Abstract:
A driver assembly with an efficient mechanism for transferring heat away from an integrated circuit (IC) chip via a heat transfer member and conductive pattern lines formed on a substrate. The IC chip is mounted on connectors and is placed above the substrate. The IC chip operatively communicates with the display panel via at least a subset of the conductive pattern lines and a subset of the connectors. A heat transfer member is formed on the substrate and is configured to transfer heat generated by the integrated circuit to a component having a lower temperature than the IC chip. A heat transfer element is placed between the IC chip and the heat transfer member to transfer the heat generated by the IC chip to the heat transfer member.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority under 35 U.S.C. 119(a) to Korean Patent Application No. 10-2011-0100909, filed on Oct. 4, 2011, which is hereby incorporated by reference in its entirety. 
     BACKGROUND 
     1. Field of the Disclosure 
     This disclosure relates to transferring heat generated by an integrated circuit (IC) chip of a driver assembly for supplying operating signals to a display device to prevent overheating of the IC chip. 
     2. Description of the Related Art 
     Display devices are used for displaying information on a display panel for visual interaction with users. Various types of display technologies were developed and currently available for use in electronic devices. The display devices may incorporate various types of technology including, among others, liquid crystal display (LCD) technology, organic light emitting display (OLED) technology, electrophoretic display technology, field emission display (FED) technology, and plasma display technology. In general, display devices include a display panel and a driver assembly for providing signals to operate pixel elements in the display panel. 
     One conventional way of implementing the driver assembly is by using chip-on-film (COF) technology. The COF generally uses a film (e.g., flexible substrate) and a driver integrated circuit (IC) chip mounted on the film. Wiring patterns are formed on the film and bumps are placed between the driver IC and the film to connect the driver IC to the wiring patterns. The wiring patterns connect the IC chip to signal lines of a display panel. 
     As the size of the display panel increases, the operating frequency and the operating voltage of the driver IC chip also increases. The increased frequency and the operating voltage of the driver IC increases the heat generated within the driver IC. Such increase the internal heat generation can cause the driver IC to overheat, resulting in malfunctioning as well as damage to the driver IC chip. The heating of the driver IC chip can compromise the reliability of the display device. 
     SUMMARY 
     Embodiments relate to a driver assembly with an efficient mechanism for transferring heat away from an integrated circuit (IC) chip via a heat transfer member and conductive pattern lines formed on a substrate. The IC chip is mounted on connectors and is placed above the substrate. The IC chip operatively communicates with the display panel via at least a subset of the conductive pattern lines and a subset of the connectors. A heat transfer member is formed on the substrate and is configured to transfer heat generated by the integrated circuit to a component having a lower temperature than the IC chip. A heat transfer element is placed between the IC chip and the heat transfer member to transfer the heat generated by the IC chip to the heat transfer member. 
     In one or more embodiments, the driver assembly is a chip on film (COF) device. 
     In one or more embodiments, the driver assembly includes an electrically insulating layer partly covering the conductive pattern lines. The connectors are placed on the part of the conductive pattern lines not covered by the electrically insulating layer and extend between the conductive pattern lines and the IC chip. 
     In one or more embodiments, the drive assembly generates signals for transmission over scan lines or data lines of the display panel. 
     In one or more embodiments, the conductive pattern lines include one or more lines connecting the heat transfer member and the component to transfer heat from the heat transfer member to the component. 
     In one or more embodiments, the one or more lines further carry electric signals or reference voltage to or from the IC chip. 
     In one or more embodiments, the heat transfer element is formed on or attached to a bottom of the IC chip. The heat transfer element may have a flat configuration with an area smaller than the bottom surface of the IC chip. 
     In one or more embodiments, the heat transfer element is a filler material injected between the IC chip and the heat transfer member. The filler material is electrically non-conductive but thermally conductive. The filler material may cover an entire bottom surface of the IC chip. 
     In one or more embodiments, the heat transfer member and the plurality of conductive pattern lines are formed in the same fabrication process and are formed of the same material. The fabrication process may include depositing a layer of conductive film on the substrate and etching the deposited film. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view illustrating a display device according to one embodiment. 
         FIG. 2  is a plan view illustrating a first driver assembly in the display device of  FIG. 1 , according to a first embodiment. 
         FIG. 3  is a cross-sectional view illustrating the first driver assembly of  FIG. 2 . 
         FIG. 4  is a cross-sectional view illustrating the driver integrated circuit (IC) chip attached with a second heat transfer member. 
         FIG. 5  is a cross-sectional view illustrating a first driver assembly according a second embodiment. 
         FIG. 6  is a plan view illustrating a first driver assembly according a third embodiment. 
