U.S. patent application number 10/233746 was filed with the patent office on 2003-01-16 for conveyorized vacuum injection system.
Invention is credited to Avery, Kevin, Gordon, Jules, Nowak, Thomas, Thurlow, David.
Application Number | 20030010286 10/233746 |
Document ID | / |
Family ID | 23962048 |
Filed Date | 2003-01-16 |
United States Patent
Application |
20030010286 |
Kind Code |
A1 |
Nowak, Thomas ; et
al. |
January 16, 2003 |
Conveyorized vacuum injection system
Abstract
The present invention provides a method and apparatus for
dispensing materials onto a substrate. In one embodiment, a
dispensing system includes a controller, a vacuum source in
electrical communication with the controller, the vacuum source
applying a vacuum to at least a portion of the substrate in
response to an instruction from the controller, an injector in
electrical communication with the controller, the injector
comprising a valve in communication with a pressure source and a
material port in communication with a material source, the valve
permitting material from the material source to be dispensed onto a
substrate in accordance with an instruction from the controller. In
one embodiment, the dispensing system also includes a trap in
communication with the vacuum source, where the trap substantially
prevents excessive material dispensed by the injector from
contacting the vacuum source.
Inventors: |
Nowak, Thomas; (N. Hampton,
NH) ; Gordon, Jules; (Methuen, MA) ; Avery,
Kevin; (Salisbury, MA) ; Thurlow, David;
(Newbury, MA) |
Correspondence
Address: |
MINTZ, LEVIN, COHN, FERRIS,
GLOVSKY and POPEO, P.C.
One Financial Center
Boston
MA
02111
US
|
Family ID: |
23962048 |
Appl. No.: |
10/233746 |
Filed: |
September 3, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10233746 |
Sep 3, 2002 |
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09493873 |
Jan 28, 2000 |
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6444035 |
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Current U.S.
Class: |
118/684 ;
118/50 |
Current CPC
Class: |
B29C 39/24 20130101;
B29C 39/42 20130101; H01L 21/67126 20130101; B29C 39/10
20130101 |
Class at
Publication: |
118/684 ;
118/50 |
International
Class: |
B05C 011/00 |
Claims
1. A dispensing system for dispensing material onto a substrate,
the dispensing system comprising: a controller; a vacuum source in
electrical communication with the controller, the vacuum source
applying a vacuum to at least a portion of the substrate in
response to an instruction from the controller; an injector in
electrical communication with the controller, the injector
comprising a valve in communication with a pressure source and a
material port in communication with a material source, the valve
permitting material from the material source to be dispensed onto a
substrate in accordance with an instruction from the
controller.
2. The system of claim 1 wherein the valve permits material to be
dispensed onto a substrate when pressure is applied to the valve
and prevents material from the material source from reaching the
substrate when pressure is removed from the valve.
3. The system of claim 1 further comprising an injecting outlet
through which the material source injects material to a process
area on the substrate and an air inlet through which the vacuum
source draws air from a process area on the substrate, thereby
drawing the injected material through the process area.
4. The system of claim 3 further comprising a trap coupled to the
air inlet and the vacuum source to receive excess material
dispensed onto the substrate.
5. The system of claim 4 wherein the trap further comprises a level
sensor detecting the level of excess dispensed material in the
trap.
6. The system of claim 5 wherein the level sensor is operably
coupled to the controller.
7. The system of claim 6 wherein the controller prevents material
from being dispensed onto the substrate when the level sensor
detects a predetermined quantity of material in the trap.
8. The system of claim 3 wherein at least one of the injecting
outlet and the air inlet are constructed and arranged to mate with
a respective hole in a layer of cover material disposed adjacent to
the process area of the substrate.
9. The system of claim 3 wherein at least one of the injecting
outlet and the air inlet are constructed and arranged to project
through a respective hole in a layer of cover material disposed
adjacent to the process area of the substrate.
10. The system of claim 9 wherein at least one of the injecting
outlet and the air inlet is constructed and arranged to retract
through the layer of cover material when dispensing is
complete.
11. The system of claim 3 wherein the injecting outlet and the air
inlet are constructed and arranged to engage respective holes in a
layer of cover material disposed adjacent to the process area of
the substrate.
12. The system of claim 11 wherein the injecting outlet and the air
inlet are constructed and arranged to align with respective holes
that are disposed on opposite sides of the process area.
13. A method for adding material to a component attached to a
substrate, comprising the steps of: sealing a process area around
the component; applying a negative air pressure to withdraw air
from within the process area; dispensing material to the sealed
process area; stopping the dispensing of material; and stopping the
application of negative air pressure to the process area.
14. The method of claim 13 wherein the step of applying a negative
air pressure further comprises applying the negative air pressure
through a first opening that is disposed adjacent to a first side
of the component.
15. The method of claim 14 wherein the step of applying a negative
air pressure further comprises extending an inlet in communication
with a source of negative air pressure through the first
opening.
