Dispensing method for epoxy encapsulation of integrated circuits

Dispensing method for epoxy encapsulation of integrated circuits
US005992688A
Ulllted States Patent [19]
[11] Patent Number:
Lewis et al.
[45]
[54]
DISPENSING METHOD FOR EPOXY
ENCAPSULATION ()F INTEGRATED
Date of Patent:
0322729
0375462 A3
0589802 B1
CIRCUITS
0608129 A1
[75]
Inventors: Alan Lewis, Carlsbad; Eric L. Austin,
Del Mar; Alec Babiarz, Encinitas;
John NeWbold, San Diego, all of Calif.
5,992,688
3841474 A1
Nov. 30, 1999
7/1989
6/1990
European Pat. Off. .
European Pat. Off. .
3/1994
7/1994
European Pat. Off. .
European Pat. Off. .
6/1990 Germany
OTHER PUBLICATIONS
[73] Assignee: Nordson Corporation, Westlake, Ohio
Tri—ContinentScienti?c, Acct/pump Modular Liquia'—Han
dling System, Technical User Manual, Doc. 7703—01, pp.
[21] App1_ No; 09/255,619
1—4, undated.
PFC Precision Series, PD—9000, Brochure, undated.
_
Dispensit Model 1000 Series, Rod Positive Displacement
[22] Flled'
Feb‘ 22’ 1999
Dispense Valve, Brochure, 1993.
Related U-S- Application Data
[62]
_ _ _
_
Primary Examiner—Gregory L. Huson
_
Division of application No. 08/828,569, Mar. 31, 1997, Pat.
No. 5,927,560.
Attorney, Agent, or Firm—Wood, Herron & Evans, L.L.P.
[57]
ABSTRACT
6
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . "i.
[
]
_. .
. ................................................. ..
22/1, 427/96
Fleld Of Search .................................. ..
[56]
integrated Circuits, includes a
References Cited
Us PATENT DOCUMENTS
2,540,390
2/1951 Gorgerat et al. ...................... .. 103/203
ghdersothl- - - - - -
A
able
for dis P ensin g tWO_ P an 6 P OX y for enca P Sulation of
_
----
3
3
3’851’801
6556 e a‘ "
12/1974 Roth """""""" "
" 222/146
4’259’975
4/1981 Kn-lsey’ Jr' et al'
137/1
4,493,350
1/1985
4,572,103
47 5977 507
2/1986 Engel .................................... .. 118/697
7/ 1986 Rosenblum et a1_
222/ 16
Beikel et al. ........................... .. 141/65
Chamber in Commu
nication With a noZZle via a three Way valve, the pumping
chamber including an outlet, an internal volume, a pair of
spaced directional seals located aWay from the outlet, an
open volume reciting betWeen the seals and an external port
Opening the Open volume to atmosphere, A stepped plunger
extends axially Within the pumping chamber, With a ?rst
portion siZed to be received and aligned through the ?rst
directional seal the plunger being movable to move the ?rst
ortion toWard the outlet to close off the internal volume at
P
,
,
the Seeehd Seal- The Seeehd Perheh of the Phlhger 1S
relativel y smaller in transverse cross-sectional dimension
4,700,870 10/1987 sehleieher et a1,
222/63
than the inside diameter of the second seal, to cooperate With
4,877,188 10/1989 Ritter .............. ..
239/135
the port to promote ?uid removal from the internal volume
5,019,409 5/1991 Wesling et al. ......................... .. 427/96
5,074,443 12/1991 Fujii et al. ............................ .. 222/639
5,148,946 9/1992 Mlzuta et a1‘
""" " 222/1
during initial ?lling and priming of the pumping chamber,
Once ?ned and primed, the plunger Causes positive Volume
displacement of liquid from the pumping chamber and out of
- the noZZle,
With
ver yg ood re
eatabilit
and hi- g h ?uid
How
.
. p .
y
5,277,342
1/1994
Dickau et al.
5313 818
5/1994
Sayka etal. .... ..
5’509’954
4/1996 Derian et a1‘
5:564:606 “V1996 Engel __________ __
5,607,581
222/387
73/19.1
95/24
rates, independent of material viscosity, and/or temperature
222/261
or viscosity changes. For re?lling, the plunger is retracted
3/1997 Gerner et al. ...................... .. 210/1982
from a Volume Which corresponds to the Volume of material
re?lled into the internal volume.
FOREIGN PATENT DOCUMENTS
0270207 A1
6/1988
European Pat. Off. .
