U.S. patent application number 11/810724 was filed with the patent office on 2007-10-25 for semiconductor device using semiconductor chip.
This patent application is currently assigned to ROHM CO., LTD.. Invention is credited to Shinji Isokawa, Tomoji Yamaguchi.
Application Number | 20070246731 11/810724 |
Document ID | / |
Family ID | 27806946 |
Filed Date | 2007-10-25 |
United States Patent
Application |
20070246731 |
Kind Code |
A1 |
Isokawa; Shinji ; et
al. |
October 25, 2007 |
Semiconductor device using semiconductor chip
Abstract
A semiconductor device includes an insulating substrate 2 having
an obverse surface formed with a die pad 3, a rectangular
semiconductor chip 7 such as an LED chip bonded to the die pad with
a die bonding material 10, and a molded portion 9 made of a
synthetic resin for packaging the semiconductor chip. The die pad 3
may be rectangular with dimensions close to those of the
semiconductor chip or circular with a diameter close to the
diagonal dimension of the semiconductor chip, whereby the
positioning and orienting of the semiconductor chip can be
accurately performed in bonding the semiconductor chip.
Inventors: |
Isokawa; Shinji; (Kyoto-shi,
JP) ; Yamaguchi; Tomoji; (Kyoto, JP) |
Correspondence
Address: |
HAMRE, SCHUMANN, MUELLER & LARSON, P.C.
P.O. BOX 2902
MINNEAPOLIS
MN
55402-0902
US
|
Assignee: |
ROHM CO., LTD.
Kyoto-shi
JP
|
Family ID: |
27806946 |
Appl. No.: |
11/810724 |
Filed: |
June 7, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10506826 |
Sep 7, 2004 |
7242033 |
|
|
PCT/JP03/01994 |
Feb 24, 2003 |
|
|
|
11810724 |
Jun 7, 2007 |
|
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Current U.S.
Class: |
257/99 ;
257/E23.07; 257/E33.001 |
Current CPC
Class: |
H01L 2924/00 20130101;
H01L 2924/00014 20130101; H01L 2224/48247 20130101; H01L 2924/00
20130101; H01L 2224/32225 20130101; H01L 2224/48227 20130101; H01L
2224/05599 20130101; H01L 2924/00012 20130101; H01L 2224/48227
20130101; H01L 2924/00012 20130101; H01L 2924/00014 20130101; H01L
2924/00015 20130101; H01L 2224/32225 20130101; H01L 2924/00
20130101; H01L 2224/73265 20130101; H01L 2224/48465 20130101; H01L
2224/451 20130101; H01L 2224/92247 20130101; H01L 2224/32245
20130101; H01L 2924/00 20130101; H01L 2924/00 20130101; H01L
2224/45099 20130101; H01L 2224/32245 20130101; H01L 2224/73265
20130101; H01L 2924/00012 20130101; H01L 2924/00012 20130101; H01L
2224/32225 20130101; H01L 2924/00 20130101; H01L 2224/48091
20130101; H01L 2224/48091 20130101; H01L 2224/45015 20130101; H01L
2224/32245 20130101; H01L 2224/48227 20130101; H01L 2224/48247
20130101; H01L 2924/207 20130101; H01L 2924/00012 20130101; H01L
2224/48247 20130101; H01L 2224/48227 20130101; H01L 2224/48227
20130101; H01L 2224/48091 20130101; H01L 2924/12041 20130101; H01L
2924/01005 20130101; H01L 24/73 20130101; H01L 2924/01082 20130101;
H01L 2224/92247 20130101; H01L 2924/00014 20130101; H01L 2924/0105
20130101; H01L 2924/014 20130101; H01L 33/62 20130101; H01L
2224/73265 20130101; H01L 2224/32245 20130101; H01L 2224/48247
20130101; H01L 24/29 20130101; H01L 23/49838 20130101; H01L
2224/48465 20130101; H01L 2224/48465 20130101; H01L 2224/48465
20130101; H01L 2924/00014 20130101; H01L 2224/27013 20130101; H01L
2924/00014 20130101; H01L 24/83 20130101; H01L 33/38 20130101; H01L
2224/451 20130101; H01L 2224/48091 20130101; H01L 2224/83192
20130101; H01L 2224/83385 20130101; H01L 2924/181 20130101; H01L
2224/451 20130101; H01L 24/32 20130101; H01L 2224/92247 20130101;
H01L 2924/181 20130101; H01L 24/48 20130101; H01L 2224/83192
20130101; H01L 2924/01078 20130101; H01L 33/486 20130101; H01L
2224/83192 20130101; H01L 2224/48465 20130101; H01L 2924/01033
20130101; H01L 2224/73265 20130101; H01L 2924/01006 20130101; H01L
2224/48465 20130101; H01L 2224/83143 20130101; H01L 2224/32225
20130101; H01L 2924/01023 20130101; H01L 2224/73265 20130101; H01L
2924/00014 20130101 |
Class at
Publication: |
257/099 ;
257/E33.001 |
International
Class: |
H01L 33/00 20060101
H01L033/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 8, 2002 |
JP |
2002-63684 |
Aug 16, 2002 |
JP |
2002-237349 |
Claims
1-11. (canceled)
12. A semiconductor device comprising: an insulating substrate
having an obverse surface formed with a die pad made of a metal
film and a pair of electrode terminals made of a metal film; a
semiconductor chip which is square or generally square as viewed in
plan and bonded to an obverse surface of the die pad with a die
bonding material; and a molded portion made of a synthetic resin
for packaging the semiconductor chip; wherein the die pad is
circular as viewed in plan and has a diameter which approximates a
diagonal dimension of the semiconductor chip, wherein a narrow
patterned conductor made of a metal film is provided between the
die pad and one of the electrode terminals to integrally connect
the die pad and the electrode terminal to each other, the narrow
patterned conductor being positioned on a longitudinal centerline
of the insulating substrate; wherein the semiconductor chip has a
diagonal line located on the longitudinal centerline of the
insulating substrate.
