U.S. patent number RE41,478 [Application Number 11/182,040] was granted by the patent office on 2010-08-10 for semiconductor device having an improved connection arrangement between a semiconductor pellet and base substrate electrodes and a method of manufacture thereof.
This patent grant is currently assigned to Renesas Electronics Corporation. Invention is credited to Atsushi Nakamura, Kunihiko Nishi.
United States Patent |
RE41,478 |
Nakamura , et al. |
August 10, 2010 |
Semiconductor device having an improved connection arrangement
between a semiconductor pellet and base substrate electrodes and a
method of manufacture thereof
Abstract
A semiconductor device comprising a semiconductor pellet mounted
on a pellet mounting area of the main surface of a base substrate,
in which first electrode pads arranged on the back of the base
substrate are electrically connected to bonding pads arranged on
the main surface of the semiconductor pellet. The base substrate is
formed of a rigid substrate, and its first electrode pads are
electrically connected to the second electrode pads arranged on its
reverse side. The semiconductor pellet is mounted on the pellet
mounting area of the main surface of the base substrate, with its
main surface downward, and its bonding pads are connected
electrically with the second electrode pads of the base substrate
through bonding wires passing through slits formed in the base
substrate.
Inventors: |
Nakamura; Atsushi (Fuchu,
JP), Nishi; Kunihiko (Kokubunji, JP) |
Assignee: |
Renesas Electronics Corporation
(Kanagawa, JP)
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Family
ID: |
26462600 |
Appl.
No.: |
11/182,040 |
Filed: |
July 15, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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10105236 |
Mar 26, 2002 |
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09613541 |
Jul 7, 2000 |
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Reissue of: |
08570646 |
Dec 11, 1995 |
05777391 |
Jul 7, 1998 |
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Foreign Application Priority Data
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Dec 20, 1994 [JP] |
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6-316444 |
May 25, 1995 [JP] |
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7-126405 |
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Current U.S.
Class: |
257/777; 438/617;
438/128; 257/784; 438/108; 438/107; 438/124; 257/778; 257/E23.001;
257/E21.499; 257/780 |
Current CPC
Class: |
H01L
24/32 (20130101); B29C 45/14655 (20130101); H01L
24/48 (20130101); H01L 24/06 (20130101); H01L
23/49816 (20130101); H01L 23/13 (20130101); H01L
23/49827 (20130101); H01L 24/49 (20130101); H01L
23/3128 (20130101); H01L 24/05 (20130101); H01L
2924/01029 (20130101); H01L 2924/01006 (20130101); H01L
2924/18165 (20130101); H01L 2224/4569 (20130101); H01L
2224/85206 (20130101); H01L 2224/2919 (20130101); H01L
24/45 (20130101); H01L 2924/01033 (20130101); H01L
2924/01082 (20130101); H01L 2924/351 (20130101); H01L
2224/04042 (20130101); H01L 2224/05556 (20130101); H01L
2224/29111 (20130101); H01L 2224/48221 (20130101); H01L
2924/01079 (20130101); B29C 45/0046 (20130101); H01L
2224/06135 (20130101); H01L 2924/01023 (20130101); H01L
2224/05554 (20130101); H01L 2924/15311 (20130101); H01L
2224/48699 (20130101); H01L 2224/32014 (20130101); H01L
2224/45565 (20130101); H01L 2924/00014 (20130101); H01L
2224/48465 (20130101); H01L 2924/18161 (20130101); B29C
45/14836 (20130101); H01L 2924/01005 (20130101); H01L
2224/4824 (20130101); H01L 2224/32225 (20130101); H01L
2924/0132 (20130101); H01L 2224/45147 (20130101); H01L
24/29 (20130101); H01L 2924/0105 (20130101); H01L
2224/0401 (20130101); H01L 2224/73215 (20130101); H01L
2224/06136 (20130101); H01L 2224/48235 (20130101); H01L
2924/181 (20130101); H01L 2224/45144 (20130101); H01L
2224/85207 (20130101); H01L 2224/92247 (20130101); H01L
2224/16 (20130101); H01L 2224/49175 (20130101); H01L
2924/30107 (20130101); H01L 2924/01014 (20130101); H01L
2924/01075 (20130101); H01L 2924/01013 (20130101); H01L
2224/48091 (20130101); H01L 2224/45124 (20130101); H01L
2224/73265 (20130101); H01L 2224/48599 (20130101); H01L
2224/48799 (20130101); H01L 2924/1579 (20130101); H01L
24/73 (20130101); H01L 2224/48227 (20130101); H01L
2224/45124 (20130101); H01L 2924/00014 (20130101); H01L
2224/45144 (20130101); H01L 2924/00014 (20130101); H01L
2224/45147 (20130101); H01L 2924/00014 (20130101); H01L
2224/45565 (20130101); H01L 2224/45144 (20130101); H01L
2224/4569 (20130101); H01L 2224/45565 (20130101); H01L
2224/45147 (20130101); H01L 2224/4569 (20130101); H01L
2224/45565 (20130101); H01L 2224/45124 (20130101); H01L
2224/4569 (20130101); H01L 2224/4569 (20130101); H01L
2924/00014 (20130101); H01L 2224/85206 (20130101); H01L
2924/00014 (20130101); H01L 2224/48091 (20130101); H01L
2924/00014 (20130101); H01L 2224/73215 (20130101); H01L
2224/32225 (20130101); H01L 2224/4824 (20130101); H01L
2224/73265 (20130101); H01L 2224/32225 (20130101); H01L
2224/48227 (20130101); H01L 2224/48465 (20130101); H01L
2224/48227 (20130101); H01L 2224/48465 (20130101); H01L
2224/48227 (20130101); H01L 2924/00 (20130101); H01L
2224/49175 (20130101); H01L 2224/48227 (20130101); H01L
2924/00 (20130101); H01L 2224/49175 (20130101); H01L
2224/48465 (20130101); H01L 2924/00 (20130101); H01L
2924/0132 (20130101); H01L 2924/0105 (20130101); H01L
2924/01082 (20130101); H01L 2224/48227 (20130101); H01L
2924/00 (20130101); H01L 2924/15311 (20130101); H01L
2224/73265 (20130101); H01L 2224/32225 (20130101); H01L
2224/48227 (20130101); H01L 2924/00 (20130101); H01L
2224/48465 (20130101); H01L 2224/4824 (20130101); H01L
2924/00 (20130101); H01L 2224/92247 (20130101); H01L
2224/73265 (20130101); H01L 2224/32225 (20130101); H01L
2224/48227 (20130101); H01L 2924/00 (20130101); H01L
2224/48465 (20130101); H01L 2224/48091 (20130101); H01L
2924/00 (20130101); H01L 2224/13111 (20130101); H01L
2924/01082 (20130101); H01L 2924/00014 (20130101); H01L
2224/48227 (20130101); H01L 2924/00 (20130101); H01L
2224/2919 (20130101); H01L 2924/0695 (20130101); H01L
2224/73265 (20130101); H01L 2224/32225 (20130101); H01L
2224/48227 (20130101); H01L 2924/00012 (20130101); H01L
2924/15311 (20130101); H01L 2224/73265 (20130101); H01L
2224/32225 (20130101); H01L 2224/48227 (20130101); H01L
2924/00012 (20130101); H01L 2224/73215 (20130101); H01L
2224/32225 (20130101); H01L 2224/4824 (20130101); H01L
2924/00012 (20130101); H01L 2224/4824 (20130101); H01L
2224/48465 (20130101); H01L 2924/00 (20130101); H01L
2224/4824 (20130101); H01L 2224/49175 (20130101); H01L
2924/00 (20130101); H01L 2224/4824 (20130101); H01L
2924/00012 (20130101); H01L 2224/2919 (20130101); H01L
2924/0665 (20130101); H01L 2924/00014 (20130101); H01L
2924/15311 (20130101); H01L 2224/73215 (20130101); H01L
2224/32225 (20130101); H01L 2224/4824 (20130101); H01L
2924/00012 (20130101); H01L 2224/48799 (20130101); H01L
2924/00 (20130101); H01L 2924/351 (20130101); H01L
2924/00 (20130101); H01L 2924/00014 (20130101); H01L
2224/05556 (20130101); H01L 2924/181 (20130101); H01L
2924/00012 (20130101); H01L 2924/00014 (20130101); H01L
2224/85399 (20130101); H01L 2924/00014 (20130101); H01L
2224/05599 (20130101); H01L 2224/49175 (20130101); H01L
2224/48465 (20130101); H01L 2924/00 (20130101); H01L
2224/48227 (20130101); H01L 2924/00 (20130101); H01L
2924/15311 (20130101); H01L 2224/73215 (20130101); H01L
2224/32225 (20130101); H01L 2224/4824 (20130101); H01L
2924/00 (20130101); H01L 2224/4824 (20130101); H01L
2224/49175 (20130101); H01L 2924/00 (20130101); H01L
2924/181 (20130101); H01L 2924/00 (20130101) |
Current International
Class: |
H01L
23/48 (20060101); H01L 21/00 (20060101); H01L
23/52 (20060101); H01L 21/44 (20060101) |
Field of
Search: |
;257/777,778,780,784,E23.001,E21.499
;438/107,108,124,126,128,455,456,613,617,637 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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64-81330 |
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Mar 1989 |
|
JP |
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64-081330 |
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Mar 1989 |
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JP |
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2-91345 |
|
Jul 1990 |
|
JP |
|
02-91345 |
|
Jul 1990 |
|
JP |
|
A-5-47829 |
|
Feb 1993 |
|
JP |
|
6-268101 |
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Sep 1994 |
|
JP |
|
A-6-314719 |
|
Nov 1994 |
|
JP |
|
WO-92/05582 |
|
Apr 1992 |
|
WO |
|
Other References
Nikkei electronics 1994.2.28 (No. 602), pp. 11-117, (with
translation). cited by examiner.
|
Primary Examiner: Lee; Hsien-ming
Attorney, Agent or Firm: Antonelli, Terry, Stout &
Kraus, LLP.
