aspect of the
present invention, the frame member is made of resin.
[0029] According to a preferred mode of a second aspect of the
present invention, the electronic element is mounted on the board
such that the frame member is inserted into the penetration hole in
a mounting step.
[0030] According to a preferred mode of a second aspect of the
present invention, the step for making a frame member comprises:
forming a precursor film for a frame member on the electronic
element, and processing the precursor film for a frame member such
that at least a part of the functional portion is exposed.
[0031] An electronic device according to a first exemplary
embodiment of the present invention will be explained. FIG. 1 is a
perspective view of an electronic device according to a first
exemplary embodiment of the present invention. FIG. 2 is a cross
sectional view along II-II line in FIG. 1.
[0032] The electronic device 10 comprises a board 13, and an
electronic element 11 mounted on the board 13 by a flip chip
attachment. The electronic element 11 is connected with the board
by an electrically conductive member (bump) 14. For example, an
electric signal in the electronic element 11 is conveyed to the
board 13 through the electrically conductive member 14 and then
transferred to a terminal formed on the opposite surface to a
surface facing to the electronic element 11 via an internal wiring
of the board 13. The electrically conductive member 14 is coated
with an underfill resin 15 and the underfill resin 15 acts so as to
unite the board 13 and the electronic element 11.
[0033] The electronic element 11 comprises a functional portion
11a. The electronic element 11 may be, for example, a light
receiving element for converting an optical signal into an
electrical signal. In this case, the functional portion 11a is a
light receiving portion.
[0034] The electronic device 10 further comprises a frame member or
a pipe member 12 (referred to as "frame member" hereinafter) in
which a first penetration hole 12a is perforated. The frame member
12 is provided on the electronic element 11 such that the first
penetration hole 12a of the frame member 12 faces at least a part
of the functional portion 11a and at least a part of the functional
portion 11a is exposed through the first penetration hole 12a.
Preferably, the frame member 12 is formed so as to surround the
whole of the exposed part of the functional portion 11a.
[0035] The board 13 has a second penetration hole 13a at a position
corresponding to the functional portion 11a of the electronic
element 11. This means that the second penetration hole 13a faces
at least a part of the functional portion 11a. The first
penetration hole 12a of the frame member 12 and the second
penetration hole 13a of the board 13 are also facing (opposing)
each other. The board 13 does not contact with the frame member 12.
Preferably, the electronic element 11 is mounted such that the
frame member 12 is inserted in the second penetration hole 13a of
the board 13. In this case a space d is formed between an outer
surface of the frame member 12 and an internal surface of the
second penetration hole 13a of the board 13. A distance of the
space d is preferably formed such that the frame member 12 will not
contact with the board 13 even when the frame member 12 and the
board 13 expanded or elongated due to increasing of temperature. It
is possible to prevent, owing to the arrangement, the board 13 from
pressing the electronic element 11 locally via the frame member 12
even when the electronic element 11 is mounted on the board 13 or
when the frame member 12 expanded by a heating step (heating step
for mounting or a durability test such as a heating cycle test,
etc. of an electronic device 10), for example. As a result,
according to the present invention, it becomes possible to prevent
breakage of the electronic element 11 by the frame member 12.
Furthermore, upon temperature fluctuation, the frame member 12 can
expand and contract independently from other elements having
different linear expansion coefficients. As a result, according to
the present invention, it becomes possible to prevent the frame
member 12 from detaching from the electronic element 11 or exerting
pressing force on the electronic element 11 even when the
temperature fluctuated. In addition, a stress exerted on the
electrically conductive member 14 can be reduced when the
temperature fluctuated because expansion and contraction of the
board 13 are not influenced by the frame member 12, or rather a
freedom of degree of expansion and contraction can be improved by
the space d. As a result, according to the present invention, it
becomes possible to improve reliability of an electrical
connection.
[0036] At least a part, preferably the whole, of the functional
portion 11a of the electronic element 11 is exposed through the
first penetration hole 12a of the frame member 12 and the second
penetration hole 13a of the board 13. When the functional portion
11a is a light receiving portion, for example, an optical signal is
input to the light receiving portion 11a through the first
penetration hole 12a of the frame member 12.
[0037] Preferably, the height of the frame member 12 (height from a
surface of the electronic element 11) is set such that the
underfill resin 15 does not get over the frame member 12 into the
first penetration hole 12a when the underfill resin 15 is filled.
Preferably, a height of the frame member 12 is 0.03 mm or more (0.1
mm, for example) when the underfill resin 15 is an epoxy resin, for
example. It may be possible to prevent the underfill resin 15 from
getting over the frame member 12 onto the surface of the functional
portion 11a unless oversupplying the underfill resin 15.
