PATENT DOCUMENT

Publication Number: US-9793222-B1
Application Number: US-201615135071-A
Country: US
Kind Code: B1

Title: Substrate designed to provide EMI shielding

Abstract:
Packages and packaging techniques for providing EMI shielding are described. In an embodiment, a package includes an electrically conductive ground structure on a ground pad at a periphery of a package substrate. The electrically conductive ground structure is encapsulated in a molding compound, and a surface of the electrically conductive ground structure is exposed at a side surface of the molding compound. An electrically conductive shield layer is on top and side surfaces of the molding compound, and in physical contact with the surface of the exposed electrically conductive ground structure.

Claims:
What is claimed is: 
     
       1. A method comprising:
 attaching a die to a top surface of a wiring substrate; 
 attaching a plurality of wire bonds to a plurality of ground pads and a plurality of dummy pads at the top surface of the wiring substrate such that each wire bond is attached to a corresponding ground pad and a corresponding dummy pad; 
 encapsulating the die and the plurality of wire bonds within a molding compound; 
 cutting through the molding compound and a corresponding plurality of bond areas of the plurality of wire bonds to expose a corresponding plurality of surfaces of the bond areas at cut side surfaces of the molding compound; and 
 depositing an electrically conductive shield layer on a top surface and the cut side surfaces of the molding compound, and in physical contact with the plurality of surfaces of the exposed bond areas at the cut side surfaces of the molding compound. 
 
     
     
       2. The method of  claim 1 , further comprising dicing though the electrically conductive shield layer and the wiring substrate to singulate a package. 
     
     
       3. The method of  claim 2 , further comprising placing a plurality of solder balls on a bottom surface of the wiring substrate prior to dicing though the wiring substrate and the electrically conductive shield layer to singulate the package. 
     
     
       4. The method of  claim 1 , wherein cutting further comprises cutting through the wiring substrate to singulate a package. 
     
     
       5. The method of  claim 4 , further comprising placing the package on a temporary carrier, and depositing the electrically conductive shield layer on the top surface and the cut side surfaces of the molding compound, and in physical contact with the plurality of surfaces of the exposed bond areas at the cut side surfaces of the molding compound. 
     
     
       6. The method of  claim 1 , further comprising:
 attaching a first wire bond of the plurality of wire bonds to a first ground pad of the plurality of ground pads and a first dummy pad of the plurality of dummy pads, and attaching a second wire bond of the plurality of wire bonds to a second ground pad of the plurality of ground pads and the first dummy pad; 
 cutting through the molding compound and a first bond area of the first wire bond to expose a first surface of the first bond area at a first cut side surface of the molding compound; and 
 cutting through the molding compound and a second bond area of the second wire bond to expose a second surface of the second bond area at the first cut side surface of the molding compound. 
 
     
     
       7. The method of  claim 6 , further comprising dicing though the electrically conductive shield layer and the wiring substrate to singulate a package including the first surface of the first bond area and the second surface of the second bond area. 
     
     
       8. The method of  claim 1 , further comprising:
 attaching a first wire bond of the plurality of wire bonds to a first ground pad of the plurality of ground pads and a first dummy pad of the plurality of dummy pads, and attaching a second wire bond of the plurality of wire bonds to a second ground pad of the plurality of ground pads and the first dummy pad; 
 cutting through the molding compound and a first bond area of the first wire bond to expose a first surface of the first bond area at a first cut side surface of the molding compound; and 
 cutting through the molding compound and a second bond area of the second wire bond to expose a second surface of the second bond area at a second cut side surface of the molding compound. 
 
     
     
       9. The method of  claim 8 , further comprising dicing though the electrically conductive shield layer and the wiring substrate to singulate a first package including the first surface of the first bond area and a second package including the second surface of the second bond area. 
     
     
       10. The package of  claim 5 , further comprising:
 attaching a first wire bond of the plurality of wire bonds to a first ground pad of the plurality of ground pads and a first dummy pad of the plurality of dummy pads, and attaching a second wire bond of the plurality of wire bonds to a second ground pad of the plurality of ground pads and the first dummy pad; 
 cutting through the molding compound and a first bond area of the first wire bond to expose a first surface of the first bond area at a first cut side surface of the molding compound; and 
 cutting through the molding compound and a second bond area of the second wire bond to expose a second surface of the second bond area at the first cut side surface of the molding compound. 
 
     
     
       11. The package of  claim 10 , further comprising dicing though the electrically conductive shield layer and the wiring substrate to singulate the package including the first surface of the first bond area and the second surface of the second bond area. 
     
     
       12. The package of  claim 5 , further comprising:
 attaching a first wire bond of the plurality of wire bonds to a first ground pad of the plurality of ground pads and a first dummy pad of the plurality of dummy pads, and attaching a second wire bond of the plurality of wire bonds to a second ground pad of the plurality of ground pads and the first dummy pad; 
 cutting through the molding compound and a first bond area of the first wire bond to expose a first surface of the first bond area at a first cut side surface of the molding compound; and 
 cutting through the molding compound and a second bond area of the second wire bond to expose a second surface of the second bond area at a second cut side surface of the molding compound. 
 
     
     
       13. The package of  claim 12 , further comprising dicing though the electrically conductive shield layer and the wiring substrate to singulate the package including the first surface of the first bond area, wherein the package does not include the second surface of the second bond area. 
     
     
       14. A package manufactured according to the method, comprising:
 attaching a die to a wiring substrate; 
 bonding a plurality of wires bonds to a plurality of ground pads at a top surface of the wiring substrate and a plurality of dummy pads at the top surface of the wiring substrate, such that each wire bond is bonded to a corresponding ground pad and a corresponding dummy pad; 
 encapsulating the die and the plurality of wire bonds with a molding compound; 
 cutting through the molding compound and the plurality of wire bonds to expose a corresponding plurality of surfaces of the plurality of electrically conductive ground structures at cut side surfaces of the molding compound; and 
 depositing an electrically conductive shield layer on a top surface and the cut side surfaces of the molding compound, and in physical contact with the plurality of surfaces of the exposed plurality of wire bonds at the cut side surfaces of the molding compound. 
 
