U.S. patent application number 16/406155 was filed with the patent office on 2019-08-29 for circuit device and method of manufacturing the same.
This patent application is currently assigned to SEMICONDUCTOR COMPONENTS INDUSTRIES, LLC. The applicant listed for this patent is SEMICONDUCTOR COMPONENTS INDUSTRIES, LLC. Invention is credited to Hideyuki SAKAMOTO.
Application Number | 20190267300 16/406155 |
Document ID | / |
Family ID | 46315302 |
Filed Date | 2019-08-29 |
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United States Patent
Application |
20190267300 |
Kind Code |
A1 |
SAKAMOTO; Hideyuki |
August 29, 2019 |
CIRCUIT DEVICE AND METHOD OF MANUFACTURING THE SAME
Abstract
Provided is a circuit device in which encapsulating resin to
encapsulate a circuit board is optimized in shape, and a method of
manufacturing the circuit device. A hybrid integrated circuit
device, which is a circuit device according to the present
invention includes a circuit board, a circuit element mounted on a
top surface of the circuit board, and encapsulating resin
encapsulating the circuit element, and coating the top surface,
side surfaces, and a bottom surface of the circuit board. In
addition, the encapsulating resin is partly recessed and thereby
provided with recessed areas at two sides of the circuit board. The
providing of the recessed areas reduces the amount of resin to be
used, and prevents the hybrid integrated circuit device from being
deformed by the cure shrinkage of the encapsulating resin.
Inventors: |
SAKAMOTO; Hideyuki;
(Ota-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SEMICONDUCTOR COMPONENTS INDUSTRIES, LLC |
Phoenix |
AZ |
US |
|
|
Assignee: |
SEMICONDUCTOR COMPONENTS
INDUSTRIES, LLC
Phoenix
AZ
|
Family ID: |
46315302 |
Appl. No.: |
16/406155 |
Filed: |
May 8, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14661080 |
Mar 18, 2015 |
10332816 |
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16406155 |
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13331784 |
Dec 20, 2011 |
8995139 |
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14661080 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 2224/48091
20130101; H01L 2924/13091 20130101; B29C 45/14008 20130101; B29C
45/14819 20130101; H01L 2224/73265 20130101; H05K 2203/1545
20130101; H05K 2201/09154 20130101; B29L 2031/3425 20130101; H05K
3/0052 20130101; H01L 2924/13055 20130101; H01L 23/3107 20130101;
H01L 2924/00 20130101; H05K 3/0097 20130101; H01L 2224/48091
20130101; H01L 2924/00014 20130101; H01L 2924/19105 20130101; H01L
2924/13091 20130101; H01L 21/565 20130101; H05K 3/284 20130101;
H05K 2203/1316 20130101; H01L 2924/13055 20130101; H01L 2924/00
20130101 |
International
Class: |
H01L 23/31 20060101
H01L023/31; B29C 45/14 20060101 B29C045/14; H01L 21/56 20060101
H01L021/56; H05K 3/28 20060101 H05K003/28 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 24, 2010 |
JP |
JP2010-287508 |
Claims
1. A circuit device comprising: a circuit board; encapsulating
resin coating the surfaces of the circuit board; leads fixed to the
circuit board, each lead comprising an end extending from the
encapsulating resin; and one or more recesses formed into a
thickness of the encapsulating resin between two of the surfaces of
the circuit board.
2. The circuit device of claim 1, further comprising a first
side-edge of the circuit board, the first side-edge facing a second
side-edge of the circuit board in a longer-side direction of the
circuit board; and a third side-edge of the circuit board, the
third side-edge facing a fourth side-edge of the circuit board in a
shorter-side direction of the circuit board; wherein the leads are
arranged along the first side-edge and the second side-edge; and
wherein the one or more recesses are provided at a side of each of
the third side-edge and the fourth side-edge.
3. The circuit device of claim 2, further comprising one or more
depressed areas, each depressed area provided at the side of each
of the third side-edge and the fourth side-edge of the circuit
board, each depressed area formed by depressing a portion of the
encapsulating resin inwards in a planar view, wherein the one or
more recesses are provided on both sides of the one or more
depressed areas.
4. The circuit device of claim 1, wherein a circuit-board-side
surface of each of the one or more recesses has a step-like
shape.
5. The circuit device of claim 1, wherein a portion of each of the
one or more recesses is located above the circuit board.
6. The circuit device of claim 1, wherein one or more cutaway
portions are formed in corners of the encapsulating resin.
7. A circuit device comprising: a circuit board; encapsulating
resin coating the surfaces of the circuit board; leads fixed to the
circuit board, each lead comprising an end extending from the
encapsulating resin; one or more recesses formed into a thickness
of the encapsulating resin between two of the largest planar
surfaces of the circuit board; and a first side-edge of the circuit
board, the first side-edge facing a second side-edge of the circuit
board in a longer-side direction of the circuit board.
8. The circuit device of claim 7, further comprising: a third
side-edge of the circuit board, the third side-edge facing a fourth
side-edge of the circuit board in a shorter-side direction of the
circuit board; wherein the leads are arranged along the first
side-edge and the second side-edge; and wherein the one or more
recesses are provided at a side of each of the third side-edge and
the fourth side-edge.
9. The circuit device of claim 8, further comprising one or more
depressed areas, each depressed area provided at the side of each
of the third side-edge and the fourth side-edge of the circuit
board, each depressed area formed by depressing a portion of the
encapsulating resin inwards in a planar view, wherein the one or
more recesses are provided on both sides of the one or more
depressed areas.
10. The circuit device of claim 7, wherein a circuit-board-side
surface of each of the one or more recesses has a step-like
shape.
11. The circuit device of claim 7, wherein a portion of each of the
one or more recesses is located above the circuit board.
12. The circuit device of claim 7, wherein one or more cutaway
portions are formed in corners of the encapsulating resin.
