Abstract:
An evacuated cavity is hermetically sealed between a baseplate and faceplate of a flat panel display. Melting a glass powder, or frit, on the perimeter of the viewing area forms the hermetic seal. After melting the frit, a first fluid is circulated through the cavity to speed cooling. To further expedite the cooling of the flat panel display, a second fluid flows externally along the contour of the flat panel display to insure that the cooling is uniform and thereby avoid thermal shock.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates generally to sealing flat panel displays, and more particularly, to cooling flat panel displays during a thermal sealing process.  
         BACKGROUND OF THE INVENTION  
         [0002]    Cathode ray tube (CRT) displays are commonly used in display devices such as televisions and desktop computer screens. CRT displays operate as a result of a scanning electron beam from an electron gun striking phosphors resident on a distant screen, which in turn increase the energy level of the phosphors. When the phosphors return to their original energy level, they release photons that are transmitted through the display screen (normally glass), forming a visual image to a person looking at the screen. A colored CRT display utilizes an array of display pixels, where each individual display pixel includes a trio of color-generating phosphors. For example, each pixel is split into three colored parts, which alone or in combination create colors when activated. Exciting the appropriate colored phosphors thus create the color images.  
           [0003]    On the other hand, flat panel displays are becoming more popular in today&#39;s market. These displays are being used more frequently, particularly to display the information of computer systems and other devices. Typically, flat panel displays are lighter and utilize less power than conventional CRT display devices.  
           [0004]    There are different types of flat panel displays. One type of flat panel display is known as a field emission display (FED). FEDs are similar to CRT displays in that they use electrons to illuminate a cathodoluminescent screen. The electron gun is replaced with numerous (at least one per display pixel) emitter sites. When activated by a high voltage, the emitter sites release electrons, which strike the display screen&#39;s phosphor coating. As in CRT displays, the phosphor releases photons which are transmitted through the display screen (normally glass), displaying a visual image to a person looking at the screen. Each pixel can be formed by a trio of color-generating phosphors, each associated with a separate emitter.  
           [0005]    In order to obtain proper operation of the flat panel display, it is important for an FED to maintain an evacuated cavity between the emitter sites (acting as a cathode) and the display screen (acting as a corresponding anode). The typical FED is evacuated to a reduced atmospheric pressure of about 10 −6  Torr or less to allow electron emission. In addition, since there is a high voltage differential between the screen and the emitter sites, the reduced pressure is also required to prevent particles from shorting across the electrodes.  
           [0006]    Generally, the assembly of a flat panel display comprises a baseplate and a faceplate that are physically bonded together in forming a hermetic seal. For example, a glass powder, or frit, is placed in a continuous pattern along the outside perimeter of the display viewing area and melted at elevated temperatures to provide the desired hermetic seal. Typically, the cavity between the baseplate and faceplate is evacuated through an opening while a thermal cycle melts the frit. Once the display is sealed, it is generally important to uniformly cool the display assembly to minimize any thermal stress or shock that may result from immediate exposure to ambient temperature.  
           [0007]    To achieve uniform cooling of the display, however, using conventional methods such as conductive cooling takes long periods of time that can not be afforded in a manufacturing environment. Accordingly, there exists a need for a more rapid cooling process during high vacuum sealing of a flat panel display assembly.  
         SUMMARY OF THE INVENTION  
         [0008]    These and other needs are satisfied by several aspects of the present invention.  
           [0009]    In accordance with one aspect of the invention, a method is provided for high vacuum sealing a flat panel display. The method includes lining the edges of a first component plate with a bonding material. A second component plate is positioned over the first component plate. The bonding material is thus sandwiched between the component plates, defining a cavity between the plates. The bonding material between the component plates is heated, followed by channeling a cooling fluid through the cavity. The cooling fluid has a lower temperature than the component plates. The cavity is thereafter evacuated.  
           [0010]    In accordance with another aspect of the present invention, a method for manufacturing a flat panel display. The method includes forming a flat panel display assembly with an internal cavity. The assembly is thermally processed in a processing chamber. After thermal processing, a first fluid flows through the cavity, cooling inner surfaces of the assembly by convection. Simultaneously, a second fluid flows within the processing chamber, cooling outer surfaces of the assembly by convection. The cavity can then be sealed.  
