U.S. patent application number 11/887331 was filed with the patent office on 2009-05-07 for flip chip mounting method and method for connecting substrates.
Invention is credited to Seiji Karashima, Takashi Kitae, Siichi Nakatani.
Application Number | 20090115071 11/887331 |
Document ID | / |
Family ID | 37053210 |
Filed Date | 2009-05-07 |
United States Patent
Application |
20090115071 |
Kind Code |
A1 |
Karashima; Seiji ; et
al. |
May 7, 2009 |
FLIP CHIP MOUNTING METHOD AND METHOD FOR CONNECTING SUBSTRATES
Abstract
A flip chip mounting method which is applicable to the flip chip
mounting of a next-generation LSI and high in productivity and
reliability as well as a method for connecting substrates are
provided. A circuit board 10 having a plurality of connecting
terminals 11 and a semiconductor chip 20 having a plurality of
electrode terminals 21 are disposed in mutually facing relation and
a resin 13 containing conductive particles 12 and a gas bubble
generating agent is supplied into the space therebetween. In this
state, the resin 13 is heated to generate gas bubbles 30 from the
gas bubble generating agent contained in the resin 13. The resin 13
is pushed toward the outside of the generated gas bubbles 30 by the
growth thereof. The resin 13 pushed to the outside is
self-assembled in the form of columns between the respective
terminals of the circuit board 10 and the semiconductor chip 20. In
this state, by pressing the semiconductor chip 20 against the
circuit board 10, the conductive particles 12 contained in the
resin 13 self-assembled between the facing terminals are brought
into contact with each other to provide electrical connection
between the terminals.
Inventors: |
Karashima; Seiji; (Osaka,
JP) ; Kitae; Takashi; (Osaka, JP) ; Nakatani;
Siichi; (Osaka, JP) |
Correspondence
Address: |
MCDERMOTT WILL & EMERY LLP
600 13TH STREET, NW
WASHINGTON
DC
20005-3096
US
|
Family ID: |
37053210 |
Appl. No.: |
11/887331 |
Filed: |
March 16, 2006 |
PCT Filed: |
March 16, 2006 |
PCT NO: |
PCT/JP2006/305274 |
371 Date: |
September 28, 2007 |
Current U.S.
Class: |
257/778 ;
257/E21.002; 257/E23.06; 438/108 |
Current CPC
Class: |
H05K 2201/10674
20130101; H01L 2924/01078 20130101; H01L 2224/1329 20130101; H01L
2924/01019 20130101; H01L 2924/01033 20130101; H01L 2924/30105
20130101; H01L 2924/01009 20130101; H01L 2924/01029 20130101; H01L
2224/29111 20130101; H01L 2224/83886 20130101; H01L 2924/0132
20130101; H01L 2924/0665 20130101; H01L 2924/381 20130101; Y10T
156/1744 20150115; H01L 2224/16227 20130101; H01L 2224/75 20130101;
H01L 24/73 20130101; H01L 2225/06513 20130101; H01L 2924/014
20130101; H01L 2224/83097 20130101; H01L 2224/83862 20130101; H01L
2224/83047 20130101; H01L 2224/8388 20130101; H01L 2924/01047
20130101; H01L 2924/01005 20130101; H01L 2224/16148 20130101; H01L
24/29 20130101; H01L 2924/01002 20130101; H01L 2924/01082 20130101;
H01L 25/0657 20130101; H01L 2224/13339 20130101; H01L 2224/2919
20130101; H01L 2924/1579 20130101; H01L 2224/293 20130101; H01L
2224/29101 20130101; H01L 2924/01027 20130101; H01L 24/83 20130101;
H01L 2224/16225 20130101; H01L 2924/01004 20130101; H01L 2924/14
20130101; H01L 2924/01006 20130101; H01L 25/50 20130101; H01L
2224/29291 20130101; H01L 2224/29347 20130101; H01L 24/16 20130101;
H01L 2224/29339 20130101; H01L 2924/01013 20130101; H01L 2924/01015
20130101; H01L 2224/13347 20130101; H05K 2203/087 20130101; H01L
24/27 20130101; H01L 2224/83091 20130101; H01L 2224/83192 20130101;
H01L 2224/165 20130101; H05K 3/323 20130101; H01L 21/563 20130101;
H01L 2224/83204 20130101; H01L 2924/0105 20130101; H01L 2224/2929
20130101; H01L 2224/1319 20130101; H01L 2224/73204 20130101; H01L
2224/83887 20130101; H01L 2924/01067 20130101; H01L 2224/13099
20130101; H01L 2924/01002 20130101; H01L 2924/00011 20130101; H01L
2924/01004 20130101; H01L 2924/00011 20130101; H01L 2924/01005
20130101; H01L 2924/00011 20130101; H01L 2924/01009 20130101; H01L
2924/00011 20130101; H01L 2924/01015 20130101; H01L 2924/00011
20130101; H01L 2924/01027 20130101; H01L 2924/00011 20130101; H01L
2224/29339 20130101; H01L 2924/01029 20130101; H01L 2224/165
20130101; H01L 2924/01029 20130101; H01L 2224/165 20130101; H01L
2924/01047 20130101; H01L 2224/165 20130101; H01L 2924/01047
20130101; H01L 2924/01029 20130101; H01L 2924/01078 20130101; H01L
2924/00011 20130101; H01L 2224/2929 20130101; H01L 2924/0665
20130101; H01L 2224/2929 20130101; H01L 2924/066 20130101; H01L
2224/83886 20130101; H01L 2924/00015 20130101; H01L 2924/0665
20130101; H01L 2924/00 20130101; H01L 2224/29101 20130101; H01L
2924/014 20130101; H01L 2924/00 20130101; H01L 2924/0132 20130101;
H01L 2924/01029 20130101; H01L 2924/01047 20130101; H01L 2924/0132
20130101; H01L 2924/0105 20130101; H01L 2924/01082 20130101; H01L
2224/1329 20130101; H01L 2924/0665 20130101; H01L 2224/13347
20130101; H01L 2924/00014 20130101; H01L 2224/13339 20130101; H01L
2924/00014 20130101; H01L 2224/2919 20130101; H01L 2924/0665
20130101; H01L 2924/00014 20130101; H01L 2224/13339 20130101; H01L
2924/01029 20130101; H01L 2924/00014 20130101 |
Class at
Publication: |
257/778 ;
438/108; 257/E21.002; 257/E23.06 |
International
Class: |
H01L 21/02 20060101
H01L021/02; H01L 23/498 20060101 H01L023/498 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 29, 2005 |
JP |
2005-094233 |
Claims
1. A flip chip mounting method for disposing a semiconductor chip
having a plurality of electrode terminals in facing relation to a
circuit board having a plurality of connecting terminals and
electrically connecting the connecting terminals of the circuit
board to the electrode terminals of the semiconductor chip, the
flip chip mounting method comprising: a first step of supplying a
resin containing conductive particles and a gas bubble generating
agent into a space between the circuit board and the semiconductor
chip; a second step of heating the resin to generate gas bubbles
from the gas bubble generating agent contained in the resin; a
third step of pressing the semiconductor chip against the circuit
board; and a fourth step of curing the resin, wherein, in the
second step, the resin is pushed toward the outside of the gas
bubbles generated from the gas bubble generating agent by growth of
the gas bubbles and self-assembled between the connecting terminals
of the circuit board and the electrode terminals of the
semiconductor chip, in the third step, the conductive particles
contained in the resin self-assembled between the terminals come in
contact with each other to provide electrical connection between
the terminals, and in the fourth step, the resin between the
terminals is cured to fix the semiconductor chip to the circuit
board.
