Patent Abstract:
A sheet utilized in making electronic displays may be prone to warping. This warping may result in the failure to make good surface-to-surface contact or even electrical connections between layers. By processing the sheet prone to warpage in a flattened configuration, the occurrence of stress-induced cracking when the sheet is applied to a rigid planar structure may be reduced. Moreover, a distorted sheet may be processed economically while still resulting in a final product which is regular, flat and planar.

Full Description:
BACKGROUND  
         [0001]    This invention relates generally to the manufacture of displays for electronic devices.  
           [0002]    In a number of cases, displays for electronic devices may be made from a plurality of layers. In some cases, these layers are of microelectronic dimensions. One layer may be warped or non-flat relative to the other layer. It may be desired to electrically interconnect these layers with at least one of the layers being re-shaped or flattened so that contact distance is the same.  
           [0003]    For example, displays may include a glass layer which generally is free of warpage and is effectively perfectly flat. However, ceramic layers, for example for making circuit boards, may be warped or non-flat.  
           [0004]    Given the distortion of one of two layers to be joined, a number of possibilities arise. One adverse consequence of the distortion is that some of the contacts between the two layers are not effective across the abutting area between the two surfaces. Another possibility is that one of the layers, such as the glass layer, may warp to conform to the other layer such as a ceramic layer. Another possibility is that the ceramic layer may warp to conform to the glass layer. Still another possibility is that each of the layers warp to some degree. As still another possibility, residual stresses may be formed that may cause contacts to fail between layers. The residual stress may arise because of the stress on materials formed on layers, due to the distortion of layers or even due to the fact that the layers eventually return to an undistorted shape after being processed in a distorted shape.  
           [0005]    Referring to FIG. 8, a circuit board layer  12   a  may be secured to a display panel  12   b  by a plurality of contacts indicated at  16 . Because of the warpage of the circuit layer  12   a , some or all of the contacts  16  either may not make good electrical connection or contacts that originally made connection may break free, resulting in open circuits.  
           [0006]    To the extent that any layer warps or distorts because of the distortion of the other layer, the possibility exists of destroying structures which are formed on a given layer. Namely, if a layer is restored to an unwarped configuration (which may be necessary in use in some cases), the interconnections and other structures that are formed on one or more layers may be disturbed.  
           [0007]    Thus, there is the need for a way to deal with the possibility of warped layers or components in assembling display modules.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a cross-sectional view of a chuck that is useful in accordance with one embodiment of the present invention;  
         [0009]    [0009]FIG. 2 is a cross-sectional view of a pair of chucks in opposition in accordance with one embodiment of the present invention;  
         [0010]    [0010]FIG. 3 is a cross-sectional view of a chuck holding a pair of display layers in accordance with one embodiment of the present invention;  
         [0011]    [0011]FIG. 4 is a cross-sectional view of the attachment of the display layers to an integrating plate in accordance with one embodiment of the present invention;  
         [0012]    [0012]FIG. 5 is a side elevational view of one embodiment of the present invention;  
         [0013]    [0013]FIG. 6 is a top plan view of the embodiment shown in FIG. 5;  
         [0014]    [0014]FIG. 7 is a partial, enlarged, cross-sectional view of one embodiment of the present invention; and  
         [0015]    [0015]FIG. 8 is a cross-sectional view of an embodiment in accordance with the prior art. 
     