16. The method of claim 15 further comprising the step of
retracting the inlet after stopping the application of negative air
pressure.
17. The method of claim 14 wherein the step of dispensing material
further comprises dispensing material through a second opening
adjacent to a second side of the component.
18. The method of claim 17 wherein the step of dispensing material
further comprises extending an outlet for the material through the
second opening.
19. The method of claim 18 further comprising the step of
retracting the outlet from the second opening after stopping the
dispensing of material.
20. The method of claim 13 wherein the step of sealing the process
area further comprises covering the process area with a sheet of
cover material.
21. The method of claim 20 wherein the step of applying a negative
air pressure further comprises applying a vacuum through a vacuum
opening in the sheet of cover material.
22. The method of claim 20 wherein the step of dispensing material
further comprises dispensing material through an injection opening
in the sheet of cover material.
23. The method of claim 13 wherein the step of stopping the
dispensing of material further comprises stopping the dispensing of
material upon the occurrence of a condition selected from the group
consisting of elapse of a predetermined time limit, detection of a
predetermined level of dispensed material, and detection of a
predetermined level of dispensed material located in a trap
arranged to receive excess dispensed material.
24. The method of claim 13, further comprising the step of catching
excess dispensed material in a trap.
25. The method of claim 13 wherein the step of stopping the
application of negative air pressure occurs prior to the step of
stopping the dispensing of material.
26. A system for adding encapsulant material to a component
attached to a substrate, comprising: means for applying a negative
air pressure to a process area on the substrate, the negative air
pressure means applying a negative air pressure to at least a
portion of the substrate; means for injecting encapsulant material
to a process area on the substrate, the injecting means comprising
a valve means in communication with a means for applying pressure
and an output means in communication with a means for dispensing
material, the valve means permitting the material from the
dispensing means to be dispensed to the component through the
output means.
27. The system of claim 26 further comprising a means for trapping
excess material dispensed onto the substrate, the trapping means in
communication with the negative air pressure means.
28. The system of claim 26 wherein the valve means and the output
means are constructed and arranged to engage respective openings in
a layer of cover material disposed adjacent to the process area of
the substrate.
29. A system for adding encapsulant material beneath a component
attached to a substrate, comprising: means for applying a negative
air pressure to at least a portion of a space existing between the
component and at least a portion of the substrate; means for
injecting encapsulant material to the space, the injecting means
comprising a valve means in communication with a means for applying
pressure and an output means in communication with a means for
dispensing material, the valve means permitting the material from
the dispensing means to be dispensed to the component through the
output means; and a controller for controlling the means for
applying a negative air pressure and the means for injecting
encapsulant material.
30. The system of claim 29 further comprising a means for trapping
excess material dispensed onto the substrate, the trapping means in
communication with the negative air pressure means.
31. The system of claim 29 wherein the valve means and the output
means are constructed and arranged to engage respective openings in
a layer of cover material disposed adjacent to the process area of
the substrate.
32. The system of claim 30 wherein the trapping means is in
operable communication with the controller, wherein the trapping
means notifies the controller when the excess material being
trapped reaches a predetermined amount.
33. The system of claim 30 wherein the trapping means is in
operable communication with the controller, wherein the controller
means monitors the amount of material being trapped.
Description
RELATED APPLICATION
[0001] This application is related to U.S. Utility application Ser.
No. 09/168,536, filed Oct. 10, 1998, which is incorporated by
reference herein.
FIELD OF THE INVENTION
[0002] The present invention relates to an apparatus, process, and
system for encapsulating electronic parts, and more specifically to
an apparatus and process which uses changes in air pressure to
force material under and around an electronic integrated circuit
chip.
BACKGROUND OF THE INVENTION
[0003] The need for denser, larger and more durable chip assemblies
has broadened the use of Direct Chip Attach (DCA) technology to
include flip chip integrated circuits. A typical flip chip
integrated circuit utilizes a solder ball grid array to provide
electrical connections between a die of the flip chip and a
substrate. During manufacturing of a typical flip chip, after the
flip chip is assembled on a substrate, a liquid dispensing system
is used to apply an underfill encapsulant material between the die
and the substrate. The flip chip underfill material is used to
reduce mechanical and thermal stress on the electrical connections
and to protect the electrical connections against atmospheric
conditions. The underfill material provides stability and rigidity
to the assembled flip chip and may also be used as a heat conductor
to improve thermal performance of the flip chip.
[0004] In typical prior art flip chip underfilling processes, a
dispenser system is used to dispense underfill material around the
sides of the flip chip and the underfill material spreads under the
flip chip and around the solder balls of the grid array via
capillary action or "wicking". During the assembly process, the
substrate is typically heated prior to, during, and after
dispensing of the underfill material to a temperature ranging from
ambient conditions to approximately 120.degree. C. The heating of
the substrate increases the capillary action causing the underfill
material to flow further under the die of the flip chip. A final
fillet of underfill material is applied around the sides of the
flip chip after the wicking action has occurred. A drawback
associated with such underfilling processes is that the underfill
material may not completely fill all voids between a die and a
substrate in a flip chip. For example, the underfill material can
fail to fill spaces between the contacts of a die.