13. A circuit device comprising: a circuit board; encapsulating
resin coating the surfaces of the circuit board; leads fixed to the
circuit board, each lead comprising an end extending from the
encapsulating resin; one or more recesses formed into the
encapsulating resin between two of the largest planar surfaces of
the circuit board; and a third side-edge of the circuit board, the
third side-edge facing a fourth side-edge of the circuit board in a
shorter-side direction of the circuit board.
14. The circuit device of claim 13, further comprising: a first
side-edge of the circuit board, the first side-edge facing a second
side-edge of the circuit board in a longer-side direction of the
circuit board; wherein the leads are arranged along the first
side-edge and the second side-edge; and wherein the one or more
recesses are provided at a side of each of the third side-edge and
the fourth side-edge.
15. The circuit device of claim 14, further comprising one or more
depressed areas, each depressed area provided at the side of each
of the third side-edge and the fourth side-edge of the circuit
board, each depressed area formed by depressing a portion of the
encapsulating resin inwards in a planar view, wherein the one or
more recesses are provided on both sides of the one or more
depressed areas.
16. The circuit device of claim 13, wherein a circuit-board-side
surface of each of the one or more recesses has a step-like
shape.
17. The circuit device of claim 13, wherein a portion of each of
the one or more recesses is located above the circuit board.
18. The circuit device of claim 13, wherein one or more cutaway
portions are formed in corners of the encapsulating resin.
Description
[0001] This application is a continuation of previously filed
application Ser. No. 14/661,080, to Sakamoto, filed Mar. 18, 2015,
which was a divisional of application Ser. No. 13/331,784 to
Sakamoto, filed Dec. 20, 2011, now U.S. Pat. No. 8,995,139, which
claimed priority to Japanese Patent Application Number JP
2010-287508 filed on Dec. 24, 2010, the disclosures of each of
which are hereby incorporated entirely herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a circuit device and a
method of manufacturing the circuit device. In particular the
present invention relates to a circuit device in which
encapsulating resin coats a circuit board having a circuit element
mounted thereon, and a method of manufacturing the circuit
device.
[0004] 2. Description of the Related Art
[0005] FIG. 8 shows a hybrid integrated circuit device 100 of the
related art having a structure in which an electric circuit mounted
on the surface of a board 101 (see Japanese Patent Application
Publication No. Hei 11-340257). A conductive pattern 103 is formed
on the surface of the rectangular board 101 with an insulating
layer 102 formed in between. A circuit element 105 is fixed at a
predetermined position on the conductive pattern 103, and thereby a
predetermined electric circuit is formed. In this example, a
semiconductor element and a chip element are connected, as circuit
elements, to the conductive pattern 103. A lead 104 is connected to
a pad 109 that is a portion of the conductive pattern 103 formed in
a peripheral area of the board 101. The lead 104 functions as an
external terminal. Encapsulating resin 108 has a function of
encapsulating the electric circuit formed on the surface of the
board 101.
[0006] The method of manufacturing the hybrid integrated circuit
device 100 can be summarized as follows. Firstly, a hybrid
integrated circuit including the conductive pattern 103 and the
circuit element 105 is mounted on the top surface of the board 101.
Then, the lead 104 is fixed, with a solder, to the pad 109 located
in a peripheral area of the board 101. Then, the encapsulating
resin 108 is formed to cover the board 101 and the lead 104. The
encapsulating resin 108 is usually formed by transfer molding using
a mold. For the transfer molding, a mold with an internal-wall
shape corresponding to the external shape of the encapsulating
resin 108 is firstly prepared, and the board 101 is placed in the
cavity of the mold. Then, encapsulating resin in the form of a
liquid is injected into the cavity, and thereby the top surface,
the side surfaces, and the bottom surface of the board 101 are
coated with the encapsulating resin. Then, the encapsulating resin
in the cavity is cured by heating. Then, the hybrid integrated
circuit device 100 encapsulated by the encapsulating resin 108 is
taken out of the mold.
SUMMARY OF THE INVENTION
[0007] In a case where the hybrid integrated circuit device 100
with the above-described configuration is provided with a fixation
portion for screwing, which is formed of the encapsulating resin
108 projecting from a side of the board 101, a larger amount of the
encapsulating resin 108 is needed, which results in a higher
cost.
[0008] The hybrid integrated circuit device 100 has another problem
that cure shrinkage of the encapsulating resin 108 inflects the
board 101 into a concave shape in the view of FIG. 8. This is
because a larger amount of encapsulating resin 108 coats the top
surface of the board 101 than that coating the bottom surface of
the board 101, and accordingly a residual stress generated by the
shrinkage of the encapsulating resin 108 is larger on the top
surface of the board 101 than on the bottom surface of the board
101.
[0009] The hybrid integrated circuit device 100 has still another
problem that voids, which are not filled with the encapsulating
resin 108, may possibly be formed under the board 101.
Specifically, in order to improve heat dissipation of the hybrid
integrated circuit device 100 in use, it is preferable to make the
encapsulating resin 108 coating the bottom surface of the board 101
as thin as possible. For example, the encapsulating resin 108
coating the bottom surface of the board 101 preferably has a
thickness of 0.5 mm or even smaller. Thus, the heat generated by
the operations of the circuit element 105 is released
satisfactorily through the board 101 and the encapsulating resin
108 coating the backside surface of the board 101. To achieve this,
the distance between the bottom surface of the board 101 and the
internal wall of the mold in the process of resin encapsulation
needs to be narrowed. Such a narrow gap, however, may possibly
prevent the encapsulating resin 108 from fully spreading into this
narrow gap, and as a consequence, may cause the formation of voids
under the board 105.
[0010] The present invention is made in view of the problems
described above, and aims to provide a circuit device in which
encapsulating resin to encapsulate a circuit board is optimized in
shape, and a method of manufacturing the circuit device.
