U.S. patent application number 11/503907 was filed with the patent office on 2007-09-20 for bonding apparatus and bonding method.
This patent application is currently assigned to FUJITSU LIMITED. Invention is credited to Yuzo Shimobeppu, Yoshiaki Shinjo, Kazuo Teshirogi, Kazuhiro Yoshimoto.
Application Number | 20070215673 11/503907 |
Document ID | / |
Family ID | 38516747 |
Filed Date | 2007-09-20 |
United States Patent
Application |
20070215673 |
Kind Code |
A1 |
Yoshimoto; Kazuhiro ; et
al. |
September 20, 2007 |
Bonding apparatus and bonding method
Abstract
To provide a bonding apparatus capable of increasing product
quality by realizing high-precision control of a pressing force
applied upon mounting of an electronic component on a substrate by
bonding, and to a bonding method capable of providing high-quality
products stably. The bonding apparatus includes: at least a bonding
head 100 for pressing an electronic component 6 against a substrate
1 to bond it to the substrate 1; a plurality of load detection
mechanisms (e.g., load sensors 5) substantially equally spaced so
as to face one another under a substrate stage S supporting the
substrate 1 provided with the electronic component 6; and a
pressure detection unit 20 for detecting pressing force at the
bonding surface between the electronic component 6 and substrate 1
on the basis of the pressure values detected by the individual load
detection mechanisms 5.
Inventors: |
Yoshimoto; Kazuhiro;
(Kawasaki, JP) ; Shimobeppu; Yuzo; (Kawasaki,
JP) ; Teshirogi; Kazuo; (Kawasaki, JP) ;
Shinjo; Yoshiaki; (Kawasaki, JP) |
Correspondence
Address: |
WESTERMAN, HATTORI, DANIELS & ADRIAN, LLP
1250 CONNECTICUT AVENUE, NW, SUITE 700
WASHINGTON
DC
20036
US
|
Assignee: |
FUJITSU LIMITED
Kawasaki
JP
|
Family ID: |
38516747 |
Appl. No.: |
11/503907 |
Filed: |
August 15, 2006 |
Current U.S.
Class: |
228/101 |
Current CPC
Class: |
H01L 2224/7592 20130101;
H01L 2224/75252 20130101; H05K 13/08 20130101; H01L 2224/75
20130101; H01L 2924/01033 20130101; H01L 2224/16 20130101; H01L
21/67144 20130101; H05K 13/082 20180801; H01L 2924/01006 20130101;
H01L 24/75 20130101; H01L 2224/75251 20130101; H05K 13/046
20130101; H01L 2924/01082 20130101 |
Class at
Publication: |
228/101 |
International
Class: |
A47J 36/02 20060101
A47J036/02 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 17, 2006 |
JP |
2006-075375 |
Claims
1. A bonding apparatus, comprising: a bonding head configured to
press an electronic component against a substrate to bond the
electronic component to the substrate; a plurality of load
detection mechanisms that are substantially equally spaced so as to
face one another under a substrate stage which supports the
substrate arranged to face the electronic component; and a pressure
detection unit configured to detect a pressure on a bonding surface
between the electronic component and the substrate on the basis of
pressure values detected by the individual load detection
mechanisms.
2. The bonding apparatus according to claim 1, wherein the
electronic component has a polygonal shape, and the load detection
mechanisms are disposed at positions corresponding to the corners
of the electronic component.
3. The bonding apparatus according to claim 2, wherein the
electronic component has a square shape, and the load detection
mechanism are disposed at positions corresponding to the corners of
the electronic component.
4. The bonding apparatus according to claim 1, wherein the load
detection mechanisms are disposed in a matrix form.
5. The bonding apparatus according to claim 1, further comprising:
a pressure adjustment unit configured to adjust a pressing force of
the bonding head; and a control unit configured to control the
pressure adjustment unit, wherein the control unit performs
feedback control on the pressure adjustment unit while comparing a
predetermined reference pressure value with the total of the
pressure values detected by the individual load detection
mechanisms.
6. The bonding apparatus according to claim 5, wherein upper and
lower thresholds for a pressing force on each of the load detection
mechanisms are previously set in the control unit on the basis of
the pressure values detected by the individual load detection
mechanisms.
7. The bonding apparatus according to claim 5, wherein upper and
lower thresholds for a pressing force on each row of the load
detection mechanisms are previously set in the control unit on the
basis of the pressure values detected by the individual load
detection mechanisms.
8. The bonding apparatus according to claim 6, wherein the
occurrence of abnormality is indicated when the pressure value
detected by the load detection mechanism has exceeded the
threshold.
9. The bonding apparatus according to claim 8, wherein the
operation of the bonding apparatus is halted.
