Abstract:
An apparatus of antenna with heat slug and its fabricating process are provided, in which the antenna with heat slug can be realized with a single sheet or double sheets of metal. Each single sheet of metal can be achieved by simply cutting and bending a metal plate. Thereby, it is a simple and low-cost fabricating process. In the known fabricating process of integrated circuit, the heat slug and the antenna can be combined in a module at the same step. Therefore, integrating the antenna with heat slug in a fabricating process needs not to develop a new process.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention generally relates to an antenna and heat slug, and a method of forming the same, and more specifically to an apparatus and fabricating process of an antenna with heat slug to be used in a multi-chip module (MCM) package.  
       BACKGROUND OF THE INVENTION  
       [0002]     The rapid development of integration modules has gained the increasing attention in a multi-chip-module package. Because a multi-chip-module includes multiple chips, the energy consumption is usually high in a single package, which leads to the need of integrating a heat slug in the package for heat dissipation to avoid the over-heating problem caused by the high energy consumption. Currently, the RF front-end module (RF FEM) has successfully integrated the balance/unbalance (balun) transformer, the power amplifier, the duplexer, the switch, the band-pass filter and the low noise amplifier (LNA) into a single package. Although the RF FEM is highly integrated, the antenna, being the front-most element, is still placed in a different module. As the demands of the integration increases, it is inevitable to integrate the antenna into the same RF FEM to achieve an even higher integration.  
         [0003]      FIGS. 1A-1D  show a packaging process with a heat slug.  FIG. 1A  is a side view of a multi-chip-module after the steps of die attach and wire bond. Dies  120  are attached and bonded on a substrate  120  via the gold wire  122 .  FIG. 1B  is a side view of a multi-chipmodule after the steps of heat slug attach and compound molding. After attaching a heat slug  114  on the substrate  130 , the packaged module is filled with the epoxy  160  via a dispenser. The heat slug  114  usually has a round shape and a plurality of support elements  115 , as shown in  FIG. 1C . The heat slug  114  is usually made by cutting or molding a metal sheet. After folding the metal sheet along the bend line  116  into a π-like shape, the heat slug  114  is placed on the substrate  130  to form a multi-chip-module.  FIG. 1D  is a side view of the multi-chip-module after a plurality of metal solder balls  150  are placed into the multi-chip-module.  
         [0004]     U.S. Pat. No. 6,686,649 disclosed an antenna and a shield fabricated respectively on both sides of a dielectric cap, and the aforementioned structure is placed on top of the chip in the packaging process to achieve the high integration. However, the design is complicated and the fabrication cost is high. In addition, the placement of the dielectric cap is not suitable for the current IC packaging methods.  
         [0005]     U.S. patent publication 2004/0,032,371 disclosed an apparatus of antenna with an electromagnetic shield used in the mobile products. The metal antenna and electromagnetic shield are formed respectively on the top and the bottom sides of a dielectric body. The dielectric body can be fixed on a printed circuit board (PCB). This method incurs a higher fabrication cost for the dielectric body. In addition, the antenna and the electromagnetic shield require the deposit and plate steps in the fabricating process as well as the addition of a metal pattern, both increase the fabrication cost.  
         [0006]     European Patent 1,126,522 disclosed an antenna and a plurality of ground surfaces in a multi-layered structure formed respectively on both sides of a dielectric body. The elements in this structure are vertically connected. For example, the antenna feed and ground lines are performed using via holes. In other words, the drilling and the metal filling steps must be included in the fabricating process. As this packaging method is a non-standard IC packaging process, the cost is high.  
         [0007]     Because of the aforementioned problems, it is imperative to provide an antenna having a simple structure and a low fabrication cost that can be integrated into a packaging to reduce the overall cost.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention has been made to overcome the aforementioned drawback of conventional antenna fabricating process. The primary object of the present invention is to provide an apparatus and a cost-effective fabricating process of antenna with heat slug.  
         [0009]     Another object of the present invention is to provide an apparatus and a fabricating process of antenna with heat slug that can be integrated into a package without incurring additional packaging steps or processes.  
