Patent Publication Number: US-2016233148-A1

Title: Semiconductor package structure including heat dissipation elements

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority of Taiwanese Patent Application No. 104104082, filed on Feb. 6, 2015. 
     FIELD 
     The disclosure relates to a semiconductor package structure, more particularly to a semiconductor package structure that is used in a display panel and that includes heat dissipation elements. 
     BACKGROUND 
     With the development of liquid crystal display technology, it is now a common requirement for refresh rates of 4k HD displays (having a resolution of 3840 ×2160 pixels) and three dimensional (3D) displays to be increased from 60 Hz to 120 Hz. The requisite rise in refresh rates has greatly increased the loading of display driver integrated circuits (IC). During operation, if the heat generated by the display driver IC is not dissipated efficiently, hot spots will be formed in certain regions of the display driver IC and will cause IC malfunction. 
     Referring to  FIG. 1 , a conventional semiconductor package structure  1  (similar to the semiconductor package structure disclosed in US 2008/0023822 A1) is disposed between and connected to a display panel  2  and a printed circuit board  3 . 
     The semiconductor package structure  1  includes a flexible substrate  11 , a driver IC  12  disposed on the flexible substrate  11 , an aluminum heat dissipation element  13  disposed on the flexible substrate  11 , and a reinforcement element  14  disposed on the heat dissipation element  13 . The heat dissipation element  13  is disposed between the driver IC  12  and the reinforcement element  14 . The flexible substrate  11  includes spaced-apart input and output ends  111 ,  112 . The input end  111  is connected to the printed circuit board  3 . The output end  112  is connected to the display panel  2 . 
     The display panel  2  has a back surface  21  that is adjacent to a backlight unit (not shown), and a front surface  22  that is laminated with a polarizer (not shown) and that is used for displaying an image. A frame unit is used for assembling the semiconductor package structure  1 , the display panel  2  and the backlight unit therein to form a liquid crystal display module. 
     Heat generated in the semiconductor package structure  1  can be dissipated from the driver IC  12  to two ends of the flexible substrate  11  via the heat dissipation element  13 . That is, an effective heat dissipation region of the semiconductor package structure  1  is limited to the two ends of the flexible substrate  11 . Furthermore, with the miniaturized and lightweight requirements for a display module, the frame unit  4  that contacts the semiconductor package structure  1  is usually made of a lightweight reinforced plastic material instead of aluminum. The reinforced plastic material is a composite material that includes a major component of epoxy resin having a thermal conductivity of about 0.19 W/mK. Compared with aluminum, having a thermal conductivity of about 237 W/mK, the reinforced plastic material is less effective in terms of heat dissipation. 
     Due to the abovementioned problem of inefficient heat dissipation, during operation, the temperature and size of the hot spots will continuously increase, causing more hot spots to form in the flexible substrate  11  and resulting in IC malfunction and deteriorated display quality. 
     SUMMARY 
     Therefore, an object of the disclosure is to provide a semiconductor package structure that has improved heat dissipation capability, so that temperatures at hot spots can be lowered and IC malfunction can be prevented. 
     According to an aspect of the present disclosure, a semiconductor package structure includes a flexible substrate, a semiconductor element, a printed circuit board, a first heat dissipation element and a second heat dissipation element. 