Preferably, the height of the frame member 12 is set such that the
frame member 12 does not project from the surface of the board 13
too much. For example, a height of the frame member 12 is
preferably 1 mm or less. If the frame member 12 projects from the
board 13 too high, the electronic device 10 becomes so thick.
[0038] A planar shape (outer circumferential shape) of an end
surface of the frame member 12 is depicted as an annular shape (a
planer shape of the first penetration hole 12a is circle) in FIG.
1; however, the shape is not limited to the shape but various
shapes can be applied. For example, a planar shape of the end
surface of the frame member 12 may be oval or polygonal. Also a
shape of the first penetration hole 12a (inner circumferential
shape) cannot be limited to a circle but can be various shapes such
as an oval or polygon.
[0039] The frame member 12 may be formed by a resin, for example.
When using a resin as a material of the frame member 12, the
material of the frame member 12 may include photo-setting resin
such as an acrylic resin or thermo-setting resin such as an epoxy
resin. A kinetic viscoelasticity of the frame member 12 ranges
preferably from 2 GPa to 6 GPa at 25 degrees C. in hardened state.
In addition, the kinetic viscoelasticity of the frame member 12
ranges preferably at least 1 MPa, and 50 MPa or less at 200 degrees
C. in hardened state. By virtue of the viscoelasticity of the frame
member 12 of these ranges, the frame member 12 can deform
elastically to some extent in accordance with the fluctuations of
temperature and relieve the thermal stress during a reflow step for
mounting the electronic device 10 or an environmental test, and the
like. The viscoelasticity of the frame member 12 is measured in
conformity with JISK7244-4.
[0040] The electronic device 10 further comprises a sealing resin
16. The sealing resin 16 seals a side of the board 13 on which the
electronic element 11 is mounted so as to cover and protect the
electronic element 11. An epoxy resin, for example, may be used as
the sealing resin 16.
[0041] The electronic device 10 may further comprise a protection
film (not shown) for protecting the functional portion 11a on the
frame member 12 and the board 13. Preferably the protecting film
shows a heat-resistance property at a temperature of reflow step or
more and is made of a material that can be detached.
[0042] Next, a fabrication method of the electronic device
according to a first exemplary embodiment of the present invention
will be explained. A semiconductor device mounting a semiconductor
element having a light receiving portion as a functional portion is
employed as an example. FIGS. 3 and 4 are process flow diagrams
illustrating fabrication steps of an electronic device according to
a first exemplary embodiment of the present invention.
[0043] At first a wafer 11A, on which a plurality of semiconductor
elements are formed as electronic elements, is prepared as shown in
FIG. 3A. A light receiving portion 11a is exposed on a surface of
each semiconductor element of the wafer 11A. Although two
semiconductor elements are shown in FIG. 3A, the number of the
semiconductor elements is not limited to two but may be one or 3 or
more.
[0044] Next, a precursor film 12A for frame member is formed on the
wafer 11A as shown in FIG. 3B. In a case where the frame member 12
is formed by a resin, a resin film or liquid resin may be used for
the precursor film 12A for frame member. A resin film having a
uniform thickness is more preferable. It will be easier to form a
film made of resin having a thickness of uniform 0.03 mm or more on
the whole wafer 11A by using a resin film than a liquid resin. When
forming a frame member of a height of 0.1 mm, a precursor film 12A
for frame member having a thickness of 0.1 mm will be used.
[0045] Next, the precursor film 12A for frame member is exposed and
patterned using a mask 18 as shown in FIG. 3C. At this step the
precursor film 12A for frame member is patterned such that the
first penetration hole 12a of frame member 12 exposes at least a
part, preferably the whole, of the light receiving portion 11a.
Next, the precursor film 12A for frame member is developed and
other parts (exposed parts) than a part that is to be a frame
member 12 are removed. Then the precursor film 12A for frame member
is formed into a shape of the frame member 12 to surround each of
the light receiving portions 11a. Next, the precursor film 12A for
frame member is heated to harden to form the frame member 12 (FIG.
3D) (the step shown by FIGS. 3B to 3D is referred to as frame
member forming step). The heat processing produces secured union of
the frame member 12 and the semiconductor element (wafer 11A). The
frame member 12 won't be deformed so much by the heat
processing.
[0046] According to the fabrication method, a plurality of frame
members 12 of a plurality semiconductor elements 11 can be formed
at one time and production efficiency can be increased.
