Stacking system and method

Abstract

The present invention stacks integrated circuits into modules that conserve board surface area. In a two-high stack or module devised in accordance with a preferred embodiment of the present invention, a pair of integrated circuits is stacked, with one integrated circuit above the other. The two integrated circuits are connected with a pair of flexible circuit structures. Each of the pair of flexible circuit structures is partially wrapped about a respective opposite lateral edge of the lower integrated circuit of the module. The flex circuit pair connects the upper and lower integrated circuits and provides a thermal and electrical path connection path between the module and an application environment such as a printed wiring board (PWB). The present invention may be employed to advantage in numerous configurations and combinations of integrated circuits in modules provided for high-density memories or high capacity computing.

1 . A high-density circuit module comprising: 
 a first CSP having a major surface and a first plurality of CSP contacts along the major surface;    a second CSP having a major surface and a second plurality of CSP contacts along the major surface, the first CSP and the second CSP being disposed in a stacked configuration;    a flex circuit comprising 
 a first conductive layer having first conductive areas, each electrically connected to a selected one of the first plurality of CSP contacts, and second conductive areas, each electrically connected to a selected one of the second plurality of CSP contacts  
 a second conductive layer having third conductive areas, each electrically connected to a selected one of the first plurality of CSP contacts, and fourth conductive areas, each electrically connected to a selected one of the second plurality of CSP contacts, and  
 an intermediate layer between the first conductive layer and the second conductive layer; and  
   module contacts, at least one of which is electrically connected to one of the first conductive areas, and at least one of which is electrically connected to one of the third conductive areas.    
   
   
       2 . The high-density circuit module of  claim 1  in which at least one of the module contacts is electrically connected to one of the fourth conductive areas.  
   
   
       3 . The high-density circuit module of  claim 1  in which the first conductive layer comprises a ground plane.  
   
   
       4 . The high-density circuit module of  claim 1  in which a first selected one of the first plurality of CSP contacts is electrically connected through the first conductive layer to at least one of the second plurality of CSP contacts, and in which a second selected one of the first plurality of CSP contacts is connected through the second conductive layer to at least one of the second plurality of CSP contacts.  
   
   
       5 . The high-density circuit module of  claim 1  in which the first conductive layer, the intermediate layer, and the second conductive layer are configured to provide distributed capacitance.  
   
   
       6 . The high-density circuit module of  claim 1  in which the second conductive layer comprises electrical paths each connecting a selected one of the CSP contacts of the first plurality of CSP contacts to a selected one of the CSP contacts of the second plurality of CSP contacts.  
   
   
       7 . The high-density circuit module of  claim 6  in which selected ones of the plurality of the electrical paths have substantially equal signal lengths.  
   
   
       8 . The high-density circuit module of  claim 6  in which the second conductive layer further comprises a voltage plane.  
   
   
       9 . The high-density circuit module of  claim 1  in which thermally conductive material is disposed between the first CSP and the second CSP.  
   
   
       10 . The high-density circuit module of  claim 9  in which the thermally conductive material is a thermally conductive adhesive.  
   
   
       11 . A high-density circuit module comprising: 
 a first CSP stacked with a second CSP, the first CSP having an outline perimeter and a major surface with a first plurality of CSP contacts, and the second CSP having a major surface with a second plurality of CSP contacts; and    a flex circuit having a first conductive layer, a second conductive layer, a first portion having a first plurality of flex contacts connected to selected ones of the first plurality of CSP contacts, a second portion having a second plurality of flex contacts connected to selected ones of the second plurality of CSP contacts, and a third portion having a bend disposed outside the outline perimeter of the first CSP and adjacent to the stack formed by the first CSP and the second CSP.    
   
   
       12 . The high-density circuit module of  claim 11  further comprising module contacts disposed along the first portion or the second portion of the flex circuit.  
   
   
       13 . The high-density circuit module of  claim 11  in which the first conductive layer comprises a ground plane.  
   
   
       14 . The high-density circuit module of  claim 11  in which a first selected one of the first plurality of CSP contacts is electrically connected through the first conductive layer to at least one of the second plurality of CSP contacts, and in which a second selected one of the first plurality of CSP contacts is connected through the second conductive layer to at least one of the second plurality of CSP contacts.  
   
   
       15 . The high-density circuit module of  claim 11  in which the second conductive layer comprises electrical paths each connecting a selected one of the CSP contacts of the first plurality of CSP contacts to a selected one of the CSP contacts of the second plurality of CSP contacts.  
   
   
       16 . The high-density circuit module of  claim 15  in which the second conductive layer further comprises a voltage plane and selected ones of the electrical paths comprise traces.  
   
