Abstract:
A packaging substrate device includes: a first laminate including a first ceramic substrate and a first copper pattern disposed on an upper surface of the first ceramic substrate; and a second laminate disposed over the first copper pattern and including a second ceramic substrate, a second copper pattern that is disposed on an upper surface of the second ceramic substrate, and a through hole extending through the second ceramic substrate and the second copper pattern to expose a copper portion of the first copper pattern. A light emitting semiconductor die can be mounted on the copper portion within the through hole. Efficient heat dissipation can be achieved through the first laminate.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority of Taiwanese application no. 098112167, filed on Apr. 13, 2009. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to a package device and a method for making the same, more particularly to a packaging substrate device, which has relatively high heat dissipation efficiency and is suitable for a chip on board (COB) packaging process, a method for making the packaging substrate device, and a packaged light emitting device. 
         [0004]    2. Description of the Related Art 
         [0005]    During emission of light, light emitting diodes (LEDs) can generate considerable heat that affects adversely the lifetime and power efficiency of the LEDs. When the temperature of the LEDs is increased to above 100° C., the lifetime and power efficiency of the LEDs will be reduced rapidly. Thus, it is necessary to package the LEDs by using package devices with better heat dissipation efficiency to prolong the LEDs&#39; lifetime and to maintain high power efficiency of the LEDs. 
         [0006]    In order to increase the heat dissipation efficiency, packaging substrate devices are commonly used nowadays. In a process for packaging a high-power LED using a packaging substrate device, a LED die is first mounted on a heat dissipation sheet using solder paste or heat dissipation paste to reduce a thermal resistance of the packaging substrate device. Then, the heat dissipation sheet is mounted onto a heat dissipation substrate using solder paste or heat dissipation paste such that the heat of the heat dissipation sheet can be transferred to the heat dissipation substrate. Generally, a heat dissipation sheet with large thickness has an efficient heat dissipation efficiency. A heat dissipation substrate associated with such a heat dissipation sheet must be able to dissipate heat rapidly and must possess sufficient structural strength in order to efficiently dissipate heat to the outside. Commonly used heat dissipation substrates include metal core printed circuit boards (MCPCB) and ceramic substrates. 
         [0007]    With increasing development of LED technologies, the power efficiency of the LEDs is getting higher and higher. Thus, there is a need to develop a packaging substrate device with a reduced thermal resistance between the LED die and the substrate. 
       SUMMARY OF THE INVENTION 
       [0008]    Therefore, an object of the present invention is to provide a packaging substrate device, which has relatively high heat dissipation efficiency and is suitable for a Chip on board (COB) packaging process. 
         [0009]    Another object of the present invention is to provide a method for making the packaging substrate device. 
         [0010]    Yet another object of the present invention is to provide a packaged light emitting device including the packaging substrate device. 
         [0011]    According to one aspect of this invention, a packaging substrate device comprises: 
         [0012]    a first laminate including a first ceramic substrate and a first copper pattern disposed on an upper surface of the first ceramic substrate; and 
         [0013]    a second laminate disposed over the first copper pattern and including a second ceramic substrate, a second copper pattern that is disposed on an upper surface of the second ceramic substrate, and a through hole extending through the second ceramic substrate and the second copper pattern to expose a copper portion of the first copper pattern. 
         [0014]    Preferably, the first laminate further includes a backside copper layer covering a lower surface of the first ceramic substrate. 
         [0015]    Furthermore, the packaging substrate device further comprises a conductive mass disposed in the through hole to electrically connect to the copper portion of the first copper pattern. The conductive mass should be made of a material with excellent electrical conductivity and thermal conductivity, is preferably a copper mass, and is eutectic bonded to the first copper pattern. 
         [0016]    The first and second copper patterns are made of copper or a copper alloy that can be eutectic bonded to the ceramic substrates. The first and second ceramic substrates can be made of, for example, Al 2 O 3 , AlN, TiO 2 , SiO 2 , ZrO 2 , ZnO, 2MgO.SiO 2 , or BaTiO 3 , and are preferably made of Al 2 O 3  or AlN. 
