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CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
The present invention is related to three copending U.S. Patent
Applications. The first related application, Ser. No. 628,978, filed Dec.
12, 1990 with inventors E. Carnall, D. Freeman and J. Y. Kaukeinen, is
entitled "Techniques for Attaching Devices to Supports" and has a common
assignee with the present patent application. The second related
application, Ser. No. 702,877, which is being filed concurrently with the
present patent application, is entitled "Method and Apparatus for Curing
An Adhesive Interface", has a common assignee with the present patent
application and has as its inventors, E. Carnall and E. J. Ozimek., The
third related application, Ser. No. 702,867, which is being filed
concurrently with the present patent application, is entitled "Method and
Apparatus for Transferring Bonding Medium to Substrates", has a common
assignee with the present patent application and has as its inventors, E.
J. Ozimek, J. L. Suess and E. Carnall.
FIELD OF THE INVENTION
The present invention relates to an apparatus that controls assembly forces
during assembly of one object with another object.
BACKGROUND OF THE INVENTION
In manufacturing semiconductor devices and integrated circuits,
wafer-shaped or linear devices are commonly secured to a support, a
substrate or a package. Various techniques have been devised to bond or
cement such devices to a support, substrate or package.
U.S. Pat. No. 4,803,124 (R. Kunz), issued on Feb. 7, 1989, discloses a
technique for bonding semiconductor chips to a mounting surface utilizing
adhesive applied in starfish patterns. Kunz teaches depositing an adhesive
material in a starfish pattern comprising a raised central portion
disposed at the intersection of a plurality of radial arms. The bonding
surface of the semiconductor chip is pressed against the adhesive deposit
to cause the adhesive to uniformly and symmetrically spread therebeneath
across the bonding surface and bond the two surfaces. Kunz also describes
a prior art technique of placing five droplets of an adhesive in an "X"
shape on a support surface using five hypodermic needles.
Typically in these techniques, a silver-filled thermally polymerizable
conductive adhesive is disposed between the back surface of the device and
the front surface of the package or substrate. Most of these techniques
use a single continuous line of adhesive or a single row of spaced-apart
dots of adhesive disposed along the long axis of the device for attaching
the device to a support or substrate. The device is then placed on the
adhesive by some means and properly aligned. The adhesive is then
thermally cured to bond the device to the support or substrate.
Referring now to FIGS. 1 and 2, there is shown an exemplary arrangement of
the above-described technique which uses a single row of dots of adhesive
12. More particularly, FIG. 1 is a front view showing a portion of a
support, substrate or package 10, a dot of adhesive 12 (which is the first
dot of adhesive 12 of the single row of dots 12 formed therebehind)
disposed on the support or substrate 10, and a device 14 which has its
long axis centrally positioned on the peaks of the row of dots of adhesive
12. FIG. 2 is a top view of the exemplary arrangement of FIG. 1 showing a
non-continuous row of 16 dots of adhesive 12 (8 dots of adhesive 12 in
each section), but it is to be understood that such row of dots of
adhesive 12 could be continuous. It is to be further understood that for
the alternative technique using a single continuous line of adhesive (not
shown), the arrangement would look the same as the front view of FIG. 1,
and only a side view and the top view of FIG. 2 would appear different in
that the dots of adhesive 12 would be interconnected to form a continuous
line of adhesive.
Referring now to FIG. 3, there is shown a result which can occur after the
single row of dots of adhesive 12 of FIGS. 1 and 2 is thermally cured. As
is illustrated in FIGS. 1 and 3, as the dots of adhesive 12 heat up during
the curing process, the viscosity of the adhesive decreases and the
adhesive flows to allow the device 14 to move and/or tilt uncontrollably
depending on how the device 14 was positioned on the dots of adhesive 12.
A similar result can occur using the single line of adhesive.
Such techniques are suitable for applications which do not require precise
positioning of one or more devices 14 on the substrate or package 10.
However, for some applications, each device 14 has to be precisely placed
with a predetermined tolerance (e.g., at most .+-.15 microns) in the X and
Y directions and not shift to exceed such tolerance on the thermal curing
of the adhesive. As illustrated in FIGS. 1 and 3, the above-described
conventional techniques are not useful for providing such precise
positioning of the device 14 on the support, substrate or package 10.
