Abstract:
An electronic device having an extensive narrow passageway may be effectively encapsulated by forming openings in one or more of the surfaces defining the encapsulation region. Encapsulation material may then be injected through these openings to fill a narrow, difficult to access region between two surfaces being encapsulated. In some cases, the encapsulant may be applied progressively, starting with a central port and applying the encapsulant in a radially expanding front through radially displaced ports.

Description:
BACKGROUND  
         [0001]    This invention relates generally to the manufacture of electronic devices, including electronic displays, and particularly the encapsulation of such devices.  
           [0002]    The encapsulation of electronic devices may involve the use of a viscous liquid material such a epoxy which is applied into voids and open areas within electronic devices. In some cases, the encapsulation prevents attack from contaminants such as water and air. In addition, encapsulation sometimes increases the structural integrity of the electronic device. For these and other reasons, it is often desirable to apply encapsulation material to electronic devices.  
           [0003]    In a variety of circumstances, the area to be encapsulated may involve a relatively narrow region between surfaces of electronic devices. Examples of such situations are the encapsulation of an integrated circuit chip onto a printed circuit board and the encapsulation between panels in electronic display devices. In each case, a narrow, planar region must be encapsulated. However, the encapsulation material is generally somewhat viscous. Because of the intrusion of electronic devices into the encapsulation region or because of its narrowness, it may be difficult to provide an encapsulation source inwardly into the narrow region.  
           [0004]    Given the narrowness of the encapsulation region, two problems may arise. Firstly, it may take an excessively long time to cause encapsulation to occur. With conventional techniques, beads of encapsulation are applied around the edges of the narrow region to be encapsulated. Capillary forces are then relied upon to draw the encapsulant inwardly into the encapsulated region. In some cases, the encapsulation material is only applied on two of four edges. One reason for doing so is to attempt to avoid creating air pockets within the encapsulated region due to the intersection of fronts of ongoing, moving encapsulation material, drawn by capillary forces. Thus, the amount of time involved in encapsulating relatively large areas may be excessive.  
           [0005]    Secondly, it may be difficult to cause the encapsulation to occur within the remote region defined by narrow surfaces without creating air pockets within the region. The air pockets can cause the very problems that encapsulation was intended to overcome. Namely, air pockets may facilitate attack by external contaminants and reduce structural integrity of the encapsulated product.  
           [0006]    Thus, there is a need for better ways to encapsulate electronic devices.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is an enlarged, cross-sectional view of an electronic device to be encapsulated in accordance with one embodiment of the present invention;  
         [0008]    [0008]FIG. 2 is a cross-sectional view of the device of FIG. 1 after encapsulation in accordance with one embodiment of the present invention;  
         [0009]    [0009]FIG. 3 is a top plan view of the device shown in FIG. 2, in accordance with one embodiment of the present invention;  
         [0010]    [0010]FIG. 4 a  is a schematic top plan view showing the encapsulation of an electronic device in accordance with one embodiment of the present invention;  
         [0011]    [0011]FIG. 4 b  is an enlarged cross-sectional view corresponding to FIG. 4 a  at a subsequent stage of encapsulation in accordance with one embodiment of the present invention;  
         [0012]    [0012]FIG. 4 c  is an enlarged cross-sectional view corresponding to FIG. 4 b  at a subsequent stage of encapsulation in accordance with one embodiment of the present invention; and  
         [0013]    [0013]FIG. 4 d  is an enlarged cross-sectional view corresponding to FIG. 4 c  at a subsequent stage of encapsulation in accordance with one embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0014]    Referring to FIG. 1, an electronic device  10  may, in one embodiment, be a tile or display module for a large area display. In other embodiments, the electronic device  10  may be an electronic integrated circuit being connected to a surface such as a printed circuit board. The electronic device  10 , in general, includes a narrow region  11  to be encapsulated.  
         [0015]    In the embodiment shown is FIG. 1, a display panel  12  and a back plate  14  define a narrow region  11  to be encapsulated. In one embodiment, that region  11  may be punctuated by interconnects  16 , light emitting display elements  20 , and other devices that may obstruct the flow of encapsulant into the region  11 .  