[0005] To overcome the problem of voids or air gaps, one prior art
dispensing system developed by Tessera of San Jose, Calif. utilizes
a vacuum approach to completely underfill flip chips. In this prior
art system, the dispensing system, including one or more flip chips
that are to receive underfill material, is enclosed within an air
tight chamber, and prior to the dispensing of underfill material, a
vacuum pump is used to purge all air from the chamber to create a
vacuum. The underfill material is then dispensed around all sides
of the flip chips, and the chamber is returned to ambient pressure.
When the chamber is returned to ambient air pressure, the underfill
material is forced under the flip chips by the difference in air
pressure outside the flip chips and under the flip chips.
[0006] While the above described prior art system is effective in
preventing voids in underfill material in flip chips, the system is
relatively large and the time required to purge air from the air
tight chamber is rather long. Further, because the airtight chamber
is so large, it is difficult to effectively purge air from the
chamber. In addition, the air tight chamber of the prior art
accommodates only manual loading of the flip chips into the
chamber, preventing the dispensing system contained within the
chamber from being effectively used in an automated assembly line.
Moreover, the large size of the airtight chamber often precludes it
from easy integration into automated manufacturing processes.
SUMMARY OF THE INVENTION
[0007] The present invention overcomes disadvantages of the prior
art by providing a system, apparatus and process for encapsulating
flip chips using dispensing systems having fixtures operating
cooperatively with injection and vacuum valves to overcome
drawbacks of the prior art systems.
[0008] In one embodiment, a dispensing system includes a
controller, a vacuum source in electrical communication with the
controller, the vacuum source applying a vacuum to at least a
portion of the substrate in response to an instruction from the
controller, and an injector in electrical communication with the
controller and having a vacuum port in communication with the
vacuum source, the injector comprising a valve in communication
with a pressure source and a material source, the valve permitting
material to be dispensed from the material source onto a substrate
in accordance with an instruction from the controller.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] For a better understanding of the present invention,
reference is made to the drawings, which are incorporated herein by
reference, and in which:
[0010] FIG. 1 illustrates a workpiece usable in accordance with the
invention and shows the flow of encapsulating material at the
workpiece in accordance with an embodiment of the invention.
[0011] FIG. 2 is a block diagram illustration of a vacuum injection
system, in accordance with one embodiment of the invention.
[0012] FIG. 3 is flow chart representation of a vacuum injection
process, in accordance with one embodiment of the present
invention.
[0013] FIG. 4 is a perspective view of a vacuum injection system,
in accordance with one embodiment of the invention.
[0014] FIG. 5 is a perspective view of the conveyorized portion of
the vacuum injection system of FIG. 4.
[0015] FIG. 6 is a side view of the conveyorized portion of FIG. 5,
viewed along the AA axis.
[0016] FIG. 7 is a side view of the conveyorized portion of FIG. 5,
viewed along the BB axis.
[0017] FIG. 8 is another side view of the conveyorized portion of
FIG. 5, viewed along the BB axis, illustrating the conveyorized
portion in more detail.
[0018] FIGS. 9A-9B are front and exploded views, respectively, of
the injection valve of FIGS. 1-8, in accordance with one embodiment
of the invention.
[0019] FIG. 10 is an exploded view of the vacuum nozzle FIGS. 1-8,
in accordance with one embodiment of the invention.
DETAILED DESCRIPTION
[0020] For purposes of illustration, embodiments of the present
invention will now be described with reference to a dispensing
system used to dispense underfill material beneath and around
electronic components such as flip chip integrated circuits. One
skilled in the art will appreciate, however, that embodiments of
the present invention are not limited to dispensing underfill
materials for flip chip integrated circuits, but may be used in
other applications.
[0021] As used in this description, the term "vacuum" does not
necessarily refer only to producing a space entirely devoid of
matter, but rather is intended also to encompass producing a space
from which matter, especially air, has been partially or
substantially removed.
[0022] One technique for encapsulating electronic components is
described in an application filed under the Patent Cooperation
Treaty (PCT) having Publication Number WO 99/53616, the contents of
which are incorporated herein by reference. In the described
method, electronic components are disposed in an assembly having
top and bottom sealing layers defining an enclosed space containing
the components. The assembly is engaged in a test fixture, and the
enclosed space is evacuated by applying a vacuum to a hole in one
of the sealing layers. Then, the vacuum is removed from the hole, a
needle is advanced into that hole, and a liquid encapsulant is
injected through the needle into the enclosed space around the
electronic components. The encapsulant flows into the enclosed
space, where it is free to flow around the components.
[0023] One disadvantage of this method, however, is that the vacuum
and encapsulant flowing through the needle must be precisely
controlled to ensure proper flow. Another disadvantage is that the
injected liquid encapsulant may not flow sufficiently around and
under all of the components to properly encapsulate each component.
