Abstract:
A semiconductor device has a first substrate having a plurality of metal traces. At least one electronic component is electrically attached to a first surface of the first substrate. A second substrate has a plurality of metal traces and attached to the first substrate. At least one electronic component is electrically attached to a first surface of the second substrate. An RF shield is formed on the first substrate to minimizing Electro-Magnetic Interference (EMI) radiation and Radio Frequency (RF) radiation to the at least one electronic component on the first substrate to form an RF shield. A mold compound is used for encapsulating the semiconductor device.

Description:
FIELD OF THE INVENTION 
     This invention relates to Radio Frequency (RF) shielding and, more specifically, to a system and method for providing compartmental shielding in a semiconductor package that lessens the footprint of semiconductor packages which use a side by side solution. 
     BACKGROUND OF THE INVENTION 
     Radio Frequency (RF) shielding may be required on certain semiconductor devices and modules (hereinafter semiconductor device) in order to minimize Electro-Magnetic Interference (EMI) radiation from the semiconductor device. RF shielding is further required to prevent RF radiation from external sources from interfering with operation of the semiconductor device. In a semiconductor device which integrates multiple functions/modules (front end module+transmitter, radio+baseband, etc.) compartmental shielding may be required to minimize EMI radiation from the different components/modules and to prevent RF radiation from interfering with operation of the different components/modules in the semiconductor device. 
     Presently, there are several different methods used for compartmental shielding of semiconductor devices which integrates multiple functions/modules. Known methods of compartmental shielding include embedded shields, metal cans with compartmental features, wire fences, and laser ablated vias. All of the above approaches are designed for side by side solutions for compartmental shielding. Side by side solutions requires additional space and thus increases the footprint of the semiconductor package. 
     Therefore, a need existed to provide a system and method to overcome the above problem. The system and method would provide for compartmental RF shielding of a semiconductor device which lessens the footprint of prior art semiconductor devices which use a side by side solution. 
     SUMMARY OF THE INVENTION 
     A semiconductor device has a first substrate having a plurality of metal traces. At least one electronic component is electrically attached to a first surface of the first substrate. A second substrate has a plurality of metal traces and attached to the first substrate. At least one electronic component is electrically attached to a first surface of the second substrate. A first set of contacts is attached to ground planes on a second surface of the second substrate and to the first surface of the first substrate. The first set of contacts is placed around the at least one electronic component on the first substrate to form an RF shield. A mold compound is used for encapsulating the semiconductor device. 
     A semiconductor device has a first substrate having a plurality of metal layers, wherein at least one metal layer is exposed on at least one side surface of the first substrate. A first electronic component is coupled to a first surface of the first substrate. A second substrate has a plurality of metal layers and is attached to the first substrate, wherein at least one metal layer is exposed on at least one side surface of the second substrate. A second electronic component is coupled to a first surface of the second substrate. A plurality of interconnects is coupled to metal layers on a second surface of the first substrate and the first surface of the second substrate. A mold compound is used for encapsulating the semiconductor device. A conductive coating is applied to the mold compound and to the at least one metal layer exposed on at least one side surface of the first substrate and second substrate. 
     The present invention is best understood by reference to the following detailed description when read in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional side view of one embodiment of the semiconductor device of the present invention; 
         FIG. 2A  is a top view of the semiconductor device depicted in  FIG. 1 ; 
         FIG. 2B  is a top view of the semiconductor device depicted in  FIG. 1  with the position of the first and second set of contacts switched; 
         FIG. 2C  is a top view of the semiconductor device depicted in  FIG. 1  with the position of the first and second set of contacts staggered; 
         FIG. 3  is a flow chart describing a method of forming the semiconductor device depicted in  FIG. 1 ; 
         FIG. 4  is a cross-sectional side view of another embodiment of the semiconductor device of the present invention; 
         FIG. 5  is a top view of the semiconductor device depicted in  FIG. 4 ; and 
         FIG. 6  is a flow chart describing a method of forming the semiconductor device depicted in  FIG. 4 . 