         FIG. 7  is a flowchart illustrating a method for transferring heat from the driver IC chip to a printed circuit board, according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the present embodiments, examples of which are illustrated in the accompanying drawings. 
       FIG. 1  is a plan view showing a display device  100  according to an embodiment. The display device  100  may be embodied using various technologies. For example, the display device  100  may be any one of a liquid crystal display (LCD) device, an organic light emitting display (OLED) device, an electrophoretic display device, a field emission display (FED) device and plasma display device. 
     The display device  100  according to the embodiment can include, among other components, a display panel  10 , a first driver assembly  20 , a second driver assembly  40  and a printed circuit board (PCB)  30 . The display device  100  may include various other components such as a power source and communication interfaces, which are omitted herein for the sake of brevity. 
     The display panel  10  can include a plurality of pixel regions defined by a plurality of scan lines and a plurality of data lines crossing each other. The plurality of pixel regions can be arranged in a matrix, for example. The plurality of scan lines can be electrically connected to the first driver assembly  20 . The plurality of data lines can be electrically connected to the second driver assembly  40 . The pixel regions in a line can be selected by scan signals that are applied, for example, sequentially. By applying data signals to the data lines, one or more pixels in the selected pixel regions can be turned on or off. 
     The first driver assembly  20  generates the scan signals carried over a plurality of scan lines (not shown). For this purpose, the first driver assembly  20  can include, among other components, a first driver IC chip  25 . The first driver IC chip  25  generates the scan signals for turning on or off pixels in the scan lines of the display panel  10 . 
     The second driver assembly  40  generates the data signals for carrying over a plurality of data lines (not shown). For this purpose, the second driver assembly  40  can include, among other components, a second driver IC chip  45 . The second driver IC chip  45  receives external signals from the PCB  30  and, in response, generates the data signals for turning on or off pixels in the data lines of the display panel  10 . 
     As the size of the display panel  10  increases, the voltage level and/or the frequency of the scan signals and the data signals are increased. Such increase in the voltage level and/or frequency of the scan signals and the data signals accompanies increase in the internal heat generated by the first driver IC chip  25  and the second driver IC chip  45 . Embodiments described herein enable effective removal of the internal heat generated in the first and second driver IC chips  25  and  45  outside of the display device  30  via PCB  30  or other components. 
     Although the following descriptions are described below primarily with reference to the first driver assembly  20 , the embodiments described with reference to  FIGS. 2 through 7  can be applied to the second driver IC assembly  40 . That is, the second driver assembly  40  may have the same or similar structure as the first driver assembly  20  to remove the heat generated in the second driver IC chip  45 . 
       FIG. 2  is a plan view illustrating a first driver assembly  20 A of the display device  100 , according to a first embodiment.  FIG. 3  is a cross-sectional view illustrating the first driver assembly  20 A taken along line I-I′ of  FIG. 2 . The first driver assembly  20 A can include, among other components, a substrate member  22 , the first driver IC chip  25 , a first heat transfer member  101  and a second heat transfer member  125 . The first IC chip  25  is mounted on the substrate member  22  to form a chip-on-film (COF) device. The first and second heat transfer members  101  transfers heat from the first IC chip  25  to the PCB  30 . 
     The substrate member  22  can include, among others, a substrate  111 , conductive pattern lines  103  on the substrate  111 , and an insulation film  115  on the conductive pattern lines  103 . The substrate  111  can be formed from a flexible material such as plastic or glass. Alternatively, the substrate  111  can be a thin layer of metal having a foil shape. 
     The conductive pattern lines  103  are formed of electrically conductive material. The conductive pattern lines  103  are sandwiched between the substrate  111  and the insulation film  115  except for a region corresponding to an opening  113  where the conductive pattern lines  103  are exposed for connection to the first driver IC  25  via bumps  127   a ,  127   b . Such conductive pattern lines  103  can include, among other lines, a first signal line  106 , a second signal line  107 , a first ground line  105   a  and a second ground line  105   b . The first signal line  106 , the second signal line  108 , the first ground line  105   a  and the second ground line  105   b  can be electrically connected to the PCB  30  to receive signals and power. 
     The conductive pattern lines  103  may include a single layer or multiple layers. One or more layers of the conductive pattern lines  103  may include materials such as gold, aluminum, silver, titanium, copper, nickel, platinum, molybdenum, tungsten, tantalum and chromium. 
     In one or more embodiments, the conductive pattern lines  103  are formed by depositing a conductive film on the substrate  111  and etching the conductive film, as well known in the art. 
     The first signal line  106 , the first ground line  105   a  and the second ground lines  105   a  can be electrically connected to the PCB  30  through extra conductive pattern lines (not shown) formed on the display panel  10  and the second driver assembly  40 . 
