U.S. patent application number 09/798321 was filed with the patent office on 2002-09-05 for electrohydrodynamicly enhanced micro cooling system for integrated circuits.
Invention is credited to Darabi, Jafar, Ohadi, Michael M..
Application Number | 20020122728 09/798321 |
Document ID | / |
Family ID | 25173108 |
Filed Date | 2002-09-05 |
United States Patent
Application |
20020122728 |
Kind Code |
A1 |
Darabi, Jafar ; et
al. |
September 5, 2002 |
ELECTROHYDRODYNAMICLY ENHANCED MICRO COOLING SYSTEM FOR INTEGRATED
CIRCUITS
Abstract
A cooling system employing Micro Electro Mechanical System
(MEMS) technology and polarization principles to move a cooling
fluid over a surface requiring cooling and further employing
electrohydrodynamic principles for the purpose of enhancing the
heat transfer coefficient between the cooling fluid and the surface
to be cooled.
Inventors: |
Darabi, Jafar; (Laurel,
MD) ; Ohadi, Michael M.; (Columbia, MD) |
Correspondence
Address: |
DANIEL E KRAMER
2009 WOODLAND DRIVE
YARDLEY
PA
19067
US
|
Family ID: |
25173108 |
Appl. No.: |
09/798321 |
Filed: |
March 2, 2001 |
Current U.S.
Class: |
417/48 |
Current CPC
Class: |
H02N 1/008 20130101;
F28D 15/0266 20130101; F28F 13/16 20130101; B01J 2219/00873
20130101 |
Class at
Publication: |
417/48 |
International
Class: |
F04B 037/02 |
Claims
We claim:
1. Micro pump means for moving a cooling fluid over a surface, the
pump comprising at least a first and a second array of electrically
charged substantially parallel linear micro electrodes, the
electrodes of the first and second arrays being alternately
positioned on the surface to form an interleaved array.
2. Pump means as recited in claim 1 further providing electrical
charge means, said means comprising means for applying a non
reversing electromotive potential between the first and second
electrode arrays whereby the first array has a positive electrical
potential with respect to the second and the second array has a
negative electrical potential with respect to the first.
3. Pump means as recited in claim 2, further providing that the
applied electromotive potential is substantially constant.
4. Pump means as recited in claim 2 where the electromotive
potential is sufficiently high to create a polarization effect on
the fluid whereby the fluid is caused to move along the lines of
the electrodes.
5. Pump means as recited in claim 4 further providing enclosing
means for channeling fluid flow along the electrode lines.
6. Pump means as recited in claim 5 further providing that the
surface is positioned so that the direction of the lines of the
linear electrodes is substantially vertical.
7. Pump means as recited in claim 5 further providing that the
surface is positioned so that the direction of the lines of the
linear electrodes and the corresponding direction of fluid flow
lies between vertical and seventy five degrees away from the
vertical.
8. Pump means as recited in claim 5 where the enclosing means
comprises conduit means for confining fluid flow within a distance
of three millimeters (mm) from the electrodes.
9. Pump means as recited in claim 4 further providing that at least
on array is formed of material having a major constituent selected
from the group consisting of Platinum, Gold and Niobium.
10. Pump means as recited in claim 4 further providing that at
least on array is formed of a material having Niobium as a major
constituent.
11. Pump means as recited in claim 5 further providing that the
surface includes a heated portion and an unheated portion an that
the interleaved array extends over both portions.
12. Pump means as recited in claim 11 further providing a fluid
inlet to the confining means positioned to cause flow over the
unheated portion before flow over the heated portion.
13. Pump means as recited in claim 12 further providing a fluid
outlet positioned to receive flow that has traversed at least part
of the heated portion.
14. Pump means as recited in claim 13 further providing that the
fluid is a volatile liquid and evaporates in traversing the heated
portion and further providing that the vapor arising from
evaporation/boiling exits the confining means through the fluid
outlet.