           [0011]    In accordance with another aspect of the invention, a method is provided for cooling a flat panel display assembly that includes at least two component plates. Cooling is conducted after melting a frit to bond the plates together and define a cavity between the plates. The cooling method includes simultaneously supplying heated gas to inside and outside surfaces of the flat panel display assembly while gradually cooling the gas.  
           [0012]    In accordance with another aspect of the present invention, a vacuum-sealed flat panel display is provided. The display includes a middle plate spaced between an upper plate and a lower plate. An upper cavity is thus defined above the middle plate, while a lower cavity is defined below the middle plate. In addition, a divider block extends between the middle plate and the rear plate. The block divides the lower cavity into two compartments, each of the which communicate with the upper cavity through at least one opening in the middle plate. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    These and further aspects of the invention will be readily apparent to those skilled in the art from the following description and the attached drawings, which are meant to illustrate and not to limit the invention, and wherein:  
         [0014]    [0014]FIG. 1 is a flow chart illustrating a method for high vacuum sealing a flat panel display in accordance with preferred embodiments of the present invention;  
         [0015]    [0015]FIG. 2A is a schematic cross-section of an unassembled flat panel display, constructed in accordance with a first embodiment of the present invention, including a faceplate and a baseplate;  
         [0016]    [0016]FIG. 2B illustrates a partially assembled flat panel display, with a bond material sandwiched between the baseplate and faceplate of FIG. 2A;  
         [0017]    [0017]FIG. 3 illustrates the flat panel display of FIG. 2B while cooling inside a furnace chamber;  
         [0018]    [0018]FIG. 4 illustrates the flat panel display of FIG. 3 following vacuum sealing;  
         [0019]    [0019]FIG. 5 is a schematic cross-section of an assembled flat panel display, constructed in accordance with a second embodiment of the present invention, including a backplate, baseplate and a faceplate with bonding material between the plates;  
         [0020]    [0020]FIG. 6 illustrates the flat panel display of FIG. 5 while cooling inside a furnace chamber; and  
         [0021]    [0021]FIG. 7 illustrates the flat panel display of FIG. 6 following vacuum sealing. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0022]    It will be appreciated that, although the preferred embodiments are described with respect to FED devices, the methods taught herein are applicable to other flat panel display devices, such as liquid crystal displays (LCDs), organic light emitting devices (OLEDs), plasma displays, vacuum fluorescent displays (VFDs) and electroluminescent displays (ELDs). The skilled artisan will also readily appreciate that the materials and methods disclosed herein will have application in a number of other contexts where units are assembled and sealed at elevated temperatures.  
         [0023]    [0023]FIG. 1 is a flow chart exhibiting a preferred process for high vacuum sealing a flat panel display. As shown, the process begins with drilling  202  at least two holes or openings through a baseplate. The drilled holes preferably include holes proximate opposite edges of the baseplate, more preferably proximate diagonally opposite corners. In other arrangements it will be understood that holes can also be formed in the faceplate or a side surface of the display to be assembled.  
         [0024]    Following the drilling  202  of holes, a bond material is applied  204  in a pattern that will form a seal between the plates when assembled. The bond material, comprising a frit (glass powder) in the illustrated embodiments, is patterned around the edges of the faceplate, for example, by mixing the frit into a paste and then dispensing or screen printing the frit. In the preferred embodiment, the frit is preferably mixed into a paste and dispensed around the perimeter edges of the faceplate and/or backplate (see embodiment below), thus avoiding oxidation of the cathode on the baseplate while the frit is fired in air before assembly. The skilled artisan will readily appreciate that the bonding material can alternatively be applied to the baseplate (if oxidation of the cathode can be prevented) or to sidewalls on flanges extending from one of the baseplate and faceplate.  
