Abstract:
An electronic module having an electromagnetic shielding structure and its manufacturing method are provided. At first, a first substrate and a second substrate are separately provided. At least one electronic element and at least one connection pad are formed on a surface of the first substrate. The second substrate includes a conductive film and at least one conductive bump is formed on a surface of the conductive film. The first substrate and the second substrate are laminated together wherein the conductive bump is aligned with and connected to the connection pad to obtain the electronic module.

Description:
FIELD OF THE INVENTION 
       [0001]    The present disclosure relates to an electronic module having an electromagnetic shielding structure and a manufacturing method of the electronic module, and particularly to an electromagnetic shielding structure used in a miniaturized electronic module. 
       BACKGROUND OF THE INVENTION 
       [0002]    For an electronic element, electromagnetic interference (EMI) usually occurs and affects neighboring electronic circuits via electromagnetic induction, electrostatic coupling, or conduction. Disturbance due to electromagnetic interface may degrade performance or cause malfunction of the electronic circuits. Therefore, electromagnetic shielding such as blocking interference of high frequency electromagnetic signals should be considered while designing electronic modules. Furthermore, the progressive miniaturization of electronic modules in recent years will worsen the disturbance, and it is difficult or expensive to build electromagnetic shielding structures within tiny space between electronic circuits. 
         [0003]    Electromagnetic shielding solutions include board-level shielding and package-level shielding. The package-level shielding can be applied to smaller electronic module. For example, conformal shielding and compartment shielding are developed to achieve electromagnetic shielding in small space. A simplified, flexible, easily controllable and cost-effective method for forming an electromagnetic shielding structure in a miniaturized electronic module with high yield rate is desired. 
       SUMMARY OF THE INVENTION 
       [0004]    The present disclosure provides an electronic module having an electromagnetic shielding structure. The electronic module includes a first substrate and a second substrate. At least one electronic element and at least one connection pad are formed on a surface of the first substrate. The second substrate includes a conductive film and at least one conductive bump formed on the conductive film. The conductive bump is connected to the connection pad. 
         [0005]    In an embodiment, the connection pad is electrically connected to a ground pin of the electronic module through a via connection in the first substrate. 
         [0006]    In an embodiment, a ground plane is disposed on the surface of the first substrate or buried in the first substrate. The connection pad is electrically connected to the ground pin through the via connection and/or the ground plane. 
         [0007]    In an embodiment, a gap between the first substrate and the second substrate is filled with an insulating adhesive. 
         [0008]    In an embodiment, the second substrate includes an insulating film covering the surface of the conductive film and the conductive bump. A top surface of the conductive bump is exposed from the insulating film. 
         [0009]    In an embodiment, the second substrate includes an insulating layer disposed on the other surface of the conductive film. 
         [0010]    In an embodiment, a plurality of conductive bumps are arranged on periphery of the electronic element, and a distance between any two adjacent conductive bumps is less than 1 mm. 
         [0011]    In an embodiment, a portion of the conductive bumps are exposed at a lateral surface of the electronic module, and a protection layer is applied to the lateral surface of the electronic module and the exposed portion of the conductive bumps. 
         [0012]    In an embodiment, the conductive bump has a tapering shape and narrows away from the conductive film. 
         [0013]    Another aspect of the present disclosure provides a manufacturing method of an electronic module having an electromagnetic shielding structure. A first substrate and a second substrate are separately provided. At least one electronic element and at least one connection pad are formed on a surface of the first substrate. The second substrate includes a conductive film and at least one conductive bump formed on a surface of the conductive film. The first substrate and the second substrate are laminated wherein the conductive bump is aligned with and connected to the connection pad. 
         [0014]    In an embodiment, the connection pad is formed on the surface of the first substrate by surface-mount technology before the electronic element is mounted on the first substrate. 
         [0015]    In an embodiment, the connection pad is preheated by heating the ground pin electrically connected to the connection pad. The substrates are stacked by aligning the conductive bump with the connection pad. Then, the stacked substrates are laminated wherein the conductive bump is connected to the connection pad. 
         [0016]    In an embodiment, the conductive bump is formed on the surface of the conductive film by a printing process. 