10. A bonding method, comprising: pressing an electronic component
against a substrate by means of a bonding head to bond the
electronic component to the substrate; detecting a pressure at a
bonding surface between the electronic component and the substrate
on the basis of pressure values detected by a plurality of load
detection mechanisms that are substantially equally spaced so as to
face one another under a substrate stage which supports the
substrate arranged to face the electronic component.
11. The bonding method according to claim 10, wherein the
electronic component has a polygonal shape, and the load detection
mechanisms are disposed at positions corresponding to the corners
of the electronic component.
12. The bonding method according to claim 11, wherein the
electronic component has a square shape, and the load detection
mechanisms are disposed at positions corresponding to the corners
of the electronic component.
13. The bonding method according to claim 10, wherein the load
detection mechanisms are disposed in a matrix form.
14. The bonding method according to claim 10, further comprising:
adjusting a pressing force of the bonding head; and performing
feedback control on the pressing force while comparing a
predetermined reference pressure value with the total of the
pressure values detected by the individual load detection
mechanisms.
15. The bonding method according to claim 14, wherein in the
feedback control step upper and lower thresholds for a pressing
force on each of the load detection mechanisms are previously set
on the basis of the pressure values detected by the individual load
detection mechanisms.
16. The bonding method according to claim 14, wherein in the
feedback control step upper and lower thresholds for a pressing
force on each row of the load detection mechanisms are previously
set on the basis of the pressure values detected by the individual
load detection mechanisms.
17. The bonding method according to claim 15, wherein the
occurrence of abnormality is detected when the pressure value
detected by the load detection mechanism has exceeded the
threshold.
18. The bonding method according to claim 17, wherein the operation
of the pressing step is halted.
19. The bonding method according to claim 10, wherein traceability
is ensured for the bonding status of the bonding surface between
the electronic component and the substrate on the basis of the
pressure values detected by the individual load detection
mechanisms.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefits of
the priority from the prior Japanese Patent Application No.
2006-075375 filed on Mar. 17, 2006, the entire contents of which
are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a bonding apparatus capable
of increasing product quality by realizing high-precision control
of a pressing force applied upon mounting of an electronic
component on a substrate by bonding, and to a bonding method
capable of providing high-quality products stably.
[0004] 2. Description of the Related Art
[0005] Electronic devices (e.g., computers) have become faster and
smaller, and there is an increasing demand for high-density
packaging of electronic components. Against this background,
substrates for large scale integration have been used, in which a
plurality of electronic components is arranged on a substrate in
layers. In addition, for tighter packing of electronic components,
flip-chip bonding has been employed in which bumps are formed on an
electronic component that is to be mounted on a substrate, and the
bumps are then pressed against the substrate and welded thereto.
High pin count and device miniaturization have been realized in
this approach, with an increasing demand for reduced bump diameter
and reduced pitch between bump connection terminals.
[0006] However, if bump connection terminal pitch reaches as small
as 40 .mu.m or less, a concern arises regarding the occurrence of
connection defects, such as short-circuits between terminals, and
damages to the electric component if it fails to achieve
high-precision positioning (tolerances to .+-.1 .mu.m) and/or
stable load control because of variations in the fabrication
precision of the substrate and in the formation of bumps. Short
circuits between terminals occur due to, for instance, excessively
crushed bumps and displacement after recognition. Damages to the
electronic component include failures of, for example, bumps and
terminals of the electronic component and substrate.
[0007] The following bonding apparatus has been conventionally used
for electronic component bonding: A bonding apparatus which has a
bonding tool provided so as to be capable of moving up and down,
and a load sensor for detecting load that has been applied to an
electronic component by the bonding tool. In such a bonding
apparatus the load sensor is provided on the upper side of the
bonding tool support and the load sensor is allowed to contact the
bonding tool support to cause both a bonding head attached with the
bonding tool and load sensor to move down, bonding the electronic
component to the substrate. The bonding apparatus is so configured
that, at this point, load (pressing force) applied by the bonding
tool is detected by the load sensor that is in contact with the
bonding tool.
[0008] The followings are specific examples of conventional bonding
apparatus used: A bonding apparatus in which a bonding tool support
is suspended from a head unit by a spring (see Japanese Patent
Application Laid-Open (JP-A) No. 2000-183114); a bonding apparatus
equipped with two different load detection mechanisms: one
configured to detect decreasing load, and one configured to detect
increasing load, at a time when a given level of load applied to a
bonding tool support has caused a bonding tool to press an
electronic component (see Japanese Patent Application Laid-Open
UP-A) No. 2002-76061); a bonding apparatus configured to carry out
feedback control by previously creating a given level of thrust in
a cylinder (see Japanese Patent Application Laid-Open UP-A) No.
2001-68895); and a bonding apparatus in which a bonding head is
provided with a parallelism adjustment mechanism by which the
parallelism of a bonding tool is determined by a parallelism
detection sensor (see Japanese Patent Application Laid-Open (JP-A)
No. 2001-223244).