Still another disadvantage is that excess encapsulant can flow back
out of the hole and contaminate the assembly, text fixture, vacuum,
or other elements. Yet another disadvantage is that waiting for the
liquid encapsulant to flow around each component increases the
process time for encapsulating the components.
[0024] FIG. 1 illustrates a workpiece 27, such as a substrate,
having components 28 that may receive encapsulant material 24 using
processes and apparatuses of the present invention. In FIG. 1,
material 24 is shown flowing through the workpiece during an
encapsulation process. The workpiece 27 includes a hollow area 26,
in which several components to be encapsulated, namely electronic
components 28 having leads 30, are disposed. The hollow area 26 of
workpiece 27 in FIG. 1 can be formed between a top coverlay tape 34
disposed on the "die side" (i.e., the top of the components 24) and
a bottom coverlay tape 32 disposed on the "contact side" (i.e., the
bottom of the components 28). An injection hole 33 is formed in the
top coverlay tape 34 at a first side of the hollow area 26 to
permit encapsulation material 24 to be injected. Similarly, a
vacuum hole 35 is formed in the top coverlay tape 24 to permit a
vacuum to be drawn on the hollow area 26. Having the injection hole
33 and vacuum hole 35 as separate holes, disposed on opposite sides
of the hollow area 26, is advantageous because the vacuum being
pulled at the vacuum hole 35 helps to rapidly draw the material 24
through the hollow area 26 and around the components 28 and also
helps to ensure that the material 24 flows around, over, and under
all of the components 28.
[0025] It should be understood that illustration of three
electronic components 28 is not intended to be limiting; any number
of components can be disposed in the hollow area 26. Further, the
articles disposed in the hollow area 26 need not be electronic or
other types of components, but rather can include any articles to
be encapsulated. As FIG. 1 illustrates, the material 24 not only
flows around the components 24 but also flows around the leads 30
of the components 28, thereby helping to prevent voids in the
encapsulant.
[0026] FIG. 2 shows a block diagram of one embodiment of a vacuum
injection system 10 in accordance with the invention, for
dispensing media such as underfill material along the sides,
underneath, and between components such as flip chip integrated
circuits (not shown) disposed on a workpiece 27 or carrier (not
shown). The vacuum injection system 10 includes a controller 12, a
vacuum source 14 having a nozzle 16, an injector 18 having an
injector valve 20, and a trap 22. The injector 18 injects underfill
material 24 receiving force from a pressure source 23. During
operation of the vacuum injection system 10, the vacuum nozzle 16
connects to the vacuum hole 35 on one side of the hollow area 26 in
the workpiece 37 so that the vacuum source 14 to draw a vacuum on
the hollow area 26, while the injector valve 20 permits the
injector 18 to inject encapsulating material 24 into the injection
hole 33. The vacuum applied by vacuum source 14 draws the
encapsulating material 24 from the injection hole 33 towards the
vacuum source 14, so that the encapsulating material 24 can
encapsulate and underfill all of the components in the hollow area
26 while substantially eliminating voids. This is explained more
fully below.
[0027] The controller 12 can be any system or processor capable of
controlling the vacuum injection processes described herein. For
example, the controller 12 can be a programmable logic controller
(PLC), a general purpose digital computer running one or more
programs relating to control of the vacuum injection processes, or
a proprietary processor system board. In one embodiment, the
controller 12 is a proprietary processor system board having a
plurality of input/output (I/O) control points. In another
embodiment, the controller 12 can further include or access one or
more daughter boards that can provide other circuit functions, such
as analog I/O, high power switching, communications to peripherals,
video display, and the like. In still another embodiment, the
controller 12 is a computer having a PENTIUM microprocessor
(manufactured by Intel Corporation of Santa Clara, Calif.) and
storing and running a plurality of process instructions and
associated software relating to control of the system 10. The
controller 12 can be a stand-alone computer, such as a personal
computer, or can be networked to one or more other computers.
[0028] In one embodiment, the controller 12 stores a plurality of
process "recipes" relating to encapsulating components and/or
assemblies on the workpiece 27. For example, a process recipe may
include all instructions and control programs necessary to
encapsulate a predetermined quantity of a predetermined component
disposed on a fixture having a predetermined size. Because the
controller 12 is in communication with the injector 18 and the
vacuum source 14, it can program either or both of these elements
to operate in accordance with a particular process for a particular
component or material. In another embodiment, the controller 12 can
monitor the vacuum level at the vacuum source 14 and adjust it as
necessary. In another example, the controller 12 can control the
injector 18 to inject material 24 for a predetermined time by
enabling and disabling the injector valve 20.
