Abstract:
A method and system for fabricating an integral electromagnetic radiation shield for an electronics package is disclosed. Various embodiments include exposing a portion of at least one ground contact feature in an electronic package by removing a portion of the electronic package above the at least one ground contact feature to form at least one trench above the at least one ground contact feature; depositing electromagnetic radiation shield material in the at least one trench to substantially fill the at least one trench with a trench deposit; and depositing additional electromagnetic radiation shield material over a substantial portion of the electronic package, wherein the electromagnetic radiation shield material in the trench and over the substantial portion of the electronic package form an integral electromagnetic radiation shield which is electrically connected to the at least one ground contact feature.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a divisional of U.S. patent application Ser. No. 11/315,903, filed on Dec. 22, 2005, which is incorporated herein by reference in its entirety. 
     
    
     FIELD 
       [0002]    The subject matter of the present invention relates to electronics packaging and more particularly to a method and system for fabricating an integral electromagnetic radiation shield in an electronics package. 
       BACKGROUND 
       [0003]    Conventional electronics used in certain applications emit high frequency electromagnetic radiation that can interfere with the performance of other devices. For example, conventional microelectronic radio frequency (RF) devices emit RF radiation. RF radiation may adversely affect the performance of other electronic components, such as certain molded array packages (MAPS) or other semiconductor packages, used in conjunction with the conventional microelectronic RF device. 
         [0004]    In order to protect other conventional electronic components from RF radiation, an electromagnetic radiation shield is provided between the conventional microelectronic RF device and other conventional electronic components. Typically this is performed by surrounding the other conventional electronic components with a physical shield. The physical shield is typically composed of an electrically conductive metallic media. For example, a conventional metal cover may be provided for each conventional electronic component desired to be shielded. In some conventional electronic components, the metal cover might include through holes that facilitate placement of mold compound that might be used as a protective layer for the underlying electronic device. 
         [0005]    Although conventional metal shields can reduce the interference due to the RF radiation, one of ordinary skill in the art will readily recognize that such conventional metal covers are costly to fabricate. Typically, such conventional metal shields are custom designed for individual conventional electronic components. In addition, custom assembly equipment is typically used for assembling the conventional metal cover and attaching the conventional metal cover to the component. The custom assembly and design are typically expensive. 
         [0006]    In addition, the conventional metal cover may also increase the size of the conventional electronic component being shielded. This increase in the size of the conventional electronic component may result in an increase in size of the final product employing the conventional electronic component. Typically, such an increase in size is undesirable. Consequently, use of conventional metal covers may be costly and undesirable for other reasons. 
       SUMMARY 
       [0007]    The subject matter of the present invention provides a method and system for fabricating a shield for an electronics package. The subject matter of the present invention may be applied to various types of organic and inorganic substrate based electronics packages. The typical package type is a Molded Array Package (MAP). The electronics package includes a substrate, at least one ground contact feature, and a protective layer. The electronics package is physically coupled to at least one additional electronics package through at least the substrate. The method and system comprise exposing a portion of the at least one ground contact feature, preferably during a singulation process. The exposing step forms at least one trench above the at least one ground contact feature. The method and system also comprise depositing a metal shielding material that substantially covers the top surfaces and side surfaces of the electronics package, filling the trenches, and is electrically connected to the at least one ground contact feature on each electronic package substrate site. 
         [0008]    According to the method and system disclosed herein, the present invention provides an integral RF shield that may be lower in cost. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a flow chart depicting a method for providing an electromagnetic radiation shield in an electronics package in accordance with an example embodiment of the present invention. 
           [0010]      FIGS. 2-7  depict side views of a semiconductor package including an electromagnetic radiation shield during fabrication in accordance with an example embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0011]    The subject matter of the present invention relates to electronics packages utilizing electromagnetic shielding. The following description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the preferred embodiments and the generic principles and features described herein will be readily apparent to those skilled in the art. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features described herein. 