[0009] However, when high-precision positioning and high-precision
load control are required in connection with reduced pitch between
bump connection terminals, variations occur in the in-plane stress
due to variations in the precision of components (e.g., substrates
and bumps), even though the detected load values falls within a set
reference load for a bonding operation, leading to reduced product
yields due to connection failures and the like.
[0010] With respect to the set reference load--a whole pressure
created during a bonding operation--there arises the following
problem: The bonding tool support is provided with a number of
components: mechanical sections (e.g., slide guides, a shaft, a
cylinder and a spring) that constitute a lifting and lowering
mechanism; mechanical sections for attaching and cooling an
electronic component and for adjusting the inclination of the
electronic component; and a number of parts (e.g., wires and pipes)
for connecting these mechanical sections together. Thus, in a case
of a load sensor provided on the upper side of the bonding tool
support, available locations or areas for the load sensor are
limited. In addition, the load sensor is susceptible to heat
generated due to friction of the components and thus tends to
produce different values for the detected load. The measured
pressure value only means the load applied to the bonding tool
support, and includes escaping loads such as inclined loads acting
on the components, and horizontal components. For this reason, the
measured load value is not necessarily equal to the value for load
acting on the bonding portions, thus requiring periodical load
calibration.
[0011] Accordingly, bonding apparatuses with conventional load
detection mechanisms, as disclosed in the foregoing Patent
Literatures, cannot achieve further increase in the product
quality; therefore, bonding technology has been sought after that
enables high-precision pressing force control for increased product
quality.
[0012] It is an object of the present invention to solve the
foregoing conventional problems and to achieve the object described
below.
[0013] Specifically, it is an object of the present invention to
provide a bonding apparatus capable of increasing product quality
by realizing high-precision control of a pressing force applied
upon mounting of an electronic component on a substrate by bonding,
and to a bonding method capable of providing high-quality products
stably.
SUMMARY OF THE INVENTION
[0014] The following is the means for solving the foregoing
problems:
[0015] The bonding apparatus of the present invention includes at
least: a bonding head configured to press an electronic component
against a substrate to bond the electronic component to the
substrate; a plurality of load detection mechanisms that are
substantially equally spaced so as to face one another under a
substrate stage which supports the substrate arranged to face the
electronic component; and a pressure detection unit configured to
detect a pressure on a bonding surface between the electronic
component and the substrate on the basis of pressure values
detected by the individual load detection mechanisms.
[0016] In this bonding apparatus the plurality of load detection
mechanisms is provided under the substrate stage in such a way that
they are substantially equally spaced so as to face one another,
for example, in a matrix form. For this reason, spaces on a planar
surface where such load detection mechanisms are arranged can be
more readily secured in the bonding apparatus of the present
invention than in conventional ones where the load detection
mechanisms are arranged in the vicinity of the bonding tool
support. In addition, there are no complex components around the
load detection mechanisms and there is no need to move up or down
them, thus allowing detection of the net load applied to the
substrate stage. Furthermore, the provision of the plurality of
load detection mechanisms allows measurement of the pressure
distributed over the substrate stage surface and high-precision
control of a pressing force of the bonding head. Thus, it is
possible to increase product quality.
[0017] The bonding method of the present invention includes at
least a pressing step of pressing an electronic component against a
substrate by means of a bonding head to bond the electronic
component to the substrate; and a pressure detection step of
detecting a pressure at a bonding surface between the electronic
component and the substrate on the basis of pressure values
detected by a plurality of load detection mechanisms that are
substantially equally spaced so as to face one another under a
substrate stage which supports the substrate arranged to face the
electronic component.
[0018] With this bonding method, in the pressing step, the
electronic component is first pressed against the substrate by
means of the bonding head and is thereby bonded to the substrate.
In the pressure detection step, the pressure at a bonding surface
between the electronic component and the substrate is detected on
the basis of pressure values detected by a plurality of load
detection mechanisms that are substantially equally spaced so as to
face one another under a substrate stage which supports the
substrate arranged to face the electronic component. As a result,
the net load applied to the substrate stage is detected, the
pressure distributed over the substrate stage surface is measured,
and the pressing force of the bonding head is controlled with high
precision. Thus, it is possible to stably provide high-quality
products with high yields.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a cross sectional view for explaining a schematic
configuration of a bonding apparatus of a first embodiment of the
present invention.
[0020] FIG. 2 is a plan view for explaining a schematic
configuration of a load detection mechanism in the bonding
apparatus of the first embodiment of the present invention.
[0021] FIG. 3A is a first schematic explanatory diagram of an
example of a modification of the load detection mechanism in the
bonding apparatus of the first embodiment of the present
invention.
[0022] FIG. 3B is a second schematic explanatory diagram of an
example of a modification of the load detection mechanism in the
bonding apparatus of the first embodiment of the present
invention.