         [0010]     Yet another object of the present invention is to provide an apparatus and a fabricating process of an antenna with heat slug, in which the antenna is simple in structure, easy to fabricate and low in cost.  
         [0011]     The final object of the present invention is to provide an apparatus and a fabricating process of an antenna with heat slug, in which the structure of the antenna with heat slug is either single metal sheet or double metal sheets.  
         [0012]     To achieve the aforementioned objects, the present invention of an apparatus of an antenna with heat slug includes a substrate, an antenna signal transmission line, at least a chip and at least a metal belt, at least a metal sheet, and a mold compound. The substrate has an upper surface and a lower surface. The lower surface includes a plurality of solder balls for electrical connection to an external circuit. The antenna signal transmission line and the metal belt are formed on the upper surface of the substrate. The chips are placed on the upper surface of the substrate and electrically connected to the antenna signal transmission line. The metal sheet has the function of an antenna and the heat slug, and is placed on the upper surface of the substrate. The mold compound at least covers the chips, the antenna signal transmission line and the metal belt.  
         [0013]     According to the present invention, the structure of having at least a metal sheet can be either a single metal sheet or double metal sheets. The structure with single metal sheet can be performed by cutting a metal sheet or molding to a specific shape and then bending the metal sheet. The structure with single metal sheet can further be divided into two types. The first type includes a heat slug having an antenna and a plurality of support elements. The heat slug having an antenna is placed above and kept a distance from the chips. One of the support elements is an antenna feed metal sheet electrically connected to the antenna signal transmission line. The remaining support elements electrically connect to each metal belt. Some of the metal belts can be connected to the ground plane for the apparatus of the invention.  
         [0014]     The second type of the single metal sheet structure includes a heat slug, an antenna, at least a connection metal sheet and an antenna feed metal sheet. The heat slug is placed above and kept a distance from the chips. The lower portion of the heat slug includes a plurality of support elements, which electrically connect to each metal belt, and then to the ground plane. The antenna is placed above and kept a distance from the heat slug. The connection metal sheet is for connecting the antenna and the heat slug. One end of the antenna feed metal sheet is connected to the antenna, and the other end is connected to the antenna signal transmission line.  
         [0015]     In the double metal sheet structure, each of the metal sheets is made by cutting a single metal sheet or molding into a specific shape, and then bending the metal sheet. One of the double metal sheets includes a heat slug and a plurality of support elements. The heat slug is placed above and kept a distance from the chips. The support elements electrically connect to each metal belt, which connects to the ground. In addition, the other sheet of the double metal sheets includes an antenna and an antenna feed metal sheet. The antenna is placed above and kept a distance from the heat slug. One end of the antenna feed metal sheet is connected to the antenna, and the other end is connected to the antenna signal transmission line. The heat slug and the plurality of support elements are covered by a layer of mold compound. The antenna is above the mold compound and the antenna feed metal sheet feeds the signal from the side.  
         [0016]     The fabricating process for the antenna with the heat slug according to the invention includes the following steps: (a) providing a substrate having at least a die attached and wire bonded, and forming an antenna signal transmission line and a plurality of metal sheets, (b) placing an antenna and a heat slug on the upper surface of the substrate and filling a mold compound, and (c) placing a plurality of metal solder balls beneath the lower surface of the substrate.  
         [0017]     According to the present invention, the structure of the antenna can be either a single metal or double metal sheets. Therefore, the step (b) in the aforementioned process can vary slightly. In the structure of single metal sheet, the metal sheet includes a plurality of support elements, and step (b) further includes the following steps: (1) cutting or molding a single metal sheet into a specific shape, (2) bending the metal sheet, (3) placing the metal sheet above the chips, connecting the antenna feed metal sheet and antenna signal transmission line, and connecting each support element and each metal belt, and (4) filling and molding a compound to cover the chips, antenna signal transmission line and a plurality of metal belts.  