    
     DETAILED DESCRIPTION  
       [0016]    Referring to FIG. 1, a chuck  18   a  may be utilized to secure a circuit board layer  12   a  in a flat configuration in one embodiment. In one embodiment, the circuit board layer  12   a  may be made of a ceramic material that may warp. Applying a vacuum through the chamber  26  within the chuck  18   a , the circuit board layer  12   a  may be secured for processing in a flat or flattened configuration with the surface  28  facing upwardly for processing.  
         [0017]    The vacuum applied through the chamber  26  may be distributed across the surface of the circuit board layer  12   a  by the diffuser  22  including a plurality of openings  24  in one example. Thereafter, the circuit board layer  12   a  may be subjected to any necessary processing.  
         [0018]    Advantageously, since the circuit board layer  12   a  may initially have been warped, but is now held in a flattened configuration, the circuit board layer  12   a  is processed in a planar configuration. Thus, if ultimately the circuit board layer  12   a  is maintained in a flat planar configuration, it is not necessary to stress the processed features that have been applied to the surface  28  of the circuit board layer  12   a.    
         [0019]    Referring to FIG. 2, the chuck  18   b  may be utilized to similarly secure a display panel  12   b  in accordance with one embodiment of the present invention. In this example, the circuit board layer  12   a  may be attached to the back side or nondisplay side of the panel  12   b . Commonly, the display panel  12   b  may include a glass panel with light emitting elements secured or deposited to the panel  12   b . For example, in one embodiment, organic light emitting devices (OLEDs) may be formed by depositing organic light emitting materials and associated column and row electrodes on a glass sheet.  
         [0020]    The display panel  12   b  may be processed through a series of steps in which the display panel  12   b  is held in a flat configuration by the chuck  18   b . When the processing of both circuit board layer  12   a  and display panel  12   b  has been completed, the two chucks  18  are arranged in juxtaposition as shown in FIG. 2 and the display panel  12   b  and the circuit board layer  12   a  have their processed sides combined as indicated at  28 .  
         [0021]    The connections between the circuit board layer  12   a  and the display panel  12   b , in one embodiment, may be electrical connections using solder as one example. For example, in accordance with conventional flip chip or surface mount packaging techniques, solder bumps or balls may be utilized to provide electrical connections between the display panel  12   b  and the circuit board layer  12   a . In one example, chucks  18   a  and  18   b  may be heated chucks to cause the solder to soften and fuse the display panel  12   b  to the circuit board layer  12   a , thereby forming electrical connections as well as a physical bond between two parts.  
         [0022]    Next, the chuck  18   b  may be removed to expose the display panel  12   b , now secured to the circuit board layer  12   a  as indicated in FIG. 3. However, in this configuration, both the circuit board layer  12   a  and the display panel  12   b  may be held in a flat (or flattened) configuration in one embodiment.  
         [0023]    In one embodiment, the composite of the circuit board layer  12   a  and the display panel  12   b  may be secured to an optical integrating plate  30  as shown in FIG. 4. The optical integrating plate  30  may include a structure that holds the composite of the circuit board layer  12   a  and the display panel  12   b  in a flat, secured position, as indicated in FIG. 5.  
         [0024]    The integrating plate  30  may include a transparent sheet that allows the display panel  12   b  to be viewed through the optical integrating plate  30 . In some embodiments, the optical integrating plate  30  may provide a diffusing effect. In other cases, the integrating plate  30  may provide the effect of integrating a plurality of discrete display portions or tiles into an overall large area display.  
         [0025]    In one embodiment, the integrating plate  30  is adhesively secured to the display panel  12   b . The panel  12   b  may be secured by surface mount techniques to the circuit board layer  12   a.    
         [0026]    At this point, the securement between the chuck  18   a  and the circuit board layer  12   a  may be released since the optical integrating plate  30  holds the assembly in a flat configuration. Because the layer  12   a  and the panel  12   b  were processed in a flat configuration, the interconnections and elements that are attached during processing to the layer  12   a  and panel  12   b  are not unnecessarily stressed because these elements are always held in a flat configuration during processing and through use.  
         [0027]    Referring to FIG. 6, the optical integrating plate  30  may include a transparent section  10 . The display panel  12   b  may be secured to the opposite surface of the one shown in FIG. 6. The transparent plate  10  may be encircled by a frame  34  which provides rigidity to the optical integrating plate  30  and may provide a more pleasing appearance.  
         [0028]    Because of potential warping, for example, of the circuit board layer  12   a , if the display panel  12   b  and layer  12   a  are processed in a conventional fashion, the stresses between the circuit board layer  12   a  and panel  12   b  may cause the contacts  16 , which may be solder balls, to break and release when the circuit board layer  12   a  for example attempts to return to its original shape. Alternatively, because of the warping of the circuit board layer  12   a , good electrical contact may not be made between the layer  12   a  and panel  12   b . Thus, to prevent stress-induced cracking and to make sure that good surface-to-surface contact for electrical connections are established, processing the two sheets in a flat configuration and then securing them to an integrating plate  30  may be advantageous in some embodiments.  
         [0029]    Although an embodiment using vacuum chucks  18  is discussed above, other techniques may be used to process panels  12   b  or layers  12   a  in a flat or flattened configuration. Another temporary holding technique includes using releasable adhesives to secure the panel  12   b  or layer  12   a  to a carrier.  
         [0030]    The processing of the display panel  12   b , in accordance with one embodiment, may begin by depositing a column electrode  40  on the panel  12   b  as shown in FIG. 7 a . In one embodiment, the column electrode  40  may be formed of a conductive transparent material such as indium tin oxide (ITO). Next, as shown in FIG. 7 b , an insulating layer  44  and a light emitting layer  42  may be deposited. In one embodiment, the light emitting layer  42  may be an organic light emitting layer. Next, the row electrodes  46  may be formed atop the resulting composite as shown in FIG. 7 c.    
         [0031]    While the present invention has been described with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.

Technology Classification (CPC): 1