[0029] For example, the controller 12 can instruct the vacuum
source 14 to apply a predetermined vacuum level (e.g., 5 inches of
mercury (in./Hg)) to the workpiece 27 and to maintain this vacuum
level for a predetermined time. While the vacuum level is
maintained, the controller 12 directs the injector 18 to configure
the injector valve 20 to inject a specific quantity (e.g., 1 cubic
centimeter (cc)) of a material 24, for example silicone
encapsulant, from a particular source of material 24, such as a
particular cartridge or syringe of material 24.
[0030] Vacuum source 14 can be a pump, such as an oil-free vacuum
pump, capable of reaching a predetermined vacuum level within a
predetermined time. In one embodiment, the vacuum pump is a
diaphragm-style pump manufactured by Varian Associates of Lexington
Md. For example, in one embodiment, the vacuum source 14 can reach
a maximum vacuum of 28 in./Hg within 5 seconds. The vacuum level
and time during which vacuum is applied can be set; for example,
they can be programmed by controller 12 or set manually using one
or more switches. Depending on how it is programmed, the vacuum
source 14 can apply a vacuum at its nozzle 16 to the hollow area 26
before, during, and/or after injection of the material 24. This
permits the vacuum source 24 to "draw" injected material 24 through
the hollow area 26 after the material 24 has been injected, thereby
encapsulating components therein without voids. In addition, by
continuing to apply a vacuum to the hollow area 26 after injection
of the material 24, the material 24 can be drawn through the hollow
area 26 faster than the material 24 flows without the vacuum being
applied.
[0031] The trap 22 is disposed between the vacuum source 14 and the
vacuum nozzle 16 to trap possible excess material 24 injected into
the hollow area 26 of the workpiece 27, to prevent contamination of
the vacuum source 14. For example, the trap 22 can be a jar having
a removable reservoir, so that material 24 in the trap 22 can be
removed easily. In one embodiment, the trap 22 includes a
disposable and easily removed reservoir. Many different types and
styles of reservoir-type devices are usable in accordance with this
aspect of the invention, as those skilled in the art will
recognize.
[0032] In one embodiment, the trap 22 can include a level sensor
(not shown) capable of detecting the level of material 24 in the
trap 22. Those skilled in the art will recognize that many
different types of sensing devices are usable to detect the level
of material 24 in the trap 22. The level sensor can stop the
injection process if the material 24 in the trap 22 reaches a
predetermined level, such as if the trap 22 becomes three quarters
full. Alternately, the controller 12 can monitor the level of
material 24 and stop the injection process if the material 24 in
the trap 22 reaches a predetermined level. The vacuum source 14 is
coupled to a vacuum nozzle 16 adapted to fit tightly to the vacuum
hole 35 on the workpiece 27.
[0033] The injector 18 can accommodate workpieces 27 and/or hollow
areas having differing sizes. The injector 18 can include an
injection port 21 that fits tightly to (or within) the injection
hole 33 on the workpiece 27 to inject material 24 into the hollow
area 26 after the vacuum source 14 has evacuated air from the
hollow area 26. In another embodiment, the injector 18 can begin
injecting material 24 into the hollow area 26 while the vacuum
source 14 is evacuating air from the hollow area 26. A pressure
source 23, such as a cartridge assembly manufactured by EFD Inc. of
Providence, R.I., uses pressure to force the material 24 out of the
injection port 21 and into the hollow area 26. In one example, the
material 24 is stored in a cartridge or syringe and pressure is
applied to the cartridge to force material 24 from the cartridge
out through the injection port 21. In one embodiment, the pressure
source 23 can be an air-driven or mechanical ram.
[0034] The injector 18 provides a positive shut-off, which can help
to prevent material 24 from dripping out of the injection port 21
after pressure on the material 24 is released or after injection of
a predetermined quantity of material 24 is complete. In one
embodiment, the positive shut-off is provided using a valve 20 that
is precisely controlled by controller 12. This aspect is described
more fully below. In another embodiment, the injector 18 can
include one or more ports (not shown) accepting syringes and/or
cartridges containing material 24 to be injected. In still another
embodiment, the injector 18 can be supplied with material 24 from a
bulk feeding device such as a ram pail pump, such as the DynaMite
190 manufactured by Graco, Inc. of Minneapolis Minn. The controller
12 can communicate with the injector valve 20 to control operation
of the injector 18, when injection occurs, to control the level of
pressure applied at the pressure source 23, to release the pressure
on the pressure source 23, to select the source of material 24, and
to control the flow of material 24 into the injector 18.
[0035] The material 24 can be any material used for encapsulating
articles. For example, some materials, such as silicone chip
encapsulant material, can be used as a compliant layer to decouple
the mismatched thermal expansion rates of silicon and common
printed circuit board (PCB) laminates (to which a silicon
electronic component being encapsulated may later be attached).
Silicone chip encapsulant material can also increase the solvent
resistance of the article being encapsulated.