         [0017]    In an embodiment, the electronic module is cut along the conductive bumps near a boundary of the electronic module to expose a portion of the conductive bumps at a lateral surface of the electronic module. Then, a protection layer is applied to the lateral surface of the electronic module and the exposed portion of the conductive bumps. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The advantages of the present disclosure will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which: 
           [0019]      FIGS. 1A ˜ 1 C are schematic diagrams illustrating a manufacturing method of an electronic module having an electromagnetic shielding structure according to an embodiment of the preset invention; 
           [0020]      FIG. 2  is a schematic diagram illustrating an electronic module having an electromagnetic shielding structure according to another embodiment of the present invention; and 
           [0021]      FIGS. 3A and 3B  are schematic diagrams illustrating layout of the conductive bumps in the electronic module according to the present disclosure. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0022]    The present disclosure will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for purpose of illustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed. 
         [0023]    Please refer to  FIGS. 1A ˜ 1 C, schematic diagrams illustrating a manufacturing method of an electronic module having an electromagnetic shielding structure according to an embodiment of the preset invention. At first, a first substrate  11  is provided ( FIG. 1A ). A plurality of electronic elements  111  for the electronic module are mounted on a first surface  110   a  of the substrate  11 . For example, the electronic elements  111  are mounted on the first surface  110   a  by surface-mount technology (SMT). Leads of the electronic elements  111  are soldered to respective functional pads  132  on the first surface  110   a  by using solders  131 . Before or after the SMT process, a plurality of connection pads  112  are formed on the first surface  110   a  of the first substrate  11  wherein the connection pads  112  are disposed at the positions where the electromagnetic shielding structures will be formed. The connection pads  112  are electrically connected to a ground plane  1121  or ground pins  119   a  of the electronic module through via connections  1120 . The ground plane  1121  is disposed on the first surface  110   a  of the first substrate  11  or buried in the first substrate  11  as an inner ground plane. The ground plane  1121  is electrically connected to the ground pins  119   a . The first substrate  11  may be a rigid printed circuit board, a flexible printed circuit board or any substrate capable of supporting electronic components. A plurality of module pins  119   a - 119   f  are formed on a second surface  110   b  of the first substrate  11  which is opposite to the first surface  110   a . These pins  119   a - 119   f  include power pins, data pins, ground pins (e.g.  119   a ) and other essential pins for different functions. The ground pins  119   a  are directly electrically connected to the connection pads  112  or indirectly electrically connected to the connection pads  112  through the via connections  1120 . 
         [0024]    On the other hand, a second substrate  21  of the electronic module is provided ( FIG. 1B ). The second substrate  21  includes a conductive film  12 , e.g. copper foil, other metal foil or film made of conductive material. Areas of the first substrate  11  and the conductive film  12  are substantially identical. A plurality of micro conductive bumps  122  are formed on a first surface  120  of the conductive film  12 . The positions of the conductive bumps  122  correspond to the positions of the connection pads  112  on the first surface  110   a  of the first substrate  11 . For example, the conductive bumps  122  are made of silver paste by a printing process. An insulating film  123 , e.g. prepreg is provided to separate the electronic elements  111  from the conductive film  12 . The insulating film  123  has a plurality of holes  1230  corresponding to the conductive bumps  122  so that top surfaces of the conductive bumps  122  are exposed from the insulating film  123 . In other words, the insulating film  123  covers the first surface  120  of the conductive film  12  and the conductive bumps  122  except the top surfaces of the conductive bumps  122 . The conductive bumps  122  have a tapering shape and narrow away from the first surface  120 . Hence, it is easier to align the conductive bumps  122  with the connection pads  112  during the PCB stacking process, and the resultant structure has better strength. The prepreg is made of a curable soft material, e.g. resin such as epoxy or polyimide, mixture of resin and glass fiber, ceramic material or glass. In addition, an insulating layer  124 , e.g. prepreg is disposed on a second surface  121  of the conductive film  12  to isolate the conductive film  12  from external influence. The conductive film  12  and the insulating film (e.g. prepreg)  123  and/or the insulating layer  124  are laminated by hot press lamination. Thus, the second substrate  21  is formed. In another embodiment, the insulating layer  124  is disposed on the second surface  121  of the conductive film  12  before the micro conductive bumps  122  are formed on the surface  120  of the conductive film  12 . 
         [0025]    In another embodiment, no holes are formed on the insulating film  123  before the lamination step. Then, during the lamination step, tips of the conductive bumps  122  can protrude from the insulating film  123  to form the holes  1230  on the insulating film  123 . 
         [0026]    Please refer to  FIG. 1C  illustrating the resultant structure of the electronic module  10 . The first substrate  11  formed with the electronic elements  111  and the second substrate  21  are stacked face to face wherein the exposed or protruded conductive bumps  122  of the second substrate  21  are aligned with the connection pads  112  on the first substrate  11 . The stacked structure is laminated to form the electronic module  10  wherein the conductive bumps  122  are connected to or joined onto the corresponding connection pads  112 . 