2. The flip chip mounting method of claim 1, wherein the gas bubble
generating agent is composed of a material which boils when the
resin is heated.
3. The flip chip mounting method of claim 1, wherein the gas bubble
generating agent is composed of two or more materials having
different boiling temperatures.
4. The flip chip mounting method of claim 1, wherein the gas bubble
generating agent is composed of a material which is thermally
decomposed to generate a gas when the resin is heated.
5. The flip chip mounting method of claim 4, wherein the gas bubble
generating agent is composed of a compound containing water of
crystallization and decomposed to generate water vapor when the
resin is heated.
6. The flip chip mounting method of claim 1, wherein the second
step is performed while the space between the circuit board and the
semiconductor chip is varied.
7. The flip chip mounting method of claim 1, wherein the first step
is performed by supplying the resin containing the conductive
particles and the gas bubble generating agent onto the circuit
board and then disposing the semiconductor chip on a surface of the
resin.
8. The flip-chip mounting method of claim 1, wherein the fourth
step is performed by heating the resin to thermally cure the
resin.
9. The flip chip mounting method of claim 1, further comprising,
after the fourth step, the step of: supplying an underfill material
into the space between the circuit board and the semiconductor chip
and then curing the underfill material.
10. The flip chip mounting method of claim 1, wherein the
semiconductor chip having the plurality of electrode terminals has
a structure in which a semiconductor bare chip is mounted on an
interposer having the plurality of electrode terminals.
11. A method for connecting substrates by disposing a second
substrate having a plurality of electrodes in facing relation to a
first substrate having a plurality of electrodes and providing
electrical connection between the electrodes of the first substrate
and the electrodes of the second substrate, the method comprising:
a first step of supplying a resin containing conductive particles
and a gas bubble generating agent into a space between the first
substrate and the second substrate; a second step of heating the
resin to generate gas bubbles from the gas bubble generating agent
contained in the resin; a third step of pressing the second
substrate against the first substrate; and a fourth step of curing
the resin, wherein in the second step, the resin is pushed toward
the outside of the gas bubbles generated from the gas bubble
generating agent by growth of the gas bubbles and self-assembled
between the electrodes of the first substrate and the electrodes of
the second substrate, in the third step, the conductive particles
contained in the resin self-assembled between the electrodes come
in contact with each other to provide electrical connection between
the electrodes, and in the fourth step, the resin self-assembled
between the electrodes is cured to fix the first substrate to the
second substrate.
12. The method of claim 11, wherein the gas bubble generating agent
is composed of a material which boils when the resin is heated.
13. The method of claim 11, wherein the second step is performed
while varying the space between the first substrate and the second
substrate.
14. The method of claim 11, wherein the first step is performed by
supplying the resin containing the conductive particles and the gas
bubble generating agent onto the first substrate and then disposing
the second substrate on a surface of the resin.
15. The method of claim 11, further comprising, after the fourth
step, the step of: supplying an underfill material into the space
between the first substrate and the second substrate and then
curing the underfill material.
16. A flip chip mounting body comprising a circuit board having a
plurality of connecting terminals and a semiconductor chip having a
plurality of electrode terminals and disposed in facing relation to
the circuit board such that the connecting terminals of the circuit
board are electrically connected to the electrode terminals of the
semiconductor chip, wherein the connecting terminals are
electrically connected to the electrode terminals by supplying a
resin containing conductive particles and a gas bubble generating
agent into a space between the circuit board and the semiconductor
chip, causing the resin to be self-assembled between the connecting
terminals and the electrode terminals, and bringing the conductive
particles in the self-assembled resin into contact with each
other.
17. The flip chip mounting body of claim 16, which is fixed with an
underfill material supplied into the space between the circuit
board and the semiconductor chip.
18. (canceled)
19. (canceled)
Description
RELATED APPLICATIONS
[0001] This application is the U.S. National Phase under 35 U.S.C.
.sctn. 371 of International Application No. PCT/JP 2006/305274,
filed on Mar. 16, 2006, which in turn claims the benefit of
Japanese Application No. 2005-094233, filed on Mar. 29, 2005, the
disclosures of which Applications are incorporated by reference
herein.
TECHNICAL FIELD
[0002] The present invention relates to a flip chip mounting method
for mounting a semiconductor chip on a circuit board and to a
method for connecting substrates each formed with a plurality of
electrodes.
BACKGROUND ART
[0003] In recent years, as semiconductor integrated circuits (LSIs)
used in electronic equipment have become higher in density and
degree of integration, the electrode terminals of LSI chips have
rapidly become higher in pin count and narrower in pitch. To mount
such an LSI chip on a circuit board, flip chip mounting has been
used widely for a reduction in wiring delay. In the flip chip
mounting, it is typical to form solder bumps on the electrode
terminals of an LSI chip and simultaneously bond the electrode
terminals to connecting terminals formed on a circuit board via the
solder bumps.
[0004] To mount a next-generation LSI having electrode terminals
the number of which is over 5,000, it is needed to form bumps
corresponding to a narrower pitch of not more than 100 .mu.m.