[0011] A circuit device according to the present invention
includes: a circuit board having a conductive pattern and a circuit
element mounted on a top surface of the circuit board;
encapsulating resin coating the top surface, side surfaces, and a
bottom surface of the circuit board; leads fixed to the circuit
board and each having an end drawn from the encapsulating resin;
and a recessed area formed by recessing a portion of the
encapsulating resin in a thickness direction at a side of the
circuit board.
[0012] A method of manufacturing a circuit device according to the
present invention includes the steps of: preparing a circuit board
having a conductive pattern and a circuit element mounted on a top
surface of the circuit board; setting the circuit board in a cavity
of a set of molds including an upper mold and a lower mold so that
the top surface of the circuit board faces an internal wall of the
upper mold; and injecting encapsulating resin into the cavity
through a gate, and thereby coating the top surface, side surfaces
and a bottom surface of the circuit board with the encapsulating
resin, in which a guiding portion is formed by projecting downwards
a portion of the internal wall of the upper mold located in a
region between the circuit board and the gate, and the
encapsulating resin is made to flow along the guiding portion into
a gap between the bottom surface of the circuit board and an
internal wall of the lower mold.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 shows diagrams illustrating a hybrid integrated
circuit device, a circuit device of preferred embodiments of the
invention. FIG. IA is a perspective view. FIGS. IB and IC are
sectional views.
[0014] FIG. 2 shows diagrams illustrating the hybrid integrated
circuit device of the preferred embodiments of the invention. FIG.
2A is a perspective view illustrating the same hybrid integrated
circuit device that is illustrated in FIG. IA but is depicted
upside down. FIG. 2B is a sectional view of the hybrid integrated
circuit shown in FIG. 2A. FIG. 2C is a top view of a depressed
area.
[0015] FIG. 3 shows diagrams illustrating the circuit board
incorporated in the hybrid integrated circuit device of the
preferred embodiments of the invention. FIG. 3A is a perspective
view. FIGS. 3B and 3C are sectional views.
[0016] FIG. 4 shows diagrams illustrating a method of manufacturing
the hybrid integrated circuit device, the circuit device of the
preferred embodiments of the invention. FIG. 4A is a perspective
view. FIGS. 4B and 4C are sectional views.
[0017] FIG. 5 is a plan view illustrating the method of
manufacturing the hybrid integrated circuit device of the preferred
embodiments of the invention.
[0018] FIG. 6 shows diagrams illustrating the method of
manufacturing the hybrid integrated circuit device of the preferred
embodiments of the invention. FIG. 6A is a diagram illustrating
encapsulating resin formed in a manufacturing process. FIGS. 6B and
6C are sectional views illustrating the manufacturing process.
[0019] FIG. 7 shows diagrams illustrating the method of
manufacturing the hybrid integrated circuit device of the preferred
embodiments of the invention. FIG. 7A is a diagram illustrating
encapsulating resin formed in a manufacturing process. FIGS. 7B and
7C are sectional views illustrating the manufacturing process.
[0020] FIG. 8 is a sectional view illustrating a circuit device of
the related art.
DESCRIPTION OF THE INVENTION
First Embodiment: Configuration of Circuit Device
[0021] The configuration of a hybrid integrated circuit device 10
(circuit device) is described below by referring to FIG. 1. FIG. IA
is a perspective view illustrating the hybrid integrated circuit
device 10 seen from above. FIG. 1B is a sectional view taken along
the line B-B' in FIG. IA. FIG. IC is a sectional view taken along
the line C-C' in FIG. IA.
[0022] As FIGS. 1A and 1B shows, the hybrid integrated circuit
device 10 includes a circuit board 12 and a hybrid integrated
circuit including a circuit element 18 and mounted on top of the
circuit board 12. Both the hybrid integrated circuit and the
circuit board 12 are encapsulated with encapsulating resin 28.
Leads 20 are connected to the hybrid integrated circuit built in
the hybrid integrated circuit device 10, and are drawn from the
encapsulating resin 28.
[0023] The circuit board 12 shown in FIG. 1B is a metal substrate
made mainly of aluminum, copper, or the like. The planar size of
the circuit board 12 is approximately 2.0 cm.times.1.0 cm, for
example. The thickness of the circuit board 12 is approximately 1.5
mm, for example. If the circuit board 12 is made of aluminum, both
the top surface and the bottom surface of the circuit board 12 are
coated with alumite films formed by anodization. Each side of the
circuit board 12 has sloping surfaces that extend outwards.
Specifically, two sloping surfaces are formed: a first sloping
surface 22 that extends continuously and obliquely outwards from
the top surface of the circuit board 12; and a second sloping
surface 24 that extends continuously and obliquely outwards from
the bottom surface of the circuit board 12.
[0024] An insulating layer 14 is formed to cover entirely the top
surface of the circuit board 12, and is made of a resin material
filled densely with granular filler such as alumina. The insulating
layer 14 has a thickness of approximately 50 .mu.m, for
example.
[0025] A conductive pattern 16 is formed by etching, into a
predetermined shape, a foil of copper or of a conductive material,
attached to the top surface of the insulating layer 14. In this
embodiment, mount pads where the circuit element 18 is mounted are
formed with the conductive pattern 16. Wiring portions that connect
the mount pads to one another are also formed with the conductive
pattern 16. In addition, as FIG. 1B shows, pads 26 and 27 are
provided each along one of two opposite sides of the circuit board
12. The inner-side end of each lead 20 is soldered to either one of
these pads 26 and 27.
[0026] The circuit element 18 is mounted at a predetermined
position on the conductive pattern 16 by using a conductive,
bonding material such as a solder. A wide variety of elements are
used as the circuit element 18. For example, passive elements such
as chip capacitors and chip resistors, active elements such as
transistors, or resin-encapsulated packages can be used for this
purpose. If a power transistor, such as a MOSFET and an IGBT, is
mounted as the circuit element 18, the transistor is mounted on a
heat sink that is fixed to the top of the conductive pattern. Note
that if a semiconductor element such as an IC is used, the
semiconductor element is connected to the conductive pattern 16
with metal thin wires.