     
     
       15. The package of  claim 14 , wherein cutting through the plurality of wire bonds comprises cutting through bond areas of the plurality of wire bonds. 
     
     
       16. The package of  claim 15 , wherein the bond areas are selected from the group consisting of ball bond areas and wedge bond areas. 
     
     
       17. The package of  claim 14 , wherein cutting through the plurality of wire bonds comprises cutting through wires of the plurality of wire bonds.

Description:
BACKGROUND 
     Field 
     Embodiments described herein relate to electronic packaging. More particularly, embodiments relate to packaging techniques for providing electro-magnetic interference (EMI) shielding. 
     Background Information 
     Plastic ball grid array (BGA) substrates are commonly used for memory, controller, and chipset applications amongst others. BGA substrates are commonly sold in the strip form, and including one or more build-up layers, and optionally a core. A common BGA package assembly process may include using an off-the shelf BGA substrate strip, mounting a plurality of die and components onto the BGA substrate strip, and encapsulating the plurality of die and components in a molding compound on the BGA strip. A plurality of packages may then be singulated from the molded BGA substrate strip. 
     In some applications, electro-magnetic interference (EMI) shielding is formed on the singulated packages in order to either mitigate EMI radiation from the package or to prevent EMI radiation from external sources from interfering with operation of the package. In one implementation an EMI shielding layer is formed over the molding compound and side surfaces of the singulated BGA substrate so that the EMI shielding layer is in direct contact with an exposed ground wire within the BGA substrate. If the electrical connection between the EMI shielding layer and the exposed ground wire is defective, the EMI shielding effect may not be achieved. 
     SUMMARY 
     Packages and packaging techniques for providing EMI shielding are described. In an embodiment, a package includes a package substrate including a top surface and a bottom surface. A die is bonded to the package substrate top surface, and a ground pad is located at a periphery of the package substrate top surface. In accordance with embodiments, an electrically conductive ground structure is on (e.g. bonded to) the ground pad. A molding compound encapsulates the die and the electrically conductive ground structure on the package substrate top surface. The molding compound includes a top surface and side surfaces, and a surface of the electrically conductive ground structure is exposed at a side surface of the molding compound. An electrically conductive shield layer (e.g. EMI shielding layer) is on the top and side surfaces of the molding compound, and in physical contact with the surface of the exposed electrically conductive ground structure. 
     The package substrate may be a variety of substrates, such as a printed circuit board (PCB). In an embodiment, the package substrate includes one or more metal routing layers, and the electrically conductive ground structure is thicker than every metal routing layer in the package substrate. In some embodiments, the electrically conductive shield layer is not formed on side surfaces of the package substrate. The electrically conductive ground structure may also or alternatively be wider than the metal routing layer(s). 
     In some embodiments, the ground pad may be a ground pad ring at the periphery of the package substrate top surface. In some embodiments, the package includes a plurality of ground pads at the periphery of the package substrate top surface, and a plurality of electrically conductive ground structures on the plurality of ground pads. In such an arrangement, a corresponding plurality of surfaces of the plurality of electrically conductive ground structures are exposed at side surfaces of the molding compound, and the electrically conductive shield layer is in physical contact with the plurality of surfaces of the plurality of exposed electrically conductive ground structures. A variety of electrically conductive ground structures may be utilized, such as, a wire bond, pillar, solder ball, cored ball, and chip with electrical routing. In some embodiments, the plurality of electrically conductive ground structures are wire bonds. 
     The package may additionally include a plurality of bond pads adjacent a periphery of the package substrate bottom surface. In an embodiment, the plurality of ground pads may be located nearer the periphery of the package substrate top surface, than the plurality of bond pads are to the periphery of the package substrate bottom surface. A plurality of solder bumps may be attached to the plurality of bond pads. The plurality of ground pads may be electrically connected to one or more of the plurality of solder bumps, or magnetically connected to one or more of the plurality of solder bumps. 
     In an embodiment, a method of forming a package includes attaching a die to the top surface of the wiring substrate, attaching a plurality of electrically conductive ground structures to a plurality of ground pads at the top surface of the wiring substrate, encapsulating the die and the plurality of electrically conductive ground structures within a molding compound, cutting through the molding compound and the plurality of electrically conductive ground structures to expose a corresponding plurality of surfaces of the plurality of electrically conductive ground structures at cut side surfaces of the molding compound, and depositing an electrically conductive shield layer on a top surface and the cut side surfaces of the molding compound, and in physical contact with the plurality of surfaces of the exposed electrically conductive ground structures at the cut side surfaces of the molding compound. 
     The packaging methods may be compatible with both half cut and full cut singulation. In a half cut method, the initial cut through the molding compound and the plurality of electrically conductive ground structures does not extend completely through the supporting wiring substrate. In such an embodiment, a sequential dicing operation is performed through the conductive shield layer and the wiring substrate to singulate a package. Additionally, a plurality of solder balls may be placed on a bottom of the wiring substrate prior to dicing though the wiring substrate and the electrically conductive shield layer to singulate the package. In a full cut method, the initial cut through the molding compound and the plurality of electrically conductive ground structures extends completely through the supporting wiring substrate to singulate a package. In such an embodiment, the singulated package may be placed on a temporary carrier, followed by depositing the electrically conductive shield layer on the top surface and the cut side surfaces of the molding compound, and in physical contact with the plurality of surfaces of the exposed electrically conductive ground structures at the cut side surfaces of the molding compound. 
