Thermal electric cooling system and method

Thermal electric liquid cooling system having a tank for containing the liquid. A cooling plate is secured to the tank and forms a part of the tank. The cooling plate is formed of a heat conductive material and has first and second surfaces with the first surface in contact with the liquid in the tank. A plurality of thermal electric modules are in contact with the second surface of the cooling plate. A cooling manifold is secured to the cooling plate and is in engagement with the thermal electric cooling devices and serves to sandwich the thermal electric cooling modules between the cooling plate and the cooling manifold. Means is provided for supplying a liquid coolant to the cooling manifold to withdraw heat from the cooling manifold.

This invention relates to a thermal electric cooling system for liquids, 
and more particularly to such a system which is a solid-state product CFC 
free. 
In U.S. Pat. No. 5,029,445 issued on Jul. 9, 1991 there is disclosed a 
thermal electric cooling system for liquids which incorporates muffin fans 
and a pump motor. It has been found in certain applications that the 
thermal electric cooling system disclosed in U.S. Pat. No. 5,029,445 is 
too bulky and is objectionable on some applications because of the fan 
noise and particle generation. There is therefore a need for a new and 
improved thermal electric cooling system. 
In general, it is an object of the present invention to provide a thermal 
electric cooling system which is relatively compact and a method for 
operating the same. 
Another object of the invention is to provide a system of the above 
character which is self-contained and can provide heating and chilling. 
Another object of the invention is to provide a system of the above 
character which eliminates the need for muffin fans. 
Another object of the invention is to provide a system of the above 
character in which the thermal electronics are utilized to transfer 
cooling to an internal heat exchanger. 
Another object of the invention is to provide a system of the above 
character which does not generate particles. 
Another object of the invention is to provide a system of the above 
character which can be utilized in Class 10 to Class 1 cleanrooms. 
Another object of the invention is to provide a system of the above 
character in which heat is removed by water through a water jacket. 
Another object of the invention is to provide a system of the above 
character which is reliable and efficient.

In general the thermal electric liquid cooling system of the present 
invention consists of a tank for containing the liquid. A cooling plate is 
secured to the tank and forms a part of the tank. The cooling plate is 
formed of a heat conductive material and has first and second surfaces 
with the first surface in contact with the liquid in the tank. A plurality 
of thermal electric modules are in contact with the second surface of the 
cooling plate. A cooling manifold is secured to the cooling plate and is 
in engagement with the thermal electric cooling devices and serves to 
sandwich the thermal electric cooling modules between the cooling plate 
and the cooling manifold. Means is provided for supplying a liquid coolant 
to the cooling manifold to withdraw heat from the cooling manifold. 
More in particular, the thermal electric cooling system 11 of the present 
invention as shown in FIG. 1 consists of a thermal electric cooler 12 
which is shown in detail in FIGS. 4, 5 and 6. As shown therein, the 
thermal electric cooler 12 consists of an upper tank 16 and a lower tank 
17. The upper tank 16 is generally rectangular in configuration and is 
provided with spaced apart parallel side walls 18 and 19, and spaced apart 
end walls 21 and 22 which adjoin the side walls 18 and 19 at right angles 
thereto. A flange 24 which is secured to the lower extremities of the side 
walls 18 and 19 and the end walls 21 and 22 and extend horizontally 
therefrom. 
The lower tank 17 also has a rectangular configuration and is provided with 
spaced apart parallel side walls 26 and 27, and spaced apart parallel end 
walls 28 and 29 which adjoin the side walls 26 and 27 at right angles 
thereto. It is also provided with a bottom wall 31. A flange 32 extends 
around the upper extremities of the side walls 26 and 27 and end walls 28 
and 29 and extends at right angles or horizontally therefrom. A thermal 
electric unit or plate 36 is provided which is formed of a suitable 
conducting metal such as aluminum which is generally planar and is 
provided with first and second planar parallel surfaces 37 and 38. The 
plate 36 has generally the same dimensions as the flanges 24 and 32. A 
gasket 41 is disposed between the flange 24 and the second surface 38 of 
the plate 36 to form a fluid-tight seal between the plate 36 and the 
flange 24 and for the upper tank 16. The upper tank 16, the gasket 41, the 
thermal electric unit or plate 36 and lower tank 17 are secured into a 
unitary assembly by bolts 42 extending through the flanges 24 and 32 and 
the gasket 41 and the plate 36. 