However, with a current solder-bump forming technology, it is
difficult to respond to the need. In addition, it is needed to form
a large number of bumps corresponding to the number of electrode
terminals. Therefore, to reduce cost, it is also required to
achieve high productivity by reducing a mounting tact time per
chip.
[0005] Likewise, due to an increased number of electrode terminals,
the semiconductor integrated circuit has shifted from the use of
peripheral electrode terminals to that of area array electrode
terminals. Under the higher-density and higher-integration
requirements, it is expected that the scale of a semiconductor
process advances from 90 nm to 65 nm and 45 nm. As a result, the
miniaturization of wiring further proceeds and a wire-to-wire
capacitance increases so that problems associated with a higher
speed and a power consumption loss have become serious and demand
for a low-dielectric-constant (low-k) insulating film between
wiring layers has further grown. Such a low-k insulating film can
be implemented by porosifying an insulating layer material so that
the mechanical strength thereof is low, presenting an obstacle to a
reduction in the thickness of a semiconductor. Moreover, when area
array electrode terminals are constructed as described above, there
is a problem in the strength of a low-k porous film. Consequently,
it has become difficult to form bumps on the area array electrodes
and perform flip chip mounting itself. As a result, there has been
demand for a low-load flip chip mounting method suitable for a
higher-density thin semiconductor compatible with the future
advancement of a semiconductor process.
[0006] As conventional bump forming techniques, a plating method, a
screen printing method, and the like have been developed. The
plating method is suitable for a narrow pitch, but has a problem in
productivity because of complicated process steps. The screen
printing method is excellent in productivity, but is not suitable
for a narrow pitch because of the use of a mask.
[0007] In such a situation, several techniques which selectively
form solder bumps on the electrodes of an LSI chip and a circuit
board have been developed recently. These techniques are not only
suitable for the formation of micro-bumps but also capable of
simultaneously forming the bumps so that they are also excellent in
productivity and draw attention as techniques applicable to the
mounting of a next-generation LSI on a circuit board.
[0008] For example, the technique disclosed in Patent Document 1,
Patent Document 2, or the like solidly coats a solder paste
composed of a mixture of a solder powder and a flux on a substrate
having electrodes formed on the surface thereof, melts the solder
powder by heating the substrate, and selectively forms solder bumps
on the electrodes having high wettability.
[0009] The technique disclosed in Patent Document 3 solidly coats a
paste-like composition (deposition-type solder using a chemical
reaction) containing an organic acid lead salt and metallic tin as
main components on a substrate on which electrodes are formed,
causes a substitution reaction between Pb and Sn by heating the
substrate, and selectively deposits a Pb/Sn alloy on the electrodes
of the substrate.
[0010] However, each of the techniques disclosed in Patent
Documents 1 to 3 shown above supplies a paste-like composition onto
the substrate by coating, local variations in thickness and
concentration occur. Accordingly, the amount of a deposited solder
differs from one electrode to another and bumps having uniform
heights cannot be obtained. In addition, since each of the methods
supplies the paste-like composition by coating onto the circuit
board having projections and depressions formed in the surface
thereof, a sufficient amount of the solder cannot be supplied onto
the electrodes forming projecting portions so that it is difficult
to obtain bumps of desired heights, which is necessary in flip chip
mounting.
[0011] In flip chip mounting using a conventional bump forming
technique, after a semiconductor chip is mounted on a circuit board
on which bumps are formed, the step of injecting a resin termed an
underfill into the space between the semiconductor chip and the
circuit board is further needed to fix the semiconductor chip to
the circuit board.
[0012] As a method for simultaneously performing the provision of
electrical connection between the facing electrode terminals of the
semiconductor chip and the circuit board and the fixation of the
semiconductor chip to the circuit board, a flip chip mounting
technique (see, e.g., Patent Document 4) using an anisotropic
conductive material has been developed. The technique supplies a
thermosetting resin containing conductive particles into the space
between the circuit board and the semiconductor chip and heats the
thermosetting resin, while simultaneously pressing the
semiconductor chip, thereby simultaneously implementing the
electrical connection between the respective electrode terminals of
the semiconductor chip and the circuit board and the fixation of
the semiconductor chip to the circuit board. [0013] Patent Document
1: Japanese Laid-Open Patent Publication No. 2000-94179 [0014]
Patent Document 2: Japanese Laid-Open Patent Publication No. HEI
6-125169 [0015] Patent Document 3: Japanese Laid-Open Patent
Publication No. HEI 1-157796 [0016] Patent Document 4: Japanese
Laid-Open Patent Publication No. 2000-332055 [0017] Patent Document
5: Japanese Laid-Open Patent Publication No. 2002-26070 [0018]
Patent Document 6: Japanese Laid-Open Patent Publication No. HEI
11-186334 [0019] Patent Document 7: Japanese Laid-Open Patent
Publication No. 2004-260131 [0020] Non-Patent Document 1: Masahito
Yasuda et al., "Self-Organized Joining Assembly Process by
Electrically Conductive Adhesive Using Low Melting Point Filler"
10th Symposium on "Microjoining and Assembly Technology in
Electronics, pp. 183 to 188, 2004)
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0021] It can be said that flip chip mounting using an anisotropic
conductive material is excellent in productivity in terms of
simultaneously implementing electrical connection between the
respective electrode terminals of a semiconductor chip and a
circuit board and fixation of the semiconductor chip to the circuit
board. However, as shown below, there are problems to be
solved.
[0022] The anisotropic conductive material mentioned above has the
conductive particles uniformly dispersed in the resin. By pressing
the semiconductor chip against the circuit board, the dispersed
conductive particles are brought into physical contact with the
respective electrode terminals of the semiconductor chip and the
circuit board, thereby allowing electrical connection between the
facing electrode terminals. On the other hand, the resin of the
anisotropic conductive material ensures insulation properties
between the adjacent electrode terminals.
[0023] However, because the conductive particles are uniformly
dispersed in the resin, the conductive particles contributing to
conduction between the facing electrode terminals are only among
all the conductive particles. As a result, it is difficult to
obtain a stable conductive state, resulting in a problem that
sufficient reliability cannot be provided for electrical
connection. Moreover, even though the adjacent electrode terminals
are insulated from each other, there is a possibility that
sufficient insulation properties cannot be ensured, since the
conductive particles not contributing to the conduction between the
facing electrode terminals are dispersed in the resin.
