U.S. patent application number 09/908810 was filed with the patent office on 2001-11-29 for resin-molded semiconductor device and method for manufacturing the same.
Invention is credited to Oida, Seishi, Suematsu, Nobuhiro, Yamaguchi, Yukio.
Application Number | 20010045640 09/908810 |
Document ID | / |
Family ID | 26364277 |
Filed Date | 2001-11-29 |
United States Patent
Application |
20010045640 |
Kind Code |
A1 |
Oida, Seishi ; et
al. |
November 29, 2001 |
Resin-molded semiconductor device and method for manufacturing the
same
Abstract
A semiconductor chip (15) is bonded on a die pad (13) of a
leadframe, and inner leads (12) are electrically connected to
electrode pads of the semiconductor chip (15) with metal fine wires
(16). The die pad (13), semiconductor chip (15) and inner leads are
molded with a resin encapsulant (17). However, no resin encapsulant
(17) exists on the respective back surfaces of the inner leads
(12), which protrude downward from the back surface of the resin
encapsulant (17) so as to be external electrodes (18). That is to
say, since the external electrodes (18) protrude, a standoff height
can be secured in advance for the external electrodes (18) in
bonding the external electrodes (18) to electrodes of a
motherboard. Thus, the external electrodes (18) may be used as
external terminals as they are, and no ball electrodes of solder or
the like need to be provided for the external electrodes (18).
Accordingly, this process is advantageous in terms of the number of
manufacturing process steps and the manufacturing costs.
Inventors: |
Oida, Seishi; (Kyoto-shi,
JP) ; Yamaguchi, Yukio; (Otsu-shi, JP) ;
Suematsu, Nobuhiro; (Kameoka-shi, JP) |
Correspondence
Address: |
NIXON PEABODY, LLP
8180 GREENSBORO DRIVE
SUITE 800
MCLEAN
VA
22102
US
|
Family ID: |
26364277 |
Appl. No.: |
09/908810 |
Filed: |
July 20, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09908810 |
Jul 20, 2001 |
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09341918 |
Jul 21, 1999 |
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6291274 |
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09341918 |
Jul 21, 1999 |
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PCT/JP98/00476 |
Feb 4, 1998 |
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Current U.S.
Class: |
257/692 ;
257/693; 257/787; 257/E21.504; 257/E23.037; 257/E23.124 |
Current CPC
Class: |
H01L 2224/48247
20130101; H01L 2924/3025 20130101; H01L 24/48 20130101; H01L
23/49503 20130101; H01L 21/565 20130101; H01L 2924/01079 20130101;
H01L 2924/15165 20130101; H01L 2224/16225 20130101; H01L 2924/16195
20130101; H01L 2224/45124 20130101; H01L 2924/01046 20130101; H01L
2224/16 20130101; H01L 2924/01078 20130101; H01L 2924/181 20130101;
H01L 2224/48091 20130101; H01L 2224/32014 20130101; H01L 21/566
20130101; H01L 2924/09701 20130101; H01L 2224/45144 20130101; H01L
2924/12041 20130101; H01L 2924/15153 20130101; H01L 21/568
20130101; H01L 2924/01028 20130101; H01L 23/3107 20130101; H01L
24/45 20130101; H01L 2924/01013 20130101; H01L 2924/14 20130101;
H01L 2224/48227 20130101; H01L 2924/01322 20130101; H01L 2924/0105
20130101; H01L 2924/15311 20130101; H01L 2224/45124 20130101; H01L
2924/00014 20130101; H01L 2224/45144 20130101; H01L 2924/00014
20130101; H01L 2224/48091 20130101; H01L 2924/00014 20130101; H01L
2924/12041 20130101; H01L 2924/00 20130101; H01L 2924/3025
20130101; H01L 2924/00 20130101; H01L 2924/181 20130101; H01L
2924/00012 20130101 |
Class at
Publication: |
257/692 ;
257/693; 257/787 |
International
Class: |
H01L 023/28; H01L
023/055 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 10, 1997 |
JP |
09-026487 |
Oct 7, 1997 |
JP |
09-274117 |
Claims
1. A resin-molded semiconductor device comprising: a semiconductor
chip having electrode pads; inner leads; connection members for
electrically connecting the electrode pads of the semiconductor
chip to the inner leads; and a resin encapsulant for molding the
semiconductor chip, the inner leads and the connection members
together, characterized in that the lower part of each said inner
lead, including at least part of the back surface thereof,
functions as an external electrode, the external electrode
protruding downward from the back surface of the resin
encapsulant.
2. The resin-molded semiconductor device of claim 1, further
comprising: a die pad for supporting the semiconductor chip
thereon; and support leads for supporting the die pad,
characterized in that each said support lead includes a depressed
portion for elevating the die pad above the inner leads.
3. The resin-molded semiconductor device of claim 1 or 2,
characterized in that a protrusion height of the external electrode
as measured from the back surface of the resin encapsulant is in
the range from 10 .mu.m to 40 .mu.m.
Description
TECHNICAL FIELD
[0001] The present invention relates to a resin-molded
semiconductor device, in which a semiconductor chip and a leadframe
are molded with a resin encapsulant, and to a method for
manufacturing such a device. In particular, the present invention
relates to a device with the back surface of the leadframe
partially exposed out of the resin encapsulant.
BACKGROUND ART
[0002] In recent years, in order to catch up with rapidly advancing
downsizing of electronic units, it has become increasingly
necessary to package semiconductor components for each of these
electronic units at a higher and higher density. Correspondingly,
sizes and thicknesses of semiconductor components have also been
noticeably reduced.
[0003] Hereinafter, a conventional resin-molded semiconductor
device will be described.
[0004] FIG. 23(a) is a plan view of a conventional resin-molded
semiconductor device, and FIG. 23(b) is a cross-sectional view of
the conventional resin-molded semiconductor device.
[0005] As shown in FIGS. 23(a) and 23(b), this conventional
resin-molded semiconductor device is of the type including external
electrodes on its back surface.
[0006] The conventional resin-molded semiconductor device includes
a leadframe consisting of: inner leads 201; a die pad 202; and
support leads 203 for supporting the die pad 202. A semiconductor
chip 204 is bonded onto the die pad 202 with an adhesive, and
electrode pads (not shown) of the semiconductor chip 204 are
electrically connected to the inner leads 201 with metal fine wires
205. And the die pad 202, semiconductor chip 204, inner leads 201,
support leads 203 and metal fine wires 205 are molded with a resin
encapsulant 6. In this structure, no resin encapsulant 206 exists
on respective back surfaces of the inner leads 201. In other words,
the respective back surfaces of the inner leads 201 are exposed and
respective lower parts of the inner leads 201, including these
exposed back surfaces, serve as external electrodes 207.
[0007] In such a resin-molded semiconductor device, the respective
back surfaces of the resin encapsulant 206 and those of the inner
leads 201 are both located in the same plane, and the die pad 202
is located above the inner leads 201. That is to say, by providing
depressed portions 208 for the support leads 203, the die pad 202
is elevated above the inner leads 201. Thus, after the device has
been molded with the resin encapsulant 206, a thin layer of the
resin encapsulant 206 is also formed on the back surface of the die
pad 202. In FIG. 23(a), the resin encapsulant 206 is illustrated as
being transparent such that the inside of the semiconductor device
can be looked through. In FIG. 23(a), the semiconductor chip 204 is
indicated by the dashed line and the illustration of the metal fine
wires 205 is omitted.