13. The semiconductor device according to claim 12, wherein the
diameter of the die pad is 0.6 to 1.5 times the diagonal dimension
of the semiconductor chip.
14. The semiconductor device according to claim 12, wherein the
semiconductor chip comprises an LED chip, and wherein the molded
portion is light-permeable.
Description
[0001] This application is a divisional of U.S. application Ser.
No. 10/506,826, filed Sep. 7, 2004, which application is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a semiconductor device
using a semiconductor chip, and particularly to a semiconductor
device including a semiconductor chip bonded to a die pad and
packaged with a molded portion made of a synthetic resin.
[0004] 2. Description of the Related Arts
[0005] Generally, alight emitting diode lamp of the type described
above includes an insulating substrate in the form of a chip, on
which a die pad and a pair of first and second electrode terminals
all of which are made of a metal film are formed so that the die
pad is electrically connected to the first electrode terminal. The
device further includes a semiconductor chip bonded to the die pad
and electrically connected to the second electrode terminal.
[0006] To bond the semiconductor chip to the die pad electrically
connected to the first electrode terminal in the semiconductor
device, a thermally meltable die bonding material such as solder
paste is used. Specifically, an appropriate amount of such die
bonding material is applied to an upper surface of the die pad, and
then the semiconductor chip is placed on the die bonding material.
In this state, the die bonding material is once melted by heating
and then hardened.
[0007] Conventionally, although the die pad has a rectangular
configuration which is similar to the rectangular configuration of
the semiconductor chip, the die pad is made considerably larger
than the semiconductor chip to be bonded thereto, which causes the
problems described below.
[0008] In bonding the semiconductor chip to the die pad, it is
necessary to bond the semiconductor chip at or near the center of
the die pad. However, when the die bonding material applied to the
die pad is melted, the semiconductor chip is floated on the melted
die bonding material, and the die bonding material spreads largely
to all sides over the upper surface of the die pad. Therefore, in
accordance with the spreading of the die bonding material to all
sides, the semiconductor chip in the floated state moves along the
upper surface of the die pad to be away from the center. Thus, when
the die bonding material is hardened thereafter, the semiconductor
chip is fixed to the die pad at a position offset from the center.
Moreover, when the semiconductor chip is put on the die pad at an
offset position, the semiconductor chip is fixed at the offset
position of the die pad without correction.
[0009] Moreover, in bonding the semiconductor chip to the die pad,
it is necessary to arrange the semiconductor chip so that each of
the corners of the semiconductor chip is oriented in a
predetermined direction. However, since the semiconductor chip
floated on the melted die bonding material can rotate freely, each
of the corners cannot be oriented in a predetermined direction.
Thus, the semiconductor chip is fixed with the orientation of the
corners deviated.
[0010] The positional deviation from the center and deviation of
the corner orientation of the semiconductor chip may hinder the
connection of a metal wire to a predetermined electrode of the
semiconductor chip in electrically connecting the semiconductor
chip to the second electrode terminal by wire bonding or may cause
such a connection failure that an intermediate portion of the metal
wire comes into contact with the semiconductor chip. Further, to
package the semiconductor chip with a molded portion made of a
synthetic resin, the molded portion need be made relatively large
in view of the above-described two kinds of deviation, which leads
to an increase in size and weight of the semiconductor device.
[0011] Particularly, when the semiconductor device is an LED device
using a LED chip as a semiconductor chip, the position of the light
source and the directionality of light emitted from the LED chip
changes due to the positional deviation from the center and
deviation of the corner orientation of the LED chip, so that
variation of the directionality of light is large.
