U.S. patent application number 13/274116 was filed with the patent office on 2012-02-09 for ball mounting apparatus and method.
This patent application is currently assigned to ROKKO VENTURES PTE LTD. Invention is credited to Soo Loo Ang, Nee Seng Ling, Ter Siang Pai.
Application Number | 20120031954 13/274116 |
Document ID | / |
Family ID | 39430192 |
Filed Date | 2012-02-09 |
United States Patent
Application |
20120031954 |
Kind Code |
A1 |
Ling; Nee Seng ; et
al. |
February 9, 2012 |
Ball Mounting Apparatus and Method
Abstract
A device for mounting an array of solder balls to a plurality of
substrates of integrated circuits, comprising: a first plate for
receiving a first substrate in a loading position; said first plate
adapted to translate laterally from a substrate loading position to
a flux receiving position; said first plate further adapted to
rotate 180.degree. from the substrate loading position to a such
that the first plate is in a solder ball receiving position, and;
mounting solder halls to the first plate.
Inventors: |
Ling; Nee Seng; (Singapore,
SG) ; Ang; Soo Loo; (Singapore, SG) ; Pai; Ter
Siang; (Singapore, SG) |
Assignee: |
ROKKO VENTURES PTE LTD
Singapore
SG
|
Family ID: |
39430192 |
Appl. No.: |
13/274116 |
Filed: |
October 14, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12515900 |
May 21, 2009 |
8061583 |
|
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PCT/SG2007/000402 |
Nov 22, 2007 |
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13274116 |
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Current U.S.
Class: |
228/41 ; 228/33;
414/744.4 |
Current CPC
Class: |
H01L 21/4853 20130101;
H05K 3/3489 20130101; H05K 3/3478 20130101; H01L 2924/0002
20130101; H01L 2924/00 20130101; B23K 2101/40 20180801; H01L
2924/0002 20130101; B23K 3/0623 20130101 |
Class at
Publication: |
228/41 ; 228/33;
414/744.4 |
International
Class: |
B23K 3/06 20060101
B23K003/06; B65G 47/74 20060101 B65G047/74 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 22, 2006 |
SG |
200608015.4 |
May 7, 2007 |
SG |
200703231.1 |
Claims
1. A device for mounting an array of solder balls to a plurality of
substrates of integrated circuits, comprising: a first plate for
receiving a first substrate in a loading position; said first plate
adapted to subsequently translate laterally from a substrate
loading position to a flux receiving position; said first plate
further adapted to subsequently rotate 180.degree. from the
substrate loading position to a such that the first plate is in a
solder ball receiving position for mounting solder balls to the
first plate.
2. The device according to claim 1, further including: a second
plate, simultaneously rotatable with the first plate, such that the
first plate is in a ball receiving position, and the second plate
is in the loading position.
3. The device according to claim 1, wherein the flux receiving
position includes: a flux applicator adapted to sweep across a
surface at a pre-determined height; a flux template for pressing to
the surface, so as to pick up flux on the template and apply said
flux to the substrate in a pattern determined by the template.
4. The device according to claim 1, wherein the solder ball
receiving position includes: a ball template having vacuum
apertures in an orientation to match that required on the
substrate, said apertures adapted to receive the solder balls; a
ball suction tool arranged to be brought into proximity with the
template, such that the ball suction tool is capable of mounting
the solder balls to the substrate in the pre-determined orientation
of the ball template.
5. A rotary conveyor assembly comprising: a first and second
actuator, the first actuator arranged to move the second actuator
in a reciprocating motion; a rotary link adapted to rotate about a
rotational fixture and rotationally mounted to the second actuator
at a first end, such that the second actuator is arranged to move
the first end in a reciprocating motion; and said rotary link
having a conveyor mounting mounted adjacent to the first end.
6. The rotary conveyor assembly according to claim 5, wherein the
rotary link further includes a slide such that the conveyor
mounting to permit relative linear movement with the rotational
fixture.
7. The rotary conveyor assembly according to claim 5, wherein the
first and second actuator are arranged to interact such that the
conveyor mounting is capable of following a circular path.
8. The rotary conveyor assembly according to claim 7, wherein the
circular path followed by the conveyor mounting includes a first
point and a diametrically opposed second point.
9. The rotary conveyor assembly according to claim 8, wherein the
slide is arranged to diametrically extend the conveyor mounting
from the second point to a third point.
10. The rotary conveyor assembly according to claim 9, wherein the
slide is arranged to diametrically extend the conveyor mounting
from the first point to a fourth point.
11. The rotary conveyor assembly according to claim 6, wherein the
first end is mounted to the second actuator through a bracket in
direct engagement with the second actuator.
12. The rotary conveyor assembly according to claim 6, wherein the
second actuator is mounted to the first actuator through an
actuator plate mounted directly to the first actuator.
13. The rotary conveyor assembly according to claim 11, wherein on
actuation by the second actuator, the bracket is arranged to move
reciprocately along the actuator plate.
14. The rotary conveyor assembly according to claim 11, wherein the
first and second actuators are rotary actuators rotating the ball
screws, and respectively engage the actuator plate and bracket in a
screw thread arrangement, such that actuation of the rotary
actuators results in linear movement of the actuator plate and
bracket.
15. The rotary conveyor assembly according to claim 6, further
including a third actuator, the first actuator arranged to move the
third actuator in a reciprocating motion; the rotary link adapted
rotationally mounted to the third actuator at a second end, such
that the third actuator is arranged to move the second end in a
reciprocating motion; said rotary link having a second conveyor
mounting mounted adjacent to the second end.
16. The rotary conveyor assembly according to claim 15, wherein the
first actuator moves the second actuator along a first axis, and
the second actuator moves the first end along a second axis, said
first and second axes arranged orthogonal to each other.
17. A template assembly comprising; a template for receiving solder
balls; a reservoir housing for containing a plurality of solder
balls, said reservoir housing arranged to move over said template
and distribute the solder balls within said template; and a fluid
interface device for providing a fluid interface between the
template and reservoir housing.
18. The template assembly according to claim 17, wherein the
reservoir housing encapsulates a void into which the solder balls
are placed, said housing further including an orifice in an
underside face of said housing through which the solder balls are
distributed to the template.
19. The template assembly according to claim 17, wherein the fluid
interface maintains the reservoir housing at a predetermined
distance above said template.
20. The template assembly according to claim 17, wherein the fluid
of said fluid interface is air.
21. The template assembly according to claim 17, wherein the fluid
interface device is integral with the reservoir housing the fluid
interface device comprising an air inlet in communication with an
external air supply; a plurality of apertures in the underside face
through which the air exit to form the fluid interface said
apertures and inlet connected by at least one air channel.
22. The template assembly according to claim 21, wherein said
apertures are arranged in two groups, said groups located adjacent
to opposed ends of said underside face.
