Abstract:
A burn-in testing cooling system including an evaporator comprising an upright tubular body having an interior surface and a central passageway with a wick disposed on the interior surface of the body that defines the central passageway. A base seals off the central passageway, with an inlet port arranged in flow communication with an upper portion of the central passageway and an outlet port arranged in flow communication with a lower portion of the central passageway. A coolant is disposed within the central passageway. A condenser is arranged in flow communication with the evaporator.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Patent Application No. 60/499,483, filed Sep. 2, 2003 and U.S. Provisional Patent Application No. 60/502,125, filed Sep. 11, 2003. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention generally relates to thermal management systems for semiconductor devices and, more particularly, to systems for cooling such semiconductor devices during burn-in testing.  
       BACKGROUND OF THE INVENTION  
       [0003]     In the conventional manufacture of semiconductor devices, semiconductor wafers are first produced in batches. Each semiconductor wafer can contain many individual electronic devices or electronic circuits, which are known as dies. Each die is electrically tested by connecting it to special purpose test equipment. Probes, which are connected to the test equipment, are brought into contact with the die to be tested. This generally occurs at a prober station, which conventionally includes a platform arranged for supporting the wafer. It is important to test each individual circuit chip die while it is still attached in a wafer, and to also test the individual integrated circuit devices once they have been packaged for their intended use. In many testing applications, the tests must be performed at elevated temperatures which, if not regulated, could cause damage to the chip during testing. Accordingly, automated test systems are commonly outfitted with temperature control systems which can control the temperature of a semiconductor wafer or packaged integrated circuit under test.  
         [0004]     For example, and referring to  FIGS. 1 and 2 , a semiconductor device test system A often includes a temperature-controlled semiconductor package support platform B that is mounted on a prober stage C of prober station D. A top surface E of the device support platform B supports a semiconductor device F and incorporates conventional vacuum line openings and grooves G facilitating secure holding of semiconductor device F in position on top surface E of device support platform B. A system controller and heater power source H are provided to control the temperature of device support platform B. A cooling system I is provided to help regulate the temperature of device support platform B. A user interface is provided in the form of a touch-screen display J where, for example, a desired temperature for the top of support platform B can be input. Temperature controlled systems for testing semiconductor devices during burn-in are well known, as disclosed in the following patents which are hereby incorporated herein by reference: U.S. Pat. Nos. 4,037,830, 4,213,698, RE31053, 4,551,192, 4,609,037, 4,784,213, 5,001,423, 5,084,671, 5,382,311, 5,383,971, 5,435,379, 5,458,687, 5,460,684, 5,474,877, 5,478,609, 5,534,073, 5,588,827, 5,610,529, 5,663,653, 5,721,090, 5,730,803, 5,738,165, 5,762,714, 5,820,723, 5,830,808, 5,885,353, 5,904,776, 5,904,779, 5,958,140, 6,032,724, 6,037,793, 6,073,681, 6,245,202, 6,313,649, 6,394,797, 6,471,913, 6,583,638, and 6,771,086.  
         [0005]     In many cases such support platforms are required to be able to both heat and cool the device. Many types of temperature-controlled support platforms are known and are widely available. Cooling is very often provided by a heat sink that is cooled by a recirculating fluid, or in other designs by passing a fluid through the support platform without recirculating it. The fluid can be a liquid or a gas, usually air in the latter case. The liquid or air can be chilled for greater cooling effect in passing through the support platform, and can be recirculated for greater efficiency. A support platform cooled by means of a fluid chilled to a temperature below ambient temperature enables device probing at temperatures below ambient. In general, conventional heat-sink designs often incorporate simple cooling channels cross-drilled and capped in the support platform.  
         [0006]     None of the foregoing systems and methods have been found to be completely satisfactory.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention provides a cooling system for a semiconductor device including an evaporator comprising an upright tubular body having an interior surface and a central passageway with a wick disposed on the interior surface of the body that defines the central passageway. A base seals off the central passageway, with an inlet port arranged in flow communication with an upper portion of the central passageway and an outlet port arranged in flow communication with a lower portion of the central passageway. A coolant is disposed within the central passageway. A condenser is arranged in flow communication with the evaporator.  