     In an embodiment, a package is manufactured according to a method including attaching a die to a wiring substrate, bonding a plurality of wires bonds to a plurality of ground pads at a top surface of the wiring substrate and a plurality of dummy pads at the top surface of the wiring substrate, such that each wire bond is bonded to a corresponding ground pad and a corresponding dummy pad, encapsulating the die and the plurality of wire bonds with a molding compound, cutting through the molding compound and the plurality of wire bonds to expose a corresponding plurality of surfaces of the plurality of electrically conductive ground structures at cut side surfaces of the molding compound, and depositing an electrically conductive shield layer on a top surface and the cut side surfaces of the molding compound, and in physical contact with the plurality of surfaces of the exposed plurality of wire bonds at the cut side surfaces of the molding compound. 
     In an embodiment, cutting through the plurality of wire bonds may include cutting through bond areas of the plurality of wire bonds, such as ball bond areas or wedge bond areas. In an embodiment, cutting through the plurality of wire bonds comprises cutting through wires of the plurality of wire bonds. In an embodiment, cutting through the plurality of wire bonds comprises cutting through bond areas and wires of the plurality of wire bonds. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  a schematic cross-sectional side view illustration of a package in accordance with an embodiment. 
         FIG. 2  is a schematic bottom view illustration of a package substrate bottom surface in accordance with an embodiment. 
         FIGS. 3-4  are schematic top view illustrations of a plurality of ground pads at the periphery of a package substrate top surface in accordance with an embodiment. 
         FIG. 5  is a schematic top view illustration of a ground pad ring at the periphery of a package substrate top surface in accordance with an embodiment. 
         FIG. 6  is a schematic cross-sectional side view illustration of a wire bond in accordance with an embodiment. 
         FIG. 7  is a schematic cross-sectional side view illustration of a pillar in accordance with an embodiment. 
         FIG. 8  is a schematic cross-sectional side view illustration of a solder ball in accordance with an embodiment. 
         FIG. 9  is a schematic cross-sectional side view illustration of a cored ball in accordance with an embodiment. 
         FIG. 10  is a schematic cross-sectional side view illustration of a silicon chip with electrical routing in accordance with an embodiment. 
         FIGS. 11-13  are schematic cross-sectional side view illustrations of packages including various electrically conductive ground structures in accordance with embodiments. 
         FIG. 14  is a flow chart illustrating a packaging method including depositing an electrically conductive shield layer on exposed electrically conductive ground structures in accordance with an embodiment. 
         FIG. 15  is a flow chart illustrating a packaging method including a half cut singulation process in accordance with an embodiment. 
         FIG. 16  is a schematic top view illustration of a wiring substrate including an arrangement of ground pads in accordance with an embodiment. 
         FIG. 17  is a schematic top view illustration of a wiring substrate including electrically conductive ground structures bonded to an arrangement of ground pads in accordance with an embodiment. 
         FIG. 18  is a schematic top view illustration of a wiring substrate including wire bonds bonded to an arrangement of ground pads in accordance with an embodiment. 
         FIG. 19  is a schematic top view illustration of a wiring substrate after encapsulation with a molding compound in accordance with an embodiment. 
         FIGS. 20-24  are schematic cross-sectional side view illustrations of a packaging method including a half cut singulation process in accordance with an embodiment. 
         FIGS. 25-26  are schematic cross-sectional side view illustrations of a package in accordance with an embodiment. 
         FIG. 27  is a flow chart illustrating a packaging method including a full cut singulation process in accordance with an embodiment. 
         FIGS. 28-30  are schematic cross-sectional side view illustrations of a packaging method including a full cut singulation process in accordance with an embodiment. 
         FIG. 31  is a schematic cross-sectional side view illustration of a package in accordance with an embodiment. 
         FIG. 32  is a flow chart illustrating a packaging method including wire bonding to dummy pads in accordance with an embodiment. 
         FIG. 33  is a schematic top view illustration of a wiring substrate including an arrangement of ground pads and dummy pads in accordance with an embodiment. 
         FIG. 34  is a schematic top view illustration of a wiring substrate including wire bonds bonded to an arrangement of ground pads and dummy pads in accordance with an embodiment. 
         FIG. 35  is a schematic top view illustration of a wiring substrate after encapsulation with a molding compound in accordance with an embodiment. 
         FIGS. 36-40  are schematic cross-sectional side view illustrations of a packaging method including wire bonding to dummy pads in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments describe packages and package substrates to provide EMI shielding. In an embodiment, a package includes a package substrate with a top surface and a bottom surface. A die is bonded to the package substrate top surface and a ground pad is located at a periphery of the package substrate top surface. An electrically conductive ground structure is on the ground pad, and a molding compound encapsulates the die and the electrically conductive ground structure on the package substrate top surface. The molding compound includes top and side surfaces, and the electrically conductive ground structure is exposed at a side surface of the molding compound. An electrically conductive shield layer (e.g. EMI shield layer) is formed on the top and side surfaces of the molding compound, and in physical contact with the exposed electrically conductive ground structure. 
     In one aspect, it has been observed that it may be difficult to ensure a reliable electrical connection is made when forming a conventional EMI shield on a singulated package. More specifically, it may be difficult to ensure a reliable connection is made with an exposed ground wire layer located within a package substrate. This may be particularly apparent as package substrate thickness is reduced. 
     In accordance with embodiments, a variety of electrically conductive ground structures can be bonded to the one or more ground pads at the periphery of the package substrate top surface. For example, the electrically conductive ground structure can be a wire bond, pillar, ball (e.g. solder), cored ball, silicon chip with electrical routing, and combinations thereof, such as a wire bond on a silicon chip. In accordance with embodiments, the electrically conductive ground structures may be thicker and/or wider than the one or more wiring layers located within the package substrate. The ground structure can be thicker and/or wider after cutting through the ground structure, for example in a half cut or full cut process. As a result, the electrically conductive ground structures may provide more surface area for making an electrical connection with an EMI shield layer. Additionally, the electrically conductive ground structures are located over the package substrate, where an EMI shield layer can be more reliably formed. 