15. Pump means as recited in claim 14 further providing conduit
means external of the pump means for connecting the fluid inlet and
the fluid outlet, thereby creating a substantially closed
circulatory system, and means positioned within the conduit means
for transferring heat from the vapor exiting the fluid outlet,
thereby condensing the vapor to liquid form.
16. Pump means as recited in claim 15 further providing second
micro pump means positioned within the conduit means for improving
fluid circulation within the closed system.
17. Pump means as recited in claim 16 where the circulating fluid
is a mixture of about 50 percent each of nonafluoroisobutylether
and nonafluorobutylether.
18. Pump means as recited in claim 16 where the circulating fluid
is selected from fluids having low electrical conductivity and
dielectric constants in the range of 2 to 100.
19. Pump means as recited in claim 4 further providing an
electrically insulating substrate selected from the group
consisting of silicon, quartz, ceramic and sapphire.
20. Pump means as recited in claim 3 further providing each
electrode has a thickness and a width and a separation distance,
and further providing that the thickness is between 0.3 .mu.m and
10 .mu.m, the width between 2 and 50 .mu.m and the distance between
adjacent electrodes between 2 and 100 .mu.m.
21. Pump means as recited in claim 20 further providing an
electrode thickness of 0.3 .mu.m, a width of 10 .mu.m and a
substantially uniform distance between adjacent electrodes of 20
.mu.m.
22. Pump means as recited in claim 20 further providing that the
distance between electrodes varies over the length of the
interleaved array.
23. Pump means as recited in claim 22 further providing that the
interleaved array includes a first end and a second end, confining
means including an inlet and an outlet for channeling fluid flow
from the array first end to the array second end, and further
providing that the distance between adjacent array electrodes
nearest the fluid inlet is greater than the distance between
adjacent array electrodes nearest the fluid outlet.
Description
PRIORITY CLAIMED
[0001] Priority is claimed based on the following Provisional or
Regular Patent Applications: NONE
BACKGROUND
[0002] Integrated circuits (IC) utilize micro-components that
require electrical energy. Neither the micron size conductors nor
the micro-components are 100 percent efficient. Both convert some
of the electrical energy used in their computations into heat. In
the early versions of these integrated circuits having relatively
few components per unit area, natural convection cooling proved
adequate to limit the operating temperatures to safe values. As
technology allowed packing more components into an integrated
package the heat generated required motor driven fans mounted
directly on the IC packages, thereby providing forced convection
cooling, to control the package temperature. The manufacturers have
even provided finned surface extenders to be mounted to the IC
packages with a heat conducting paste to better dissipate the IC
package heat to the fan forced air stream. All of these heat
dissipation schemes have employed macro-cooling methods to cool
micro components.
[0003] Significant increases in component density and accompanying
heat dissipation rates have acted to raise operating temperatures
of the IC packages to such levels that their operating life can be
endangered and in the alternative to limit the heat dissipation
rates, thereby limiting the ultimate capability of the IC
package.
[0004] The current invention is directed to micro means for sharply
improving the coefficients of heat transfer between the coolant and
the IC and for providing improved means for removing heat generated
by an IC The proposed micro pump and heat exchanger allows present
high density ICs to operate at lower temperature, thereby providing
longer life. The present invention, by providing sharply Improved
flow and heat transfer over the heat dissipation area further has
the capability of allowing future ICs to be manufactured with
higher component densities and to operate at higher heat
dissipation levels without exceeding life threatening component
temperatures.
[0005] This system offers several features including; 1) applying
the electric field directly to the heat transfer surface using MEMS
(Micro Electronic Mechanical Systems) technology to provide ultra
thin liquid films; 2) providing the required pumping action to
bring the working fluid to the heat transfer surface; and 3)
increasing the effective heat transfer coefficient at the heat
transfer surface by thin-film evaporation. Each electrode typically
has a thickness of 0.3 .mu.m to 10 .mu.m and a width of 2 .mu.m to
50 .mu.m The gap between the electrodes depends on the design and
application and may vary over the range from 2 .mu.m to 100
.mu.m.