[0047] Next, an electrically conductive member 14, for attaching
the wafer to the board 13 by flip chip, is formed on the wafer 11A
(FIG. 3E). According to the present invention, the bump can be
formed without taking the frame member 12 into account, that is,
without requiring a high precision of height.
[0048] Next, the wafer 11A is cut into individual semiconductor
element to form the semiconductor element 11 having a frame member
12 (FIG. 3F).
[0049] Next, a precursor material 13A for board containing a
plurality of board 13 is prepared. A second penetration hole 13a is
formed on each of the boards 13 of the precursor material 13A for
board. Next, the semiconductor elements 11 are attached by flip
chip on the precursor material 13A for board (FIG. 4A, referred to
as mounting step). At this step, the semiconductor element 11 is
attached such that the second penetration hole 13a of the board 13
faces both of the light receiving portion 11a and the first
penetration hole 12a of the frame member 12 and such that the frame
member 12 is inserted into the second penetration hole 13a.
[0050] According to the present invention, because the frame member
12 does not contact with the board 13, unnecessary stress toward
the semiconductor element 11 from the frame member 12 in the
mounting step can be prevented. A mounting efficiency is not
decreased because a load control against the pressure from the
frame 12 can be eliminated.
[0051] Next, an underfill resin 15 is formed around the
electrically conductive member 14 for reinforcing the connection
between the precursor material 13A for board and the semiconductor
element 11 (FIG. 4B). When filling the underfill resin 15,
spreading of the underfill resin 15 onto the light receiving
portion 11a can be prevented by the frame member 12.
[0052] Next, a plurality of semiconductor elements 11 are sealed as
a whole by a sealing resin 16 (FIG. 4C). The light receiving
portion 11a is not covered by the sealing resin 16 because the
underfill resin 15 is filled between the precursor material 13A for
board and the semiconductor element 11 and the light receiving
portion 11a is surrounded by the frame member 12.
[0053] Next, the precursor material 13A for board and the sealing
resin 16 are separated according to each semiconductor element 11
to produce the electronic device (semiconductor device) 10.
[0054] A protection film (not shown) for covering the frame member
12 and the board 13 may be formed as necessary.
[0055] Next, an electronic device according to a second exemplary
embodiment of the present invention will be explained. FIG. 5 is a
cross sectional view of an electronic device according to a second
exemplary embodiment of the present invention. In FIG. 5, the same
element as a first exemplary embodiment is denoted by the same
symbol.
[0056] A sealing resin 26 seals the whole of the electronic element
11 in the electronic device 10 of a first exemplary embodiment;
however, a sealing resin 26 of an electronic device 20 of a second
exemplary embodiment is formed such that a surface (referred to as
"second surface" hereinafter) opposite to a surface (referred to as
"first surface" hereinafter) on which the functional portion 11a of
the electronic element 11 is formed is exposed. Other structures of
the electronic device 20 of a second exemplary embodiment are the
same as those of a first exemplary embodiment.
[0057] Next, a fabrication method of the electronic device 20 of a
second exemplary embodiment will be explained. FIG. 6 is a process
flow diagram illustrating fabrication steps of the electronic
device 20 of a second exemplary embodiment. A different step from
the fabrication method of the electronic device 10 of a first
exemplary embodiment, shown in FIGS. 3 and 4, is the resin sealing
step shown in FIG. 4C. After the underfill resin forming step shown
in FIG. 4B, a buffer sheet 21 is provided on the second surface of
the electronic element 11 as shown in FIG. 6. Then a first sealing
die 22a and a second sealing die 22b are set from upside and
downside, respectively, and a sealing resin 26 is provided. The
sealing resin 26 can be formed without covering the second surface
of the electronic element 11 by such a fabrication method. The
buffer sheet 21 is provided between the electronic element 11 and
the sealing die 22 and prevents the sealing resin 26 from flowing
into the second surface of the electronic element 11 and prevents
the sealing die 22 from damaging the electronic element 11. A resin
sheet having an extensibility and flexibility can be used as a
buffer sheet 21 and a release film, for example, can be
available.
[0058] Other fabrication steps of the electronic device 20 of a
second exemplary embodiment are the same as those of a first
exemplary embodiment.
[0059] According to a second exemplary embodiment, a heat radiation
efficiency of the electronic element can be improved and therefore,
a malfunction of the electronic device can be prevented.
[0060] Next, an electronic device according to a third exemplary
embodiment of the present invention will be explained. FIG. 7 is a
cross sectional view of an electronic device of a third exemplary
embodiment of the present invention. In FIG. 7, the same element as
a first exemplary embodiment is denoted by the same symbol.