23. The template assembly according to claim 21, wherein said fluid
interface is located intermediate said apertures and a running
surface of said template.
24. The template assembly according to claim 17, wherein the
reservoir housing is mounted on a linear slide for moving the
reservoir housing along the template.
25. The template assembly according to claim 17, wherein said
underside face further includes two ridges separating a central
portion of the underside face from the apertures, such that a
central portion of the underside face is positioned above said
opposed ends during distribution of said solder balls.
26. A delivery device for delivery flux to a flux pool comprising;
a flux containment chamber; a first pressure source for applying
pressure to the contained flux within the containment chamber; an
exit chamber; a nozzle, such that under pressure flux moves from
the containment chamber through the exit chamber and exits the
nozzle; and wherein the exit chamber comprises a second pressure
source for applying pressure to flux within the exit chamber.
27. The device according to claim 26, wherein the flux containment
chamber includes a barrel of a syringe and the first pressure
source includes a selectively operable plunger arranged to slide
down the barrel so as to apply pressure to the flux within the
containment chamber.
28. The device according to claim 26, wherein the second pressure
source comprises an inlet in communication with a pressurized air
source such that on activation of the second pressure source,
pressurized air is applied to flux in the exit chamber to force
said flux from the exit chamber and out of said nozzle.
29. A device according to claim 26, further including a sensor for
sensing a quantity of flux within the barrel such that on reaching
a predetermined minimum quantity, the sensor will output a signal
to prompt an operator to remove said barrel.
30. An adaptor plate assembly for mounting a pick up head to a
solder ball placement machine, the adaptor plate comprising; a
plate having a central orifice; a resilient engagement portion
having a plurality of resilient depressible projections located on
a peripheral edge of said plate for resiliently engaging
corresponding recesses in the solder ball placement machines; a
plurality of location holes on a first face of said plate arranged
to correspond with projections from the pick up head; and
engagement portions for releaseably engaging the pick up head.
31. The adaptor plate according to claim 30 wherein further
including an inlet on one face and an outlet on an opposed second
face having channels connecting said inlet and outlet so as to pass
a vacuum through said plate.
32. The adaptor plate according to claim 30, further including
steel bushings for insertion in the location holes.
33. The adaptor plate according to claim 30, wherein said plate is
made from aluminum.
34. The adaptor plate according to claim 30, wherein said plate is
adapted to be press fit into engagement with said solder ball
placement machine using said resilient projections.
35. The adaptor plate according to claim 32, wherein said bushings
include centrally placed apertures, said apertures sized so as to
correspond to projections from said solder ball placement
machine.
36. The adaptor plate according to claim 30, wherein said pick up
head is one of a solder ball pick up head or a flux pick up head.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/515,900, filed May 21, 2009, which is a 371
National Phase entry of Application PCT/SG2007/000402, filed Nov.
22, 2007, further claiming priority to Singapore Application No.
200703231.1 filed May 7, 2007 and Singapore Application No.
20060815.4 filed Nov. 22, 2006, all of which are incorporated
herein by reference, together with any and all attachments and
exhibits thereto. The full benefit and priority of all applications
are claimed.
BACKGROUND OF THE INVENTION
[0002] The invention relates to ball grid arrays and more
particularly the placement of solder balls in such arrays placed
upon substrates prior to dicing.
[0003] Ball grid arrays are arrays for receiving solder balls which
are used as electrodes for connection to integrated circuits. They
are placed whilst the integrated circuit is still within a
substrate prior to or after dicing of said substrate.
[0004] The substrate, in general terms, is passed into a flux
deposition platform and then to a ball mounting platform where upon
the balls are mounted within the flux in precisely located
arrangements.
[0005] Solder Ball Placement Machines are employed to attach the
solder balls within the area-array package substrates where they
form the final interconnection to the substrate. The Solder Ball
Placement Machine performs two main processes, which are flux
deposit on the substrate, followed by solder balls placement on the
substrate. Flux is used to remove oxidation on the solder pad for
better connectivity and bonding, and to hold the solder ball in
place before the substrate is sent to the reflow oven to melt the
solder ball to complete the bonding.
[0006] In one method, the flux and solder balls processing regions
are located in series whereby the substrate is passed within the
flux processing region so that flux is applied to the array.
Subsequently the substrate is passed to the ball mounting platform
whereby a ball robot places the solder balls in a precise
benchmark. The substrate is subsequently passed out of the ball
mounting apparatus and subsequently sent for dicing.
[0007] For this arrangement, fiducial vision of the substrate on
each platform is taken so as to locate the position and orientation
of the substrate and so precisely place both the flux and solder
balls.
[0008] A flaw in this method, however, is the need to take two
separate set of fiducial vision of the substrate on the two
separate platforms. This will worsen the bottle neck at the ball
mounting station as the ball pick head being the apparatus for
placing the balls must first determined whether the head is fully
laden with balls such that there are none missing from the cavity
used for placing the balls and subsequently checked that all balls
were deposited from the head and no particular cavity still having
a ball jammed within the head and so not transferred to the array.
This double inspection system controls the flow of substrates
through the ball mounting device and can consequently miss the
overall speed of this process.
[0009] In a different arrangement, the flux and ball mounting
regions are placed parallel to each other such that the substrate
is passed into the device and the flux positioning head and ball
pick head positioned to access the substrate without having to move
the substrate from one station to the next. In this way, the
fiducial vision of the substrate to ensure orientation and position
of the substrate is correct, need only be taken once and not
separately at the flux region and ball region, so consequently for
this reason will be a faster process compared to the previous.
However, the limitation of this arrangement is that the single
platform can only be worked on by the Flux or the Ball Head at one
time and either one will be idle, so the benefit of a single
fiducial vision check is wasted as the bottle neck is now at the
single mounting platform and it causes an increase in the machine
cycle time.
[0010] In another facet of the process, the flux pool generally
comprises a pair of sweeping flux applicators mounted on a linear
slide and arranged to travel backward and forward over a supply of
flux deposited on a plate. The flux applicator, during the sweeping
motion forms a layer of flux at a pre-determined thickness as
controlled by the height of the flux applicator. The sweeping
action is driven by a speed control motor and often including a
pair of pneumatic actuators.
[0011] During sweeping, one flux applicator will be in a lowered
position at the fixed height from the flux pool to form the
predetermined flux thickness. The thickness of flux on the plate
will control the amount of flux taken by a flux tool which then
applies the controlled amount of flux to a substrate. As a means of
ensuring the flux pool has a sufficient supply, there is a sensor
which measures the level of flux in the flux pool that on reaching
a lower limit, which activates a flux refiller to add new flux to
the flux pool.
[0012] The flux refiller typically comprises a syringe subjected to
an external air supply so as to apply pressure to the plunger of
the syringe and consequently inject the flux into the flux
pool.