DISCLOSURE OF THE INVENTION
[0012] An object of the present invention is to solve the problems
described above.
[0013] According to a first aspect of the present invention, there
is provided a semiconductor device comprising: an insulating
substrate having an obverse surface formed with a rectangular die
pad made of a metal film and a pair of electrode terminals made of
a metal film; a rectangular semiconductor chip bonded to an obverse
surface of the die pad with a die bonding material; and a molded
portion made of a synthetic resin for packaging the semiconductor
chip. The rectangle of the die pad has a length and a width which
are 0.50 to 1.50 times the length and the width of the rectangle of
the semiconductor chip, respectively.
[0014] By making the length and the width of the rectangle of the
die pad 0.50 to 1.50 times the length and the width of the
rectangle of the semiconductor chip, the following advantages are
provided. When the semiconductor is placed on the die pad, the side
surfaces of the semiconductor chip may not be in parallel with the
side surfaces of the die pad or the semiconductor chip may be
offset from the center of the die pad. Even in such a case, the
surface tension of the die bonding material acts simultaneously to
each side of the semiconductor chip and each side of the die pad.
As a result, as will be described later in detail, by self
alignment due to the surface tension, the semiconductor chip is
automatically corrected so that each side of the semiconductor chip
become parallel or generally parallel with a respective side of the
die pad, or each of the corners of the semiconductor chip is
oriented constantly in a predetermined direction. Further, the LED
chip is automatically corrected to locate at or near the center of
the die pad.
[0015] Thus, in bonding the semiconductor chip to the die pad on
the insulating substrate, by the self alignment due to the surface
tension of the die bonding material, the deviation of the
semiconductor chip from the center of the die pad can be reduced,
and each of the corners of the semiconductor chip can be oriented
accurately in a predetermined direction so that each side of the
semiconductor chip become parallel or generally parallel with a
respective side of the die pad. Therefore, the molded portion for
packaging the semiconductor chip can be made smaller as compared
with that of the prior art, whereby the size and weight of the
semiconductor device can be reduced.
[0016] Particularly, in the first aspect, when the semiconductor
device is a chip-type LED device including an LED chip as the
semiconductor chip and a light-permeable molded portion, the change
of the light source position and the directionality can be
suppressed, whereby variation of the directionality can be
reduced.
[0017] Further, in the first aspect, the die pad may have a side
surface integrally formed with a narrow extension projecting
outward from the die pad. With such an arrangement, part of the die
bonding material applied onto the die pad spreads onto the obverse
surface of the narrow extension. As a result, the thickness of the
die bonding material on the obverse surface of the die pad can be
reduced while the self alignment by the die bonding material is
assured. Therefore, the float height from the die pad, height
variation and inclination of the semiconductor chip can be reduced,
and the amount of sinking of the semiconductor chip in the die
bonding material is also reduced. Thus, short-circuiting in the
semiconductor chip can be suppressed. Moreover, when the
semiconductor chip is an LED chip, the reduction of the amount of
light emitted from the LED chip can be prevented.
[0018] Further, in the first embodiment, the die pad may be formed
with a recess of a size insufficient to receive the semiconductor
chip. With such an arrangement, part of the die bonding material
applied to the obverse surface of the die pad enters the recess. As
a result, the thickness of the die bonding material on the obverse
surface of the die pad can be reduced while the self alignment by
the die bonding material is assured. Therefore, the float height
from the die pad, height variation and inclination of the
semiconductor chip can be reduced, and the amount of sinking of the
semiconductor chip in the die bonding material is also reduced.
Thus, short-circuiting in the semiconductor chip can be
suppressed.
[0019] When the provision of the narrow extension is combined with
the provision of the recess, higher advantages can be obtained than
when only either one of the above is provided.
[0020] According to a second aspect of the present invention, there
is provided a semiconductor device comprising: an insulating
substrate having an obverse surface formed with a die pad made of a
metal film and a pair of electrode terminals made of a metal film;
a semiconductor chip which is square or generally square as viewed
in plan and bonded to an obverse surface of the die pad with a die
bonding material; and a molded portion made of a synthetic resin
for packaging the semiconductor chip. The die pad is circular as
viewed in plan and has a diameter which approximates the diagonal
dimension of the semiconductor chip, and wherein a narrow patterned
conductor made of a metal film is provided between the die pad and
one of the electrode terminals to integrally connect the die pad
and the electrode terminal to each other.
[0021] With such an arrangement, a thermally meltable die bonding
material is applied to the obverse surface of the die pad, and then
the semiconductor chip is placed thereon. Thereafter, the entirety
is heated to a temperature above the melting point of the die
bonding material.