         [0017]    The packaging substrate device of the present invention is especially suitable for a vertical type LED die. In the packaging substrate device, the first and second copper patterns are electrically isolated from each other by using the second ceramic substrate. A semiconductor die can be packaged in the packaging substrate device by COB packaging, and has a first electrode electrically connected to the first copper pattern and a second electrode wire-bonded to the second copper pattern. Therefore, the light emitting diode can electrically connect to outer circuits using the packaging substrate device of this invention. 
         [0018]    Furthermore, the semiconductor die can be mounted in the through hole and directly bonded to the first copper pattern. Therefore, the heat generated by the semiconductor die can be transferred to the first copper pattern, the first ceramic substrate and the backside copper layer for dissipation. Moreover, since the packaging substrate device according to the present invention is provided without using the solder paste or the heat dissipation paste, the heat dissipation efficiency of the packaging substrate device can be enhanced. 
         [0019]    Besides, by provision of the conductive mass, the distance for wire-bonding the semiconductor die to the second copper pattern can be shortened. 
         [0020]    According to another aspect of this invention, a method for making a packaging substrate device comprises: 
         [0021]    (a) patterning a first copper layer covering an upper surface of a first ceramic substrate of a first laminate to form a first copper pattern on the upper surface of the first ceramic substrate; 
         [0022]    (b) patterning a second copper layer covering an upper surface of a second ceramic substrate of a second laminate to form a second copper pattern on the upper surface of the second ceramic substrate; 
         [0023]    (c) forming a through hole to extend through the second laminate for receiving an electronic element; 
         [0024]    (d) placing the second laminate onto the first laminate such that the second ceramic substrate is in contact with the first copper pattern; and 
         [0025]    (e) heating the first and second laminates such that the first copper pattern is bonded to the second ceramic substrate. 
         [0026]    According to yet another aspect of this invention, a packaged light emitting device comprises: 
         [0027]    a first laminate including a first ceramic substrate and a first copper pattern disposed on an upper surface of the first ceramic substrate; 
         [0028]    a second laminate disposed over the first copper pattern and including a second ceramic substrate, a second copper pattern that is disposed on an upper surface of the second ceramic substrate, and a through hole extending through the second ceramic substrate and the second copper pattern to expose a copper portion of the first copper pattern; and 
         [0029]    a semiconductor die mounted on the copper portion of the first copper pattern, and having a first electrode electrically connected to the first copper pattern and a second electrode wire-bonded to the second copper pattern. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0030]    Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments of the invention, with reference to the accompanying drawings, in which: 
           [0031]      FIGS. 1(   a ) and  1 ( b ) show a first laminate before and after a patterning step of a method for making a packaging substrate device according to the first embodiment of the present invention; 
           [0032]      FIGS. 2(   a ) to  2 ( c ) show a second laminate before and after a patterning step of a method for making a packaging substrate device according to the first embodiment of the present invention; 
           [0033]      FIG. 3  shows the second laminate of  FIG. 2(   c ) after a through hole forming step according to the first embodiment of the present invention; 
           [0034]      FIG. 4  is a top view of the packaging substrate device according to the first embodiment of the present invention; 
           [0035]      FIG. 5  is a top view of a packaged light emitting device according to the first embodiment of the present invention; 
           [0036]      FIG. 6  is a top view of the packaging substrate device according to the second embodiment of the present invention; and 
           [0037]      FIG. 7  is a top view of a packaged light emitting device according to the second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0038]    Before the present invention is described in greater detail with reference to the accompanying preferred embodiments, it should be noted herein that like elements are denoted by the same reference numerals throughout the disclosure. 
         [0039]    A method for making a packaging substrate device according to the first embodiment of the present invention will be described hereinafter with reference to  FIGS. 1 to 4 . 
