Modularized Die Stacking System and Method

Abstract

An IC die and a flexible circuit structure are integrated into a lower stack element that can be stacked with either further integrated lower stack element iterations or with pre-packaged ICs in any of a variety of package types. A die is positioned above the surface of portions of a pair of flex circuits. Connection is made between the die and the flex circuitry. A protective layer is formed to protect the flex-connected die and its connection to the flex. Connective elements are placed along the flex circuitry to create an array of module contacts along the second side of the flex circuitry. The flex circuitry is positioned above the body-protected die to create an integrated lower stack element. The integrated lower stack element may be stacked either with iterations of the integrated lower stack element or with a pre-packaged IC to create a multi-element stacked circuit module.

1 . A circuit module comprising: 
 an upper IC element;    an integrated lower stack element comprising: 
 an integrated circuit die;  
 first and second flex circuits, disposed adjacent to and connected with the integrated circuit die to create a die-flex combination; and  
 a protective structure molded to the die-flex combination to create a body having an upper surface above which are placed portions of the first and second flex circuits; and  
   the upper IC element and the integrated lower stack element being in stacked conjunction with the upper IC element being disposed above the integrated lower stack element and the upper IC element and integrated lower stack element being connected through the first and second flex circuits.    
   
   
       2 . The circuit module of  claim 1  in which the first and second flex circuits each have first and second conductive layers.  
   
   
       3 . The circuit module of  claim 2  in which the connection of the upper IC element and integrated lower stack element through the first and second flex circuits is implemented through interconnections articulated at the first and second conductive layers of the first and second flex circuits.  
   
   
       4 . The circuit module of  claim 2  in which at least one of the first and second conductive layers of the first and second flex circuits have demarked upper and lower flex contacts.  
   
   
       5 . An integrated lower stack element comprising: 
 an integrated circuit die;    first and second flex circuits, disposed adjacent to and connected with the integrated circuit die to create a die-flex combination; and    a protective structure molded to the die-flex combination to create a body having an upper surface above which are placed portions of the first and second flex circuits.    
   
   
       6 . The integrated lower stack element of  claim 5  in which the first and second flex circuits are connected with the integrated circuit die through wire bonds.  
   
   
       7 . The integrated lower stack element of  claim 5  in which the first and second flex circuits are connected with the integrated circuit die through flip-chip connections.  
   
   
       8 . The integrated lower stack element of  claim 5  further comprising a set of module contacts disposed along the first and second flex circuits.  
   
   
       9 . The integrated lower stack element of  claim 5  in which the first and second flex circuits each have first and second conductive layers.  
   
   
       10 . A circuit module comprising: 
 (a) an integrated lower stack element comprising; 
 an integrated circuit die having a plurality of die connective sites;  
 a flexible circuit having first and second conductive layers, the flexible circuit being disposed in part beneath and affixed to and connected with the integrated circuit die to form a die-flex combination; and  
 a protective structure set about the die-flex combination to cover at least a portion of the die and at least a portion of the flexible circuit and create a body having an upper surface above which are placed portions of the flexible circuit; and  
   (b) an upper IC element having a plurality of upper IC contacts, the upper IC element being disposed in stacked conjunction with the integrated lower stack element, the upper IC element and integrated lower stack element being connected through the flexible circuit.    
   
   
       11 . The circuit module of  claim 10  in which a data signal connection between the upper IC element and the integrated lower stack element is implemented at the second conductive layer of the flex circuit.  
   
   
       12 . The circuit module of  claim 10  in which a data signal connection between the upper IC element and the integrated lower stack element is implemented at the first conductive layer of the flex circuit.  
   
   
       13 . The circuit module of  claim 10  in which: 
 a data set of the plurality of upper IC contacts expresses an n-bit datapath;    a data set of the plurality of die connective sites expresses an n-bit datapath; and    a set of module contacts expresses a 2n-bit datapath that combines the n-bit datapath of the data set of the plurality of upper IC contacts and the n-bit datapath of the data set of the plurality of die connective sites.    
   