         [0025]    Subsequently, the flat panel display is assembled  206  by aligning the faceplate over the baseplate to sandwich the bonding material between the faceplate and baseplate. The skilled artisan will appreciate that spacers maintain a uniform distance between the plates. As a result, a cavity is formed between the faceplate and the baseplate, which will allow the flat panel display to function.  
         [0026]    Following the assembly  206  of the flat panel display, a tube is affixed  207  to each of the drilled holes of the baseplate. The tubes can be affixed by using the same or similar frit that was used between the faceplate and baseplate. With the tubes affixed, the drilled holes can serve as input and output ports.  
         [0027]    The flat panel display assembly is placed  208  in a chamber, preferably a furnace chamber. The furnace chamber preferably comprises a first input opening and a first output opening to function as a chamber fluid dispenser and chamber fluid exhaust, respectively.  
         [0028]    The furnace chamber also preferably comprises a second input opening and second output opening. Preferably, the input and output ports of the flat panel display assembly are connected to communicate with the second input opening and the second output opening of the furnace chamber, thus forming input and output tubulation ports.  
         [0029]    After placing  208  and aligning the flat panel display assembly within the preferred furnace chamber, a vacuum is preferably applied to evacuate  210  the furnace chamber and the cavity between the faceplate and baseplate. The furnace chamber can be evacuated by any suitable means, such as conventional vacuum pumping. In this case the inside cavity of the flat panel display is preferably also evacuated, preferably by similar vacuum pumping means through the tubulation ports.  
         [0030]    In other arrangements, a reducing atmosphere (e.g., H 2 , CO, etc.) can be maintained within the flat panel display and/or in the furnace, minimizing the risk of oxidizing devices during subsequent thermal processing.  
         [0031]    After the furnace chamber and the flat panel display cavity are adequately evacuated  210  or filled with a reducing gas, the temperature within the furnace chamber is elevated high enough to melt  211  the frit sandwiched between the faceplate and the baseplate. The melted frit seals the inside flat panel display cavity from the outside environment. The skilled artisan will readily appreciate that other bonding processes may also require thermal or other energy input.  
         [0032]    Once the frit is melted  211  and the flat panel display assembly is sealed off, a cooling fluid is circulated  212  within the cavity, preferably by pumping fluid into the input tubulation port(s) through the cavity and out the output tubulation port(s). Preferably, the ports are arranged to achieve uniform convective cooling within the flat panel display assembly. The fluid, preferably a gas, also preferably comprises a non-oxidizing agent such as nitrogen, argon, etc., to protect the internal components of the flat panel display from oxidation. At the same time, to facilitate uniform cooling across the flat panel display assembly, cooling gas is also preferably circulated within the furnace chamber to provide controlled, convective cooling to the outside of the assembly.  
         [0033]    In the final hermetically sealed condition, the components of the flat panel display are subjected to a substantial amount of stress due to the pressure differential between the inside and the outside of the assembly. Accordingly, a similar pressure differential between the inside and outside of the flat panel display during the thermal cycle is most preferably applied. The pressure differential can be applied by evacuating the display after the frit has sealed the package and the temperature has somewhat reduced, such that the frit is solidified. Alternatively, the furnace can be pressurized during the thermal cycle prior to final evacuation of the display. This allows the components of the flat panel display to be subjected to stresses similar or equal to those that the assembly will be subjected to in the final sealed condition. In other words, this configuration allows for the flat panel display to be pre-stressed or conditioned during the sealing process.  
         [0034]    Following the cooling  212  of the flat panel display, the inside cavity is preferably evacuated  214  by vacuum pumping through the tubulation ports of the flat panel display. The input and output ports of the flat panel display are pinched off  215  to seal the inside cavity from the outside environment. Pinch-off heaters elevate the temperature of the evacuated input and output ports enough to collapse the ports and seal the openings. The vacuum-sealed flat panel display can then be removed  216  from the furnace chamber.  
         [0035]    The sealing process of the preferred embodiments will now be described in more detail with reference to FIGS.  2 - 7 .  