         [0018]     On the other hand, in the structure of double metal sheet, one of the metal sheets includes a heat slug and a plurality of support elements, and the other sheet includes an antenna and an antenna feed metal sheet. Step (b) further includes the following steps: (1) cutting or molding the metal sheets into a specific shape, respectively, (2) bending the metal sheets so that there is a 90° angle between the sheet containing the antenna and the antenna feed metal sheet and the sheet containing the heat slug and the support elements, (3) placing the heat slug above the chips and connecting each support element and each metal belt, (4) filling and molding a compound to cover the heat slug, the metal belts and the chips, and (5) placing the antenna above the mold compound and connecting the antenna feed metal sheet and the antenna signal transmission line.  
         [0019]     The antenna with the heat slug of the present invention can be fabricated by simply cutting and bending a single sheet or double metal sheets. The simplicity of the fabrication lowers the overall cost. In addition, the invention fabricated by a single sheet is formed by a monolithic unit. Therefore, installing the antenna and the heat slug can be performed within a single step because the antenna and the heat slug are combined in a single sheet. Therefore, no additional step is required for the installation.  
         [0020]     The foregoing and other objects, features, aspects and advantages of the present invention will become better understood from a careful reading of a detailed description provided herein below with appropriate reference to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]      FIG. 1A  is a side view of a conventional multi-chip-module after the steps of die attach and wire bond.  
         [0022]      FIG. 1B  is a side view of a multi-chip-module after the steps of heat slug attach and compound molding.  
         [0023]      FIG. 1C  shows an expanded view of a conventional heat slug.  
         [0024]      FIG. 1D  shows a side view of a conventional multi-chip module after ball placement.  
         [0025]      FIG. 2  shows a cross-sectional view of the antenna with heat slug according to the present invention, in which the antenna with heat slug is realized with a single metal sheet.  
         [0026]      FIG. 3A  shows a perspective view of the first embodiment according to the present invention.  
         [0027]      FIG. 3B  shows a cross-sectional view of a first embodiment according to the present invention.  
         [0028]      FIG. 3C  is a side view of a first embodiment according to the present invention.  
         [0029]      FIGS. 4A-4E  show the fabricating process of the first embodiment according to the present invention.  
         [0030]      FIG. 5  is a cross-sectional view of a second embodiment according to the present invention.  
         [0031]      FIGS. 6A-6E  show the fabricating process of the second embodiment according to the present invention.  
         [0032]      FIG. 7  shows a cross-sectional view of a third embodiment according to the present invention.  
         [0033]      FIGS. 8A-8G  show the fabricating process of the third embodiment according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0034]      FIG. 2  shows a schematic view of the apparatus of antenna with heat slug according to the present invention, wherein the apparatus is with the structure of single metal sheet. Referring to  FIG. 2 , the apparatus includes at least a chip  220 , an antenna signal transmission line  221 , a plurality of metal belts  240 , an antenna with heat slug unit  210 , a mold compound  260  and a substrate  230 . Chip  220  is placed on an upper surface  231  of substrate  230 , and is connected to antenna signal transmission line  221  and bonding pad  241  by wire  222 . Antenna signal transmission line  221  and metal belts  240  are formed on upper surface  231  of substrate  230 . Sealing body  260  covers chip  220 , antenna signal transmission line  221  and metal belts  240 . Antenna with heat slug unit  210  further includes an antenna feed metal sheet  212 , an antenna  211 , a heat slug  214  and a plurality of support elements  215  (i.e. the structure of single metal sheet  213  with the dashed line). Heat slug  214  with its plurality of support elements  215  is a single monolithic module having the structure of single metal sheet. If the functions of antenna feed metal sheet  212  and antenna  211  are also included into the monolithic structure of heat slug  214  with its plurality of support elements  215 , antenna with heat slug unit  210  becomes a structure of single metal sheet without the dashed line, as shown in  FIG. 2 . Antenna with heat slug unit  210  is placed above chip  220  and is connected to metal belts  240  through support elements  215 . In addition, one end of antenna feed metal sheet  212  is connected to the antenna, and the other end is connected to antenna signal transmission line  221  on upper surface  231  of the substrate  230 . Antenna signal transmission line  221  is also connected to chip  220 . Chip  220  is connected to the external circuit through solder balls  250  beneath the lower surface  232  of substrate  230 .  