[0024] Thus, to apply the flip chip mounting using the anisotropic
conductive material to a next-generation LSI chip having connecting
terminals the number of which is over 5,000, problems associated
with reliability remain to be solved.
[0025] The present invention has been achieved in view of the
foregoing and an object of the present invention is to provide a
flip chip mounting method which is applicable to the flip chip
mounting of a next-generation LSI and high in productivity and
reliability as well as a method for connecting substrates having
the same basic process steps as the flip chip mounting method.
Means for Solving the Problems
[0026] A flip chip mounting method of the present invention is a
flip chip mounting method for disposing a semiconductor chip having
a plurality of electrode terminals in facing relation to a circuit
board having a plurality of connecting terminals and electrically
connecting the connecting terminals of the circuit board to the
electrode terminals of the semiconductor chip, the flip chip
mounting method comprising: a first step of supplying a resin
containing conductive particles and a gas bubble generating agent
into a space between the circuit board and the semiconductor chip;
a second step of heating the resin to generate gas bubbles from the
gas bubble generating agent contained in the resin; a third step of
pressing the semiconductor chip against the circuit board; and a
fourth step of curing the resin, wherein, in the second step, the
resin is pushed toward the outside of the gas bubbles generated
from the gas bubble generating agent by growth of the gas bubbles
and self-assembled between the connecting terminals of the circuit
board and the electrode terminals of the semiconductor chip, in the
third step, the conductive particles contained in the resin
self-assembled between the terminals come in contact with each
other to provide electrical connection between the terminals, and
in the fourth step, the resin between the terminals is cured to fix
the semiconductor chip to the circuit board.
[0027] Preferably, the gas bubble generating agent is composed of a
material which boils when the resin is heated. The gas bubble
generating agent may be composed of two or more materials having
different boiling temperatures. The gas bubble generating agent may
also be composed of a material which is thermally decomposed to
generate a gas when the resin is heated. For example, the gas
bubble generating agent is composed of a compound containing water
of crystallization and decomposed to generate water vapor when the
resin is heated.
[0028] In a preferred embodiment, the second step is performed
while the space between the circuit board and the semiconductor
chip is varied.
[0029] In a preferred embodiment, the first step is performed by
supplying the resin containing the conductive particles and the gas
bubble generating agent onto the circuit board and then disposing
the semiconductor chip on a surface of the resin.
[0030] In a preferred embodiment, the fourth step is performed by
heating the resin to thermally cure the resin. The flip chip
mounting method may also further comprise, after the fourth step,
the step of: supplying an underfill material into the space between
the circuit board and the semiconductor chip and then curing the
underfill material.
[0031] In a preferred embodiment, the semiconductor chip having the
plurality of electrode terminals has a structure in which a
semiconductor bare chip is mounted on an interposer having the
plurality of electrode terminals.
[0032] A method for connecting substrates of the present invention
is a method for connecting substrates by disposing a second
substrate having a plurality of electrodes in facing relation to a
first substrate having a plurality of electrodes and providing
electrical connection between the electrodes of the first substrate
and the electrodes of the second substrate, the method comprising:
a first step of supplying a resin containing conductive particles
and a gas bubble generating agent into a space between the first
substrate and the second substrate; a second step of heating the
resin to generate gas bubbles from the gas bubble generating agent
contained in the resin; a third step of pressing the second
substrate against the first substrate; and a fourth step of curing
the resin, wherein in the second step, the resin is pushed toward
the outside of the gas bubbles generated from the gas bubble
generating agent by growth of the gas bubbles and self-assembled
between the electrodes of the first substrate and the electrodes of
the second substrate, in the third step, the conductive particles
contained in the resin self-assembled between the electrodes come
in contact with each other to provide electrical connection between
the electrodes, and in the fourth step, the resin self-assembled
between the electrodes is cured to fix the first substrate to the
second substrate.
[0033] Preferably, the gas bubble generating agent is composed of a
material which boils when the resin is heated.
[0034] In a preferred embodiment, the second step is performed
while varying the space between the first substrate and the second
substrate.
[0035] In a preferred embodiment, the first step is performed by
supplying the resin containing the conductive particles and the gas
bubble generating agent onto the first substrate and then disposing
the second substrate on a surface of the resin.
[0036] In a preferred embodiment, the flip chip mounting method
further comprises, after the fourth step, the step of: supplying an
underfill material into the space between the first substrate and
the second substrate and then curing the underfill material.
[0037] A flip chip mounting method of the present invention is a
flip chip mounting body comprising a circuit board having a
plurality of connecting terminals and a semiconductor chip having a
plurality of electrode terminals and disposed in facing relation to
the circuit board such that the connecting terminals of the circuit
board are electrically connected to the electrode terminals of the
semiconductor chip, wherein the connecting terminals are
electrically connected to the electrode terminals by supplying a
resin containing conductive particles and a gas bubble generating
agent into a space between the circuit board and the semiconductor
chip, causing the resin to be self-assembled between the connecting
terminals and the electrode terminals, and bringing the conductive
particles in the self-assembled resin into contact with each
other.
[0038] In a preferred embodiment, the flip chip mounting body is
fixed with an underfill material supplied into the space between
the circuit board and the semiconductor chip.
[0039] A flip chip mounting apparatus of the present invention is a
flip chip mounting apparatus for flip chip mounting a semiconductor
chip on a circuit board, the flip chip mounting apparatus
comprising: holding means for holding the semiconductor chip and
the circuit board in mutually facing relation with a given space
provided therebetween; supplying means for supplying a resin
containing conductive particles and a gas bubble generating agent
into the space between the semiconductor chip and the circuit
board; heating means for heating the resin, and pressing means for
pressing the semiconductor chip against the circuit board, wherein
the heating means has first heating means for controlling a
temperature to a value at which gas bubbles are from the gas bubble
generating agent contained in the resin and second heating means
for controlling the temperature to a value at which the resin is
thermally cured.