[0036] The workpiece 27, integrated circuits or other substrates
that are to receive dispensing material in the system 10 can be
transported as individual units on conveyors, multiple units in a
common carrier, or using a continuous tape feeder system. The
workpiece 27 can, in one embodiment, include such individual units,
multiple units on a common carrier, or a continuous tape feeder
system. The system 10 may include a conveyor (not shown in FIG. 1,
but illustrated in FIGS. 4-8) for loading and unloading integrated
circuits or multiple unit common carriers into the dispensing
system. Alternatively, the system 10 may be configured as known in
the art for receiving a continuous tape having integrated circuits
that are to receive encapsulant material bonded to the top surface
of the tape.
[0037] FIG. 3 illustrates a flow chart of a process for
encapsulating components using the system 10 of FIG. 1, in
accordance with an embodiment of the invention. In a first step of
the process, the chip or component 28 is aligned on the workpiece
27 or carrier and is sealed, such as by the top and bottom coverlay
tapes 34, 32 of FIG. 2 (step 40). The carrier or workpiece 27 at an
injection point in the system 10 is positioned on a conveyor (step
42). The vacuum and encapsulation holes 35, 33 (also referred to as
vacuum input and injection input, respectively) are contacted by
the vacuum and injection ports (step 44). The vacuum source 14
draws a vacuum at a first side of the workpiece 27 (step 46) to
evacuate air from the hollow area 26 containing the components 28
to be encapsulated while simultaneously drawing encapsulant
material 24 through the hollow area 26. In one embodiment, prior to
step 44 the workpiece 27 may be lifted off of the conveyor to place
the vacuum and injection ports 35, 33 in contact with the vacuum
nozzle 16 and a nozzle at the injector 18.
[0038] After the vacuum source 14 begins applying the vacuum, the
injector valve 20 opens to begin dispensing material 24 into the
hollow area 24 (step 48). Because the material 24 is at a pressure
higher than that in the hollow area 26, the material 24, after
being injected from the injector valve 20 is drawn through the
hollow area 26, towards the vacuum hole 35. In addition, because
the vacuum source 14 is applying a vacuum to the hollow area 26,
the material 24 will flow through the hollow area 26 faster than if
the hollow area 26 were evacuated then the vacuum was removed. The
controller 12 determines how long the vacuum source 14 applies the
vacuum and how long the injector 18 can inject material based on a
number of factors, which can include the size of the hollow area
26, the number of components 28, the type of material 24, the level
of the vacuum being applied, and the amount of material in the trap
22. Those skilled in the art will recognize that other factors may
affect the time for encapsulation. Based on information from the
controller 12, the injection valve 20 is closed at a predetermined
time to stop the injection of material 24 into the hollow area 26
(step 50), and the vacuum is released at a predetermined time. Any
excess material 24 that flows out of the vacuum hole 35 flows into
the trap 22 and is contained in the trap 22, instead of
contaminating the vacuum source 14 (step 52). Then, the injector 18
and vacuum source 14 are be removed from the injection and vacuum
holes 33, 35 (step 54), and the next encapsulation step (such as
curing of the encapsulant) can proceed.
[0039] Note, however, that other events can cause the injection
valve 20 (and/or the vacuum valve 16) to stop the encapsulation
process from continuing. For example, if a sensor in the trap 22
indicates that the material 24 in the trap 22 reaches a
predetermined level, the sensor in the trap 22 can either disable
the vacuum source 14, or close the injector valve 20, to stop the
vacuum from drawing material 24 through the hollow area 26. It
should also be understood that the order of steps 50 and 52 can be
reversed; that is, the vacuum can be released before the injection
valve 20 is shut.
[0040] An embodiment of an automated vacuum encapsulation system
100 in accordance with the present invention will now be described
with reference to FIGS. 1 and 4-9. The automated system 100
includes encapsulation assemblies 102, a conveyor 104, and a
display and control panel 106. The panel 106 includes various
indicators and switches permitting operators to monitor or control
at least a portion of the encapsulation process being run at the
system 100. For example, if the encapsulation system 100 included a
trap 22 (FIG. 1), the panel 106 can include indicators informing an
operator the status of the trap 22 (e.g., empty, quarter-full,
three quarters full, etc.) or that the trap 22 must be emptied to
avoid a shutdown of the system 100.
[0041] Also contained within the system 100 are control electronics
for the vacuum encapsulation process, such as a controller 12,
power circuitry (not shown), air sources (not shown), control
pneumatics for the injectors 18 and other devices, cooling fans,
and the like. In one embodiment, the control electronics includes a
controller 12 having a microprocessor such as a PENTIUM processor,
which can be programmed to control the dispensing system, to
control the flow of workpieces 27 such as integrated circuits into
and out of the dispensing system, and to operate some or all of the
other control electronics.
[0042] The conveyor 104 of the encapsulation system 100 flows from
left to right and is manually adjustable to accommodate parts of
varying widths. For example, in this embodiment, the conveyor 104
can be adjusted from 50 mm to 180 mm between its rails 104', 104".