[0006] A typical fabrication sequence is described below. However,
it is expected that more modern and rapid manufacturing sequences
will be developed or applied to the process to secure the desired
arrangement of the electrodes. Therefore, it is emphasized that the
novelty of the invention lies in the use of the micro-electrode
arrangement to achieve polarization pumping of the cooling and the
application of an electric field through the micro electrodes to
improve the heat transfer coefficients over the heat transfer
area.
[0007] Typical fabrication begins with wafer or substrate
pre-metaliztion cleaning. The substrate is typically quartz but
sapphire or other similar material may be employed. After
cleansing, 300 .ANG. thickness Chromium and 2500 .ANG. thickness
Platinum (1 .ANG.=0.001 .mu.m) is deposited using an e-beam
evaporator. A 1.5 .mu.m, thick layer of photo resist is applied
over the deposited metals followed by a soft bake at 100.degree. C.
Photolithography is employed to create the desired electrode
pattern followed by a hard-bake at 120.degree. C. While Ion
beam-milling was employed, a variety of other etching techniques
such as wet etching and deep reactive e ion etching are
available.
[0008] The Cr/Pt film Is etched to give the heater and electrode
patterns. Following the micro fabrication, the packaging is
performed.
[0009] A preferred cooling fluid suitable for use in this invention
mixture of about 50 percent each of nonafluoroisobutylether and
nonafluorobutylether offered by 3M Company located in St. Paul
Minn. 1 800 364-3577) under the trade name HFE-7100 (dielectric
constant k=7.4). This fluid has a typical boiling point at
atmospheric pressure of 60.degree. C. (.about.140.degree. F.) and a
viscosity of 0.23 CPS at 23.degree. C. (73.4.degree. F.). Among
other useable fluids are those which have low electrical
conductivity and dielectric constants in the range of 2 to 100.
Examples of these are deionized (DI) water (k=78.5) HFC-134a
(k=9.5), L-13791 (k=7.39) and methoxy nonafluorobuteane
(C.sub.4F.sub.9OCH.sub.3).
PRIOR ART:
[0010] The use of the electrohydrodynarmic technique for
micro-scale fluid pumping has been investigated by a number of
researchers over the past half decade (Barrt et al., 1990; Richter
et al., 1991; Fuhr et al., 1992; Fuhr et al., 1994; Cho and Kim,
1995; and Ahn and Kim, 1997).
[0011] Bart discloses and EHD pumping principle employing a
traveling electrical wave or charge imposed between electrodes
positioned in a substantially parallel array whereby a
non-electrically conducting fluid is moved transverse to the
electrodes by a sinusoidally applied voltage. Bart points our that
his principle works only if the electrodes are freely suspended
with in the fluid to be pumped and will not work if the electrodes
are positioned against the surface to be cooled
[0012] Richter et al. (1991) demonstratede a micro-machined
ion-drag EHD pump consisting of pairs of facing permeable or
perforated substantially planar grids through which the pumped
fluid moves. Richter displays an array of pairs for increasing the
pumping head. Richter points out (p. 160, col. 1) that the
polarization or `dielectrophoretic` force "cannot lead to a
permanent fluid motion for DC fields . . ." Further, none of
Richter's grids are in direct contact with any surface to be
cooled.
[0013] Fuhr (1992) employs a grid of micro electrodes applied to a
surface but teaches a single phase or poly-phase electrical
alternating potential applied to his electrodes. Further, Fuhr's
pumped fluid moves transversely to the electrodes.
[0014] Fuhr (1994) again teaches a traveling wave pumping design
and suggests that a square wave format is superior to sinusoidal
wave format. He further points out that traveling wave pumping
principles require that the fluid pumped exhibit a gradient in the
properties of electrical conductivity or permittivity, a
characteristic not required by the present invention.