Typically, when there is a need to assemble electronic devices (e.g.,
charge coupled integrated circuit chips) with high precision, the assembly
is performed using elaborate and expensive manual techniques assisted with
product-specific assembly fixtures. A need for product-specific fixtures
typically produces inordinately high assembly costs. Additionally, any
changes in product design are preceded by long lead times.
It has been a long sought after goal to provide a flexible and automated
system of assembling (attaching) electronic devices to substrates using a
bonding medium wherein the electronic devices are accurately located on
the substrates. To be practical, such a system needs to be adaptable to
the production of a wide range of product configurations. There are many
problems associated with developing such an automated assembly system. For
example, it is difficult to apply a bonding medium or adhesive to
substrates in a manner that provides sufficient uniformity of support for
the devices being assembled with the substrates.
Additionally, there is no known prior art way to automatically place a wide
variety of devices (IC's) onto an adhesive coating on a substrate. Prior
to curing the adhesive, the devices must be pressed onto the surface of
the adhesive to assure that there is no movement of the devices during
curing. The pressing of the devices onto the adhesive must be performed
with a very carefully controlled force, typically in the range of between
5 to 20 grams with a tolerance of .+-.0.05 grams. A force that is too high
causes the fragile devices to break. A force that is too low fails to
properly seat the devices onto the adhesive. Because the devices have
various thicknesses, it has been impractical to automatically control such
a force within the limits required for successful assembly of the devices.
In prior art assembly methods, the devices were placed onto the adhesive
coated substrates and the substrates were loaded into a high temperature
oven to cure the bonding medium or adhesive. In spite of the exercise of
extreme care in the formation of a uniform supporting base of adhesive and
placement of the devices onto desired locations, the assemblies emerged
from the oven with a slightly different positioning of the devices
relative to the substrates. The cause of this variation of positioning was
not fully understood, but it was assumed that the variations were caused
by some physical distortions of the adhesive that occurred during curing.
After a careful and more insightful examination of this problem, it has
been discovered that this undesirable phenomenon is a result of
environmental vibration (i.e., vibrations caused by movements of vehicles
and heavy objects in the vicinity of the curing operation or vibrations
from sources such as fans in a curing oven) which produces lateral
movement of the devices relative to the substrates while the adhesive is
in a fluid state. There has heretofore been no recognition that such
vibration is a problem.
It is desirable therefore to have an automated system for assembling
devices to substrates using a bonding medium (e.g., adhesive) which
results in the devices being accurately positioned and well secured to the
substrate. Furthermore, the desired system should be adaptable to the
production of a wide range of product configurations and produce high
yields.
SUMMARY OF THE INVENTION
The present invention is directed to an apparatus for assembling a first
object to a second object with a predetermined force. The apparatus
supports the first object and moves the second object relative to the
first object. A moving means has a driven member and a floating member
adapted to hold the second object. The driven member and the floating
member are coupled to each other with a deflecting member. The driven
member has a distance sensor coupled thereto which is adapted to measure a
displacement of the floating member relative to the driven member. The
sensor is coupled to a control means adapted to move the driven member to
place the second object into contact with the first object and then
continue the movement of the driven member until the sensor has measured a
predetermined displacement of the floating member relative to the driven
member.
Viewed from another aspect, the present invention is directed to an
apparatus for assembling a first object to a second object with a
predetermined force. The apparatus comprises means for supporting the
first object and means for moving the second object relative to the first
object. The moving means has a driven member and a floating member. The
driven member and the floating member are coupled to each other with a
deflecting member. The floating member is adapted to hold the second
object. The driven member has a distance sensor coupled thereto. The
distance sensor is adapted to measure a displacement of the floating
member relative to the driven member. The sensor is coupled to a control
means adapted to move the driven member to place the second object into
contact with the first object and continue the movement of the driven
member until the sensor has measured a predetermined displacement of the
floating member relative to the driven member.
Viewed from yet another aspect, the present invention is directed to an
apparatus for facilitating the bonding of a semiconductor device to a
substrate via an adhesive interface therebetween. The apparatus comprises
means for supporting the substrate and means for moving the semiconductor
device relative to the substrate. The moving means has a driven member and
a floating member. The driven member and the floating member are coupled
to each other with a deflecting member. The floating member is adapted to
hold the semiconductor device. The driven member has a distance sensor
coupled thereto. The distance sensor is adapted to measure a displacement
of the floating member relative to the driven member. The sensor is
coupled to a control means adapted to move the driven member to place the
semiconductor device into contact with an adhesive interface formed on the
substrate and continue the movement of the driven member until the sensor
has measured a predetermined displacement of the floating member relative
to the driven member.