[0027] The encapsulating resin 28 coats the conductive pattern 16
and the circuit element 18 that are formed on the top surface of
the circuit board 12. In addition, the single encapsulating resin
28 coats all of the top surface, the side surfaces, and the bottom
surface of the circuit board 12. The resin encapsulation including
also that of the bottom surface of the circuit board 12 can prevent
outside moisture from reaching the circuit board 12 and thus can
improve the moisture resistance of the device. The encapsulating
resin 28 is made of a resin material added with granular filler of
alumina or the like. Some of the possible resin materials that can
be used to form the encapsulating resin 28 are such thermosetting
resins as epoxy resins and such thermoplastic resins as acrylic
resins.
[0028] In this embodiment, to improve the heat dissipation from the
device as a whole, the encapsulating resin 28 coating the bottom
surface of the circuit board 12 is formed thinly to have a
thickness T1 of 0.5 mm or smaller. However, this structure poses a
difficulty in spreading the encapsulating resin all over the area
under the circuit board 12 during the process of resin
encapsulation. This embodiment, however, solves the problem by
using a mold with a special shape. More details of this solution
will be described later by referring to FIG. 6.
[0029] As FIGS. 1A and 1C show, not only does the encapsulating
resin 28 of this embodiment encapsulate the circuit board 12 but
also portions of the encapsulating resin 28 extend outwards from
the sides of the circuit board 12. Specifically, portions of the
encapsulating resin 28 extend outwards from the shorter sides of
the circuit board 12. In addition, the central portions of these
extended portions of the encapsulating resin 28 are depressed in a
planar view, and thereby depressed areas 32A and 32B are formed in
the central portions. The depressed areas 32A and 32B are used when
the hybrid integrated circuit device 10 is screwed to a heat sink
or to a mount surface.
[0030] In addition, as FIG. IA shows, recessed areas 30A and 30B
are formed respectively on the two sides of the depressed area 32A
whereas recessed areas 30C and 30D are formed respectively on the
two sides of the depressed area 32B.
[0031] The formation of the recessed areas 30A to 30D in the
encapsulating resin 28 can reduce the amount of the resin used for
the encapsulating resin 28. Consequently, the cost can be cut and
the hybrid integrated circuit 10 can be made lighter in weight. In
the meanwhile, the portions of the encapsulating resin 28 that
surround the recessed areas 30A to 30D have a thickness that is 1.0
mm or larger, which is large enough to give a mechanical strength
that enables the screwing of the hybrid integrated circuit 10 at
depressed areas 32A and 32B.
[0032] As FIG. 1C shows, not only do the recessed areas 30A and 30D
exist in portions at the two sides of the circuit board 12 but also
portions of the recessed areas 30A and 30D extend over parts of the
circuit board 12. Such a structure of the recessed areas 30A and
30D allows further reduction of the amount of the encapsulating
resin 28 needed for the encapsulation of the hybrid integrated
circuit 10. The other recessed areas 30B and 30C share the feature
and the effect.
[0033] In addition, an inner side of each of the recessed areas 30A
and 30D is not a single plane but has a step-like structure. With
this step-like structure, the cure shrinkage of the encapsulating
resin 28 coating the top surface of the circuit board 12 can be
caused dispersedly in surfaces with different angles of the
encapsulating resin 28, and thereby the deformation of the circuit
board 12 caused by this cure shrinkage can be reduced.
[0034] The structure of the hybrid integrated circuit device 10 is
described further by referring to FIG. 2. FIG. 2A is a perspective
view illustrating the hybrid integrated circuit device 10 of FIG.
IA upside down. FIG. 2B is a sectional view taken along the line
B-B' in FIG. 2A. FIG. 2C is a top plan view illustrating the
depressed area 32B and its vicinity shown in FIG. 2A.
[0035] As FIG. 2A shows, cutaway portions 33 are formed by
partially cut away the four corners of the encapsulating resin 28.
To be more specific, each of the upper corner portions and its
vicinity is cut away to form each cut away portion 33. Each cutaway
portion 33 has a cuboid shape formed by cutting away each corner of
the encapsulating resin 28 into that shape. The formation of the
cutaway portions 33 in the corners of the encapsulating resin 28
can prevent damages, such as cracks, of the encapsulating resin 28
even when an impact or the like is applied to the corners of the
encapsulating resin 28.
[0036] As FIG. 2A to 2C show, peripheral edge portions 46 are
formed in a way that portions of the encapsulating resin 28 around
the bottom ends of the depressed areas 32A and 32B are extended
inward of the depressed areas 32A and 32B. In a planar view, each
of the depressed areas 32A and 32B has a rectangular shape with
rounded corners. The inner end portion of each peripheral edge
portion 46 has a shape of a portion of a circle or of an ellipse
corresponding to the shape of the columnar screw to be inserted in
this depressed area 32A or 32B.
[0037] To put it differently, in the sectional view of FIG. 2B, the
areas above the peripheral edge portions 46 and indicated by the
dashed-dotted lines are removed. In order to simplify the external
shape of the encapsulating resin 28, the side-surface portions of
the encapsulating resin 28 can be extended to the positions aligned
with the inner end portions of the peripheral edge portions 46,
without the peripheral edge portions 46 additionally formed. In
this embodiment, however, the encapsulating resin 28 is formed with
the shape shown in FIG. 2B so that the bottom surface (the upper
surface in FIG. 2B) of the circuit board 12 can be coated thinly
with the encapsulating resin 28. More details of this feature will
be described later by referring to FIG. 6C.
[0038] The configuration of the circuit board that is built in the
hybrid integrated circuit device 10 is described below by referring
to FIG. 3. FIG. 3A is a perspective view illustrating the circuit
board 12. FIG. 3B is a sectional view taken along the line B-B' in
FIG. 3A. FIG. 3C is a sectional view taken along the line C-C' in
FIG. 3A.
