PATENT DOCUMENT

Publication Number: US-9030841-B2
Application Number: US-201213593075-A
Country: US
Kind Code: B2

Title: Low profile, space efficient circuit shields

Abstract:
A low profile, space efficient circuit shield is disclosed. The shield includes top and bottom metal layers disposed on the top of and below an integrated circuit. In one embodiment the shield can include edge plating arranged to encircle the edges of the integrated circuit and couple the top and bottom metal layers together. In another embodiment, the shield can include through vias arranged to encircle the edges of the integrated circuit and couple the top and bottom metal layers together. In yet another embodiment, passive components can be disposed adjacent to the integrated circuit within the shield.

Claims:
What is claimed is: 
     
       1. A small form factor shield device, comprising:
 an integrated circuit assembly, comprising:
 an integrated circuit, comprising at least two conductive contact pads, and 
 a matrix formed of insulative material that fully encapsulates the integrated circuit; and 
 
 a conformable electromagnetic interference (EMI) shield formed of a flexible conductor wrapped directly around at least a top and a bottom portion of the integrated circuit assembly and configured to conform to a shape of the top and bottom portion of the integrated circuit assembly such that the wrapped integrated circuit assembly comprising the conformable EMI shield and the integrated circuit assembly is substantially the same size as the integrated circuit assembly alone; 
 a flexible circuit coupled with the conformable EMI shield and comprising electrically conductive pathways separate and distinct from each other, at least one of the electrically conductive pathways being electrically coupled with and grounded through the conformable EMI shield; and 
 vias disposed around a periphery of the integrated circuit, each of the vias embedded within the matrix and extending from the top portion of the matrix to the bottom portion of the matrix, thereby electrically coupling a first portion of the conformable EMI shield disposed along the top portion to a second portion of the conformable EMI shield disposed along the bottom portion. 
 
     
     
       2. The small form factor shield device as recited in  claim 1 , wherein the plurality of vias cooperate to prevent EMI from escaping unshielded lateral portions of the integrated circuit assembly. 
     
     
       3. The small form factor shield device as recited in  claim 1 , wherein the small form factor shield device is surface mounted to a printed circuit board. 
     
     
       4. The small form factor shield device as recited in  claim 1 , further comprising a conductive edge plating creating an additional electrically conductive pathway between the top and bottom portions of the conformable EMI shield. 
     
     
       5. The small form factor shield device as recited in  claim 1 , wherein the conformable EMI shield is electrically coupled with the integrated circuit. 
     
     
       6. The small form factor shield device as recited in  claim 1 , wherein the conformable EMI shield is configured to be grounded through a grounding path separate and distinct from electrically conductive pathways associated with the integrated circuit. 
     
     
       7. The small form factor shield device as recited in  claim 1 , further comprising at least one passive component embedded in the matrix. 
     
     
       8. The small form factor shield device as recited in  claim 7 , wherein the at least one passive component is one of a resistor, capacitor or inductor. 
     
     
       9. The small form factor shield device as recited in  claim 1 , wherein the conformable shield comprises a sheet of metal foil between 10-100 microns thick. 
     
     
       10. The small form factor shield device as recited in  claim 1 , wherein the matrix has a rectangular geometry with chamfered corners, the chamfered corners increasing an amount of other components that can be mounted on a circuit board along side the small form factor shield device.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 61/602,529, filed Feb. 23, 2012, entitled “LOW PROFILE, SPACE EFFICIENT CIRCUIT SHIELDS,” and to U.S. Provisional Patent Application No. 61/613,427, filed Mar. 20, 2012, entitled “LOW PROFILE, SPACE EFFICIENT CIRCUIT SHIELDS,” which are incorporated herein by reference in their entireties and for all purposes. 
    