A plurality of sensors (not shown) are operable with the conveyor
104 to sense when a workpiece 27 (FIG. 1) has been placed at the
entrance end (left side) of the conveyor 104 and to sense when a
workpiece 27 has reached an injector assembly 102. The conveyor 104
is made from materials that are safe from electrostatic discharge
(ESD).
[0043] Referring to FIG. 5, the injector assemblies 102 are
illustrated in greater detail. Each injector assembly 102 includes
a material assembly 108 dispensing material 24 used for
encapsulation. For example, the material assembly 108 accepts 80 cc
syringes and 150 cc cartridges as reservoirs for material 24. The
locations of the material assemblies 108 ensure that they can be
easily accessed and maintained by operators of the system. If the
system 100 is running in a continuous high volume environment,
however, the materials assembly 108 can be coupled to a bulk
material feeding device to avoid frequent replenishment of material
24 while running.
[0044] As workpieces 27 move along the conveyor 104, when the
workpiece 27 reaches the injector assembly 102, a pneumatic
assembly 109 helps to lifts the workpiece 27 off of the conveyor
104 and towards the injector assembly 102 (this is shown in greater
detail in FIG. 8). When lifted, the workpiece 27 is disposed to
contact its injection hole 33 and vacuum hole 35 with a nozzle of
the injector valve 20 (not shown in FIG. 5) of the injector 18, and
the vacuum nozzle 16 coupled to the vacuum source 14 (not shown in
FIG. 5), respectively.
[0045] FIG. 6 illustrates a side view of an injector assembly 102
of FIG. 5 taken along the AA line. This view illustrates the
relative physical locations of the injector valve 20 and the
pneumatic assembly 109 to the conveyor 104.
[0046] FIG. 7 illustrates another side view of the injector
assemblies 102 of FIG. 5 taken along the B-B line. In this view,
alignment pins are 110, 112 are shown projecting from a top fixture
element 114 in the injector assembly 102. The alignment pins 110,
112 mate with corresponding alignment holes in the workpiece 27, to
ensure that the vacuum nozzle 16 and the injector 18 can make
proper contact with the injection hole 35 and the vacuum hole 33.
Although the alignment holes in the workpiece 27 are not
illustrated, those skilled in the art will recognize that
conventional alignment pins and alignment holes can be used to
align the workpiece 27.
[0047] FIG. 8 illustrates still another side view of the injector
assemblies 102 of FIG. 5 taken along the B-B line. In this view,
the injector nozzle 20 and the vacuum nozzle 18 pass through the
top fixture element 114, from which alignment pins 110, 112
project. The workpiece 27 is disposed on a movable bottom fixture
element 116, which has been raised a predetermined distance above
the conveyor 104, to bring the workpiece 27 towards the injector
nozzle 20 and vacuum nozzle 18 at the top fixture element 114. The
alignment pins 110, 112 are engageable with corresponding alignment
holes in the workpiece 27 and in the bottom fixture element 112, to
hold the workpiece 27 and the top and bottom fixture elements 114,
116 at a predetermined alignment.
[0048] As the alignment pins 110, 112 are engaged with the
workpiece alignment holes and the bottom fixture element alignment
holes, the top face of the bottom fixture element 116 is urged
towards the bottom face of the top fixture element 114, until the
injector nozzle 20 and vacuum nozzle 16 engage the injection hole
33 and vacuum hole 35 of the workpiece 27. Depending on the depth
of the alignment holes, the length of the alignment pins 110, 112
and the thickness of the top fixture element 114 where the vacuum
nozzle 16 and injector nozzle 20 pass through it, the top fixture
element 114 may be in contact with the bottom fixture element 116
when the vacuum nozzle 16 and injector nozzle 20 are in proper
engagement with the vacuum hole 35 and injector hole 33.
[0049] Although FIGS. 6-8 illustrate that the bottom fixture
element 116 has alignment holes and the top fixture element 113 has
alignment pins 110, 112, those skilled in the art will recognize
that the top fixture element 114 could instead have the alignment
holes and the bottom fixture element 116 could have the alignment
pins. Similarly, although FIGS. 6-8 illustrate that the bottom
fixture element 116 is lifted vertically above the conveyor 104
towards the top fixture element 114, it is possible to instead move
the top fixture element 114 towards the bottom fixture element 116,
or to move both the top fixture element 114 and the bottom fixture
element 116 towards each other. In addition, the fixture element
that contacts that contacts the workpiece 27 surface (or the die
surface of a component on a carrier) can be adjustable to
compensate for variations in the thickness of the workpiece 27 or
die thickness. This compensation allows proper clamping and
fixturing of the components being processed due to lot
variations.
[0050] FIGS. 9A-9B illustrate an example of an injector valve 20
usable in accordance with an embodiment of the invention. The
injector valve 20 includes a stroke cylinder 66, stopper rod
assembly 60, and nozzle assembly 82, along with various fitting and
hardware components, which operate together to provide a positive
shut-off function that the controller 12 (FIG. 2) can control with
precision. Each of these elements is described more fully
below.