   
       17 . The high-density circuit module of  claim 15  in which selected ones of the electrical paths have substantially equal signal lengths.  
   
   
       18 . The high-density circuit module of  claim 17  in which the second conductive layer further comprises a voltage plane and selected ones of the electrical paths comprise traces.  
   
   
       19 . The high-density circuit module of  claim 11  in which thermally conductive material is disposed between the first CSP and the second CSP.  
   
   
       20 . The high-density circuit module of  claim 19  in which the thermally conductive material is a thermally conductive adhesive.  
   
   
       21 . A high-density circuit module component comprising: 
 a CSP having a first major surface, a second major surface, an outline perimeter, and CSP contacts along at least the first major surface or the second major surface;    a flex circuit having a plurality of conductive layers, a first generally planar portion proximal to at least a portion of the first major surface of the CSP, a second generally planar portion proximal to at least a portion of the second major surface of the CSP, and a bend outside the outline perimeter of the CSP;    flex contacts disposed along the second generally planar portion of the flex circuit; and    module contacts disposed along the first generally planar portion of the flex circuit.    
   
   
       22 . The high-density circuit module component of  claim 21  in which the flex contacts are connectable with CSP contacts of another CSP.  
   
   
       23 . The high-density circuit module component of  claim 21  in which one of the conductive layers comprises a ground plane.  
   
   
       24 . The high-density circuit module component of  claim 23  in which one of the flex contacts is connected to the ground plane by a via.  
   
   
       25 . The high-density circuit module component of  claim 24  in which the via is on-pad.  
   
   
       26 . The high-density circuit module component of  claim 24  in which the via is off-pad.  
   
   
       27 . The high-density circuit module component of  claim 21  in which the flex circuit comprises plural primary traces each connecting a selected one of the CSP contacts to a selected one of the flex contacts.  
   
   
       28 . The high-density circuit module component of  claim 27  in which selected ones of the primary traces have substantially equal signal lengths.  
   
   
       29 . The high-density circuit module component of  claim 27  in which the flex circuit further comprises at least one secondary trace connecting a selected one of the module contacts only to one or more of the CSP contacts.  
   
   
       30 . The high-density circuit module component of  claim 27  in which the flex circuit further comprises at least one secondary trace connecting a selected one of the module contacts only to one or more of the flex contacts.  
   
   
       31 . The high-density circuit module component of  claim 30  in which the flex circuit further comprises at least one tertiary trace connecting a selected one of the module contacts only to one or more of the CSP contacts.  
   
   
       32 . A high-density circuit module comprising: 
 a stack comprising a first CSP having a major surface along which a first plurality of CSP contacts is disposed and a second CSP having a major surface along which a second plurality of CSP contacts is disposed;    a flex circuit having a plurality of conductive layers, a first generally planar portion disposed adjacent to at least a portion of the major surface of the first CSP, a second generally planar portion disposed adjacent to at least a portion of the major surface of the second CSP, and a folded portion disposed adjacent to the stack;    sets of flex contacts, respectively comprising a first plurality of flex contacts, a second plurality of flex contacts, and a third plurality of flex contacts;    a plurality of module contacts;    conductive connections between ones of the first plurality of CSP contacts and ones of the first plurality of flex contacts;    conductive connections between ones of the second plurality of CSP contacts and ones of the second plurality of flex contacts; and    conductive connections between ones of the plurality of module contacts and ones of the third plurality of flex contacts.    
   
   
       33 . The high-density circuit module of  claim 32  in which a first of the conductive levels comprises a ground plane.  
   
   
       34 . The high-density circuit module of  claim 33  in which a second of the conductive levels has plural electrical paths, each between a selected one of the contacts of the first plurality of CSP contacts and a selected one of the contacts of the second plurality of CSP contacts.  
   
   
       35 . The high-density circuit module of  claim 34  in which the second conductive layer comprises a voltage plane, and the electrical paths comprise traces.  
   
   
       36 . The high-density circuit module of  claim 34  in which selected ones of the electrical paths have substantially equal signal lengths.  
   
   
       37 . The high-density circuit module of  claim 36  in which the second conductive layer comprises a voltage plane, and the electrical paths comprise traces.  
   
   
       38 . The high-density circuit module of  claim 32  in which a first selected one of the first plurality of CSP contacts is electrically connected through a first one of the conductive layers to at least one of the second plurality of CSP contacts, and in which a second selected one of the first plurality of CSP contacts is connected through a second one of the conductive layers to at least one of the second plurality of CSP contacts.  
   
   
       39 . The high-density circuit module of  claim 32  in which thermally conductive material is disposed between the first CSP and the second CSP.  
   
   
       40 . The high-density circuit module of  claim 39  in which the thermally conductive material is a thermally conductive adhesive.