     
    
    
     Common reference numerals are used throughout the drawings and detailed description to indicate like elements. 
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 and 2A , a semiconductor device  10  (hereinafter device  10 ) is shown. The device  10  provides compartmental shielding which lessens the footprint of prior art semiconductor devices which use a side by side solution. 
     The device  10  has a first substrate  12 . The first substrate  12  may be any one chosen from a conventional rigid PCB, a flexible PCB, and an equivalent thereof, but the kind of first substrate  12  is not limited herein. The first substrate  12  includes an insulation layer  14  having predetermined area and thickness. The insulation layer  14  has an approximately planar first surface and an approximately planar second surface opposing the first surface. The first substrate  12  has a plurality of metal traces  16  formed on the first surface of the insulation layer  14 . A plurality of metal traces  16  may also be formed on the second surface of the insulation layer  14 . The number of metal traces  16  is not limited to the number shown in the Figures. If multiple layers of metal traces  16  are formed, a dielectric layer may be applied between the metal traces  16 . The dielectric layer is used as an insulating layer to separate two signal layers. A soldermask may be placed over the top surface of the metal traces  16  formed on the first substrate  12 . The soldeiinask is used to protect the metal traces  16 . 
     One or more electronic component  18  is attached to a first surface of the first substrate  12 . The electronic component  18  may be prepackaged semiconductor device, bare semiconductor die, or a passive component. The prepackaged semiconductor device may be a RF device, memory device, a logic device, an ASIC device, and other like elements. The prepackaged semiconductor device may also be a multi-chip module. It should be noted that the listing of the above types of prepackaged semiconductor devices is given as an example and should not be seen as to limit the scope of the present invention. The bare semiconductor die may be a RF device, memory die, a logic die, an ASIC die, and other like elements. It should be noted that the listing of the above types of bare semiconductor dies is given as an example and should not be seen as to limit the scope of the present invention. The passive component may be any type of passive electronic component. The passive component may be packaged singly such as a resistor, capacitor, transistor, diode, and the like or as an array of passive circuits. The listing of the above is given as an example and should not be seen as to limit the scope of the present invention. 
     The electronic component  18  is coupled to a first surface of the first substrate  12 . The electronic component  18  may be coupled to the first surface of the first substrate  12  in a plurality of different manners. In the embodiment shown in  FIGS. 1 and 2 , the electronic components  18  include bare semiconductor die. An adhesive  20  may be used to couple the die to the first substrate  12 . The adhesive  20  may be an adhesive film, an epoxy, or the like. The listing of the above adhesive types should not be seen as to limit the scope of the present invention. The die is then electrically coupled to the first substrate  12  through the use of wirebonds  22 . Alternatively, the die may be coupled to the substrate  12  through flip chip bonding, surface mount technology (SMT) or the like. 
     The device  10  has a second substrate  23 . The second substrate  23  may be any one chosen from a conventional rigid PCB, a flexible PCB, and an equivalent thereof, but the kind of substrate  23  is not limited herein. For example, the second substrate  23  may be a lead frame type structure. The second substrate  23  includes an insulation layer  24  having predetermined area and thickness. The insulation layer  24  has an approximately planar first surface and an approximately planar second surface opposing the first surface. The second substrate  23  has a plurality of metal traces  26  formed on the first surface of the insulation layer  24  and a plurality of metal traces  26  formed on the second surface thereof. The number of metal traces  26  is not limited to the number shown in the Figures. If multiple layers of metal traces  26  are formed, a dielectric layer is generally applied between the metal traces  26 . The dielectric layer is used as an insulating layer to separate two signal layers. A soldermask is generally placed over the top surface of the metal traces  26  formed on the second substrate  23 . The soldermask is used to protect the metal traces  26 . In the embodiment shown in  FIGS. 1 and 2 , the width of the second substrate  23  is less than the width of the first substrate  12 . 