     The first signal line  106 , the second signal line  107  and the ground lines  105   a ,  105   b  can be used to carry various signals. For example, the first signal line  106  can be used to transfer a scan control signal sent from the PCB  30  to the first driver IC chip  25 . The first and second ground lines  105   a  and  105   b  can be connected to a reference voltage source (e.g., GND) and/or transfer heat generated in the first driver IC chip  25 . The second signal line  107  can provide a signal path for sending a scan signal from the first driver IC chip  25  to a scan line on the display panel  10 . 
     The insulation film  115  insulates the conductive pattern lines  103  from external environment to prevent external contaminants from short-circuiting the conductive pattern lines  103 . An opening  113  can be formed in a central area of the substrate member  22  by removing the insulation film  115 . The conductive pattern lines  103  (e.g., first and second signal lines  106 ,  107  and the first and second ground lines  105   a  and  105   b ) are exposed in the opening  113  to enable these lines to come in contact with the first driver IC  25  via bumps (e.g., bumps  127   a ,  127   b ). The first signal line  103 , the first ground line  105   a , second ground line  105   b  and the second signal line  107  are spatially separated in the opening  113  to prevent these lines from coming into contact with each other. 
     The first driver IC chip  25  can be mounted above the opening  113  of the substrate member  22 . One side (e.g., the left side in  FIG. 3 ) of the first driver IC chip  25  can be electrically connected to the first signal line  106 , the first ground line  105   a  and the second ground line  105   b . The other side (e.g., the right side in  FIG. 3 ) of the first driver IC chip  25  can be electrically connected to the second signal line  107 . 
     As illustrated in  FIG. 3 , a first heat transfer member  101  is formed on an area of substrate  111  exposed by the opening  113 . The first heat transfer member  101  is surrounded by conductive pattern lines  103 . The first heat transfer member  101  can be formed by the fabrication process for forming the first and second signal lines  106  and  107  and the first and second ground lines  105   a  and  105   b . Consequently, the first heat transfer member  101  may be of the same material as and formed in the same layer as the first and second signal lines  106  and  107  and the first and second ground lines  105   a  and  105   b . The fabrication process may include depositing a film on the substrate  111  and then etching the film. 
     The first heat transfer member  101  can be electrically insulated from the first and second signal lines  103  and  107 . For this purpose, the first and second signal lines  106  and  107  can be spaced away from the first heat transfer member  101 . 
     The first and second ground lines  105   a  and  105   b  can be electrically connected to the first heat transfer member  101 . The first heat transfer member  101  can remove heat generated in the first driver assembly  20 A via the first and second ground lines  105   a , 105   b  and the PCB  30 . 
     The first heat transfer member  101  can be formed from a thermally conductive resin material such as epoxy or silicon. The first heat transfer member  101  can be prepared by forming a liquid resin material on the substrate member  22  within the opening  113  and curing the liquid resin material into a hard solid. Alternatively, the first heat transfer member  101  may be a tape formed from a resin material on the substrate member  22  exposed to the opening  113 . 
       FIG. 4  is a cross-sectional view illustrating the first driver IC chip  25  attached with a second heat transfer member  125 , according to one embodiment. The second heat transfer member  125  can be formed on or attached to the bottom surface of the first driver IC chip  25 . The second heat transfer member  125  comes into contact with the first heat member  101  to transfer heat from the body of the first driver IC  25  to the first heat transfer member  101 . The second heat transfer member  125  can be formed, for example, as a tape attached to a bottom surface of the first driver IC chip  25 . The tape comes into surface contact with both the first heat transfer member  125  and the first driver IC chip  25  and can be made of resin materials such as epoxy or silicon. Heat generated in the first driver IC chip  25  is transferred to the first heat transfer member  101  on the substrate member  22  through the second heat transfer member  125 , and then transferred from the first heat transfer member  101  to the printed circuit board  30  via the first and second ground lines  105   a ,  105   b.    
     The embodiment of  FIGS. 2 and 3  enable efficient removal of heat from the first driver IC chip  25  to the PCB  30  via a heat transfer path including the second heat transfer member  125 , the first heat transfer member  101  and the first and second ground lines  105   a  and  105   b.    
       FIG. 5  is a cross-sectional view showing a first driver assembly  20 B according a second embodiment. The first driver assembly  20 B is substantially the same as the first driver assembly  20 A of  FIGS. 2 and 3  except that a heat transfer filler  130  is provided between the substrate member  22  and the first driver IC chip  25  instead of the second heat transfer member  125 . Description of components in the second embodiment having the same function as those of the first embodiment will be omitted herein for the sake of brevity. 