13 Claims, 2 Drawing Sheets
U.S. Patent
N0v.30, 1999
Sheet 2 of2
52
FIG. 4
5,992,688
62
5,992,688
1
2
It is still another object of the invention to improve upon
DISPENSING METHOD FOR EPOXY
ENCAPSULATION OF INTEGRATED
CIRCUITS
accuracy and performance capacity in the encapsulation of
integrated circuits, by minimiZing adverse affects, such as
doWntime, Which indirectly result from the abrasive ?ller
typically used in tWo component premixed epoxies.
The invention achieves the above-stated objectives by
using a stepped plunger Within a pumping chamber, in
This application is a divisional of prior US. application
Ser. No. 08/828,569, ?led Mar. 31, 1997 now US. Pat. No.
5,927,560.
combination With tWo seals and an open volume
FIELD OF THE INVENTION
This invention relates to precise dispensing of liquid, and
therebetWeen, to actively prime the pumping chamber by
10
removing any air or entrapped bubbles from liquid ?lled into
more particularly to a dispensing pump suitable for dispens
the pumping chamber prior to dispensing. After priming,
ing epoxy to encapsulate integrated circuits.
further movement of the plunger causes a true volume
displacement outWardly from an outlet of the pumping
BACKGROUND OF THE INVENTION
In the dispensing of minute, precise quantities of liquid,
chamber.
15
such as the dispensing of epoxy to encapsulate portions of
integrated circuits, it is important to achieve and maintain
Thus, regardless of the viscosity or the temperature of the
liquid, particularly a tWo-part epoxy used for encapsulation,
the interrelationship among the tWo-step plunger, the seals
high repeatability in the dispensing quantity, notWithstand
ing possible variations in the temperature and/or viscosity of
the liquid. For some applications, the liquid dispensed is
displaced by the advancing plunger equals the volume
and the pumping chamber assures that the volume of ?uid
extremely sensitive to such changes. For instance, in encap
sulating integrated circuits, it is typical to use a tWo com
ponent epoxy Which is premixed by the epoxy manufacturer
and then froZen. The epoxy must then be used Within a feW
days, and in some instances Within several hours.
25
For typical dispensing operations, an epoxy for encapsu
lating of this type Will have a relatively high viscosity.
HoWever, as the temperature changes, the viscosity is also
subject to change. These viscosity variations can affect
dispensing volumes, particularly if a positive volume dis
displaced from the pumping chamber. Stated another Way,
the arrangement of these components assures, after ?lling
and priming of the pumping chamber, that the internal
chamber sealed by the plunger includes only the incom
pressible ?uid to be dispensed.
The plunger may be repeatedly driven into the liquid
material Within the pumping chamber to dispense dots or
discrete streams of material, until the internal chamber needs
to be re?lled. By driving the piston at a controlled rate, the
volume of material dispensed during a shot can be accu
rately determined by the amount of time the piston is drive
placement device is used to dispense the epoxy. For a given
doWnWard, by varying the time that the piston is actuated,
set of dispensing stroke parameters, i.e., displacement
distance, force and rate, the dispensing result Will vary With
variations in viscosity.
different volumes of material may be dispensed. Since the
diameter of the piston is knoWn, then the amount of material
displaced per unit time is also knoWn and the total volume
of material dispensed can easily be calculated. Applicant has
Another problem relates to air or bubble entrapment
35
Within the liquid to be pumped from the pumping device.
Obviously, if a displacement pump is compressing
used a servo driven d.c. motor to provide a high degree of
entrapped air during the displacement strike, the relationship
control and movement of the plunger, enabling program
mable movement of the plunger to dispense a precise desired
betWeen the displacement stroke and the dispensed volume
volume in the range of about 3 Microliters to 500
Will become distorted.
Microliters, or even a thousand Microliters.
Most of the premixed tWo part epoxies used for encap
sulations of this type contain an abrasive ?ll material, such
dispensing pump includes a pumping chamber operatively
According to a preferred embodiment of the invention, a
connected to a supply syringe and a dispensing noZZle via a
as silica This abrasive ?ller can cause undue Wear on
dispensing apparatus, again adversely affecting dispensing
45
and/or resulting excessive doWntime due to the need to
repair or replace Worn components.
