Stacked Module Systems and Methods

Abstract

The present invention stacks chip scale-packaged integrated circuits (CSPs) into modules that conserve PWB or other board surface area. In a preferred embodiment in accordance with the invention, a form standard associated with one or more CSPs 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 contacts of the lower CSP will be compressed before flex circuitry is attached to a combination of the CSP and a form standard to create lower profile contacts between CSP and the flex circuitry.

1 . A method for devising a high-density circuit module, the method comprising the steps of:
 providing a first CSP having a planar surface rising above which are contacts, the contacts each rising above the planar surface by a height H;   attaching a form standard to the first CSP to form a primary combination, the primary form standard wrapping about sides of the first CSP and having ends disposed beneath the planar surface;   reducing the height H for each said contact;   providing a flex circuit upon which are located, solder paste sites;   disposing the primary combination adjacent to the flex circuit to realize areas of contact between the solder paste sites and the contacts that rise above the planar surface of the first CSP;   attaching the substantially rigid form standard of the combination to the flex circuit to create a unit; and   selectively heating the areas of contact between the solder paste sites and the contacts to form connections between the first CSP and the flex circuit.   
   
   
       2 . The method of  claim 1  further comprising the step of disposing a second CSP above the unit and connecting the flex circuit to the second CSP. 
   
   
       3 . The method of  claim 2  in which the flex circuit comprises at least one conductive layer. 
   
   
       4 . The method of  claim 2  in which the flex circuit comprises two conductive layers.