Parent Case Text
.Iadd.More than one reissue application has been filed for the
reissue of U.S. Pat. No. 5,777,391. These reissue applications are
Ser. No. 09/613,541, filed Jul. 7, 2000, Ser. No. 10/105,236, filed
on Mar. 26, 2002, which is a continuation of Ser. No. 09/613,541,
Ser. No. 11/182,039 filed on Jul. 15, 2005, which is a continuation
of Ser. No. 10/105,236, the present application Ser. No.
11/182,040, also filed on Jul. 15, 2005, which is another
continuation application of Ser. No. 10/105,236, Ser. No.
11/256,620, filed on Oct. 24, 2005, which is a Continuation of Ser.
Nos. 11/182,039 and 11/182,040, Ser. No. 11/256,621, also filed on
Oct. 24, 2005, which is also a continuation of Ser. Nos. 11/182,039
and 11/182,040, Ser. No. 11/285,730, filed on Nov. 23, 2005 which
is a continuation of Ser. No. 11/182,039 and Ser. No. 11/182,040,
and Ser. No. 11/285,729, filed on Nov. 23, 2005, which is also a
continuation of Ser. No. 11/182,039 and Ser. No. 11/182,040, the
subject matter of which are incorporated by reference
herein..Iaddend.
Claims
What is claimed is:
.[.1. A semiconductor device comprising: (a) a rigid substrate
having a first main surface and a second main surface opposite to
the first main surface; (b) a semiconductor pellet mounted on the
first main surface of the rigid substrate, the semiconductor pellet
having a plurality of semiconductor circuit elements and a
plurality of bonding pads; (c) a plurality of electrode pads formed
on the second main surface of the rigid substrate; and (d) a
plurality of bonding wires for electrically connecting the bonding
pads of the semiconductor pellet with the electrode pads; wherein
the semiconductor pellet is mounted facedown on the rigid
substrate, the rigid substrate has slits that extend from the first
main surface to the second main surface and expose the bonding pads
of the semiconductor pellet, the bonding wires extend through the
slits in the rigid substrate to connect the bonding pads and the
electrode pads, and bump electrodes are formed on said electrode
pads..].
.[.2. A semiconductor device according to claim 1, wherein the
bonding pads are arranged at the periphery of the semiconductor
pellet and the slits are formed along the directions of rows of the
bonding pads..].
.[.3. A semiconductor device according to claim 2, wherein the
electrode pads are located on both sides of the slits..].
.[.4. A semiconductor device according to claim 3, wherein the
electrode pads located on one side of the slits and under the
semiconductor pellet are power supply pads, and the electrode pads
located on the other side of the slits and outside the
semiconductor pellet are signal pads..].
.[.5. A semiconductor device according to claim 1, further
comprising a first resin sealing body covering the semiconductor
pellet..].
.[.6. A semiconductor device according to claim 5, further
comprising a second resin sealing body formed in the slits and
covering the bonding wires..].
.[.7. A semiconductor device according to claim 1, wherein said
rigid substrate is formed by glass fibers impregnated with epoxy
resin..].
.[.8. A method of manufacturing a semiconductor device in which a
semiconductor pellet is mounted on a pellet mounting area of the
main surface of a rigid base substrate and in which first electrode
pads arranged on the back of the rigid base substrate are
electrically connected to bonding pads arranged on the main surface
of the semiconductor pellet, said method comprising: a step of
mounting the semiconductor pellet, with its main surface downward,
on the pellet mounting area of the main surface of the rigid base
substrate a step of electrically connecting the bonding pads of the
semiconductor pellet and second electrode pads electrically
connected to the first electrode pads of the rigid base substrate
and arranged on the back of the rigid base substrate through
bonding wires passing through slits formed on the rigid base
substrate; and a step of forming bump electrodes on the first
electrode pads..].
.[.9. A method of manufacturing a semiconductor device according to
claim 9, further comprising a step of forming by transfer molding a
resin sealing body that covers the periphery of the main surface of
the rigid base substrate and seals the bonding wires, after the
step of electrically connecting the bonding wires..].
.[.10. A semiconductor device according to claim 10, wherein said
rigid substrate is formed by glass fibers impregnated with
polyimide resin..].
.[.11. A semiconductor device comprising: (a) a rigid substrate
having a first main surface and a second main surface opposite to
the first main surface; (b) a semiconductor pellet mounted on the
first main surface of the rigid substrate, the semiconductor pellet
having a plurality of semiconductor circuit elements and a
plurality of bonding pads; (c) a plurality of electrode pads formed
on the second main surface of the rigid substrate; and (d) a
plurality of bonding wires for electrically connecting the bonding
pads of the semiconductor pellet with the electrode pads; wherein
the semiconductor pellet is mounted facedown on the rigid
substrate, the rigid substrate has slits that extend from the first
main surface to the second main surface and expose the bonding pads
of the semiconductor pellet, and the bonding wires extend through
the slits in the rigid substrate to connect the bonding pads and
the electrode pads; wherein the bonding pads are arranged at the
periphery of the semiconductor pellet and the slits are formed
along the directions of rows of the bonding pads..].
.[.12. A semiconductor device according to claim 11, wherein the
electrode pads are located on both sides of the slits..].
.[.13. A semiconductor device according to claim 12, wherein the
electrode pads located on one side of the slits and under the
semiconductor pellet are power supply pads, and the electrode pads
located on the other side of the slits and outside the
semiconductor pellet are signal pads..].
.[.14. A semiconductor device comprising: a substrate of a
quadrilateral shape having a first pair of opposed edges and a
second pair of opposed edges, said substrate having a first main
surface, a second main surface opposite to said first main surface
and a first slit and a second slit each extending from said first
main surface to said second main surface, said first slit extending
along one of said first pair of opposed edges, said second slit
extending along the other of said first pair of opposed edges, said
substrate having first electrode pads on said second main surface
in a first area between said first and second slits, second
electrode pads on said second main surface in a second area between
said first slit and said one of the first pair of opposed edges,
and third electrode pads on said second main surface in a third
area between said second slit and the other of the first pair of
opposed edges; a semiconductor pellet having a main surface with
semiconductor elements and bonding pads, said semiconductor pellet
being mounted on said first main surface of substrate such that
said bonding pads are arranged to be in line with said first and
second slits; bonding wires extending through said first and second
slits in said substrate and electrically connecting said bonding
pads and said first to third electrode pads, respectively; a resin
member sealing said semiconductor pellet and said bonding wires;
and bump electrodes arranged on said second main surface of said
substrate in said first to third areas in a direction of said first
pair of opposed edges and being electrically connected with said
first to third electrode pads, wherein said bump electrodes in said
second and third areas are arranged to form plural rows in a
direction of at least one of said second pair of opposed edges,
respectively..].
.[.15. A semiconductor device according to claim 14, wherein said
semiconductor pellet has a quadrilateral shape and has a third pair
of opposed edges and a fourth pair of opposed edges, wherein said
bonding pads are arranged in a peripheral portion of said main
surface and extend along said third pair of opposed edges..].
.[.16. A semiconductor device according to claim 15, wherein said
semiconductor pellet is mounted on said first main surface opposite
to said first area, wherein said substrate has a larger size than
that of said semiconductor pellet, and wherein said bump electrodes
in said second and third areas are located outside said third pair
of opposed edges..].
.[.17. A semiconductor device according to claim 14, wherein the
number of said bump electrodes in said second and third areas is
larger than the number of said bump electrodes in said first
area..].
.[.18. A semiconductor device according to claim 14, wherein said
semiconductor pellet has a rear surface opposite to said main
surface, and wherein said rear surface of said semiconductor pellet
is exposed from said resin member..].
.[.19. A semiconductor device according to claim 14, wherein the
number of said bump electrodes in said second area is larger than
the number of said bump electrodes in said first area..].
.[.20. A semiconductor device according to claim 14, wherein said
semiconductor pellet has a rear surface opposite to said main
surface, and wherein said rear surface of said semiconductor pellet
is exposed from said resin member..].
.[.21. A semiconductor device according to claim 14, wherein said
first electrode pads extend along said first and second slits,
respectively, said second electrode pads extend along said first
slit, and said third electrode pads extend along said second slit,
wherein said first to third electrode pads are arranged at a first
pitch, respectively, wherein said bonding pads in said first and
second slits are arranged at a second pitch which is smaller than
said first pitch, respectively, wherein said bonding wires in said
first slit alternately connect said bonding pads in said first slit
with said first and second electrode pads, and wherein said bonding
wires in said second slit alternately connect said bonding pads in
said second slit with said first and third electrode pads..].
