Integrated circuit stacking system and method

Abstract

The present invention stacks integrated circuits (ICs) into modules that conserve PWB or other board surface area. In another aspect, the invention provides a lower capacitance memory expansion addressing system and method and preferably with the CSP stacked modules provided herein. In a preferred embodiment in accordance with the invention, a form standard provides a physical form that allows many of the varying package sizes found in the broad family of CSP packages to be used to advantage while employing a standard connective flex circuitry design. In a preferred embodiment, the form standard will be devised of heat transference material such as copper to improve thermal performance. In an alternative embodiment, the form standard may include a heat spreader portion with mounting feet. In a preferred embodiment of the memory addressing system, a high speed switching system selects a data line associated with each level of a stacked module to reduce the loading effect upon data signals in memory access.

1 . A method of making a high-density circuit module comprising the steps of: 
 (a) providing a form standard having a first radiating form portion, a second radiating form portion, and a heat spreader form portion;    (b) providing a flex circuit having first and second sets of flex contacts;    (c) providing a first CSP and a second CSP each having a top surface;    (d) connecting the first CSP and second CSP to the first and second sets of flex contacts, respectively;    (e) attaching the first radiating form portion of the form standard to the flex circuit, the first radiating form portion extending at least partially around the first CSP;    (f) attaching the second radiating form portion of the form standard to the flex circuit, the second radiating form portion extending at least partially around the second CSP;    (g) attaching the heat spreader form portion of the form standard to the top surface of the first CSP such that at least one thermal mount of the heat spreader form portion reaches downward, relative to the top surface of the first CSP, outside of a lateral extent of the first CSP;    (h) folding the flex circuit at an area between the first and second CSPs such that the flex circuit is folded around form curves on the first and second radiating form portions, and such that the second CSP is placed in an inverted, stacked position above the first CSP and thereby contacts the heat spreader form portion on a side of the heat spreader form portion opposite from a side adjacent to the first CSP.    
     
     
         2 . The method of  claim 1  in which the at least one thermal mount extends downward, relative to the top surface of the first CSP, to a level beside a plurality of module contacts on a side of the flex circuit opposite the first CSP.  
     
     
         3 . The method of  claim 1  further including the steps of: 
 (a) packaging the high-density circuit module in a hermetically sealed container;  
 (b) soldering the high-density circuit module to a circuit board;  
 (c) bonding the at least one thermal mount to the circuit board with a thermally conductive bonding means.  
 
     
     
         4 . The method of  claim 1  further including the steps of: 
 (a) soldering the high density circuit module onto a circuit board;  
 (b) bonding the at least one thermal mount to the circuit board with a thermally conductive bonding means.  
 
     
     
         5 . A method of assembling a high-density circuit module comprising the steps of: 
 (a) providing a flex circuit having first and second flex extensions and a central portion with a plurality of flex contacts arranged as a first set and a second set;    (b) providing first, second, and third CSPs;    (c) providing a form standard;    (c) connecting the first CSP to the first set flex contacts on the central portion of the flex circuit;    (d) placing the second CSP on the first flex extension;    (e) placing the third CSP on the second flex extension;    (f) folding the first and second flex extensions over first and second folded portions of the form standard.    
     
     
         6 . The method of  claim 5  further including the step of bonding the flex circuit to the form standard.  
     
     
         7 . The method of  claim 5  in which the step of providing a form standard includes assembling the form standard from at least two pieces.  
     
     
         8 . The method of  claim 5  in which the form standard has a means for radiating heat.  
     
     
         9 . The method of  claim 5  in which the form standard comprises fins.  
     
     
         10 . The method of  claim 5  in which the form standard comprises pins formed near at least one lateral edge of the form standard.  
     
     
         11 . The method of  claim 5  in which the form standard has heat conductive mounting feet.  
     
     
         12 . The method of  claim 5  in which the form standard has heat conductive thermal mounts.  
     
     
         13 . The method of  claim 5  in which the form standard has heat extensions for thermal connection of the high-density circuit element to its operating environment.  
     
     
         14 . The method of  claim 5  in which the form standard has mounting extensions for mechanically stabilizing the high-density circuit element in its operating environment.  
     
     
         15 . The method of  claim 14  in which the operating environment comprises a hermetically sealed package.  
     
     
         16 . A method of assembling a high-density circuit module comprising the steps of: 
 (a) providing a flex circuit having a plurality of flex contacts, the flex contacts being arranged into first and second sets;    (b) providing a form standard element;    (c) providing a first CSP and a second CSP each having a first and a second lateral edge delineating a lateral extent;    (d) connecting the first and second CSPs to the first and second sets of flex contacts, respectively;    (e) fitting the form standard element on the first CSP, the form standard element covering a portion of the first CSP and extending partially beyond the lateral extent of the first CSP;    (f) folding the flex circuit around a curved edge of the form standard element such that the second CSP is in contact with the form standard element on a side of the form standard element opposite from a side contacting the first CSP.    
     
     
         17 . The method of  claim 16  further including the steps of securing the form standard to the first CSP with an adhesive.  
     
     
         18 . The method of  claim 16  in which the form standard element is assembled from multiple pieces.  
     
     
         19 . The method of  claim 16  in which the form standard element has a means for radiating heat.  
     
     
         20 . The method of  claim 16  in which the form standard comprises fins.  
     
     
         21 . The method of  claim 16  in which the form standard comprises pins formed in a hollowed interior portion of the form standard element.  
     
     
         22 . The method of  claim 16  in which the form standard element has heat conductive mounting feet.  
     
     
         23 . The method of  claim 16  in which the form standard element has heat extensions for thermal connection of the high-density circuit element to its operating environment.  
     
     
         24 . The method of  claim 16  in which the form standard element has mounting extensions for fixing the high-density circuit element to an operating environment.  
     
     
         25 . The method of  claim 24  in which the operating environment comprises a hermetically sealed package.  
     
     
         26 . The method of  claim 16  further including the step of fixing the form standard element to a top major surface of the second CSP after the step of folding the flex circuit.