Die attach material for TBGA or flexible circuitry

Abstract

An attachment material is provided between the die and the solder balls of a TBGA or other flexible circuitry package that is sufficiently compliant to absorb pressure between the two, so as not to apply stress to the solder balls. The attachment material is also sufficiently rigid, with a low coefficient of thermal expansion (CTE), so that the material does not excessively expand and contract during thermal cycling relative to the die. More preferably, the attachment material has a CTE close to that of the die to prevent breakage of the tape at the junction between the tape and the die.

1 . An adhesive layer for use in an integrated circuit package for attaching a die to a solder ball array, the adhesive layer having: 
 a modulus of elasticity greater than about 100 ksi; and    a coefficient of thermal expansion of less than about 200 ppm/° C.    
     
     
         2 . The adhesive layer of  claim 1 , wherein the die is selected from the group consisting of microprocessors, co-processors, digital signal processors, graphics processors, microcontrollers, memory devices, reprogrammable devices, programmable logic devices, and logic arrays.  
     
     
         3 . The adhesive layer of  claim 1 , wherein the modulus of elasticity is less than about 126 ksi.  
     
     
         4 . The adhesive layer of  claim 1 , wherein the coefficient of thermal expansion is less than about 150 ppm/° C.  
     
     
         5 . The adhesive layer of  claim 4 , wherein the modulus of elasticity is less than about 126 ksi.  
     
     
         6 . The adhesive layer of  claim 4 , wherein the coefficient of thermal expansion is less than about 106 ppm/° C.  
     
     
         7 . The adhesive layer of  claim 6 , wherein the modulus of elasticity is less than about 126 ksi.  
     
     
         8 . The adhesive layer of  claim 6 , wherein the coefficient of thermal expansion is less than about 100 ppm/° C.  
     
     
         9 . The adhesive layer of  claim 8 , wherein the modulus of elasticity is less than about 126 ksi.  
     
     
         10 . An adhesive layer for use in an integrated circuit package for attaching a die to a solder ball array, the adhesive layer having: 
 a modulus of elasticity greater than about 10 ksi; and    a coefficient of thermal expansion of less than 100 ppm/° C.    
     
     
         11 . The adhesive layer of  claim 10 , wherein the modulus of elasticity is greater than about 50 ksi.  
     
     
         12 . The adhesive layer of  claim 10 , wherein the modulus of elasticity is greater than about 100 ksi.