[0013] Whilst there are variations known in the industry many
typically have similar arrangements including the use of a syringe
in order to inject flux into the flux pool. Accordingly, these
suffer the problem of syringes generally in that not all the
contents of the syringe can be completely removed. Instead a "slug"
or "tailing" of the flux remains in the exit chamber preceding the
nozzle of the syringe. This remaining flux may be partially exposed
to the external environment and therefore, can become contaminated
on the next usage of the syringe. Further, whilst the flux is
viscous, it can still drip from the nozzle and so the tailing
remaining in the nozzle may drip and so place flux on the
peripheral elements of the flux pool. Accordingly the flux that
contacts areas outside the flux pool may further become
contaminated and if then inadvertently added to the flux pool can
cause contamination to the entire flux pool.
[0014] This may also result in contamination that may spread to
subsequent substrates, contaminating an entire batch of substrates
to which the solder balls are being attached.
[0015] In a further facet, once the flux is applied to the
substrate, solder balls are then mounted to the flux for further
processing. The arrangement of the solder balls on to the substrate
requires a very precise arrangement to a very high tolerance.
[0016] Templates are used as a means of establishing a
predetermined array for the batch process of placing small scale
units such as solder balls for down stream manufacturing
purposes.
[0017] The time consuming activity of placing the solder balls
within the highly defined arrays is one that can be alleviated by
automating their placement of the units within said arrays. One
such method involves pouring the solder balls into the templates
for a gravity placement of the arrays. It follows that this method
would be extremely inaccurate. Another such method involves
sweeping a reservoir of solder balls across the template so as to
maintain a more precise correspondence with the array through
maintaining a pre-determined gap between the reservoir and the
array. The maintenance of this very precise gap has led to a high
quality in output and less wastage through misplacement of solder
balls within the array.
[0018] The difficulty with this approach is the level of tolerance
required to maintain the gap. It is necessary to establish a datum
from which to measure the gap and for the mechanical system
required for distribution of the solder balls to the array. Fixed
points relative to the reservoir such as a base plate underlying
the template or a linear slide to which the reservoir is mounted so
as to distribute the balls are logical places to establish the
datum. The precision requires a high degree of machining which adds
to the manufacturing costs of the device. Further poor linearity of
the linear slide or warpage of the base plate must be avoided to
maintain the precision required.
[0019] Without maintaining a high precision for the gap, it is very
difficult to accurately distribute the solder balls particularly as
a template may require an array having a planar area of 300
rnm.times.90 mm. The degree of flatness required over such an area
represents a significant manufacturing cost for the equipment.
[0020] Further, even if the machining is maintained to a very high
tolerance, the installation of various components including the
template will also require a high degree of quality. If the
template is not precisely fitted to the device, then even a
manufacture of high tolerance will not overcome the shortcomings of
a poor installation.
BRIEF SUMMARY OF THE INVENTION
[0021] Therefore, in a first aspect, the invention provides a
method of mounting an array of solder balls to a plurality of
substrates of integrated circuits, comprising the steps of:
delivering a first substrate to a first plate in a loading
position; laterally translating the first plate to a flux receiving
position; applying flux to said first substrate; returning said
plate to the loading position; rotating the first plate 180.degree.
such that the first plate is in a solder ball receiving position,
and; mounting solder balls to the first plate.
[0022] In a second aspect, the invention provides a device for
mounting an array of solder balls to a plurality of substrates of
integrated circuits, comprising: a first plate for receiving a
first substrate in a loading position; said first plate adapted to
translate laterally from a substrate loading position to a flux
receiving position; said first plate further adapted to rotate
180.degree. from the substrate loading position to a such that the
first plate is in a solder ball receiving position, and; mounting
solder balls to the first plate.
[0023] In a third aspect, the invention provides a rotary conveyor
assembly comprising a first and second actuator, the first actuator
arranged to move the second actuator in a reciprocating motion; a
rotary link adapted to rotate about a rotational fixture and
rotationally mounted to the second actuator at a first end, such
that the second actuator is arranged to move the first end in a
reciprocating motion; said rotary link having a conveyor mounting
mounted adjacent to the first end.
[0024] In a fourth aspect the invention provides a template
assembly comprising; a template for receiving solder balls; a
reservoir housing for containing a plurality of solder balls, said
reservoir housing arranged to move over said template and
distribute the solder balls within said template and; a fluid
interface device for providing a fluid interface between the
template and reservoir housing.
[0025] In a fifth aspect the invention provides a delivery device
for delivery flux to a flux pool comprising; a flux containment
chamber; a first pressure source for applying pressure to the
contained flux within the containment chamber; an exit chamber and
a nozzle, such that under pressure flux moves from the containment
chamber through the exit chamber and exits the nozzle; wherein the
exit chamber comprises a second pressure source for applying
pressure to flux within the exit chamber.
[0026] In a sixth aspect, the invention provides an adaptor plate
assembly for mounting a pick up head to a solder ball placement
machine, the adaptor plate comprising; a plate having a central
orifice; a resilient engagement portion having a plurality of
resilient depressible projections located on a peripheral edge of
said plate for resiliently engaging corresponding recesses in the
solder ball placement machines; a plurality of location holes on a
first face of said plate arranged to correspond with projections
from the pick up head, and engagement portions for releaseably
engaging the pick up head.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
[0027] It will be convenient to further describe the present
invention with respect to the accompanying drawings that illustrate
possible arrangements of the invention. Other arrangements of the
invention are possible, and consequently the particularity of the
accompanying drawings is not to be understood as superseding the
generality of the preceding description of the invention.
[0028] FIG. 1A is a plan view of a substrate processing device
according to one embodiment of the present invention.
[0029] FIG. 1B is a plan view of a ball mounting device according
to one embodiment of the present invention;
[0030] FIG. 2 is a detail view of the ball mounting device of FIG.
1B.
[0031] FIG. 3 is an isometric view of the ball mounting device of
FIG. 2.
[0032] FIG. 4 is a flow chart of a ball positioning process
according to one embodiment of the present invention.
[0033] FIG. 5 is a flow chart of a flux depositing process
according to one embodiment of the present invention.
[0034] FIG. 6 is a flow chart of a ball mounting process according
to one embodiment of the present invention.
[0035] FIGS. 7A to 7J are sequential plan views of a twin conveyor
in the process of mounting solder balls to a plurality of
substrates according to one embodiment of the present
invention.
[0036] FIG. 8 is a plan view of a rotary conveyor assembly
according one embodiment of the present invention.
[0037] FIGS. 9A to 9G are sequential plan views of movement of the
rotary conveyor of FIG. 8.
[0038] FIG. 10A is an isometric view of a solder ball preparation
module according to a further embodiment of the present
invention.
[0039] FIG. 10B is an isometric reverse view of the solder ball
preparation module of FIG. 10A.
[0040] FIG. 10C is an isometric underside view of the solder ball
preparation module of FIG. 10A.