[0023] FIG. 3C is a third schematic explanatory diagram of an
example of a modification of the load detection mechanism in the
bonding apparatus of the first embodiment of the present
invention.
[0024] FIG. 4 is a flowchart for explaining an operation (bonding
method) of the bonding apparatus of the first embodiment of the
present invention.
[0025] FIG. 5A is a first schematic explanatory diagram showing a
bonding operation by means of a bonding method using the bonding
apparatus of the first embodiment of the present invention.
[0026] FIG. 5B is a second schematic explanatory diagram showing
the bonding operation by means of a bonding method using the
bonding apparatus of the first embodiment of the present
invention.
[0027] FIG. 6A is graph showing an example of a plot of reference
load vs. time in the bonding apparatus of the first embodiment of
the present invention.
[0028] FIG. 6B is graph showing an example of a plot of load vs.
time, the load detected by an individual load sensor of the bonding
apparatus of the first embodiment of the present invention.
[0029] FIG. 7A is a first schematic explanatory diagram showing an
example of trouble that occurs during a bonding operation carried
out by means of the bonding method using the bonding apparatus of
the first embodiment of the present invention.
[0030] FIG. 7B is a second schematic explanatory diagram showing an
example of trouble that occurs during a bonding operation carried
out by means of the bonding method using the bonding apparatus of
the first embodiment of the present invention.
[0031] FIG. 7C is a third schematic explanatory diagram showing an
example of trouble that occurs during a bonding operation carried
out by means of the bonding method using the bonding apparatus of
the first embodiment of the present invention.
[0032] FIG. 7D is a fourth schematic explanatory diagram showing an
example of trouble that occurs during a bonding operation carried
out by means of the bonding method using the bonding apparatus of
the first embodiment of the present invention.
[0033] FIG. 7E is a fifth schematic explanatory diagram showing an
example of trouble that occurs during a bonding operation carried
out by means of the bonding method using the bonding apparatus of
the first embodiment of the present invention.
[0034] FIG. 7F is a sixth schematic explanatory diagram showing a
example of trouble that occurs during a bonding operation carried
out by means of the bonding method using the bonding apparatus of
the first embodiment of the present invention.
[0035] FIG. 8A is a first graph showing another plot of load vs.
time, the loads detected by the individual load sensors of the
bonding apparatus of the first embodiment of the present
invention.
[0036] FIG. 8B is a second graph showing still another plot of load
vs. time, the loads detected by the individual load sensors of the
bonding apparatus of the first embodiment of the present
invention.
[0037] FIG. 9A is a first step view for explaining a substrate
transportation operation carried out in the bonding apparatus of
the first embodiment of the present invention.
[0038] FIG. 9B is a second step view for explaining the substrate
transportation operation carried out in the bonding apparatus of
the first embodiment of the present invention.
[0039] FIG. 9C is a third step view for explaining the substrate
transportation operation carried out in the bonding apparatus of
the first embodiment of the present invention.
[0040] FIG. 9D is a fourth step view for explaining the substrate
transportation operation carried out in the bonding apparatus of
the first embodiment of the present invention.
[0041] FIG. 10A is a cross-sectional view for explaining an example
of the schematic configuration of a conventional bonding
apparatus.
[0042] FIG. 10B is a cross-sectional view for explaining another
example of the schematic configuration of a conventional bonding
apparatus.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0043] Hereinafter, the bonding apparatus and bonding method of the
present invention will be described in detail with reference to the
drawings.
Embodiment 1
[0044] The first embodiment of the bonding apparatus of the present
invention will be described with reference to the drawings.
[0045] FIG. 1 is a cross-sectional view showing a schematic
configuration of the bonding apparatus according to the first
embodiment of the present invention.
[0046] The bonding apparatus shown in FIG. 1 is one carrying out
flip chip bonding, and has a bonding head 100. The bonding head 100
has a function of heating and pressurizing (pressing) an electronic
component having bumps to bond the bumps to connection terminals of
a substrate 1.
[0047] As shown in FIG. 1, the bonding head 100 includes a bonding
tool support 10 having a bonding tool 7 which operates by attaching
thereto an electronic component 6 by vacuum and a heat mechanism 8
for heating the bonding tool 7 to heat bumps 6A formed on the
electronic component 6 to thereby set bonding temperature to about
180.degree. C. to 350.degree. C. In the bonding tool support 10, a
protruding part 10A is engaged with a cylinder 11 attached to a
C-shaped lifting and lowering block 12, and is held by the lifting
and lowering block 12 via a slidable slide guide 9. In addition, a
.theta. motor 13 is arranged on the top of the bonding tool support
10. The .theta. motor 13 carries out a .theta. rotation correction
upon positioning of the electronic component 6.