     One or more electronic component  28  is coupled to a first surface of the second substrate  23 . The electronic component  28  may be prepackaged semiconductor device, bare semiconductor die, or a passive component. The prepackaged semiconductor device may be a RF device, memory device, a logic device, an ASIC device, and other like elements. The prepackaged semiconductor device may also be a multi-chip module. It should be noted that the listing of the above types of prepackaged semiconductor devices is given as an example and should not be seen as to limit the scope of the present invention. The bare semiconductor die may be a RF device, memory die, a logic die, an ASIC die, and other like elements. It should be noted that the listing of the above types of bare semiconductor dies is given as an example and should not be seen as to limit the scope of the present invention. The passive component may be any type of passive electronic component. The passive component may be packaged singly such as a resistor, capacitor, transistor, diode, and the like or as an array of passive circuits. The listing of the above is given as an example and should not be seen as to limit the scope of the present invention. 
     The electronic component  28  may be coupled to the first surface of the second substrate  23  in a plurality of different manners. The electronic component  28  may be attached to the first surface of the second substrate  23  with an adhesive  30  and wirebonded. Alternatively, the electronic component  28  may be coupled to the second substrate  23  through flip chip bonding, surface mount technology (SMT) or the like. 
     The second substrate  23  is coupled to the first surface of the first substrate  12  so as to be elevated above the first surface of the first substrate  12 . A first set of contacts  32  are used to attach a second surface of the second substrate  23  to the first surface of the first substrate  12 . The first set of contacts  32  are positioned around a first perimeter of the second surface of the second substrate  23  and attach to metal traces  26  of the second substrate  23  which acts as a ground plane. The first set of contacts  32  are also attached to metal traces  16  on the first surface of the first substrate  12  which acts as a ground plane. Thus, the first set of contacts  32  is grounded creating an RF shield around the electronic components  18  on the first surface of the first substrate  12 . The first set of contacts  32  may be a plurality of solder balls as shown in  FIGS. 1 and 2A . 
     A second set of contacts  34  may be placed around a second perimeter of the second substrate  23 . The second set of contacts  34  can be used to provide an electrical connection between metal traces  16  on the first substrate  12  and metal traces  26  on the second substrate  23 . The second set of contacts  34  may be a plurality of solder balls as shown in  FIGS. 1 and 2A . As shown in  FIG. 2A , the first set of contacts  32  may be placed inside of the second set of contacts  34 . In an alternative embodiment as shown in  FIG. 2B , the contacts  32  may be placed around an outer perimeter of the second substrate  12  and contacts  34  may be placed inside the perimeter formed by the contacts  32 . In still another embodiment as shown in  FIG. 2C , the contacts  32  and  34  may be placed in a staggered pattern wherein the contacts  34  are placed in front of and behind the contacts  32 . 
     A mold compound  36  is used to encapsulate the device  10 . The mold compound  36  is mainly made of thermosetting plastic material like epoxy. The mold compound  36  is used to encapsulate the components of the device  10  (i.e., electronic components  18  and  28 ), the second substrate  23 , and the first and side surfaces of the first substrate  12 . 
     A third set of contacts  38  may be coupled to the second surface of the first substrate  12 . In the embodiment shown in  FIGS. 1 and 2 , the third set of contacts  38  are solder balls  38 . If solder balls  38  are used, the solder balls  38  will be electrically coupled to the second surface of the first substrate  12 . In general, a reflow process may be used to couple the solder balls  38  to the second surface of the first substrate  12 . Alternative methods may be used to couple different types of contacts to the first substrate  12  without departing from the spirit and scope of the present invention. 