The invention will be better understood from the following detailed
description taken in consideration with the accompanying drawings and
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a front view of a prior art arrangement of a support or substrate
with a device placed on the peak of a dot of adhesive which is the first
dot of a row of such dots formed therebehind;
FIG. 2 is an exemplary top view of the prior art arrangement of FIG. 1;
FIG. 3 is a front view of the prior art arrangement of FIG. 1 showing a
possible result after the adhesive dots have been thermally cured;
FIG. 4 is a front view of an arrangement of a support or substrate with a
device placed on the peaks of a first and a second dot of adhesive which
are the first dots of a first and second row of adhesive dots,
respectively, formed therebehind, which arrangement can be advantageously
produced with the present invention;
FIG. 5 is an exemplary top view of the arrangement of FIG. 4;
FIG. 6 is a front view of the arrangement of FIG. 4 showing the result
after the adhesive dots in both rows have been thermally cured;
FIG. 7 is a front view of an arrangement of a support or substrate with a
device mounted on the peak of a line of adhesive which is the first line
of a plurality of substantially parallel lines of adhesive formed
therebehind, which arrangement can be advantageously produced with the
present invention;
FIG. 8 is an exemplary top view of the arrangement of FIG. 7;
FIG. 9 is a front view of the arrangement of FIG. 7 showing the result
after the adhesive lines have been thermally cured;
FIG. 10 is a top view of an exemplary arrangement of a portion of a support
of substrate with three closely-spaced, side-by-side, staggered or
overlapping devices positioned on a combination of a row of dots of
adhesive and parallel lines of adhesive, which arrangement can be
advantageously produced with the present invention;
FIG. 11 is a schematic top view that shows symbolically an apparatus that
embodies certain force control features in accordance with the present
invention;
FIG. 12 is schematic view of an apparatus for curing an adhesive interface
between a device and a substrate after the device is placed on the
substrate in accordance with the present invention;
FIG. 13 shows an adhesive transfer tool of the apparatus of FIG. 11;
FIG. 14 is a detailed view of a portion of the adhesive transfer tool shown
in FIG. 13;
FIG. 15 is cross-sectional view of a portion of the apparatus of FIG. 11
taken along the dashed lines 15--15;
FIG. 16 is a view of the apparatus of FIG. 11 taken along the dashed line
16--16 during a first operation thereof;
FIG. 17 shows the same apparatus as FIG. 16, but during a second operation
thereof; and
FIG. 18 shows the same apparatus as FIG. 16, but during a third operation
thereof.
The drawings are not necessarily to scale.
DETAILED DESCRIPTION
The present invention is useful in the fabrication of assemblies of objects
such as those shown in FIGS. 4 through 10. These figures show arrangements
of devices and substrates which are disclosed and claimed in pending U.S.
patent application Ser. No. 628,978 which is cited in the Cross Reference
to Related Patent Applications section hereinabove.
Referring now to FIG. 4, there is shown a front view of an arrangement for
mounting a device 26 on a support or substrate 20. More particularly, the
arrangement of FIG. 4 comprises the support or substrate 20, a first and a
second dot of adhesive 22 and 24, respectively, which are the first dots
of a respective first and second row of dots of adhesive 22 and 24,
respectively, formed therebehind, and the device 26 which has long edges
29 thereof positioned parallel to the first and second rows of dots of
adhesive 22 and 24. For purposes of discussion hereinafter, it is assumed
that the device 26 is a rectangular or wafer-like device such as, for
example, a linear CCD sensor, with a planar surface that is positioned on
the peaks of the first and second row of dots of adhesive 22 and 24. The
first and second row of dots of adhesive 22 and 24 are preferably disposed
equidistant from a centerline 28 of the device.
In the context of the description of the present invention, one use of the
term "device" is to describe objects that are comprised of semiconductor
material in the form of die or chips on which are formed various
electrically functional elements (e.g., transistors, resistors, capacitors
and etc.). In this context, the term "device" is intended to describe a
semiconductor chip or die which has at least one and typically a plurality
of electrical elements.