[0039] As FIG. 3A shows, the circuit board 12 has a rectangular
shape with a first side-edge 12A, a second side-edge 12B, a third
side-edge 12C, and a fourth side-edge 12D. The conductive pattern
16 with a predetermined shape is formed on the insulating layer
coating the top surface of the circuit board 12.
[0040] The conductive pattern 16 includes lands to which circuit
elements are connected and wirings that connect the lands to one
another. In addition, pads 26 formed with portions of the
conductive pattern 16 that are formed into pad-like shapes are
provided along the right-hand side-edge (i.e., third side-edge 12C)
of the circuit board 12. Furthermore, pads 27 are formed along the
fourth side-edge 12D located on the opposite side of the circuit
board 12 to the third side-edge 12C.
[0041] In circuit board 12, a side-surface shape of each of the
first side-edge 12A and the second side-edge 12B is different from
a side-surface shape of each of the third side-edge 12C and the
fourth side-edge 12D. Specifically, the first side-edge 12A and the
second side-edge 12B have a larger sloping surface on the lower
side than on the upper side, but the third side-edge 12C and the
fourth side-edge 12D have a larger sloping surface on the upper
side than on the lower side.
[0042] The side-surface shape of the first side-edge 12A and the
second side-edge 12B in the circuit board 12 are described below by
referring to FIG. 3B. Specifically, each of the four
above-mentioned side surfaces of the circuit board 12 includes a
first sloping surface 22 that extends continuously and obliquely
outwards from the top surface of the circuit board 12 and a second
sloping surface 24 that extends continuously and obliquely outwards
from the bottom surface of the circuit board 12. In each of the
first side-edge 12A and the second side-edge 12B, the second
sloping surface 24 has a width that is larger than the width of the
first sloping surface 22. For example, the second sloping surface
24 has a width L2 of 0.4 mm whereas the first sloping surface 22
has a width L1 of 0.1 mm. In addition, the second sloping surface
24 is longer than the first sloping surface 22 in the thickness
direction as well. For example, the 20 second sloping surface 24
has a length L4 in the thickness direction of 10.0 mm whereas the
first sloping surface 22 has a length L3 in the thickness direction
of approximately 0.2 mm. The circuit board 12 has a total thickness
L5 of, for example, 1.5 mm. This embodiment improves the fluidity
of the encapsulating resin 28 in the process of resin encapsulation
by forming the side surface of the first side-edge 12A and that of
the second side-edge 12B into the above-described shapes. More
details about this feature will be described later by referring to
FIG. 6A.
[0043] As FIG. 3C shows, the relative dimensions between the first
sloping surface 22 and the second sloping surface 24 in each of the
third side-edge 12C and the fourth side-edge 12D are opposite those
in each of the first side-edge 12A and the second side-edge 12B.
Specifically, the width and the thickness of the first sloping
surface 22 are greater than their respective counterparts of the
second sloping surface 24. For example, the first sloping surface
22 has a width L6 of approximately 0.4 mm, and a height L8 of
approximately 10.0 mm In addition, the second sloping surface 24
has a width L7 of approximately 0.1 mm, and a height L9 of
approximately 0.2 mm. Forming each of the third side-edge 12C and
the fourth side-edge 12D into the above-described shape has an
advantageous effect of preventing voids from occurring in the
encapsulating resin 28 under the bottom surface of the circuit
board 12 during the process of resin encapsulation. More details
about this feature will be described later by referring to FIG.
6B.
Second Embodiment: Method of Manufacturing Circuit Device
[0044] In this embodiment, a method of manufacturing the circuit
device with the above-described configuration is described by
referring to FIGS. 4 to 7.
[0045] Firstly, as FIG. 4 shows, grooves with a V-shaped cross
section are formed in both the top surface and the bottom surface
of a large-sized substrate 34. FIG. 4A is a perspective view
illustrating the substrate 34 in which the grooves are formed. FIG.
4B is a sectional view taken along the line B-B' in FIG. 4A. FIG.
4C is a sectional view taken along the line C-C' in FIG. 4A.
[0046] As FIG. 4A shows, the substrate 34 is a large-sized
substrate from which multiple circuit boards can be formed. Dicing
lines are drawn in a lattice shape corresponding to the size of the
circuit board to be formed from the substrate 34. A metal substrate
made of aluminum or the like is used as the substrate 34.
Alternatively, the substrate 34 may be made of a resin material
such as glass epoxy, or may be made of ceramics.
[0047] In the top surface of the substrate 34, first grooves 36 and
second grooves 38 are formed in a lattice shape. The second grooves
38 are shallower than the first grooves 36. In the bottom surface
of the substrate 34, third grooves 40 and fourth grooves 42 are
formed at positions such that the third grooves 40 correspond
respectively to the first grooves 36 and the fourth grooves 42
correspond respectively to the second grooves 38. The third grooves
40, which correspond respectively to the first grooves 36, are
shallower than the fourth grooves 42, which correspond respectively
to the second grooves 38.
[0048] In the top surface of the substrate 34, each single board
area 44 is defined as an area surrounded by the first grooves 36
and the second grooves 38. Identical conductive patterns (not
illustrated) are formed respectively in the board areas 44.
[0049] As FIG. 4B shows, at the border between every two adjacent
board areas 44, one of the second grooves 38 is formed from the top
surface and one of the fourth grooves 42 is formed from the bottom
surface. The second grooves 38 are shallower than the fourth
grooves 42. Specifically, each of the shallow second grooves 38 has
a width L20 of approximately 0.2 mm and a depth L21 of
approximately 0.2 mm. Each of the fourth grooves 42 formed from the
bottom surface of the substrate 34 has a width L24 of approximately
0.8 mm and a depth L23 of approximately 10.0 mm. Within the
dimension in the thickness direction of the substrate 34, the
portion left without any of the two grooves 38 and 43 has a
thickness L22 of approximately 0.4 mm.