[0022] By the heating, the die bonding material is melted, so that
the semiconductor chip is floated on the melted die bonding
material. At this time, the melted die bonding material spreads,
while alloying, over the entire obverse surface of the die pad and
also over the bottom surface and each of four side surfaces of the
semiconductor chip. Thus, surface tension of the melted die bonding
material acts between the circumferential edge of the die pad and
each of the four side surfaces of the semiconductor chip.
[0023] In this case, since the semiconductor chip is square or
generally square while the die pad is circular with a diameter
which approximates the diagonal dimension of the semiconductor
chip, the semiconductor chip floating on the melted die bonding
material undergoes self alignment for moving the LED chip to a
position where the surface tension acts equally onto each of the
four side surfaces of the semiconductor chip. Therefore, even when
the semiconductor is placed at a position offset from the center of
the die pad, the position is automatically corrected by self
alignment due to the surface tension for the four sides so that the
semiconductor chip is located at or near the center of the die
pad.
[0024] Further, part of the melted die bonding material spreads
also toward the narrow patterned conductor made of a metal film and
connecting the die pad to one of the electrode terminals.
Therefore, a bulged portion projecting on to the narrow patterned
conductor is formed at the outer circumference of the molten solder
paste, and surface tension acts also between the side surfaces of
the semiconductor chip and the bulged portion spreading onto the
narrow patterned conductor. Therefore by the self alignment due to
the behavior of the solder paste to make the surface tension act
equally onto each of the side surfaces, the semiconductor chip
floating on the melted die bonding material is automatically
corrected so that one of the four corners of semiconductor chip is
oriented toward the narrow patterned conductor.
[0025] In this way, the semiconductor chip is automatically
corrected (self alignment) to locate at or near the center of the
die pad, and at the same time, automatically corrected (self
alignment) so that one of the four corners of the semiconductor
chip is oriented toward the narrow patterned conductor.
[0026] By the subsequent hardening of the melted die bonding
material by cooling, the semiconductor chip is bonded at or near
the center of the die pad connected to one of the electrode
terminals, with one of the corners of the semiconductor chip
oriented toward the narrow patterned conductor connected to the die
pad so that each of the corners is constantly oriented in a
predetermined direction. Therefore, it is possible to reduce the
positional deviation of the semiconductor chip from the center of
the die pad and the deviation of the corner orientation of the
semiconductor chip.
[0027] As a result, the possibility of a connection failure, which
may occur in electrically connecting the semiconductor chip to one
of the electrode terminals by wire bonding using a metal wire, is
reliably reduced. Further, when the semiconductor chip is to be
packaged with a molded portion made of a synthetic resin, the
molded portion can be made smaller by as much as the above two
kinds of deviation is reduced, whereby the size and weight of the
semiconductor device can be reduced.
[0028] As noted above, the self alignment to locate the
semiconductor chip at or near the center of the die pad and to
orient the semiconductor chip so that one of the corners is
oriented toward the narrow patterned conductor can be reliably
achieved by making the diameter of the die pad 0.6 to 1.5 times the
diagonal dimension of the semiconductor chip.
[0029] In the second aspect, the die pad may be arranged between
the paired electrode terminals arranged on a generally straight
line, and the narrow patterned conductor may be arranged to extend
from the circumference of the die pad at a position deviating by 45
degrees from the line of the electrode terminals. With such an
arrangement, when the die bonding material is melted, one of the
corners of the semiconductor chip is oriented toward the patterned
conductor at the 45 degree position. Therefore, the semiconductor
chip can be bonded so that, among the four sides of the
semiconductor chip, a pair of opposite sides extend parallel or
generally parallel with the line of the electrode terminals while
the other pair of opposite sides extend perpendicularly or
generally perpendicularly to the line of the electrode terminals.
Therefore, the width and the length of the semiconductor device can
be made smaller than when the four sides of the semiconductor chip
are inclined relative to the line of the electrode terminals.
Accordingly, the size and weight of the semiconductor device can be
advantageously reduced.
[0030] In the second aspect again, when the semiconductor device is
a chip-type LED device including an LED chip as the semiconductor
chip and a light-permeable molded portion, the change of the light
source position and the directionality can be suppressed, whereby
the variation of the directionality can be reduced.
[0031] In the second aspect again, the die pad may be formed with a
recess of a size insufficient to receive the semiconductor chip,
similarly to the first aspect. With such an arrangement, the
variation of the float height of the semiconductor chip from the
die pad as well as the inclination of the semiconductor chip can be
reduced, and short-circuiting in the semiconductor chip can be
suppressed.