Referring now to FIG. 5, there is shown an exemplary top view of the
arrangement of FIG. 4 with the first and second row of dots of adhesive 22
and 24 being non-continuous. It is to be understood that the first and
second row of dots of adhesive 22 and 24 can be continuous or
non-continuous to provide an arrangement which uniformly supports device
26. More particularly, in the arrangement of FIGS. 4 and 5, the first and
second rows of dots of adhesive 22 and 24, respectively, are disposed
substantially parallel to the long edges 29 of the rectangular or
wafer-like device 26 (as stated above), and are of near equal shape and
volume to cause the adhesive dots 22 and 24 to contact and uniformly
support the device 26 near the long edges 29 of the device 26.
Additionally, it is preferable that each row of the dots of adhesive 22
and 24 be positioned outwards from a centerline 28 of device 26 by an
equal amount.
Referring now to FIG. 6, there is shown a front view of the arrangement of
FIG. 4 showing the result after the first and second rows of dots of
adhesive 22 and 24 have been thermally cured. More particularly, during an
initial heating phase of a curing process, the viscosity of the adhesive
decreases, and the adhesive flows. When such dots of adhesive 22 and 24
have substantially an equal shape and volume, each dot of adhesive 22 and
24 flows downwards and outwards around the original pattern because the
device 26 is uniformly supported by each of the dots of adhesive 22 and
24. This arrangement of dots of adhesive 22 and 24 produces at most only
minute or negligible sideways forces in each of the flowing dots of
adhesive 22 and 24 as the adhesive polymerizes in a later phase of the
curing process. Therefore, the device 26 settles substantially straight
downwards and is prevented from shifting beyond an exemplary tolerance of
.+-.15 microns during the thermal adhesive polymerization process, thereby
providing precise positioning of the device 26. During the curing process,
the dots of adhesive 22 and 24 disposed near the long edges 29 of the
device 26 spread out from under and support the long edges 29 of the
device 26 as shown in FIG. 6.
It is to be understood that any suitable adhesive can be used, such as, for
example, a silver filled thermally polymerizable conductive adhesive such
as "Ablebond 84 1LMi" obtainable from the Ablestik Company. Such exemplary
adhesive is a thermally polymerizable silver filled epoxy which is both
thermally and electrically conductive.
Referring now to FIG. 7, there is shown a front view of another adhesive
pattern. In FIG. 7, a line of adhesive 30 is positioned substantially
perpendicular to the long edges 29 and centerline 28 of the exemplary
rectangular or wafer-shaped device 26. In the front view of FIG. 7, it is
to be understood that a plurality of similar substantially parallel
spaced-apart lines of adhesive 30 are formed behind the illustrated line
of adhesive 30. As shown in FIG. 7, each line of adhesive 30 has a length
which approximates the width of the device 20 to be positioned thereon to
uniformly support the device 26 therealong. It is to be understood that
the series of parallel spaced-apart lines of adhesive 30 may extend from
one end of the device 26 to the other end along its entire length, or over
one or more portions of the entire length as, for example, near the two
ends and the middle of the device 26.
Referring now to FIG. 8, there is shown an exemplary top view of the
arrangement of FIG. 7, wherein the lines of adhesive 30 are divided into
three sections where each end section is shown as comprising an exemplary
5 lines of adhesive 30, and the center section is shown as comprising an
exemplary 7 lines of adhesive 30. It is to be understood that the lines of
adhesive 30 can be continuous or non-continuous down the length of the
device 26, but the lines of adhesive 30 should form a pattern which
uniformly supports the device 26. Additionally, any number of lines of
adhesive 30 can be used for each section or over the continuous length,
and will usually comprise many more lines of adhesive 30 than shown in
FIG. 8.
Referring now to FIG. 9, there is shown a front view of the arrangement of
FIG. 7 illustrating the result after the lines of adhesive 30 of FIG. 7
have been thermally cured. As with the dots of adhesive 22 and 24 of FIGS.
4 and 6, the lines of adhesive 30 uniformly support the device 26 and
prevent the device 26 from shifting beyond the exemplary tolerance of, for
example, .+-.15 microns during the thermal polymerization process, thereby
providing precise positioning. More particularly, during the curing
process, the adhesive will first flow and then polymerize. When such lines
of adhesive have substantially an equal shape and volume, each line of
adhesive flows downwards and outwards around the original pattern because
the device 26 is uniformly supported by each of the lines of adhesive. In
other words, this arrangement will produce at most only minute or
negligible sideways forces in each of the flowing lines of adhesive as the
adhesive polymerizes. Therefore, the device 26 settles straight downwards
and is prevented from shifting beyond the exemplary tolerance of .+-.15
microns during the thermal adhesive polymerization process to provide
precise positioning.