[0008] Also, conventionally, to secure a required standoff height
from the back surface of the resin encapsulant 206 in bonding the
external electrodes to the electrodes of a motherboard such as a
printed wiring board, on which a resin-molded semiconductor device
is mounted, ball electrodes 209 of solder are attached to the
external electrodes 207 as shown in FIG. 24. After the standoff
height has been secured by these ball electrodes 209, the device is
mounted onto the motherboard.
[0009] Hereinafter, a method for manufacturing the conventional
resin-molded semiconductor device will be described with reference
to the drawings. FIGS. 25 through 27 are cross-sectional views
illustrating a manufacturing process for the conventional
resin-molded semiconductor device.
[0010] First, as shown in FIG. 25, a leadframe 210, including the
inner leads 201 and die pad 202, is prepared. It is noted that the
die pad 202 is actually supported by the support leads, but the
illustration of the support leads is omitted in FIG. 25. Depressed
portions are formed in the support leads and the die pad 202 is
elevated above the plane on which the inner leads 201 are located.
The leadframe 210 does not include any tie bar used for preventing
the resin encapsulant from flowing out during resin
encapsulation.
[0011] Next, as shown in FIG. 26, the semiconductor chip 204 is
bonded, with an adhesive, to the die pad 202 of the lead-frame
prepared. This process step is called "die bonding".
[0012] Then, as shown in FIG. 27, the semiconductor chip 204, which
has been bonded onto the die pad 202, is electrically connected to
the inner leads 201 via the metal fine wires 205. This process step
is called "wire bonding". As the metal fine wires 205, aluminum
(Al) or gold (Au) fine wires may be appropriately used, for
example.
[0013] Subsequently, as shown in FIG. 28, the die pad 202,
semiconductor chip 204, inner leads 201, support leads and metal
fine wires 205 are molded with the resin encapsulant 206. In this
case, the leadframe, on which the semiconductor chip 204 has been
bonded, is introduced into a molding die assembly and
transfer-molded. In particular, resin encapsulation is performed
with the back surface of the inner leads 201 in contact with an
upper or lower die of the die assembly.
[0014] Finally, the ends 211 of the inner leads 201, protruding
outward from the resin encapsulant 206, are cut off after the resin
encapsulation. By performing this cutting process step, the end
faces of the inner leads 201 cut off are substantially flush with
the side faces of the resin encapsulant 6 and the respective lower
parts of the inner leads 201 are used as external electrodes
207.
[0015] In the manufacturing process of this conventional
resin-molded semiconductor device, the resin encapsulant 206 might
overflow from the edges of the inner leads 201, reach the back
surfaces thereof and thereby form resin bur thereon (overflowing
resin) during the resin encapsulation process step. Thus, a water
jet process step is introduced for blowing off the resin bur after
the resin encapsulation process step and before the process step of
cutting off the inner leads 201.
[0016] Also, if necessary, ball electrodes of solder are formed on
the lower surfaces of the external electrodes 207, thereby
completing the resin-molded semiconductor device shown in FIG. 24.
As another alternative, a solder plating layer is sometimes formed
instead of the solder balls.
PROBLEMS TO BE SOLVED
[0017] The conventional resin-molded semiconductor device, however,
has the following drawbacks. First, since the lower surfaces of the
external electrodes 207 are located in substantially the same plane
as that of the resin encapsulant 206 on the back of the
semiconductor device, no standoff height from the resin encapsulant
206 can be obtained. Thus, the device must be mounted onto a
motherboard with the ball electrodes 209 of solder interposed
therebetween. Accordingly, mounting cannot be carried out
efficiently.
[0018] In addition, during the resin encapsulation step of the
conventional process for manufacturing a resin-molded semiconductor
device, a leadframe, on which a semiconductor chip has been bonded,
is introduced into a molding die assembly and then molded with a
resin by pressing the inner leads against the surface of the lower
die such that the leads closely contact the die. Even so, there
occurs a problem that the resin encapsulant reaches the back
surface of the inner leads to form a resin bur (overflowing resin)
on the surface of the external electrodes.
[0019] FIG. 30 is a partial plan view illustrating, on a larger
scale, the external electrodes 207 and their surroundings on the
back of the semiconductor device as illustrated within the circle
in FIG. 23(a). As shown in FIG. 30, resin bur 206a is sometimes
formed on the respective lower surfaces of the external electrodes
207 during the conventional resin encapsulation process step. That
is to say, the resin encapsulant 206 reaches the lower surfaces of
the external electrodes 207 to form the resin bur 206a thereon
during the resin encapsulation process step. In other words, part
of each external electrode 207 is buried within the resin
encapsulant 206.
[0020] Thus, a water jet process step has heretofore been
introduced to blow off the resin bur 206a on the external
electrodes 207. However, such a water jet process step is very
troublesome and is contradictory to the demand on a process
simplification to manufacture resin-molded semiconductor devices in
high volume or on a reduction in number of process steps. That is
to say, the formation of the resin bur is a non-negligible factor
interfering with such simplification of manufacturing process.
[0021] A leadframe for a general-purpose resin-molded semiconductor
device currently used is ordinarily made of copper (Cu) or Alloy
42. This material is plated with nickel (Ni) as an undercoat layer
and then plated with palladium (Pd) and gold (Au). In the
conventional process, however, if the resin bur is blown off with
high-pressure water jet during the water jet process step
introduced to remove the resin bur, then not only the resin bur,
but also soft metal plating peel off with the water jet. Also,
serious quality control problems, like deposition of impurities,
might happen.
[0022] To avoid this problem, various measures can be taken, e.g.,
the leadframe may be plated after the water jet process step is
over. However, in such a case, a metal layer pre-plating treatment
(or a preparatory plating treatment) cannot be performed, i.e., the
leadframe cannot be plated prior to the resin encapsulation process
step. Accordingly, the plating process step cannot be performed
efficiently, thus further interfering with the simplification of
manufacturing process. Also, such a measure is not preferable in
terms of the reliability of a resin-molded semiconductor device,
either.
[0023] An object of this invention is providing a resin-molded
semiconductor device and a method for manufacturing the same, which
can meet the demand on a simplified manufacturing process by
suppressing the formation of resin bur on the back of a leadframe
or by ensuring a standoff height of external electrodes from a
resin encapsulant during a resin encapsulation process step.
DISCLOSURE OF INVENTION
[0024] In order to achieve this object, the present invention
discloses a resin-molded semiconductor device formed by using a
seal tape for preventing the overflow of a resin during resin
encapsulation and a method for manufacturing a resin-molded
semiconductor device using a seal tape.
[0025] A resin-molded semiconductor device according to the present
invention includes: a semiconductor chip having electrode pads;
inner leads; connection members for electrically connecting the
electrode pads of the semiconductor chip to the inner leads; and a
resin encapsulant for molding the semiconductor chip, inner leads
and connection members together. The lower part of each said inner
lead, including at least part of the back surface thereof,
functions as an external electrode. And the external electrode
protrudes downward from the back surface of the resin
encapsulant.
[0026] In this structure, since the external electrode of the inner
lead protrudes from the resin encapsulant, a standoff height can be
secured for the external electrode. That is to say, in this
structure, the inner leads can be directly connected, as external
terminals, onto a motherboard without providing any ball electrodes
for the external electrodes. As a result, the first object is
accomplished.
