Reduction of Electromagnetic Interference in Integrated Circuit Device Packages

Abstract

EMI radiation in an integrated circuit device package ( 10 ) is reduced or eliminated by the introduction of a magnetic material into the encapsulating medium ( 14 ). The permeance of the magnetic encapsulating medium ( 14 ) affects the inherent series inductance of the lead frame conductors ( 16 ) to thereby reduce electromagnetic interference. Ferrite microbeads ( 30 ) are formed around the lead frame conductors ( 16 ) to contain the magnetic flux ( 32 ) generated by an electrical current signal and to attenuate the effects of mutual inductance.

1 . An integrated circuit comprising: 
 a wafer having circuitry disposed thereon;    a plurality of conductors coupled to the wafer;    a structure that encapsulates and supports the wafer; and magnetic material disposed to alter an inductance associated with at least one of the plurality of conductors.    
   
   
       2 . The integrated circuit of  claim 1 , wherein the magnetic material is at least partially disposed within the structure.  
   
   
       3 . The integrated circuit of  claim 1 , wherein the magnetic material is substantially homogeneously disposed throughout the structure.  
   
   
       4 . The integrated circuit of  claim 1 , wherein at least a portion of the magnetic material is disposed external to the structure.  
   
   
       5 . The integrated circuit of  claim 1 , wherein the magnetic material comprises a ferromagnetic material.  
   
   
       6 . The integrated circuit of  claim 1 , wherein the magnetic material comprises a ferrite material.  
   
   
       7 . The integrated circuit of  claim 1 , further comprising at least one choke structure formed of the magnetic material, wherein each chock structure associates with at least one respective conductor of the plurality of conductors.  
   
   
       8 . The integrated circuit of  claim 1 , wherein the magnetic material forms a plurality of choke structures, each of the choke structures being associated with at least one respective conductor of the plurality of conductors  
   
   
       9 . The integrated circuit of  claim 7 , wherein the structure comprises a dielectric material encapsulating at least a portion of the choke structures.  
   
   
       10 . The integrated circuit of  claim 7 , wherein at least some of the choke structures are disposed external to the structure.  
   
   
       11 . The method of reducing electromagnetic interference generated within an integrated circuit device package wherein the integrated circuit device package comprises 
 a wafer having wafer circuitry disposed thereon;    a plurality of conductors defining electrically conductive paths for carrying all of the electric current flowing to and from the wafer circuitry; and    a structure that encapsulates and supports the wafer; said method comprising applying magnetic material that exhibits a lossy characteristic, in the vicinity of at least one of the electrically conductive paths such that the magnetic material is not part of any of the electrically conductive paths for carrying all of the electric current flowing to and from the wafer circuitry, to attenuate the highest frequency signal components while introducing generally little inductance effects of overshoot and ringing associated with the series inductance of the at least one of the electrically conductive paths.    
   
   
       12 . The method of  claim 11 , wherein the structure that encapsulates and supports the wafer comprises an encapsulating medium, and said method further comprises introducing magnetic material that exhibits a lossy characteristic into the encapsulating medium such that the magnetic material is not part of any of the electrically conductive paths for carrying all of the electric current flowing to and from the wafer circuitry, so as to cause the series inductance of the at least one of the electrically conductive paths to behave as a lossy inductor so as to attenuate the highest frequency signal components while introducing generally little inductance effects of overshoot and ringing.  
   
   
       13 . The method of  claim 12 , wherein a relatively small amount of magnetic material that exhibits a lossy characteristic, is introduced into the encapsulating medium such that the magnetic material is not part of any of the electrically conductive paths for carrying all of the electric current flowing to and from the wafer circuitry, and so that the relative permeability in the vicinity of the at least one of the electrically conductive paths is not so high as to cause significant mutual coupling with other of the plurality of conductors.  
   
   
       14 . The method of  claim 13 , where the introduction of the relatively small amount of magnetic material that exhibits a lossy characteristic, such that the magnetic material is not part of any of the electrically conductive paths for carrying all of the electric current flowing to and from the wafer circuitry, results in a relative permeability of the encapsulating medium that is sufficient to desirably affect the series inductance of the at least one of the electrically conductive paths.  
   
   
       15 . The method of  claim 13 , where the mutual inductance between the one of the plurality of electrically conductive paths and an adjacent conductor is small with respect to the self-inductance of each conductor.  
   
   
       16 . The method of  claim 11 , wherein the magnetic material that is not part of any of the electrically conductive paths for carrying all of the electric current flowing to and from the wafer circuitry, is applied such that mutual coupling of the one of the plurality of electrically conductive paths and an adjacent conductor is substantially eliminated.  
   
   
       17 . The method of  claim 11 , where the magnetic material that exhibits a lossy characteristic and is not part of any of the electrically conductive paths for carrying all of the electric current flowing to and from the wafer circuitry, substantially surrounds the one of the plurality of the electrically conductive paths and effectively chokes undesired high frequency signals immediately external to the at least one of the electrically conductive paths without substantially affecting data signals passing therethrough.  
   
   
       18 . The method of  claim 17 , where the structure that encapsulates and supports the wafer comprises an encapsulating medium that is substantially free of magnetic material.  
   
   
       19 . The method of  claim 17 , where the structure that encapsulates and supports the wafer comprises an encapsulating medium that contains a small amount of magnetic material that is not part of any of the electrically conductive paths for carrying all of the electric current flowing to and from the wafer circuitry, to further achieve the reduction of electromagnetic interference.  
   
   
       20 . The method of  claim 17 , where the magnetic material that is not part of any of the electrically conductive paths for carrying all of the electric current flowing to and from the wafer circuitry, substantially surrounds the one of the plurality of electrically conductive paths, at the portion of such one electrically conductive path relatively near to the wafer.