[0040] In a preferred embodiment, the resin heated with the first
heating means is pushed toward the outside of the gas bubbles
generated from the gas bubble generating agent by growth of the gas
bubbles and self-assembled between connecting terminals of the
circuit board and electrode terminals of the semiconductor chip,
the semiconductor chip is pressed against the circuit board with
the pressing means to bring the conductive particles contained in
the resin self-assembled between the terminals into contact with
each other and provide electrical connection between the terminals,
and the resin is heated with the second heating means to fix the
semiconductor chip to the circuit board in a state in which the
conductive particles contained in the resin are in contact with
each other.
Effect of the Invention
[0041] In the flip chip mounting method according to the present
invention, by heating the resin containing the conductive particles
and the gas bubble generating agent which is supplied into the
space between the circuit board and the semiconductor chip, the gas
bubbles are generated from the gas bubble generating agent and the
resin is pushed toward the outside of the gas bubbles by the growth
thereof and allowed to be self-assembled between the connecting
terminals of the circuit board and the electrode terminals of the
semiconductor chip. Then, by pressing the semiconductor chip
against the circuit board, the conductive particles contained in
the resin self-assembled between the facing terminals are brought
into contact with each other to allow electrical connection between
the terminals. This allows the conductive particles dispersed in
the resin to be efficiently self-assembled between the terminals
and contribute to conduction between the terminals. As a result, a
stable conductive state is obtained and electrical connection with
high reliability can be achieved.
[0042] Likewise, in the method for connecting substrates according
to the present invention also, by heating the resin containing the
conductive particles and the gas bubble generating agent which is
supplied into the space between the facing substrates, the gas
bubbles are generated from the gas bubble generating agent and the
resin is pushed toward the outside of the gas bubbles by the growth
thereof and allowed to be self-assembled between the respective
electrodes of the facing substrates. By pressing the substrates
against each other, the conductive particles contained in the resin
self-assembled between the electrodes are brought into contact with
each other to allow electrical connection between the electrodes.
This allows the conductive particles dispersed in the resin to be
efficiently self-assembled between the electrodes and contribute to
conduction between the electrodes. As a result, a stable conductive
state is obtained and substrate-to-substrate connection with high
reliability can be achieved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] FIGS. 1(a) to 1(d) are step-by-step cross-sectional views
showing a flip chip mounting method in an embodiment of the present
invention;
[0044] FIGS. 2(a) to 2(c) are step-by-step cross-sectional views
showing the flip chip mounting method in the embodiment;
[0045] FIG. 3(a) is view showing a temperature profile in heating a
resin in the present invention and FIG. 3(b) is a view showing a
pressure profile when a semiconductor chip is pressed against a
circuit board;
[0046] FIGS. 4(a) and 4(b) are views for illustrating the mechanism
of self-assembly of a resin in the present invention;
[0047] FIG. 5(a) to 5(c) are step-by-step cross-sectional views
illustrating a step of performing heating while varying a gap
between the circuit board and the semiconductor chip in the present
invention;
[0048] FIG. 6 is a view for illustrating the self-assembly of a
resin containing two or more gas bubble generating agents in the
present invention;
[0049] FIG. 7 is a view showing the materials of a gas bubble
generating agent in the present invention;
[0050] FIG. 8 is a view showing the materials of a gas bubble
generating agent powder which is thermally decomposed in the
present invention; and
[0051] FIG. 9 is a block diagram showing a structure of a flip-chip
mounting apparatus in the present invention.
DESCRIPTION OF NUMERALS
[0052] 10 Circuit Board
[0053] 11 Connecting Terminal
[0054] 12 Conductive Particle
[0055] 13 Resin
[0056] 20 Underfill Material
[0057] 21 Semiconductor Chip
[0058] 30, 30a, 30b Gas bubbles
[0059] 40 Flip Chip Mounting Apparatus
[0060] 41 Holding Means
[0061] 42 Supplying Means
[0062] 43 Heating Means
[0063] 44 First Heating Means
[0064] 45 Second Heating Means
[0065] 46 Pressing Means
BEST MODE FOR CARRYING OUT THE INVENTION
[0066] Referring to the drawings, the embodiments of the present
invention will be described herein below. For easier illustration,
components having substantially the same functions are designated
by the same reference numerals in the drawings shown below. The
present invention is not limited to the following embodiments.
[0067] FIGS. 1(a) to 1(d) and FIGS. 2(a) to 2(c) are step-by-step
cross-sectional views showing the basic steps of a flip chip
mounting method in an embodiment of the present invention.
[0068] First, as shown in FIG. 1(a), a resin (e.g., an epoxy resin
or the like) 13 containing conductive particles (e.g., Cu or the
like) 12 and a gas bubble generating agent (e.g., isopropyl alcohol
or the like) is supplied onto a circuit board 10 having a plurality
of connecting terminals 11. Then, as shown in FIG. 1(b), a
semiconductor chip 20 having a plurality of electrode terminals 21
is disposed on the surface of the resin 13 to face the circuit
board 10. At this time, the electrode terminals 21 of the
semiconductor chip 20 are aligned with respect to the connecting
terminals 11 of the circuit board 10.
[0069] The steps shown herein may also be such that the circuit
board 10 and the semiconductor chip 20 are preliminarily disposed
to face each other with a given space (e.g., 10 to 80 .mu.m)
interposed therebetween and then the resin 13 containing the
conductive particles 12 and the gas bubble generating agent is
supplied into the space.
[0070] In this state, when the resin 13 is heated to a
predetermined temperature (e.g., 100 to 150.degree. C.), gas
bubbles 30 are generated from the gas bubble generating agent
contained in the resin 13, as shown in FIG. 1(c). Then, as shown in
FIG. 1(d), the generated gas bubbles 30 gradually grow so that the
resin 13 is pushed by the grown gas bubbles 30 toward the outside
thereof.
[0071] As shown in FIG. 2(a), the resin 13 pushed to the outside is
self-assembled in the form of columns (e.g., generally cylindrical
columns) between the connecting terminals 11 of the circuit board
10 and the electrode terminals 21 of the semiconductor chip 20. At
this time, most of the resin 13 which is not self-assembled between
the terminals is pushed from the space between the circuit board 10
and the semiconductor chip 20 toward the outside under the pressure
of the grown gas bubbles 30.