[0027] The resin-molded semiconductor device may further include: a
die pad for supporting the semiconductor chip thereon; and support
leads for supporting the die pad. Each said support lead may
include a depressed portion for elevating the die pad above the
inner leads.
[0028] In such an embodiment, the resin encapsulant exists under
the die pad, thus increasing the force of the resin encapsulant
holding the die pad and semiconductor chip. In addition, since the
die pad is slightly elevated only by the depth of the depression of
the support leads, the structure of the resin-molded semiconductor
device can be kept thin without increasing the thickness of the
resin-molded semiconductor device so much.
[0029] In the resin-molded semiconductor device, a protrusion
height of the external electrodes as measured from the back surface
of the resin encapsulant is preferably in the range from about 10
.mu.m to about 40.mu.m.
[0030] In such an embodiment, the force of the resin encapsulant
holding the inner leads is not weakened so much and the external
electrodes can be made to function as external terminals.
[0031] A basic method for manufacturing a resin-molded
semiconductor device according to the present invention includes: a
first step of preparing molding die assembly, semiconductor chip
and peripheral member; a second step of attaching a seal tape to
between the peripheral member and the die assembly such that the
seal tape adheres to part of a surface of the peripheral member; a
third step of encapsulating the semiconductor chip and the
peripheral member, except for at least the part of the surface
thereof, within a resin encapsulant with the seal tape attached;
and a fourth step of removing the seal tape after the third step
has been performed. After the fourth step has been performed, at
least the part of the surface of the peripheral member is exposed
out of the resin encapsulant.
[0032] According to this method, if there is any part to be exposed
without fail in the peripheral member, a structure with that part
exposed out of the resin encapsulant can be obtained by adhering
the seal tape to that part of the peripheral member in the second
step. Also, since no resin bur is formed on that part of the
peripheral member, either, conventionally required process steps,
like water jet, can be eliminated. As a result, the manufacturing
process can be simplified, and therefore, the first object is
accomplished.
[0033] In the basic method for manufacturing a resin-molded
semiconductor device, the first step may include: a first sub-step
of preparing, as the peripheral member, a leadframe including inner
leads and a region for supporting the semiconductor chip thereon; a
second sub-step of bonding the semiconductor chip onto the region
of the leadframe for supporting the semiconductor chip thereon; and
a third sub-step of electrically bonding the semiconductor chip to
the inner leads. In the second step, the seal tape may be adhered
to the back surfaces of the inner leads.
[0034] According to this method, a resin-molded semiconductor
device, in which a semiconductor chip, connected to a leadframe, is
provided within a resin encapsulant, is obtained. Also, the back
surfaces of the inner leads never fail to be exposed out of the
resin encapsulant. Furthermore, by regulating the pressure of the
inner leads against the seal tape, the protrusion height of the
inner leads as measured from the back surface of the resin
encapsulant, i.e., the standoff height of the inner leads, can be
adjusted. Accordingly, a resin-molded semiconductor device,
attaining the effects of the first resin-molded semiconductor
device described above, can be formed easily.
[0035] In the method for manufacturing a resin-molded semiconductor
device including the leadframe, in the first sub-step of the first
step, a die pad may be formed as the region for supporting the
semiconductor chip thereon. Support leads may be formed for
supporting the die pad. And a depressed portion for elevating the
die pad above the inner leads may be formed in each said support
lead. In the second sub-step of the first step, the semiconductor
chip may be bonded onto the die pad. In the third sub-step of the
first step, the semiconductor chip, which has been bonded onto the
die pad, may be electrically bonded to the inner leads via metal
fine wires. And in the second step, the seal tape may be adhered
only to the back surfaces of the inner leads in the leadframe.
[0036] According to this method, the resin encapsulant can exist
under the back of the die pad without increasing the total
thickness of the resin-molded semiconductor device so much. As a
result, the force of the resin encapsulant holding the die pad can
be increased and a thinner resin-molded semiconductor device can be
formed easily.
[0037] The method for manufacturing a resin-molded semiconductor
device including the leadframe may further include the step of
cutting off part of each said inner lead laterally protruding out
of the resin encapsulant such that end faces of the inner leads are
substantially flush with the side faces of the resin encapsulant
after the fourth step has been performed.
[0038] According to this method, a laterally protruding portion can
be eliminated from each inner lead. As a result, a resin-molded
semiconductor device with a reduced area can also be formed.
[0039] In the method for manufacturing a resin-molded semiconductor
device including the leadframe, in the first sub-step of the first
step, the leadframe prepared may have been plated with nickel (Ni),
palladium (Pd) and gold (Au) layers.
[0040] According to this method, plated layers of quality can be
formed by pre-plating, and the use of a seal tape can eliminate
additional process steps for removing resin bur, such as a water
jet process step, which are usually performed after resin
encapsulation. Accordingly, even when resin bur should be removed,
the plated layers do not peel off.
[0041] In the method for manufacturing a resin-molded semiconductor
device including the leadframe, in the second step, the seal tape
attached may have such a thickness as corresponding to a
predetermined value, which is equal to the height of the lower
surfaces of the inner leads protruding downward from the back
surface of the resin encapsulant after the resin encapsulation.
[0042] According to this method, the protrusion height of the inner
leads can be easily adjusted based on the thickness of the seal
tape. Accordingly, not only the force of the resin encapsulant
holding the inner leads, but also the standoff height provided for
making the lower part of each inner lead function as an external
terminal can be controlled at respectively adequate values.
[0043] In the basic method for manufacturing a resin-molded
semiconductor device, the first step may include: a first sub-step
of preparing a substrate as the peripheral member, the upper
surface of the substrate being provided with interconnects, the
back surface of the substrate being provided with external
electrodes to be connected to the interconnects; a second sub-step
of bonding the semiconductor chip onto the upper surface of the
substrate; and a third sub-step of electrically connecting the
semiconductor chip to the interconnects on the upper surface of the
substrate via connection members. In the second step, the seal tape
may be adhered at least to the external electrodes.
[0044] According to this method, a resin-molded semiconductor
device of a substrate-bonded type, in which external electrodes are
exposed out of the resin encapsulant without fail, can be
formed.
[0045] In the basic method for manufacturing a resin-molded
semiconductor device, the first step may include: a first sub-step
of preparing at least a radiator plate as the peripheral member;
and a second sub-step of mounting the semiconductor chip on the
radiator plate. In the second step, the seal tape may be attached
to the back surface of the radiator plate.
[0046] According to this method, a resin-molded semiconductor
device including a radiator plate with good radiation properties,
in which no resin encapsulant overflows to reach the back of the
radiator plate, can be formed.
[0047] In the method for manufacturing a resin-molded semiconductor
device including the radiator plate, in the first substep of the
first step, a leadframe including leads and a bed may be further
prepared as the peripheral member. In the second sub-step of the
first step, the semiconductor chip may be bonded onto the bed and
then the bed may be mounted onto the radiator plate, thereby
mounting the semiconductor chip over the radiator plate.
[0048] According to this method, a resin-molded semiconductor
device including a radiator plate can be formed easily by using a
leadframe.