[0048] Note that the cylinder 11 may be used without changing its
thrust or may be used while changing its thrust by means of a
later-described pressure adjustment unit 22 (e.g., an
electropneumatic regulator), which makes cylinder thrust variable
by feedback control.
[0049] The lifting and lowering block 12 is connected to a lifting
and lowering mechanism 18 which is comprised of a slide guide 15, a
feed screw 16, and a Z motor 17 arranged on the top of the feed
screw 16, and the flat side wall of the C-shaped lifting and
lowering block 12 is held by the feed screw 16 via the slidable
slide guide 15. When load is applied to the electronic component 6
more than necessity, the lifting and lowering block 12 connected to
the lifting and lowering mechanism 18 is allowed to move up and
down for feedback control on the set load, protecting the substrate
1, electronic component 6, load sensor 5, etc. from damages.
[0050] The substrate 1 having connection terminals 1A formed
thereon is placed on a substrate attachment plate 2 that holds the
substrate 1 by vacuum. Under the substrate attachment plate 2, a
substrate heater 3 for heating the substrate 1 and heat insulating
material 4 are provided. The heat insulating material 4 is
supported by a matrix of four load sensors 5 positioned at the four
corners of the heat insulating material 4. Note in this embodiment
that the substrate attachment plate 2, substrate heater 3 and heat
insulating material 4 constitute a substrate stage S.
[0051] Signals from these load sensors 5 are then detected by a
pressure detection unit 20 (e.g., an A/D converter) and transmitted
to a control unit 21 for measurement of both the total load on the
bumps 6A of the electronic component 6 and the pressure distributed
over the substrate stage S surface and for control of the pressure
adjustment unit 22. In this way, set load for bonding operations is
controlled.
[0052] Conventionally, the rating of a load sensor is so determined
that it can support a maximum set load adopted for a bonding
apparatus; within a load range up to 490,33N (50 kgf), 490,33N (50
kgf) is generally adopted for the rating of load sensors for
high-pressure detection, and 49.03N (5 kgf) for the rating of load
sensors for low-pressure detection. For this reason, when a set
load ranges from 49.03N (5 kgf) to 147.10N (15 kgf), the load
sensor is rated at 50 kgf, which results in poor precision.
[0053] The bonding apparatus according to the first embodiment of
the present invention, however, has four load sensors 5 and thus a
maximum load is equally shared by them. For this reason, even when
a maximum load of 490,33N (50 kgf) is applied, the load on per one
load sensor 5 is reduced by a factor of 4 (i.e., 122.58N (12.5
kgf)). Thus, it is possible to increase the linearity of the
hysteresis curve and/or hysteresis characteristics by reducing the
ratings of the load sensors 5.
[0054] The operation frequency of the lifting and lowering
mechanism that has the slide guides, spring, cylinder, etc. is very
high in view of the units of the semiconductor device manufactured.
The lifting and lowering mechanism is susceptible to heat generated
due to friction of the foregoing complex components; thus, the
status of the bonding apparatus is likely to change accordingly.
The bonding apparatus according to the first embodiment of the
present invention, however, has no complex lifting and lowering
mechanism and has a matrix of the immobilized four load sensors 5
under the substrate 1, allowing detection of the net load applied
to the portions where the bumps 6A and corresponding connection
terminals 1A are bonded together, and of the pressure distributed
over the substrate stage S surface.
[0055] Next, the load detection mechanism in the bonding apparatus
according to the first embodiment of the present invention will be
described. FIG. 2 is a plan view showing the load detection
mechanism in the bonding apparatus.
[0056] As shown in FIG. 2, the substrate 1 is attached by vacuum to
the substrate attachment plate 2 that has a vacuum aspiration
groove corresponding to the shape of the substrate 1. The substrate
heater 3 for heating the substrate 1 is provided under the
substrate attachment plate 2, heating the substrate 1 to about
100.degree. C. in general. The load sensors 5 are provided under
the substrate heater 3 with the heat insulating material 4
interposed between them. The permissible temperature range for the
load sensors 5 generally ranges from about 50.degree. C. to
100.degree. C., and therefore, both the load sensors 5 and a drive
unit (not shown) that moves the substrate stage S need to be
protected against heat (about 180.degree. C. to 350.degree. C.)
generated upon heating of the substrate 1 and bonding of the
electronic component 6. To this end, the heat insulating material 4
and a cooling mechanism (not shown) are arranged.
[0057] In this embodiment the four load sensors 5--the first load
sensor 5A, second load sensor 5B, third load sensor 5C, and fourth
load sensor 5D--are substantially equally spaced along the
perimeter of the substrate attachment plate 2 so as to face one
another, forming a matrix of load sensors provided at positions
corresponding to the four corners of the substrate attachment plate
2, as shown in FIG. 2. The detection signal from each of the load
sensors 5A to 5D is outputted to the control unit 21 via the
pressure detection unit 20 (e.g., an A/D converter).