         [0036]    With reference initially to FIG. 2A, components of an unassembled flat panel display are shown. The main components of a flat panel display include a frontal support element or faceplate  10  and a rear support element or baseplate  20 , both which are preferably manufactured of a glass compound. In the illustrated FED embodiment, the baseplate  20  comprises cathode emitter tips while the faceplate includes an anode element and photo-luminescent coating, such as phosphors.  
         [0037]    At least two holes  12   a  and  12   b  are formed through the baseplate  20 . Tubes  16   a  and  16   b  are affixed therebelow by any suitable means, forming input and output ports to the interior of the assembly. While illustrated schematically with two holes  12   a ,  12   b , the skilled artisan will appreciate that multiple holes can be peripherally positioned to obtain uniform flow from inlet ports to outlet ports across the inner surfaces of the flat panel display. Most preferably, two holes are positioned proximate diagonally opposite corners.  
         [0038]    Additionally, a bond material is preferably placed on the perimeter edges of the faceplate  10 . The preferred bond material is a frit  5 , comprising glass powder and other additives that, when mixed into a paste, is advantageously used to make a thermally compatible vacuum tight seal between two glass compounds. The frit  5  can be applied using conventional methods.  
         [0039]    After firing the frit  5 , the components of FIG. 2A are then assembled together to form the flat panel display assembly  30 , as shown in FIG. 2B. Spacers and alignment markers (not shown) aid in the assembly to produce a uniform space or cavity  18  between the plates. The frit  5  is sandwiched between the faceplate  10  and the baseplate  20 , forming a cavity  18  therebetween.  
         [0040]    Prior to or subsequent to the assembly of the flat panel display  30 , it is placed inside a chamber, preferably a furnace chamber  40 . With reference to FIG. 3, the furnace chamber  40  comprises at least one inlet  42  and at least one outlet  45  for fluid flow and/or evacuation of the chamber during the sealing process. The illustrated furnace chamber  40  further comprises a second input opening  47  and a second output opening  49 . The flat panel display  30  is aligned within the furnace chamber  40  so that the tubes  16   a ,  16   b  communicate with the second input opening  47  and second output opening  49 , respectively, thus forming an input tubulation port  61  and output tubulation port  62 .  
         [0041]    For some flat panel display technologies, it is advantageous for thermal processes (for example, to melt the frit as described below) to be conducted in a reducing atmosphere or vacuum to protect the components of the display from oxidation. In the preferred embodiment, once the flat panel display  30  is assembled and aligned within the furnace chamber  40 , both the chamber  40  and the cavity  18  are preferably evacuated by any suitable means. Using conventional vacuum pumping, the pressure range within the chamber  40  and the cavity  18  is pumped down to preferably between about 10 −9  Torr and 10 −5  Torr, more preferably between about 10 −8  Torr and 10 −6  Torr. During the pump-down (preferably over 2-3 hours) the chamber  40  temperature is preferably elevated to between about 300° C. and 350° C., more preferably between 320° C. and 330° C. to bake-out any moisture contained within the display package  30 . In other arrangements, the cavity  18  can be filled with reducing agents (e.g., H 2 , CO, etc.) rather than being evacuated.  
         [0042]    After both the chamber  40  and cavity  18  are adequately evacuated or filled with reducing gas, the temperature within the furnace chamber  40  is raised to a high enough temperature to melt the frit  5  sandwiched between the faceplate  10  and baseplate  20 . By melting the frit  5 , the faceplate  10  and the baseplate  20  are effectively bonded to one another, sealing the cavity  18  from the chamber  40 . To melt the frit, the temperature within the furnace chamber  40  is preferably elevated to between about 300° C. and 550° C., more preferably between about 400° C. and 500° C. for a preferred duration of between about 15 minutes and 30 minutes, more preferably between about 20 minutes and 25 minutes.  
         [0043]    Depending of the design of the flat panel display assembly, an external force can also be applied to the outside of the package assembly during the melting process to maintain alignment of the assembly and to help the frit  5  flow. The external force may be applied utilizing fixed clamps, springs clamps, weights, etc.  