[0049] In the basic method for manufacturing a resin-molded
semiconductor device, in the first step, a lead assembly, including
inner and outer leads, may be prepared as the peripheral member. In
the second step, the seal tape may be adhered to between the inner
leads and the molding die assembly so as to be attached to part of
the surface of each said inner lead. In the third step, all the
members, except for at least the part of the surface of each said
inner lead, may be encapsulated within the resin encapsulant with
the seal tape attached, thereby forming a resin package including
an opening and a recess within the opening. The method may further
include, posterior to the fourth step, the steps of: mounting the
semiconductor chip having the electrode pads into the recess of the
resin package; electrically connecting the electrode pads of the
semiconductor chip to the inner leads via connection members; and
sealing the opening with a sealing member. After the fourth step
has been performed, at least the part of the surface of each said
inner lead may be exposed out of the resin encapsulant.
[0050] According to this method, it is possible to form easily a
resin-molded semiconductor device, which a solid-state imaging
device or the like, requiring an overlying free space, is built in.
In such a case, a connection portion between an inner lead and the
semiconductor chip can be exposed out of the resin encapsulant
without fail.
BRIEF DESCRIPTION OF DRAWINGS
[0051] FIG. 1(a) and 1(b) are respectively plan view and
cross-sectional view of a resin-molded semiconductor device
according to a first embodiment of the present invention, in which
a resin encapsulant is illustrated as being transparent.
[0052] FIG. 2 is a cross-sectional view illustrating the process
step of preparing a leadframe during a manufacturing process of the
resin-molded semiconductor device in the first embodiment.
[0053] FIG. 3 is a cross-sectional view illustrating the process
step of bonding a semiconductor chip onto a die pad during the
manufacturing process of the resin-molded semiconductor device in
the first embodiment.
[0054] FIG. 4 is a cross-sectional view illustrating the process
step of forming metal fine wires during the manufacturing process
of the resin-molded semiconductor device in the first
embodiment.
[0055] FIG. 5 is a cross-sectional view illustrating the process
step of placing a seal tape under the leadframe during the
manufacturing process of the resin-molded semiconductor device in
the first embodiment.
[0056] FIG. 6 is a cross-sectional view illustrating a resin
encapsulation process step during the manufacturing process of the
resin-molded semiconductor device in the first embodiment.
[0057] FIG. 7 is a cross-sectional view of the resin-molded
semiconductor device after the process step of cutting off the ends
of the inner leads is finished during the manufacturing process of
the resin-molded semiconductor device in the first embodiment.
[0058] FIG. 8 is a partial bottom view of the resin-molded
semiconductor device formed by the manufacturing process of the
resin-molded semiconductor device in the first embodiment.
[0059] FIG. 9 is a cross-sectional view of a resin-molded
semiconductor device of a substrate-bonded type according to a
second embodiment of the present invention.
[0060] FIGS. 10(a) and 10(b) are cross-sectional views illustrating
the process step of bonding a semiconductor chip onto the substrate
with metal fine wires and the process step of mounting a
semiconductor chip onto the substrate with bumps, respectively,
during a manufacturing process of the resin-molded semiconductor
device in the second embodiment.
[0061] FIG. 11 is a cross-sectional view illustrating a resin
encapsulation process step during the manufacturing process of the
resin-molded semiconductor device in the second embodiment.
[0062] FIG. 12 is a cross-sectional view of a resin-molded assembly
after the seal tape has been removed during the manufacturing
process of the resin-molded semiconductor device in the second
embodiment.
[0063] FIG. 13 is a cross-sectional view of a resin-molded
semiconductor device including a radiator plate according to a
third embodiment of the present invention.
[0064] FIG. 14 is a cross-sectional view illustrating the process
step of preparing a leadframe during a manufacturing process of the
resin-molded semiconductor device in the third embodiment.
[0065] FIG. 15 is a cross-sectional view illustrating the process
step of bonding a semiconductor chip onto a radiator plate and
forming metal fine wires during the manufacturing process of the
resin-molded semiconductor device in the third embodiment.
[0066] FIG. 16 is a cross-sectional view illustrating the process
step of placing a seal tape under the radiator plate and the
leadframe during the manufacturing process of the resin-molded
semiconductor device in the third embodiment.
[0067] FIG. 17 is a cross-sectional view illustrating a resin
encapsulation process step during the manufacturing process of the
resin-molded semiconductor device in the third embodiment.
[0068] FIG. 18 is a cross-sectional view of the resin-molded
semiconductor device after the seal tape has been removed during
the manufacturing process of the resin-molded semiconductor device
in the third embodiment.
[0069] FIG. 19 is a cross-sectional view of a resin-molded
semiconductor device as a CCD package according to a fourth
embodiment of the present invention.
[0070] FIG. 20 is a cross-sectional view illustrating a resin
encapsulation process step during a manufacturing process of the
resin-molded semiconductor device in the fourth embodiment.
[0071] FIG. 21 is a cross-sectional view illustrating the process
step of removing a seal tape after the resin encapsulation during
the manufacturing process of the resin-molded semiconductor device
in the fourth embodiment.
[0072] FIG. 22 is a cross-sectional view illustrating the process
step of forming metal fine wires and sealing with seal glass during
the manufacturing process of the resin-molded semiconductor device
in the fourth embodiment.
[0073] FIGS. 23(a) and 23(b) are respectively plan view and
cross-sectional view of a conventional resin-molded semiconductor
device of the type including external electrodes on its back.
[0074] FIG. 24 is a cross-sectional view of a conventional
resin-molded semiconductor device ensuring a standoff height by
providing ball electrodes for the external electrodes.
[0075] FIG. 25 is a cross-sectional view illustrating the process
step of preparing a leadframe during a conventional manufacturing
process of the resin-molded semiconductor device.
[0076] FIG. 26 is a cross-sectional view illustrating the process
step of bonding a semiconductor chip onto a die pad during the
conventional manufacturing process of the resin-molded
semiconductor device.
[0077] FIG. 27 is a cross-sectional view illustrating the process
step of forming metal fine wires during the conventional
manufacturing process of the resin-molded semiconductor device.
[0078] FIG. 28 is a cross-sectional view illustrating a resin
encapsulation process step during the conventional manufacturing
process of the resin-molded semiconductor device.
[0079] FIG. 29 is a cross-sectional view of the resin-molded
semiconductor device after the resin encapsulation during the
conventional manufacturing process of the resin-molded
semiconductor device.
[0080] FIG. 30 is a bottom view of the resin-molded semiconductor
device formed by the conventional manufacturing process of the
resin-molded semiconductor device.
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1
[0081] FIG. 1(a) is a plan view of a resin-molded semiconductor
device according to a first embodiment, and FIG. 1(b) is a
cross-sectional view thereof taken along the line 1b-1b in FIG.
1(a). In FIG. 1(a), a resin encapsulant 17 is illustrated as being
transparent, a semiconductor chip 15 has a contour as indicated by
the dashed line, and the illustration of metal fine wires 16 is
omitted.
[0082] As shown in FIGS. 1(a) and 1(b), the resin-molded
semiconductor device of this embodiment includes a leadframe
consisting of: inner leads 12; a die pad 13 for supporting the
semiconductor chip thereon; and support leads 14 for supporting the
die pad 13. The semiconductor chip 15 is bonded on the die pad 13
with an adhesive, and electrode pads (not shown) of the
semiconductor chip 15 are electrically connected to the inner leads
12 with metal fine wires 16. And the inner leads 12, die pad 13,
support leads 14, semiconductor chip 15 and metal fine wires 16 are
encapsulated within the resin encapsulant 17. Also, the die pad 13
is elevated by depressed portions 19 of the support leads 14 so as
to be located above the inner leads 12. Accordingly, after the
chip, frame and so on have been molded with the resin encapsulant
17, a thin layer of the resin encapsulant 17 exists under the back
surface of the die pad 13.