         [0035]     It is worth noticing that antenna signal transmission line  221  and metal belts  240  appear to be overlapping in  FIG. 2  because of the viewing angle, although they are not actually connected.  
         [0036]     The following description includes three embodiments of the present invention. The first and the second embodiments are both with the structure of single metal sheet, and the third embodiment is with the structure of double metal sheet.  
         [0037]      FIG. 3A  shows a perspective view of a first embodiment of the present invention. In this embodiment, the antenna with heat slug includes an antenna  311 , an antenna feed metal sheet  312 , at least a connection metal sheet  313 , a heat slug  314 , at least a chip  320 , an antenna signal transmission line  321 , a plurality of metal belts  340 , a mold compound (described and shown in  FIG. 3B ) and a substrate  330 . Antenna  311 , antenna feed metal sheet  312 , at least a connection metal sheet  313 , heat slug  314  and support elements  315  constitute an antenna with heat slug module  310 , which has a single metal sheet structure.  
         [0038]     Substrate  330  has an upper surface  331  and a lower surface  332 . Antenna signal transmission line  321  and a plurality of metal belts are formed on upper surface  331 , where a chip  320  is attached. Chip  320  is connected to antenna signal transmission line  321  and bump pad  341  through metal wire  322 . One end of connect metal sheet  313  is connected to antenna  311 , and the other end is connected to heat slug  314 . The angle between connection metal sheet  313  and antenna  311  is about 90°. The angle between connection metal sheet  313  and heat slug  314  is also about 90°. Therefore, antenna  311  and heat slug  314  are parallel to each other. One end of antenna feed metal sheet  312  is connected to antenna  311 , with a 90° angle between them. The other end of antenna feed metal sheet  312  is connected to antenna signal transmission line  321  to transmit the antenna signal from upper surface  331  of the substrate  330  to antenna  311  in order to excite antenna  311 .  
         [0039]     Furthermore, heat slug  314  has a plurality of support elements  315  for connecting to metal belts  340  and for separating heat slug  314  from chip  320  to avoid direct contact between the two. Metal belts  340  are connected to the ground plane of the electronic device.  
         [0040]      FIG. 3B  is a cross-sectional view of the first embodiment of the present invention. Mold compound  360  is made of such as epoxy resin, to encompass at least chip  320 , part of antenna signal transmission line  321 , and metal belts  340 . Mold compound  360  can also encompass the lower side of antenna  311 , antenna feed metal sheet  312 , and the outer side of support element  315  to protect chip  320  from erosion and oxidation.  
         [0041]     A plurality of solder balls  350  are beneath the lower surface  332  of the substrate  330 . Solder balls  350  are for connecting to the external circuit, motherboard or other electronic devices. In addition to dissipating the heat, heat slug  314  can also be applied to insulate chip  320  from the interference of the antenna radiation signal.  
         [0042]      FIG. 3C  is a side view of a first embodiment according to the present invention. Connection metal sheet  313  is connected to antenna  311  and heat slug  314 , and heat slug  314  is connected to support element  315 . In addition, antenna  311  is connected to antenna feed metal sheet  312 . Therefore, the aforementioned components can all be combined into a monolithic structure by cutting and bending a single metal sheet.  
         [0043]      FIGS. 4A-4E  show the fabricating process of the first embodiment according to the present invention.  
         [0044]     First, at least a chip  320  is attached to upper surface  331  of substrate  330 , on which antenna signal transmission line  321  and a plurality of metal belts  340  are already formed. Metal wire  322  is then formed to bond chip  320 . As shown in  FIGS. 4A and 4B , an epoxy dispenser is applied to attach the chip  320  to substrate  330 , which has bump pad  341 , antenna signal transmission line  321  and a plurality of metal belts  340  thereon.  