[0072] Then, in this state, the semiconductor chip 20 is pressed
against the circuit board 10 in the direction indicated by the
arrows, as shown in FIG. 2(b). The magnitude of the pressure is set
to, e.g., about 20 k to 200 kPa. By the pressing, the conductive
particles 12 contained in the resin 13 self-assembled between the
facing terminals are brought into contact with each other to
provide electrical connection between the terminals. At this time,
the electrical connection between the terminals is intended to be
achieved with at least one or more conductive particles 12
interposed between the terminals. In pressing, the conductive
particles 12 contained in the resin 13 are prevented from flowing
out of the resin 13 by the action of a stress resulting from the
viscosity of the resin 13.
[0073] In this state, the resin 13 self-assembled between the
facing terminals is cured to fix the semiconductor chip 20 to the
circuit board 10, as shown in FIG. 2(c). Although the resin 13 that
has spread over the entire surfaces of the terminals is sufficient
to fix the semiconductor chip 20 to the circuit board 10, an
underfill material 14 may also be injected as necessary into the
space between the semiconductor chip 20 and the circuit board 10
and then cured to enhance the fixation of the semiconductor chip 20
to the circuit board 10. It is also possible to supply the
underfill material 14 before pressing the semiconductor chip 20
against the circuit board 10.
[0074] In accordance with the present invention, by heating the
resin 13 containing the conductive particles 12 and the gas bubble
generating agent supplied into the space between the circuit board
10 and the semiconductor chip 20, the gas bubbles are generated
from the gas bubble generating agent and, by allowing the gas
bubbles to grow and push the resin 13 toward the outside thereof,
the resin 13 can be self-assembled between the connecting terminals
11 of the circuit board 10 and the electrode terminals 21 of the
semiconductor chip 20. By pressing the semiconductor chip 20
against the circuit board 10, the conductive particles 12 contained
in the resin 13 self-assembled between the facing terminals are
brought into contact with each other to allow electrical connection
between the terminals. This allows the conductive particles 12
dispersed in the resin 13 to be efficiently self-assembled between
the terminals and contribute to conduction between the terminals.
As a result, a stable conductive state is obtained and electrical
connection with high reliability can be achieved.
[0075] The sizes of the individual components and the positional
relationships therebetween shown in FIGS. 1(a) to 1(d) and FIGS.
2(a) to 2(c) (e.g., the sizes of the conductive particles 12, the
size of the spacing between the circuit board 10 and the
semiconductor chip 20, and the like) are represented for the
convenience of easier illustration and do not show real sizes and
the like.
[0076] FIGS. 3(a) and 3(b) are graphs showing an example of a
temperature profile in the step of heating the resin 13 and an
example of a pressure profile in a pressing step in the flip chip
mounting method described above.
[0077] As shown in FIG. 3(a), the resin 13 is first heated to a
temperature T.sub.1 at which the gas bubbles 30 are generated from
the gas bubble generating agent contained in the resin 13. The
temperature T.sub.1 is held for a given time t.sub.1, during which
the generated gas bubbles 30 grow to push the resin 13 toward the
outside thereof and the resin 13 is self-assembled in the form of
columns between the facing terminals. The temperature T.sub.1 is
set herein to, e.g., 100 to 180.degree. C. and the given time
t.sub.1 is set to, e.g., about 5 to 10 seconds.
[0078] Then, in the state, the semiconductor chip 20 is pressed
under a pressure P.sub.1 against the circuit board 10 in the
direction indicated by the arrows for a given time t.sub.2, as
shown in FIG. 3(b). By the pressing, the conductive particles 12
contained in the resin 13 self-assembled between the facing
terminals are brought into contact with each other to provide
electrical connection between the terminals. At this time, the
resin 13 is maintained at a given heating temperature T.sub.1. The
pressure P.sub.1 is set herein to, e.g., 70 to 200 kPa and the
given time t.sub.2 is set to, e.g., about 0 to 5 seconds.
[0079] Finally, as shown in FIG. 3(a), the resin 13 is heated to a
temperature T.sub.3 at which the resin 13 is cured. The temperature
T.sub.3 is held for a given time t.sub.3 to cure the resin 13
remaining between the facing terminals and thereby fix the
semiconductor chip 20 to the circuit board 10. The temperature
T.sub.3 is set herein to, e.g., 150 to 250.degree. C. and the given
time t.sub.3 is set to, e.g., about 10 to 20 seconds.
[0080] In the temperature profile shown in FIG. 3(a), the heating
temperature at which the gas bubbles 30 are generated from the gas
bubble generating agent is held at the fixed temperature T.sub.1
for the period of the time t.sub.1 (or the time t.sub.1+t.sub.2).
However, it is also possible to gradually increase the temperature
during the period of the time.
[0081] Referring to FIGS. 4(a) and 4(b), the mechanism of the
self-assembly of the resin 13 between the terminals, which is a key
point to the flip chip mounting method of the present invention,
will be briefly described herein.
[0082] FIG. 4(a) is a view showing the state of the resin 13 pushed
by the grown gas bubbles (not shown) into the space between one of
the connecting terminals 11 of the circuit board 10 and the
corresponding electrode terminal 21 of the semiconductor chip 20.
The resin 13 that has come in contact with the connecting terminal
11 and the electrode terminal 21 has an interfacial tension (a
force resulting from the so-called wet-spreading of a resin)
F.sub.s at the interfaces thereof which is larger than a stress
F.sub..eta. generated from the viscosity .eta. of the resin so that
the resin 13 spreads over the entire surfaces of the connecting
terminal 11 and the electrode terminal 21 to finally form a
columnar resin having boundaries at the end portions of the
terminals 11 and 21. Accordingly, even when the positions at which
the connecting terminal 11 and the electrode terminal 21 face to
each other are slightly displaced, the resin 13 can be reliably
self-assembled between the terminals under the interfacial
tension.
[0083] As shown in FIG. 4(b), a stress F.sub.b resulting from the
growth (or movement) of the gas bubbles 30 is applied to the
columnar resin 13 formed by self-growth between the terminals.
However, the columnar resin 13 can retain the shape thereof under
the effect of a reverse stress F.sub..eta. resulting from the
viscosity .eta. of the resin 13 so that the resin 13 once
self-assembled does not disappear. In addition, a surface tension
(or a gas-liquid interfacial tension) acts on the boundary between
the resin 13 and a gas (e.g., gas bubbles 30) and the surface
tension can also act to retain the shape of the columnar resin
13.