[0041] FIGS. 11A to 11C are various views of the solder ball
reservoir according to a further embodiment of the present
invention.
[0042] FIGS. 12A and 12B are isometric views of an adaptor plate
according to a further embodiment of the present invention.
[0043] FIGS. 13A and 13B are isometric views of an adaptor plate
according to a further embodiment of the present invention.
[0044] FIG. 14 is an elevation view of the operation of a flux
refiner of the prior art.
[0045] FIG. 15 is an elevation cross sectional view of the flux
refiller according to a further embodiment of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0046] FIG. 1 shows an overview of a substrate processing device 1
comprising a ball mounting device 5, a re-flow & washer machine
10 immediately downstream from the ball mounting device 5, a
collector 15 and a magazine unloader 20. The substrate processing
device is used to process substrates, and specifically those that
comprise integrated circuits (IC) with ball grid arrays (BGA)
whereby solder balls are mounted to the IC's to form said
arrays.
[0047] The invention relates to the ball mounting device 5, one
embodiment of which is shown in FIGS. 1B, 2 and 3. At the upstream
end of the ball mounting device 5 is the magazine loader 25.
Typically, the loader 25 comprises an upper stage, lower stage,
magazine clamp and pusher, which for clarity of the overall process
are not shown. The upper stage is where magazines or cassettes
loaded with substrates are inserted, prior to the mounting of the
solder balls. A rubber belt, driven by rollers and an induction
motor moves the loaded magazine towards the magazine clamp. The
magazine clamp picks up the magazine and indexes the first
substrates to the input conveyor 40.
[0048] Individual substrates are pushed one at a time into the
input conveyor 40 when the magazine clamp index each substrates to
the conveyor. Once all the substrates have been pushed out, the
magazine clamp will place the empty magazine on the lower stage
where the empty magazines are removed by the operator.
[0049] Input conveyor 40 comprises a pair of guide rails 41A, B,
driving belts driven by an induction motor, inlet rollers, cleaning
brush & vacuum module, orientation check sensor and substrate
pusher, all of which combine to move the substrates through to the
flux and ball mounting region.
[0050] The width of the guide rails 41A, B is adjustable by a
stepper motor with feedback so as to conform to the width of the
substrate that is keyed into the product recipe during initial
setup. The inlet roller feeds each substrate into the rails 41A, B
from the magazine with the driving belts on the rails carrying the
substrate forward until it reaches a stopper. A sensor detects the
presence of a substrate at the stopper whereby an orientation
sensor will check for the correct orientation of the substrate at
this position.
[0051] The stopper is driven by an air cylinder in an up/down
motion to selectively permit or prevent movement of the substrate.
There is also a cleaning brush & vacuum module along the input
conveyor 40 to clean the substrate.
[0052] When the substrate is ready to be sent downstream, the input
conveyor 40 moves towards the flux/ball mounting region 30, to
close the gap between itself and the R-Y Twin Conveyor 65, located
in the region 30. The initial gap is necessary to avoid
interference with the rotation of the R-Y Twin Conveyor 65 once
loading has taken place.
[0053] The process continues with the stopper retracting and the
substrate pushed by the substrate pusher into one of the R-Y Twin
conveyor 65 nearer to the flux robot 45 until the substrate reaches
the stopper in the R-Y Twin conveyor 65. The substrate pusher
horizontal X motion is driven by a stepper motor with feedback and
the up/down motion is driven by an air cylinder.
[0054] The fiducial vision comprises two sets of cameras, optics
and lightings mounted on two individual X-Y slides. It registers
the actual substrate location in the twin conveyor 65 when the
substrate is loaded as there is still some free play between the
locating holes of substrate and the location pins. The machine
system automatically provides an offset to the initial placement
location base on the current substrate location. This provides a
more consistent placement of flux and solders balls on the
substrate.
[0055] In this embodiment, the R-Y Robot and Twin Conveyor 65
comprises two linear slides 80, 85, a rotatable twin conveyor 70,
75, rotation linkage mechanism 67, substrate pusher, substrate
lifter and top plate. The twin conveyors 70, 75 are mounted
separately on the two linear slides 80, 85 driven by two servo
motors which the two conveyors 70, 75 are able to move in Y
direction independent of each other and the twin conveyors 70, 75
can rotate together by the use of rotation linkages mechanism
driven by servo motor.
[0056] The process implemented by the apparatus according to this
embodiment is shown in set of conveyor pushers mounted on each of
the conveyors. When a new substrate 235 is loaded, the conveyor
pusher acts as a stopper with the stop position arranged such that
the substrate location holes coincide with the top plate locating
pins. The conveyor pushers are driven by stepper motor with
feedback.
[0057] When the substrate is being lifted up by the substrate
lifter to locate on the top plate, the conveyor pusher returns to
its push position. The top plate has two locating pins which will
precisely locate the substrate. Alternatively, the substrate is
held by the lifter using a vacuum without the use of top plate. The
fiducial vision registers the current substrate location. Next, the
conveyor 236 will then move to the Flux Robot position 245 for flux
to be deposited on the substrate.
[0058] The use of flux is to remove oxidation on the solder pad for
better connectivity and bonding, and to hold the solder ball in
place before the substrate is sent to the reflow oven to melt the
solder ball to complete the bonding.
[0059] After the flux is deposited, and the conveyor returned to
the central position, the twin conveyor will rotate 1800 to bring
the conveyor with flux nearer to the Ball Robot 250. The Ball Robot
will then place the solder balls on the solder pad held in place by
flux.
[0060] When the ball is being placed, the other conveyor of the
Twin Conveyor is loaded with a new substrate 242 and flux is being
placed by the Flux Robot 245. The conveyor then returns to the
central position, and the twin conveyor rotates 1800 again to bring
the conveyor with the substrate with solder balls to align to the
Input Conveyor and After Mount Inspection Conveyor.
[0061] The After Mount Inspection Conveyor will then move to the
left to close up the gap between itself and the Twin Conveyor. The
Conveyor Pusher pushes the substrate out into the After Mount
Inspection Conveyor and stop at the stopper position to stop the
new substrate pushed in by the substrate pusher at the Input
Conveyor. The whole process then repeats itself for the subsequent
substrates loaded to the conveyor.
[0062] FIG. 5 shows a flow path for the flux deposition method. The
Flux Pool comprises a pair of sweeping flux applicators mounted on
linear slide. The flux applicator will form a layer of flux which
has predetermined thickness by setting the height of the
applicator. The sweeping action 150 is driven by using speed
control motor and the up/down motion is driven by a pair of air
cylinders. During sweeping 150, one of the flux applicator will be
at the down position at a fixed height from the flux pool to form a
layer of flux with a certain thickness. This flux thickness
controls the amount of flux pick up 155 by the Flux Tool and the
subsequent amount of flux applied on the substrate 160.