     In various embodiments, description is made with reference to figures. However, certain embodiments may be practiced without one or more of these specific details, or in combination with other known methods and configurations. In the following description, numerous specific details are set forth, such as specific configurations, dimensions and processes, etc., in order to provide a thorough understanding of the embodiments. In other instances, well-known semiconductor processes and manufacturing techniques have not been described in particular detail in order to not unnecessarily obscure the embodiments. Reference throughout this specification to “one embodiment” means that a particular feature, structure, configuration, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrase “in one embodiment” in various places throughout this specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, configurations, or characteristics may be combined in any suitable manner in one or more embodiments. 
     The terms “above”, “over”, “to”, “spanning” and “on” as used herein may refer to a relative position of one layer with respect to other layers. One layer “above”, “over”, “spanning” or “on” another layer or bonded “to” or in “contact” with another layer may be directly in contact with the other layer or may have one or more intervening layers. 
     Referring now to  FIG. 1  a schematic cross-sectional side view illustration is provided of a package  100  including a package substrate  102  with a top surface  104  and a bottom surface  106 . The top surface  104  may include a plurality of contact pads  109  and one or more ground pads  108  located around a periphery of the package substrate  102  top surface  104 . As shown, one or more die  120  and/or component(s)  122  may be bonded to the top surface of package substrate top surface  104 , for example to contact pads  109  with conductive bumps  124 . One or more electrically conductive ground structures  130  is on the one or more ground pads  108 , and a molding compound  140  encapsulates the die  120 , component(s)  111 , and the electrically conductive ground structure(s)  130  on the package substrate top surface  104 . The molding compound  140  includes a top surface  142  and side surfaces  144 , and the electrically conductive ground structure  130  is exposed at a side surface  144  of the molding compound  140 . An electrically conductive shield layer  150  (e.g. EMI shield layer) is formed on the top surface  142  and side surfaces  144  of the molding compound  140 , and in physical contact with the exposed electrically conductive ground structure  130 . 
     Package substrate  102  may be a variety of substrates including electrical routing, such as a printed circuit board (PCB). In an embodiment, the package substrate  102  is a wiring board that includes one or more metal routing layers  114  and dielectric layers to provide insulation between the metal routing layers  114 . Vias  116  may optionally extend through the one or more dielectric layers to connect metal routing layers  114 . In an embodiment, the dielectric layers are laminate resin layers, such as epoxy or bismaleimide-triazine resin, and may include a filler such as glass fibers. Metal routing layers  114  may be plated layers, or foil layers for example. The package substrate  102  may additionally include a core layer, for example, to support a specific coefficient of thermal expansion or provide structural support. The core may be formed of a variety of materials including, but not limited to, semiconductor, ceramic, polymer, glass fiber and resin, and metal. 
     In an embodiment, a plurality of electrically conductive ground structures  130  are on (e.g. bonded to) the plurality of ground pads  108  at the periphery of the package substrate  102  top surface  104 . In the particular embodiment illustrated, the electrically conductive ground structures  130  are wire bonds (as also described with regard to  FIG. 6 ) that include a bond area  132  and optionally a wire  134  extending from the bond area  132 . Wire bonding is a solid phase welding process in which a wire and pad surface are brought into intimate contact, in which interdiffusion of atoms typically takes place. During the wire bonding process, a wire  134  is brought into contact with the ground pad  108 , with the combination of heat, pressure, and/or ultrasonic energy leading to material deformation of the wire. The bond area  132  may be formed using techniques such as ball bonding (forming a ball bond area) or wedge bonding (forming a wedge bond area). Once the bond area  132  is made, the wire  134  may be broken off, or moved and attached to another pad at the opposite end of the wire  134 . 
     Still referring to  FIG. 1 , an electrically conductive ground structure  130  wire bond, including a ball bonding bond area  132  and wire  134  are illustrated. As shown, the electrically conductive ground structure  130  is exposed at side surfaces  144  of the molding compound  140 . In an embodiment, a surface  133  of the bond area  132  is exposed at the side surfaces  144 . In an embodiment, a surface  135  of the wire  134  is exposed at the side surfaces  144 . For example, a cross-section of a width or diameter of the wire  134  is exposed. In an embodiment, both surfaces  133 ,  135  of the bond area  132  and the wire  134  are exposed at the side surfaces  144 . In each of the embodiments, an electrically conductive shield layer  150  (e.g. EMI shield layer) is formed on the top surface  142  and side surfaces  144  of the molding compound  140 , and in physical contact with the exposed surfaces (e.g.  133 ,  135 ) of the electrically conductive ground structure  130 . In some embodiments, the electrically conductive shield layer  150  is not formed on side surfaces  103  of the package substrate  102 , though the electrically conductive shield layer  150  may be formed on side surfaces  103  of the package substrate  102 . The electrically conductive shield layer  150  may optionally be formed on side surfaces of the one or more ground pads  108  arranged around a periphery of the top surface  104  of the package substrate  102 . 
     The package substrate  102  may include one or more bond pads  110  on a bottom surface  106  of the package substrate  102 . Conductive bumps  160  (e.g. solder balls) may be attached to the bond pads  110 . In an embodiment, one or more of the ground pads  108  are electrically connected to one or more of the bond pads  110 , and conductive bumps  160 . For example, the electrical connection may be through one or more metal routing layers  114  and vias  116 . In one embodiment, the one or more ground pads  108  are magnetically connected to one or more of the bond pads  110 , for example, where the electrically conductive ground structure  130  is magnetic (e.g. magnetic wire, ball, etc.) 
     In an embodiment, the electrically conductive ground structure  130  is thicker than every metal routing layer  114  in the package substrate  102 . In an embodiment, the exposed surfaces (e.g.  133  and/or  135 ) of the electrically conductive ground structure  130  is thicker than every metal routing layer  114  in the package substrate  102 . The electrically conductive ground structure  130  may also, or alternatively, be wider than the metal routing  114  (for example at the cut surfaces in contact with the electrically conductive shield layer  150 ). In one aspect, the increased area and raised elevation above the package substrate  102  may facilitate electrical connection with the electrically conductive shield layer  150 . In some embodiments the one or more ground pads  108  are exposed at the side surfaces  103  of the package substrate  102 , though this is not necessary. 