While auger pumps have been used in the past to perform
three position, four Way valve, Which is controlled automati
cally to connect the supply syringe With the pumping
chamber during ?ling and priming, and to connect the
pumping chamber With the noZZle during dispensing. The
precise quantity dispensing of this type, the output of a
typical auger pump varies directly With variations in the
viscosity of the dispensed ?uid, the needle siZe and the
supply pressure. While the effect of viscosity changes and
pumping chamber has a surrounding side Wall Which de?nes
an internal volume or chamber for the dispensing liquid,
the ?uid ?oW rate can be minimized With proper pump
includes a stepped plunger, having a relatively large ?rst
With an outlet located at one end thereof. Opposite the outlet
and axially aligned thereWith, the pumping chamber
mum possible mass ?oW rate While maintaining accuracy is
limited.
portion located farther from the outlet than a relatively
smaller second portion. The ?rst portion is circular in
transverse cross sectional shape. The recessed portion may
be circular, but of smaller diameter, or may be of another
SUMMARY OF THE INVENTION
than that of the ?rst portion. A drive mechanism, preferably
design, advanced calibration techniques and manual adjust
ments of the valve operation are required. Thus, the maxi
55
shape so long as the transverse cross sectional area is less
It is an object of the invention to achieve, in liquid
a servo driven d.c. motor, operatively connects to the ?rst
dispensing of relatively high viscosity materials, high
portion of the plunger to reciprocally move the plunger
Within the pumping chamber, along the axis.
The plunger extends axially through tWo seals. The ?rst
seal at all times sealingly engages the ?rst portion of the
plunger. Both seals have central passages therethrough siZed
repeatability of dispensed volume at high ?oW rates, inde
pendent of the viscosity of the material.
It is another object of the invention to improve accuracy
in the dispensing of liquids, by eliminating problems asso
ciated With air entrapment and/or viscosity or temperature
changes in the liquid.
65
to correspond to the inner diameter of the ?rst portion of the
plunger. The second seal resides betWeen the ?rst seal and
5,992,688
3
4
the outlet. It may be supported by an internal shoulder
de?ned by a thicker region of the side Wall. The axial
spacing betWeen the seals de?nes an open volume, and a
With an abrasive ?ller, usually silica. This epoxy is typically
premixed by a supplier and then froZen and shipped to an
end user. It then must be used Within several days, and in
some cases Within several hours. Because of the silica, this
port in the side Wall permits venting of the pumping chamber
to alloW venting of entrapped air during initial ?lling, and
during priming of the pumping chamber as the plunger
epoxy is particularly abrasive for a dispensing apparatus of
this type. Moreover, it is subject to viscosity changes
because of its temperature sensitivity.
moves toWard the outlet to eventually locate the ?rst portion
thereof in contact With the second seal.
Because the plunger and the seals cooperate to remove
The dispensing pump 10 of this invention is a true positive
displacement pump, designed to deliver highly repeatable
quantities of liquid 25 at high ?oW rates, independent of
entrapped air from the internal volume during priming,
leaving only the incompressible ?uid to be dispensed Within
material viscosity. The pumping chamber includes a rigid
the internal volume, further movement of the plunger toWard
the outlet causes true positive displacement of liquid from
side Wall 26 Which de?nes an outlet 28 and an internal
the pumping chamber. Thus, high repeatability in the dis
pensing of minute quantities is achieved independent of
volume 30, With the outlet 28 being located at the vertical
bottom of the internal volume in the preferred embodiment,
although other orientations are also contemplated. The side
temperature or viscosity changes, even at relatively high
Wall 26 is preferably anodiZed aluminum With a surface
?oW rates.
?nish, or any other suitably rigid and compatible material.
The dispensing pump of this invention also improves
upon prior art dispensers relative to its ability to dispense a
The pumping chamber 14 includes a ?rst directional seal 32
and a second directional seal 34 spaced axially therefrom, to
de?ne an open volume 36 therebetWeen. The seals 32, 34 are
viscous epoxy With an abrasive ?ller. More speci?cally, the
epoxy ?oW channels may be made relatively large in siZe so
relatively simple construction and the use of off-the shelf
preferably thermoplastic, such as a polyimide. Aport 38 in
the side Wall 26 of the pumping chamber 14 communicates
With a ?uid outlet line 40, and the ?uid ?oW along the line
replaceable components for the ?uid interconnections helps
40 is controlled by a valve 42.
that the potential for clogging is minimiZed. Also, the
to minimiZe doWntime When it is necessary to replace Worn 25
components. As for the pumping chamber, the side Walls, the
seals and the piston are also readily accessible and fairly
simple to manufacture, and/or assemble at start-up,
A plunger 44 is supported along the center axis of the
pumping chamber 14, extending through the ?rst directional
seal 32, and the second directional seal 34 and in alignment
With the outlet 28 and the noZZle 18. The plunger 44 has a
changeover or upon replacement. All of these features
stepped con?guration With a relatively large diameter ?rst
provide advantages in epoxy encapsulation of integrated
portion 46 and a relatively smaller second portion 48. The
plunger 44 is preferably of stainless steel, although as With
the side Wall 26, it may be of any suitably rigid and
compatible material, such as a machinable plastic. In FIG. 1,
the ?rst portion 46 is located above the second portion 48.