     Referring to  FIGS. 1-3 , a method of forming the device  10  is shown. The device  10  is generally assembled in strip fashion. Thus, a plurality of devices  10  are formed from a single substrate strip. As shown in Step  100 , one or more electronic component  18  are attached to a first surface of the first substrate  12 . The electronic component  18  may be coupled to the first surface of the first substrate  12  in a plurality of different manners. In accordance with one embodiment, an adhesive  20  may be used to couple the bare die electronic component  18  to the first substrate  12 . The adhesive  20  may be an adhesive film, an epoxy, or the like. The listing of the above adhesive types should not be seen as to limit the scope of the present invention. The electronic component  18  is then electrically coupled to the first substrate  12  through the use of wirebonds  22 . Alternatively, the electronic component  18  may be coupled to the substrate  12  through flip chip bonding, surface mount technology (SMT) or the like. Step  100  may also performed for components  28  coupled to substrate  23  in a separate strip form assembly flow followed by a singulation process to remove a unit assembly from the multiple unit strip. 
     Next as shown in Step  110 , a first set of contacts  32  are positioned around a first perimeter of a second surface of a second substrate  23  and attach to metal traces  26  of the second substrate  23  which acts as a ground plane. A second set of contacts  34  may be placed around a second perimeter of the second substrate  23  and attached to metal traces  26 . 
     A module is coupled to the first surface of the first substrate  12  so as to be elevated above the first surface of the first substrate  12  as shown in Step  120 . The module comprises the second substrate  23  having one or more electronic component  28  coupled to a first surface of the second substrate  23 . The electronic component  28  may be coupled to the first surface of the second substrate  23  in a plurality of different manners. The electronic component  28  may be attached to the first surface of the second substrate  23  with an adhesive  30  and wirebonded. Alternatively, the electronic component  28  may be coupled to the second substrate  23  through flip chip bonding, surface mount technology (SMT) or the like. 
     The module is attached so that the first set of contacts  32  are attached to metal traces  16  on the first surface of the first substrate  12  which acts as a ground plane. Thus, the first set of contacts  32  is grounded creating an RF shield around the electronic components  18  on the first surface of the first substrate  12 . The first set of contacts  32  may be a plurality of solder balls as shown in  FIGS. 1-2C . The second set of contacts  34  which are attached to metal traces  16  on the first surface of the first substrate can be used to provide an electrical connection between the first substrate  12  and the second substrate  23 . The second set of contacts  34  may also be a plurality of solder balls as shown in  FIGS. 1-2C . The first set of contacts  32  may be placed inside of the second set of contacts  34  as shown in  FIG. 2A . In an alternative embodiment as shown in  FIG. 2B , the contacts  32  may be placed around an outer perimeter of the second substrate  12  and contacts  34  may be placed inside the perimeter formed by the contacts  32 . In still another embodiment as shown in  FIG. 2C , the contacts  32  and  34  may be placed in a staggered pattern wherein the contacts  34  are placed in front of and behind the contacts  32 . 
     A mold compound  36  is used to encapsulate the device  10  as shown in Step  130 . The mold compound  36  is mainly made of thermosetting plastic material like epoxy. The mold compound  36  is used to encapsulate the components of the device  10  (i.e., electronic components  18  and  28 ), the second substrate  23 , and the first and side surfaces of the first substrate  12 . 
     A third set of contacts  38  may be coupled to the second surface of the first substrate. In the embodiment shown in  FIGS. 1-2C , the third set of contacts  38  are solder balls  38 . If solder balls  38  are used, the solder balls  38  will be electrically coupled to the second surface of the first substrate  12 . In general, a reflow process may be used to couple the solder balls  38  to the second surface of the first substrate  12 . Alternative methods may be used to couple different types of contacts to the first substrate  12  without departing from the spirit and scope of the present invention 
     Referring to  FIGS. 4-6 , another embodiment of the device  10 ′ is shown. The device  10 ′ provides compartmental shielding which lessens the footprint of prior art semiconductor devices which use a side by side solution. 