Referring now to FIG. 10, there is shown a top view of a portion of a
support or substrate 40 on which a plurality (in this case three) of
devices 42a, 42b and 42c are positioned in a closely spaced, side-by-side
staggered (overlapping) exemplary arrangement. A single row of dots of
adhesive 44 (similar to that shown in FIG. 4) is used towards the ends of
the devices 42a, 42b, and 42c where the devices overlap each other (having
a portion of the device lying adjacent to another device). Additionally, a
plurality of lines of adhesive 46 (as described for FIGS. 7 and 8) are
used in the central area and towards the ends of devices 42a, 42b, and 42c
where the devices do not overlap each other. For example, the device 42a
uses a separate plurality of substantially parallel lines of adhesive 46
(which are substantially perpendicular to the long edge 48 of the device)
at the central area and the left end where the device 42a does not overlap
another device. At the end where device 42a overlaps the end of device
42b, each of the two devices 42a and 42b are shown as comprising a single
row of dots of adhesive 44 which are parallel to, and inside, the long
edge 48 of the device. Long edge 48 is disposed opposite the long edge 49
of the device that lies adjacent the corresponding long edge 49 of the
other device. A similar configuration of adhesive dots 44 and adhesive
lines 46 is used between overlapping and non-overlapping sections,
respectively, of the devices 42c and 42b. Since the first and second ends
of device 42b overlap and lie adjacent to the ends of devices 42a and 42c,
respectively, device 42b comprises a row of adhesive dots 44 at each of
the first and second ends, and parallel lines of adhesive 46 at the
central portion of device 42b where this device does not overlap another
device.
As described above, a single row of adhesive dots 44 is used at each end of
the device where that device overlaps another device. The reason for this
is that the device 42a, 42b or 42c must be supported at its end(s) because
that is where wire bonds are generally made between the device 42a, 42b,
and 42c and the associated external circuits. Additionally, the use of a
single row of adhesive dots 44 at the end(s) of the devices 42 (where the
end(s) overlap other devices) and within the boundary of the long edges 48
minimizes the amount of adhesive used and prevents the adhesive from
protruding beyond the outside dimensions of the device when the adhesive
is thermally polymerized.
Generally, the devices are positioned within 3-4 mils of each other in the
overlap regions, and if the adhesive squirts or flows out from under the
devices, the adhesive from one device could cause an adjacent device to
shift. It is to be understood that the illustration in FIG. 10 of six dots
of adhesive 44 at each overlapping end of devices 42a, 42b and 42c is
merely for purposes of exposition and not for purposes of limitation. At
each of these overlapping ends, there could be any number of dots of
adhesive 44 in a row as, for example, 30-35 dots. Similarly, it is to be
understood that the number of lines of adhesive 46 shown in FIG. 10 for
each section of devices 42a, 42b and 42c are merely for purposes of
illustration, and that any number of such lines of adhesive 46 can be used
that will uniformly cradle the associated device and prevent shifting
during thermal polymerization. Additionally, the lines of adhesive 46
could be disposed over the entire non-overlapping portions of each of
devices 42a , 42b, and 42c rather than under separate portions thereof,
but any arrangement can be used which will uniformly cradle each device
and prevent shifting of the device upon thermal polymerization of the
adhesive.
It can be seen from the preceding description that in the context of
applying devices to substrates, there is a need to form a wide variety of
precisely controlled patterns of bonding medium on substrates. In a
typical manufacturing operation, it is desirable to quickly change from
producing one type of product to another type of product. Such changes
often require a changing of the patterns of bonding medium that are
applied to the substrates. An apparatus for applying devices to substrates
that is readily adaptable to changes of product design is shown in FIG.
11.
Referring now to FIG. 11 there is shown schematically an apparatus 100 for
mounting devices onto substrates. The apparatus 100 has certain assembly
force control features which operate in accordance with the present
invention. The apparatus 100 comprises a first robotic unit (manipulator
or robot) 102, a second manipulator 104 (shown within a dashed line
rectangle), an adhesive source 106, a rack 108 for holding various tools
for the robot 102 and a pallet support 110.
The adhesive source 106 comprises a rotatable adhesive wheel 196, a support
stand 198, and an adjustable skimming blade 200. The adhesive wheel 196 is
provided with a raised lip 202 that forms a container for adhesive 203.