The diameter of the second portion 48 is less than the inner
diameter of the second directional seal 34. Or alternatively,
circuits.
These and other features of the invention Will be more
readily understood in vieW of the folloWing detailed descrip
tion and the draWings.
35
BRIEF DESCRIPTION OF THE DRAWINGS
the transverse cross-sectional dimension of the second por
FIG. 1 is a cross-sectional schematic Which illustrates a
tion 48 is such that it permits ?uid ?oW betWeen the internal
volume 30 and the open volume 36. The outer diameter of
the ?rst portion 48 is at least as great as, and preferably
dispensing pump in accordance With a ?rst preferred
embodiment of the invention, during dispensing.
FIG. 2 is a cross-sectional vieW taken along lines 2—2 of
FIG. 1.
FIG. 3 is a side vieW of a stepped plunger in accordance
With a second preferred embodiment of the invention.
FIG. 4 is a cross-sectional vieW similar to FIG. 1, shoWing
slightly greater than, the internal diameter of the ?rst and the
second directional seals 32, 34, to prevent ?uid How to and
45
initial ?lling of the pumping chamber.
DETAILED DESCRIPTION OF THE DRAWINGS
FIG. 1 shoWs a dispensing pump 10 for high accuracy
dispensing of epoxy for encapsulation of integrated circuits
in accordance With a ?rst preferred embodiment of the
invention. The dispensing pump 10 includes a supply
servo driven motor 45.
syringe, or cartridge 12, for supplying epoxy under pressure,
as by a piston 13 or by air pressure, to an adj acently mounted
pumping chamber 14. The pumping chamber 14 delivers the
liquid to a dispensing noZZle 18, via a valve 16, and
55
therefrom toWard an integrated circuit 20 residing on a
support 22, Which may be moved relative to the noZZle 18,
as shoWn by directional arroWs 24. The cartridge 12 may be
any conventional cartridge style Which supplies the desired
umes for such a cartridge are in the range of about 3 to 180
preferably interconnects With the valve 16 via a Luer lock
interconnection 58, as is Well knoWn and conventional in the
cubic centimeters. Typical air pressures for supplying the
dispensing industry, particularly dispensing With respect to
epoxy to the pumping chamber 14 are in the range of about
As noted above, the epoxy typically used for encapsulat
ing integrated circuits is a premixed tWo component epoxy
The valve 16 is preferably a three position, four Way valve
of the type sold by Medex Inc., under Model No. B1934-1L.
This valve 16 is a four Way rotary valve Which is capable,
via toggle operation of a sWitch 50, of selectively intercon
necting the internal volume 30 With the noZZle 18, or the
internal volume 30 With the supply syringe 12, via a conduit
52 extending therebetWeen.
Preferably, the noZZle 18 includes cylindrical tip 54
residing in a tight ?t Within a plastic casing 56, Which
volume of epoxy and at the desired pressure. Typical vol
50—80 psi.
from the open volume 36 during dispensing.
DoWnWard movement of the stepped plunger 44 through
the liquid 25 contained Within the internal volume 30,
preferably the tWo component epoxy referred to above,
displaces the liquid 25 from the pumping chamber 14 via the
outlet 28, through the valve 16, through the noZZle 18 and
then outWardly therefrom toWard the substrate 20. Move
ment of the plunger 44 is preferably controlled by a dc.
65
medical devices. Similarly, a second Luer lock connection
59 resides betWeen the valve 18 and pumping chamber 14,
and yet a third Luer lock connection 60 interconnects the
5,992,688
5
6
conduit 52 With valve 16, and a fourth Luer lock intercon
nection 62 interconnects the syringe 12 With the conduit 52.