[0050] As FIG. 4C shows, the first grooves 36 formed from the top
surface are deeper than the third grooves 40 formed from the bottom
surface. Note that the size of each first groove 36 may be the same
as that of each fourth groove 42 shown in FIG. 4B, and also that
the size of each third groove 40 may be the same as that of each
second groove 38 shown in FIG. 4B.
[0051] The substrate 34 with the grooves formed in the
above-described process is divided at positions where the grooves
are formed, and thereby individual board areas 44 are separated
from one another to be used as the circuit board 12. The dividing
of the substrate 34 may be done by bending the substrate 34 at each
border between every two adjacent board areas 44. Alternatively,
the substrate 34 may be cut with a cutting device such as a cutter,
and thereby the board areas 44 may be separated from one another to
be used as the circuit boards 12.
[0052] After the separation of the board areas 44 from one another,
circuit elements are connected to the conductive pattern 16 formed
on the top surface of each board area 44. Specifically, a
semiconductor element and/or a chip element shown in FIG. 1 may be
soldered to the conductive pattern 16.
[0053] Then as FIG. 5 shows, the circuit boards 12 to each of which
the circuit element 18 is connected are fixed to a lead frame 50.
The lead frame 50 is a metal plate made of copper or the like with
a thickness of approximately 0.1 mm and formed into a predetermined
shape, and includes a frame portion 52 and support portions 53. The
frame portion 52 has a frame shape, and forms the external shape of
the lead frame 50. Each support portion 53 bridges the lengthwise
sides of the frame portion 52. An uppermost unit 56 shown in FIG. 5
includes the leads 20 each of which has an end connected to the
frame portion 52 and also includes the leads 20 each of which has
an end connected to the corresponding support portion 53. The unit
56 herein refers to the plural leads 20 that form a single circuit
device. Linking portions 62 (tie bars) are provided to link
together the vicinities of the leading-end portions of the leads
20. The left-hand end portion and the right-hand end portion of
each linking portion 62 are connected to the frame portion 52.
Projection areas 58 are formed in the frame portion 52 by
projecting inwards some parts of the frame portion 52. The
projection areas 58 thus formed are the areas where the depressed
areas 32A and 32B shown in FIG. IA are to be formed.
[0054] In this manufacturing process, end portions of the leads 20
are soldered to the pads 26 and 27 provided on the top surface of
each circuit board 12. Thus each circuit board 12 is fixed to the
lead frame 50. In this embodiment, three circuit boards 12 are
fixed to the lead frame 50, and the next manufacturing process,
that is, the process of resin encapsulation is performed on the
circuit boards 12 in this state.
[0055] In FIG. 5, dashed-lined circles indicate the positions where
gates 82 are formed. The resin used in a later process of
encapsulating the circuit board 12 is introduced through each of
the gates 82. In the example shown in FIG. 5, two gates 82 are
formed at the two sides of each projection area 58, but only one of
the two gates 82 may be formed instead.
[0056] Then, as FIGS. 6 and 7 shows, each circuit board 12 is
encapsulated with resin. The resin encapsulation in this
manufacturing process is done by the transfer molding technique
using a set of molds.
[0057] The resin encapsulation performed in this manufacturing
process is described by referring to FIG. 6. FIG. 6A is a
perspective view illustrating the encapsulating resin 28 fabricated
in this manufacturing process. FIG. 6B is a sectional view
illustrating a set of molds taken along the line B-B' in FIG. 6A.
FIG. 6C is a sectional view illustrating the set of molds taken
along the line C-C' in FIG. 6A.
[0058] As FIG. 6B shows, a set of molds 66 used in this
manufacturing process includes an upper mold 68 and a lower mold
70. If the two molds 68 and 70 are brought into contact with each
other, a cavity 72 is formed as a gap between the two molds 68 and
70.
[0059] A guiding portion 76 is formed by projecting downwards a
portion of the upper mold 68 corresponding to the right-hand side
portion of the circuit board 12. The shape of the guiding portion
76 is formed by transferring the shape of the recessed area 30A
shown in FIG. 6A. To put it differently, the guiding portion 76 has
a protruding shape corresponding to the recessed shape of the
recessed area 30A. This feature is also applied to a guiding
portion 78 located in an area corresponding to the left-hand side
portion of the circuit board 12. The shape of the guiding portion
78 is formed by transferring the shape of the recessed area 30D
shown in FIG. 6A.
[0060] The lower end portion of the guiding portion 76 is
positioned below the level corresponding to the top surface of the
circuit board 12. This structure allows encapsulating resin 74 to
flow smoothly downwards in FIG. 6B along the guiding portion 76. In
addition, it is more preferable that the lower end of the guiding
portion 76 be positioned below the level corresponding to the upper
end of the second sloping surface 24 of the circuit board 12. This
structure has a larger effect of allowing the encapsulating resin
74 to flow along the guiding portion 76 to the area under the
circuit board 12.
[0061] The set of molds 66 has a gate 82, a runner 73, and an air
vent 71. The gate 82 is an opening through which the encapsulating
resin is introduced into the cavity 72. The runner 73 is a route
through which the encapsulating resin to be introduced into the
cavity 72 flows. The air vent 71 is a hole through which the air is
discharged from the cavity 72 to the outside of the set of the
molds 66. Either one gate 82 or two gates 82 are formed for each
single cavity 72 (see FIG. 5).
[0062] As FIG. 6C shows, protruding portions 84 and 85 are formed
in the lower mold 70. The shapes of the protruding portions 84 and
85 are formed by transferring the depressed areas 32A and 32B shown
in FIG. 6A. The top surfaces of the protruding portions 84 and 85
are in contact respectively with the bottom surfaces of the
projection areas 58 of the lead frame 50. The inner-side wall of
each of the protruding portions 84 and 85 is located on an inner
side of the corresponding projection area 58 of the lead frame 50.