[0083] Hereinafter, the features of the resin-molded semiconductor
device according to this embodiment will be described. No resin
encapsulant 17 exists on the respective lower parts of the inner
leads 12. In other words, the respective lower surfaces of the
inner leads 12 are exposed, and are used as interconnection with a
motherboard. That is to say, the respective lower parts of the
inner leads 12 function as external electrodes 18. In addition,
virtually no resin burr, which ordinarily sticks out during a resin
encapsulation process step, exists on the external electrodes 18.
And the external electrodes 18 slightly protrude downward from the
back surface of the resin encapsulant 17. The external electrodes
18 can be easily formed in such a shape by the manufacturing
process described later so as to protrude downward and have no
resin burr thereon.
[0084] In the resin-molded semiconductor device of this embodiment,
no outer leads, which function as external electrode terminals in
many conventional structures, exist beside the inner leads 12.
Instead, the lower part of each inner lead 12, including the lower
and side faces thereof, functions as an external electrode 18.
Accordingly, such a structure contributes to downsizing of a
semiconductor device. Moreover, since no resin burr exists on the
respective lower surfaces of the inner leads 12, i.e., the lower
surfaces of the external electrodes 18, the electrodes of the
motherboard can be bonded to these external electrodes 18 with more
reliability. Furthermore, the external electrodes 18 are formed to
protrude from the plane of the resin encapsulant 17. Thus, a
standoff height, which should be secured in bonding the external
electrodes to the electrodes of the motherboard during mounting of
the resin-molded semiconductor device onto the motherboard, has
already been provided for the external electrodes 18. Accordingly,
the external electrodes 18 can be used as external terminals as
they are. Also, unlike the conventional process, there is no need
to attach solder balls to the external electrodes 18 during
mounting of the device onto the motherboard. Therefore, this method
is advantageous in the number and cost of manufacturing process
steps.
[0085] In addition, the die pad 13 is elevated above the inner
leads 12 and a thin layer of the resin encapsulant 17 exists on the
back of the die pad 13. As a result, the reliability of the
resin-molded semiconductor device improves.
[0086] In this embodiment, the die pad 13 is provided for
supporting the semiconductor chip 15 thereon. Alternatively, even
if it were not for the die pad 13, the semiconductor chip still
could be supported by the respective insulated ends of the inner
leads or mounted on a plastic tape. That is to say, the die pad 13
is not always required, and this embodiment is applicable to a
leadframe without a die pad.
[0087] Also, in this embodiment, the metal fine wires 16 are used
as means for electrically connecting the electrodes of the
semiconductor chip 15 to the inner leads 12. Alternatively, the
electrodes of the semiconductor chip 15 may be electrically
connected to the inner leads 12 by flip-chip bonding (i.e., with
bumps interposed therebetween) or direct bonding (i.e., by forming
a eutectic alloy).
[0088] Next, a method for manufacturing the resin-molded
semiconductor device of this embodiment will be described with
reference to the drawings. FIGS. 2 through 7 are cross-sectional
views illustrating a manufacturing process of the resin-molded
semiconductor device of this embodiment.
[0089] First, in the process step shown in FIG. 2, a leadframe 20,
including inner leads 12 and a die pad 13 for supporting a
semiconductor chip thereon, is prepared. Although the die pad 13 is
actually supported by support leads, the support leads are not
illustrated in FIG. 2 because the leads are not included in this
cross section. Also, a depressed portion is formed in each of these
support leads, thereby the die pad 13 is elevated above the plane
on which the inner leads 12 are located. The leadframe 20 prepared
is not provided with tie bars used for stopping the outflow of a
resin encapsulant during resin encapsulation.
[0090] The leadframe 20 of this embodiment is formed by plating a
frame made of copper (Cu) with the three metal layers of: an
undercoat nickel (Ni) layer; a palladium (Pd) layer plated thereon;
and an outermost thin gold (Au) layer. Alternatively, the leadframe
20 may be made of any raw material other than copper (Cu), e.g.,
Alloy 42. Also, the leadframe 20 may be plated with any noble
metals other than nickel (Ni), palladium (Pd) and gold (Au).
Furthermore, the number of plated layers does not have to be
three.
[0091] Next, in the process step shown in FIG. 3, a semiconductor
chip 15 is mounted and bonded, with an adhesive, onto the die pad
of the leadframe prepared. This process step is so-called "die
bonding". It should be noted that any support member other than a
leadframe may be used to support the semiconductor chip. For
example, a TAB tape or a substrate may also be used.
[0092] Then, in the process step shown in FIG. 4, the semiconductor
chip 15, which has been bonded onto the die pad 13, is electrically
bonded to the inner leads 12 with metal fine wires 16. This process
step is so-called "wire bonding". The metal fine wires may be made
of an appropriately selected material such as aluminum (Al) or gold
(Au). Optionally, the semiconductor chip 15 may be electrically
connected to the inner leads 12 via bumps or the like, not the
metal fine wires 16.
[0093] Subsequently, in the process step shown in FIG. 5, a seal
tape 21 is attached to the respective back surfaces of the inner
leads 12 with the semiconductor chip 15 bonded onto the die pad 13
of the leadframe.
[0094] The seal tape 21 is used as a sort of mask for preventing
the resin encapsulant from overflowing and reaching the respective
lower surfaces of the inner leads 12 during resin encapsulation.
The existence of the seal tape 21 can prevent resin burr from being
formed on the back surfaces of the inner leads 12. The seal tape 21
attached to the inner leads 12 and so on may be any resin-based
tape, which is mainly composed of polyethylene terephthalate,
polyimide, polycarbonate or the like, can be easily peeled after
the resin encapsulation and has some resistance to an elevated
temperature environment during the resin encapsulation. In this
embodiment, a tape mainly composed of polyethylene terephthalate is
used and the thickness thereof is 50 .mu.m.
[0095] In this embodiment, the seal tape 21 is attached to the
entire back surface of the leadframe, but is adhered only to the
surfaces of the inner leads 12 of the leadframe. That is to say,
the seal tape 21 does not adhere to the back surface of the die pad
13, which is elevated by the depressed portions of the support
leads. Alternatively, the radiation properties of the die pad 13
may be increased by adhering the seal tape 21 to the back surface
of the die pad 13 and then peeling the seal tape 21 off to expose
the back surface of the die pad 13 after the resin encapsulation
step.
[0096] Then, in the process step shown in FIG. 6, the leadframe, on
which the semiconductor chip 15 has been bonded and to which the
seal tape 21 has been attached, is introduced into a die assembly.
And a resin encapsulant 17 is poured into the die assembly to mold
the chip, frame and so on with the encapsulant 17. In this case,
resin encapsulation is performed while pressing downward the ends
22 of the inner leads 12 of the leadframe with the dies such that
the resin encapsulant 17 does not reach the respective lower
surfaces of the inner leads 12. The resin encapsulation is also
performed with the seal tape 21 on the back of the inner leads 12
pressed against the face of the die.