[0084] As described above, in the flip chip mounting method of the
present invention, the growth of the gas bubbles generated from the
gas bubble generating agent operates to cause the self-assembly of
the resin between the terminals. To further enhance the operation
and effect thereof, it is effective in varying the space (gap)
between the circuit board 10 and the semiconductor chip 20 in the
step of heating the resin.
[0085] FIGS. 5(a) to 5(c) are views showing an example in which the
gap between the circuit board 10 and the semiconductor chip 20 is
varied in the step of generating the gas bubbles from the gas
bubble generating agent contained in the resin 13 in the step of
heating the resin 13 and causing the resin 13 to be self-assembled
between the terminals by the growth of the gas bubbles.
[0086] FIG. 5(a) shows the state in which the resin 13 containing
the conductive particles 12 and the gas bubble generating agent
(not shown) is supplied into the space between the circuit board 10
and the semiconductor chip 20. At this time, the gap L.sub.1
between the circuit board 10 and the semiconductor chip 20 is
small.
[0087] From this state, the resin 13 is heated, while the gap
L.sub.2 between the circuit board 10 and the semiconductor chip 20
is increased, as shown in FIG. 5(b). In the heating step, the gas
bubbles 30 generated from the gas bubble generating agent gradually
grow and, in the growing process, the gap L.sub.2 between the
circuit board 10 and the semiconductor chip 20 is also gradually
increased. This allows a given amount of the resin 13 initially
supplied into the space between the circuit board 10 and the
semiconductor chip 20 to be efficiently self-assembled between the
connecting terminals 11 and the electrode terminals 21.
[0088] FIG. 5(c) shows the state of the resin 13 self-assembled
between the facing terminals at the time at which the gap between
the circuit board 10 and the semiconductor chip 20 is L.sub.3, in
which the resin 13 scarcely remains between the adjacent terminals.
This is because most of the resin 13 which is not self-assembled
between the terminals is pushed from the space between the circuit
board 10 and the semiconductor chip 20 toward the outside under the
pressure of the grown gas bubbles 30.
[0089] Although the description has been given to the example in
which the gap between the circuit board 10 and the semiconductor
chip 20 is increased in the heating step in FIGS. 5(a) to 5(c), the
same operation and effect can be obtained even when the heating
step is performed while periodically varying the gap.
[0090] A characteristic feature of the flip chip mounting method of
the present invention is that the gas bubbles are generated from
the gas bubble generating agent contained in the resin 13 to grow
and cause the resin 13 to be self-assembled between the terminals.
Although the gas bubble generating agent used in the example shown
in FIGS. 1(a) to 1(d) and FIGS. 2(a) to 2(c) is made of one
material, the gas bubble generating agent may also be made of two
or more materials having, e.g., different boiling temperatures.
[0091] FIG. 6 is a view showing an example in which two gas bubble
generating agents having different boiling temperatures are
contained in the resin 13, which shows the state of the gas bubbles
generated from the gas bubble generating agents. Gas bubbles 30a
generated from the gas bubble generating agent having a lower
boiling temperature are larger than gas bubbles 30b generated from
the gas bubble generating agent having a higher boiling temperature
because the growth of the gas bubbles 30a is temporally leading
that of the gas bubbles 30b.
[0092] The growing gas bubbles 30b push the resin 13 toward the
outside thereof under the growing pressure thereof and can move a
part of the resin 13 into the space between the connecting
terminals 11 of the circuit board 10 and the electrode terminals 21
of the semiconductor chip 20, while there is also the resin 13 left
behind. By repeating the operation of causing the gas bubbles 30b,
which are retarded in growth, to push the resin 13 left behind
again toward the outside thereof, the resin 13 can be efficiently
moved into the space between the terminals. This allows uniform
self-assembly of the resin 13 between the terminals.
[0093] The resin 13, the conductive particles 12, and the gas
bubble generating agent used in the flip chip mounting method of
the present invention are not particularly limited, but the
following materials can be used respectively therefor.
[0094] As the resin 13, there can be used a thermosetting resin
such as an epoxy resin, a phenol resin, or a silicone resin, or a
thermoplastic resin. However, the resin 13 preferably has a
viscosity on the order which at least allows the resin 13 to flow
in the heating step.
[0095] As the conductive particles 12, Cu, Ag, AgCu, or the like
can be used. In the present invention, electrical connection
between the terminals is intended to be achieved by contact between
the individual conductive particles so that it is preferable to
maximally suppress the growth of an oxide film on the surface of
each of the conductive particles. It is also possible to implement
a state in which only the surfaces of the conductive particles in
contact with each other are melted to form metal bonding at the
interfaces therebetween. The content of the conductive particles 12
in the resin 13 is preferably in the range of, e.g., about 0.5% to
30% by volume. The content of the gas bubble generating agent in
the resin 13 is preferably in the range of, e.g., about 0.1% to 20%
by weight.
[0096] As the gas bubble generating agent, any of the materials
shown in FIG. 7 can be used. To prevent the conductive particles 12
from melting in the heating step for generating the bas bubbles (a
gas such as H.sub.2O, CO.sub.2, or N.sub.2) from the gas bubble
generating agent, it is necessary to select the material having a
boiling temperature lower than the melting temperature of the
conductive particles 12 during the generation of the gas
bubbles.
[0097] As the gas bubble generating agent, a material which is
thermally decomposed to generate the gas bubbles when the resin is
heated may also be used. As such a gas bubble generating agent, any
of the materials shown in FIG. 8 can be used. In the case of using,
e.g., a compound containing water of crystallization (aluminum
hydroxide), the compound is thermally decomposed when the resin is
heated and water vapor is generated as gas bubbles.
[0098] In the flip chip mounting method described thus far, the
semiconductor chip 20 may also be a structure (such as, e.g., a CSP
or a BGA) in which a semiconductor bare chip is mounted on an
interposer having a plurality of electrode terminals (lands). The
present invention is applicable not only to flip chip mounting but
also to substrate-to-substrate connection for achieving electrical
connection between the respective electrodes of substrates each
having the plurality of electrode terminals. The
substrate-to-substrate connection can be achieved by the following
method.
[0099] First, a resin containing conductive particles and a gas
bubble generating agent is supplied into the space between a first
substrate and a second substrate each having a plurality of
electrodes. Thereafter, the resin is heated to generate gas bubbles
from the gas bubble generating agent contained in the resin. In the
heating step, the resin is pushed toward the outside of the gas
bubbles generated from the gas bubble generating agent by the
growth thereof and self-assembled between the electrodes of the
first substrate and the electrodes of the second substrate.
