Method of integrated circuit assembly

Abstract

A method of integrated circuit assembly before encapsulation including at least one step of soldering, under mechanical pressure, a first element on a second element, including temporarily maintaining a predetermined spacing, at least partially without solder paste, between the surfaces to be assembled of the first and second elements.

What is claimed is:  
     
         1 . A method of integrated circuit assembly before encapsulation including at least one step of soldering under mechanical pressure a first element on a second element, including temporarily maintaining a predetermined spacing, at least partially without solder paste, between the surfaces to be assembled of the first and second elements.  
     
     
         2 . The method of    claim 1   , including using a solder paste comprising balls of a diameter greater than the individual diameter of other components of the deposited solder paste, to avoid filling the predetermined spacing defined by the ball diameter.  
     
     
         3 . The method of    claim 2   , wherein the balls have a diameter much greater than the final thickness desired for the soldering.  
     
     
         4 . The method of    claim 3   , wherein the ratio between the balls and the individual diameter of the other components is greater than 5, preferably on the order of 10.  
     
     
         5 . The method of    claim 3   , wherein the balls have a diameter ranging between 0.1 and 0.6 mm, preferably on the order of 0.4 mm.  
     
     
         6 . The method of    claim 2   , wherein the balls of greater diameter are formed of the same alloy as the other components of the solder paste.  
     
     
         7 . The method of    claim 2   , including successively performing the steps of: 
 depositing a layer of solder paste on the second element,    depositing the balls by means of needles at the tips of which they are maintained before dispense by solder paste.    
     
     
         8 . The method of    claim 7   , wherein the needle tips are dipped in the solder paste layer, then in a bed of balls before being dipped again in the paste layer where the balls remain by capillarity.  
     
     
         9 . The method of    claim 1   , wherein the first element is a ceramic pad and the second element is a metal heat sink.  
     
     
         10 . The method of    claim 1   , wherein the first element is a heat sink and the second element is a connection grid.