A plurality of spaced apart parallel vertically upstanding fins 46 are 
mounted on the plate 36 and are also formed of a suitable conducting 
material as aluminum. The fins 46 can be formed of separate elements and 
then bonded to the plate 36, or, alternatively, the plate 36 with the 
upstanding fins 46 can be formed integral in a suitable manner such as by 
forming both the plate and the fins from an aluminum extrusion. As can be 
seen from FIG. 5, the fins 46 extend upwardly into the upper tank 16 and 
are adapted to come into contact with any liquid placed in the upper tank 
16. Thus the fins 46 with the associated plate 36 serve as a heat sink. 
The thermal electric unit 34 also includes a plurality of spaced apart 
thermal electric cooler cells 48 of a suitable size, as for example 
approximately 11/4" by 11/4" with a thickness of approximately 1/8". These 
cells or modules 48 are of a conventional type manufactured by Marlow 
Industries, Inc., at 10451 Vista Park Road, Dallas, Tex., 75232. As shown 
in FIG. 6, twelve of such cells or modules 48 have been provided and 
arranged with six in two spaced apart parallel rows on the bottom or first 
surface of the plate 37 and are held in intimate contact therewith and are 
sandwiched between the bottom or second surface 38 of plate 36 and the 
upper or first surface 51 of a water jacket or manifold 52. 
The water jacket or manifold 52 is formed of a suitable conducting material 
such as aluminum and is secured to the plate 36 by suitable means such as 
screws 54. The manifold 52 is provided with a serpentine flow passage 56 
which extends through the manifold as shown in dotted lines in FIG. 6 and 
is in communication with an inlet fitting 57 and an outlet fitting 58 
mounted on one end of the manifold facing the end wall 28 of the lower 
tank 17. The serpentine flow passage provides spaced parallel passages 
56a, 56b, 56c and 56d lying adjacent each of the two rows of thermal 
electric cells or modules 48 as shown particularly in FIG. 6. The passages 
56a and 56b are interconnected by a passage 56e and passages 56c and 56d 
are interconnected by a passage 56f. Passages 56b and 56c are 
interconnected by a U 59. The inlet and outlet fittings 57 and 58 are 
connected to piping 60 and 61 for supplying a suitable cooling liquid such 
as water to the serpentine flow passage 56 within the manifold 52. 
An inlet fitting 63 is provided on the front end wall 21 of the upper tank 
16 and an outlet fitting 64 is provided in the side wall 19 of the upper 
tank 16. A large clean-out opening 66 is also provided in the top wall 33 
and has a removable threaded cap 67 mounted thereon. Another fitting 68 is 
also provided in the top wall 23 and there is provided a valve (not shown) 
mounted therein to permit the bleeding of air into and out of the upper 
tank 16 as the same is being filled with liquid or liquid is being 
withdrawn therefrom. A rod-like or cylindrical cartridge electric heater 
71 is mounted in the end wall and is provided for heating the liquid in 
the upper tank 16 as hereinafter described. A temperature switch 72 and a 
liquid level float switch 73 are also mounted in the end wall 22. 
A compartment 76 is mounted on the end 22 of the upper tank 16 and is 
provided for making electrical connections to the heater 71, the 
temperature sensor 72 and the liquid level switch 73 as well as for making 
connections to the thermal electric unit 34 with the cells or modules 48 
therein. 