         [0012]    The subject matter of the present invention provides a method and system for fabricating an electromagnetic radiation shield for an electronics package. The electronics package includes a substrate, at least one ground contact feature, and a protective layer. The electronics package is physically coupled to at least one additional electronics package through at least the substrate. The method and system comprise exposing a portion of the at least one ground contact feature by removing a portion of the electronics package above the ground contact feature. The exposing step forms at least one trench above the at least one ground contact feature. The method and system also comprise depositing an electromagnetic radiation shield that substantially covers the electronics package, fills the at least one trench, and is electrically connected to the at least one ground contact feature. The method and system also comprise separating the electronics package from the at least one additional electronics package such that a remaining portion of the electromagnetic radiation shield substantially enclosing a portion of the electronics package above the ground contact feature that remains. 
         [0013]    The subject matter of the present invention will be described in terms of particular components and particular electronics packages, such as MAPs. However, one of ordinary skill in the art will readily recognize that other and/or additional components and other and/or additional electronics packages could be used. For example, the subject matter of the present invention may be applied to various types of electronics packages that use a leadframe array or substrate array strip format such that each strip contains multiple repeat individual sites for package assembly. In addition, the present invention is described in the context of particular methods. One of ordinary skill in the art will, however, readily recognize that other methods having other and/or additional steps could be used. 
         [0014]      FIG. 1  is a flow chart depicting one embodiment of a method  100  for providing an electromagnetic radiation shield in accordance with the present invention in an electronics package.  FIGS. 2-7  depict a side view of one embodiment of an electronics package  210 , a MAP, including one embodiment of an electromagnetic radiation shield in accordance with the present invention during fabrication. Referring to  FIGS. 1-7 , the method  100  is described in the context of the MAP  210 . However, one of ordinary skill in the art will readily recognize that the method  100  can be used with other semiconductor packages. In addition, one of ordinary skill in the art will readily recognize that the electromagnetic radiation shield, described below, could be used with other semiconductor packages. 
         [0015]      FIG. 2  depicts the substrate strip  200  including the MAP  210  prior to fabrication of one embodiment of the electromagnetic radiation shield in accordance with the present invention. In forming the MAP  210 , multiple electronic dice and/or other components are attached and electrically connected to each sites on the leadframe array or substrate array first, mass over-molded and then singulated into individual electronic packages such as the MAP  210 . The substrate strip  200  shown thus includes a substrate  202 , ground contact features  204  and  206 , and a protective layer  208 . The MAP substrates  202  are typically fabricated with an organic substrate core material, such as polyamide, BT resin or FR-4, FR-5 material. 
         [0016]    The circuitry metal for these substrates  202 , such as for ground contact feature  204  and  206 , is typically copper. These substrates can have metal circuitry on both sides of the organic core, multiplayer metal (4, 6, 8 or more metal layers are also used). 
         [0017]    A solder mask layer (not shown), typically made with an epoxy base material, coats both top and bottom metal layers exposing the bond pad regions (not shown) and or component attach regions (not shown) on the top and solderball attach regions (not shown) at the bottom of the substrate strip  200 . The exposed metal is over-plated with typically nickel and gold metal to facilitate wire bonding and soldering. The ground contact features  204  and  206  may have a variety of shapes such as a pad, a line, or a frame. However, ground contact features  204  and  206  are depicted as ground planes. In addition, the ground planes  204  and  206  are preferably designed to be at the extreme external edge of the individual electronic package substrate site. During the MAP packaging assembly process, discrete components (not shown), if present, are first attached to the individual package substrate sites of the substrate strip  200  by soldering or epoxy. 