[0097] Finally, in the process step shown in FIG. 7, the seal tape
21, which has been attached to the respective back surfaces of the
inner leads 12, is peeled off and removed, thereby forming external
electrodes 18, protruding from the back surface of the resin
encapsulant 17. Then, the ends of the inner leads 12 are cut off to
be substantially flush with the side faces of the resin encapsulant
17, thereby completing a resin-molded semiconductor device such as
that shown in FIG. 7.
[0098] FIG. 8 is a partial bottom view of the resin-molded
semiconductor device of this embodiment, illustrating respective
parts of the external electrodes 18 on a larger scale. As shown in
FIG. 8, in this embodiment, the formation of resin bur on the back
and side faces of the inner leads 12, i.e., on the surfaces of the
external electrodes 18, can be prevented. This is because the resin
encapsulation process step is performed with the seal tape 21
adhered to the back surface of the leadframe. Also, unlike a
conventional manufacturing process, it is possible to prevent the
resin encapsulant 17 from reaching the surfaces of the external
electrodes 18 and part of the external electrodes 18 from being
buried in the resin encapsulant 17.
[0099] According to the manufacturing method of this embodiment,
the seal tape 21 is attached in advance to the respective back
surfaces of the inner leads 12 before the resin encapsulation
process step. Thus, the resin encapsulant 17 cannot reach, and no
resin burr is formed on, the back surfaces of the inner leads 12
functioning as external electrodes. Accordingly, resin burr, formed
on the inner leads, need not be removed therefrom using water jet
or the like, unlike a conventional method for manufacturing a
resin-molded semiconductor device with the lower surfaces of inner
leads entirely exposed. That is to say, since this troublesome step
of deburring can be omitted, this process is simple enough to
mass-produce a great number of resin-molded semiconductor devices.
In addition, peeling of metal plated layers such as nickel (Ni),
palladium (Pd) and gold (Au) on the leadframe, which might happen
during the conventional deburring process step using water jet, for
example, can be eliminated. For that reason, the leadframe can be
plated in advance with these metal layers before the resin
encapsulation process step.
[0100] In addition, since the external electrodes 18 formed by the
manufacturing process of this embodiment protrude from the resin
encapsulant 17, the external electrodes 18 can be used as external
terminals as they are, without providing solder balls as in a
conventional process.
[0101] Although the step of deburring using water jet can be
omitted, the step of attaching the seal tape should be additionally
performed in this embodiment. However, the step of attaching the
seal tape 21 is more cost-effective than the water jet process
step. And it is easier to control the former process step than the
latter. Accordingly, the process can be simplified without fail.
Among other things, the method of this embodiment is particularly
advantageous in that attaching the seal tape can eliminate the
water jet process step conventionally required, which has brought
about various quality-control problems like peeling of metal plated
layers from the leadframe and deposition of impurities thereon.
Thus, in this embodiment, the plated metal layers are much less
likely to peel off. Also, it is true that resin burr still may be
formed in this embodiment depending on the attachment state of the
seal tape. Even so, the resulting resin burr is very thin, and can
be easily removed with water jet at a low water pressure.
Accordingly, should such a water jet process step be required,
peeling of the metal plated layers still can be prevented. And
there is no problem if the leadframe is plated with these metal
layers beforehand.
[0102] It should be noted that a level difference is formed between
the respective back surfaces of the inner leads 12 and that of the
resin encapsulant 17 as shown in FIG. 6. This is because the seal
tape 21 softens and thermally shrinks owing to the heat applied by
the molten resin encapsulant during the resin encapsulation step,
and the inner leads 12 are strongly forced into the seal tape 21.
Accordingly, in this structure, the back surfaces of the inner
leads 12 protrude from that of the resin encapsulant 17. As a
result, a standoff height of the external electrodes 18, or the
respective lower parts of the inner leads 12, can be secured.
Therefore, these protruding external electrodes 18 can be used as
external terminals as they are.
[0103] The height of the level difference between the respective
back surfaces of the inner leads 12 and that of the resin
encapsulant 17 can be controlled based on the thickness of the seal
tape 21 attached before the step of encapsulating. For example, in
this embodiment, since the thickness of the seal tape 21 is 50
.mu.m, the height of the level difference, i.e., the protrusion
height of the external electrodes 18, is usually about one-half of
the thickness, and 50 .mu.m at its maximum. That is to say, the
height of a portion of the seal tape 21 upwardly forced as measured
from the back surfaces of the inner leads 12 is determined
depending on the thickness of the seal tape 21. In other words, the
protrusion height of the external electrodes 18 can be
self-controlled by the thickness of the seal tape 21, thus
facilitating the manufacturing. The protrusion height of the
external electrodes 18 can be controlled only by adjusting the
thickness of the seal tape 21 during a mass production process, and
there is no need to provide an additional process step separately.
Accordingly, the manufacturing method of this embodiment is
extremely advantageous in terms of the process control cost. It
should be noted that as for the seal tape 21 to be attached, the
hardness of a material used, the thickness and the thermal
softening properties thereof can be determined depending on the
desired height of the level difference.
[0104] In the resin-molded semiconductor device of this embodiment,
although the resin encapsulant 17 exists on the back of the die pad
13 as shown in FIG. 2, the thickness thereof is equal to the
elevated height of the die pad 13, and is extremely small. Thus,
the resin-molded semiconductor device of this embodiment is
substantially one-side-encapsulated semiconductor device.
[0105] In the foregoing exemplary embodiment, the seal tape 21 is
attached in advance to the respective lower surfaces of the inner
leads 12 of the leadframe before the resin encapsulation process
step. Instead of attaching the tape to the leadframe this way, the
seal tape 21 may be placed on a molding die assembly and the
leadframe may be adhered thereto. In such a case, the seal tape can
be reeled off and supplied to the molding die assembly as will be
described later. As a result, the process can be further
simplified.
[0106] Also, in this embodiment, a manufacturing process, in which
resin encapsulation is performed with the seal tape attached to the
back of the leadframe, has been exemplified. However, the method of
the present invention is not limited to a semiconductor device
including a leadframe. A technique of using a seal tape during a
resin encapsulation process step, which is a basic concept of the
present invention, is broadly applicable to any resin encapsulation
process step for a semiconductor device incorporating a
semiconductor chip and including some members to be molded with
resin. Thus, this technique is applicable to a resin encapsulation
process step for a semiconductor device of a TAB or substrate
type.
Embodiment 2
[0107] Next, a second embodiment of the present invention will be
described. FIG. 9 is a cross-sectional view illustrating a
resin-molded semiconductor device of a substrate-bonded type
according to this embodiment.
[0108] As shown in FIG. 9, the resin-molded semiconductor device of
this embodiment is of a substrate-bonded type such as a BGA (ball
grid array) type. The device includes: a substrate 24 made of
single- or multiple-layered glass epoxy plastic or ceramic; a
semiconductor chip 25 mounted on the substrate 24; and metal fine
wires 26 for electrically connecting interconnects (not shown)
formed on the upper surface of the substrate 24 to electrode pads
(not shown) of the semiconductor chip 25. And over the upper
surface of the substrate 24, the semiconductor chip 25,
interconnects and metal fine wires 26 are molded with an insulating
resin encapsulant 27. On the back of the substrate 24, external
electrode pads (lands) 28 are formed. The interconnects on the
upper surface of the substrate 24 are connected to the external
electrode pads (lands) 28 on the back surface of the substrate 24
by way of through holes or via holes.