[0032] According to a third aspect of the present invention, there
is provided a semiconductor device comprising: a die pad made of a
metal plate and a pair of electrode terminals made of a metal
plate; a semiconductor chip which is square or generally square as
viewed in plan and bonded to the die pad with a die bonding
material; and a molded portion made of a synthetic resin for
packaging the semiconductor chip. The die pad is circular as viewed
in plan and has a diameter which approximates the diagonal
dimension of the semiconductor chip, and a narrow patterned
conductor made of a metal plate is provided between the die pad and
one of the electrode terminals to integrally connect the die pad
and the electrode terminal to each other. With such an arrangement,
a semiconductor device which does not utilize an insulating
substrate but utilizes a metal plate is provided.
[0033] Similarly to the second aspect, the following arrangements
are also applicable to the third aspect: [0034] i) to make the
diameter of the die pad 0.6 to 1.5 times the diagonal dimension of
the semiconductor chip; [0035] ii) to arrange the die pad between
the paired electrode terminals arranged on a generally straight
line and to arrange the narrow patterned conductor so as to extend
from the circumference of the die pad at a position deviating by 45
degrees from the line of the electrode terminals; and [0036] iii)
to make the semiconductor device a chip-type LED device including
an LED chip as the semiconductor chip and a light-permeable molded
portion.
[0037] Other objects, features and advantages of the present
invention will become clearer from the description of the
embodiments given below with reference to accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] FIG. 1 is a longitudinal sectional view showing a chip-type
LED device according to a first embodiment.
[0039] FIG. 2 is a plan view of FIG. 1.
[0040] FIG. 3 is a perspective view showing the chip-type LED
device according to the first embodiment.
[0041] FIG. 4 is an exploded perspective view of the first
embodiment.
[0042] FIG. 5 is a sectional view taken along lines V-V in FIG.
4.
[0043] FIG. 6 is a longitudinal sectional view showing an LED chip
bonded to an insulating substrate in the first embodiment.
[0044] FIG. 7 is a plan view of FIG. 6.
[0045] FIG. 8 is a perspective view showing a first variation of
the first embodiment.
[0046] FIG. 9 is a perspective view showing a second variation of
the first embodiment.
[0047] FIG. 10 is a perspective view showing a third variation of
the first embodiment.
[0048] FIG. 11 is a perspective view showing a fourth variation of
the first embodiment.
[0049] FIG. 12 is a sectional view taken along lines XII-XII in
FIG. 11.
[0050] FIG. 13 is a longitudinal sectional view showing a chip-type
LED device according to a second embodiment.
[0051] FIG. 14 is a plan view of FIG. 13.
[0052] FIG. 15 is an exploded perspective view showing the
chip-type LED device according to the second embodiment.
[0053] FIG. 16 is a sectional view taken along lines XVI-XVI in
FIG. 15.
[0054] FIG. 17 is enlarged view showing the principal portion of
FIG. 14.
[0055] FIG. 18 is a sectional view taken along lines XVIII-XVIII in
FIG. 17.
[0056] FIG. 19 is a sectional view taken along lines XIX-XIX in
FIG. 17.
[0057] FIG. 20 is a plan view showing a variation of the second
embodiment.
[0058] FIG. 21 is an exploded perspective showing a chip-type LED
device according to a third embodiment.
[0059] FIG. 22 is a plan view of FIG. 21.
[0060] FIG. 23 is a longitudinal sectional view showing a variation
of the third embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0061] FIGS. 1-7 show a first embodiment of the present
invention.
[0062] Indicated by the reference sign 1 in these figures is a
chip-type LED device as an embodiment of semiconductor device.
[0063] The chip-type LED device 1 includes an insulating substrate
2 in the form of a chip. The insulating substrate 2 has an upper
surface formed with a rectangular die pad 3 and a pair of terminal
electrodes 4, 5 all of which are made of a metal film, and a narrow
patterned conductor 6 made of a metal film and electrically
connecting the terminal electrode 4 to the die pad 3.
[0064] The chip-type LED device 1 further includes an LED chip 7
bonded to the upper surface of the die pad 3, a thin metal wire 8
connecting the LED chip 7 and the terminal electrode 5 by wire
bonding, and a molded portion 9 made of a light-permeable synthetic
resin such as a transparent resin for packaging the LED chip 6 and
the wiring pattern 6.
[0065] The paired terminal electrodes 4, 5 extend from the upper
surface onto an end surface and a lower surface of the insulating
substrate 2.
[0066] The bonding of the LED chip 7 onto the die pad 3 on the
insulating substrate 2 is performed as follows.
[0067] To mount the LED chip 7 which is a typical rectangular one
having a length L0 and a width W0, the length L1 and the width W1
of the die pad 3 are made equal or generally equal to the length L0
and the width W0 of the LED chip 7 so that the die pad becomes
congruent or generally congruent to the LED chip 7. In bonding, an
appropriate amount of solder paste H is applied to the upper
surface of the die pad 3, as shown in FIG. 3. Then, as shown in
FIG. 4, the LED chip 7 is placed on the solder paste H. Thereafter,
the solder paste in this state is heated to a temperature above the
melting point of the solder and then cooled for hardening.