     Referring now to  FIG. 2 , a schematic bottom view illustration is provided of a package substrate  102  bottom surface  106  in accordance with an embodiment. As shown, an arrangement of bond pads  110  are located on the bottom surface  106 , and may be electrically connected with the die  120  and/or component(s)  122  within the package, as well as the ground pad(s)  108  on the top surface  104  of the package substrate  102 . In an embodiment, a periphery of the bond pads  110  may be electrically connected to each other with interconnects  112 . 
     An exemplary illustration of a plurality of ground pads  108  located around a periphery of the top surface  104  of the package substrate  102  is illustrated in  FIG. 3 . In the particular embodiment illustrated in  FIG. 3 , the ground pads  108  may be exposed at the side surfaces  103  of the package substrate  102 . However, this is not required. In the embodiment illustrated in  FIG. 4  the ground pads  108  may not be exposed at side surfaces  103  of the package substrate  102 . For example, the ground pads  108  need not be exposed as long as a portion of the electrically conductive ground structure  130  is exposed at the side surfaces  144  of the molding compound  140  and in electrical connection with the electrically conductive shield layer  150 . Furthermore, it is not necessary to include a plurality of separate ground pads  108 , and a ground pad  108  ring may alternatively used in accordance with embodiments, as illustrated in  FIG. 5 . In an embodiment, the plurality of ground pads  108  (or ground ring) are located nearer the periphery of the package substrate top surface  104 , than the plurality of bond pads  110  are to the periphery of the package substrate bottom surface  106 . 
     While embodiments thus far have been described and illustrated including a wire bond as the exemplary electrically conductive ground structure  130 , embodiments are not so limited, and a variety of electrically conductive ground structures may be used in the packages  100  and fabrication methods described. 
       FIG. 6  is a schematic cross-sectional side view illustration of a wire bond  630  electrically conductive ground structure  130  in accordance with an embodiment. As previously described with regard to  FIG. 1 , the wire bond  630  may include a bond area  132  and wire  134 . 
       FIG. 7  is a schematic cross-sectional side view illustration of a pillar  730  electrically conductive ground structure  130  in accordance with an embodiment. For example, pillar  730  may be a metal (e.g. copper) pillar or ring that is bonded to or plated on the package substrate  102 . 
       FIG. 8  is a schematic cross-sectional side view illustration of a solder ball  830  electrically conductive ground structure  130  in accordance with an embodiment. 
       FIG. 9  is a schematic cross-sectional side view illustration of a cored ball  930  electrically conductive ground structure  130  in accordance with an embodiment. For example, a cored ball  930  may include an inner metal core  932  (e.g. copper) and shell  934  (e.g. solder). 
       FIG. 10  is a schematic cross-sectional side view illustration of a chip  1030  electrically conductive ground structure  130  with electrical routing in accordance with an embodiment. As shown, the chip  1030  may include one or more wiring layers  1034  and vias  1036 , for example, formed of copper. The chip  1030  may include support layers  1032  formed of silicon, or other suitable materials to support the one or more wiring layers  1034  and vias  1036  and provide mechanical integrity, for example during a cutting or sawing process. 
     Referring now to  FIGS. 11-13  schematic cross-sectional side view illustrations are provided of packages  100  including various electrically conductive ground structures in accordance with embodiments. As illustrated in  FIG. 11 , a solder ball  830  may include a surface  833  that is exposed at the side surfaces  144  of the molding compound  140 , and in contact with the electrically conductive shield layer  150 . Also illustrated in  FIG. 11 , a cored ball  930  may include a surface  933  of the core, and surface  935  of the shell  934  that are exposed at the side surfaces  144  of the molding compound  140 , and in contact with the electrically conductive shield layer  150 . 
     As illustrated in  FIG. 12 , a pillar  730  may include a surface  733  that is exposed at the side surfaces  144  of the molding compound  140 , and in contact with the electrically conductive shield layer  150 . Also illustrated in  FIG. 12 , a chip  1030  may include a surface  1035  of a wiring layer  1034 , and optionally a surface  1033  of a support layer(s)  1032  that are exposed at the side surfaces  144  of the molding compound  140 , and in contact with the electrically conductive shield layer  150 . 
     As illustrated in  FIG. 13 , a chip  1030  may include a surface  1037  of a via  1036  exposed at the side surfaces  144  of the molding compound  140 , and in contact with the electrically conductive shield layer  150 . Also illustrated in  FIG. 13  is a hybrid approach including a wire bond  630  on top of a chip  1030 . A variety of conductive surfaces may be exposed at side surfaces of the molding compound  140  and in contact with the electrically conductive shield layer  150 , including surfaces  133 ,  135 , and/or  1035 . 
     The packaging processes in accordance with embodiments may be compatible with a variety of electrically conductive ground structures  130  and techniques for applying the electrically conductive shield layer  150 . Additionally, the packaging processes in accordance with embodiments may be compatible with BGA processing techniques, in which the packages  100  are fabricated on and singulated on a wiring substrate  200 , which corresponds to the package substrate  102  after singulation. For example, the wiring substrate  200  may be in the form of a panel substrate or strip substrate compatible with BGA processing techniques. 