         [0027]    Furthermore, while forming the conductive bumps  122  by the printing process, additional conductive frames (not shown) may be formed to construct compartments (not shown) for accommodating the electronic elements  111 . Therefore, the electronic module  10  takes advantages of both conformal shielding and compartment shielding to achieve electromagnetic shielding. 
         [0028]    Since the connection pads  112  are electrically connected to the ground plane  1121  or the ground pins  119   a  of the electronic module  10  through the via connections  1120 , the connection pads  112  may be preheated by heating the ground pins  119   a  to slightly melt the connection pads  112  so as to assist bonding between the connection pads  112  and the conductive bumps  122 . For example, a heating element (not shown) is connected to the ground pins  119   a  to provide heat to the ground pins  119   a . The heat is transferred to the via connections  1120 , the ground plane  1121  and the connection pads  112  on the first substrate  11  by means of heat conduction. 
         [0029]    To enhance the isolating effect and the bonding between the first substrate  11  and the second substrate  21 , an underfilling process is performed to inject an insulating adhesive  30  into gaps between the first substrate  11  and the second substrate  21 . An epoxy mixture, for example, can be used in the underfilling process to effectively glue the first substrate  11  and the second substrate  21  together. 
         [0030]    After the lamination step, solder ball placement is performed to join solder balls  130  onto the pins  119   a - 119   f  of the electronic module  10 . The material of the solder balls  130  is tin or tin alloy such as silver-tin alloy, copper-tin alloy, tin-lead alloy or tin-zinc alloy. When the electronic module  10  is soldered to a system printed circuit board (PCB)  40  by using the solder balls  130 , the ground pins  119   a  are electrically connected to the grounding pads  41   a , while the other module pins  119   b ˜ 119   f  such as power pins and data pins are electrically connected to the corresponding functional pads  41   b ˜ 41   f  of the system printed circuit board  40 . 
         [0031]    Please refer to  FIG. 2 , a schematic diagram illustrating structure of an electronic module having an electromagnetic shielding structure according to another embodiment of the present invention. The size of the electronic module can be further reduced by cutting the electronic module along the conductive bumps  122   a  and  122   b  near boundaries of the electronic module. Therefore, the electronic module  20  has a smaller surface area than the electronic module  10  in the above embodiment. The conductive bumps  122   a  and  122   b  are exposed at lateral surfaces of the electronic module  20 . Then, a thin protection layer  50  is applied to the top surfaces and the lateral surfaces of the electronic module  20  and the exposed portions of the conductive bumps  122   a  and  122   b . Under this condition, the insulating layer  124  may be omitted to further reduce the size of the electronic module  20 . 
         [0032]    Please refer to  FIG. 3A , a schematic diagram illustrating layout of the conductive bumps in the electronic module. The conductive bumps  122  are closely arranged on the periphery of the shielded areas  4  where the sensitive electronic elements are located. According to the layout of the sensitive electronic elements, the conductive bumps  122  may be arranged on periphery of the electronic module and/or arranged at inner part of the electronic module. The distance between two adjacent conductive bumps  122  is less than 1 mm. Thus, electromagnetic signals do not pass in and out the surrounded areas  4  laterally so that the electronic elements are shielded from the electromagnetic interference. As shown in  FIG. 3A , there are two shielded areas  4  surrounded by the conductive bumps  122 . It is to be noted that the number of the shielded areas  4  in an electronic module is not limited and it varies according to the performance and quantity of the electronic elements.  FIG. 3B  illustrates another example indicating that only a portion  4   b  of the electronic module should be shielded so that the conductive bumps  122  do not cover all the electronic module. It is to be noted that the electronic element/module may be entirely or partially surrounded by the closely arranged conductive bumps  122  according to the balance between electromagnetic shielding effect and miniaturization requirement. 
         [0033]    According to the present disclosure, the electronic module with electromagnetic shielding function can be manufactured by a simplified method which can be integrated into a package process. The electromagnetic shielding structure can be disposed in much small areas of the electronic module. Therefore, it is advantageous to miniaturization of the electronic module by using the electromagnetic shielding structure of the present disclosure in the electronic module. The electronic module is manufactured in a simplified, flexible, easily controllable and cost-effective manner. Furthermore, high yield rate is achieved due to the easily controllable feature of the manufacturing method. 
         [0034]    While the disclosure has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.