         [0040]    The method for making the packaging substrate device  100  ( FIG. 4 ) includes: (i) patterning a first laminate  1  ( FIG. 1(   b )); (ii) patterning a second laminate  2  ( FIGS. 2(   b ) and  2 ( c )); (iii) forming a through hole  221  (FIG.  3 ) to extend through the second laminate  2  for receiving an electronic element (i.e., a semiconductor die  3  shown in  FIG. 5) ; (iv) placing the second laminate  2  onto the patterned first laminate  1 ; and (v) heating and bonding the patterned first and second laminates  1  and  2  to each other. 
         [0041]    Referring to  FIG. 1(   a ), the first laminate  1  includes a first ceramic substrate  12 , a first copper layer  11  covering an upper surface of the first ceramic substrate  12 , and a first backside copper layer  13  covering a lower surface of the first ceramic substrate  12 . The first laminate  1  may be a commercially available product, or may be made using a direct bonding copper method. 
         [0042]    As shown in  FIG. 1(   b ), the first copper layer  11  is patterned to form a first copper pattern  11 ′ on the upper surface of the first ceramic substrate  12  and to form three first positioning elements  111  in a region of the first copper pattern  11 ′. In this embodiment, the first positioning elements  111  are circular recesses. Details concerning the patterning of the copper layer  11  are omitted herein since the patterning can be conducted using any conventional PCB lithography process and etching process. 
         [0043]    Referring to  FIG. 2(   a ), the second laminate  2  includes a second ceramic substrate  22 , a second copper layer  21  covering an upper surface of the second ceramic substrate  22 , and a second backside copper layer  23  covering a lower surface of the second ceramic substrate  22 . The second laminate  2  is prepared using a direct bonding copper method. 
         [0044]    In the preferred embodiment, the second laminate  2  has an area smaller than that of the first laminate  1 , and the first and second ceramic substrates  12  and  22  are made of aluminum oxide. 
         [0045]    As shown in  FIGS. 2(   b ) and  2 ( c ), the second copper layer  21  is patterned to form a second copper pattern  21 ′ on the upper surface of the second ceramic substrate  12 , and the second backside copper layer  23  is patterned to form three second positioning elements  231  on the lower surface of the second ceramic substrate  22 . Each second positioning element  231  is in a form of a circular protrusion for interference fit with the circular recess of the first positioning element  111 . Alternatively, the second positioning elements  231  may be square or triangular protrusions when the first positioning elements  111  are square or triangular. The second positioning elements  231  may also be formed as recesses when the first positioning elements  111  are protrusions. The height of the protrusions of the second positioning elements  231  is substantially equal to the depth of the recesses of the first positioning elements  111 . The second positioning elements  231  can be respectively placed in the first positioning elements  111  on the first ceramic substrate  12 . 
         [0046]    In other embodiments, the protrusions of the second positioning elements  231  can be replaced by three pillars (not shown) made of ceramic or copper. In this case, the lower surface of the second ceramic substrate  22  is formed with recesses that can be respectively aligned with the recesses of the first positioning elements  111 . Then, each pillar can be placed between the recesses of the first and second positioning elements  111 ,  231 . 
         [0047]    The patterning of the second copper layer  21  and the second backside copper layer  23  may be conducted by conventional PCB lithography process and etching process. 
         [0048]    Referring to  FIG. 3  in combination with  FIG. 2(   c ), the through hole  221  is formed in an etched region  210  of the second copper pattern  21 ′. In this embodiment, the copper in the etched region  210  of the second copper pattern  21 ′ is removed during the patterning of the second copper layer  21  to expose the second ceramic substrate  22  as shown in  FIG. 2(   c ), followed by forming the through hole  221  through the etched region  210  by a laser drilling process. 
         [0049]    Preferably, for ensuring that a portion of the second copper pattern  21 ′ around the through hole  221  is electrically isolated from the first copper pattern  11 ′, the through hole  221  is provided with a size smaller than that of the etched region  210  of the second copper pattern  21 ′. 