[0058] The shape and locations of the load sensors 5 are not
particularly limited; various modifications can be made as
described below. For example, as shown in FIG. 3A, the substrate
stage S may be immobilized by means of strain gauges as the load
sensors 5. As shown in FIG. 3B, other mechanisms (e.g., load cells)
as the load sensors 5 may be combined, and a guide part G may be
provided to make the substrate stage S mobile. As shown in FIG. 3C,
in addition to the foregoing load sensors 5A to 5D, additional four
load sensors--the fifth load sensor 5E, sixth load sensor 5F,
seventh load sensor 5G, and eighth load sensor 5H--may be provided
in such a way that they are substantially equally spaced along the
perimeter of the substrate attachment plate 2 so as to face one
another in a matrix form. As shown in FIG. 3C, as the number of the
load sensor 5 increases (8 in FIG. 3C), so too does the number of
load detection points, allowing acquisition of more detailed load
detection data.
[0059] The bonding operation (bonding method of the present
invention) carried out by the bonding apparatus will be described
with reference to the flowchart shown in FIG. 4.
[0060] As a pressure load (whole bonding load) applied to bond the
connection terminals 1A of the substrate 1 to the bumps 6A of the
electronic component 6, a reference pressure and the descending
speed of the bonding tool 7 are set by the control unit 21 (e.g., a
microcomputer). In this embodiment, pressure values detected by the
load sensors 5A to 5D are used to set the upper and lower
thresholds for a pressing force on each of the load sensors 5A to
5D. The thresholds are appropriately determined according to the
constitutional material, structure, size, etc. of the substrate 1,
bumps 6A, etc. Alternatively, they can be determined by detecting
either pressure acting on one load sensor positioned at one corner
of an electronic component or pressure acting on a side of the
electronic component having a combination of load sensors (i.e.,
pressure acting on a row of load sensors), on the basis of the
pressure acting on one bump, data concerning the connection
terminal strength that results in defects, etc. Moreover, if the
pressing force exceeds the thresholds, alarm notifications are sent
and/or the apparatus operation is halted, enabling early
notification of the occurrence of abnormalities.
[0061] As shown in FIG. 5A, in a bonding operation, the bonding
tool 7 is moved down by means of the lifting and lowering mechanism
18, so that bonding load has a reference pressure. In this way the
electronic component 6 attached to the bonding tool 7 by vacuum
moves down toward the connection terminals 1A formed on the
substrate 1. As shown in FIG. 5B, pressure values, detected by the
load sensors 5A to 5D during a period from the time when the
electronic component 6 and substrate 1 make first contact to the
time when the bonding tool 7 is completely lifted after a
predetermined period of a bonding operation, are transmitted to the
control unit 21. As shown in FIG. 4, the control unit 21 then
compares the predetermined reference pressure with the total of the
pressure values detected by the load sensors 1 to 4 (load sensors
5A to 5D) to perform feedback control on the pressure adjustment
unit 22. In this way a digital flow rate-regulating valve is
adjusted by a pressure motor driver to adjust the flow rate in the
cylinder 11. The flow rate in the cylinder 11 is detected and
transmitted to the control unit 21. Each of the detected pressure
values thus sampled is compared with the upper and lower thresholds
for the pressing force that have been previously set for one corner
and one side of the electronic component 6. When the detected
pressure values--even within the set reference pressure--exceeded
these upper and lower thresholds, it is determined that
abnormalities have occurred, followed by sending of alarm
notification and halt of the apparatus operation. Thus, the
electronic component 6 can be protected from being damaged.
Moreover, detected pressure values sampled for each bonding
operation can be monitored over time, stored as a manufacture
status history. It is therefore possible to increase product
quality and to ensure traceability of products.
[0062] Next, with reference to FIGS. 6A and 6B, description will be
provided how the load sensors 5A to 5D detect pressure.
[0063] A graph as shown in FIG. 6A is given by plotting the change
in X, a bonding load reference pressure (reference pressure per one
electronic component), versus time. The bonding load reference
pressure equals to the total of the pressure values, which have
been detected by the load sensors 5A to 5D during a period from the
time when a reference pressure is applied to the electronic
component 6 as a result of contact between the electronic component
6 and substrate 1 to the time when the bonding tool 7 is completely
lifted after a predetermined period of a bonding operation.
[0064] When the load sensors 5A to 5D are equally pressed, X1, a
detected pressure value per one load sensor, is four times as small
as the bonding load reference pressure X, as shown in FIG. 6B. This
means that load is equally distributed on the bumps 6A of the
electronic component 6. In this state, there is no concern for
damages to the electronic component 6.