       FIG. 14  is a flow chart illustrating a packaging method including depositing an electrically conductive shield layer on exposed electrically conductive ground structures in accordance with an embodiment. In interest of clarity, the following description of  FIG. 14  is made with regard to reference features found in other figures described herein. At operation  1420  a plurality of die  120  and/or components  122  are attached to a top surface of a wiring substrate  200  so that at least one die  120  and/or component  122  is located within a package area  101 . At operation  1420  a plurality of electrically conductive ground structures  130  are attached to a plurality of ground pads  108  at the top surface  104  of the wiring substrate  200 . A variety of electrically conductive ground structures  130  may be used, including those described and illustrated in  FIGS. 6-10 , as well as combinations thereof, such as described with regard to  FIG. 13 . In an embodiment, the order of operations  1410 ,  1420  may be reversed. The plurality of die  120  and/or components  122 , and the plurality of electrically conductive ground structures  130  are then encapsulated within a molding compound  140  at operation  1430 . Following encapsulation, at operation  1440  the molding compound  140  and plurality of electrically conductive ground structures  130  are cut, for example using a blade or saw, to expose the plurality of electrically conductive ground structures  130  at the cut side surfaces  144  of the molding compound  140 . At operation  1450  an electrically conductive shield layer  150  is then deposited on the top surface  142  and the cut side surfaces  144  of the molding compound  140 , and also in physical contact with exposed surfaces of the exposed electrically conductive ground structures  130  at the cut side surfaces  144 . 
     The packaging methods in accordance with embodiments may be compatible with both half cut and full cut singulation processes. A packaging method illustrating a half cut singulation process is described and illustrated in  FIGS. 15-26 . In a half cut singulation process the electrically conductive shield layer  150  may be formed at the strip or panel level, potentially increasing throughput. A packaging method illustrating a full cut singulation process is described and illustrated in  FIGS. 27-31 . In one aspect, the packaging methods described in accordance with embodiments may be applied to a variety of different package substrates. For example, the packaging methods may be integrated at the strip level or panel level BGA packaging process. Furthermore, the packaging methods may be integrated with a variety of different substrates, for example, with minimum thicknesses and/or reduced wiring/routing layers. Thus, an electrically conductive shield layer  150  may be formed irrespective of the package substrate (or wiring substrate). 
       FIG. 15  is a flow chart illustrating a packaging method including a half cut singulation process in accordance with an embodiment. In interest of clarity, the following description of  FIG. 15  is made with regard to reference features found in other figures described herein. At operation  1510  a plurality of die  120  and/or components  122 , and a plurality of electrically conductive ground structures  130  are encapsulated within a molding compound  140  on a top surface of a wiring substrate  200 . At operation  1520  the molding compound  140  and plurality of electrically conductive ground structures  130  are cut, for example using a blade or saw, to expose the plurality of electrically conductive ground structures  130  at the cut side surfaces  144  of the molding compound  140 . In such an embodiment, the cut does not extend completely through the wiring substrate  202 , and may not extend into the wiring substrate  202 . At operation  1530  an electrically conductive shield layer  150  is then deposited on the top surface  142  and the cut side surfaces  144  of the molding compound  140 , and also in physical contact with exposed surfaces of the exposed electrically conductive ground structures  130  at the cut side surfaces  144 . At operation  1540 , the electrically conductive shield layer  150  and the wiring substrate  200  are diced through (e.g. half cut using a blade or saw) to singulate one or more packages  100  from the wiring substrate  200 . 
       FIG. 16  is a schematic top view illustration of a wiring substrate  200  (e.g. strip substrate, panel substrate) including an arrangement of ground pads  108  in accordance with an embodiment. As shown, a plurality of package areas  101 , or outlines, are provided to indicate where the cutting (e.g. sawing) streets will be. One or more die  120  and/or components  122  may be mounted onto the top surface  204  (not labeled in  FIG. 16 ) of the wiring substrate  200  within one or more package areas  101 . One or more ground pads  108  may also be located on the wiring substrate  200  top surface adjacent to a periphery of the package areas  101 . In the embodiment illustrated, the ground pads  108  overlap the package areas  101  (outlines). In other embodiments, the ground pads  108  may be located within the package areas  101 . In an embodiment, one or more ground pads  108  may be shared by adjacent package areas  101 . 
     Referring to  FIG. 17 , a corresponding plurality of electrically conductive ground structures  130  may be bonded to the arrangement of ground pads  108 . For example, the electrically conductive ground structures  130  may be any of those described and illustrated in  FIGS. 6-10 , as well as combinations thereof, such as described with regard to  FIG. 13 . In accordance with embodiments, the one or more electrically conductive ground structures  130  overlap the package areas  101 . 
     In one embodiment, the electrically conductive ground structures are wire bonds. During the wire bonding process, a wire  134  is brought into contact with the ground pad  108 , with the combination of heat, pressure, and/or ultrasonic energy leading to material deformation of the wire. The bond area  132  may be formed using techniques such as ball bonding or wedge bonding. Once the bond area  132  is made, the wire  134  may be broken off or moved and attached to another pad at the opposite end of the wire  134 . 
     Referring to  FIG. 18  an embodiment is illustrated including a plurality of wire bonds  630  bonded to the plurality of ground pads  108 . In the embodiment illustrated, the wires  134  of the wire bonds  630  may span between two ground pads  108  for the same package area  101 . In such an embodiment, the wires  134  of the wire bonds  630  may remain in the completed package  100 . The wires  134  of the wire bonds  630  may also span between two ground pads  108  of different package areas  101 . In such an embodiment, the wires  134  may be cut when cutting through the molding compound and electrically conductive ground structure. 
     The plurality of die  120  and/or components  122 , and the plurality of electrically conductive ground structures  130  (e.g. of  FIG. 16  or  FIG. 17 ) are then encapsulated within a molding compound  140 , as illustrated in  FIG. 19 . A schematic side view illustration of the encapsulated structure is illustrated in  FIG. 20 . The particular embodiment illustrated shows wire bonds  630  including bond areas  132 , in which the wires  134  have been broken off. It is to be appreciated that this is an exemplary illustration, and embodiments are not so limited. Any of the electrically conductive ground structures  130  previously described can be utilized. 
     Referring now to  FIGS. 21-22 , sawing streets are illustrated prior to half cutting, and trenches  146  are illustrated after half cutting through the molding compound  140  and the plurality of electrically conductive ground structures (e.g. wire bonds  630 ) to expose cut side surfaces  144  of the molding compound and an exposed surface  133  (e.g. of the bond area  132 ) of the wire bonds  630 . In accordance with embodiments, the half cut trenches  146  may extend slightly into the wiring substrate  200 , stop on the top surface  204  of the wiring substrate  200 , or not reach the wiring substrate  200  so long as the trenches extend at least partially through the electrically conductive ground structures (e.g. wire bonds  630 ). In an embodiment, a width of the trenches  146  corresponds to a saw blade width. 