         [0044]    Subsequent to thermal sealing of the flat panel display assembly  30 , it is generally advantageous to cool the flat panel display assembly  30  to minimize thermal shock resulting from ambient exposure. At the same time, in a manufacturing environment, it is generally desirable to expedite the cooling of the flat panel display assembly  30  to improve production throughput.  
         [0045]    Accordingly, an internal cooling fluid  65  is pumped into the input tubulation port  61  and out through the output tubulation port  62  to convectively cool the inside of the flat panel display  30 . The cooling fluid also preferably comprises a non-oxidizing agent such as nitrogen or argon, or a reducing agent such as H 2  or CO, protecting the internal components of the display from oxidation during the process. Preferably, the cooling fluid is initially heated to a temperature below that of the thermal process by between about 5° C. and 10° C., more preferably between about 10° C. and 20° C. The initial flow of gas is heated to minimize any thermal shock induced by the temperature difference between the flat panel display  30  and the cooling fluid. Band heaters (not shown) or any suitable means as is well known in the art can conduct heating of the cooling fluid.  
         [0046]    The cooling fluid  65 , comprising argon gas in the illustrated embodiment, is pumped initially at a rate preferably between about 25 sccm and 500 sccm, more preferably between 50 sccm and 100 sccm, at a preferably temperature range between about 300° C. and 500° C., more preferable between about 400° C. and 500° C. Thereafter, the temperature of the cooling gas  65  is decreased at a preferable rate to optimize convective cooling of the flat panel display  30 . Preferably, the temperature of the cooling gas  65  is decreased at a rate of between about 5° C./min and 30° C./min, more preferably between about 10° C./min and 20° C./min. Also, to further optimize convective cooling of the flat panel display  30 , it may be advantageous to increase the flow rate of the cooling gas  65  as its temperature is being decreased. In the preferred embodiment, the flow rate of the cooling gas  65  is increased preferably increased to between about 100 sccm and 1000 sccm, more preferably between about 250 sccm and 750 sccm. As an example, the flow rate of cooling gas  65  can be increased by between about 10 sccm/min to 20 sccm/min. The skilled artisan will readily appreciate that minimizing thermal shock can be achieved by either or both of controlling the cooling gas temperature and controlling the cooling gas flow rate.  
         [0047]    To insure that the cooling of the flat panel display  30  is uniform, it is advantageous to pump an external cooling gas  67  into the furnace chamber  40  to provide controlled, convective cooling to outside surfaces of the flat panel display  30 . A preferably inert or non-oxidizing gas, comprising argon in the illustrated embodiment, is pumped into the chamber fluid dispenser  42  at a rate preferably between about 25 sccm and 500 sccm, more preferably between about 50 sccm and 100 sccm. Also, the flow of the external gas  67  is preferably increased at a rate of between about 10 sccm/min and 20 sccm/min. Like the internal cooling gas  65 , the temperature of the external cooling gas  67  is constantly kept lower than the temperature of the cooling assembly  30 . Moreover, the external cooling gas  67  temperature is preferably the substantially same temperature as the internal cooling gas  65 , such that the substrates or plates are uniformly cooled from inside and out and thermal stress cracking is avoided during the aided cool down. Insubstantial differences in actual gas temperature between the internal cooling gas  65  and the external cooling gas  67  may result, for example, by differences in pathlengths from a common heat source to the inner and outer surface of the assembly  30 , respectively.  
         [0048]    As a result of exposure to cooling fluids  65 ,  67 , the temperature of the flat panel display  30  is desirably brought down to between about 30° C. and 100° C., more preferably between about 30° C. and 50° C., after between about 2 and 3 hours.  
         [0049]    Subsequent to the cooling of the flat panel display  30 , the cavity  18  is evacuated through the tubulation ports  61  and  62 . Uniform evacuation can be aided by switching both ports to the vacuum source by means of conventional switch valves. Alternatively, a reducing agent (not shown) such as hydrogen (H 2 ), carbon monoxide (CO), etc., may be subsequently back-filled into the cavity  18 , particularly where inert cooling gas was employed prior to evacuation. Introducing H 2 , for example, before a final evacuation of the cavity  18  may be advantageous for the emitter tips (not shown) of the flat panel display  30 .  
