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 flex circuit and a second flex circuit, each comprising a set of first flex contacts, a set of second flex contacts, a first conductive layer, a second conductive layer, and an intermediate layer between the first and second conductive layers;    a first CSP having contacts, the contacts of the first CSP being connected to the first flex contacts of each of the first and second flex circuits;    a second CSP having contacts, the first CSP being disposed above the second CSP and the contacts of the second CSP being connected to the second flex contacts of each of the first and second flex circuits; and    module contacts in contact with the second flex contacts.    
   
   
       2 . The high-density module of  claim 1  in which for at least the first flex circuit or the second flex circuit, the first conductive layer, the intermediate layer, and the second conductive layer are configured to provide distributed capacitance.  
   
   
       3 . The high-density circuit module of  claim 1  in which selected ones of the first flex contacts are connected to selected ones of the second flex contacts.  
   
   
       4 . The high-density circuit module of  claim 3  in which selected ones of the first flex contacts are connected to selected ones of the second flex contacts with traces.  
   
   
       5 . The high-density circuit module of  claim 4  in which selected ones of the traces have substantially equal signal lengths.  
   
   
       6 . The high-density circuit module of  claim 1  in which at least one of the contacts of the first CSP and at least one of the contacts of the second CSP are connected to the first conductive layer of the first flex circuit.  
   
   
       7 . The high-density circuit module of  claim 6  in which at least one of the contacts of the first CSP or at least one of the contacts of the second CSP is connected to the first conductive layer of the first flex circuit with an on-pad via.  
   
   
       8 . The high-density circuit module of  claim 6  in which at least one of the contacts of the first CSP or at least one of the contacts of the second CSP is connected to the first conductive layer of the first flex circuit with an off-pad via.  
   
   
       9 . The high-density circuit module of  claim 1  in which the first conductive layer and the second conductive layers of the first flex circuit and the second flex circuit are metal.  
   
   
       10 . The high-density circuit module of  claim 9  in which the metal of the first conductive layer and the second conductive layers is alloy 110.  
   
   
       11 . A module comprising a lower CSP and an upper CSP, each of the CSPs having a top surface and a bottom surface, and each of the CSPs having a first lateral side and a second lateral side, the module comprising: 
 a first flex circuit partially wrapped about the first lateral side of the lower CSP, the first flex circuit having a first plurality of upper flex contacts and a first plurality of lower flex contacts; and    a second flex circuit partially wrapped about the second lateral side of the lower CSP, the second flex circuit having a second plurality of upper flex contacts and a second plurality of lower flex contacts, the first plurality of upper flex contacts and the second plurality of upper flex contacts configured to connect the first flex circuit and the second flex circuit, respectively, to the upper CSP, and the first plurality of lower flex contacts and the second plurality of lower flex contacts configured to connect the first flex circuit and the second flex circuit, respectively, to the lower CSP.    
   
   
       12 . The module of  claim 11  in which the first flex circuit and the second flex circuit each have an upper conductive layer and a lower conductive layer, each having at least one electrical path connecting a selected one of the plurality of upper flex contacts to a selected one of the plurality of lower flex contacts.  
   
   
       13 . The high-density circuit module of  claim 12  in which selected ones of the electrical paths comprise traces having substantially equal signal lengths.  
   
   
       14 . A high-density circuit module comprising: 
 a first CSP having CSP contacts;    a second CSP having CSP contacts and disposed in a stack with the first CSP;    a first flex circuit and a second flex circuit, each having 
 first and second conductive layers,  
 an intermediate layer between the first and second conductive layers,  
 first flex contacts in electrical connection with CSP contacts of the first CSP,  
 second flex contacts in electrical connection with CSP contacts of the second CSP, and  
 electrical paths of the first conductive layer or the second conductive layer, selected ones of the electrical paths connecting a selected one of the first flex contacts and a selected one of the second flex contacts; and  
   a plurality of module contacts connectable to an application platform, each one of the plurality of module contacts being in electrical connection to an electrical path of the first flex circuit, to an electrical path of the second flex circuit, or to one of the CSP contacts of the first CSP or the second CSP.    
   
   
       15 . The high-density circuit module of  claim 14  in which at least one of the first conductive layers comprises a ground plane.  
   
   
       16 . The high-density circuit module of  claim 14  in which at least one of the CSP contacts of the first CSP is connected to a first conductive layer and a plurality of the CSP contacts of the first CSP are connected to a second conductive layer.  
   
   
       17 . The high-density circuit module of  claim 14  in which, for at least the first flex circuit or the second flex circuit, the first conductive layer, the intermediate layer, and the second conductive layer are configured to provide distributed capacitance.  
   
   
       18 . The high-density circuit module of  claim 14  in which, for at least the first flex circuit or the second flex circuit, the second conductive layer comprises plural traces each connecting a selected one of the CSP contacts of the first CSP to a selected one of the CSP contacts of the second CSP.  
   
   
       19 . The high-density circuit module of  claim 18  in which selected ones of the traces have substantially equal signal lengths.  
   
   
       20 . The high-density circuit module of  claim 18  in which the second conductive layer further comprises a voltage plane.  
   
   
       21 . The high-density circuit module of  claim 14  in which thermally conductive material is disposed between the first CSP and the second CSP.  
   
   
       22 . The high-density circuit module of  claim 21  in which the thermally conductive material is a thermally conductive adhesive.  
   
   
       23 . A high-density circuit module comprising: 
 a first flex circuit comprising first flex contacts, second flex contacts, a first conductive layer, a second conductive layer having plural electrical paths, and an intermediate layer between the first conductive layer and the second conductive layer;    a second flex circuit comprising first flex contacts and second flex contacts;    a first CSP having contacts, selected contacts of the first CSP being connected to selected first flex contacts of each of the first and second flex circuits;    a second CSP having contacts, the first CSP being disposed above the second CSP and selected contacts of the second CSP being connected to selected second flex contacts of each of the first and second flex circuits;    module contacts; and    a plurality of electrical connections each connecting one of the contacts of the first CSP to one of the module contacts.    
   
   
       24 . The high-density circuit module of  claim 23  in which the plurality of electrical connections comprises at least three electrical connections, at least one of which transits a portion of the first conductive layer and at least two of which each transits the second conductive layer along one of the electrical paths of the second conductive layer.  
   
   
       25 . The high-density circuit module of  claim 23  in which the first conductive layer has a ground plane and the second conductive layer has a voltage plane.  
   
   
       26 . The high-density circuit module of  claim 23  in which selected ones of the electrical paths of the second conductive layer have substantially equal signal length.  
   
   
       27 . The high-density circuit module of  claim 26  in which the first conductive layer has a ground plane and the second conductive layer has a voltage plane.  
   
   
       28 . The high-density circuit module of  claim 23  in which thermally conductive material is disposed between the first CSP and the second CSP.  
   
   
       29 . The high-density circuit module of  claim 28  in which the thermally conductive material is a thermally conductive adhesive.