         [0018]    The dice (not shown) and/or components (not shown) are attached to individual sites and wirebonded or flip-chip soldered. The substrate strip is then overmolded using the protective layer  208 . The protective layer  208  is typically an epoxy mold compound. Consequently, the MAP  210  is physically coupled to additional MAPs  210 ′ and  210 ″ through at least the substrate  202 . In the embodiment shown, the MAP  210  is coupled to the MAPS  210 ′ and  210 ″ through the substrate  202 , the ground planes  204  and  206 , respectively, and the protective layer  208 . As discussed above, in the embodiment shown, in which the electronics package  210  being fabricated is a MAP, the protective layer  208  is an over-mold compound. Thus, in one embodiment, the protective layer  208  includes an epoxy mold that has been over-molded to the substrate  202 . The MAP  210  also generally includes other active and/or passive electronic components that have been attached, bonded, and electrically coupled with portions of the substrate  202 . However, for simplicity, such electronic components are not shown. 
         [0019]    Referring to  FIGS. 1 and 2 , a portion of the ground planes  204  and  206  are exposed by removing a portion of the electronics package above the ground planes  204  and  206 , respectively, via step  102 . Step  102  is typically is performed during the singulation step, which is used to separate the MAPs  210 ,  210 ′ and  210 ″. A saw or laser is preferably used to perform the portion of the singulation in step  102 . The saw or laser cuts through the total thickness of the protective layer  208  and stops at the substrate strip&#39;s “top” surface exposing the ground planes  204  and  206 . In the embodiment shown, step  102  is preferably performed by utilizing a wide saw blade to cut into the MAP  210 , stopping at the ground planes  204  and  206 . The wide saw blade is wider than a blade use to separate the packages. The typical range of widths for the saw blade used to partially cut the MAP (i.e. used in step  102 ) is 0.002″ to 0.010″ wider than the MAP singulation saw blade used in step  108 . However, depending on the ground contact feature size design, the saw blade width can vary. 
         [0020]      FIG. 3  depicts substrate the strip  200  including the MAP  210  during step  102 . Thus, the saw blade(s)  214  used in exposing the ground planes  204  and  206  are shown. Note that in one embodiment a single saw blade  214  is used multiple times to make the cuts.  FIG. 4  depicts the substrate strip  200  including the MAP  210  after step  102  has been completed. Thus, the ground planes  204  and  206  are exposed. In addition, the ground planes  204  and  206  have not been cut through by the saw blades  214 . Thus, trenches  216  and  218  above the ground planes  204  and  206 , respectively, have been formed. 
         [0021]    An electromagnetic radiation shield material is deposited, via step  104 . Step  104  preferably includes conformally depositing a metallic material over the surface of the devices  210 ,  210 ′ and  210 ″, particularly including the protective layer  208  and ground planes  204  and  206 . In one embodiment, the metallic material includes materials such as Ni and/or Fe. In another embodiment, the metallic material may be a metal-polymer composite material. Various methods could be used to provide the electromagnetic radiation shield. For example, in various embodiments, screen printing, spraying and curing, stencil printing, brushing, and/or vacuum depositing may be used to provide the electromagnetic shield. 
         [0022]      FIG. 5  depicts substrate the substrate strip  200  including the MAP  210  after step  104  has been performed. Thus, the electromagnetic shield  220  has been deposited. The electromagnetic shield  220  substantially covers the electronics package  210 . In addition, the electromagnetic shield  210  substantially fills the trenches  216  and  218 . The electromagnetic shield  210  is also electrically coupled with the ground planes  204  and  206 . The electromagnetic shield  220  thus substantially covers the top surfaces and side surfaces of the MAP  210 , filling all the saw/laser cut trenches  214  and  216 , and is electrically connected to the ground planes  204  and  206  on each electronic package substrate site. Stated differently, the substrate strip may be completely coated with metal. However, as can be seen in  FIG. 5 , the MAPs  210 ,  210 ′, and  210 ″ are still physically connected. In a preferred embodiment, after step  104  is performed, package solderballs (not shown), if used, may be attached to the bottom of the substrate strip. 