         [0050]    With reference to FIG. 4, once the cavity  18  is evacuated of the cooling gas  65  and any reducing agent, the input and output ports  16   a ,  16   b  are pinched off or sealed to effectively seal the inside cavity  18  from the surrounding environment. Pinch-off heaters, or other sealing mechanisms as are well known in the art, are utilized to seal the input and output ports  16   a  and  16   b . The pinch-off heaters, for example, elevate the temperature of the evacuated tube ports  16   a  and  16   b  high enough to collapse them and form seals  15   a  and  15   b  at the corresponding drilled holes ( 12   a ,  12   b ). Once cooled, evacuated and sealed, the flat panel display  30  is removed from the furnace chamber  40 .  
         [0051]    In accordance with a second embodiment, FIG. 5A illustrates components of an unassembled flat panel display  130  comprising a frontal support or faceplate  110 , middle support or baseplate  120  and a rear support or backplate  125 . This three-piece configuration differs from the two-piece (i.e., faceplate and baseplate) configuration of FIGS.  2 - 4  in that the baseplate  120  is thinner than the faceplate  110  and an additional backplate  125  is provided.  
         [0052]    [0052]FIG. 5 further illustrates similar bond material or frits  105   a ,  105   b  at the perimeter edges of both the backplate  125  and the faceplate  110 , which are fired in air prior to assembly. During this firing, the baseplate  120  is not present, avoiding oxidation of the cathode. When assembled, as is illustrated in FIG. 5, the baseplate  120  is sandwiched between the faceplate  110  and the backplate  125  with frits  105   a ,  105   b  on both top and bottom of the baseplate  120 . The sandwiching of the three pieces forms a divided cavity, comprising an upper cavity  118   a  and a lower cavity  118   b , between the faceplate  110  and backplate  125 .  
         [0053]    Holes  112   a ,  112   b  are drilled through the backplate  125 , with tubes affixed to form an input port  116   a  and an output port  116   b . Additionally, a second set of at least two holes ( 112   c  and  112   d ) are also drilled through the baseplate  120 , which will allow for fluid to be pumped through both sides of the baseplate  120 . The holes  112   a ,  112   b  through the backplate  125  are preferably centrally located, whereas the holes  112   c ,  112   d  in the baseplate  120  are preferably peripherally located, as will be better understood from the following discussion.  
         [0054]    A divider  135  is most preferably mounted to the interior side of the backplate  125  or baseplate  120  (shown on the backplate  125 ). This divider  135  preferably extends across one dimension of the assembly  130 . An additional frit  105   c  is placed on one side of the divider  135  such that, when assembled, it is sandwiched between the baseplate  120  and the divider  135  and divides the lower cavity  118   b  into two compartments.  
         [0055]    With reference to FIG. 6, an assembled flat panel display  130  is positioned within a furnace chamber  140 , wherein the input and output ports  116   a ,  116   b  correspondingly communicate with the second input and output openings  147 ,  149  of the furnace chamber  140 . As a result, input and output tubulation ports  161 ,  162  are thus formed.  
         [0056]    As mentioned above, for some flat panel display technologies, it is advantageous for thermal processes (for example, to melt the frit as described below) to be conducted in a reducing atmosphere or vacuum to protect the components of the display from oxidation. In the preferred embodiment, once the flat panel display  130  is mounted within the furnace chamber  140 , both the chamber  140  and the cavity  118   a ,  118   b  are accordingly evacuated by any suitable means. Using conventional vacuum pumping, the pressure range within the chamber  140  is preferably pumped down slowly to between about 10 −9  Torr and 10 −5  Torr, more preferably between about 10 −8  Torr and 10 −6  Torr. The cavity  118   a ,  118   b  is preferably pumped down to the same pressure ranges. Desirably, the chamber  140  temperature is elevated to between about 300° C. and 350° C., more preferably between 320° C. and 330° C., during pump-down over 2-3 hours to bake-out any moisture contained within the display package  130 .  