    
     FIELD OF THE DESCRIBED EMBODIMENTS 
     The described embodiments relate generally to shielding electrical components and more particularly to low-profile, space efficient electrical shields. 
     BACKGROUND 
     Electromagnetic interference (EMI) signals can adversely affect the performance and function of electrical devices. Some electrical devices can be sensitive to radiated EMI signals from other devices. For example, a low noise amplifier may provide substantial gain to an input signal; however, the performance of the amplifier may be negatively affected by the presence of interfering EMI signals on the amplifier inputs. The EMI signals can distort or otherwise cause errors in the sensitive input section and as a result the output of the amplifier can become distorted. To protect electrical devices from receiving unintentional EMI radiation, the strength of emitted electromagnetic interference is typically regulated by governmental agencies. 
     A common device used to control both emission and reception of EMI signals is a metallic shield employed to cover electrical components. The shield protects sensitive electrical parts from receiving stray EMI signals and can also limit the radiation of EMI signals. Shields function by providing a low impedance pathway for EMI signals. Shields are typically constructed of metal, such as steel or, in some instances, can be constructed with conductive paint over an insulator such as plastic. 
     As described, traditional shield implementations cover one or more electrical components. Unfortunately traditional shield implementations can increase area used on supporting substrates such as a printed circuit board (PCB). Increased area can be due, at least in part, to air gaps commonly used between protected components and the shield. The air gap may ease assembly and installation of the shield on the supporting substrate. As product designs are driven smaller, the areas of related modules such as printed circuit boards are driven to be smaller as well. Thus, there is a desire to decrease the area need to support shield implementations, particularly on supporting substrates such as PCBs. 
     Therefore, what is desired is space efficient shield assembly to attenuate interfering electrical signals for use on supporting substrates. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The described embodiments and the advantages thereof may best be understood by reference to the following description taken in conjunction with the accompanying drawings. These drawings in no way limit any changes in form and detail that may be made to the described embodiments by one skilled in the art without departing from the spirit and scope of the described embodiments. 
         FIG. 1  is a simplified diagram of one embodiment of a small form factor shield system. 
         FIG. 2  is a simplified diagram of another embodiment of a small form factor shield system. 
         FIG. 3  is a simplified diagram of yet another embodiment of a small form factor shield system. 
         FIG. 4  is a simplified diagram of still another embodiment of a small form factor shield system. 
         FIG. 5  is a simplified diagram of another embodiment of a small form factor shield system. 
         FIG. 6  is simplified diagram of yet another embodiment of a small form factor shield system. 
         FIG. 7  is a flow chart of method steps for forming a low profile, space efficient EMI shield. 
         FIG. 8  is a diagram of a low profile shield system supporting a flex circuit. 
         FIGS. 9A and 9B  illustrate two views of a low profile shield assembly. 
         FIG. 10  illustrates another embodiment of a low profile shield assembly. 
         FIG. 11  is a flow chart of method steps for forming shield system. 
     
    
    