[0015] Choi (1995) teaches flow direction that is transverse to the
electrode direction and the use of six phase AC as the driving
potential.
[0016] Ahn (1997) teaches an ion-drag principle where the fluid
flow is transverse the linear direction of the
micro-electrodes.
[0017] The present invention is based on a polarization pumping
principle. No previous work was found that addressed the use of EHD
pumping based on polarization principles.
SUMMARY OF THE INVENTION
[0018] The invention discloses a micro pump for moving a cooling
fluid over a heated surface to be cooled. The pump comprises an
array of substantially parallel linear micro electrodes positioned
on the hot surface. A conduit is provided enclosing the array and
positioned to cause flow parallel to the direction of the
electrodes. The conduit has an interior periphery including the hot
electrode bearing surface. The electrodes are electrically
connected in at least two groups and a voltage source is employed
for applying a non reversing electromotive force between the
electrode groups.
Objects and Advantages
[0019] An object of the invention is to provide low cost, easily
applied means for circulating, without moving parts, a cooling
fluid in heat transfer relation to a small surface requiring
cooling.
[0020] A further object is to provide such means employing
micro-electrodes that can be applied to the surface itself.
[0021] A further object is to provide such means that utilize fluid
polarization principles.
[0022] A further object is to provide such means that require
unusually small amounts of electrical power.
[0023] A further object is to provide such means that require only
direct current energization and do not require single or
multi-phase alternating currents for electrode energization.
[0024] A further object is to provide such circulating or pumping
means for a fluid that evaporates on contact with the surface being
cooled.
[0025] A further object is to provide such circulating means that
includes means for applying an electric field directly to the
surface being cooled, thereby improving the heat transfer
coefficient between the cooling fluid and the surface.
[0026] A further object is to provide an active thin film
evaporation and cooling process.
[0027] A further object is to deploy the pumping means over the
cooled surface and over an adjacent surface and where the means for
applying the electric field to the cooled surface is an extension
of the micro-electrodes that comprise the pump.
[0028] A further object is to provide such circulating means to a
surface positioned at an angle to the horizontal and especially
where the fluid moves from a lower position on the surface to a
higher position.
[0029] A further object is to position the cooled surface at a
right angle to the horizontal.
[0030] A further object is to employ a closed circulating system
for the fluid circulated.
[0031] A still further object is to employ a volatile liquid as the
fluid circulated and to deploy an externally cooled condenser to
condense vapor generated at the cooled surface to the liquid state
for the reuse at the cooled surface.
[0032] A further object is to provide `gravity` circulating means
for returning the condensed vapor to the surface.
[0033] A further object is to employ a second pump for facilitaing
the return of liquid from the condenser to the cooled surface.
[0034] A further object is to employ the principle of
micro-electro-mechanical systems or MEMS to achieve the above
objects.
[0035] Other equally important objects and objectives will be noted
as the detailed exposition of the construction and usage of the
invention is perused in the text below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] FIG. 1 shows a side elevation of a pump and heat exchanger
of the invention in heat transfer relationship to a heat producing
integrated circuit package.
[0037] FIG. 2 is a cross-sectional view 2 of device of FIG. 1
illustrating the gross internal electrode layout of the pump-heat
exchanger of the invention.
[0038] FIG. 3 is cross section 3 of the device of FIG. 1 showing an
end view of the pump-heat exchanger of FIG. 1.
[0039] FIG. 4 illustrates, in gross, the electrode positioning
within the flow channel.
[0040] FIG. 5 shows a pump-heat exchanger of the invention combined
with a heat producing integrated circuit package.
[0041] FIG. 6 is a plan view of the pump-heat exchange assembly
showing the hidden electrodes
[0042] FIG. 7 is a highly enlarged cross section of the electrodes
and their enclosure including typical electrode spacings and
dimensions.