[0061] An electronic device 30 of a third exemplary embodiment,
which is different from a first exemplary embodiment or a second
exemplary embodiment, has no sealing resin. Other structures of the
electronic device of a third exemplary embodiment are the same as
those of a first exemplary embodiment.
[0062] A fabrication method of the electronic device 30 of a third
exemplary embodiment is the same as that of a first exemplary
embodiment except that the resin sealing step shown in FIG. 4C is
eliminated.
[0063] According to a third exemplary embodiment, a heat radiation
efficiency of the electronic device can be improved and therefore,
a malfunction of the electronic device can be prevented.
[0064] Next, an electronic device according to a fourth exemplary
embodiment of the present invention will be explained. FIG. 8 is a
cross sectional view of an electronic device of a fourth exemplary
embodiment of the present invention. In FIG. 8, the same element as
a first exemplary embodiment is denoted by the same symbol.
[0065] An electronic device 40 of a fourth exemplary embodiment,
which is different from first to third exemplary embodiments, has
no underfill resin. However, instead of that, a sealing resin 46 is
filled between the electronic element 11 and the board 13, between
the frame member 12 and the board 13 and around the electronic
element 11.
[0066] Preferably, a top surface (end surface at a side of board
13) 12b of the frame member 12 protrudes from a top surface
(exposed surface) 13b of the board 13. Preferably, the top surface
12b of the frame member 12 protrudes from the top surface 13b of
the board 13 by 0.05 mm or more, for example. It is possible to
prevent the sealing resin 46 from flowing into the first
penetration hole 12a of the frame 12 during the resin sealing step
by the protrusion of the top surface 12b of the frame member 12
from the top surface 13b of the board 13.
[0067] Other structures of the electronic element 40 of a fourth
exemplary embodiment are the same as those of a first exemplary
embodiment.
[0068] According to a fourth exemplary embodiment, the sealing
resin 46 provided between the frame member 12 and the board 13 can
relieve the stress due to an expansion or contraction of the
elements caused by the fluctuations of temperature. As a result a
reliability of the electronic device 40 can be improved.
[0069] Next, a fabrication method of the electronic device 40 of a
fourth exemplary embodiment will be explained. The fabrication
method of the electronic device 40 of a fourth exemplary embodiment
does not include an underfill resin forming step shown in FIG. 4B.
Instead of that, the sealing resin 46 is filled also between the
electronic element 11 and the board 13 in the resin sealing step.
FIG. 9 is a schematic sectional view for illustrating fabrication
steps of the electronic device 40 of a fourth exemplary embodiment.
As shown in FIG. 9, a first buffer sheet 41a is provided on the
second surface of the electronic element 11 and a second buffer
sheet 41b is provided on the upper surface (exposed surface) 13b of
the board 13 after the mounting step shown in FIG. 4A. The first
and the second buffer sheets 41a and 41b are similar to the buffer
sheet of a second exemplary embodiment. Then a first and a second
sealing dies 42a and 42b are set on the first and the second buffer
sheets 41a and 41b at upper and lower layers, respectively, and the
sealing resin 46 is formed. It is preferable to provide the second
buffer sheet 41b such that the top surface 12b of the frame member
12 sinks into the second buffer sheet 41b or the second buffer
sheet 41b is depressed by the top surface 12b of the frame member
12. The structure can prevent the sealing resin 46 from flowing
into the first penetration hole 12a of the frame member 12. The
flowing of the sealing resin 46 into the first penetration hole 12a
can be also prevented by forming the frame members 12 in a uniform
height. A local pressure exerted on the electronic element 11 by
the die-forming may be diminished by an elastic deformation of the
second buffer sheet 41b. The local pressure exerted on the
electronic element 11 may be also reduced by an elastic deformation
of the frame member 12 when the frame member 12 is made of
resin.
[0070] A fabrication method of the electronic device 40 of a fourth
exemplary embodiment other than the step above explained is the
same as that of a first exemplary embodiment.
[0071] As many apparently widely different exemplary embodiments of
the present invention can be made without departing from the spirit
and scope thereof, it is to be understood that the invention is not
limited to the specific exemplary embodiments thereof except as
defined in the appended claims. Also it should be noted that any
combination and/or selection of the disclosed and/or claimed
elements, matters and/or items may fall under the modifications
aforementioned.
[0072] It should be noted that other objects, features and aspects
of the present invention will become apparent in the entire
disclosure and that modifications may be done without departing the
gist and scope of the present invention as disclosed herein and
claimed as appended herewith.
[0073] The present invention can be applicable preferably to an
electronic device having a light receiving portion as a functional
portion, for example. Such an electronic device may be used for a
DVD player, digital video camera or digital still camera, for
example.
* * * * *