.[.22. A semiconductor device comprising: a substrate of a
quadrilateral shape having first to fourth edges, said substrate
having a first main surface, a second main surface opposite to said
first main surface and first to fourth slits extending from said
first main surface to said second main surface, said first to
fourth slits respectively extending along said first to fourth
edges and defining a first area of said substrate surrounded by
said first to fourth slits and a second area of said substrate
extending outside said first to fourth slits, said substrate having
first electrode pads on said second main surface in said first area
and second electrode pads on said second main surface in said
second area; a semiconductor pellet having a main surface with
semiconductor elements and bonding pads, said semiconductor pellet
being mounted on said first main surface of substrate such that
said bonding pads are arranged in line with said first to fourth
slits; bonding wires extending through said first to fourth slits
in said substrate and electrically connecting said bonding pads and
said first and second electrode pads, respectively; a resin member
sealing said semiconductor pellet and said bonding wires; and bump
electrodes arranged on said second main surface of said substrate
in said first and second areas and being electrically connected
with said first and second electrode pads, wherein said bump
electrodes in said second area are arranged to form a plurality of
rows such that said plurality of rows are formed relative to one
another to surround said first area of substrate..].
.[.23. A semiconductor device according to claim 22, wherein said
semiconductor pellet has a quadrilateral shape and has first to
fourth edges, wherein said bonding pads are arranged in a
peripheral portion of said main surface and extend along said first
to fourth edges of said semiconductor pellet..].
.[.24. A semiconductor device according to claim 23, wherein said
semiconductor pellet is mounted on said first main surface opposite
to said first area, wherein said substrate has a larger size than
that of said semiconductor pellet, and wherein said bump electrodes
in said second area are located outside said first to fourth edges
of said semiconductor pellet..].
.[.25. A semiconductor device according to claim 22, wherein said
first and second electrode pads extending along said first to
fourth slits, respectively, and are arranged at a first pitch,
wherein said bonding pads extend along said first and second
electrode pads and are arranged at a second pitch which is smaller
than said first pitch, and wherein said bonding wires alternately
connect said bonding pads with said first and second electrode
pads..].
.Iadd.26. A method of manufacturing a semiconductor device
comprising the steps of: (a) providing a semiconductor pellet and a
substrate, said semiconductor pellet having a circuit system and
bonding pads formed on a main surface thereof, said substrate
having a first surface, a second surface opposite to said first
surface, electrode pads formed on said second surface and a slit
passing through said substrate from said first surface to said
second surface; (b) mounting said semiconductor pellet over said
substrate such that said main surface of said semiconductor pellet
is faced to said first surface of said substrate and said bonding
pads are arranged to be aligned with said slit in a plan view, and
such that a portion of said slit is arranged at the outside of said
semiconductor pellet in said plan view; (c) electrically connecting
said electrode pads of said substrate with said bonding pads of
said semiconductor pellet by bonding wires via said slit
respectively; (d) after the step (c), forming a resin sealing body
on said first and second surfaces of said substrate, said resin
sealing body formed on said first surface side of said substrate
being positioned around of said semiconductor pellet in a plane
view, said resin sealing body on said first and second surfaces of
said substrate being formed in unitary to each other via said slit,
and sealing said bonding wires; and (e) forming bump electrodes on
said second surface of said substrate such that said bump
electrodes are electrically connected to said electrode pads of
said substrate, wherein said resin sealing body in the step (d) is
formed by a transfer molding method using a molding die; wherein
said resin sealing body includes a first portion on said first
surface of said substrate, a second portion on said second surface
of said substrate and a third portion in said slit; and wherein
from said first to third portions of said resin sealing body are
continuously formed to one another..Iaddend.
.Iadd.27. A method of manufacturing a semiconductor device
according to claim 26, wherein said molding die has an upper die
and a lower die, wherein said lower die of said molding die has a
cavity defined by a recess of said lower die, wherein the step (d)
includes a step of setting assembly comprising said substrate and
said semiconductor pellet at said molding die such that a part of
said bonding wires and said electrode pads are placed in said
cavity defined by said recess of said lower die, and wherein said
resin material is supplied into said cavity through said slit of
said substrate by said transfer molding method..Iaddend.
.Iadd.28. A method of manufacturing a semiconductor device
according to claim 26, wherein said resin material is made from
resin containing filler..Iaddend.
.Iadd.29. A method of manufacturing a semiconductor device
according to claim 26, wherein said substrate is a rigid substrate
formed of a glass fiber impregnated with resin..Iaddend.
.Iadd.30. A method of manufacturing a semiconductor device
according to claim 29, wherein said resin included in said
substrate is epoxy resin, polyimide resin or maleimide
resin..Iaddend.
.Iadd.31. A method of manufacturing a semiconductor device
according to claim 29, wherein said bonding wires are formed of
gold, wherein connection of said bonding wires is accomplished by
ultrasonic thermo-compression bonding in the step (c)..Iaddend.
.Iadd.32. A method of manufacturing a semiconductor device
according to claim 26, wherein said bump electrodes are formed such
that a thickness of in a thickness direction of said substrate is
smaller than a height of each of said bump electrodes in said
thickness direction of said substrate..Iaddend.
.Iadd.33. A method of manufacturing a semiconductor device
according to claim 32, wherein said bump electrodes are formed of a
Pb-Sn alloy..Iaddend.
.Iadd.34. A method of manufacturing a semiconductor device
according to claim 32, wherein said bump electrodes are formed to
provide an electrical and mechanical connection to a mounting
board, at the side of said second surface of said
substrate..Iaddend.
.Iadd.35. A method of manufacturing a semiconductor device
according to claim 26, wherein said bonding pads are arranged in a
first direction along a side of said semiconductor pellet, wherein
said portion of said slit arranged at the outside of said
semiconductor pellet is along said side of said semiconductor
pellet, wherein said resin sealing body in the step (d) is formed
by a transfer molding method, and wherein the formation of said
resin sealing body includes a step of providing a resin material in
said slit from a second direction which is substantially
perpendicular to said first direction..Iaddend.
.Iadd.36. A semiconductor device comprising: (a) a semiconductor
pellet and a substrate, said semiconductor pellet having a circuit
system and bonding pads formed on a main surface thereof, said
substrate having a first surface, a second surface opposite to said
first surface, electrode pads formed on said second surface and a
slit passing through said substrate from said first surface to said
second surface; (b) wherein said semiconductor pellet is mounted
over said substrate such that said main surface of said
semiconductor pellet is faced to said first surface of said
substrate and said bonding pads are arranged to be aligned with
said slit in a plan view, and such that a portion of said slit is
arranged at the outside of said semiconductor pellet in said plan
view; (c) wherein said electrode pads of said substrate are
electrically connected with said bonding pads of said semiconductor
pellet by bonding wires via said slit; (d) a resin sealing body
formed on said first and second surfaces of said substrate, said
resin sealing body formed on said first surface side of said
substrate being positioned around of said semiconductor pellet in a
plane view, said resin sealing body on said first and second
surfaces of said substrate being formed in unitary to each other
via said slit, and sealing said bonding wires; and (e) bump
electrodes formed on said second surface of said substrate such
that said bump electrodes are electrically connected to said
electrode pads of said substrate, respectively, wherein said resin
sealing body includes a first portion on said first surface of said
substrate, a second portion of said second surface of said
substrate and a third portion in said slit; and wherein from said
first to third portions of said resin sealing body are continuously
formed to one another..Iaddend.
.Iadd.37. A semiconductor device according to claim 36, wherein
said substrate is a rigid substrate formed of a glass fiber
impregnated with resin..Iaddend.
.Iadd.38. A semiconductor device according to claim 37, wherein
said resin included in said substrate is epoxy resin, polyimide
resin or maleimide resin..Iaddend.
.Iadd.39. A semiconductor device according to claim 37, wherein
said bonding wires are formed of gold, and wherein connection of
said bonding wires is accomplished by ultrasonic thermo-compression
bonding..Iaddend.
.Iadd.40. A semiconductor device according to claim 36, wherein
said resin material is made from resin containing
filler..Iaddend.
.Iadd.41. A semiconductor device according to claim 36, wherein
said bump electrodes are formed such that a thickness of in a
thickness direction of said substrate is smaller than a height of
each of said bump electrodes in said thickness direction of said
substrate..Iaddend.
.Iadd.42. A semiconductor device according to claim 41, wherein
said bump electrodes are formed of a Pb-Sn alloy..Iaddend.
.Iadd.43. A semiconductor device according to claim 41, wherein
said bump electrodes are formed to provide an electrical and
mechanical connection to a mounting board, at the side of said
second surface of said substrate..Iaddend.
.Iadd.44. A semiconductor device according to claim 36, wherein
said bonding pads are arranged in a first direction along a side of
said semiconductor pellet, and wherein said portion of said slit
arranged at the outside of said semiconductor pellet is along said
side of said semiconductor pellet..Iaddend.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device and a
method of manufacture thereof and more particularly to a technology
effectively applied to a semiconductor device and a method of
manufacture thereof, the device having a structure in which a
semiconductor pellet is mounted on a pellet mounting area on the
main surface of a base substrate and in which a first electrode pad
on the back of the base substrate is electrically connected to an
external terminal on the main surface of the semiconductor
pellet.