     DETAILED DESCRIPTION OF SELECTED EMBODIMENTS 
     Representative applications of methods and apparatus according to the present application are described in this section. These examples are being provided solely to add context and aid in the understanding of the described embodiments. It will thus be apparent to one skilled in the art that the described embodiments may be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order to avoid unnecessarily obscuring the described embodiments. Other applications are possible, such that the following examples should not be taken as limiting. 
     In the following detailed description, references are made to the accompanying drawings, which form a part of the description and in which are shown, by way of illustration, specific embodiments in accordance with the described embodiments. Although these embodiments are described in sufficient detail to enable one skilled in the art to practice the described embodiments, it is understood that these examples are not limiting; such that other embodiments may be used, and changes may be made without departing from the spirit and scope of the described embodiments. 
     Shielding techniques are widely practiced to control the effects of unwanted electromagnetic interference (EMI). Shielding can be used to not only protect sensitive components from absorbing unwanted EMI, but can also be used to prevent unintended emission of EMI signals. Traditional shielding techniques, however, can be bulky and can impose design constraints by requiring excessive area on mounting substrates such as a printed circuit boards. 
     A low-profile, space efficient integrated shield solution is disclosed. In one embodiment, an integrated circuit is surrounded by top and bottom metal layers and edge plating forming a shield around the integrated circuit. In one embodiment, the shield can be coupled to a signal shared with the integrated circuit. In another embodiment, the shield can be isolated from the integrated circuit. For example the shield can be coupled to a signal separate from the signal coupled to the integrated circuit. In certain embodiments the separate signal is ground signal. In yet another embodiment, the edge plating can be replaced with through vias that both couple the top and bottom metal layers and also act as an edge shield. In still another embodiment, passive components can be included within the shield with the integrated circuit. 
       FIG. 1  is a simplified diagram of one embodiment small form factor shield system  100  in accordance with the specification. The shield system  100  can include integrated circuit  102  and substrate  110 . Substrate  110  can be a printed circuit board, flex circuit or other technically feasible material. In one embodiment, integrated circuit  102  can be embedded within a suitable matrix  104  such as a resin, fiberglass, epoxy or other insulative material. In one embodiment, integrated circuit  102  can be a ball grid array, CSP, PLCC or other feasible integrated circuit package. 
     Integrated circuit  102  or the combination of integrated circuit  102  and matrix  104  can be effectively wrapped with a shield. In one embodiment, shield  101  can include shield top  120 , shield bottom  122  and shield edge plating  124 . Shield  101  can be formed out of thin metal foil such as copper, aluminum, steel or other suitable material. By attaching shield  101  directly to integrated circuit  102  (or integrated circuit  102  and matrix  104  combination), substantial area can be saved on substrate  110  because the combination of shield  101  and integrated circuit  102  need not require much more surface area than integrated circuit  102  alone. In some embodiments shield  101  can be formed from metal foil, only a few microns thick. For example, the foil can range from 10 microns to 100 microns thick. Differing foil thicknesses can attenuate differing EMI frequencies. In one embodiment, the foil thickness can be selected to reduce a particular target frequency. In another embodiment, the foil thickness can be selected to increase or decrease an amount of EMI attenuation. 
     Integrated circuit  102  signals can be coupled through terminals  130 , laser vias  132  and bumps  134 . In one embodiment, laser vias  132  are formed before shield  101  is formed. That is, shield  101  is formed to have openings therein corresponding to the locations of laser vias  132 . In one embodiment bumps  134  can be balls, solder balls or other suitable feature allowing the coupling of signals to pads  106 . In one embodiment, shield  101  can be coupled to one or more bumps  134  shared in common with integrated circuit  102 . In this way, when bump  134  is coupled to ground, then shield  101  is also coupled to ground. This arrangement can reduce or eliminate the need for dedicated pads needed to support shield signal coupling. In one embodiment, shield  101  can be used as a contact point or support point for other components such as a flex circuit. For example, when shield  101  is coupled to ground, then a separate flex circuit can couple a flex circuit ground signal to shield  101 . 
       FIG. 2  is a simplified diagram of another embodiment a small form factor shield system  200  in accordance with the specification. Similar to  FIG. 1 , this embodiment includes an integrated circuit  102  within a matrix  104  mounted on a substrate  110 . Shield top  120  and shield bottom  122  can be disposed above and below and in contact with matrix  104 . Through vias  202  can couple shield top  120  to shield bottom  122 . Though vias  202  can be placed around the perimeter of integrated circuit  102  and replace the need for edge plating  124 . Thus, shield  201  can include shield top  120 , shield bottom  122  and through vias  202 . Shield  201  can be coupled to bump  134  as described in  FIG. 1  to connect shield  201  to a ground signal already used by integrated circuit  102 . In one embodiment, matrix  104  can support two or more sub-layers, similar to printed circuit board designs. Through vias  202  can be stacked vertically to couple shield top  120  to shield bottom  122  through sub-layers within matrix  104 . 
       FIG. 3  is a simplified diagram of yet another embodiment of a small form factor shield system  300  in accordance with the specification. The shield system  300  includes integrated circuit  102  and substrate  110  as described above in  FIG. 2 . Shield  301  can include shield top  120 , shield bottom  122  and edge plating  124 . In this embodiment, shield  301  can be isolated with respect to other signals that can be coupled to integrated circuit  102 . As shown, shield  301  can be coupled to a dedicated bump  302 . In turn, bump  302  can be coupled to a signal through pad  304  on substrate  110 . This signaling arrangement enables shield  301  to be coupled to isolated signals with respect to the integrated circuit  102 . For example, integrated circuit may use a local voltage reference such as analog ground, while shield  301  can be coupled to a different signal such as digital ground. 