         [0057]    Subsequently, the temperature within the furnace chamber  140  is raised to a high enough temperature to melt the frits  105   a ,  105   b ,  105   c  sandwiched above and below the baseplate  120 . By melting the frits  105   a ,  105   b  and  105   c , the assembly components are effectively bonded to one another, sealing the cavity  118   a ,  118   b  from the chamber  140 . To melt the frits  105   a ,  105   b  and  105   c , the temperature within the furnace chamber  140  is preferably elevated to between about 300° C. and 550° C., more preferably between about 400° C. and 500° C. for a preferred duration of between about 15 minutes and 30 minutes, more preferably between about 20 minutes and 25 minutes.  
         [0058]    Subsequent to melting the frits  105   a ,  105   b ,  105   c  at elevated temperatures, it is generally advantageous to cool the flat panel display  130  in a manner that minimizes thermal shock induced from ambient exposure. However, in a manufacturing environment, it is also generally desirable to expedite the cooling of the flat panel display  130  to improve production throughput.  
         [0059]    Accordingly, as shown in FIG. 6, cooling fluids  65 ,  67  are provided to the interior and exterior of the assembly  130  to provide a uniform convective cooling to inside and outside surface of the flat panel display  130 . Preferred cooling gas compositions, temperatures and flow rates can be as described for the previous embodiment.  
         [0060]    Within the assembly  130 , cooling fluid  65  circulates both above and below the baseplate  120  through both portions  118   a ,  118   b  of the cavity by means of the two drilled holes  112   c ,  112   d . As briefly noted above, the relative positions of the holes  112   a ,  112   b  and holes  112   c ,  112   d , with respect to each other and to the divider  135 , are selected to optimize uniform distribution of the cooling gas  65  in both portions  118   a ,  118   b  of the cavity. In particular, the lower holes  112   a ,  112   b  are preferably positioned proximate the divider  135 , whereas the central holes  112   c ,  112   d  are preferably located peripherally. Thus, at least one of the lower holes  112   a ,  112   b  communicates with each of the compartments on either side of the divider  135 . Similarly, at least one of the central holes  112   c ,  112   d  communicates with each of the compartments on either side of the divider  135 .  
         [0061]    During the cooling process, once the frits have solidified enough to seal the inside of the display  130  from the outside, a pre-stressing pressure differential is established between the inside of the display  130  and the chamber  140 . The differential can be established by any combination of pressurizing and pumping down the display  130  and chamber  140 , but the differential should be equivalent to the final product pressure differential, e.g., about atmospheric in the chamber  140  and about 10 −6  Torr within the display  130 .  
         [0062]    Referring to FIG. 7, subsequent to cooling the flat panel display  130 , the cavity  118   a ,  118   b  is again evacuated through the tubulation ports  161 ,  162 . Uniform evacuation can be aided by switching both ports to the vacuum source by means of conventional switch valves. The input and output ports  116   a ,  116   b  are then pinched off or sealed to effectively seal the inside cavity  118   a ,  118   b  from the surrounding environment, as described above, forming seals  115   a ,  115   b  at the drilled holes  112   a ,  112   b , respectively. Once cooled, evacuated and sealed, the flat panel display is removed from the furnace chamber  140 .  
         [0063]    Several advantages are obtained by the preferred process. For example, circulating fluid to cool by convection more efficiently cools an assembly than by conventional conductive cooling. Fluid pathways formed within the flat panel display allow for an effective circulation of a cooling fluid during a high vacuum sealing process. Additionally, the illustrated arrangements facilitate application of a pressure differential between the inside and outside of a flat panel display, subjecting and conditioning the flat panel display to pressure differentials similar to those of the final sealed product. The same ports used to evacuate the inside of the flat panel display can be used to circulate a fluid to more quickly cool the flat panel displays.  
         [0064]    Although this invention has been described in terms of a certain preferred embodiment and suggested possible modifications thereto, other embodiments and modifications may suggest themselves and be apparent to those of ordinary skill in the art are also within the spirit and scope of this invention. Accordingly, the scope of this invention is intended to be defined by the claims that follow.