[0043] FIG. 8 shows the angular limits of effective performance of
the assembly.
[0044] FIGS. 9 and 10 show details of variations in electrode shape
and spacing at the pump inlet and outlet.
[0045] FIG. 11 shows one version of a potential cooling circuit
employing a secondary external pump.
DETAILED DESCRIPTION OF THE INVENTION
[0046] FIG. 1 is a side elevation of an Integrated Circuit assembly
(IC) in a package 20 formed in a enclosure 24 and having a
multiplicity of electrically connecting pins 22 for providing power
and information to the IC from a computer connected socket and for
withdrawing from the IC information processed by it. In the process
of performing its information or power processing function, heat is
generated by the IC sealed within the enclosure 24 and the external
surfaces of the IC 24 become hot.
[0047] The cooling system assembly of the invention 26 is thermally
connected to the available hot surface of the IC package 24 on the
package side opposite its pins 22. Typically the thermal connection
is made by coating the surfaces to be thermally connected with a
heat conducting grease and clamping or otherwise securing together
(clamping means not shown) the IC 24 to be cooled and the cooling
device 26, thereby forming a mechanical and thermal interface
29.
[0048] The cooling unit 26 has a sapphire substrate 28. Other
materials may be employed for substrates including ceramic, single
crystal quartz or silicon. The primary substrate requirements are
low electrical conductivity, rigidity and high thermal
conductivity. On the surface 40 of the substrate 28 of the cooling
unit 26 there are positioned a multiplicity of parallel
micro-electrodes 42 and 44 (FIG. 2) to be described.
[0049] An enclosure 30 is provided for channeling cooling fluid
over the micro-electrodes 42, 44. The enclosure 30 is provided with
a fluid inlet 38 and a fluid outlet 36. Then enclosure 30 has
enclosing portions or walls that define a conduit having an
internal periphery that includes the substrate surface on which
micro electrodes 42, 44 are positioned. Each electrode 42, 44 has a
direction, that direction being the direction of a straight line
centrally positioned on the electrode and traversing it from end to
end. (See also FIG. 2) While the electrodes here are described and
shown as being straight, they are well adapted to being positioned
in a curved or cylindrical surface and the description should be
understood to apply to each surface to which such an array could be
applied whether flat, curved, cylindrical, convex or concave. In a
preferred mode, the substrate 28 is positioned so the direction of
the micro electrodes is substantially vertical, that is at an angle
62 of about 90 degrees to the horizontal. It is intended that the
terms vertical means "positioned at an approximated angle of 90
degrees to a plane defined by the surface of a quiescent body of
liquid." Further discussion of this angle 62 will be found in
connection with FIG. 8.
[0050] FIG. 1 displays two sectioning lines: 2-2 refers to a
section shown in FIG. 2; 3-3 refers to a section shown in FIG.
3.
[0051] Referring now to FIG. 2 which is the section 2-2 of FIG. 1,
there are displayed positioned on and fastened to the surface 40 of
substrate 26, tow separate arrays of micro electrodes; the
nominally negative array having tie bar 48 and having connected
thereto a series of micro elements 42, and the nominally positive
array having tie bar 46 and having connected thereto a series of
micro elements 44. The micro elements 42 and 44 are positioned in
an interleaved fashion so that the micro elements 42 alternate with
the micro elements 44. While the positive tie bar 46 and the
negative tie bar 48 are positioned at opposite ends of the
interleaved array, it is the clear intent of the inventors that tie
bars can be positioned wherever convenient, even at the same end of
the interleaved array, laying one on top of the other and each
insulated from the other.