[0068] As indicated by double-dashed lines in FIG. 5, when the
rectangular LED chip 7 is placed on the rectangular die pad 3, the
side surfaces of the LED chip 7 may not be in parallel with the
side surfaces of the die pad 3 or the LED chip 7 may be offset from
the center of the die pad 3. Even in such a case, with the above
arrangement, the surface tension of the molten solder acts
simultaneously to each side surface of the LED chip 7 and each side
surface of the die pad 3. As a result, by self alignment due to the
surface tension, the orientation of the LED chip 7 is automatically
corrected so that each side of the LED chip 7 become parallel or
generally parallel with a respective side of the die pad 3, and the
position of the LED chip 7 is automatically corrected so that the
LED chip 7 is accurately located at the center of the die pad
3.
[0069] By the hardening of the molten solder, the LED chip 7 is
fixed with the position corrected as described above.
[0070] Through the experiment by the inventors, it has been found
that the automatic correction by the self alignment due to the
surface tension of the molten solder is reliably achieved when the
length L1 and the width W1 of the rectangle of the die pad 3 are
0.50 to 1.50 times the length L0 and the width W0 of the rectangle
of the LED chip 7, preferably 0.65 to 1.35 times, and most
preferably 0.75 to 1.25 times. This holds true for bonding
materials other than solder paste such as conductive paste.
[0071] In this way, in die-bonding the LED chip 7 to the die pad 3
on the insulating substrate 2, the self alignment by the die
bonding material reduces the positional deviation of the LED chip 7
from the center of the die pad 3 while making each side surface of
the LED chip 7 parallel or generally parallel with a respective
side surface of the die pad 3. Therefore, the width of the
insulating substrate and the molded portion 9 for packaging the LED
chip 7 can be reduced as compared with that of the prior art
device, whereby the size and weight of the chip-type LED device 1
can be reduced. Further, the variation of directionality of light
emitted from the LED chip 6 can be reduced.
[0072] In the first embodiment, the patterned conductor 6 for
electrically connecting the die pad 3 to the first terminal
electrode 4 does not extend straight as indicated by double-dashed
lines in FIG. 2 but extends obliquely as indicated by the solid
lines in FIG. 2, whereby the patterned conductor 6 is made
relatively long. With such an arrangement, the contact area between
the patterned conductor and the molded portion 9 packaging the
patterned conductor can be increased, whereby moisture in the
atmosphere, for example, is reliably prevented from entering
through the patterned conductor 6.
[0073] The number of the patterned conductor is not limited to one.
As shown in FIG. 7, two patterned conductors, i.e. the patterned
conductor 6 indicated by solid lines and a patterned conductor 6a
indicated by double-dashed lines may be provided.
[0074] FIG. 8 shows a first variation of the first embodiment.
[0075] In the first variation, each corner of the rectangular die
pad 3 formed on the upper surface of the insulating substrate 2 is
integrally formed with a narrow extension 3a which extends outward
from the die pad 3.
[0076] With this arrangement, when the solder paste H is applied
onto the die pad 3 and melted, part of the molten solder spreads
onto the obverse surface of the narrow extension 3a extending
continuously outward from the die pad 3. Therefore, the thickness
of the molten solder on the obverse surface of the die pad 3 can be
reduced while the self alignment due to the surface tension of the
molten solder is assured.
[0077] As a second variation of the first embodiment, the narrow
extension 3a may be provided at each side surface of the die pad 3,
as shown in FIG. 9. As a third variation of the first embodiment, a
plurality of narrow extensions 3a may be provided at one side
surface of the pad 3 so that the extensions also serve as the
patterned conductor 6, as shown in FIG. 10. In these variations
again, the thickness of the molten solder on the obverse surface of
the die pad 3 can be reduced while the self alignment due to the
surface tension of the molten solder is assured.
[0078] FIGS. 11 and 12 show a fourth variation of the first
embodiment.
[0079] In the fourth variation, the rectangular die pad 3 formed on
the upper surface of the insulating substrate 2 is formed with a
recess 3b of a size insufficient to receive the LED chip 7.
[0080] With such an arrangement, when the solder paste H applied to
the obverse surface of the die pad 3 is melted with the LED chip 7
placed thereon, part of the molten solder is received in the recess
3b. Therefore, the thickness of the molten solder on the obverse
surface of the die pad 3 can be reduced while the self alignment
due to the surface tension of the molten solder is assured.
[0081] FIGS. 13-19 show a second embodiment of the present
invention.