[0063] The Flux Robot comprises X & Z slides and a Flux Process
Head, which is mounted on the X & Z slides driven by two
servomotors moving in the X direction and the Z direction. The Flux
Process Head can rotate horizontally to compensate for theta error
with the substrate and is also driven by a servomotor. The Flux
Robot is mounted on a gantry for stable operation, with the Flux
Process Head carrying the Flux Tool to pick up flux from the Flux
Pool and deposit the flux on the solder pad of the substrate held
in the R-Y twin conveyor.
[0064] The pattern of array of the Flux Tool corresponds to the
pattern of the array of the solder pad on the substrate. The Flux
Tool can be easy removable for converting to other product of
substrate and for washing and maintenance. It comprises pins which
are retractable so as to compensate for any warpage of the
substrate and to ensure all the pins contact the solder pad to
transfer flux to the solder pad. The retractable mechanism works by
using either springs or sponge type material.
[0065] As shown in the flow chart of FIG. 4, the Ball Pool
comprises a solder ball container mounted on linear slide driven by
speed control motor and a Ball Refill Module. The Ball Pool module
is mounted on slides, which can move in Y direction driven by
stepper motor with feedback. This allows fine adjustment to match
the Ball Template to the Ball Suction Tool in Y direction. The
solder ball container has an opened base where the solder balls
will contact with a Ball Template 110. The Ball Template has vacuum
apertures patterned in the same array as the solder pad in the
substrate.
[0066] The vacuum apertures of the Ball Template will retain solder
balls which will be picked up by the Ball Suction Tool 115. The
Ball Template is easy removable for conversion of different product
of substrate. The Ball Refill Module has a storage compartment for
solder balls and it supply solder balls to the ball container for
prolong operation without the assist of operator.
[0067] The Ball Robot 50 comprises X & Z slides and a Ball
Process Head, which is mounted on X & Z slides driven by two
servomotors moving in the X direction and Z direction. The Ball
Process Head can rotate horizontally to compensate for theta error
with the substrate and Ball Template and it is driven by
servomotor. The Ball Robot 50 is mounted on a gantry for stable
operation, and supporting the Ball Process Head which carries the
Ball Suction Tool, having vacuum apertures patterned in the same
array as the solder pads in the substrate.
[0068] The Ball Suction Tool may be removable for converting to
other product of substrate. It picks solder balls by vacuum from
the ball pool 115, move to Missing ball Inspection 120 and finally
deposits the solder balls 125 on the solder pads of the substrate
held in the R-Y twin conveyor.
[0069] After placing the solder balls on the substrate 125, the
Ball Process Head will carry the suction tool to Stuck Ball
Inspection 135. Both the Missing ball Inspection 120 and Stuck Ball
Inspection 135 are in the path of picking and placing of solder
balls which will reduce cycle time of the inspection.
[0070] The Missing Ball Inspection comprises an Infra-red emitter
and an Infra-red receiver. The infra-red emitter is mounted in the
Ball Process Head while the infra-red receiver is mounted in the
path of the Ball Process Head from the Ball Pool to the R-Y
Conveyor. Alternatively, the infra-red receiver may be mounted in
the Ball Process Head while the infra-red emitter is mounted in the
path of the Ball Process Head from the Ball Pool to the R-Y
Conveyor.
[0071] After the Ball Process Head has picked up the solder balls
from the Ball Template on the Ball Pool, it will pass through the
infra-red emitter or receiver. If there is no missing ball, the
infra-red will not pass through the vacuum apertures and the
infra-red receiver will registered nominal voltage, the machine
system will show that missing ball inspection has passed. If there
is any missing ball, the infra-red will pass through the vacuum
apertures and the infra-red receiver will registered higher
voltage, the machine system will show that missing ball is detected
and the system will dump the solder balls and check for stuck balls
before re-picking the solder balls. If after re-pick, there are
still missing balls, the machine system will prompt for operator
assistance.
[0072] The Stuck Ball Inspection comprises a pair of laser emitter
and laser receiver mounted horizontally in the path of the Ball
Process Head from the R-Y Conveyor to the Ball Pool. After the Ball
Suction Tool had placed the solder balls on the substrate, the Ball
Process Head will carry the Suction Tool through the laser beam at
a predetermine height. If there is a solder ball stuck on the
suction tool, the laser beam will be partially blocked and the
reading of the laser receiver will show a weaker strength of the
laser beam and output a signal that stuck ball is detected on the
Ball Suction tool.
[0073] The Suction Tool will try to dump the stuck solder ball in
the Dump Bin 140 and re-inspect the suction tool again, if stuck
ball is still detected, the system will stop and prompt for
operator to assist. If there is no solder ball stuck on the Suction
Tool, there will be no change in the reading of the laser receiver
and the machine system will show that stuck ball inspection has
passed.
[0074] The After Mount Inspection 31 (AMI) comprises a camera 105
with low angle ring light 100 mounted stationary. The camera is a
line scan camera which will capture an image of an object while on
the fly and the object position is feed back to the vision system
by a linear encoder. The line scan camera has an advantage where it
can capture large image at one time which is much faster than a
normal area scan camera which need to take a few shots of the large
object. The camera will capture the image of the substrate when it
scan the substrate position by the linear encoder while the
substrate is being moved along under the camera with the low angle
ring light switched on. The vision inspection will check for
missing balls, extra balls, ball diameter, ball pitch and ball to
pad distance.
[0075] The After Mount Inspection Conveyor comprises a pair of
guide rails with driving belts, substrate lifter and process top
plate mounted on linear slide driven by speed control motor. The
width of the guide rails is adjustable by stepper motor with
feedback and it corresponds to the width of the substrate that is
keyed into the product recipe during initial setup. Before the
substrate is pushed into the AMI 31 conveyor from the R-Y conveyor,
AMI Conveyor will move towards the left to close up the gap between
itself and the R-Y Twin Conveyor. The gap is necessary to avoid
interference with the rotation of the R-Y Twin Conveyor.
[0076] On the AMI conveyor, the substrate will he lift up by the
substrate lifter to locate on top plate. The top plate will move
under the line scan camera for image capturing. The top plate is
connected to a linear encoder to feedback the position of the
substrate while the camera is capturing the image. After vision
capturing, the substrate will be lower on the conveyor and the
driving belts will move the substrate downstream to the Multi Lane
Distributor 35.
[0077] The Multi Lane Distributor 35 comprises a pair of guide
rails with driving belts and substrate pusher, which is mounted on
a linear slide driven by stepper motor with feedback. The width of
the guide rails is adjustable by a stepper motor with feedback and
it corresponds to the width of the substrate that is keyed into the
product recipe during initial setup. After vision inspection, the
passed substrate will be sent downstream to the Reflow Oven while
the failed substrate will he send to the Reject Module 32.