A semiconductor device with a ball grid array (BGA) structure has
been introduced as a semiconductor device having a high level of
integration in the Nikkei Electronics, Feb. 28, 1994, pp. 111-117,
published by Nikkei McGraw-Hill. The BGA structure of such as
semiconductor device, as shown in FIG. 16 (cross section of an
essential part), has a semiconductor pellet 2 mounted on a pellet
mounting area of the main surface of the base substrate 1 and a
plurality of bump electrodes 4 arranged in grid on the back of the
base substrate 1 opposite the main surface.
The base substrate 1 may be made from a printed wiring board of
two-layer wiring structure. Second electrode pads 1A are arranged
in a peripheral area of the main surface of the base substrate 1
(around the pellet mounting area), while first electrode pads 1B
are arranged on the back of the base substrate 1 opposite the main
surface. The second electrode pads 1A are electrically connected to
through-hole conductors 1C via conductors 1A.sub.1 arranged on the
main surface of the base substrate 1. The first electrode pads 1B
are electrically connected to the through-hole conductors 1C via
conductors 1B.sub.1 arranged on the back of the base substrate
1.
The semiconductor pellet 2 may comprise mainly a semiconductor
substrate 2B of single-crystal silicon. On the main surface of the
semiconductor substrate 2B (device forming surface) is formed a
logic circuit system, a memory circuit system or a combination of
these. A plurality of bonding pads 2A are arranged on the main
surface of the semiconductor substrate 2B. The bonding pads 2A are
formed in the top of the interconnect layers formed on the main
surface of the semiconductor substrate 2B.
The bonding pads 2A on the semiconductor pellet 2 are electrically
connected to the second electrode pads 1A on the main surface of
the base substrate 1 through bonding wires 6. In other words, the
bonding pads 2A on the semiconductor pellet 2 are electrically
connected to the first electrode pads 1B through the bonding wires
6, second electrode pads 1A, conductors 1A.sub.1, through-hole
conductors 1C and conductors 1B.sub.1.
The semiconductor pellet 2 and the bonding wires 6 are sealed with
a resin sealing body 7 formed on the main surface of the base
substrate 1. The resin sealing body 7 is formed by transfer
molding.
The bump electrodes 4 are electrically and mechanically connected
to the surfaces of the first electrode pads 1B on the base
substrate 1. The bump electrodes 4 may be formed from an alloy
material, such as Pb-Sn.
The semiconductor device of such a BGA structure is mounted on a
mounting board, with the bump electrodes 4 electrically and
mechanically connected to electrode pads arranged on the mounting
surface of the mounting board.
Another example of semiconductor device having a high circuit
density is disclosed in U.S. Pat. Ser. No. 5148265, which shows a
semiconductor device in which the base substrate is made from a
filmlike flexible substrate. In this semiconductor device, the
semiconductor pellet is mounted, with its main surface downward, on
the pellet mounting area of the main surface of the base substrate
made of a flexible substrate, and the bonding pads arranged on the
main surface of the semiconductor pellet are electrically connected
to the second electrode pads arranged on the back of the base
substrate through the bonding wires. The second electrode pads on
the base substrate are electrically connected to the first
electrode pads on the back of the base substrate through conductors
that are also arranged on the back. Bump electrodes are
electrically and mechanically connected to the surfaces of the
first electrode pads.
The semiconductor device of the above construction is mounted on
the mounting surface of a mounting board, with its bump electrodes
electrically and mechanically connected to the electrode pads
arranged on the mounting surface of the mounting board.
SUMMARY OF THE INVENTION
In the semiconductor device with the BGA structure, as shown in
FIG. 16, the second electrode pads 1A arranged on the main surface
of the base substrate 1 are electrically connected through the
through-hole conductors 1C to the first electrode pads 1B arranged
on the back of the base substrate 1. The through-hole conductors 1C
comprises a hole area formed within a through-hole in the base
substrate 1 and a land area (fringe portion) formed on the main
surface and back surface of the base substrate 1. The inner
diameter of the through-hole may be around 0.3 mm and the outer
diameter of the land area of the through-hole conductor 1C may be
about 0.6 mm. The inner diameter of the through-hole and the outer
diameter of the land area of the through-hole conductor 1C are set
large compared to the widths of the conductors 1A.sub.1
electrically connecting the second electrode pads 1A and the
through-hole conductors 1C and also compared to the widths of the
conductors 1B.sub.1 electrically connecting the first electrode
pads 1B and the through-hole conductors 1C.
The circuit systems formed on the typical semiconductor pellets 2
have tended to grow in their level of integration and the number of
functions they perform. With enhanced integration and more
diversified functions of the circuit system, the number of bonding
pads 2A of the semiconductor pellet 2 and the number of second
electrode pads 1A of the base substrate 1 increase. That is, the
number of through-hole conductors 1C electrically connecting the
second electrode pads 1A and the first electrode pads 1B increases
as the integration and function of the circuit system are enhanced.
Hence, there has been a problem that the external size of the base
substrate 1 increase with the increasing number of the through-hole
conductors 1C, which in turn increases the size of the
semiconductor device as a whole.
There is also another problem which the inventors have considered.
The intervals between the through-hole conductors formed by copper
foil thick film printing, etching or electroplating techniques are
greater than the intervals of the bonding pads of the semiconductor
pellet formed by photolithography. For this reason, in a
semiconductor device with the BGA structure, as the number of the
through-hole conductors 1C increases, they are positioned outwardly
away from the semiconductor pellet 2. This inevitably extends the
length of the conductors 1A.sub.1 electrically connecting the
second electrode pads 1A and the through-hole conductors 1C and the
length of the conductors 1B.sub.1, electrically connecting the
first electrode pads 1B and the through-hole conductors 1C. This,
in turn, increases inductance and reduces the operating speed of
the semiconductor device.
In the semiconductor device using a flexible substrate for the base
substrate, the flexible substrate may for example be formed of a
polyester film or polyimide film. This flexible substrate has a
small Young's modulus and is soft (low hardness) compared with a
rigid substrate impregnated with epoxy resin or polyimide resin, as
represented by the FR4 substrate according to the NEMA Standard.
Therefore, when the bonding pads arranged on the main surface of
the semiconductor pellet are connected with the second electrode
pads arranged on the back of the base substrate through bonding
wires, the bonding force applied to the second electrode pads is
absorbed by the base substrate, preventing the bonding force and
ultrasonic vibrations from being transmitted to the second
electrode pads effectively. This gives rise to an apprehension that
the connection strength between the bonding wires and the second
electrode pads may decrease, leading to connection failures of
bonding wires and reduced electric reliability of the semiconductor
device.
In semiconductor devices that use a flexible substrate for the base
substrate, the flexible substrate has a large thermal expansion
coefficient in the planar direction and a small Young's modulus
(small rigidity), which means that it is easy to bend, compared
with the rigid substrate. Therefore, when the semiconductor device
is mounted on the mounting surface of the mounting board, the
reflow heat used during the process of mounting causes deformations
to the base substrate, such as warping and twisting, which in turn
reduces the flatness of the back of the base substrate with respect
to the mounting surface of the mounting board, thereby lowering the
mounting precision of the semiconductor device.
An object of this invention is to provide a technology that allows
a reduction in the size of the semiconductor device.
Another object of this invention is to provide a technology that
allows an increase in the operating speed of the semiconductor
device.
Still another object of this invention is to provide a technology
that can enhance electric reliability of the semiconductor
device.
A further object of this invention is to provide a technology that
can enhance mounting precision of the semiconductor device.
A further object of this invention is to provide a manufacturing
technology for the semiconductor device that can accomplish the
above objectives.
These and other objects and novel features of this invention will
become apparent from the following description of this
specification and the accompanying drawings.
Representative aspects of this invention may be briefly summarized
as follows.
A semiconductor device in accordance with invention comprises a
semiconductor pellet mounted on the pellet mounting area of the
main surface of the base substrate, in which first electrode pads
arranged on the back of the base substrate are electrically
connected to the bonding pads on the main surface of the
semiconductor pellet. The base substrate is formed of a rigid
substrate, and its first electrode pads are electrically connected
to second electrode pads also arranged on the back side of the base
subtrate. The semiconductor pellet is mounted, with its main
surface downward, on the pellet mounting area of the main surface
of the base substrate, and its bonding pads are electrically
connected to the second electrode pads on the base substrate
through bonding wires extending through slits formed in the base
substrate.
A method of manufacturing a semiconductor device is also provided,
in which a semiconductor pellet is mounted on the pellet mounting
area of the main surface of the base substrate and in which first
electrode pads arranged on the back of the base substrate are
electrically connected to the bonding pads on the main surface of
the semiconductor pellet. In particular, the method includes a step
of mounting the semiconductor pellet, with its main surface
downward, on the pellet mounting area of the main surface of the
base substrate made of a rigid substrate, and a step of connecting
the bonding pads on the semiconductor pellet to the second
electrode pads electrically connected to the first electrode pads
of the base substrate and arranged on the back of the base
substrate through bonding wires extending through slits formed in
the base substrate.