         [0008]     In another embodiment of the invention, a cooling system for a plurality of semiconductor devices is provided including a plurality of evaporators. Each evaporator includes an upright tubular body having an interior surface and a central passageway with a wick disposed on the interior surface of the body that defines the central passageway. A base seals off each of the central passageways, and also includes an outlet port arranged in flow communication with an upper portion of each of the central passageways and an inlet port arranged in flow communication with a lower portion of each of the central passageways. A coolant is disposed within each of the central passageways. A condenser is arranged in flow communication with each of the evaporators.  
         [0009]     In yet another embodiment of the invention, a cooling system for a plurality of semiconductor devices is provided including a plurality of evaporators. Each evaporator includes an upright tubular body having an interior surface and a central passageway with a wick disposed on the interior surface of the body that defines the central passageway. A base seals off each of the central passageways, and also includes an outlet port arranged in flow communication with (i) an upper portion of each of the central passageways and a common outlet conduit, and (ii) an inlet port arranged in flow communication with a lower portion of each of the central passageways and a common inlet conduit. A coolant is disposed within each of the central passageways. A condenser is arranged in flow communication with each of the evaporators through the common outlet conduit and the common inlet conduit. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     These and other features and advantages of the present invention will be more fully disclosed in, or rendered obvious by, the following detailed description of the preferred embodiment of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts and further wherein:  
         [0011]      FIG. 1  is a front elevational view of a temperature-controlled semiconductor device testing system of the type contemplated for use with the present invention;  
         [0012]      FIG. 2  is an exploded perspective view of an evaporator formed in accordance with the present invention positioned above a semiconductor chip to be cooled atop a support platform of a temperature-controlled semiconductor device testing system;  
         [0013]      FIG. 3  is a side elevational view of a loop thermosyphon formed in accordance with one embodiment of the invention;  
         [0014]      FIG. 4  is a perspective view of an evaporator formed in accordance with the present invention;  
         [0015]      FIG. 5  is a cross-sectional view of the evaporator shown in  FIG. 4 , as taken along line  5 - 5  in  FIG. 4 ;  
         [0016]      FIG. 6  is a perspective view of an array of evaporators having a common condenser formed in accordance with an alternative embodiment of the present invention;  
         [0017]      FIG. 7  is a perspective view of a typical electronics cabinet housing a plurality of arrays of evaporators having a plurality of common condensers formed in accordance with another alternative embodiment of the present invention; and  
         [0018]      FIG. 8  is a perspective view of an array of evaporators arranged in flow communication with a common condenser through common conduits formed in accordance with a further embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0019]     This description of preferred embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description of this invention. The drawing figures are not necessarily to scale and certain features of the invention may be shown exaggerated in scale or in somewhat schematic form in the interest of clarity and conciseness. In the description, relative terms such as “horizontal,” “vertical,” “up,” “down,” “top” and “bottom” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing figure under discussion. These relative terms are for convenience of description and normally are not intended to require a particular orientation. Terms including “inwardly” versus “outwardly,” “longitudinal” versus “lateral” and the like are to be interpreted relative to one another or relative to an axis of elongation, or an axis or center of rotation, as appropriate. Terms concerning attachments, coupling and the like, such as “connected” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. The term “operatively connected” is such an attachment, coupling or connection that allows the pertinent structures to operate as intended by virtue of that relationship. In the claims, means-plus-function clauses are intended to cover the structures described, suggested, or rendered obvious by the written description or drawings for performing the recited function, including not only structural equivalents but also equivalent structures.  
         [0020]     Referring to  FIGS. 2-5 , a loop thermosyphon system  2  for use in cooling one or more semiconductor devices F during burn-in testing includes one or more evaporators  5 , a conduit network  8 , and one or more condensers  11  ( FIG. 3 ). More particularly, each evaporator  5  comprises a vessel  10  and a wick  15  ( FIGS. 4 and 5 ). Vessel  10  includes a first end  19 , an outlet port  21 , a second end  24 , an inlet port  25 , and a central passageway  26  that is defined by interior surface  28  of vessel  10 . Vessel  10  also includes a thermal interface base  27  that is fixedly and hermetically attached to second end  24 . A relatively long blind cylinder or tube that is formed from a thermally conductive material, e.g., copper or its alloys, monel, or the like, is often preferred for vessel  10 . Of course, other shapes of vessel  10  may be used with equal effect. Central passageway  26  defines a vapor space within vessel  10 . Vessel  10  is often about 10 mm in diameter and about 12 mm in height.  