[0078] The Reflow Oven comprises a slow moving broad metal chain
conveyor that carry the substrates through the different heating
and cooling zone of the oven. The Multi Lane Distributor will
spread the substrate on the broad conveyor of the Reflow Oven by
indexing substrate to different position lane on the conveyor.
Typically, depending on the width of the substrate, 3 to 5 lanes
are used to spread the substrates evenly on the conveyor of the
reflow oven. The rejected substrate is then transferred to the
Reject Module 32 for the operator to rework.
[0079] Additional features that may be added to the apparatus and
process include: [0080] a Reflow Oven for melting the solder ball
to complete the bonding to the solder pad; [0081] a Washer Machine
to wash and dry the substrates to remove flux and any contaminants;
[0082] Offloader, which comprises a Nestling Conveyor, Multi Lane
Consolidator, Offload Conveyor, Buffer Bin and Magazine
Handler.
[0083] The Nestling Conveyor comprises a set of rollers in 3 to 5
lanes depending on the machine. The substrates will be stopped by
the stopper in each lane until the Multi lane consolidator is
indexed to the lane and the stopper is lowered to allow the
substrate to be transferred over.
[0084] The Multi Lane Consolidator comprises a pair of guide rails
with driving belts, which is mounted on a linear slide driven by
stepper motor with feedback. The width of the guide rails is
adjustable by stepper motor with feedback and it corresponds to the
width of the substrate that is keyed into the product recipe during
initial setup. The Multi Lane Consolidator will receive the
substrates from the different lane of the Nestling conveyor by
indexing to the individual lanes.
[0085] After receiving the substrate, it will index to the Offload
conveyor and the stopper is lowered to allow the substrate to
transfer over to the Offload conveyor.
[0086] The Buffer Bin comprises a metal tray for the collection of
substrates when there is no empty magazine or an error has occurred
at the Magazine Handler. The purpose of the Buffer Bin is to
prevent jam up at the Nestling Conveyor as the conveyor of the
Reflow Oven and the Washer Machine will continuously feed
substrates to the Nestling Conveyor.
[0087] The Offload Conveyor comprises a pair of guide rails with
driving belts and substrate offload pusher. The width of the guide
rails is adjustable by stepper motor with feedback and it
corresponds to the width of the substrate that is keyed into the
product recipe during initial setup. The Offload Conveyor receives
the substrate from the Multi lane consolidator and then sends it to
the magazine by the offload pusher.
[0088] The Magazine Unloader comprises an upper stage, lower stage
and magazine clamp. The Upper stage is where empty magazines or
cassettes are inserted. The rubber belt driven by the rollers and
motor will move the empty magazine towards the magazine clamp. The
magazine clamp will then pick up the magazine and index first
substrate slot to the Offload Conveyor.
[0089] The Offload Pusher pushes the substrate into first substrate
slot in the magazine. The magazine clamp will then index to the
next substrate slot. This process repeat until the magazine is
full. Once the magazine is full, the magazine clamp will place the
full magazine on the lower stage where the full magazines can be
removed by the operator.
[0090] Referring to FIGS. 8 and 9A to 9G, there is shown a rotary
conveyor 260 for selectively moving an object through a combination
of translation and rotation. Whilst applicable to the device and
method described above, the rotary conveyor 260 is also applicable
to a range of applications distinct from the solder ball device of
the present invention. In this sense, the device will be described
separately from the aforementioned device and method. It will,
nevertheless, be understood by the skilled addressee that the
rotary conveyor 260 according to this aspect of the invention will
fulfil the requirements of the conveyor 65 as previously
described.
[0091] FIG. 8 shows one half of the total rotary conveyor assembly,
omitting the other half for clarity. It will be appreciated the
following discussion is applicable to the second half, which act
together to provide the efficiencies of the overall assembly
260.
[0092] The rotary conveyor assembly 260 according to this
embodiment comprises a rotary link 270 which rotates about a fixed
point 330. The rotary link 270 further includes a slide 280 upon
which is located a conveyor mounting 310. When the assembly 260 is
applied to the solder ball mounting device and method, the conveyor
mounting is adapted to receive and transport substrates. Otherwise,
the conveyor mounting 310 will be applicable to the engagement of
other objects according to the intended use.
[0093] The conveyor mounting 310 is placed adjacent a first end 290
of the slide 280, which is also adjacent to the rotary conveyor's
engagement with a bracket 400 of an actuator 360 aligned with the Y
axis. The centre point 320 of the conveyor mounting 310 defines a
floating point through which motion of the rotary link 270 may be
described. In particular, and as will be described below, the
movement of the floating point 320 defines a circular path 335, in
this embodiment. It will be appreciated that, in arrangements
falling within the scope of the invention, that the path 335 may
define a range of different shapes according to the desired
application.
[0094] Not shown is an identical conveyor mounting which may be
positioned at the opposed end 300 on another set of slides, which
in turn would be engaged with a similar actuator (not shown).
[0095] The Y-actuator 360 biases the rotary link 270 through a
screw thread arrangement, whereby a ball screw 370, within a base
plate 380, is rotated by the Y-actuator 360. The bracket to which
the rotary link 270 is mounted engages the ball screw 370 through a
corresponding screw thread engagement. By preventing rotation of
the bracket 400, actuation by the Y-actuator 360 rotates the ball
screw 370 which in turn results in linear motion of the bracket.
The rotational mounting of the bracket 400 with the rotary link 270
consequently leads to, at least partially, rotation of the link
270.
[0096] The assembly 260 further includes an X-actuator 340 which is
mounted to the base plate 380. The base plate 380, as well as the
Y-actuator 360 is free to move along guides 385A, B. The base plate
380 is mounted to the X-actuator 340 and guides 385A, 13 in a
similar manner to the Y-actuator 360 is mounted to the bracket 400,
that is, by a ball screw 350. Accordingly, actuation by the
X-actuator 340 causes linear movement of the base plate 380 and
Y-actuator 360 along the guides 385 A, B. It follows that, the
X-actuator 340, will therefore influence the movement of the rotary
link 270 through biasing of the base plate 380 and Y-actuator
360.
[0097] FIGS. 9A to 9G show a sequence of movement of the rotary
conveyor assembly 260. As with FIG. 8, the other half of the
conveyor 260 has been omitted for clarity.
[0098] The process commences with the conveyor mounting 310 in a
first position which in this case is directed downwards along the
Y-axis. The bracket 400 is placed in the fully extended position
along the Y-axis by the Y-actuator 360. The base plate 380 is
placed in the left position of its intended path by the X-actuator
340 so that slide 280 is parallel to the Y axis. The slide 280 is
retracted maintaining the conveyor mounting 310 in the
aforementioned first position.
[0099] FIG. 9B shows the change in position of the components
following biasing both the X and Y actuators 340, 360. The
Y-actuator 360 has partially retracted the bracket with the
X-actuator 340 partially retracting the base plate 380. This leads
to the rotary link 260 rotating, in this case, about 45.degree..