     Like the previous embodiment, the device  10 ′ has a first substrate  12 . The first substrate  12  includes an insulation layer  14  having predetermined area and thickness. The first substrate  12  has a plurality of metal traces  16  formed on the first surface of the insulation layer  14 . A plurality of metal traces  16  may also be formed on the second surface of the insulation layer  14 . The number of metal traces  16  is not limited to the number shown in the Figures. If multiple layers of metal traces  16  are formed, a dielectric layer may be applied between the metal traces  16 . The dielectric layer is used as an insulating layer to separate two signal layers. A soldermask may be placed over the top surface of the metal traces  16  formed on the first substrate  12 . The soldermask is used to protect the metal traces  16 . 
     One or more electronic component  18  is attached to the first surface of the first substrate  12 . The electronic component  18  may be any type of active or passive device. The electronic component  18  may be coupled to the first surface of the first substrate  12  in a plurality of different manners. In accordance with one embodiment, an adhesive  20  may be used to couple the electronic component  18  to the first substrate  12 . The adhesive  20  may be an adhesive film, an epoxy, or the like. The electronic component  18  is then electrically coupled to the first substrate  12  through the use of wirebonds  22 . Alternatively, the electronic component  18  may be coupled to the substrate  12  through flip chip bonding, surface mount technology (SMT) or the like. 
     The device  10 ′ has a second substrate  23 . The second substrate  23  includes an insulation layer  24  having predetermined area and thickness. The second substrate  23  has a plurality of metal traces  26  formed on the first surface of the insulation layer  24  and a plurality of metal traces  26  formed on the second surface thereof. If multiple layers of metal traces  26  are formed, a dielectric layer may be applied between the metal traces  26 . The dielectric layer is used an insulating layer to separate two signal layers. A soldermask may be placed over the top surface of the metal traces  26  formed on the second substrate  23 . The soldermask is used to protect the metal traces  26 . In the embodiment shown in  FIGS. 4-6 , the width of the second substrate  23  is approximately the same as the width of the first substrate  12 . 
     One or more electronic component  28  is coupled to the first surface of the second substrate  23 . The electronic component  28  may be any type of active or passive device. The component  28  may be coupled to the first surface of the second substrate  23  in a plurality of different manners. If a bare die active or passive device  28 , it may be attached to the first surface of the second substrate  23  with an adhesive  30  and wirebonded. Alternatively, the component  28  may be coupled to the second substrate  23  through flip chip bonding, surface mount technology (SMT) or the like. 
     The second substrate  23  is coupled to the first surface of the first substrate  12  so as to be elevated above the first surface of the first substrate  12 . Contacts  33  are used to attach the second surface of the second substrate  23  to the first surface of the first substrate  12 . The contacts  33  are positioned around a perimeter or in an array fashion on the second surface of the second substrate  23  and attach to metal traces  26  of the second substrate  23 . Contacts  33  are also attached to metal traces  16  on the first surface of the first substrate  12 . Contacts  33  may be used to transfer electrical signals between the first substrate  12  and the second substrate  23 , or act as power/ground supplies. 
     A mold compound  36  is used to encapsulate the device  10 ′. The mold compound  26  is mainly made of thermosetting plastic material like epoxy. The mold compound  36  is used to encapsulate the electronic components  18  and  28  of the device  10 ′, the second substrate  23 , and the first surface and side surfaces of the first substrate  12 . 
     To provide compartmental shielding for the device  10 ′, at least one metal trace  16  may be exposed on a side surface of the first substrate  12 . At least one metal trace  26  may also be exposed on a side surface of the second substrate  23 . The exposed metal trace  16  and/or  26  will be used as ground planes. 
     The side surface of the first substrate  12  is generally a surface adjacent to the first surface of the first substrate  12 . In the embodiment shown in  FIGS. 4-6 , the side surface is the surface adjacent and approximately perpendicular to the first surface of the first substrate  12 . In a similar manner, the side surface of the second substrate  23  is generally a surface adjacent to the first surface of the second substrate  23 . In the embodiment shown in  FIGS. 4-6 , the side surface is the surface adjacent and approximately perpendicular to the first surface of the second substrate  12 . All four sides of the device  10 ′ may be formed so that one of the metal  16  and/or  26  is exposed on each side of the device  10 ′. 
