Frostless interface supercooled VLSI system

A double walled vessel having a styrofoam filling between the double walls internally supports a semiconductor circuit to which is attached at least one flat ribbon cable. The semiconductor circuit is immersed in liquid nitrogen with at least one flat ribbon cable extending to the top lip of the vessel. Carbon conductors are connected to each conductor of the flat ribbon cable and extend to the outer wall of the vessel. Another flat ribbon cable is connected to the carbon conductors and to an electrical connector. A double walled top having a styrofoam filling is secured to the vessel such that the carbon conductors are sealed between the styrofoam filling of the top and the double walled vessel thereby preventing the formation of frost on the flat ribbon cable and connector that is external to the sealed vessel. Various tubings are inserted through the double walled vessel to permit the insertion of liquid nitrogen and the drawing off of gaseous nitrogen.

BACKGROUND OF THE INVENTION 
The present invention is directed to a system for supercooling a 
semiconductor device such as a CMOS VLSI chip for the purpose of 
increasing the speed of the device and for maintaining the interface 
between the VLSI chip and other systems frostless. 
It is well known that for certain electrical conductors the resistance of 
the conductor decreases when the conductor is supercooled, for example, 
towards a temperature of -190: C. A decrease in resistance tends to 
increase the speed at which a signal can travel along the conductor. When 
super cooling temperatures are applied to large scale semiconductor chips 
of the CMOS type increases in the speed of the signal travel are obtained. 
One popular medium used for supercooling semiconductor chips is liquid 
nitrogen. The liquid nitrogen is placed in a vessel with the semiconductor 
chip and electrical leads connected to the circuits on the chip pass 
through the liquid nitrogen and out of the vessel to facilitate connection 
to external electrical systems. 
One problem associated with this arrangement is that frost develops on the 
leads where they exit the vessel and meet with room temperature. This 
frosting causes interference with the connectors that connect the leads to 
external electrical systems and when melted causes water pools in 
proximity to the vessel. Both of these conditions are undesirable. The 
system of the present invention prevents the formation of frost on the 
conductors that exit the vessel housing a supercooled very large scale 
integrated CMOS device. 
SUMMARY OF THE INVENTION 
The present invention is a system for supercooling a VLSI circuit in a 
liquid nitrogen filled vessel and for providing an electrical interface to 
the VLSI circuit from outside of the vessel which interface is maintained 
frost free. 
In a preferred embodiment of the present invention a double walled 
container having a removable top and a styrofoam filling between the 
double walls is partially filled with liquid nitrogen. An integrated 
circuit is electrically connected to one end of a flat ribbon cable and is 
immersed in the liquid nitrogen. The other end of the flat ribbon cable is 
connected to individual carbon conductors. The carbon conductors are in 
turn connected to an electrical connector by means of a second section of 
flat ribbon cable. 
The top of the vessel is clamped to the vessel with the individual carbon 
conductors sandwiched between the styrofoam of the top and the styrofoam 
of the vessel so that no frost develops on the carbon conductors or the 
second section of flat ribbon cable. 
It is therefore a primary object of the present invention to provide a 
frost free system for a supercooled VLSI chip; 
It is another object of the present invention to provide a frostless 
interface for electrical conductors immersed at one end in a supercooled 
environment and at the other end in a nominal environment. 
It is yet another object of the present invention to isolate the 
temperature extremes of electrical conductors by interposing a carbon 
conductor in the electrical conductor at the point of temperature 
transition. 
These and other objects of the present invention will become more apparent 
when taken in conjunction with the following description and drawings 
wherein like characters indicate like parts and which drawings form a part 
of the present disclosure.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, the system 10 for supercooling the semiconductor chip 
is shown comprised of a double walled vessel 12 have an outer wall 14, an 
inner wall 18, and an insulating material 16 filling the void between the 
two walls which insulating material may be styrofoam. A double walled top 
assembly 13 having an outer wall 15, an inner wall 17, and an insulating 
material 16, is attachable to the vessel 12 by means of fasteners 60 which 
connect to an integral flange 64 on the outer wall 15 of the top assembly 
and to the flange 62 which is an integral part of the outer wall 14 of the 
vessel 12. The vessel may be of any particular shape such as cylindrical 
and/or square without detracting from the teaching of the present 
invention. A projecting lip 22 extends inward from the inner wall 18 and 
supports a ceramic platform 20 having openings 32 therethrough to 
facilitate the flow of a liquid 24 such as liquid nitrogen. 
Referring to FIG. 2 in conjunction with FIG. 1, bonded to the platform 20 
is a semi-conductor chip 26, which chip in turn is connected by conductors 
28 to a cable 30 which may be a flat conductor ribbon. The ribbon 30 
extends upward towards the junction of the top assembly 13 and the vessel 
12 to the lip of the inner wall 18. At the approximate location of the lip 
of the inner wall the ribbon 30 is connected to a plurality of carbon 
conductors 50 of low ohmic but relatively high thermal insulating value. 
The carbon conductors 50, in the assembled position, are sandwiched 
between the styrofoam fill of the top assembly and the styrofoam fill of 
the vessel. The carbon conductors 50 perform the transformation from the 
high temperature, relatively speaking, of the exterior of the system to 
the supercooled inner temperature of the vessel generated by the liquid 
nitrogen. The carbon conductors are connected to a continuing strip 52 of 
flat conductor ribbon which ribbon terminates in an electrical connector 
54. The connector 54 is connectable to circuitry and or systems designed 
to interface with the electronics of the chip 26. 
An inlet tube 40 and an outlet tube 42 project through the double walls of 
the vessel 12 and are connected to a supply of cooled liquid nitrogen (no 
shown for purposes of clarity). The liquid nitrogen ingresses into the 
vessel 12 via the tube 40 and can move from the vessel by means of tubing 
42 so that the nitrogen can be returned to its cooling source. A gas vent 
tube 44 is provided near the top portion of the vessel above the level of 
the liquid nitrogen for purposes of collecting gaseous nitrogen and for 
returning the gas to the supply of cooled liquid nitrogen for conversion 
to a liquid. In order to eliminate the formation of frost on the tubes 40, 
42, and 44 leading into and out of the vessel, outer tubes 70, having a 
diameter greater than the tubes they enclose, are positioned on flanged 
portions 72 of the outer vessel wall 14 so as to create an insulating 
space 73. 
The inner wall 18 of the vessel 12 and the inner wall 17 of the top 
assembly 13 may be formed from a ceramic or metallic type material. The 
flat conductor ribbon 30 and the associated ribbon 52 may be a polyemide 
flat ribbon which is electrically connected through embedded wires or 
other electrical conduction means to the semiconductor chip and the carbon 
conductors by either thermal compression or soldering. The carbon 
conductors 50 may be formed from a carbon strip of the type manufactured 
by Omega-Ply of California and/or may be discrete carbon resistors. In the 
preferred embodiment of the invention, the semiconductor chip 26 is a very 
large scale (VLSI) CMOS device. The support assembly 20 may be formed from 
a PCB board material or ceramic. The ceramic material is preferred. 
While there has been shown what is considered to be the preferred 
embodiment of the invention, it will be manifest that many changes and 
modifications may be made therein without departing from the essential 
spirit of the invention. It is intended, therefore, in the annexed claims, 
to cover all such changes and modifications as fall within the true scope 
of the invention.