[0051] The nozzle assembly 82 includes a flexible nozzle tip 83
that forms a tight seal to the injection hole 33 of a workpiece 27
(FIGS. 1 and 2). The nozzle tip 83 is "doughnut" shaped and has an
opening in the center therein through which material 24 to be
injected can flow and which can receive the rod tip 61 of a stopper
rod assembly 60 (described more fully below) to block the hole in
the nozzle tip 83 and prevent material 24 from escaping. The nozzle
assembly 82 is coupled to a first end of an upper body assembly 78
to which a nipple assembly 76 attaches. The nipple assembly 76
couples to a source of material 24, such as the material assembly
108 (FIGS. 4-7), for receiving material to be injected. An O-ring
80 helps to form a tight seal between the nozzle assembly 82 and
the upper body assembly 78.
[0052] A piston seal 74 couples the second end of the upper body 78
to a first side of a bushing assembly 70 via a first retainer nut
72. A second retainer nut 68 couples the second side of the bushing
assembly 70 to a stroke cylinder 66 and a stopper rod assembly 60.
The stroke cylinder 66 is coupled via a length of tubing 62 and
first, second, and third fittings 56, 58, 64, to a pressure source
23 (FIG. 2). In one embodiment, the stroke cylinder 66 can be an
SMC Cylinder manufactured by Kinequip Inc., Buffalo, N.Y., such as
Model. No. NCJ2B16-050T. This model can operate with a maximum
pressure of 100 pounds per square inch (PSI), and those skilled in
the art will recognize that other stroke cylinders having
comparable specifications can be used in accordance with the
invention.
[0053] The stopper rod assembly 60 is movably coupled to the stroke
cylinder 66, such as by spring loading. During operation of the
injector valve 20, pressure from a pressure source 23 (FIG. 1) can
be applied and removed from the stroke cylinder 66. When pressure
is applied, the pressure compresses the spring biasing within the
stroke cylinder 66, thereby holding the stopper rod assembly 60
back from the nozzle tip 83. Thus, when pressure is applied, the
stopper rod assembly 60 is disposed within the upper body 78 and
nozzle assembly 82 to permit material 24 to flow through the nozzle
tip 83 of the nozzle assembly 82, through an injection hole 33
(FIG. 1) and into the hollow area 26 of a workpiece 27 (FIG.
1).
[0054] When pressure is released, the spring biasing within the
stroke cylinder releases and the stroke cylinder 66 can move the
stopper rod assembly 60 through the bushing 70 and upper body 78 so
that the rod tip 61 of the stopper rod assembly 60 is disposed at
the opening in the nozzle tip 83 of the nozzle assembly 82, to
prevent material 24 entering through the nipple 76 from escaping
through the nozzle tip 83. Because the controller 12 (FIG. 2) can
precisely control when and how pressure from pressure source 23
(FIG. 2) is applied, the flow of material 24 out of the injector
valve 20 can be precisely controlled.
[0055] FIG. 10 illustrates an example of a vacuum nozzle 16 usable
in accordance with an embodiment of the invention. A nozzle body 88
has a seal 86 at one end and a fitting 90 at the other end. The
fitting 90 and seal 86 are structured and arranged to be operable
with the vacuum source 14 (FIG. 1) and to be coupled closely to the
vacuum hole 35. Those skilled in the art will recognize the types
of vacuum nozzles that may be usable in accordance with the
invention.
[0056] As described herein, the present invention provides improved
systems, methods, and apparatuses for encapsulation of articles
such as electronic components. The controller and injector valve
precisely control the flow of encapsulant into the workpiece, which
ensures that a proper quantity of encapsulant is applied to the
articles, improves the yield of the encapsulation process, and
decreases waste of encapsulant. Having the controller control
operation of the vacuum source provides precise control of the
vacuum being applied to the workpiece. This permits the time and
magnitude of the applied vacuum to vary based on the encapsulant
used and the number and size of articles to be encapsulated.
[0057] In addition, use of a vacuum source applying a vacuum
directly to the area containing articles to be encapsulated, as
described herein, provides advantages over the prior art. First,
applying a vacuum only to that area helps to reduce the size of the
vacuum source required, thereby reducing the size of the dispensing
system overall. Second, applying a vacuum to the area in which
encapsulant is being injected at the same time that the encapsulant
is being injected speeds the flow of encapsulant through the
workpiece and helps ensure that the encapsulant thoroughly contacts
all the articles to be encapsulated. In addition, use of a trap in
connection with the vacuum source helps prevent encapsulant being
drawn through the workpiece from contaminating the vacuum source or
other areas outside of the workpiece.
[0058] Having thus described at least one illustrative embodiment
of the invention, various alterations, modifications and
improvements will readily occur to those skilled in the art. Such
alterations, modifications and improvements are intended to be
within the scope and spirit of the invention. Accordingly, the
foregoing description is by way of example only and is not intended
as limiting. The invention's limit is defined only in the following
claims and the equivalents thereto.
* * * * *