     The first driver assembly  20 B may include, among other components, a substrate member  22 , a first driver IC chip  25 , a heat transfer member  101  and a heat transfer filler  130 . The heat transfer filler  130  can be formed between the substrate member  22  an the first driver IC chip  25  to cover the opening  113  of the substrate member and the circumference thereof. In other words, the heat transfer filler  130  can be formed not only on the first and second signal lines  103  and  107 , the first and second ground lines  105   a  and  105   b , the heat transfer member  101  and the substrate  111  exposed by the opening  113 , but also on the inner edge area of the insulation film  115  adjacent to the opening  113 . 
     The heat transfer filler  130  can be formed from a material that is electrically non-conductive but thermally conductive. The heat transfer filler  130  is electrically non-conductive, and hence, electrical short between the first driver IC chip  25  and the first and second signal lines  103  and  107  is prevented. The heat transfer filler  130  can be formed from materials such as an epoxy-based material or a silicon-based material. 
     After filling the thermally conductive filler  130  and forming the first and second bumps  127   a ,  127   b  on the substrate member  22 , the first driver IC chip  25  is depressed to connect the first and second signal lines  103  and  107  on the substrate member  22  to the conductive pattern lines  103  using the first and second bumps  127   a  and  127   b . Subsequently, the heat transfer filler  130  can be cured through a curing process using heat or laser beam. 
     In order to increase the amount of heat transferred, it is advantageous to have the heat transfer filler  130  come into contact with the first driver IC chip  25  as much as possible. The heat transfer filler  130  can be formed to make contact with the entire rear-surface of the first driver IC chip  25 . 
     The second embodiment enables heat generated in the first driver IC chip  25  to be transferred to the heat transfer member via a heat transfer path including the heat transfer filler  130 , the heat transfer member  101 , the first ground line  105   a  and the second ground line  105   b.    
       FIG. 6  is a plan view illustrating a first driver assembly  20 C according a third embodiment. The first driver assembly  20 C is substantially the same as the first driver assemblies  20 A and  20 B except that the first driver assembly  20 C includes extra heat transfer lines  109   a ,  109   b  connected to the first heat transfer member  101  in addition to the first and second ground lines  105   a ,  105   b  of the first driver assembly  20 A. Description of components in the first driver assembly  20 C having the same function as those of the first driver assembly  20 A will be omitted herein for the sake of brevity. 
     The conductive pattern lines  30  in the first driver assembly  20 C include the first and second heat transfer lines  109   a ,  109   b  in addition to the first and second signal lines  106 ,  107  and the first and second ground lines  105   a ,  105   b.    
     Unlike the first driver assembly  20 A, the first and second ground lines  105   a ,  105   b  can be disconnected from the first heat transfer member  101  since the first and second heat transfer lines  109   a ,  109   b  form a heat path to transfer the heat from the first driver IC  25 . 
     The first and second heat transfer lines  109   a ,  109   b  can be simultaneously formed using the same process for forming the first heat transfer member  101 , the first and second signal lines  103  and  107 , and the first and second ground lines  105   a  and  105   b . Therefore, the first and second heat transfer lines  109   a ,  109   b  may be made in the same layer and made from the same material as the first and second signal lines  106  and  107 , and the first and second ground lines  105   a ,  105   b.    
     To increase the heat transfer, each of the first and second heat transfer lines  109   a ,  109   b  can have a width wider than the first and second signal lines  106 ,  107 . If an extra margin remains in the substrate member  22 , the first and second heat transfer lines  109   a ,  109   b  can be formed to have a wider width to increase the heat transfer. 
       FIG. 7  is a flowchart illustrating a method for transferring heat from the driver IC chip  25  to the PCB  30 , according to one embodiment. The driver IC chip  25  is operated  710  to generate signals to the display panel  10 . The generated signals may be scan signals transmitted over the scan lines of the display panel  10  or data signals transmitted over the data lines of the display panel  10 . As a result of the operation, heat is generated by the driver IC chip  25 . 
     The heat generated by the driver IC chip  25  is transferred  720  to a heat transfer element below the bottom surface of the driver IC chip  25 . The heat transfer element may be the heat transfer member  125  (see  FIGS. 3 and 4 ) or the heat transfer filler  130  (see  FIG. 5 ). 
     The heat is then transferred  730  from the heat transfer element to the heat transfer member  101  formed on the substrate  111 . The heat is then transferred  740  from the heat transfer member  101  to a component (e.g., PCB) with a lower temperature via one or more conductive pattern lines  103  formed on the substrate  111 . 
     Embodiments allow heat generated in a driver IC chip of a COF to be effectively transferred to other components (e.g., the PCB  30 ) via a heat path including a heat transfer member. By reducing the temperature of the driver IC chip, malfunction and damage of the driver IC chip can be prevented. 
     Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.