According to the above construction of this invention, the bonding
pads of the semiconductor pellet and the first electrode pads of
the base substrate can be electrically connected through the
bonding wires and the second electrode pads, so it is possible to
eliminate the through holes used to electrically connect the second
electrode pads and the first electrode pads in prior structures.
This allows the external size of the base substrate to be reduced
by an amount corresponding to an area occupied by the through holes
(land area), thus reducing the size of the semiconductor device as
a whole.
Further, because the first electrode pads can be put closer to the
second electrode pads by an amount corresponding to an area
occupied by the through holes, the conductors of the base substrate
that electrically connect the second electrode pads and the first
electrode pads can be reduced in length. As a result, inductance
can be reduced and the operating speed of the semiconductor device
increased.
Further, the rigid substrate has a higher Young's modulus than a
flexible substrate; therefore, when the bonding pads arranged on
the main surface of the semiconductor pellet and the second
electrode pads arranged on the back of the base substrate are
electrically connected by bonding wires, the bonding force applied
to the second electrode pads can be prevented from being absorbed
by the base substrate. This assures effective transmission of the
bonding force and the ultrasonic vibrations to the second electrode
pads. Thus, the connection strength between the bonding wires and
the second electrode pads is increased, making it possible to
prevent connection failure of the bonding wires and to enhance
electric reliability of the semiconductor device.
Furthermore, the rigid substrate has a small inplane thermal
expansion coefficient and a high Young's modulus compared with a
flexible substrate, which means the rigid substrate is harder to
bend. This prevents the base substrate from being deformed (warped
or twisted) due to reflow heat produced during the process of
mounting the semiconductor device on the mounting surface of the
mounting board. This ensures a sufficient flatness of the back of
the base substrate with respect to the mounting surface of the
mounting board, thus enhancing the mounting precision of the
semiconductor device.
According to the above-mentioned manufacturing method of this
invention, the bonding pads of the semiconductor pellet and the
first electrode pads of the base substrate are electrically
connected through bonding wires and second electrode pads, so the
through holes electrically connecting the second electrode pads and
the first electrode pads can be eliminated, making it possible to
use a base substrate reduced in external size by an amount
corresponding to the occupied area of the through holes. This in
turn allows the manufacture of reduced-size semiconductor
devices.
Further, because the bonding pads of the semiconductor pellet and
the first electrode pads of the base substrate are electrically
connected through bonding wires and second electrode pads, the
through holes electrically connecting the second electrode pads and
the first electrode pads can be eliminated, making it possible to
use a base substrate whose conductors electrically connecting the
second electrode pads and the first electrode pads are reduced by a
length corresponding to the occupied area of the through holes.
This in turn allows the manufacture of semiconductor devices with
faster operating speeds.
The base substrate uses a rigid substrate having a high Young's
modulus compared with a flexible substrate; therefore, when the
bonding pads arranged on the main surface of the semiconductor
pellet and the second electrode pads arranged on the back of the
base substrate are electrically connected by bonding wires, the
bonding force applied to the second electrode pads can be prevented
from being absorbed by the base substrate, ensuring effective
transfer of the bonding force and ultrasonic vibrations to the
second electrode pads. This enhances the connection strength
between the bonding wires and the second electrode pads, allowing
the manufacture of the semiconductor device with high electric
reliability.
Furthermore, the base substrate used is formed of a rigid substrate
having a small planar thermal expansion coefficient and a high
Young's modulus compared with those of a flexible substrate, which
means the rigid substrate is harder to bend. As a result, the rigid
base substrate is free from deformations (warping or twisting) due
to reflow heat during the process of mounting the semiconductor
device on the mounting surface of the mounting board. As a result,
a sufficient degree of flatness of the back of the base substrate
with respect to the mounting surface of the mounting board can be
secured, which in turn allows the manufacture of semiconductor
devices with high mounting precision.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view of the main surface side of the semiconductor
device, as a first embodiment of this invention, that employs a BGA
structure;
FIG. 2 is a cross section taken along the line A--A of FIG. 1:
FIG. 3 is an enlarged cross section of an essential part of FIG.
2;
FIG. 4 is an enlarged plan view showing the state of the back side
of an essential part of the semiconductor device with the resin
sealing body removed;
FIG. 5 is a cross section showing an essential part of a molding
die for the resin sealing body of the semiconductor device;
FIG. 6 is a cross section showing the method of manufacturing the
semiconductor device;
FIG. 7 is a cross section of an essential part of the semiconductor
device showing the method of manufacture thereof;
FIG. 8 is a cross section of an essential part of the semiconductor
device showing the method of manufacture thereof;
FIG. 9 is a cross section of an essential part of the semiconductor
device showing the method of manufacture thereof; FIG. 10 is a
cross section showing an essential part of the semiconductor device
mounted on a mounting board;
FIG. 11 is a cross section showing a variation of the semiconductor
device;
FIG. 12 is a cross section of the semiconductor device, as a second
embodiment of this invention, that employs the BGA structure;
FIG. 13 is an enlarged plan view showing the state of the back side
of an essential part of the semiconductor device with the resin
sealing body removed;
FIG. 14 is a plan view showing the state of the back side of an
essential part of the semiconductor device, as a third embodiment
of this invention, that employs the BGA structure with the resin
sealing body removed;
FIG. 15 is a plan view showing the state of the back side of an
essential part of the semiconductor device, as a fourth embodiment
of this invention, that employs the BGA structure and is removed of
the resin sealing body removed; and
FIG. 16 is a cross section showing an essential part of the
semiconductor device that employs the conventional BGA
structure.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The construction of this invention is described in the following in
conjunction with embodiments that apply this invention to a
semiconductor device using the BGA structure.
In the drawings used for explaining the embodiments, components
with identical functions are given like reference numerals and
their explanations are not repeated.
Embodiment 1
The outline construction of a semiconductor device, as a first
embodiment of this invention, that uses the BGA structure is shown
in FIG. 1 (plan view of the main surface side), FIG. 2 (cross
section taken along the line A--A of FIG. 1), FIG. 3 (enlarged
cross section of an essential part of FIG. 2) and FIG. 4 (enlarged
plan view showing the back side of an essential part of the
semiconductor device with the resin sealing body removed).
As shown in FIGS. 1, 2, 3 and 4, the semiconductor device has a
semiconductor pellet 2 mounted on a pellet mounting area of the
main surface of a base substrate 1, with a plurality of bump
electrodes 4 arranged in grid on the back of the base substrate 1
opposite the main surface.
The base substrate 1 may be formed of a printed circuit board. The
printed circuit board may, for example, have a structure in which
wiring is formed over the surface of a rigid substrate of glass
fiber impregnated with epoxy resin, polyimide resin or maleimide
resin. In other words, the base substrate 1 is formed of a rigid
substrate. The rigid substrate has a high Young's modulus and is
hard compared with a flexible substrate made of polyester film or
polyimide film. The rigid substrate has a small thermal expansion
coefficient in a planar direction, a high Young's modulus and is
difficult to bend compared with the flexible substrate. For
example, the rigid substrate made of a glass fiber impregnated with
epoxy resin or polyimide resin has a Young's modulus of around
16-22 GPa and a thermal expansion coefficient of about
10-20.times.10.sup.-61/.degree. C. Flexible substrates made of
polyester film or polyimide film have a Young's modulus of about
2-5 GPa and a thermal expansion coefficient of about
20-25.times.10.sup.-61/.degree. C.
On the back of the base substrate 1 are formed a plurality of
second electrode pads 1A and first electrode pads 1B, which are
electrically interconnected through conductors 1B.sub.1 on the back
of the base substrate 1. The second electrode pads 1A, first
electrode pads 1B and conductors 1B.sub.1 are formed of a Cu film,
for example.
On the surfaces of the first electrode pads 1B are formed bump
electrodes 4 that are electrically and mechanically connected to
them. The bump electrodes 4 may be formed of, for instance, a Pb-Sn
alloy.
The semiconductor pellet 2 is mounted, with its main surface
(underside in FIG. 2 and 3) downward, on the pellet mounting area
of the main surface of the base substrate 1. That is, the
semiconductor pellet 2 is mounted facedown on the pellet mounting
area of the main surface of the base substrate 1. Interposed
between the main surface of the semiconductor pellet 2 and the
pellet mounting area of the main surface of the base substrate 1 is
an insulating layer 3, which may be formed of a polyimide-, epoxy-
or silicon-base low-elasticity resin.
The semiconductor pellet 2 may be rectangular and may mainly be
comprised of a semiconductor substrate 2B made of single-crystal
silicon. On the main surface (device forming surface) of the
semiconductor substrate 2B are formed a logic circuit system, a
memory circuit system or a combination of these. Also on the main
surface of the semiconductor substrate 2B, a plurality of bonding
pads 2A are arranged along the sides of the rectangular surface.
The bonding pads 2A are formed on the top of interconnect layers on
the main surface of the semiconductor substrate 2B. That is, the
bonding pads 2A are arranged in the periphery of the main surface
of the semiconductor pellet 2 along each of the four sides.
The bonding pads 2A of the semiconductor pellet 2 and the second
electrode pads 1A of the base substrate 1 are electrically
connected to each other through bonding wires 6 running in slits 5
formed in the base substrate 1. The bonding wires 6 may be of gold
(AU), copper (Cu) or aluminum (Al), and may be coated with
insulating resin. The bonding wires 6 may be connected by a bonding
method that utilizes ultrasonic vibrations in combination with
thermo-compression.