The slide remains in the refracted position, and thus the conveyor
mounting 310 follows the circular path 335.
[0100] Further biasing by the actuators 340, 360 rotate the rotary
link 270 through to 90.degree. (FIG. 9C). By reversing the
direction of the X-actuator 340, the base plate 380 is extended,
whilst simultaneously retracting the Y-actuator 360. This results
in the conveyor mounting 310 first rotating to 135.degree. (FIG.
9D) and then to 180.degree. (FIG. 9E), such that it is directed
along the Y-axis.
[0101] In this position, the actuators 340, 3450 are fixed.
Subsequently, the slide 280 is progressively extended (FIGS. 9F,
9G) so as to move the conveyor mounting 310 outside of the circular
path 335 followed in previous steps. Here, the conveyor mounting
310 may deliver an object to a station isolated from the rotary
conveyor assembly 260, or alternatively permit an object to undergo
a process whilst within the mounting or receive a further
object.
[0102] It will be appreciated that, whilst the above process is
taking place, a conveyor mounting on the opposite side (not shown)
is similarly moving an object in reverse. Consequently, the rotary
conveyor assembly controls the processing of two objects
simultaneously, with the effect of, inter alia, reducing
bottlenecks.
[0103] It will be appreciated that the rate and extent of extension
and retraction by the actuators controls the path followed by the
conveyor mounting. Accordingly, variation of these rates and
movements may define different shaped paths including an elliptical
path, rectangular path or even one following a sinusoidal path.
[0104] It will be further appreciated that the actuators can be
either lead screws or ball screws or belt mechanism driven by
servomotors or linear motors with linear encoders.
[0105] Further still, it will be appreciated that, in this
embodiment, the mechanism uses two actuators, instead of the usual
three, to operate with three degrees of freedom (X,Y,0).
[0106] FIGS. 10A to 10C show a solder ball preparation module 505
according to one embodiment of the present invention. The module
comprises a solder ball template 515 mounted by brackets 516 within
a housing 518. The solder ball template is adapted to receive a
quantity of solder balls from a solder ball reservoir 510 for
holding in a predetermined array arrangement within a recess
517.
[0107] The solder ball reservoir 510 includes a void 507 into which
solder balls are loaded for distribution to the solder ball
template 515 as it sweeps 512 longitudinally along the X axis along
the template 515. The solder ball reservoir 510 in particular
comprises a reservoir housing 525 encapsulating the void 507.
[0108] The solder ball reservoir 510 is arranged to be supported
along a fluid interface between the template 515 and the solder
ball reservoir 510. The fluid interface is created by a fluid
interface device which substantially comprises an inlet 520 for
receiving compressed air. This is communicate through air columns
(shown in FIG. 11A) which bear against a running surface 519 of the
template so as to separate the solder ball reservoir 510 from the
template 515 by a predetermined air gap. In a preferred embodiment,
this air gap may be of the order of 0.3 mm but in any event will be
determined based upon the size of the solder balls being
distributed by the solder ball reservoir 510. Accordingly the gap
may be as small as 50 microns and can he established by one skilled
in the art who will be able to determine the optimum gap based upon
the solder ball diameter.
[0109] The solder ball reservoir 510 is arranged to sweep 512 in
the longitudinal direction by use of the pulley belt arrangement
546 which is controlled by speed control motor 550. Thus whilst the
fluid interface maintains the predetermined gap, movement to
achieve the sweeping 512 effect is achieved by the speed control
motor along linear slides 570.
[0110] Further, the template 515 is capable of lateral movement
(Y-axis) relative to the solder ball pickup head (not shown) by
operating a stepper motor 540 in communication with a lead screw
565 mounted between the housing 518 and the template 515. Thus, to
further accommodate fine adjustments, the stepper motor can effect
precise movement through use of this arrangement. An advantage of
providing the brackets 516 so as to secure the template 515
provides for the template 515 to be readily removable from the
device 505. Thus the device 505 can be used tbr a range of
different substrates by merely replacing the template 515 so as to
have different templates mountable within the device to match
different substrates types.
[0111] A feature of the template 515 is the addition of end zones
534 at opposed ends of the template, such that the "run" of the
reservoir 510 includes not just the template 515 but also the end
zones 534. This provides a number of advantages including ensuring
that the range of distribution of the solder balls is maintained
and not compromised by deceleration and acceleration of the
reservoir 510 as it approaches the end of its run. By having the
array 517 in a central portion of the full length of the run, the
rate of distribution can be constant for its full length with any
acceleration issues isolated from the distribution of solder balls
by the provision of these end zones 534. Also, the template 515 may
not match the end plates 535 flatness perfectly due to warping of
the template after prolonged usage. By minimizing the "run" of the
reservoir 510 over the end plate 535, damages to the solder balls
and reservoir housing 525 are reduced.
[0112] The device 505 further includes end plates 535 over which
the reservoir can be positioned so as to permit removal of the
template 515. Thus the reservoir will only move to the end plates
at the end of the machine run so as to permit maintenance or as
mentioned, replacement of the template.
[0113] With reference to FIGS. 11A to 11C, there is shown the
solder ball reservoir housing 525 with the various components
removed for clarity. As can be seen, the reservoir housing 525
encapsulate the void 507 so that on sweeping movement 512 along the
template 515, the solder balls can pass through the reservoir
directly onto the template and so accurately form the array within
the recess 517 of the template 515.
[0114] The fluid interface device according to the present
invention is embodied here through an air inlet into channels
within the reservoir housing 525 and exiting through air columns
580 which are directed downwards onto the running surface 519 of
the template. It follows that the gap can be adjusted through
adjusting the flow of air through the air column 580 which are
housed within recesses 581 to control said flow.
[0115] The datum from which the air gap is measured is from the
running surface 519 of the template 515. As no physical contact is
made between the reservoir housing 525 and the surface 519, the
actual surface preparation of the surface 519 is immaterial to the
maintenance of the air gap. This is in contrast with a system that
would have the housing 525 running across the template by contact
with any part of the entire module 505. The machining of the
device, required to maintain the gap, must be to a particularly
high tolerance given the required gap in order to achieve the
requisite quality. Such a high degree of tolerance in machining is
not required for the arrangement according to the present invention
because of this lack of contact between the reservoir housing 525
and the template 515. To this end the linear slide and housing 518
of the module similarly can be manufactured to a normal tolerance
which consequently will significantly reduce the manufacturing
costs of the device.
[0116] In a further embodiment of the present invention in the case
of variation in the air pressure or subsequent completion of the
array, a step 585 arranged on the under surface 590 of the
reservoir housing 525. On removal of the air pressure, the
reservoir housing 525 will drop down to be in contact with the
running surface 519 of the template. The step 585 on the under
surface 590 will, therefore, maintain a clearance with that portion
of the under surface 590 directly above the solder ball array 517.