[0065] Troubles that occur during a bonding operation are shown in
FIGS. 7A to 7F. In FIG. 7A, the bonding tool 7 is inclined and is
out of parallelism relative to the substrate stage S. In FIG. 7B,
the substrate stage S is inclined and is out of parallelism
relative to the bonding tool 7. In FIG. 7C, the bumps 6A are
different in height. In either case, connection failures have
occurred between the connection terminals 1A and bumps 6A. In FIG.
7D, foreign material D is trapped between the substrate 1 and
substrate stage S. In FIG. 7E, foreign material D is trapped
between the electronic component 6 and bonding tool 7. In FIG. 7F,
foreign material D is trapped between the connection terminal 1A
and bump 6A. In either case, connection failures have occurred. In
addition, such connection failures occur due to, for example,
variations in the substrate and in the chip thickness. Load
detection mechanisms in conventional bonding apparatus cannot find
such connection failures, and a bonding operation finishes after
application of a bonding load reference pressure X (total load
reference pressure per one electronic component) shown in FIG. 6B.
In the first embodiment of the present invention, however, since
thresholds are set for each of the pressure values detected by the
plurality of load sensors 5, it is possible to detect abnormalities
such as connection failures. As described above, with conventional
loading detection mechanisms, no abnormalities can be detected upon
occurrence of component crash, connection failures, etc.,
continuing manufacturing operations. More specifically, load to be
applied over the electronic component converges to a particular
point, resulting in electronic component failure and reduced
production yields. According to the present invention, however, it
is possible to increase product quality and production yields.
[0066] Even when such abnormalities are minor ones that disappear
as the bumps 6A of the electronic component 6 deform, the load
sensors 5A to 5D in this embodiment produce different values for
the detected pressure, allowing detection of such minor
abnormalities. To be more specific, for example, when the bonding
tool 7 and substrate stage S are out of parallelism as shown in
FIGS. 7A and 7B and accordingly the electronic component 6 is
inclined such that load is first applied to the load sensors 5A and
5B shown in FIG. 2, the bonding apparatus is so controlled that a
bonding load reference pressure is applied to them at a
predetermined rate. For this reason, the load detected by the load
sensors 5A and 5B increases first as indicated by X2 of FIG. 8A and
later on, as the bumps 6A deforms by application of pressure, load
is also applied to the load sensors 5C and 5D as indicated by
X3.
[0067] Similarly, when the electronic component 6 is inclined such
that load is applied only to the load sensor 5A at an early stage,
as shown in FIG. 8B, the load detected by the load sensor 5A
increases first as indicated by X4. As the bumps 6A deforms by
application of load, load is also applied to the load sensors 5B
and 5C as indicated by X5 and finally, load is applied to the load
sensor 5D as indicated by X6. Variations in load values among the
load sensors 5A to 5D begin to decrease from the time when load is
uniformly applied to them.
[0068] Thus, there is a time-lag before all of the load sensors 5A
and 5D are uniformly pressed. However, the bonding apparatus
according to this embodiment can detect such a time lag. Load
sensors that are first pressed tend to produce higher values for
the detected pressure than other load sensors; therefore, loads
acting on components (e.g., the electronic component 6, bumps 6A,
and connection terminals 1A on the substrate 1) are compared with
the upper and lower thresholds for the pressing force that are
previously set for one corner and one side of the electronic
component 6, allowing monitoring whether components in the
resulting products have been fabricated within the allowable
strength range. Thus, it is possible to increase product quality
and reliability.
[0069] In this embodiment, although a bonding operation has been
made for one element on the substrate 1 as described above, similar
bonding operations can be made for a plurality of elements arranged
on one substrate. For example, when four elements 31A to 31D are
arranged on a substrate 30 as shown in FIGS. 9A to 9D, the
substrate stage may be fixed and then the substrate 30 may be moved
for the bonding of individual electronic components 6 in the order
from FIG. 9A to FIG. 9D. Alternatively, in this case, the substrate
stage may be divided into several sections before performing
bonding operations. These embodiments are suitable for multiple
bonding and, what is more, are mechanically allowable, for example,
for semiconductor devices with high pin count and large-area
semiconductor devices, which require high load during a bonding
operation.
[0070] With the bonding apparatus and bonding method of the present
invention, a plurality of load sensors is arranged on a substrate
in a matrix form. Load to a bonding portion, applied within the
upper and lower thresholds for the allowable load that have been
previously set for each position where the load sensor detects
load, is feedback-controlled, and the stress distribution over the
substrate stage surface can be monitored. Thus, it is possible to
increase the accuracy and reliability of the load detection
mechanism upon bonding of the electronic component to the substrate
(i.e., upon production of products).
[0071] Since it is possible to find during a bonding operation
troubles (e.g., inclination of the bonding tool, contamination of
foreign material, variations in the level of bumps, connection
failures between substrate's connection terminals, abnormal lifting
and lowering of the bonding tool, and wearing away and/or failure
of the lifting and lowering mechanism), the occurrence of
abnormalities and/or the presence of defective pieces can be
immediately determined, allowing a stable production management at
all times without involving continued production of defective
pieces. Thus, it is possible to provide high-quality products with
high yields.