[0082] Indicated by the reference sign 11 in these figures is a
chip-type LED device. The chip-type LED device 11 includes an
insulating substrate 12 in the form of a chip. The insulating
substrate 12 has an upper surface formed with a die pad 13 made of
a metal film to have a circular configuration with a diameter D,
and a pair of terminal electrodes 14 and 15 made of a metal film
and provided on opposite sides of the die pad. The upper surface of
the insulating substrate 12 is further formed with a narrow
patterned conductor 16 made of a metal film and electrically
connecting the terminal electrode 14 to the die pad 13.
[0083] The chip-type LED device 11 further includes an LED chip 17
bonded to the upper surface of the die pad 13, a thin metal wire 18
connecting an electrode on the upper surface of the LED chip 17 to
the terminal electrode 15 by wire bonding, and a molded portion 19
made of a light-permeable synthetic resin such as a transparent
resin for packaging the LED chip 17, the narrow patterned conductor
16 and the metal wire 18 on the upper surface of the insulating
substrate 12. As viewed in plan, the LED chip 17 is square or
generally square with side length B.
[0084] The terminal electrodes 14, 15 extend from the upper surface
onto an end surface and a lower surface of the insulating substrate
12.
[0085] To bond the LED chip 17 onto the die pad 13 on the
insulating substrate 12, the diameter D of the die pad 13 is made
close to the diagonal dimension S of the square or generally square
LED chip 7.
[0086] In die bonding, an appropriate amount of solder paste H is
applied to the upper surface of the die pad 13, and then the LED
chip 7 is placed on the solder paste H, as shown in FIGS. 15 and
16.
[0087] In placing the LED chip 17, it is only necessary to put the
LED chip on the solder paste H, and it is unnecessary to accurately
position the LED chip at the center of the die pad 13 or orient
each corner of the LED chip 17 in a predetermined direction.
[0088] Thereafter, the entirety is heated to a temperature above
the melting point of the solder to melt the solder paste H and then
cooled to normal temperature for hardening the paste.
[0089] By the heating and melting of the solder paste H, the LED
chip 17 is floated on the molten solder paste H. At this time, the
molten solder paste H spreads, while alloying, over the entire
obverse surface of the die pad 13 and also over the bottom surface
and each of four side surfaces of the LED chip 17. Thus, surface
tension of the molten solder paste H acts between the
circumferential edge of the die pad 13 and each of the four side
surface of the LED chip 17.
[0090] In this case, since the LED chip 17 is square or generally
square while the die pad 13 is circular with a diameter D which
approximates the diagonal dimension S of the LED chip 17, the LED
chip 17 floating on the molten solder paste H undergoes self
alignment for moving the LED chip to a position where the surface
tension acts equally to each of the four side surfaces of the LED
chip. Therefore, even when the LED chip 17 is placed at a position
offset from the center of the die pad 13, the position is
automatically corrected by self alignment so that the LED chip is
located at or near the center of the die pad 13.
[0091] Further, as shown in FIGS. 17 and 18, part of the molten
solder paste H spreads also toward the narrow patterned conductor
16 connecting the die pad 13 to the electrode terminal 14.
Therefore, a bulged portion h projecting onto the narrow patterned
conductor 16 is formed at the outer circumference of the molten
solder paste H, and surface tension of the solder paste H acts also
between the side surfaces of the LED chip 17 and the bulged portion
h spreading onto the narrow patterned conductor 16. Therefore, by
the self alignment due to the behavior of the solder paste to make
the surface tension act equally onto each of the side surfaces, the
orientation of the LED chip 17 floating on the molten solder paste
H is automatically corrected so that one of the four corners of the
LED chip 17 is oriented toward the narrow patterned conductor
16.
[0092] In this way, as shown in FIGS. 17, 18 and 19, automatic
correction is performed so that the LED chip 7 is positioned at or
near the center of die pad 13 and one of the four corners of the
LED chip is oriented toward the narrow patterned conductor 16.
[0093] By the subsequent hardening of the solder paste H by
cooling, the LED chip 17 is bonded at or near the center of the die
pad 13 connected to the electrode terminal 14, with one of the
corners of the LED chip 17 oriented toward the narrow patterned
conductor 16 connected to the die pad 13 so that each of the
corners is constantly oriented in a predetermined direction.
[0094] Through the experiment by the inventors, it has been found
that the self alignment due to the surface tension of the molten
solder is reliably achieved when the diameter D of the die pad 13
is 0.6 (lower limit) to 1.5 (upper limit) times the diagonal
dimension S of the LED chip 17, and is more reliably achieved when
0.8 (lower limit) to 1.2 (upper limit) times.
[0095] Therefore, "a diameter close to a diagonal dimension of the
semiconductor chip" as set forth in the claims of the present
invention means the above-described range.