[0109] In this embodiment, ball electrodes 29, which are made of a
conductive material for bonding the substrate 24 to an external
board, are provided for the external electrode pads 28. However,
the ball electrodes 29 do not have to be provided. Also, the
substrate 24 may be a thin polyimide film, for example.
[0110] According to this embodiment, the assembly is
transfer-molded with a resin encapsulant while a seal tape is
attached to the back of the substrate 24 during a resin
encapsulation process step as will be described later. Thus, it is
possible to prevent the resin encapsulant 27 from overflowing to
reach the external electrode pads 28. Consequently, a surface to be
connected to a motherboard can be free from resin bur, which would
otherwise be formed on the external electrode pads 28, and the
reliability in connecting with the ball electrodes 29 interposed
can be improved.
[0111] Next, a method for manufacturing the resin-molded
semiconductor device of this embodiment will be described with
reference to the drawings. FIGS. 10 through 12 are cross-sectional
views illustrating, on a step-by-step basis, a manufacturing
process for the BGA-type resin-molded semiconductor device of this
embodiment.
[0112] First, in the process step shown in FIG. 10(a),
interconnects (not shown) are formed on the substrate 24, which is
a single- or multiple-layered glass epoxy plastic or ceramic plate.
Through holes or via holes are formed in the substrate 24. And the
external electrode pads 28 are formed on the back of the substrate
24. Thereafter, the semiconductor chip 25 is bonded at a
predetermined position on the substrate 24 with a die-bonding
member, for example, and the interconnects on the substrate are
connected to electrode pads (not shown) on the semiconductor chip
with the metal fine wires 26.
[0113] Alternatively, the semiconductor chip 25 may be mounted onto
the substrate 24 in a facedown manner shown in FIG. 10(b). In such
a case, the interconnects on the substrate 24 are ordinarily bonded
to the electrode pads on the semiconductor chip 25 with metal balls
30 like bumps. As the case may be, the interconnects on the
substrate 24 and the electrode pads on the semiconductor chip 25
are alloyed and directly bonded to each other. The subsequent
process steps will be described on the supposition that the bonding
structure shown in FIG. 10(a) has been adopted here.
[0114] Next, in the process step shown in FIG. 11, resin
encapsulation is performed using a molding die assembly 31,
consisting of lower and upper dies 31a and 31b, to mold the
semiconductor chip 25, interconnects, and metal fine wires 26 over
the substrate 24. In this step, before the resin encapsulation is
performed, a first seal tape 32a is attached to the back of the
substrate 24, i.e., to the upper surface of the lower die 31a of
the molding die assembly 31, thereby adhering the seal tape 32a to
the lower surfaces of the external electrode pads 28 of the
substrate 24. In this case, the pressure applied to the die
assembly forces the external electrode pads 28 into the seal tape
32a. As a result, the seal tape 32a adheres to the back of the
substrate 24 and to lower surfaces of the external electrodes 28.
In addition, a second seal tape 32b is also adhered to the lower
surface of the upper die 31b of the molding die assembly 31. By
transfer-molding the assembly with the resin encapsulant 27 in such
a state, only the regions surrounding the semiconductor chip 25 can
be molded with the resin over the upper surface of the substrate 24
and the overflow of the resin encapsulant to the back of the
substrate 24 can be prevented. And as described above, it is
possible to prevent the resin bur from being formed on the external
electrode pads 28 on the back of the substrate 24.
[0115] Also, since not only the first seal tape 31a but also the
second seal tape 32b are used, the resin encapsulant 27 can be
advantageously released from the upper die 31b easily.
[0116] According to such a resin encapsulation technique, resin
encapsulation is performed with pressure applied to the substrate
24 through the molding die assembly 31. Since pressure is herein
applied to the structure with the substrate 24 interposed between
the first and second seal tapes 32a and 32b, the force applied to
the substrate 24 can be cushioned and the fracture or deformation
of the substrate 24 can be advantageously prevented during the
resin encapsulation.
[0117] Finally, in the process step shown in FIG. 12, the
resin-molded assembly, in which the regions surrounding the is
semiconductor chip 25 over the substrate 24 are molded with the
resin encapsulant 27, is released from the molding die assembly 31.
As a result, a resin-molded package, in which no resin encapsulant
has reached the external electrode pads 28 on the back of the
substrate 24, is obtained.
[0118] If the ball electrodes 29 (indicated by the phantom lines)
are provided for the external electrode pads 28 on the back of the
substrate 24, a resin-molded semiconductor device of a BGA type can
be obtained. Alternatively, if these external electrode pads 28
have been formed with a relatively large thickness, then the
external electrode pads 28 may be used as external terminals as
they are without forming the ball electrodes 29 thereon.
[0119] As can be understood, in the method for manufacturing a
BGA-type resin-molded semiconductor device according to this
embodiment, the first and second seal tapes 32a and 32b are used.
By utilizing the elasticity thereof, deformation of the substrate
24 within the molding die assembly can be suppressed, and
deposition of the resin encapsulant or foreign particles on the
external electrode pads 28 of the substrate 24 can be
prevented.
[0120] Of the first and second seal tapes 32a and 32b, the first
seal tape 32a is not always required. Even if only the second seal
tape 32b is provided, it is also possible to prevent the overflow
of the resin encapsulant to the sides or back of the substrate 24,
since the second seal tape 32b is in contact with the upper surface
of the substrate 24.
[0121] Furthermore, the seal tape 32a does not have to be adhered
to the entire back face of the substrate 24. The seal tape 32a is
only required to adhere to at least the lower surfaces of the
external electrode pads 28.
Embodiment 3
[0122] Next, a third embodiment of the present invention will be
described. FIG. 13 is a cross-sectional view illustrating a
resin-molded semiconductor device according to this embodiment. The
resin-molded semiconductor device of this embodiment includes: a
radiator plate; and a semiconductor chip incorporating a device
generating a relatively large quantity of heat, e.g., a high-power
transistor.
[0123] As shown in FIG. 13, the semiconductor device of this
embodiment includes: a bed 33, or a support for a leadframe; a
semiconductor chip 34 bonded on the bed 33 with a die-bonding
member; a metal terminal 35 of the leadframe; a metal fine wire 36
for electrically connecting the metal terminal 35 to the
semiconductor chip 34; and a radiator plate 37 for supporting the
bed 33 thereon. In this structure, all the members are entirely
molded with an insulating resin encapsulant 38, except for the
bottom of the radiator plate 37 and part of the metal terminal 35
protruding out of the resin encapsulant 38 as an external terminal.
That is to say, the upper and side faces of the radiator plate 37,
bed 33, semiconductor chip 34, metal fine wire 36 and the other
part of the metal terminal 35 are molded with the resin encapsulant
38.
[0124] According to this embodiment, the assembly is
transfer-molded with a seal tape attached to the back of the
radiator plate 37 during a resin encapsulation process step as will
be described later. Thus, it is possible to prevent the resin
encapsulant 38 from overflowing to reach the back of the radiator
plate 37 and forming resin bur thereon. Accordingly, the radiating
face (back surface) of the radiator plate 37 can maintain it
function. That is to say, its function of dissipating the heat,
which has been generated from the semiconductor chip of the
semiconductor device, to the outside can be maintained and
improved.