As shown in FIG. 1, the lines 59 and 61 connected to the manifold 52 are 
connected to a heat exchanger and a city water supply in a conventional 
manner. The compartment 76 is connected by a control cable 77 connector to 
a controller 78. 
The inlet fitting 63 is connected by a line or conduit 81 to a fitting 82 
provided on a wafer chuck 83. An outlet 64 on the wafer chuck is connected 
by a line 86 to the outlet 87 of a pump 88. Inlet 89 to the pump 81 is 
connected by a line 91 to the outlet 64 on the upper tank 16. 
The operation and use of the system shown in FIG. 1 may now be briefly 
described as follows. Let it be assumed that wafers (not shown) are 
transported from a hot zone onto the wafer chuck 83. The wafer chuck 
serves to cool the wafers down to a predetermined desired temperature plus 
or minus 1/10th of a degree. The upper tank 16 is filled with the cooling 
liquid, as for example distilled water, which is cooled to a desired 
temperature by the thermal electric unit 34 under the control of the 
controller 78. The controller 78 can be of a conventional type, as for 
example a proportional plus integral plus derivative type of controller. 
Such controller responds to the rate at which the measurement is changing 
even though the actual error is still small. When the temperature 
measurement starts to change, derivative action generates an immediate 
response proportional to its rate of change to provide a precision 
temperature control for the liquid within the thermal electric cooler 12 
and to thereby provide a liquid at a predetermined temperature to the 
wafer chuck 83. In the operation of the system, the thermal electric cells 
or modules 48 are always operating under the same polarity so that the 
thermal electric cells or modules 48 are always cooling and are not used 
for heating. If heat is needed to maintain the desired temperature, the 
heat is supplied from the cartridge heater 71 to provide the constant 
temperature under the control of the controller 78. Since polarity is not 
reversed on the thermal electric cells or modules 48, improved reliability 
is obtained from the thermal electric cells or modules 48. 
Another system 101 shown in FIG. 2 utilizes the thermal electric cooler 12 
for cooling a developer in a developer cooling tank 102 which is provided 
with a coil 103 which is helically wound into a cylindrical shape. The 
coil 103 is connected to the lines 81 and 86 of a suitable size such as 1" 
through tees 104 to the cooler 12 through the pump 88 so that a cooling 
liquid is pumped through the coil 103. The developer to be cooled is 
supplied from a tank (not shown) to the coil 103 through a line 106 of a 
suitable size as for example 1/4" through a plug 107 mounted in one leg of 
the tee 104. The line 106 extends through the coil 103 and is connected to 
a line 108 which exits through the other tee 104 and a plug 107 is 
provided therein and is connected to the wafer process station (not shown) 
for use therein. In this manner it can be seen that heat or cold can be 
transferred from the liquid within the lines 81 and 86 under the control 
of the controller 78 for the thermal electric cooler 12 to cool or heat 
the developer flowing internally of lines 106 and 108 within the coil 103 
in which the cooling liquid from the thermal electric cooler 12 is 
flowing. In this way, a developer can be maintained at a predetermined 
desired temperature. 
From the foregoing it can be seen that thermal electric coolers of the 
present invention are ideally suited to a wide variety of systems because 
of their size, wide operating range, low power requirements and high 
reliability. The thermal electric coolers in the systems of the present 
invention are solid state with no moving parts. Since there are no moving 
parts, extreme reliability is obtained which reduces downtime. They are 
environmentally more desirable because they do not use conventional 
refrigerants such as Freon and CFCs (chlorofluorocarbons). They also do 
not use corrosive liquids and gases. There are no compressor noises or 
particle generating fans. 
By way of example, thermal electric coolers made in accordance with the 
present invention have had the ability to cool and heat the tank contents 
from 40.degree. C. to 15.degree. C. and keep a precise temperature control 
with a tolerance of plus or minus 0.degree. C. The physical size for one 
cooler provides a small footprint, as for example 101/2" wide, 16" long 
and 11" high.