   
       14 . The circuit module of  claim 10  in which the second conductive layer comprises at least one demarked voltage plane and a voltage set of upper flex contacts and a voltage set of lower flex contacts that connect voltage conductive die connective sites and voltage conductive upper IC contacts to one of the at least one voltage planes.  
   
   
       15 . A flex circuit connecting an upper IC element and an integrated circuit die in a circuit module, the flex circuit comprising: 
 first and second outer layers; and    first and second conductive layers, between which there is an intermediate layer, the first and second conductive layers and the intermediate layer being interior to the first and second outer layers, the second conductive layer having demarked first and second flex contacts, the first flex contacts being accessible through first windows through the second outer layer and the second flex contacts being accessible through second windows through the first outer layer, the first conductive layer, and the intermediate layer, the first flex contacts in electrical connection with the upper IC element and the second flex contacts in electrical connection with the integrated circuit die;    wherein the flex circuit is disposed in part beneath and is combined with the integrated circuit die to form a die-flex combination and wherein a protective structure is set about the die-flex combination to cover at least a portion of the die and at least a portion of the flex circuit, the protective structure having an upper surface above which are placed portions of the flex circuit.    
   
   
       16 . The flex circuit of  claim 15  in which the second flex contacts are accessible through module windows through the second outer layer.  
   
   
       17 . The flex circuit of  claim 15  in which the first and second conductive layers are metal.  
   
   
       18 . The flex circuit of  claim 15  in which selected ones of the first flex contacts are connected to selected ones of the second flex contacts.  
   
   
       19 . The flex circuit of  claim 15  in which selected ones of the first flex contacts and selected ones of the second flex contacts are connected to the first conductive layer.  
   
   
       20 . The flex circuit of  claim 17  in which the metal of the first and second conductive layers is alloy 110.  
   
   
       21 . The flex circuit of  claim 18  in which the connected selected ones of the first and second flex contacts are connected with traces.  
   
   
       22 . The flex circuit of  claim 15  in which selected ones of the first flex contacts and selected ones of the second flex contacts are connected to the first conductive layer with vias.  
   
   
       23 . A circuit module that employs the flex circuit of  claim 15  to connect selected die contacts of an integrated circuit die to selected contacts of an upper IC element.  
   
   
       24 . A circuit module comprising: 
 a first flex circuit devised in accordance with  claim 15;     a second flex circuit devised in accordance with  claim 15;     an integrated circuit die having a plurality of die connective sites, a set of the plurality of die connective sites of the integrated circuit die being in electrical communication with the first flex contacts of each of the first and second flex circuits;    an upper IC element having a plurality of upper IC contacts, a set of the plurality of upper IC contacts of the upper IC element being in electrical communication with the second flex contacts of each of the first and second flex circuits; and    a set of module contacts in electrical communication with the second flex contacts.    
   
   
       25 . The circuit module of  claim 24  in which the first and second flex circuits are connected through an inter-flex circuit connective.  
   
   
       26 . A circuit module comprising: 
 a first flex circuit devised in accordance with  claim 15;     a second flex circuit devised in accordance with  claim 15;     an integrated circuit having a plurality of die connective sites, a set of the plurality of die connective sites, the die contacts of the integrated being in electrical communication with the second flex contacts of each of the first and second flex circuits;    an upper IC element having a plurality of upper IC contacts, a set of the plurality of upper IC contacts of the upper IC element being in electrical communication with the first flex contacts of each of the first and second flex circuits; and    a set of module contacts in electrical communication with the first flex contacts.    
   
   
       27 . The circuit module of claims  24  or  26  in which for the first and second flex circuits, the first conductive layer conveys ground, and the second conductive layer conveys voltage in a voltage plane and the intermediate layer is insulative to create a distributed capacitor in the first and second flex circuits.  
   