[0072] In addition, when abnormalities have occurred, alarms can be
issued and the operation of the apparatus can be halted, thus
ensuring the traceability of products for quality management.
Conventional Example
[0073] FIGS. 10A and 10B each shows a schematic configuration of a
conventional bonding apparatus.
[0074] The bonding apparatus shown in FIG. 10A includes a bonding
head 200. The bonding head 200 includes a bonding tool support 210
having a bonding tool 207 which operates by attaching an electronic
component 206 by vacuum thereto and a heat mechanism 208 for
heating the bonding tool 207 to heat bumps 206A formed on an
electronic component 206. In the bonding tool support 210, a
protruding part 210A is engaged with a cylinder 211 attached to a
C-shaped lifting and lowering block 212, and the lower surface of
the protruding part 210A is biased against the lifting and lowering
block 212 by a spring 230. The bonding tool support 210 is held by
the lifting and lowering block 212 via a slidable slide guide 209.
In addition, a rotary motor 213 is arranged on the top of the
bonding tool support 210. The rotary motor 213 carries out a
rotation correction upon positioning of the electronic component
206. A load sensor 205 for detecting the pressing force of the
bonding tool 207 is arranged on the bonding tool support 210
beneath the cylinder 211.
[0075] The lifting and lowering block 212 is connected to a lifting
and lowering mechanism 218 which is comprised of a slide guide 215,
a feed screw 216, and a lifting and lowering motor 217 arranged on
the top of the feed screw 216, and the flat side wall of the
C-shaped lifting and lowering mechanism 212 is held by the feed
screw 216 via the slidable slide guide 215. The lifting and
lowering block 212 connected to the lifting and lowering mechanism
218 is allowed to move vertically, causing the bonding tool 207 to
move vertically accordingly.
[0076] A substrate 201 having connection terminals 201A formed
thereon is placed on a substrate attachment plate 202 that holds
the substrate 201 by vacuum. Under the substrate attachment plate
202, a substrate heater 203 for heating the substrate 201 and heat
insulating material 204 are provided.
[0077] After the signal from the load sensor 205 has been detected
by a pressure detection unit 220 and transmitted to a control unit
221, the control unit 221 controls a pressure adjustment unit 222,
causing the pressure detection unit 222 to adjust the flow rate of
a valve 223. In this way the pressing force of the bonding tool 207
is controlled.
[0078] Meanwhile, a conventional bonding apparatus shown in FIG.
10B includes a bonding head 300. The bonding head 300 is similar to
the bonding head 200 shown in FIG. 10A except that a load sensor
205 is arranged on a lifting and lowering block 212 beneath a
protruding part 210A of a bonding tool support 210.
[0079] Thus, in the conventional bonding apparatus shown in FIGS.
10A and 10B, there are many parts constituting the lifting and
lowering mechanism 218, bonding tool support 210, heating mechanism
208, etc. around the position where the load sensor 205 is
provided. For this reason, the load sensor 205 is susceptible to
heat generated due to friction of these parts; thus the load sensor
205 tends to produce varying values for the detected load.
Moreover, since such produced values merely indicate load acting on
the bonding tool 207 itself, the conventional bonding apparatus
cannot find during a bonding operation troubles (e.g., inclination
of the bonding tool, contamination of foreign material, variations
in the level of bumps, connection failures between substrate's
connection terminals, abnormal lifting and lowering of the bonding
tool, and wearing away and/or failure of the lifting and lowering
mechanism) like the foregoing bonding apparatus according to the
first embodiment. Accordingly, products obtained using such
conventional bonding apparatus are of less quality than those
obtained using the bonding apparatus according to the first
embodiment, resulting in reduced production yields.
[0080] According to the present invention it is possible to solve
the foregoing conventional problems and to provide a bonding
apparatus capable of increasing product quality by realizing
high-precision control of a pressing force applied upon mounting of
an electronic component on a substrate by bonding, and to a bonding
method capable of providing high-quality products stably.
[0081] The bonding apparatus of the present invention controls
pressing force with high precision when mounting an electronic
component on a substrate by bonding, thereby increasing product
quality. Moreover, when abnormalities have occurred, alarms can be
issued and/or the operation of the bonding apparatus can be halted,
thus ensuring the traceability of products for quality management.
For these reasons, the bonding apparatus of the present invention
can be suitably used for bonding of flash memories, DRAMs, and
FRAMs.
[0082] The bonding method of the present invention controls
pressing force with high precision to achieve stable mounting of an
electronic component on a substrate. Thus, with the bonding method
of the present invention, it is possible to provide high-quality
products with high yields without involving continued production of
defected pieces.
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