[0052] Referring again to FIG. 2 there is shown in cross section
the enclosure 30, substrate 28 on which the array is positioned and
electrical leads 34 and 32, each connecting to its respective tie
bar 46 and 48, whereby an appropriate electrical potential may be
applied to the tie bars and their respective interleaved micro
electrodes. In one typical construction the width of substrate 28,
measured across the face of the array of micro electrodes is about
10 millimeters (mm) and the height measured from the end adjacent
tie bar 46 to the end adjacent tie bar 48 is about 15 mm and the
actual measurements of the interleaved micro electrode array
positioned thereon, correspondingly smaller. Hidden line 20
identifies the edge of the IC assembly intended to be cooled.
[0053] The electrical potential needed to cause polarization of the
preferred fluid depends, in part on the formation of the micro
electrodes. However, a typical voltage is in the range of 50 to 200
V. While a uniform, substantially non-varying voltage performs
well, it is within the scope of this disclosure that the voltage
may be caused to vary while maintaining the same relative polarity
between the electrodes. The voltage variation may be in the form of
an impressed sine wave, a square wave or some other format.
Further, a variation having a defined frequency such as 20 Hertz
(Hz) or 60 Hz or a much higher frequency such as 1000 Hz may be
preferred.
[0054] FIG. 3 is a cross section 3-3 of the structure of FIG. 1.
FIG. 3 shows IC package 20 having casing 24 and pins 22 for
providing information input and output and power input to the IC 21
kernel itself. It is the IC 21 kernel in which the heat generating
micro electronics are located an which is sought to be effectively
cooled by the micro pump and cooling unit 26 of the invention. As
in FIG. 1, the heat transfer interface 29 between heat producing IC
package 20 and the micropump--heat exchanger of the invention 26 is
shown. On the surface 40 of substrate 28 of the pump--heat
exchanger 25 are positioned the individual micro electrodes 42, 44
and one (34) of the two electrical connections required for
actuating the micro pump. Enclosure 30 is shown providing a flow
channel for cooling fluid, along with one 36 of its two outlet
connections. In FIG. 3 the scale is too small to clearly identify
the individual micro electrodes, but additional section 4-4 and
FIG. 7, provide expanded views.
[0055] FIG. 4 is the oval section of FIG. 3. This section clearly
shows the relative relations of the micro electrodes 40 and their
specific interleaved identities 42 and 44 on substrate 28 and
within flow enclosure 30.
[0056] In FIG. 5 there is shown a construction where a single
substrate 50 provides a base for the micro electrodes within flow
enclosure 30 and its fluid inlet 38 and outlet 36, and pins 22 for
supplying and retrieving digital information and power to the IC
kernel 21, not shown. Further pins 52 and 54 serve to supply the
EMF required by the pump micro electrode assembly positioned within
flow enclosure 30, thereby enabling a single integrally designed
and constructed package to perform both functions.
[0057] FIG. 5 is a plan view of the construction of FIG. 2 showing
the interleaved micro electrodes 42 and 44, the tie bars 46 and 48,
their external electrical connections 32 and 34 and the flow
enclosure 30 with its inlet connection 38 and outlet connection 36,
all positioned on substrate 28. Hidden line 20 identifies the edge
of the IC assembly intended to be cooled.
[0058] FIG. 7 shows a greatly enlarged cross section of a portion
of the interleaved array of micro electrodes 42, 44. These are
positioned on surface 28S of substrate 28 and are enclosed by flow
enclosure 30 with its connection 36. The wall of the flow enclosure
typically is spaced a distance 31 from the substrate and the micro
electrodes. Distance 31 is typically about 3 mm, although, for
different fluids and pumping requirements, other dimensions 31 can
be employed.
[0059] In one preferred embodiment, micro electrodes 42 and 44 each
have a width dimension 56, 60 of 10 .mu.m and a thickness 43, 61 of
1 .mu.m. In their interleaved array the alternating polarity micro
electrodes are spaced 20 .mu.m apart. In other embodiments adapted
for different heat transfer rates or different cooling fluids,
other dimensions may be preferred. In one preferred embodiment the
micro electrodes are formed of Gold or Platinum. In other
embodiments, Niobium or a Niobium rich alloy is employed for micro
electrodes.