In a preferred manner of moving sWitch 50 of valve 16 to
25 in the supply syringe 12, operation of the pneumatic
cylinder to control movement of the ?tting 64 and the sWitch
50 held thereby, opening and closing of valve 42 for venting
the internal volume 30 during the initial ?lling, and perhaps
most importantly, reciprocal movement of the plunger 44
selectively interconnect the syringe 12 and the pumping
chamber 14, or the pumping chamber and the noZZle 18, the
invention provides a shaped ?tting, or adapter, 64 With an
internal recess Which is complementary in shape to the
sWitch 50 of the valve 16. The ?tting 64 operatively inter
With respect to the pumping chamber 14.
Typically, up to ?fty parts, or even more, may be encap
sulated via a like number of doWnWard movements of the
plunger 44, prior to resuming the re?lling operations. To
connects via a mechanical member 66 to a controllable
actuator of some type, such as a pneumatic cylinder or an 10 re?ll the pumping chamber 14, the valve 16 is closed to
electrical solenoid. Selective control of the actuator causes
interconnect the syringe 12 and the pumping chamber 14,
the ?tting 64, and hence the sWitch 50 held thereby, to toggle
and the plunger 44 is retracted to a position Where the large
cross section 46 of the plunger 44 remains beloW direct seal
34, as shoWn in FIG. 1. The liquid 25 is again driven into the
back and forth betWeen the tWo selected positions to control
?uid ?oW through the valve 16.
FIG. 2 shoWs a side vieW of a plunger 144 in accordance
15
With a second preferred embodiment of the invention,
Wherein the ?rst portion 146 is identical to the ?rst portion
46 of plunger 44 shoWn in FIG. 1. HoWever, the second
portion 148 of plunger 144 differs in cross-sectional
dimension, With four symmetrically arranged open sections
149 extending therealong, as shoWn best in FIG. 3.
In operation of the dispensing pump 10, the cartridge or
syringe 12 ?lled With the premixed tWo-party epoxy is
mounted to the fourth Luer lock 62. With the valve 16 open
so as to permit ?oW betWeen the syringe 12 and the pumping
chamber 14, either the piston 13 is driven or air pressure is
internal volume 30 to re?ll it to a desired level. The volume
of liquid 52 re?lled into internal volume 30 is preferably
controlled so as to match the volume occupied by the
20
plunger 44 prior to retraction. There is no need for priming
after re?lling, only upon initial ?lling With a neW cartridge
12. If desired retraction of plunger 44 and re?lling of liquid
25 from cartridge 12 may occur and be controlled simulta
neously.
In using the invention, applicant has achieved Zero drip
With intermittent dispensing of liquid having a viscosity of
25
one centipoise. The invention is suitable for use With liquids
having a range in viscosity from 1 to 1 M centipoise. The
supplied to the inside of the syringe 12, typically on the
invention is capable achieving accuracy in dispensing with
order of 50 to 80 psi, to cause the epoxy to How through the
How rates ranging from 0.006 cc per second to 1 cc per
second, and With a shot siZe ranging from 0.002 cc to 2 cc
and With an accuracy better than 1%.
conduit 52, through the valve 16 and into the internal
volume 30, preferably ?lling the internal volume 30. If air
pressure is used, the air pressure to the syringe 12 is supplied
30
While a preferred embodiment of the invention has been
via an air supply port (not shoWn) and pressuriZed air supply
described, that embodiment is to be understood as exem
(not shoWn).
plary in nature, since those skilled in the art Would readily
During initial ?ling of the internal volume 30 epoxy, as
shoWn in FIG. 4, the valve 16 remains open betWeen the
35
syringe and the pumping chamber 14, and valve 42 in ?uid
passages of the seals, and the outer shape of the large portion
communication With open volume 36 also remains open, to
enable ?uid to How outWardly from the internal volume 30,
completely ?lling volume 30 With incompressible ?uid.
After the internal volume 30 is ?lled completely, determined
either by the duration of ?lling or visual detection of liquid
25 How out of port 38, the plunger 44 is then moved
doWnWardly to locate ?rst portion 46 Within the second
directional seal 34. This movement of the plunger 44 primes
the pumping chamber 14, to result in an internal volume 30
40
45
55
This dispensing pump 10 is particularly suitable for
encapsulating integrated circuits on a substrate 20, Which is
in turn located on a support 22. This is typically done during
relative movement of the dispensing pump 10 With respect
to the support 22, as indicated by directional arroWs 24. This
relative movement may be affected by mounting the dis
pensing pump on a robot (not shoWn) or by moving the
support past the noZZle 18 in conveyor like fashion.