The slits 5 in the base substrate 1 are formed in the directions of
the rows of the bonding pads 2A that are arranged along each side
of the main surface of the semiconductor pellet 2. That is, the
base substrate 1 of this embodiment has four slits 5, each of which
is located above the bonding pads 2A of the semiconductor pellet
2.
The second electrode pads 1A of the base substrate 1 are placed in
both areas of the back of the base substrate 1 divided by the slits
5. The second electrode pads 1A located in one of the areas of the
back of the base substrate 1 demarcated by the slits 5 (inside the
semiconductor pellet 2) are supplied with a power supply such as an
operation voltage (3.3 V for instance) and a reference voltage (0 V
for instance). The second electrode pads 1A located in the other
area of the back of the base substrate 1 demarcated by the slits 5
(outside the semiconductor pellet 2) receive a signal such as an
input/output signal and a control signal.
The semiconductor pellet 2 are provided with 100 bonding pads 2A on
each side at a pitch of about 100 .mu.m. The number of bonding pads
2A is increased as the level of integration and the operating speed
of the circuit system mounted on the semiconductor pellet 2
increase.
The first area of the back of the base substrate 1 demarcated by
the slits 5 is provided with, for example, 50 second electrode pads
1A for each side of the semiconductor pellet 2; and the second area
is provided with, for instance, 50 second electrode pads 1A for
each side of the semiconductor pellet 2. Because the second
electrode pads 1A cannot be made as small as the bonding pads 2A of
the semiconductor pellet 2, the pitch of the second electrode pads
1A is set wider than that of the bonding pads 2A, for instance, at
around 200 .mu.m. That is, because the second electrode pads 1A of
the base substrate 1 are arranged in two rows for each side of the
semiconductor pellet 2, the length of the second electrode pads 1A
corresponding to one side of the semiconductor pellet 2 can be made
almost equal to that of the bonding pads 2A arranged along one side
of the semiconductor pellet 2 even if the pitch of the second
electrode pads 1A of the base substrate 1 is set to two times that
of the bonding pads 2A of the semiconductor pellet 2. Furthermore,
the second electrode pads 1A of the base substrate 1 can be located
at positions facing the corresponding bonding pads 2A of the
semiconductor pellet 2.
The peripheral area of the main surface of the base substrate 1
excluding the pellet mounting area is covered with a resin sealing
body 7, which seals the bonding wires 6. That is, the resin sealing
body 7 is formed on the main surface side and the back surface side
of the base substrate 1. The resin sealing body 7 is made from
epoxy resin 7A containing a phenol-base hardener, silicone rubber
and filler for reducing stresses.
The back of the base substrate 1 facing the main surface of the
semiconductor pellet 2 is exposed from the resin sealing body 7
that covers the peripheral area of the base substrate 1.
The resin sealing body 7 is formed by the transfer molding that
uses a molding die 10 shown in FIG. 5 (cross section of an
essential part). The molding die 10 has a cavity 11 defined by an
upper die 10A and a lower die 10B, an inflow gate 13 connected to
the cavity 11, and, though not shown, a pot and a runner. The pot
communicates with the cavity 11 through the runner and the inflow
gate 13.
The cavity 11 comprises a recess 11A formed in the upper die 10A
and a recess 11B formed in the lower die 10B. The resin 7A is
supplied into the recess 11A from the pot through the runner and
the inflow gate 13. The base substrate 1 is placed in the recess
11B.
The recess 11B is formed with recesses 12, which are located at
positions facing the slits 5 of the base substrate 1 and which
extend in the same directions as the slits 5. Placed in the
recesses 12 are a part of bonding wires 6 electrically connecting
the bonding pads 2A of the semiconductor pellet 2 and the second
electrode pads 1A of the base substrate 1, and also the second
electrode pads 1A of the base substrate 1. The resin 7A is supplied
from the recess 11A through the slits 5 of the base substrate 1
into the recess 11A.
Though not shown in FIG. 12, the recesses 12 are provided with a
gas vent to prevent voids due to bubbles.
Next, the method of manufacturing the above-mentioned semiconductor
device is described by referring to FIGS. 6 through FIG. 9.
First, a base substrate 1 made of a rigid substrate is prepared.
The base substrate 1 includes slits 5 as well as second electrode
pads 1A, first electrode pads 1B and conductors 1B.sub.1 on its
back.
Next, as shown in FIG. 6 (cross section), the semiconductor pellet
2 is mounted on the pellet mounting area of the main surface of the
base substrate 1. The semiconductor pellet 2 is fixed to the pellet
mounting area of the main surface of the base substrate 1 through
an insulating layer 3.
Next, the base substrate 1 is mounted on a bonding stage (heat
block) 14 with the semiconductor pellet 2 at the bottom. The
bonding stage 14 has a recess 14A that accommodates the
semiconductor pellet 2. The base substrate 1 and the semiconductor
pellet 2 are heated to about 200.degree. C. on the bonding stage
14.
Next, as shown in FIG. 7 (cross section of an essential part), the
bonding pads 2A arranged on the main surface of the semiconductor
pellet 2 and the second electrode pads 1A arranged on the back of
the base substrate 1 are electrically connected by the bonding
wires 6. The bonding wires 6 running in the slits 5 are connected
to the bonding pads 2A of the semiconductor pellet 2 and to the
second electrode pads 1A of the base substrate 1. The connection of
the bonding wires 6 is accomplished by ultrasonic thermocompression
bonding. In this process, the base substrate 1 is made from a rigid
substrate with a high Young's modulus compared with the flexible
substrate used in conventional structure, so that the bonding force
applied to the second electrode pads 1A is prevented from being
absorbed by the rigid base substrate 1, thus allowing the bonding
force and the ultrasonic vibrations to be transferred effectively
to the second electrode pads 1A. Further, because the base
substrate 1 is made of a rigid substrate that has a smaller thermal
expansion coefficient in the planar direction than that of a
flexible substrate and a higher Young's modulus--which means it is
harder to bend--it is possible to reduce positional deviations of
the second electrode pads 1A and of the bonding pads 2A of the
semiconductor pellet 2 due to thermal expansion of the base
substrate 1.
Then, as shown in FIG. 8 (cross section of an essential part), the
base substrate 1 and the semiconductor pellet 2 are put in the
cavity 11 defined by the upper die 10A and the lower die 10B of the
molding die 10, with the base substrate 1 fit in the recess 11B of
the cavity 11. A part of the bonding wires 6 and the second
electrode pads 1A of the base substrate 1 are placed in the
recesses 12 formed in the recess 11B. The molding die 10 is
preheated to around 170.degree.-180.degree. C. to heighten the
fluidity of the resin 7A supplied into the cavity 11. Because the
base substrate 1 is made from a rigid substrate with a smaller
thermal expansion coefficient in the planar direction than the
flexible substrate and with a higher Young's modulus, which means
the base substrate 1 is harder to bend, the base substrate 1 can be
prevented from being deformed (warped or twisted) due to the
heating of the molding die 10 to about 170.degree.-180.degree. C.
during this process.
Next, resin tablets are charged into the pot of the molding die 10,
nothing that they are preheated by a heater to lower the viscosity
before being charged. The resin tablets in the pot are heated by
the molding die 10, further lowering the viscosity.
The resin is then pressurized by a plunger of the transfer molding
device, forcing the resin 7A from the pot through the runner and
the gate 13 into the recess 11A and the recesses 12 of the cavity
11 to cover the peripheral area of the main surface of the base
substrate 1, leaving the back of the semiconductor pellet 2
exposed. In this way, a resin sealing body 7 that seals the bonding
wires 6 is formed. The resin 7A is forced into the recesses 12
through the slits 5 of the base substrate 1 from the recess 11A. In
this process, the resin 7A supplied from the recess 11A to the
recesses 12 through the slits 5 flows in the axial direction of the
bonding wires 6, i.e., in the vertical direction, from one end side
of the bonding wires 6. This vertical flow of resin prevents the
bonding wires 6 from being deformed whereas the horizontal flow
along the surface of the base substrate 1 may deform them.
Then, the base substrate 1 is taken out of the molding die 10, and
bump electrodes 4 are electrically and mechanically connected to
the surfaces of the first electrode pads 1B on the back of the base
substrate 1. Thus, a nearly completed semiconductor device shown in
FIG. 1, 2, 3 and 4 is obtained.
After this, the semiconductor device is shipped as a product. The
semiconductor device shipped as a product is mounted on a mounting
surface of a mounting board 15, with the bump electrodes 4 of the
semiconductor device electrically and mechanically connected to
electrode pads 15A arranged on the mounting surface of the mounting
board 15, as shown in FIG. 10 (cross section). The connection
between the bump electrodes 4 of the semiconductor device and the
electrode pads 15A of the mounting board 15, although it depends on
the material of the bump electrodes 4, may be accomplished in an
atmosphere at a reflow temperature of, for instance, around
210.degree.-230.degree. C. In this mounting process, because the
base substrate 1 is made from a rigid substrate which has a smaller
thermal expansion coefficient in the planar direction and a higher
Young's modulus--which means it is more difficult to bend--than a
flexible substrate, the base substrate 1 can be prevented from
being deformed due to reflow heat.