     A conductive coating  42  is then applied to the device  10 ′. The conductive coating  42  is used to provide RF shielding for the device  10 ′. The conductive coating  42  may be applied by plating, vacuum printing, vacuum deposition, insert molding, spray coating, and the like. The conductive coating  42  is applied to the top surface of the device  10 ′ and to the side surfaces of the device  10 ′. The conductive coating  42  is applied so that the conductive coating  42  will be in contact with the exposed metal traces  16  and/or  26 . Thus, the device  10 ′ will have a conductive coating  42  that contacts grounded metal (i.e., the exposed metal traces  16  and/or  26 ). The conductive coating  42  in contact with the exposed metal trace  16  creates a compartmental RF shield around the electronic component  18  on the first surface of the first substrate  12 . In a similar manner, the conductive coating  42  in contact with the exposed metal trace  26  creates a compartmental RF shield around the electronic component  28  on the first surface of the second substrate  23 . 
     In  FIGS. 4-6 , the conductive coating  42  is a conformal coating. In a conformal coating, a thin layer of the conductive coating  42  is applied to the top surface of the device  10 ′ and to the side surface of the device  10 ′. The conductive coating  42  is applied to the side surface of the device  10 ′ so that the side surface will have a thin layer of conductive coating  42  similar in thickness to the conductive coating applied to the top surface of the device  10 ′. 
     A non-conductive coating  48  may be applied to the conductive coating  42 . The non-conductive coating  48  is used as a protective layer to protect the conductive coating  42  and hence the device  10 ′ from solvents, solders, fluxes, etc. The non-conductive coating  48  may be applied to the stacked device  10 ′ or to a single package device having a conductive coating  42 . Although  FIG. 4  shows the non-conductive coating  48 , the non-conductive coating  48  is an optional element. 
     Electrical contacts  38  may be coupled to the second surface of the first substrate  12 . In the embodiment shown in  FIGS. 4 and 5 , the electrical contacts  38  are solder balls  38 . If solder balls  38  are used, the solder balls  38  will be electrically coupled to the second surface of the first substrate  12 . In general, a reflow process may be used to couple the solder balls  38  to the second surface of the first substrate  12 . Alternative methods may be used to couple different types of contacts to the first substrate  12  without departing from the spirit and scope of the present invention. 
     Referring now to  FIGS. 4-6 , a method of foaming the semiconductor device  10 ′ will be described. The semiconductor device  10 ′ is assembled in strip fashion as shown. Thus, a plurality of semiconductor devices  10 ′ are formed from a single substrate strip. The substrate strip is segmented into a plurality of rows and columns to form individual semiconductor devices  10 ′. 
     As shown in Step  200 , one or more electronic component  18  is attached to a first surface of the first substrate  12 . The electronic component  18  may be coupled to the first surface of the first substrate  12  in a plurality of different manners. In accordance with one embodiment, an adhesive  20  may be used to couple the electronic component  18  to the first substrate  12 . The adhesive  20  may be an adhesive film, an epoxy, or the like. The electronic component  18  is then electrically coupled to the first substrate  12  through the use of wirebonds  22 . Alternatively, the electronic component  18  may be coupled to the substrate  12  through flip chip bonding, surface mount technology (SMT) or the like. Step  200  may also performed for components  28  coupled to substrate  23  in a separate strip form assembly flow possibly followed by a singulation process to remove a unit or a sub group of assembled units from the multiple unit strip. 