         [0023]    The MAP  210  is separated from the additional MAPs  210 ′ and  210 ″, via step  106 . Thus, the singulation process is completed in step  106 . Step  106  is performed such that a remaining portion of the electromagnetic radiation shield  220  still substantially encloses the portion of the MAP  210  above the one ground planes  204  and  206 . Stated differently, step  106  is performed such that the electromagnetic shield  210  is still capable of functioning as a shield. The cut performed in step  106  may be performed using a laser or a saw. The saw or laser is preferably configured to cut through the mid-point of the trenches  214  and  216 . In the embodiment shown, step  106  is performed using a saw blade that is thinner than the saw blade used in step  102 . In addition, the saw blade would cut through not only the shield  220 , but also the ground planes  204  and  206 , as well as the substrate  202 . Once the MAP  210  is separated from the additional MAPs  210 ′ and  210 ″, any further fabrication of the MAP  210  may be completed. 
         [0024]      FIG. 6  depicts the substrate strip  200  including the MAP  210  during step  106 . Thus, thinner saw blades  222  are shown. The saw blades  222  cut through the shield  220 , the ground planes  204 ′ and  206 ′, as well as the substrate  202 ′. Thus, the MAPs  210 ,  210 ′, and  210 ″ are singulated to individual packages. Note that although multiple saw blades  222  are, shown, in one embodiment a single saw blade  222  is used multiple times to make the cuts. Because thinner saw blades  222  are used and because the saw blades  222  are positioned such that the shield  220 ′ still substantially encloses the MAP  210  above the ground planes  204 ′ and  206 ′, the remaining portion of the electromagnetic shield  220 ′ is still capable of functioning as an electromagnetic radiation shield. Thus, for example, the shield  220 ′ may still be sufficiently effective at protecting the electronics (not explicitly shown) of the MAP  210  from RF radiation. 
         [0025]      FIG. 7  depicts the MAP  210  after step  106  is completed. Because the MAP  210  was separated in step  106 , the other MAPs  210 ′ and  210 ″ are not depicted. However, the MAPs  210 ′ and  210 ″ should also have shields (not shown) that are analogous to the shield  220 ′. As can be seen in  FIG. 7 , the shield  220 ′ is integrated into the MAP  210 . The shield  220 ′ still substantially encloses the MAP  210  above the ground planes  204  and  206 . The shield  220 ′ substantially surrounds the portion of the MAP  210  from the ground planes  204 ′ and  206 ′ and above. Thus, the protective layer  208  is substantially surrounded. Thus, the remaining portion of the electromagnetic shield  220 ′ is still capable of functioning as an electromagnetic radiation shield. Thus, for example, the shield  220 ′ may still be sufficiently effective at protecting the electronics (not explicitly shown) of the MAP  210  from RF radiation. In addition, the shield  220 ′ is formed directly on the MAP  210 . In a preferred embodiment, the shield  220 ′ if fabricated directly on the protective layer  208 ′. 
         [0026]    Thus, using the method  100 , the electronics package, here a MAP,  210  can be shielded using an integrated shield  220 ′. The method  100  may utilize conventional processes in preparing the MAP  210  for the shield  220 ′, in depositing the shield  220 , and in separating the MAP  210  from remaining MAPs  210 ′ and  210 ″. As a result, the shield  220 ′ is relatively simple to fabricate and incorporate into fabrication of the MAP  210 ,  210 ′, and  210 ″. Consequently, custom designing of a shield and custom fabrication of the shield using tools specifically for the shield and the particular electronics package can be avoided. Inclusion of the shield  220 ′ in the MAP  210 ′ may thus be more cost effective. In addition, the shield  220 ′ is preferably integrated into the MAP  210 ′ and directly on the protective layer  208 ′. Consequently, the shield  220 ′ may not significantly increase the size of the MAP  210 ′. Thus, the shield  220 ′ may also avoid undue increases in size of the MAP  210 ′ and/or any final product employing the MAP  210 ′. 
         [0027]    A method and system for more easily providing an electromagnetic radiation shield for an electronics package are described. The present invention has been described in accordance with the embodiments shown, and one of ordinary skill in the art will readily recognize that there could be variations to the embodiments, and any variations would be within the spirit and scope of the present invention. Accordingly, many modifications may be made by one of ordinary skill in the art without departing from the spirit and scope of the appended claims.