         [0016]    A port  22  may be provided to facilitate the injection of encapsulant. In one embodiment, encapsulation material, rather than being injected at the edges of the electronic device  10  is actually applied through encapsulation injection ports  22  that are defined through the back plate  14 . Obviously, the ports  22  must be placed in a position so as not to disrupt the electronic operations of the device  10 .  
         [0017]    Encapsulant then may be injected into the region  11  until such time as the device  10  is fully encapsulated. While two encapsulation ports  22  are illustrated, in some cases, only a single encapsulation port  22  may be utilized and in some embodiments, a port  22  may be centrally located on the device  10 .  
         [0018]    In general, it may be advantageous in many embodiments to cause encapsulant to spread outwardly from the center of the device  10  towards its edges. This, in some embodiments, may prevent the formation of air pockets or air bubbles in the encapsulated region  11 .  
         [0019]    Generally, the encapsulation material is any normally utilized encapsulation material. It may be viscous in some cases. For example, epoxy may be utilized. In general, the encapsulation material is applied as a liquid and eventually hardens to form a tough encapsulation.  
         [0020]    The completed structure, shown in FIG. 2, includes encapsulation  24 , having end portions that may form a meniscus. Encapsulation  24  totally fills the region  11 , in one embodiment, and also fills the injection ports  22 .  
         [0021]    In accordance with one embodiment of the present invention, a plurality of injection ports  22  may be utilized. A central injection port  22   a  is initially utilized to inject the encapsulation material between the panel  12  and plate  14 . Once the encapsulation material begins to appear in a second ring of encapsulation ports  22   b,  the injection through the port  22   a  may be stopped and the injection through the ports  22   b  may begin. Thus, if the port  22   a  is centrally located on the panel  12  and plate  14 , and the ports  22   b  are radially distributed with respect to the port  22   a,  a cylindrically advancing front of encapsulant may be provided between the panel  12  and plate  14 . This arrangement may reduce the likelihood of forming air bubbles.  
         [0022]    Once the encapsulant applied through the ports  22   b  reaches the ports  22   c,  the flow of encapsulant through the ports  22   b  may be stopped. Next encapsulant may be injected through the ports  22   c.  The ports  22   c  are radially outwardly displaced from the ports  22   b  in one embodiment of the present invention. In addition, the ports  22   c  may be situated along a radius that bisects an arc defined between two adjacent ports  22   b.  In this way, the occurrence of air pockets or voids may be reduced by continually applying the encapsulant in a progressive fashion in the regions most likely to form voids or air bubbles.  
         [0023]    Finally, a fourth ring of encapsulation ports  22   d  may be utilized to complete the flow of encapsulant in one embodiment. Again the ring of ports  22   d  is spaced radially outwardly with respect to the ports  22   c  and situated intermediately with respect to adjacent ports  22   c.    
         [0024]    Referring to FIG. 4 a,  a more generalized embodiment is illustrated. In this example, the electronic device  10   a  may be a device other than a display. It may include more or less components within the gap region  11 . Initially, the encapsulant  24   a  is injected through a centrally located port  22   a  and the encapsulant  24   a  spreads radially outwardly toward the radially outwardly displaced ports  22   b.  When the encapsulant  24   b  reaches the ports  22   b,  as shown in FIG. 4 b,  the injection of encapsulation through the port  22   a  is stopped and encapsulation material may be injected through the ports  22   b.    
         [0025]    Similarly, that injection is continued until the encapsulation material  24   c  reaches the ports  22   c,  at which time injection through the ports  22   b  is terminated and replaced with injection through the ports  22   c,  as shown in FIG. 4 c.  Finally the injection commences through the ports  22   d,  replacing the flow through the ports  22   c  when the encapsulant  24   d  reaches the ports  22   d,  as shown in FIG. 4 d.  When encapsulant reaches the peripheral edges of the device  10   a,  the flow of encapsulant may be terminated.  
         [0026]    In some embodiments, injecting encapsulant in a progressive fashion may facilitate the rapid deployment of encapsulation without the provision of air bubbles. In general, the more sources of encapsulant that are provided, the faster the encapsulation may be completed. Particularly with large areas to be encapsulated, the encapsulation time may create a considerable bottle neck in fabrication processing.  
         [0027]    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.