[0100] Then, the second substrate is pressed against the first
substrate to bring the conductive particles contained in the resin
self-assembled between the facing electrodes into contact with each
other. This allows electrical connection between the facing
electrodes.
[0101] Finally, the resin self-assembled between the electrodes is
cured to fix the first substrate to the second substrate, whereby
the substrate-to-substrate connection is completed.
[0102] As the first substrate or the second substrate, there can be
used a circuit board, a semiconductor wafer, a semiconductor chip
(including a bare chip and a mounted chip), or the like.
[0103] To the substrate-to-substrate connection also, the various
conditions or methods described in the flip chip mounting method
described above are applicable. For example, to a temperature
profile in the step of heating resin 13, the profile shown in FIG.
3(a) is applicable. To the variation in the gap between the
substrates, the method shown in FIG. 5 is applicable.
[0104] For the resin 13, the conductive particles 12, and the gas
bubble generating agent to be used also, the materials described in
the flip chip mounting method can also be appropriately selected
and used.
[0105] Heretofore, the flip chip mounting method and the method for
connecting substrates according to the present invention have been
described. An apparatus for fabricating a flip chip mounting body
by practicing the flip chip mounting method can be implemented with
a flip chip mounting apparatus 40 as shown in FIG. 9.
[0106] As shown in the block diagram of FIG. 9, the flip chip
mounting apparatus 54 comprises holding means 41 for holding the
semiconductor chip 20 and the circuit board 10 in mutually facing
relation with a given space provided therebetween, supplying means
42 for supplying the resin 13 containing the conductive particles
12 and the gas bubble generating agent into the space between the
semiconductor chip 20 and the circuit board 10, heating means 43
for heating the resin 13, and pressing means 46 for pressing the
semiconductor chip 20 against the circuit board 10. The heating
means 43 has first heating means 44 for controlling a temperature
to a value at which the gas bubbles are generated from the gas
bubble generating agent contained in the resin 13 and second
heating means 45 for controlling the temperature to a value at
which the resin 13 is thermally cured.
[0107] The holding means 41 has an additional alignment mechanism
for aligning the positions of the electrode terminals of the
semiconductor chip 20 with respect to those of the connecting
terminals of the circuit board 10. When the resin is in the form of
a paste, the supplying means 42 can use a dispenser or the like and
the heating means 43 can use a heating stage (hot plate) or a
heating box (oven) heated with a hot blast or an infrared ray.
[0108] In the flip chip mounting apparatus 40, the resin 13 heated
with the first heating means 44 is pushed toward the outside of the
gas bubbles generated from the gas bubble generating agent by the
growth thereof and self-assembled between the connecting terminals
11 of the circuit board 10 and the electrode terminals 21 of the
semiconductor chip 20. By further pressing the semiconductor chip
20 against the circuit board 10 with the pressing means 46, the
conductive particles 12 contained in the resin 13 self-assembled
between the facing electrodes are brought into contact with each
other, whereby the flip chip mounting body is completed.
[0109] A method which simultaneously performs the provision of
electrical connection between the facing terminals of a
semiconductor chip and a circuit board and the fixation of the
semiconductor chip to the circuit board using a resin containing a
solder powder (conductive particles) is disclosed in each of Patent
Document 5 (Japanese Laid-Open Patent Publication No. 2002-26070)
and Patent Document 6 (Japanese Laid-Open Patent Publication No.
HEI 11-186334). In the method disclosed in each of the documents,
the respective portions of the facing terminals of the
semiconductor chip and the circuit board which are in contact with
each other are soldered by melting the solder powder contained in
the resin and then the semiconductor chip is encapsulated in and
fixed to the circuit board by curing the resin. Although the method
disclosed in each of the documents apparently seems to be a similar
technique to the present invention, the method solders the
terminals by a so-called reflow process. Accordingly, the solder
powder is dispersed in the resin even after resin encapsulation
and, unlike in the present invention, it is not intended to achieve
electrical connection between the terminals by causing the resin
containing the conductive particles to be self-assembled between
the facing terminals and then bringing the conductive particles
contained in the resin into contact with each other. Therefore, the
method disclosed in each of the documents is a technique
essentially different from the present invention.
[0110] On the other hand, a method which simultaneously performs
the provision of electrical connection between the facing terminals
of a semiconductor chip and a circuit board and the fixation of the
semiconductor chip to the circuit board, each using a resin
containing conductive particles (low-melting-point metal filler),
is described in each of Patent Document 7 (Japanese Laid-Open
Patent Publication No. 2004-260131) and Non-Patent Document 1
(Masahiro Yasuda et al., "Self-Organized Joining Assembly Process
by Electrically Conductive Adhesive Using Low Melting Point Filler"
10th Symposium on "Microjoining and Assembly Technology in
Electronics, pp. 183 to 188, 2004). Each of the documents discloses
a technique in which conductive particles selectively form
self-organized connectors between terminals by using a resin having
an oxidizing/reducing ability based on the aggregation and wetting
of the molten metal filler contained in the resin.
[0111] However, Patent Document 7 and Non-Patent Document 1 do not
go beyond indicating the probability of a process which selectively
(in a self-assembled manner) joins the facing terminals and merely
causes aggregation (self-assembly) by relying only on the
wettability of the molten conductive particles. As a result, it is
difficult to uniformly form the connectors between the
terminals.
[0112] The present invention has been achieved based on the
recognition that, since the resin containing the conductive
particles does not function as the "sea" in which the conductive
particles can freely move, the bonding process of the conductive
particles does not uniformly proceed and, consequently, uniform
connectors cannot be formed between the terminals. Therefore, by
applying the method according to the present invention, it is
possible to perform high-yield flip chip mounting of a
semiconductor chip having a large number of electrode terminals so
that a useful method applicable to a mass production process is
provided.
[0113] Although the present invention has thus been described using
the preferred embodiments thereof, such a description is not a
restrictive matter and various modifications can be naturally
made.
INDUSTRIAL APPLICABILITY
[0114] In accordance with the present invention, it is possible to
provide a flip chip mounting method which is applicable to the flip
chip mounting of a next-generation LSI and high in productivity and
reliability as well as a method for connecting substrates.
* * * * *