         [0050]    The positions and number of the through holes  221  can be varied based on the design requirements, and should not be limited to this embodiment. 
         [0051]    Referring to  FIG. 4 , the second laminate  2  is stacked on the first laminate  1  such that a copper portion of the first copper pattern  11 ′ is exposed from the through hole  221 . The second laminate  2  can be prevented from sliding relative to the first laminate  1  since the protrusions of the second positioning elements  231  are placed in interference fit with the respective recesses of the first positioning elements  111 . The second laminate  2  shields and contacts a large part of the first copper pattern  11 ′, and only a small part of the first copper pattern  11 ′ for electrical outlet connection is exposed from the through hole  221 . 
         [0052]    The stack of the first and second laminates  1  and  2  is placed in a high temperature furnace at an atmosphere having oxygen content lower than 10 ppm to conduct a direct copper bonding (DCB) process at a temperature that is lower than the melting point of copper (about 1083° C.) and higher than the eutectic temperature of the copper-copper oxide eutectic (1063° C.) 
         [0053]    The packaging substrate device  100  shown in  FIG. 4  can be used for packaging a semiconductor die, especially a vertical type semiconductor LED die. 
         [0054]    Referring to  FIG. 5 , a packaged light emitting device  200  according to the first embodiment of the present invention is shown to include the packaging substrate device  100  of  FIG. 4  and a vertical type light emitting semiconductor die  3 . 
         [0055]    The light emitting semiconductor die  3  is disposed in the through hole  221 , and is directly mounted on the copper portion of the first copper pattern  11 ′ using a COB packaging process. The semiconductor die  3  has a first electrode (not shown) electrically connected to the first copper pattern  11 ′ and a second electrode wire-bonded to the second copper pattern  21 ′ via a bonding wire  30 . Because the first and second copper patterns  11 ′,  21 ′ are electrically isolated from each other by the second ceramic substrate  22 , a short circuit between the first electrode and the bonding wire  30  can be prevented. The distance for wire-bonding the semiconductor die  3  can be reduced through the use of the multi-layered structure of the present invention. The packaged light emitting device  200  can further include an encapsulation resin layer, a fluorescent layer, a lens, etc., based on the design of the packaged light emitting device  200 . In an embodiment, a transparent encapsulation resin is filled in a space confined by the through hole  221  and the first copper layer  11 . 
         [0056]      FIG. 6  illustrates a packaging substrate device  100 ′ according to the second embodiment of the present invention. The second embodiment differs from the first embodiment only in that the packaging substrate device  100 ′ further includes a conductive mass (copper mass)  4 , which is disposed in the through hole  221  to electrically connect to the copper portion of the first copper pattern  11 ′ and which is electrically isolated from the second copper pattern  21 ′. The conductive mass  4  can be placed in the through hole  221  and on the copper portion of the first copper pattern  11 ′ prior to the heating of the first and second laminates  1  and  2  so that it is mounted to the copper portion of the first copper pattern  11 ′. Thereafter, the semiconductor die  3  (see  FIG. 7 ) is mounted on the conductive mass  4  in this embodiment. Preferably, the conductive mass  4  is co-planar with the second copper pattern  21 ′ such that the bonding wire  30  that bonds the semiconductor die  3  to the second copper pattern  21 ′ can be shortened. Alternatively, the conductive mass  4  can be lower or higher than the second copper layer  21 . 
         [0057]      FIG. 7  illustrates a packaged light emitting device  200 ′ according to the second embodiment of the present invention. The packaged light emitting device  200 ′ according to the second embodiment of the present invention is shown to include the packaging substrate device  100 ′ of  FIG. 6  and alight emitting semiconductor die  3  that is mounted on the conductive mass  4 . 
         [0058]    While the present invention has been described in connection with what are considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretations and equivalent arrangements.