[0125] Next, a method for manufacturing the resin-molded
semiconductor device of this embodiment will be described with
reference to the drawings. FIGS. 14 through 18 are cross-sectional
views illustrating, on a step-by-step basis, a manufacturing
process for the resin-molded semiconductor device including a
radiator plate according to this embodiment.
[0126] First, in the process step shown in FIG. 14, a leadframe,
including the bed 33, or a support for a semiconductor chip, and
the metal terminal 35, is prepared. The semiconductor chip 34 is
bonded onto the upper surface of the bed 33 with a die-bonding
member. Then, the semiconductor chip 34 is connected to the metal
terminal 36 with the metal fine wire 36.
[0127] Next, in the process step shown in FIG. 15, the radiator
plate 37 is bonded onto the back of the bed 33. Alternatively, the
bed 33 may also be formed with an increased thickness so as to
function as a radiator plate by itself.
[0128] Then, in the process step shown in FIG. 16, the seal tape 39
is adhered to the back of the radiator plate 37. In this case, the
radiator plate 37 with the seal tape 39 adhered thereto may be
placed into a molding die assembly. Alternatively, the back of the
radiator plate 37 may be adhered to the seal tape 39 by attaching
in advance the seal tape 39 to the molding die assembly, more
specifically onto the lower die, and then mounting the radiator
plate 37 onto the lower die.
[0129] Subsequently, in the process step shown in FIG. 17, the bed
33, semiconductor chip 34, metal fine wire 36 and part of the metal
terminal 35 are molded with the insulating resin encapsulant 38
while the seal tape 39 is adhered to the back of the radiator plate
37. In this case, the bottom of the radiator plate 37 and the other
part of the metal terminal 35 are exposed out of the resin
encapsulant 38.
[0130] Finally, in the process step shown in FIG. 18, the seal tape
39 is peeled off from the back of the radiator plate 37 and the
metal terminal 35 is folded, thereby completing a resin-molded
semiconductor device shown in FIG. 18, in which the back of the
radiator plate 37 is exposed.
[0131] In the method for manufacturing the resin-molded
semiconductor device including a radiator plate according to this
embodiment, the seal tape 39, which is adhered to the back of the
radiator plate 37, is used during the resin encapsulation process
step, thereby preventing the overflow of the resin encapsulant onto
the back of the radiator plate 37 and the formation of resin bur
thereon. In other words, since the back of the radiator plate 37
can be exposed without fail, a resin-molded semiconductor device
can be obtained without lessening the radiation effect of the
radiator plate 37. Also, since the resin encapsulation is performed
with the seal tape 39 adhered to the back of the radiator plate 37,
part of the seal tape 39 is forced inward to partially cover the
sides of the radiator plate 37. As a result, the radiator plate 37
slightly protrudes out of the back of the resin encapsulant after
the resin encapsulation is over. Accordingly, in mounting such a
resin-molded semiconductor device onto a motherboard, the entire
back surface of the radiator plate 37 can be in contact with the
motherboard without fail, thus enhancing the radiation effect.
Embodiment 4
[0132] Next, a fourth embodiment of the present invention will be
described with reference to the drawings. FIG. 19 is a
cross-sectional view illustrating a resin-molded semiconductor
device, like a CCD package, according to this embodiment.
[0133] As shown in FIG. 19, the resin-molded semiconductor device
of this embodiment includes: a resin package 41 with an opening in
the upper part thereof and a recess 42 provided within the opening;
a solid-state imaging device 40 bonded onto the bottom of the
recess 42 of the resin package 41 with a die-bonding member; inner
leads 43 provided near the recess 42 of the resin package 41; outer
leads 46, which are connected to the respective inner leads 43 and
extend outward through the resin package 41; and metal fine wires
44 for electrically connecting electrode pads (not shown) on the
solid-state imaging device 40 to the inner leads 43 on the resin
package 41. Also, the opening of the resin package 41 is sealed
with sealing glass 45. The outer leads 46, protruding out of the
resin package 41, are folded downward. It should be noted that the
resin package 41 is a package that has been integrally
transfer-molded with an insulating resin.
[0134] In the resin-molded semiconductor device according to this
embodiment, the resin package 41 is formed by performing
transfer-molding with a seal tape attached onto the inner leads 43
during a resin encapsulation process step as will be described
later. Thus, no resin bur is formed on respective upper surfaces of
the inner leads 43, but these surfaces are exposed. Accordingly, in
this resin-molded semiconductor device, the inner leads 43 can be
connected to the solid-state imaging device 40 via the metal fine
wires 44 with more reliability.
[0135] Next, a method for manufacturing the resin-molded
semiconductor device according to this embodiment, like a CCD
package, will be described with reference to the drawings. FIGS. 20
through 22 are cross-sectional views illustrating, on a
step-by-step basis, a manufacturing process for the resin-molded
semiconductor device according to this embodiment.
[0136] First, in the process step shown in FIG. 20, a lead
assembly, including inner and outer leads 43 and 46, is prepared.
Before the resin package is molded, the seal tape 47 is attached or
adhered to those portions of the lead assembly to be the inner
leads 43, thereby preventing the overflow of the resin encapsulant
onto the upper surfaces of the inner leads 43. Then, the respective
members are transfer-molded with a resin within a molding die
assembly consisting of upper and lower dies 51a and 51b, thereby
forming the resin package 41. FIG. 20 illustrates a state where the
resin package 41 has already been formed and the respective
surfaces of the inner and outer leads 43 and 46 are covered with
the seal tape 47.
[0137] Then, in the process step shown in FIG. 21, the seal tape 47
is peeled off, thereby obtaining a resin package 41, in which the
respective upper surfaces of the inner leads 43 are exposed without
fail. At an elevated temperature, the seal tape 47 adheres to the
inner leads 43 without forming any gap therebetween. Thus, on the
exposed surfaces of the inner leads 43, from which the seal tape 47
has been peeled off, no foreign particles, such as resin bur of the
resin encapsulant, are deposited.
[0138] Subsequently, in the process step shown in FIG. 22, the
solid-state imaging device 40 is bonded onto the bottom of the
recess 42 provided within the resin package 41. Electrode pads on
the solid-state imaging device 40 are connected to the inner leads
43 with the metal fine wires 44. After the opening of the resin
package 41 has been sealed with the sealing glass 45, the outer
leads 46 are folded. The outer leads 46 may be folded into a
desired shape depending on the type of the semiconductor
device.
[0139] A resin encapsulation technique using a seal tape according
to this embodiment is particularly suitable for manufacturing a
semiconductor device including a resin package with an opening in
the upper part thereof, e.g., an optical semiconductor device like
a CCD or a hologram. In particular, remarkable effects can be
attained if this embodiment is applied to molding a resin package
including leads.
[0140] Another application of this embodiment will be briefly
described. In manufacturing a component, such as an LED, the
package of which should have required color or transparency, resin
encapsulation can be performed effectively by attaching a seal tape
to a molding die assembly in advance such that foreign particles or
dirt involved with the molding die assembly are not transferred to
the package. As a result, an excellent package can be formed.
Industrial Applicability
[0141] The resin-molded semiconductor device and the method for
manufacturing the same according to the present invention are
applicable to all sorts of electronic equipment using a
semiconductor integrated circuit made up of various types of
transistors.
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