     A module is then coupled to the first surface of the first substrate  12  so as to be elevated above the first surface of the first substrate  12  as shown in Step  210 . The module comprises a second substrate  23 . One or more electronic component  28  is coupled to the first surface of the second substrate  23 . The electronic component  28  may be coupled to the first surface of the second substrate  23  in a plurality of different manners. The electronic component  28  may be attached to the first surface of the second substrate  23  with an adhesive  30  and wirebonded. Alternatively, the electronic component  28  may be coupled to the second substrate  23  through flip chip bonding, surface mount technology (SMT) or the like. 
     The second substrate  23  is coupled to the first surface of the first substrate  12  so as to be elevated above the first surface of the first substrate  12 . Connectors  33  are used to attach the second surface of the second substrate  23  to the first surface of the first substrate  12 . Connectors  33  are positioned around a perimeter of the second surface of the second substrate  23  and attach to metal traces  26  of the second substrate. Connectors  33  are also attached to metal traces  16  on the first surface of the first substrate  12 . Connectors  33  may be used to transfer electrical signals between the first substrate  12  and the second substrate  23 , or act as power/ground nodes. 
     Next as shown in Step  220 , a mold compound  36  is used to encapsulate the device  10 ′. The mold compound  36  is mainly made of thermosetting plastic material like epoxy. The mold compound  36  is used to encapsulate the electronic components  18  and  28  of the device  10 ′, the second substrate  23 , and the first surface and side surfaces of the first substrate  12 . 
     To provide compartmental shielding for the device  10 ′, at least one metal trace  16  may be exposed on a side surface of the first substrate  12  as shown in Step  230 . At least one metal trace  26  may also be exposed on a side surface of the second substrate  23 . The exposed metal trace  16  and/or  26  will be used as ground planes. The metal trace  16  and/or  26  may be exposed by performing a saw cut to singulate the substrate strip to form the individual semiconductor devices  10 ′. Other methods may be used to expose the metal trace  16  and/or  26  without departing from the spirit and scope of the present invention. 
     A conductive coating  42  is then applied to the device  10 ′ as shown in Step  240 . The conductive coating  42  is used to provide RF shielding for the device  10 ′. The conductive coating  42  may be applied by plating, vacuum printing, vacuum deposition, insert molding, spray coating, and the like. The conductive coating  42  is applied to the top surface of the device  10 ′ and to the side surfaces of the device  10 ′. The conductive coating  42  is applied so that the conductive coating  42  will be in contact with the exposed metal traces  16  and/or  26 . Thus, the device  10 ′ will have a conductive coating  42  that contacts grounded metal (i.e., the exposed metal traces  16  and/or  26 ). The conductive coating  42  in contact with the exposed metal trace  16  creates a compartmental RF shield around the electronic components  18  on the first surface of the first substrate  12 . In a similar manner, the conductive coating  42  in contact with the exposed metal trace  26  creates a compartmental RF shield around the electronic components  28  on the first surface of the second substrate  23 . 
     A non-conductive coating  48  may be applied to the conductive coating  42 . The non-conductive coating  48  is used as a protective layer to protect the conductive coating  42  and hence the device  10 ′ from solvents, solders, fluxes, etc. The non-conductive coating  48  may be applied to the stacked device  10 ′ or to a single package device having a conductive coating  42 . 
     Electrical contacts  38  may be coupled to the second surface of the first substrate  12 . In the embodiment shown in  FIGS. 4 and 5 , the electrical contacts  38  are solder balls  38 . If solder balls  38  are used, the solder balls  38  will be electrically coupled to the second surface of the first substrate  12 . In general, a reflow process may be used to couple the solder balls  38  to the second surface of the first substrate  12 . Alternative methods may be used to couple different types of contacts to the first substrate  12  without departing from the spirit and scope of the present invention. 
     This disclosure provides exemplary embodiments of the present invention. The scope of the present invention is not limited by these exemplary embodiments. Numerous variations, whether explicitly provided for by the specification or implied by the specification, such as variations in structure, dimension, type of material and manufacturing process may be implemented by one of skill in the art in view of this disclosure.