     Referring now to  FIG. 23 , an electrically conductive shield layer  150  is then deposited on the top surface  142  and the cut side surfaces  144  of the molding compound  140 , and also in physical contact with exposed surfaces  133  of the exposed electrically conductive ground structures (e.g. wire bonds  630 ) at the cut side surfaces  144 . In accordance with embodiments, the electrically conductive shield layer  150  may be formed by spraying or sputtering to achieve a low cost and high throughput. Additional methods may also be used, including plating. Electrically conductive shield layer  150  may be formed of a variety of materials including metals (e.g. copper, etc.). 
     Conductive bumps  160  (e.g. solder balls) may optionally be attached to the bond pads  110  prior to or after formation of the electrically conductive shield layer  150 . A second half cut may then be performed through the electrically conductive shield layer  150  and the wiring substrate to singulate one or more packages  100 . Exemplary sawing streets are illustrated in  FIG. 24 . After singulation, the packages  100  may be in condition for bonding to a circuit board or mother board. 
       FIG. 25  is a schematic cross-sectional side view illustration of package  100  fabricated using a half cut singulation process in accordance with an embodiments. The structure illustrated in  FIG. 25  is substantially similar to that illustrated in  FIG. 1 , with one difference being the exemplary structure of the electrically conductive ground structures is a wire bond  630 , without an exposed surface  135  of the cut wire  134 . In accordance with embodiments, the electrically conductive ground structures of  FIG. 25  may be any of those previously described and illustrated with regard to  FIGS. 6-13 . 
       FIG. 26  is a schematic side view illustration of a package  100  including wire bonds  630  with wires  634  and bond areas  132  attached at both ends inside the package  100 . Thus, the wire bonds  630 , including the wires  134 , may be embedded inside the molding compound  140 . The wires  134  may additionally provide electrical connection between ground pads  108 . The structure illustrated in  FIG. 26  may be fabricated from a wiring substrate  200  such as that previously described and illustrated in  FIG. 18 , for example. 
     While embodiments thus far have been described and illustrated with regard to a half cut singulation process, embodiments are not so limited and the packages  100  may also be fabricated using a full cut singulation process.  FIG. 27  is a flow chart illustrating a packaging method including a full cut singulation process in accordance with an embodiment. In interest of clarity, the following description of  FIG. 27  is made with regard to reference features found in other figures described herein. At operation  2710  a plurality of die  120  and/or components  122 , and a plurality of electrically conductive ground structures  130  are encapsulated within a molding compound  140  on a top surface of a wiring substrate  200 . At operation  2720  a full cut is made through the molding compound  140 , the plurality of electrically conductive ground structures  130 , and the wiring substrate  200 , for example using a blade or saw, to singulate one or more packages  100  and expose the plurality of electrically conductive ground structures  130  at the cut side surfaces  144  of the molding compound  140 . At operation  2730  the one or more packages  100  are placed on a temporary carrier  300  such as a tape or adhesive layer. At operation  2740  an electrically conductive shield layer  150  is then deposited on the top surface  142  and the cut side surfaces  144  of the molding compound  140 , and also in physical contact with exposed surfaces of the exposed electrically conductive ground structures  130  at the cut side surfaces  144 . At operation  2750  the packages  100  are removed from the temporary carrier  300 . 
       FIGS. 28-30  are schematic cross-sectional side view illustrations of a packaging method including a full cut singulation process in accordance with an embodiment. Referring to  FIG. 28 , the packaging method may have been performed similarly as the process sequence illustrated in  FIGS. 16-20 . After encapsulation with the molding compound  140 , conductive bumps  160  (e.g. solder balls) may optionally be attached to the bond pads  110 . Exemplary sawing streets are illustrated in  FIG. 28 , where a full cut singulation process may be performed in which a full cut is made through the molding compound  140 , the plurality of electrically conductive ground structures  130  (e.g. the exemplary wire bonds  630  illustrated), and the wiring substrate  200 , for example using a blade or saw, to singulate one or more packages  100  and expose the plurality of electrically conductive ground structures  130  (e.g. wire bonds  630 ) at the cut side surfaces  144  of the molding compound  140 . 
     The one or more packages  100  may then be placed on a temporary carrier  300  such as a tape or adhesive layer, as illustrated in  FIG. 29 . An electrically conductive shield layer  150  may then deposited on the top surface  142  and the cut side surfaces  144  of the molding compound  140 , and also in physical contact with exposed surfaces  133  of the exposed electrically conductive ground structures  130  (e.g. wire bonds  630 ) at the cut side surfaces  144 , as illustrated in  FIG. 30 . As previously described, the packaging processes may be compatible with a variety of package substrates  102 , irrespective of package substrate  102  thickness. For example, as illustrated in  FIGS. 29-30  it is possible that a portion of the package substrate  102  thickness is embedded into the temporary carrier  300 . Since the exposed surfaces  133  of the electrically conductive ground structures  130  (e.g. wire bonds  630 ) are elevated above the top surface  104  of the package substrate  102 , a reliable contact may be made with the exposed surfaces  133  when depositing the electrically conductive shield layer  150 , with mitigated risk of the exposed surfaces  133  being embedded within the temporary carrier  300  and, thus inaccessible. 
     The packages  100  may then be removed from the temporary carrier, as illustrated in  FIG. 31 . The packages  100  illustrated in  FIG. 31  may be similar to those previously illustrated and described with regard to  FIG. 1 ,  FIG. 25 , or  FIG. 26 . One difference may be that the electrically conductive shield layer  150  may partially, or completely, span the side surfaces  103  of the package substrate  102 . The electrically conductive shield layer  150  may potentially span the side surfaces  103  of the package substrate  102  using a half cut processing sequence as well. 
     Referring now to  FIG. 32  a flow chart illustrating a packaging method including wire bonding to dummy pads is provided in accordance with an embodiment.  FIGS. 33-40  illustrate various schematic top view and cross-sectional side views of a packaging method including wire bonding to dummy pads is provided in accordance with an embodiment. In interest of clarity,  FIG. 32  is described concurrently and with reference to  FIGS. 33-40 . 