     The flexible substrate includes first and second insulation layers, and a first wiring layer that is disposed between the first and second insulation layers and that includes input and output ends. The semiconductor element is disposed on and electrically connected to the first wiring layer. The printed circuit board is disposed adjacent to the input end of the first wiring layer and includes a second wiring layer that is electrically connected to the first wiring layer. The first heat dissipation element is disposed on and connected to the printed circuit board and is spaced apart from the second wiring layer. The second heat dissipation element has a main portion that is disposed on and connected to either one of the first and second insulation layers, and a first extension portion that connects and extends outwardly from the main portion to contact the first heat dissipation element on the printed circuit board. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the present disclosure will become apparent in the following detailed description of the embodiments with reference to the accompanying drawings, of which: 
         FIG. 1  is a fragmentary, partly cross-sectional view of a conventional semiconductor package structure; 
         FIG. 2  is a fragmentary perspective view of a first embodiment of a semiconductor package structure according to the present disclosure; 
         FIG. 3  is a fragmentary, partly cross-sectional view of the first embodiment taken along line III-III of  FIG. 2 ; 
         FIG. 4  is a fragmentary perspective view of a second embodiment of the flexible substrate semiconductor package structure according to the present disclosure; 
         FIG. 5  is a fragmentary, partly cross-sectional view of the second embodiment taken along line V-V of  FIG. 4 ; 
         FIG. 6  is a fragmentary perspective view of a third embodiment of the flexible substrate semiconductor package structure according to the present disclosure; and 
         FIG. 7  is a fragmentary, partly cross-sectional view of the third embodiment taken along line VII-VII of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION 
     Before the disclosure is described in greater detail with reference to the accompanying embodiments, it should be noted herein that like elements are denoted by the same reference numerals throughout the disclosure. 
     Referring to  FIGS. 2 and 3 , a first embodiment of a semiconductor package structure  5  according to the present disclosure is adapted to be used with a display panel  6  of a display module, and includes a flexible substrate  51 , a semiconductor element  52 , a printed circuit board  54 , a first heat dissipation element  542  and a second heat dissipation element  53 . The display panel  6  has a back surface  61  that is adjacent to a backlight unit (not shown), and a front surface  62  that is laminated with a polarizer (not shown) and that is used for displaying an image. 
     It is worth mentioning that the display panel  6  may be a liquid crystal display panel or an active matrix organic light emitting diode (AMOLED) display panel. 
     The flexible substrate  51  includes first and second insulation layers  514 ,  515 , and a first wiring layer  513  that is disposed between the first and second insulation layers  514 ,  515 , that includes spaced-apart input and output ends  511 ,  512 , and that has two spaced-apart connection portions  516 . The connection portions  516  are exposed from the first insulation layer  514  and are spaced apart from the input end  511 . The first wiring layer  513  is made of copper, which has superior electrical and thermal conductivities. The second insulation layer  515  may be used as a support layer and may be made of polyimide (PI) film. The first insulation layer  514  may be used as a solder resist layer, may be mainly made of polyimide resin, and is used for protecting the first wiring layer  513 . 
     In the first embodiment, the semiconductor element  52  is a driver IC. The semiconductor element  52  is disposed between the input and output ends  511 ,  512 , and is disposed on and electrically connected to the first wiring layer  513 . The semiconductor element  52  has top and bottom surfaces  521 ,  524 , a lateral surface  522  interconnecting the top and bottom surfaces  521 ,  524 , and two spaced-apart connection members  523  that are formed on and extend from the bottom surface  524  oppositely of the top surface  521  to respectively contact the connection portions  516  of the first wiring layer  513 . The lateral surface  522  of the semiconductor element  52  is coated with a first encapsulant  55  that is made of, e.g., an electrically insulating resin. The connection members  523  are made of gold. The connection portions  516  are coated with tin. The semiconductor element  52  is fixedly connected to the first wiring layer  513  by eutectic bonding or using anisotropic conductive paste (ACP). Since the method of connecting the connection members  523  to the connection portions  516  is well-known in the art and is not the essence of the present disclosure, the method of connection will not be elaborated hereinafter for the sake of brevity. 
     The printed circuit board  54  is disposed adjacent to the input end  511  of the first wiring layer  513  and includes a second wiring layer  541  that is electrically connected to the first wiring layer  513 . In the first embodiment, the second wiring layer  541  is made of a material including copper. 
     The first heat dissipation element  542  is disposed on and connected to the printed circuit board  54 , is spaced apart from the second wiring layer  541 , and is made of a material including metal. Preferably, the first heat dissipation element  542  is made of a material including copper. 
     To be more specific, the second wiring layer  541  and the first heat dissipation element  542  may each independently be a copper-plated metal pad that is further plated with a nickel/gold (Ni/Au) layer by a surface finish process. Since gold has superior anti-oxidation properties, surface oxidation of the second wiring layer  541  and the first heat dissipation element  542  can be prevented. 