       FIG. 4  is a simplified diagram of still another embodiment of a small form factor shield system  400  in accordance with the specification. Shield system  400  can include integrated circuit  102  and substrate  110  as described above. Shield top  120  and shield bottom  122  are again placed above and below the integrated circuit  102 . In this embodiment, instead of using edge plating  124 , through vias  202  are used to couple shield top  120  to shield bottom  122 . Thus, shield  401  can include shield top  120 , shield bottom  122  and through vias  202 . As described in  FIG. 3 , shield  401  can be isolated with respect to other signals that can be coupled to integrated circuit  102 . Thus, shield  401  can be coupled to isolated signals with respect to integrated circuit  102 . 
       FIG. 5  is a simplified diagram of another embodiment of a small form factor shield system  500  in accordance with the specification. Shield system  500  includes integrated circuit  102  and substrate  110 . Shield  501  can include shield top,  120 , shield bottom  122  and edge plating  124 . In this embodiment, the volume enclosed by the shield  501  can be increased relative to the size of integrated circuit  102 . The increase in volume can support one or more passive components  502  that can also be embedded in matrix  104 . A passive component can be a resistor, capacitor, inductor or the like. In one embodiment, signals can be coupled between integrated circuit  102  and passive component  502 . For example, passive component  502  can be a bus termination resistor that can be coupled to integrated circuit  102 . In one embodiment, shield  501  can be isolated from other signals going to or coming from integrated circuit  102  as described in  FIG. 3 . In another embodiment, shield  501  can be coupled to bump  134  that can be shared with integrated circuit  102 . 
       FIG. 6  is simplified diagram of yet another embodiment of a small form factor shield system  600  in accordance with the specification. Shield  601  can include shield top  120 , shield bottom  122  and through vias  202 . The volume enclosed by shield  601  and the volume of matrix  104  can be increased to allow one or more passive components  502  to be embedded with integrated circuit  102 . In one embodiment, shield  601  can be isolated from other signals going to or coming from integrated circuit  202 . In another embodiment, shield  601  can be coupled to at least one signal going to or coming from integrated circuit  102 . In one embodiment, signals can be coupled between passive component  502  and integrated circuit  102 . 
       FIG. 7  is a flow chart of method steps  700  for forming a low profile, space efficient EMI shield. Persons skilled in the art will appreciate that any system executing the following steps in any order is within the scope of the disclosed method steps. The method begins in step  702  where an integrated circuit  102  is obtained. In one embodiment, integrated circuit  102  can include solder bumps. In other embodiments, integrated circuit  102  can include solder balls or other similar features. In step  704 , metal components for the EMI shield are obtained. In one embodiment, metal components can include shield top  120  and shield bottom  122  as well as edge plating  124  can be obtained. In step  706 , metal components are attached to integrated circuit  102 . In one embodiment, integrated circuit  102  can be embedded within matrix  104 ; therefore, metal components can be attached to matrix  104 . In step  708 , metal components can be coupled together to form the EMI shield and the method ends. 
       FIG. 8  is a diagram of a low profile shield system  800  supporting a flex circuit. Shield  801  can include shield top  120 , shield bottom  122  and edge plating  124 . Shield  801  can be coupled to bump  134 . Bump  134  can be coupled to a signal through pad  106 , thereby coupling shield  801  to the signal on pad  106 . In one embodiment, the signal on pad  106  can be a ground signal, thus shield  801  can be coupled to the ground signal. Flex circuit  803  can be configured to couple at least one signal to shield  801 . In one embodiment, flex circuit  803  can be disposed on, and in direct contact with shield  801 . In one embodiment, flex circuit  803  can be attached with a conductive adhesive to shield  801  coupling an exposed trace or wire within flex circuit  803  to shield  801 . In one embodiment, when shield  801  is coupled to ground, one or more signals in flex circuit  803  can also be coupled to ground. For example, flex circuit may include a ground plane that can be coupled to ground through shield  801 . 
       FIGS. 9A and 9B  illustrate two views of a low profile shield assembly  900 .  FIG. 9A  shows assembly  900  from a top view. In this embodiment, integrated circuit  102  is embedded in matrix  104  to form a low profile shield system  914 . The initial size of matrix  104 , however, can be larger than the finished dimension of the shield system  914 . The shield system  914  can include embedded integrated circuit  102  surrounded by shield  901  which can include edge plating  912  and shield top  120  and shield bottom (not shown). In one embodiment, matrix  104  can act as a carrier for the integrated circuit  102  and shield  901 . Matrix  104 , thusly configured, can enable easier assembly, handling and manufacturing of shield system  914 . 
     In one embodiment shield top  120  can receive a solder mask. The solder mask can resist solder especially as shield system  914  may be attached to a circuit board though a flow or re-flow soldering technique. In another embodiment, at least a portion of shield top  120  can be free from a solder mask to allow the attaching of a heat sink, heat pipe or other thermal conductive solution. In one embodiment, matrix  104  can be minimized over integrated circuit  102  in area  950  to help increase thermal transfer from integrated circuit  102 . 
       FIG. 9A  also shows pads  934  for coupling signals to integrated circuit  102  and shield  901 . Pads  934  can couple signals through laser vias  936  to integrated circuit  102 . In one embodiment, shield system  914  can include 30 pads. Other embodiments can include more or few bumps as may be required to support integrated circuit  102 . Note that shield bottom  122  can exist between pads  934  to enhance shield  901  performance. Matrix  104  can include routed areas  910 . Routed areas  910  can enable edge plating  912  to be applied while the shield system  914  is still mounted in matrix  104  (acting as a carrier). Routed areas  910  can be formed with a router, laser drill or with any other technically feasible approach. Edge plating  912  can be applied through routed areas  910  and can couple shield top  120  and shield bottom  122  to form shield  901 . In one embodiment, to separate shield system  914  from excess portions of matrix  104 , lines can be scored around the perimeter of shield system  914 . In another embodiment, shield system  914  can be separated from excess portions of matrix  914  with a laser or any other similar approach. 