This embodiment offers the following advantages.
A semiconductor device comprises a semiconductor pellet 2 mounted
on a pellet mounting area of the main surface of a base substrate
1, in which first electrode pads 1B arranged on the back of the
base substrate 1 are electrically connected to bonding pads 2A
arranged on the main surface of the semiconductor pellet 2. The
base substrate 1 is formed of a rigid substrate, and its first
electrode pads 1B are electrically connected to the second
electrode pads 1A arranged on its reverse side. The semiconductor
pellet 2 is mounted on the pellet mounting area of the main surface
of the base substrate 1, with its main surface downward, and its
bonding pads 2A are electrically connected with the second
electrode pads 1A of the base substrate 1 through bonding wires 6
passing through slits 5 formed in the base substrate 1. Because
with this construction the bonding pads 2A of the semiconductor
pellet 2 and the first electrode pads 1B of the base substrate 1
can be electrically connected through the bonding wires 6 and
second electrode pads 1A, it is possible to eliminate the through
holes used to electrically connect the second electrode pads 1A and
the first electrode pads 1B. This in turn allows the base substrate
1 to be reduced in size by an amount corresponding to the occupied
area of the through holes (land area), which contributes to size
reduction of the semiconductor device.
Because the first electrode pads 1B can be put closer to the second
electrode pads 1A by a distance corresponding to the occupied area
of the through holes, it is possible to shorten the length of the
conductors 1B, of the base substrate 1 that electrically connect
the second electrode pads 1A and the first electrode pads 1B. This
reduces the inductance, increasing the operation speed of the
semiconductor device.
Further, because the rigid substrate has a higher Young's modulus
and is harder than the flexible substrate of the conventional
structure, the bonding force applied to the second electrode pads
1A is not absorbed by the base substrate 1 when electrically
connecting the bonding pads 2A on the main surface of the
semiconductor pellet 2 and the second electrode pads 1A on the back
of the base substrate 1 by the bonding wires 6. As a result, the
bonding force and the ultrasonic vibrations are effectively
transferred to the second electrode pads 1A. This in turn increases
the connection strength between the bonding wires 6 and the second
electrode pads 1A, preventing possible connection failures of the
bonding wires 6, enhancing the electric reliability of the
semiconductor device.
Moreover, because the rigid substrate has a smaller thermal
expansion coefficient in the planar direction and a higher Young's
modulus than a flexible substrate, which means it is more resistant
to bending, the base substrate 1 is free from deformations (warping
and twisting) due to reflow heat when the semiconductor device is
mounted on the mounting surface of the mounting board 15. As a
result, a sufficient degree of flatness of the back of the base
substrate 1 with respect to the mounting surface of the mounting
board 15 can be secured, enhancing the mounting precision of the
semiconductor device.
Further, because the rigid substrate has a smaller thermal
expansion coefficient in the planar direction and a higher Young's
modulus than the flexible substrate, which means it is more
resistant to bending, the warping of the base substrate 1 can be
limited to less than 100 .mu.m even when the external size of the
base substrate 1 increases with the increasing number of the first
electrode pads 1B.
With the warping of the base substrate 1 limited to within 100
.mu.m, it is possible to eliminate a reinforcement substrate
intended to prevent warping of the base substrate 1. This reduces
the manufacture cost of the semiconductor device compared with that
of a semiconductor device having a reinforcement substrate.
Furthermore, because the base substrate 1 can be formed of a
printed wiring board of a single layer structure having the second
electrode pads 1A, first electrode pads 1B and conductors 1B.sub.1
arranged only on the back of a rigid substrate, the parts cost of
the base substrate 1 can be reduced compared with that of a base
substrate formed of a two-layer printed wiring board which has
circuits formed on both the main and back surfaces of the rigid
substrate. This means that the overall cost of semiconductor device
manufacture can be lowered.
Another feature of this embodiment is that the slits 5 formed in
the base substrate 1 extend in the directions of rows of bonding
pads 2A arranged on the main surface of the semiconductor pellet 2
and are located at positions over the bonding pads 2A. With this
construction, the slits 5 are arranged within the area occupied by
the semiconductor pellet 2, so that the base substrate 1 requires
no increase in size corresponding to the slits 5.
A further feature of this embodiment is that the second electrode
pads 1A are arranged in two opposite areas of the back of the base
substrate 1 divided by the slits 5. This construction allows an
increase in the number of power supply paths for electrically
connecting the bonding pads 2A of the semiconductor pellet 2 and
the second electrode pads 1A of the base substrate 1. This in turn
makes it possible to reduce power supply noise generated at time of
simultaneous switching of signals, thereby preventing malfunctions
of the semiconductor device.
Further, even when the pitch of the second electrode pads 1A of the
base substrate 1 is set larger than that of the bonding pads 2A of
the semiconductor pellet 2, the length of the row of the second
electrode pads 1A for each side of the semiconductor pellet 2 can
be made almost equal to the length of the row of the bonding pads
2A for each side of the semiconductor pellet 2. This prevents an
increase in the length of the bonding wires 6, which is dependent
on the length of the row of the second electrode pads 1A. As a
result, it is possible to prevent the bonding wires 6 from being
deformed by the flow of resin when the bonding wire 6 are sealed by
the resin sealing body 7 according to the transfer molding.
Further, because the second electrode pads 1A can be located at
positions on the base substrate 1 facing the bonding pads 2A of the
semiconductor pellet 2, the lengths of the bonding wires 6 can be
made uniform, which in turn makes uniform the inductances of the
signal paths between the bonding pads 2A of the semiconductor
pellet 2 and the second electrode pads 1A of the base substrate
1.
A further feature of this embodiment is the structure in which the
back of the semiconductor pellet 2 opposing its main surface is
exposed from the resin sealing body 7 that covers the peripheral
area around the main surface of the base substrate 1. This
structure allows the heat generated by the operation of the circuit
system mounted on the semiconductor pellet 2 to be released from
the back of the semiconductor pellet 2, thus enhancing the heat
dissipation efficiency of the semiconductor device.
Further, because the mechanical strength of the base substrate 1
can be reinforced by the mechanical strength of the resin sealing
body 7, deformations of the base substrate 1 (warping and twisting)
due to reflow heat during mounting can be prevented.
A further feature of this embodiment is that the bonding wires 6
are sealed with the resin sealing body 7. This structure prevents
the bonding wires 6 from being deformed due to external impacts and
contacts, thus enhancing the electric reliability of the
semiconductor device.
A still further feature of this embodiment is that the resin
sealing body 7 is formed both on the main surface side and the back
surface side of the base substrate 1. This structure prevents the
resin sealing body 7 from becoming separated from the base
substrate 1 due to the thermal stresses generated during a
temperature cycle test or when the bump electrodes 4 are connected.
This in turn enhances the reliability of the semiconductor
device.
A method of manufacturing a semiconductor device, in which a
semiconductor pellet 2 is mounted on a pellet mounting area of the
main surface of a base substrate 1 and in which first electrode
pads 1B arranged on the back of the base substrate 1 are
electrically connected to bonding pads 2A arranged on the main
surface of the semiconductor pellet 2, comprises a step of mounting
the semiconductor pellet 2, with its main surface downward, on the
pellet mounting area of the main surface of the base substrate 1
formed of a rigid substrate, and a step of electrically connecting
the bonding pads 2A to the second electrode pads 1A, which are
electrically connected to the first electrode pads 1B of the base
substrate 1 and arranged on the back of the base substrate 1,
through bonding wires 6 passing through slits 5 formed in the base
substrate 1. The bonding pads 2A of the semiconductor pellet 2 and
the first electrode pads 1B of the base substrate 1 therefore are
electrically connected through the bonding wires 6 and the second
electrode pads 1A, so that through holes 1C used for electrically
connecting the second electrode pads 1A and the first electrode
pads 1B can be eliminated, reducing the external size of the base
substrate 1 by an amount corresponding to the occupied area of the
through holes. As a result, the overall external size of the
semiconductor device can be reduced.
Further, because the bonding pads 2A of the semiconductor pellet 2
and the first electrode pads 1B of the base substrate 1 are
electrically connected through the bonding wires 6 and the second
electrode pads 1A, there is no need for through holes 1C to
electrically connect the second electrode pads 1A with the first
electrode pads 1B. This makes it possible to use a base substrate 1
in which the conductors 1B.sub.1 electrically connecting the second
electrode pads 1A and the first electrode pads 1B are shorter by a
length corresponding to the occupied area of the through holes. As
a result, it is possible to fabricate a semiconductor device with
fast operating speeds.
Because the base substrate 1 used is formed of a rigid substrate
having a higher Young's modulus--which means it is harder--than a
flexible substrate, the bonding force applied to the bonding pads
2A when electrically connecting the bonding pads 2A arranged on the
main surface of the semiconductor pellet 2 and the second electrode
pads 1A arranged on the back of the base substrate 1 through the
bonding wires 6 is not absorbed by the base substrate 1,
effectively transmitting the bonding force and ultrasonic
vibrations to the second electrode pads 1A. As a result, the
connection strength between the bonding wires 6 and the second
electrode pads 1A can be increased, which in turn allows the
manufacture of a semiconductor device with high electric
reliability.