[0060] In FIG. 8 the substrate 28 bearing the micro electrodes of
the invention is so positioned that the primary direction of the
micro electrodes 40 is at a right angle 62 to the horizontal. While
the pumping action on the cooling fluid that enters inlet 38 is
effective without reference to the electrode direction, the pumping
action is most effective when the electrodes cause flow in a
substantially upward direction along the direction or axis of the
micro electrodes. A preferred maximum deviation of the angle 78 of
the assembly and the enclosed micro electrodes from the vertical is
about 75 degrees.
[0061] FIG. 9 and 10 are greatly enlarged sections of the
structures illustrated in FIG. 2. In FIG. 9 there is shown micro
element 64 whose width dimension varies linearly over its length so
that the spacing between it and its adjacent micro electrode 44, or
electrode of opposite electrical polarity, is reduced from its
initial dimension 76I (not shown) to a final spacing dimension of
76F. In a preferred embodiment the dimension 76F is 0.833 of the
initial dimension 76I. It is intended that this reduction in flow
width and area between adjacent electrodes in the direction of flow
be employed to intensify the polarization effect on the fluid
remaining within the array in liquid form, as evaporation of the
liquid cooling fluid occurs during the cooling process. In other
embodiments, the width dimension varies in a non-linear manner in
order to best conform with the characteristics of the cooling fluid
and the rate of its evaporation in the cooling process. The
distance 74 between the end of the electrode 64 and the tie bar 46
of opposite polarity is typically three times the initial electrode
spacing 76I. Initial electrode spacings may vary over the range of
2 to 100 .mu.m depending on the cooling fluid employed. The above
preferred dimensions have been found to be satisfactory for the 50
percent mixture of nonafluoro-isobutylether and a
nonafluoro-butylether offered by 3M Company located in St. Paul
Minn. (1 800 364-3577) under the trade name HFE-7100. This fluid
has a typical boiling point at atmospheric pressure of 60.degree.
C. (.about.140.degree. F.) and a viscosity of 0.23 CPS at
23.degree. C. (73.4.degree. F.). Among other useable fluids are
pure (DI) water, HFC-134a and L-13791 and other fluids having low
electrical conductivity and dielectric constants in the range of 2
to 100.
[0062] In FIG. 10 a similar variation in the width of electrode 66
is shown where the flow within the micro pump is in a downward
direction. There the spacing 70F is reduced to a fraction,
typically 83.3 percent of its initial 70I spacing dimension.
[0063] FIG. 11 displays the outline of a complete cooling system
for the IC to be cooled. The combined IC/micro cooling system has
the micro electrode array positioned under enclosure 30 and on
substrate 50. Enclosure outlet 36 is connected by conduit 80 to
condenser 82. While no cooling medium is show affecting condenser
82, either air or liquid can be applied for this purpose. The
condenser outlet conduit 84, 88 may be connected directly to inlet
38 of the micro heat exchanger assembly of the invention. However,
where higher flows or where conduit flow resistance is encountered,
an auxiliary micro electronic pump may be connected between
conduits 84 and 88 to increase the head available for flow. It
should be clearly understood that the principle illustrated in FIG.
11 applies equally well to the structures of figures other than
that of FIG. 5 which is shown here in FIG. 11 for simplicity
only.
[0064] From the foregoing description, it can be seen that the
present invention comprises an advanced and unobvious construction
for making and using a micro pump for pumping a fluid and an
associated micro heat exchanger for cooling integrated circuits and
other small heat generators. It will be appreciated by those
skilled in the art that changes could be made to the embodiments
described in the foregoing description without departing from the
broad inventive concept thereof. It is understood, therefore, that
this invention is not limited to the particular embodiment or
embodiments disclosed, but is intended to cover all modifications
and elements and their equivalents that are within the scope and
spirit of the invention as defined by the appended claims.
* * * * *