Thermally enhanced stacked die package and fabrication method

Abstract

A substrate is provided. A first die is attached to the substrate. The first die is electrically connected to the substrate. A heat sink having an undercut around its periphery is attached to the first die. A second die is attached to the heat sink. The second die is electrically connected to the substrate, and the first die, the heat sink, and the second die are encapsulated.

1 . A method of assembling a semiconductor package with stacked dies comprising: 
 providing a substrate;    attaching a first die to the substrate;    electrically connecting the first die to the substrate;    attaching a heat sink having an undercut around its periphery overhanging bond pads over the first die;    attaching a second die to the heat sink;    electrically connecting the second die to the substrate; and    encapsulating the first die, the heat sink, and the second die.    
   
   
       2 . The method of assembling a semiconductor package with stacked dies as claimed in  claim 1  wherein: 
 electrically connecting the first die to the substrate uses a number of bonding wires; and    attaching a heat sink attaches a heat sink that extends laterally over the number of bonding wires.    
   
   
       3 . The method of assembling a semiconductor package with stacked dies as claimed in  claim 1  wherein attaching a heat sink attaches a heat sink that is electrically grounded.  
   
   
       4 . The method of assembling a semiconductor package with stacked dies as claimed in  claim 1  wherein attaching a heat sink attaches a heat sink that has an electrically conductive coating, further comprising: 
 connecting the second die to the electrically conductive coating; and    connecting the electrically conductive coating to a ground plane.    
   
   
       5 . The method of assembling a semiconductor package with stacked dies as claimed in  claim 1  wherein attaching a heat sink attaches a heat sink that extends laterally beyond the edges of the second die.  
   
   
       6 . A method of thermally enhancing a semiconductor package with a stack of dies comprising providing a heat sink having an undercut around its periphery between dies in the stack.  
   
   
       7 . The method of thermally enhancing a semiconductor package with a stack of dies as claimed in  claim 6  wherein: 
 providing a heat sink attaches a heat sink that extends laterally over the lower die to which the heat sink is attached.    
   
   
       8 . The method of thermally enhancing a semiconductor package with a stack of dies as claimed in  claim 6  wherein providing a heat sink attaches a heat sink that is electrically grounded.  
   
   
       9 . The method of thermally enhancing a semiconductor package with a stack of dies as claimed in  claim 6  wherein providing a heat sink attaches a heat sink that has an electrically conductive coating, further comprising: 
 connecting one of the dies in the stack of dies to the electrically conductive coating; and    connecting the electrically conductive coating to a ground plane.    
   
   
       10 . The method of thermally enhancing a semiconductor package with a stack of dies as claimed in  claim 6  wherein providing a heat sink attaches a heat sink between each adjoining pair of dies in the stack of dies.  
   
   
       11 . A semiconductor package with stacked dies comprising: 
 a substrate;    a first die attached to the substrate;    the first die being electrically connected to the substrate;    a heat sink having an undercut around its periphery attached to the first die;    a second die attached to the heat sink and electrically connected to the substrate; and    an encapsulant over the first die, the heat sink, and the second die.    
   
   
       12 . The semiconductor package with stacked dies as claimed in  claim 11  further comprising: 
 a number of bonding wires electrically connecting the first die to the substrate; and wherein:    the undercut of the heat sink extends laterally over the number of bonding wires.    
   
   
       13 . The semiconductor package with stacked dies as claimed in  claim 11  wherein the heat sink is electrically grounded.  
   
   
       14 . The semiconductor package with stacked dies as claimed in  claim 11  wherein: 
 the heat sink has an electrically conductive coating connected to a ground plane on the substrate; and    the second die is connected to the electrically conductive coating.    
   
   
       15 . The semiconductor package with stacked dies as claimed in  claim 11  wherein the undercut of the heat sink extends laterally beyond the edges of the second die.  
   
   
       16 . A thermally enhanced semiconductor package with a stack of dies comprising a heat sink having an undercut around its periphery between dies in the stack.  
   
   
       17 . The thermally enhanced semiconductor package with a stack of dies as claimed in  claim 16  wherein: 
 the undercut of the heat sink extends laterally over the die to which the heat sink is attached.    
   
   
       18 . The thermally enhanced semiconductor package with a stack of dies as claimed in  claim 16  wherein the heat sink is electrically grounded.  
   
   
       19 . The thermally enhanced semiconductor package with a stack of dies as claimed in  claim 16  wherein: 
 the heat sink has an electrically conductive coating;    one of the dies in the stack of dies is connected to the electrically conductive coating; and    the electrically conductive coating is connected to a ground plane.    
   
   
       20 . The thermally enhanced semiconductor package with a stack of dies as claimed in  claim 16  wherein a heat sink is positioned between each adjoining pair of dies in the stack of dies.