Preferably, control of the components of the dispensing
pump 10 is coordinated in an automated manner, this control
including the force or the air pressure supplied to the liquid
retracting said plunger to form a ?uid ?oW path betWeen
said internal volume and said passage,
introducing said liquid into said internal volume,
a dc. servo driven motor 45, provides a high degree of
control and accuracy to achieve dispensing of repeatable
We claim:
1. A method of dispensing a liquid from a dispenser
including a pumping chamber having an internal volume
communicating With an outlet and having a plunger mounted
for movement Within a passage in a seal, the method
comprising:
50
through outlet 28. Control of the plunger 44, preferably by
quantities of liquid.
of the plunger need not be circular, so long as a ?uid tight
seal is created therebetWeen. Thus, the disclosed and
described embodiment should be regarded as exemplary in
nature and not limiting in nature. Applicants Wish to be
limited only by the folloWing claims.
completely ?lled With the incompressible epoxy liquid 25,
With no air entrapped therein. The sWitch 50 of the valve 16
is then moved to open the ?uid connection betWeen internal
volume 30 and noZZle 18. Thereafter, further movement of
the plunger 44 toWard the outlet 28 causes positive volume
displacement of ?uid 25 from the internal volume 30
appreciate that a number of variations may be made there
from Without departing from the scope of the invention. For
instance, the transverse cross sectional shape of the central
60
extending said plunger to seal said passage, and
extending said plunger an additional amount to positively
displace at least a portion of the liquid in said internal
volume through said outlet.
2. The method of claim 1, Wherein the liquid is an epoxy
material and the step of extending said plunger an additional
amount further comprises:
displacing said epoxy material onto an electric circuit
component.
3. The method of claim 1 Wherein the plunger further
includes a section of increased cross-sectional dimension
relative to an adjacent section and the step of retracting said
65
plunger further comprises:
disengaging the section of increased cross-sectional
dimension from said seal to form said ?uid ?oW path.
5,992,688
8
7
9. The method of claim 8, further comprising:
selectively controlling movement of the plunger to dis
4. The method of claim 1, wherein the step of introducing
liquid into said internal volume further comprises:
forcing air to escape from the internal volume through
said ?uid ?oW path While ?lling the internal volume
pense in at least one of the folloWing manners: inter
mittent drip dispensing and intermittent stream dis
pensing.
With liquid.
5. The method of claim 1 further comprising:
closing a valve connected betWeen the outlet and the
internal volume prior to ?lling said internal volume
With said liquid.
6. The method of claim 5 further comprising:
opening said valve after said plunger has been extended to
close said passage.
7. The method of claim 1, Wherein the step of extending
said plunger an additional amount further comprises:
10
priming the pumping chamber by moving the plunger
toWard the outlet and into said engaged position to
15
extending said plunger With a servo motor by a discrete
distance corresponding to a desired amount of said
11. The method of claim 8 and further comprising:
venting ?uid Which moves past the ?rst seal from the
internal volume.
12. The method of claim 8 and further comprising:
controlling a valve to operatively connect the pumping
epoxy, comprising:
moving a dispensing pump relative to an integrated circuit
located on a support, the dispensing pump including a
pumping chamber having an internal volume and an
dispensed and bounded, opposite the outlet, by a ?rst
seal and a plunger mounted for reciprocating move
ment in said ?rst seal betWeen an engaged position
preventing ?uid ?oW past said ?rst seal and a disen
gaged position alloWing ?uid ?oW past said ?rst seal;
and
dispensing the epoxy from the outlet of the pumping
chamber toWard the integrated circuit by moving the
plunger toWard the outlet, While maintaining the
plunger in said engaged position.
create a ?uid tight condition in the internal volume so
that further movement of plunger toWard the outlet,
during dispensing, causes positive displacement of
liquid through the outlet.
liquid to be displaced from said outlet.
8. A method of encapsulating integrated circuits With
outlet therefor de?ned by a surrounding side Wall, the
internal volume being ?lled With the epoxy to be
10. The method of claim 8 further comprising:
prior to dispensing, ?lling the internal volume of the
pumping chamber With epoxy from a supply syringe
via a valve, With the plunger in said disengaged posi
tion to permit ?uid ?oW betWeen opposite sides of the
?rst seal;
chamber With the supply syringe during said ?lling and
25
priming, and to operatively connect the pumping cham
ber to a dispensing noZZle during said dispensing.
13. The method of claim 8 Wherein a portion of the
plunger extends through a second seal, said second seal
being spaced from said ?rst seal, on a side opposite the outlet
and further comprising:
maintaining a ?uid tight condition betWeen said portion of
the plunger and said second seal during said
dispensing, ?lling and priming.
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