   
       28 . A circuit module comprising: 
 a first CSP having first and second lateral sides and upper and lower major surfaces and a set of CSP contacts along the lower major surface;    an integrated circuit die having a set of die connective sites connected to a pair of flex circuits;    each of which pair of flex circuits having a first conductive layer and a second conductive layer, both said conductive layers being interior to first and second outer layers, and demarcated at the second conductive layer of each flex circuit there being upper and lower flex contacts, the upper flex contacts being connected to the set of CSP contacts of the first CSP and the lower flex contacts being connected to the die connective sites of the integrated circuit die and a set of module contacts.    
   
   
       29 . The circuit module of  claim 28  in which: 
 a chip-enable module contact is connected to an enable lower flex contact that is connected to a chip select CSP contact of the first CSP.    
   
   
       30 . The circuit module of  claim 29  in which the connection between the enable lower flex contact and the chip select CSP contact of the first CSP is through an enable connection at the first conductive layer.  
   
   
       31 . The circuit module of  claim 28  in which a body having first and second lateral sides and an upper major surface is set about the integrated circuit die and a first one of the flex circuit pair is partially wrapped about the first lateral side of said body and a second one of the flex circuit pair is partially wrapped about the second lateral side of said body to dispose the upper flex contacts above the upper major surface of said body and beneath the lower major surface of the first CSP.  
   
   
       32 . The circuit module of  claim 31  in which the first CSP expresses an n-bit datapath and the integrated circuit die expresses an n-bit datapath, each of the flex circuits of the flex circuit pair having supplemental lower flex contacts which, in combination with the lower flex contacts, provide connection for the set of module contacts and a set of supplemental module contacts to express a 2n-bit module datapath that combines the n-bit datapath expressed by the first CSP and the n-bit datapath expressed by the integrated circuit die.  
   
   
       33 . A circuit module comprising: 
 a first CSP having first and second major surfaces with a plurality of CSP contacts along the first major surface;    an integrated lower stack element in accordance with  claim 5 , the first CSP being disposed above the integrated lower stack element;    each of the pair of flex circuits of the integrated lower stack element having an outer layer and an inner layer and first and second conductive layers between which conductive layers there is an intermediate layer, the second conductive layer having demarked a plurality of upper and lower flex contacts and a voltage plane, a first set of said plurality of upper and lower flex contacts being connected to the voltage plane, a second set of said plurality of upper and lower flex contacts being connected to the first conductive layer, and a third set of said plurality of upper and lower flex contacts being comprised of selected ones of upper flex contacts that are connected to corresponding selected ones of lower flex contacts, the plurality of CSP contacts of the first CSP being in contact with the upper flex contacts; and    a set of module contacts in contact with the lower flex contacts.    
   
   
       34 . The circuit module of  claim 33  in which the first CSP and the integrated circuit die of the integrated lower stack element are memory circuits.  
   
   
       35 . The circuit module of  claim 33  in which the second set of said plurality of upper and lower flex contacts is connected to the first conductive layer with vias that pass through the intermediate layer.  
   
   
       36 . The circuit module of  claim 35  in which the second set of said plurality of upper and lower flex contacts is comprised of upper flex contacts connected to the first conductive layer with on-pad vias.  
   
   
       37 . The circuit module of  claim 35  in which the second set of said plurality of upper and lower flex contacts is comprised of lower flex contacts connected to the first conductive layer with off-pad vias.  
   
   
       38 . The circuit module of  claim 1  mounted on a board.  
   
   
       39 . The circuit module of claims  33  or  34  in which between the first CSP and the integrated lower stack element there is a thermally conductive layer.  
   
   
       40 . A method for assembling a circuit module, the method comprising the steps of: 
 acquiring an integrated circuit die;    acquiring a flex circuit devised in accordance with  claim 15;     disposing an adhesive on a selected area of the first outer surface of the flex circuit;    adhering the flex circuit to the integrated circuit die;    forming a connection between the flex circuit and the integrated circuit die;    protecting the integrated circuit die and the connection formed between the flex circuit and the integrated circuit die with a protective layer to form a body;    disposing a portion of the flex circuit above the body;    acquiring a CSP;    connecting the CSP to the flex circuit.