A space 77 is formed between the top surface of the vicinity of the
inner-side end of the protruding portion 84 and the bottom surface
of the upper mold 68. The height of the space 77 is the same as the
thickness of each projection area 58 of the lead frame 50.
Likewise, a space 75 is formed between the top surface of the
vicinity of the inner-side end of the protruding portion 85 and the
bottom surface of the upper mold 68. The height of the space 75 is
the same as the thickness of each projection area 58 of the lead
frame 50. The peripheral edge portions 46 shown in FIG. 2A and the
like are formed by filling the spaces 75 and 77 with the
encapsulating resin.
[0063] Description is given below of a method of encapsulating the
circuit board 12 with resin by using the set of molds 66 with the
above-described structure.
[0064] Firstly, as FIG. 6B shows, the lead frame 50 to which the
circuit board 12 is fixed is placed on the top surface of the lower
mold 70. As FIG. 5 shows, three circuit boards 12 are fixed to the
lead frame 50 of this embodiment. The circuit boards 12 are set
individually in cavity areas formed in the lower mold 70.
[0065] In addition, the frame portion 52 of the lead frame 50 of
this embodiment is placed so that the frame portion 52 can close
the corresponding groove-shaped runner 73 formed in the lower mold
70. Thus, the bottom surface of the frame portion 52 of the lead
frame 50 becomes the ceiling of the frame portion 52.
[0066] Then, the upper mold 68 and the lower mold 70 are brought
into contact with each other. Thus, each circuit board 12 is set in
the corresponding cavity 72. In the meanwhile, the upper mold 68
and the lower mold 70 clamp the frame portions 52 of the lead frame
50, so that the position of each circuit board 12 within the
corresponding cavity 72 is determined. In addition, the top surface
of the circuit board 12 with the circuit elements mounted thereon
faces the internal wall of the upper mold 68. Furthermore, as FIG.
6C shows, the projection areas 58 of the lead frame 50 are brought
into contact with the internal walls of the protruding portions 84
and 85 of the lower mold and with the internal wall of the upper
mold 68.
[0067] Then, the encapsulating resin 74 either in a liquid state or
in a semi-solid state is introduced from an unillustrated pod
through both the runner 73 and the gates 82 into the cavity 72. The
encapsulating resin 74 is made of a thermosetting resin, such as an
epoxy resin, added with inorganic granular filler, such as alumina.
The encapsulating resin 74 is heated to be in a molten state before
being supplied to the set of molds 66.
[0068] Once the encapsulating resin 74 is introduced into the
cavity 72, the encapsulating resin 74 flows along the side surface
of the guiding portion 76, and then along the side surface of the
circuit board 12. After that, the encapsulating resin 74 is filled
into the gap left between the bottom surface circuit board 12 and
the internal wall of the lower mold 70. Once the filling of the
encapsulating resin 74 into this gap is finished, the encapsulating
resin 74 is introduced into the portion of the cavity 72 located
over the circuit board 12 to encapsulate, with resin, both the
circuit board 12 and the circuit elements mounted on the top
surface of the circuit board 12. As the resin encapsulation of this
manufacturing process progresses, the air in the cavity 72 is
discharged to the outside through the air vent 71 formed in the
opposite side of the set of molds 66 to the gates 82.
[0069] Once the inside of the cavity 72 is filled with the
encapsulating resin 74, the encapsulating resin 74 is heated and
cured in a heating-and-curing process. Then, the upper mold 68 and
the lower mold 70 are separated away from each other, so that the
circuit boards 12 each encapsulated with resin are taken out of the
set of molds 66. Once the process of resin encapsulation is
finished, the leads 20 of each unit 56 are separated from either
the frame portion 52 or the support portions 53 of the lead frame
50 as FIG. 5 shows. This separation is done by a punching process
using a die.
[0070] The hybrid integrated circuit device 10 whose structure is
shown m FIG. 1 is manufactured through the series of manufacturing
processes described above.
[0071] This embodiment is characterized in that the guiding portion
76 formed in the upper mold 68 of the set of molds 66 helps the
encapsulating resin 74 flow into the gap under the circuit board
12.
[0072] The guiding portion 76 provided in this embodiment directs
the flow of the encapsulating resin 74 towards the portion under
the circuit board 12. As described earlier, the guiding portion 76
is formed by projecting downwards a portion of the internal wall of
the upper mold 68 corresponding to the right-hand side portion of
the circuit board 12. The right-hand side surface of the guiding
portion 76 is a sloping surface that slopes inwards towards the
bottom. Accordingly, once introduced into the cavity 72, the
encapsulating resin 74 flows along the side surface of the guiding
portion 76 and thereby moves preferentially into the portion under
the circuit board 12.
[0073] In addition, the gap between the end portion of the guiding
portion 76 and the circuit board 12 is narrow, and a part of the
guiding portion 76 that is formed into a step-like shape is located
above the circuit board 12. Hence, the encapsulating resin 74
introduced into the cavity 72 is prevented from being introduced
into the space above the circuit board before the space under the
circuit board 12 is filled with the encapsulating resin 74.
[0074] In addition, the frame portion 52 of the lead frame 50 forms
a part of the runner 73 in this embodiment, and thus the gates 82
are located at higher positions than the circuit board 12. In this
embodiment, even under the conditions described above, the guiding
portion 76 forces the encapsulating resin 74 to flow downwards, and
thereby the space under the circuit board 12 is filled with the
encapsulating resin 74.
[0075] In addition, the circuit board 12 of this embodiment has
side surfaces with shapes that facilitate the downward flow of the
encapsulating resin 74. Specifically, as described earlier, each of
the side surfaces of the circuit board 12 includes the first
sloping surface 22 and the second sloping surface 24. In the side
surface of the circuit board 12 that the introduced encapsulating
resin 74 is brought into contact with, the second sloping surface
24 is larger than the first sloping surface 22. To put it
differently, the second sloping surface 24 has a larger area than
the first sloping surface 22.