[0096] FIG. 20 shows a variation of the second embodiment.
[0097] In the chip-type LED device 11' of this variation, the die
pad 13' is arranged, as viewed in plan, on a center line C
connecting the electrode terminals 14', 15' provided at opposite
ends of the insulating substrate 12' to each other. Specifically,
as viewed in plan, the terminal electrode 14' and the terminal
electrode 15' are arranged on a straight line with the die pad 13'
interposed therebetween, and the narrow patterned conductor 16'
connecting the die pad 13' to the electrode terminal 14' is
arranged to extend from the circumference of the die pad 13 at a
position deviating by an angle .theta. (=45 degrees) from the
center line C connecting the electrode terminals 14' and 15' to
each other, i.e. from the line of the electrodes 14', 15'.
Similarly to the foregoing embodiments, an LED chip 17' is bonded
on the upper surface of the die pad 13' with solder paste H, and an
electrode on the LED chip 17' is connected to the electrode
terminal 15' by wire bonding using a metal wire 18'. The LED chip
17', the narrow patterned conductor 16' and the metal wire 18' on
the upper surface of the insulating substrate 12' are packaged with
a molded portion 19' made of a transparent synthetic resin.
[0098] With such an arrangement, when solder paste H applied to the
upper surface of the die pad 13' is melted with the LED chip 17'
placed thereon, self alignment due to the surface tension of the
solder paste H occurs so that the LED chip 17' is automatically
located at or near the center of the die pad 13', while, at the
same time, one of the corners is automatically oriented toward the
narrow patterned conductor 16'. As shown in FIG. 20, by
subsequently fixing the LED chip in this state, the LED chip 17'
can be bonded so that, among the four sides of the LED chip, a pair
of opposite sides extend parallel or generally parallel with the
center line C connecting the electrode terminals 14' and 15' to
each other, i.e. with the line of the electrode terminals 14', 15'
while the other pair of opposite sides extend perpendicularly or
generally perpendicularly to the center line C connecting the
electrode terminals 14' and 15' to each other. Therefore, the width
F and the length E of the chip-type LED device 11' can be made
smaller than in the structure shown in FIG. 14 in which the four
sides of the LED chip are inclined relative to the line of the
electrode terminals 14' and 15'.
[0099] FIGS. 21 and 22 show a third embodiment of the present
invention.
[0100] In the chip-type LED device 21 according to the third
embodiment, instead of the paired electrode terminals and the die
pad all of which comprise a metal film formed on an insulating
substrate, a pair of electrode terminals and a die pad all of which
comprise a relatively thick metal plate are provided, and the
insulating substrate is not used.
[0101] Specifically, both of the electrode terminal 25 and the
electrode terminal 24 connected to the circular die pad 23 via a
narrow patterned conductor 26 are made of a metal plate. Similarly
to the foregoing embodiments, an LED chip 27 is bonded on the upper
surface of the die pad 23 with solder paste H, and an electrode on
the LED chip 27 is connected to the electrode terminal 25 by wire
bonding using a metal wire 28. The LED chip 27, the narrow
patterned conductor 26 and the metal wire 28 are packaged with a
molded portion 29 made of alight-permeable synthetic resin such as
a transparent resin.
[0102] With such an arrangement, a chip-type LED 21 which does not
include an insulating substrate can be formed by using a metal
plate.
[0103] As shown in FIG. 23, in a variation of the third embodiment,
the electrode terminal 25 maybe elongated for direct connection to
the LED chip 27 instead of the connection to the LED chip 27 by
wire bonding using a metal wire 28, whereby the wire bonding using
a metal wire can be eliminated.
[0104] In the third embodiment again, it is preferable that the
diameter D of the die pad 23 is 0.6 (lower limit) to 1.5 (upper
limit) times the diagonal dimension of the LED chip 27, and more
preferably, 0.8 (lower limit) to 1.2 (upper limit) times the
diagonal dimension of the LED chip. Further, in the third
embodiment again, similarly to the variation of the second
embodiment shown in FIG. 20, the narrow patterned conductor 26 may
be arranged to extend from the circumference of the die pad 23 at a
position deviating by an angle .theta. (=45 degrees) from the
center line connecting the electrode terminals 24 and 25 to each
other., i.e. from the line of the electrodes 24, 25. In this case,
the width and length of the chip-type LED device 21 can be
shortened for size reduction.
[0105] In the foregoing embodiments, a chip-type LED device using
an LED chip is described as an example of semiconductor device.
However, the present invention is not limited thereto and is also
applicable to such a semiconductor device as a transistor in which
more than two electrode terminals are connected to a single
semiconductor chip, as well as to a diode having a structure
similar to that of the chip-type LED device.
* * * * *