     The second heat dissipation element  53  has a main portion  531 , a first extension portion  532  and a second extension portion  533 . The main portion  531  of the second heat dissipation element  53  is disposed on and connected to one of the first or second insulation layers  514 ,  515 . In the first embodiment, the main portion  531  is disposed on and connected to the second insulation layer  515 , and corresponds in position to the semiconductor element  52 . The first extension portion  532  is connected to and extends outwardly from the main portion  531  to contact the first heat dissipation element  542  on the printed circuit board  54 . The second extension portion  533  is connected to and extends from the main portion  531  toward the output end  512 . The second heat dissipation element  53  is made of a material including metal. In the first embodiment, the second heat dissipation element  53  is made of a material including copper, which has a thermal conductivity of about 401 W/mK. 
     It is worth mentioning that the first heat dissipation element  542  of the printed circuit board  54  and the second heat dissipation element  53  may each also be independently made of a material including carbon composite that has a thermal conductivity of up to 400 W/mK. Compared with the conventional aluminum heat dissipation element  13  having a thermal conductivity of 237 W/mK, the first heat dissipation element  542  and the second heat dissipation element  53  can achieve better heat dissipation and can lower process costs. 
     In use, an electrical signal is transmitted from the second wiring layer  541  of the printed circuit board  54 , passes through the first wiring layer  513  of the flexible substrate  51 , and reaches the semiconductor element  52 . The semiconductor element  52  undergoes joule heating to transfer the electrical signal into heat and becomes a heat source. Since the main portion  531  of the second heat dissipation element  53  is disposed on and connected to the second insulation layer  515 , and corresponds in position to the heat source (i.e., the semiconductor element  52 ), heat generated by the semiconductor element  52  can be effectively transferred to the first heat dissipation element  542  of the printed circuit board  54  through the first extension portion  532 . Moreover, copper wirings on the printed circuit board  54  can increase the effective area of heat dissipation so as to further prevent the semiconductor element  52  from malfunctioning by being overheated. 
     Referring to  FIGS. 4 and 5 , a second embodiment of the semiconductor package structure  5  has a structure similar to that of the first embodiment. The differences are described hereafter. 
     In the second embodiment, the top surface  521  of the semiconductor element  52  is coated with a second encapsulant  56 . The second encapsulant  56  is made of an electrically insulating resin. The first heat dissipation element  542  is disposed on the printed circuit board  54  oppositely of the second wiring layer  541 . The main portion  531  of the second heat dissipation element  53  is disposed on and connected to the first insulation layer  514 , and is disposed between the input end  511  and the semiconductor element  52 . The first extension portion  532  is connected to and extends outwardly from the main portion  531  along a lateral side of the printed circuit board  54  to contact the first heat dissipation element  542 . The second extension portion  533  is connected to and extends from the main portion  531  over the first and second encapsulants  55 ,  56  toward the output end  512 . Specifically, the second extension portion  533  covers and contacts the first and second encapsulants  55 ,  56  on the semiconductor element  52 . 
     Referring to  FIGS. 6 and 7 , a third embodiment of the semiconductor package structure  5  has a structure similar to that of the second embodiment. The differences are described hereafter. 
     In the third embodiment, the second encapsulant  56  and the second extension portion  533  are omitted. 
     To sum up, by virtue of the first extension portion  532  of the second heat dissipation element  53  and the first heat dissipation element  542 , heat generated by the semiconductor element  52  can be effectively transferred from the semiconductor element  52  to the first heat dissipation element  542  and be dissipated from the first heat dissipation element  542 . The nickel/gold-plated first heat dissipation element  542  has better resistance against surface oxidation. Moreover, the copper wirings on the printed circuit board  54  can increase the effective area of heat dissipation. Therefore, the semiconductor element  52  may be effectively cooled and prevented from mal functioning due to overheating. 
     While the disclosure has been described in connection with what are considered the exemplary embodiments, it is understood that this disclosure is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.