And so this preferred embodiment, a further safeguard is provided
to prevent contamination or damage to the solder ball array 517. It
follows further that should the solder ball reservoir 510 be
interfered with, such as by an operator touching the reservoir
housing 525 and so overcoming the air pressure maintaining the air
gap, the reservoir housing 525 cannot be pushed into the solder
ball array 517, preventing accidental damage.
[0117] A further advantage of providing this fluid interface
includes a reduction in maintenance and increase in commercial life
of the device. Because of a lack of contact surface, that is the
reservoir housing 525 remains clear of the template 515, surfaces
which under normal circumstances would require a high tolerance and
therefore suffer wear more rapidly in fact do not suffer wear.
[0118] The air columns 580 shown in FIG. 11A are represented as
slots 581 in which are located a plurality of apertures. The slots
581 are located at opposed ends of the underside face 590 so as to
correspond with the running surface 519 of the template. It will be
appreciated, however, that this air column may be represented in a
different arrangement according to the required air flow in order
to maintain the fluid interface. Thus while FIG. 11A shows two
elongate slots with the apertures corresponding to these slots,
many other arrangements will also fall within the scope of the
invention as will be appreciated by the skill addressee.
[0119] FIGS. 12 and 13 show adaptor plates for mounting to solder
ball placement machines (not shown) which facilitate the mounting
of a variety of devices including solder ball and flux pick up
heads. In the absence of a single industry standard, mounting
fixtures can vary from manufacturer to manufacturer. The adaptor
plate according to this embodiment solves the problem of the lack
of industry standard by the facilitation of mounting of a variety
of manufacturers' devices. FIGS. 12A and 12B in particular, are
intended for use with a solder ball pickup providing a range of
features which both facilitate attachment as well as ensuring
secure mounting. In particular the adaptor plate 605 comprises an
aluminum body 610 with a central orifice 615. Set within the body
610 are locating holes 630 into which projections from the various
devices may be inserted. Within each locating hole 630 are steel
bushings 635 which can be readily replaced should the projections
from different manufacturers vary considerably. In any event the
steel bushings 635 can be manufactured over a wide specification so
that they can accommodate projections of different size or shape
for an individual bushing. The bushings are made of steel so as to
provide a high degree of abrasion resistance as compared to the
aluminum body 610. Further, because they are replaceable and
relatively cheap, the aluminum body 610 remains intact, in keeping
with its relatively expensive manufacture whilst replacing the
steel bushing either for accommodating different manufacturers'
devices or for replacing overly worn fixtures. Further, the tool
lock 650 can be replaced should it be necessary to accommodate a
particular manufacturer's specification. Accordingly the tool lock
650 will be selected so as to meet as wide a range of manufacturing
connections as possible. Further, the tool lock 650 can be replaced
with other standard devices to broaden the applicability of the
adaptor plate 605 without the excessive costs of manufacturing a
new body 610 for each variety.
[0120] To ensure correct placement, the body 610 also includes
locating pins 640 to be inserted within specific recesses within
the required machines. A resilient engagement portion such as the
press fit device 620 having spring loaded projections 625 which can
be used to press fit into the relevant devices and be held in place
securely and accurately but without time consuming fasteners.
Whilst the adaptor plate 605 is securely mounted within the device
using the press fit portion 620, the spring loaded projections 625
allow it to be quickly removed and replaced or to be modified such
as replacement of the tool lock 650 or steel bushings 635.
[0121] The adaptor plate 605 as shown in FIGS. 12A and 12B require
the provision of a vacuum supply and accordingly the aluminum body
610 incorporates a vacuum inlet 655 in one face of the adaptor
plate which receives the vacuum supply through a plurality of
vacuum holes 645. In this embodiment there are eight such vacuum
holes 645 equally spaced around the opposed face of the adaptor
plate 605 with internal channels (not shown) maintaining
communication between the vacuum holes 645 and the vacuum source
655. Thus by a simple press fit the adaptor plate 605 can be fitted
to a solder ball pick up and in an appropriate device attached
thereto.
[0122] The arrangement is equally applicable to a flux pick up as
shown in FIGS. 13A and 13B whereby the locating holes 630 with
steel bushings 635 are also present. Further the locating pins 640
and tool locks 650 are also present for attachment to the various
devices. Further still, the advantages of a press fit device are
provided for a similar resilient portion 630 with spring loaded
projections 625.
[0123] Because the vacuum source is not required for the flux pick
up, the adaptor plate 665 does not incorporate the vacuum source
features of the adaptor plate 605 of the solder ball pick up.
However, the body 680 of the flux pick up adaptor plate 665 does
incorporate void 685 within the body 680 similar to voids 660 in
the body 610 of the solder ball pick up adaptor plate 605. Because
of the lack of vacuum source required for this application, the
voids 685 can accordingly be larger and, therefore, further
reducing the weight of the adaptor plate 605.
[0124] FIG. 14 shows an arrangement where flux 710 is delivered to
a flux pool 740 on a sweep 745 across the flux pool 740 whilst on
the plate 722 and so smooth out the flux pool 740 to a known
thickness for collection and delivery to the substrate. This is
typically achieved by a syringe 700 having the flux 710 within a
containment chamber. Pressure 720 is applied to the flux 710
through a plunger 715 which is forced downwards by air pressure.
Consequently flux 710 is forced into an exit chamber 705 to exit
through nozzle 725 thus delivering flux 730 to the flux pool 740.
The difficulty arises in that after the pressure 720 is removed,
flux still remains within the exit chamber 705 and, subject to
gravity, can drip in an uncontrolled manner so as to lead to
contamination by dropping flux 750 onto various components such as
the flux applicator 735. This contamination can be transferred to
subsequent flux pools which may then be transferred to substrates
leading to significant wastage of product during attachment of the
solder balls. As the flux is sticky, it can attract foreign
particles which will affect the accuracy of the placement of the
solder balls. Also if flux is being accidentally deposited on
either the Solder Ball Pickup Head or the Solder Ball Reservoir,
the operation of the whole machine will be affected as the flux
contaminated solder balls will attached to any surface that it
comes into contact with. FIG. 15 shows a solution to this problem
by the introduction of a second pressure source 755 which injects
air pressure directly into the exit chamber 705. The injection of
air through the inlet 755 blows out the excess flux from the nozzle
under a controlled environment such as into a waste bin or if the
pressure through the inlet 755 is sufficiently controllable,
emptying the remaining flux into the flux pool 740. The result is
the lower most portion of the flux 760 being above the inlet 755
leaving the exit chamber substantially clear 765 such that no flux
can drip in an uncontrolled manner. Accordingly the addition of the
second pressure source through the inlet 755 avoids significant
problems involved in contamination through uncontrolled dripping of
flux.
* * * * *