       FIG. 9B  shows a side view of assembly  900 . Integrated circuit  102  is embedded in matrix  104  and effectively surrounded by shield  901 . As shown, shield  901  can include shield top  120 , shield bottom  122  and edge plating  912  as applied through routed areas  910 . Pads  934  can couple signals to integrated circuit  102 .  FIG. 9B  also shows excess portions of matrix  104  beyond shield  901 . These portions of matrix  104  can be removed prior to mounting shield system  914  onto a circuit board, for example. Other embodiments can include different integrated circuit  102  heights and different shield system  914  heights. In one embodiment, shield  914  can share a signal, such as a ground signal with integrated circuit  102 . This arrangement was described earlier in conjunction with  FIG. 1 . In another embodiment, shield  914  can be isolated from signals used by integrated circuit  102  and be coupled to an independent signal such as chassis ground. This arrangement was described earlier in conjunction with  FIG. 3 . 
       FIG. 9C  illustrates a side view of assembly  900  of  FIGS. 9A and 9   b  after excess portions of matrix  104  are removed. Any suitable method can be used to remove excess portions of matrix  104 . In one embodiment, a router is used to route the excess portions of matrix  104  away from the shield system  914 . In another embodiment, excess portion of matrix  104  are scored near the shield system  914  and subsequently broken off. In other embodiments, a laser cutting device is used to cut away excess portion of matrix  104 . After excess portions of matrix  104  are removed, shield system  914  can be mounted onto a circuit board  940 , for example. Circuit board  940  can be a printed circuit board, flex circuit or other suitable structure. Solder balls  942  can be aligned with pads  934  such that signals can be coupled from circuit board  940  to integrated circuit  102 . 
       FIG. 10  illustrates another embodiment of a low profile shield assembly  1000 . In this embodiment, shield system  1014  can include integrated circuit  102  embedded in matrix  104 . In contrast to shield system  914  in  FIG. 9 , corners of shield system  1014  can be chamfered  1006  at 45 degrees. Chamfers  1006  can help increase the amount of other components that can be mounted on a circuit board along side shield system  1014 . Chamfers  1006  can be formed as a later step after integrated circuit  102  is embedded in matrix  104  and after shield  901  is formed and attached. In one embodiment, chamfers  1006  can be formed by a router. In another embodiment, chamfers  1006  can be formed by scoring matrix  104  to enable easy separation. In still another embodiment, chamfers  1006  can be formed by a laser cutting device. 
     Pads  934  are on the far side of shield system  1014  (as in  FIG. 9A ) and are shown here with dashed lines. A pin A 1  indicator  1008  can be applied to the near side of shield system  1014  (and over pad A 1 ) and can help orient shield system  1014  for proper assembly onto a circuit board, for example. 
       FIG. 11  is a flow chart of method steps  1100  for forming shield system  914 . The method begins in step  1102  where integrated circuit  102  is obtained. In step  1104 , integrated circuit  102  is embedded in matrix  104 . In one embodiment, matrix  104  can be larger than the finished dimension of shield system  914 . Step  1104  can include the forming of routed areas  910  into matrix  104 . In step  1105  shield  901  can be formed to surround integrated circuit  102 . In one embodiment, shield  901  can include shield top  120 , shield bottom  122  and edge plating  912  applied through routed areas  910 . In step  1106  pads  934  can be attached to matrix  104  to couple signals to integrated circuit  102 . In one embodiment, laser vias can be formed to help couple signals from integrated circuit  102  to pads  934 . In step  1108 , a solder mask can be preferentially applied to shield top  120 . In one embodiment, portions of shield top  120  can be left without solder mask to enable attachment of a heat sink, heat pipe or other like thermal conducting device. In step  1110  excess matrix  104  can be removed. In one embodiment, excess matrix  104  can be the portion of matrix  104  that extends beyond the finished dimension of shield system  914 . 
     The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of specific embodiments are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the described embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings.

Metadata:
Filing Date: 20120823
Publication Date: 20150512
Grant Date: 20150512
Priority Date: 20120223
Inventors: ARNOLD SHAWN X.
MULLINS SCOTT P.
THOMA JEFFREY M.
CHANDHRASEKHAR RAMAMURTHY
Assignee: APPLE INC
CPC Classifications: [{"code": "H01L23/3107", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T29/49204", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L23/552", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01L23/3107", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/19105", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/04105", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L23/552", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01L2224/12105", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/04105", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L23/3107", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/12105", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/12105", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T29/49204", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/0401", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/0401", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/04105", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L23/552", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01L2223/6677", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/04105", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L23/3107", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/12105", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L23/552", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01L2924/19105", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/0401", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2223/6677", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 49002670