         [0045]     Then, a single metal sheet is cut or molded into a specific shape. Connection metal sheet  313 , antenna  311 , heat slug  314  and its plurality of support elements  315  are all combined in a monolithic structure.  FIG. 4C  is a view of an unfolded metal sheet of an antenna with heat slug  310 . The length of antenna feed metal sheet  312  equals to the sum of the length {overscore (AB)} of connection metal sheet  313  and the width {overscore (CD)} of support element  315 , so that antenna feed metal sheet  312  is easily connected to antenna signal transmission line  321 . Because the present invention is monolithic, the fabricating cost can be reduced.  
         [0046]     The single metal sheet is then bended so that heat slug  314  and support elements  315 , connection metal sheet  313  and heat slug  314 , and connection metal sheet and antenna  311  are all perpendicular to each other.  FIG. 4D  shows the shape of the single metal sheet after bending along the dashed line.  
         [0047]     The next step is to mount the single metal sheet to upper surface  331  of the substrate  330 , to connect antenna feed metal sheet  312  to antenna signal transmission line  321 , and each support element  315  to each metal belt  340 ; and to form mold compound  360 . During the mounting, no extra antenna feed circuit is required as antenna feed metal sheet  312  is in direct contact with antenna signal transmission line  321 . Mold compound  360  at least encompasses chip  320 , antenna signal transmission line  321 , and metal belt  340 . Mold compound  360  may also encompass the lower side of antenna  311 , antenna feed metal sheet  312 , and the outer side of support element  315  for holding the module in place.  
         [0048]     Finally, a plurality of solder balls  350  are bonded beneath the lower surface  332  of the substrate  330  for connecting to the external circuits, as shown in  FIG. 4E .  
         [0049]     It is worth noticing that antenna signal transmission line  321  and metal belts  340  appear to be overlapping in  FIGS. 3B, 4B  and  4 E. However, as shown in  FIGS. 3A and 4A , they are actually not connected at all.  
         [0050]     The aforementioned process shows that the steps of the packaging process are identical to the steps in a conventional packaging process shown in  FIG. 1 . The only difference is to replace the conventional heat slug with the heat slug of the present invention. Therefore, the present invention does not require a new fabricating process, and meets the objects of high integration and low manufacturing cost.  
         [0051]      FIG. 5  shows a side view of a second embodiment of the present invention. An antenna with heat slug module  510  has a structure similar to that of the first embodiment. Antenna with heat slug module  510  includes a heat slug  514 , which can dissipate heat as well as act as an antenna. Heat slug  514  has a plurality of support elements  515 , which is also formed in a monolithic structure. One of the plurality of support elements is an antenna feed metal sheet  512  connected to antenna signal transmission line  521  on upper surface  531  of the substrate  530 . The remaining support elements  513  are connected to metal belts  540 , respectively. Some of the metal belts  540  are connected to the ground plane.  
         [0052]      FIGS. 6A-6E  show the fabricating process of the second embodiment according to the present invention.  
         [0053]     The second embodiment has a fabricating process similar to that of the first embodiment. The difference is that the single metal sheet is cut or molded into a different shape in the process. First, as shown in  FIG. 6A , at least a chip  520  is attached to upper surface  531  of substrate  530 , on which antenna signal transmission line  521  and a plurality of metal belts  540  are already formed. Wire bond  522  is then formed to connect chip  320 .  
         [0054]     Then, a single metal sheet is cut or molded into a specific shape. As shown in  FIGS. 6B and 6C , heat slug  514  can be either of the round shape or a rectangular shape, and antenna feed metal sheet  512  can be one of the support elements. In the following bending step, the single metal sheet is bended along dashed line  516 , as shown in  FIGS. 6B and 6C , to make heat slug  514  being perpendicular to support elements  515 .  
         [0055]     The next step is to mount the single metal sheet to upper surface  531  of the substrate  530 , to connect antenna feed metal sheet  512  to antenna signal transmission line  521 , and each support element  515  to each metal belt  540 , and to form mold compound  560 . The height of antenna feed metal sheet  512  is the length of {overscore (EF)} in  FIGS. 6B and 6C .  
