Methods and systems for attaching die in stacked-die packages

Abstract

A method for producing a multiple-die device by attaching a die to a substrate using a first die-attach material having a first processing temperature and attaching a subsequent die using a second die-attach material having a second processing temperature such that the process of attaching the second die does not degrade the first die-attach material. For one embodiment, multiple dies are attached using each die-attach material. For one embodiment, the first die-attach material is a thermoplastic film and the second and subsequent die-attach materials are reformulations of the thermoplastic film.

1 - 17 . (canceled)  
     
     
         18 . A method comprising: 
 selecting a first die-attach material having a first associated processing temperature;    attaching a first set of one or more dies to a substrate and to one another using the first die-attach material;    selecting a second die-attach material having a second associated processing temperature, the second associated processing temperature being lower than the first associated processing temperature such that subjecting the first die-attach material to the second associated processing temperature does not degrade the first die-attach material to within a specified degree; and    attaching a second set of one or more dies to the first set of one or more dies and to one another using the second die-attach material.    
     
     
         19 . The method of  claim 18  wherein the first die-attach material comprises a first thermoplastic film and the second die-attach material comprises a second thermoplastic film.  
     
     
         20 . The method of  claim 19  wherein the first thermoplastic film has a first glass transition temperature and the second thermoplastic film has a second glass transition temperature that is lower than the first glass transition temperature.  
     
     
         21 . The method of  claim 18  further comprising: 
 attaching one or more additional sets of one or more dies successively upon the second set of one or more dies, each of the one or more additional sets of one or more dies being attached to a previous set of one or more dies and to one another using a different respective die-attach material.    
     
     
         22 . The method of  claim 18  wherein the first die-attach material comprises a thermoplastic film and the second die-attach material comprises a reformulation of the thermoplastic film, the reformulation of the thermoplastic film being effected by adding a plasticizer to the thermoplastic film.  
     
     
         23 . The method of  claim 22  wherein the plasticizer is selected from the group consisting of low molecular weight polyimides, amine terminated rubbers and low molecular weight epoxies.  
     
     
         24 . The method of  claim 18  wherein the first die-attach material comprises a first paste-based adhesive and the second die-attach material comprises a second paste-based adhesive.  
     
     
         25 . The method of  claim 18  wherein the first die-attach material comprises a first epoxy and the second die-attach material comprises a second epoxy.  
     
     
         26 - 30 . (canceled)