[0076] Hence, the encapsulating resin 74 that has been introduced
through the gates 82 into the cavity 72 and has moved along the
guiding portion 76 moves further along the second sloping surface
24 of the circuit board 12 and then fills the gap between the
circuit board 12 and the lower mold 70. Accordingly, the
encapsulating resin 74 is introduced into the narrow gap under the
circuit board 12 without forming voids.
[0077] In addition, as FIG. 6C shows, the small distance between
each of the protruding portions 84 and 85 and the circuit board 12
in this embodiment prevents the encapsulating resin 74 having
flowed in the portion under the circuit board 12 from moving into
the portion above the circuit board 12. Specifically, the
protruding portions 84 and 85 are provided to form the depressed
areas 32A and 32B for screwing shown in FIG. 6A. So, if the
external shape of the encapsulating resin 28 needs to be
simplified, the inner-side ends of the protruding portions 84 and
85 have to be located at the same positions corresponding to the
inner-side ends of the projection areas 58 of the lead frame 50 so
that the shapes of the inner-side ends of the protruding portions
84 and 85 can be fit to the screws to be inserted. The structure
described above, however, widens each of the gaps formed between
the inner side surfaces of the protruding portions 84 and 86 and
the corresponding end portion of the circuit board 12, and the
wider gap thus created allows the encapsulating resin 74 that has
flowed in the portion under the circuit board 12 to move into the
portion above the circuit board 12. To prevent this movement of the
encapsulating resin 74, the internal walls of the protruding
portions 84 and 85 of this embodiment are located at positions
inward of the end portions of the projection areas 58 of the lead
frame 50. Accordingly, the gaps formed between the protruding
portions 84 and 85 and the corresponding end portions of the
circuit board 12 become narrower. Thus prevented is the movement of
the encapsulating resin 74 from the portion under the circuit board
12 to the portion above the circuit board 12 through the gaps.
Consequently, voids can be prevented from being formed in the
portion under the circuit board 12.
[0078] Another configuration to prevent the flow of the resin is
described below by referring to FIG. 7. FIG. 7A is a perspective
view illustrating a hybrid integrated circuit device 10 to be
manufactured. FIG. 7B is a sectional view of a set of molds 66 used
in the resin encapsulation taken along the line B-B' in FIG. 7A.
FIG. 7C is a sectional view of the set of molds 66 used in the
resin encapsulation taken along the line C-C' in FIG. 7A.
[0079] As FIG. 7B shows, each of guiding portions 76 and 78 is
formed by projecting downwards a portion of an upper mold 68. A
protruding portion 84 is formed by projecting upwards a portion of
a lower mold 70. The protruding portion 84 is located between
guiding portion 76 and the guiding portion 78. The guiding portions
76 and 78 are used to form respectively recessed areas 30C and 30D
shown in FIG. 7A. The protruding portion 84 is used to form a
depressed area 32B shown in FIG. 7A.
[0080] In this embodiment, protruding portions 86 are formed by
projecting inwards portions of the corners of the lower mold 70.
The protruding portions 86 are substantially cuboid-shaped portions
formed by making the four corners of the internal walls of the
lower mold 70 protrude inwards. The forming of the protruding
portions 86 allows cutaway portions 33 to be formed as shown in
FIG. 7A. The upper end of each protruding portion 86 is preferably
located above the lower ends of the guiding portions 76 and 78.
With this structure, a larger effect of guiding the flow of the
encapsulating resin in a manner described below can be
obtained.
[0081] The protruding portions 86 thus formed narrow the distances
between the internal walls of the lower mold 70 and each of the
guiding portions 76 and 78 in the regions where the protruding
portions 86 are formed. Hence, the encapsulating resin 74 that has
flowed in the portion under the circuit board 12 (see FIG. 6B) is
prevented from moving into the upper portion of the cavity through
the gaps between each of the guiding portion 76 and 78 and the
corresponding internal wall of the lower mold 70. Also with this
structure, the voids can be prevented from being formed in a
portion under the circuit board 12.
[0082] In this embodiment, as FIG. 7C shows, in each of the side
surfaces of the circuit board 12 corresponding to the third
side-edge 12C and the fourth side-edge 12D, a lower, second sloping
surface 24 is smaller than an upper, first sloping surface 22.
Hence, as the internal-wall side surfaces of the lower mold 70 are
sloping surfaces each of which becomes wider towards above, the
gaps between the internal-wall side surfaces of the lower mold 70
and the corresponding end portions of the circuit board 12 become
smaller. Accordingly, the encapsulating resin 74 that has been
filled in the portion under the circuit board 12 is prevented from
moving into the space above the circuit board 12 through the
gaps.
[0083] According to preferred embodiments of the invention, a
recessed area is formed at a side portion of the circuit board by
recessing a portion of the encapsulating resin in the thickness
direction. Hence, even if a fixation portion for screwing or the
like is formed in a portion of the encapsulating resin at a side of
the circuit board, the necessary amount of the encapsulating resin
can be reduced and the cost can be reduced as well.
[0084] In addition, the providing of the recessed area at a side of
the circuit board has the following effect. Even if a stress is
generated by the curing by heating of the encapsulating resin
coating the top surface of the circuit board, the circuit board 12
is reinforced by the recessed area. Accordingly, the warpage of the
circuit board by the stress can be avoided.
[0085] In addition, concerning the manufacturing method, as the
guiding portions to guide the flow of the encapsulating resin
introduced through the gates in the process of resin encapsulation
are provided at the two sides of the circuit board, the
encapsulating resin guided by the guiding portion flows into the
portion under the circuit board. Hence, even if the gap between the
internal wall of the mold and the bottom surface of the circuit
board is small, the small gap is preferentially filled with the
encapsulating resin. Accordingly, the voids can be prevented from
being formed in the portion under the circuit board.
* * * * *