         [0056]     Finally, a plurality of solder balls  550  are placed on lower surface  532  of the substrate  530  for connecting to the external circuits, as shown in  FIG. 6E .  
         [0057]      FIG. 7  shows a side view of a third embodiment of the present invention. The third embodiment is similar to the first embodiment of the present invention except that the structure of the antenna with heat slug is double metal sheet. In other words, antenna  711  and antenna feed metal sheet  712  are made of a metal sheet, while heat slug  714  and its plurality of support elements  715  are made of another metal sheet. Support elements  715  of heat slug  714  are for connecting to metal belts  740  and separating heat slug  714  from chip  720  to avoid direct contact. Mold compound  760  at least encompasses the upper side of heat slug  714  and the outer side of support elements  715 . Antenna  711  is mounted above sealing body  760 . Mold compound  760  also acts as a substrate between antenna  711  and heat slug  714 . On the other hand, one end of antenna feed metal sheet  712  is connected to antenna  711  forming a 90° angle, and the other end is connected to antenna signal transmission line  721  so that the antenna signal is fed from antenna feed metal sheet  712  on the side.  
         [0058]     It is worth noticing that antenna signal transmission line  721  and support elements  715  appear to be overlapping in  FIGS. 8D-8G . However, they are actually not connected at all.  
         [0059]      FIGS. 8A-8G  show the fabricating process of the third embodiment of the present invention.  
         [0060]     First, at least a chip  720  is attached to upper surface  731  of substrate  730 , on which antenna signal transmission line  721  and a plurality of metal belts  740  are already formed. Wire bond  722  is then formed to connect chip  320 , as shown in  FIG. 8A .  
         [0061]     Then, the metal sheets are cut or molded into a specific shape, respectively. Because the structure of this embodiment uses double metal sheets, each of the metal sheets must be cut or molded into a different shape in accordance with the design. As the example shown in  FIGS. 8B and 8C , antenna  711  has a rectangular or round shape, while antenna feed metal sheet  712  may have a triangular or rectangular shape. As for heat slug  714  and its plurality of support elements  715 , the metal sheet can be cut or molded into a shape as shown in  FIG. 1C .  
         [0062]     The metal sheets are then bended so that heat slug  714  and support elements  715 , and connection metal sheet  712  and antenna  711  are all perpendicular to each other.  FIGS. 8B, 8C  and iC show the shape of the metal sheets after bending along the dashed lines  716 ,  116 .  
         [0063]     The next step is to mount heat slug  714  to upper surface  731  of the substrate  730 , and to connect each support element  715  to each metal belt  740 , as shown in  FIG. 8D . Then, mold compound  760  is formed to encompass at least chip  720 , a part of antenna signal transmission line  721 , metal belts  740 , the upper side of heat slug  714  and the outer side of support elements  715 , as shown in  FIG. 8E .  
         [0064]     Then, antenna  711  is placed above sealing body  760  and antenna feed metal sheet  712  is connected to antenna signal transmission line  721 , as shown in  FIG. 8F . The height of antenna feed metal sheet  712  is the length {overscore (GH)} of in  FIGS. 8B and 8C .  
         [0065]     Finally, a plurality of solder balls  750  are placed on lower surface  732  of the substrate  730  for connection to the external circuits, as shown in  FIG. 8G .  
         [0066]     In summary, the antenna with heat slug of the present invention, with the structure of using a single metal sheet or double metal sheets, is simple in structure and easy to fabricate. In particular, the structure of single metal sheet takes advantage of a monolithic structure of the antenna with heat slug so that the antenna and the heat slug are simultaneously mounted and sealed inside a package. The process is identical to the conventional packaging process. Therefore, no new process is required. The present invention reduces the manufacturing cost and meets the high integration object.  
         [0067]     Although the present invention has been described with reference to the preferred embodiments, it will be understood that the invention is not limited to the details described thereof. Various substitutions and modifications have been suggested in the foregoing description, and others will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.