     At operation  3210  a plurality of die  120  and/or components  122  are attached to the top surface of the wiring substrate  200  (e.g. strip substrate, panel substrate) so that at least one die  120  and/or component  122  is located within each package area  101 , as illustrated in  FIG. 33 . At operation  3220  a plurality of wire bonds are bonded to one or more ground pads  108  and one or more dummy pads  118  at a top surface  104  of a wiring substrate  200 , such that each wire bond  630  is bonded to a corresponding ground pad  108  and a corresponding dummy pad  118 , as illustrated in  FIG. 34 . In an embodiment, the order of operations  3210 ,  3220  may be reversed. As shown in  FIGS. 33-34 , the dummy pads  118  may be arranged around/outside peripheries of the package areas  101 . In such an arrangement, the wire bond  630  wires  134  may extend from inside the package areas  101  to outside of the package areas  101 . While the embodiments illustrated in  FIGS. 32-33  show a plurality of ground pads  108  and dummy pads  118 , embodiments are also compatible with a ground pad  108  ring and/or dummy pad  118  ring. 
     At operation  3230  the plurality of die  120  and/or components  122 , and the plurality of wire bonds  630  are then encapsulated within a molding compound  140 , as illustrated in  FIGS. 35-36 . Following encapsulation, at operation  3240  the molding compound  140  and wire bonds  630  are cut, for example using a blade or saw, to expose the plurality of wire bonds  630  at the cut side surfaces  144  of the molding compound  140 .  FIG. 37  illustrates a plurality of saw streets prior to cutting, and  FIG. 38  illustrates a schematic cross-sectional side view of trenches  146  after a half cut. It is to be appreciated that while a half cut processing sequence is illustrated, that embodiments are not so limited and a full cut may also be made through the wiring substrate  200 . 
     Still referring to  FIG. 38 , following the cut, whether half cut or full cut, surfaces  133  of the bond areas  132  may be exposed at the side surfaces  144 , and/or surfaces  135  of the wires  134  may be exposed at the side surfaces  144 . For example, a cross-section of a width or diameter of the wires  134  is exposed. In an embodiment, both surfaces  133 ,  135  of the bond areas  132  and the wires  134  are exposed at the side surfaces  144 . 
     At operation  3250  an electrically conductive shield layer  150  (e.g. EMI shield layer) is then deposited on the top surface  142  and the cut side surfaces  144  of the molding compound  140 , and also in physical contact with exposed surfaces of the exposed wire bonds  630  at the cut side surfaces  144 , as illustrated in  FIG. 39 . In some embodiments, the electrically conductive shield layer  150  is not formed on side surfaces  103  of the package substrate  102 , though the electrically conductive shield layer  150  may be formed on side surfaces  103  of the package substrate  102 . In a half cut processing sequence, a plurality of packages may then be singulated along the saw lines illustrated in  FIG. 40 , resulting the package  100  structures illustrated in  FIG. 1 . 
     In utilizing the various aspects of the embodiments, it would become apparent to one skilled in the art that combinations or variations of the above embodiments are possible for forming package and package substrate for EMI shielding. Although the embodiments have been described in language specific to structural features and/or methodological acts, it is to be understood that the appended claims are not necessarily limited to the specific features or acts described. The specific features and acts disclosed are instead to be understood as embodiments of the claims useful for illustration.

Metadata:
Filing Date: 20160421
Publication Date: 20171017
Grant Date: 20171017
Priority Date: 20160421
Inventors: LEE MYUNGHO
Assignee: APPLE INC
CPC Classifications: [{"code": "H01L24/17", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L24/81", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L25/50", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L21/32051", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L2924/15311", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L21/561", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L21/4853", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L25/0655", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L21/78", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L23/49811", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L21/6835", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L23/3128", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L24/97", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L2924/3025", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L23/49838", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L23/552", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01L21/565", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L2924/01029", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/16227", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L23/552", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01L21/561", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L2924/3025", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L24/97", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L2924/181", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/15311", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/97", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/48227", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/00012", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/15331", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/15331", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/19105", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/19107", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/19107", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/19105", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/97", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/16227", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/16227", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L24/81", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L23/49811", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L21/561", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L23/3128", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L25/0655", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L2924/15311", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L21/32051", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L2924/3025", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L21/78", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L21/4853", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L24/97", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L2924/01029", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L24/17", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L23/552", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01L25/50", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L21/565", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L21/6835", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L23/49838", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 60022634