         [0021]     Wick  15  is disposed upon interior surface  28  of vessel  10 , and may comprise adjacent layers of screening or a sintered powder structure with interstices between the particles of powder. Of course, capillary wick  15  may also other wicking structures, such as, grooves, screen, cables, and felt. In one embodiment, wick  15  may comprise sintered copper powder, sintered aluminum-silicon-carbide (AlSiC) or copper-silicon-carbide (CuSiC) having an average thickness of about 0.1 mm to 1.0 mm. A coolant fluid  29  may comprise any of the well known two-phase vaporizable liquids, e.g., water alcohol, freon, etc.  
         [0022]     Conduit network  8  includes an outlet conduit  31  and an inlet conduit  33 , both of which often comprise an elongate hollow tubing having a central passageway  37 . Conduit network  8  is often formed from stainless steel, copper or its alloys, or the like highly thermally conductive material.  
         [0023]     Referring to  FIGS. 3 , and  6 - 8 , each condenser  11  is formed from a conductive metal, such as copper, aluminum, or steel, and comprises a front wall  45 , a rear wall  47 , an inlet duct  49 , and an outlet duct  51 . Each condenser  11  is associated with one or more evaporators  5 , with inlet duct  49  arranged in flow communication with at least one evaporator  5 , via outlet port  21 , and outlet duct  51  arranged in flow communication with at least one evaporator  5 , via inlet port  25 . Front wall  45  and rear wall  47  include interior confronting surfaces that may include a variety of known surface features (e.g., posts, mesh, grooves, irregularly shaped protrusions, baffles, and wick materials) that are adapted for aiding in the dispersal of thermal energy from coolant fluid  29  to front wall  45  and rear wall  47  as it passes between them. Alternatively, condenser may be a liquid cooled, condenser that is chilled by a flowing liquid or gas, e.g., chilled water or air, entering port  53  from a pumped source (not shown) and exiting condenser  11  via port  57  ( FIG. 6 ).  
         [0024]     Each condenser  11  acts as a heat exchanger transferring heat contained in a mixture of vaporous working fluid and liquid working fluid (not shown) to the ambient surroundings, via an external heat sink, e.g., conventional heat exchangers having the capability to facilitate transfer of thermal energy, and that are often heat transfer devices, such as a fin stack, cold plate or secondary heat exchanger of the type well known in the art.  
         [0025]     Referring to  FIGS. 6-8 , a plurality of semiconductor chips F may be cooled simultaneously with an array of evaporators  60  where each evaporator  5  is arranged in flow communication with a common condenser  62 . A plurality of arrays  60  may be stacked with in a cabinet  67  for ease of use with a variety of electronics systems. An alternative embodiment, provides a common inlet conduit  70  and common outlet conduit  72  to which evaporators  5  are interconnected in flow communication such that each outlet port  21  is arranged in flow communication with common outlet conduit  72  and, each inlet port  25  is arranged in flow communication with common inlet conduit  70 .  
         [0026]     In operation, loop thermosyphon system  2  may be used to cool one or more semiconductor devices F in the following manner. A plurality of semiconductor chips F to be cooled ( FIGS. 6-8 ) are thermally coupled to thermal interface base  27 . As thermal energy is transferred from the each semiconductor chip F to evaporator  5 , coolant fluid  29  which saturates wick  15  within evaporator  5  begins to evaporate (i.e., boil). As coolant fluid  29  boils, the pressure within evaporator  5  increases, which in turn forces a mixture of vaporous coolant fluid to flow through outlet port  21  toward condenser  11 . Liquid coolant fluid  29  is condensed within condenser  11  and returns to evaporator  5  via inlet port  25 .  
         [0027]     It is to be understood that the present invention is by no means limited only to the particular constructions herein disclosed and shown in the drawings, but also comprises any modifications or equivalents within the scope of the claims.