Because the base substrate 1 is formed of a rigid substrate having
a smaller thermal expansion coefficient in the planar direction and
a higher Young's modulus--which means it is more resistant to
bending--than a flexible substrate, the base substrate 1 is
prevented from being deformed (warped or twisted) due to reflow
heat during the process of mounting the semiconductor device on the
mounting surface of the mounting board 15. This allows the back
surface of the base substrate 1 to have a sufficient degree of
flatness with respect to the mounting surface of the mounting board
15, thus enhancing the mounting precision of the semiconductor
device.
Following the process of electrically connecting with the bonding
wires 6, the method of manufacture includes a process of transfer
molding of a resin sealing body 7 that covers the peripheral area
of the main surface of the base substrate 1 and seals the bonding
wires 6. Because the base substrate 1 uses a rigid substrate which
has a smaller thermal expansion coefficient in the planar direction
and a higher Young's modulus and is more resistant to bending than
a flexible substrate, this method prevents the base substrate 1
from being deformed (warped or twisted) due to heating of the
molding die 10.
Because the resin 7A supplied from the recess 11A into the recesses
12 through the slits 5 flows from one end side of the bonding wires
6 in their axial direction, i.e., in the vertical direction, the
bonding wires 6 are not deformed by the flow of the resin 7A,
whereas they can be deformed when the resin flows along the surface
of the base substrate 1, i.e., in the lateral direction.
As shown in FIG. 11 (cross section), the resin sealing body 7 may
be formed on the back surface of the base substrate 1 excluding the
surfaces of the second electrode pads 1A and first electrode pads
1B. In this case, the base substrate 1 is held and clamped from
both sides by the resin sealing body 7 and therefore prevented from
being warped.
The base substrate 1 may, though not shown, be formed in a
multilayer structure in which a plurality of rigid substrates are
stacked together. This structure can reduce the manufacture cost as
compared with a base substrate made up of a plurality of flexible
substrates stacked together.
Embodiment 2
The outline configuration of a semiconductor device as the second
embodiment of this invention that employs a BGA structure is shown
in FIG. 12 (cross section) and FIG. 13 (enlarged plan view of an
essential part of the back side showing the state of the back side
removed of the resin sealing body).
As shown in FIG. 12 and 13, the semiconductor device has the
semiconductor pellet 2 mounted facedown on the pellet mounting area
of the main surface of the base substrate 1 with an insulating
layer 3 in between. A plurality of bump electrodes 4 are arranged
in grid on the back of the base substrate 1.
Arranged in the central area of the main surface of the
semiconductor pellet 2 along the longer sides thereof is a row of
bonding pads 2A, which are electrically connected to the second
electrode pads 1A arranged on the back of the base substrate 1
through the bonding wires 6 passing through the slits 5 formed in
the base substrate 1. The second electrode pads 1A are electrically
connected to the corresponding first electrode pads 1B arranged on
the back of the base substrate 1 through conductors 1B.sub.1. Bump
electrodes 4 are electrically and mechanically connected to the
surfaces of the first electrode pads 1B. That is, the bonding pads
2A of the semiconductor pellet 2 are electrically connected to the
first electrode pads 1B through the bonding wires 6, second
electrode pads 1A and conductors 1B.sub.1.
The slits 5 of the base substrate 1 are formed in the central area
of the main surface of the semiconductor pellet 2 along the
direction of the row of the bonding pads 2A arranged along the
longer side of the semiconductor pellet 2. The slits 5 are tapered
so that its opening on the back side of the base substrate 1 is
greater than the opening on the main surface side.
As described above, this embodiment offers similar effects and
advantages to those of the first embodiment. With the slits 5
tapered, it is possible to prevent contact between the base
substrate 1 and a bonding tool when one end of the bonding wires 6
is bonded to the bonding pads 2A of the semiconductor pellet 2.
This in turn raises the yield of semiconductor device assembly in
the bonding process.
Embodiment 3
The outline configuration of a semiconductor device as the third
embodiment of this invention that employs a BGA structure is shown
in FIG. 14 (plan view of an essential part of the back side showing
the state of the back side removed of the resin sealing body).
As shown in FIG. 14, the semiconductor device has a semiconductor
pellet 2 mounted facedown on a pellet mounting area of the main
surface of the base substrate 1, with an insulating layer 3 in
between. Bump electrodes 4 are arranged in grid on the back of the
base substrate 1.
At the outer periphery of the main surface of the semiconductor
pellet 2, a plurality of bonding pads 2A are arranged along the
sides of the pellet. At the central portion of the main surface of
the semiconductor pellet 2, a plurality of bonding pads 2A are
arranged along the longer or shorter side of the pellet. The
bonding pads 2A are electrically connected to the second electrode
pads 1A arranged on the back of the base substrate 1 by bonding
wires 6 passing through slits 5 formed in the base substrate 1. The
second electrode pads 1A are electrically connected to first
electrode pads 1B arranged on the back of the base substrate 1
through conductors 1B.sub.1. Bump electrodes 4 are electrically and
mechanically connected to the surfaces of the individual first
electrode pads 1B. That is, the bonding pads 2A are electrically
connected to the first electrode pads 1B through the bonding wires
6, second electrode pads 1A and conductors 1B.sub.1.
The slits 5 are arranged at each sides of the semiconductor pellet
2 and also at the central portion of the pellet. That is, the base
substrate 1 of this embodiment has five slits 5, each of which is
located above the bonding pads 2A of the semiconductor pellet
2.
As explained above, this embodiment offers the similar effects and
advantages to those of the first embodiment. Because the slits 5
are arranged at the sides and the central portion of the
semiconductor pellet 2, it is possible to increase the number of
bonding pads 2A arranged on the main surface of the semiconductor
pellet 2 and the number of second electrode pads 1A arranged on the
back of the base substrate 1. This allows an increase in the number
of power supply paths for electrically connecting the bonding pads
2A of the semiconductor pellet 2 and the second electrode pads 1A
of the base substrate 1. This is turn allows a further reduction in
power supply noise generated when output signals are switched
simultaneously. Furthermore, this construction makes it possible to
increase the number of signal paths electrically connecting the
bonding pads 2A of the semiconductor pellet 2 and the second
electrode pads 1A of the base substrate 1 and therefore reduce the
external size of the semiconductor pellet 2 dictated by the number
of bonding pads 2A.
Although this embodiment has been shown to have only one slit 5
formed at the central portion of the semiconductor pellet 2, two or
more slits 5 may be arranged parallelly or crosswise to each other
at the central part of the semiconductor pellet 2. By increasing
the number of slits 5 in this way, it is possible to further
increase the number of the second electrode pads 1A of the base
substrate 1 and the number of the bonding pads 2A of the
semiconductor pellet 2.
Embodiment 4
The outline configuration of a semiconductor device as the fourth
embodiment of this invention that employs a BGA structure is shown
in FIG. 15 (plan view of an essential part of the back side showing
the state of the back side removed of the resin sealing body).
As shown in FIG. 15, the semiconductor device has a semiconductor
pellet 2 mounted facedown on a pellet mounting area of the main
surface of the base substrate 1, with an insulating layer 3 in
between. Bump electrodes 4 are arranged in grid on the back of the
base substrate 1. The base substrate 1 is formed of a printed
circuit board of, for example, 3-layer wiring structure.
At the outer periphery of the main surface of the semiconductor
pellet 2, a plurality of bonding pads 2A are arranged along the
sides of the pellet. The bonding pads 2A are electrically connected
to the second electrode pads 1A arranged on the back of the base
substrate 1 through bonding wires 6 passing through slits 5 formed
in the base substrate 1.
Of the second electrode pads 1A, electrode pads 1A.sub.2 are formed
integral with electrode plates 8A. The electrode plates 8A are
electrically connected to other electrode plates 8A via through
holes (not shown) and internal wiring (not shown) in the base
substrate 1. The electrode plates 8A is connected to be at a
reference voltage (0 V for example). Of the second electrode pads
1A, electrode pads 1A.sub.3 are formed integral with an electrode
plate 8B. This electrode plate 8A is connected to be at an
operating voltage (3.3 V for instance).
With this embodiment, because the through holes 1C that
electrically connect the second electrode pads 1A on the main
surface of the base substrate 1 and the first electrode pads 1B on
the back are eliminated, the electrode plates 8A and the electrode
plate 8B can be arranged on the back of the base substrate 1. This
allows the bump electrodes 4 to be freely located and shortens the
distance between the bonding pads 2A of the semiconductor pellet 2
and the pump electrodes 4. As a result, the inductance can be
reduced, thereby increasing the operating speeds of the
semiconductor device.
The invention has been described in detail in connection with
representative embodiments of the invention. It is noted, however,
that the invention is not limited to these embodiments but that
many modifications may be made without departing from the spirit of
the invention.
Representative advantages of this invention may be summarized as
follows.
It is possible to reduce the size of a semiconductor device in
which the semiconductor pellet is mounted on the pellet mounting
area of the main surface of the base substrate and in which the
first electrode pads arranged on the back of the base substrate are
electrically connected to the bonding pads arranged on the main
surface of the semiconductor pellet.
It is possible to increase the operating speed of the semiconductor
device.
It is also possible to enhance the electric reliability of the
semiconductor device.
Further, it is possible to increase the mounting precision of the
semiconductor device.
* * * * *