The skimming blade 200 is coupled to the support stand 198 with a
spring-loaded adjusting screw 204. The skimming blade 200 is also
supported with two guide pins 208. The adhesive source 106 is shown with
additional detail in a cross-sectional view taken through the dashed lines
15--15 in FIG. 15.
One example of a manipulator which is used in a preferred embodiment of the
apparatus 100 as the robot 102 is a Model Adept 2 Four Axis SCARA Robot
available from Adept Technology, Inc. An example of a manipulator which is
used in a preferred embodiment of the apparatus 100 as the manipulator 104
is a Three Stage Micropositioning Table available from Kensington Corp.
coupled with a Daedel Linear Stage/Compumotor Drive available from Daedel
Corp.
For illustrative purposes, the apparatus 100 is shown assembling the
devices 42a, 42b and 42c to the substrates 40 in the configuration shown
in FIG. 10. For purposes of simplicity, the devices are denoted
hereinbelow with the numeral 42 whenever there is no need to distinguish,
for example, the device 42a from the devices 42b and 42c.
The robot 102 comprises a base 112, first and second movable arms 114 and
116, respectively, a tool holder 118 and a camera 120. An operating axis
or end effector of the robot 102 is shown with two short crossed lines
that intersect at a point designated by a number 122.
The robot 102 operates by translating the point 122 to various locations on
the apparatus 100. When the point 122 is at a desired location, the tool
holder 118 is moved vertically to perform a desired function.
The manipulator 104 comprises an x-y stage 126, a rotatable stage 128, a
support beam 130, a die collet drive 132, a camera 140, and a pallet
support 142. The support beam 130 is coupled to the x-y stage 126. The die
collet drive 132 is coupled to the support beam 130. The rotatable stage
128 is positioned under the die collet drive 132. This arrangement allows
the die collet drive 132 to be moved, in an x-y plane, to various
locations above the rotatable stage 128. When the die collet drive 132 is
at a desired location, a die collet (not shown in FIG. 11 but shown in
FIGS. 16, 17 and 18) is moved vertically to perform a desired operation.
The rotatable stage 128 rotates the pallet support 142 under the die
collet drive 132.
In operation, the apparatus 100 performs assembly of the devices 42 to the
substrates 40 in response to programmed commands executed by the robot 102
and the manipulator 104. Initially, a pallet 150 containing a number of
the devices 42 and the substrates 40 is placed onto the pallet support 110
by an operator. The devices 42 and the substrates 40 are held in cavities
151 formed in the pallet 150. The apparatus 100 performs the desired
assembly without any further intervention or attention from the operator.
After the pallet 150 is in place, the robot 102 moves the point 122 to a
position over the tool rack 108. The tool holder 118 is lowered and
engages with an adhesive transfer tool 152. The robot 102 successively
moves the adhesive transfer tool 152 to a position over the adhesive
source 106 and then to various positions over the pallet 150. The adhesive
transfer tool 152 transfers a precisely controlled quantity or portion of
adhesive to desired locations on each of the substrates 40 during these
successive moves. A detailed description of the adhesive transfer process
is provided later hereinbelow.
After adhesive is applied to each of the substrates 40, the adhesive
transfer tool 152 is replaced in the tool rack 108. The tool holder 118
then engages with a conventional pallet transfer tool 154. The robot 102
then uses the pallet transfer tool 154 to move the pallet 150 from the
pallet support 110 to the pallet support 142 on the manipulator 104.
The manipulator 104 places the devices 42 onto the substrates 40. The
camera 140 is used to find an orientation of one of the substrates 40 with
respect to x and y axes of the x-y stage 126. The rotatable stage 128 is
rotated to align the substrate 40 with the x and y axes of the x-y stage
126. The die collet drive 132 is positioned, by movement of the x-y stage
126, over one of the devices 42 and the die collet (not shown) is engaged
with the device 42. The die collet is then positioned over a desired
location of the substrate 40, i.e., a location on which adhesive has been
applied. The device 42 is lowered onto the adhesive 203 at the desired
location. This process is repeated until all of the devices 42 are placed
on the substrates 40. A detailed description of the placement operation is
provided later hereinbelow.
After the placement process is completed, the pallet 150 is removed from
the apparatus 100 by an operator and placed in a curing apparatus 160
which is shown in FIG. 12.
We have found that vibrations produce a deleterious effect during curing of
the adhesive 203. If left uncontrolled, these vibrations cause relative
motion between the | | |
