Novel reworkable underfills for ceramic mcm c4 protection

Abstract

The present invention provides chip containing electronic devices such as Multichip Ceramic Modules (MCM's) containing a plurality of chips on a substrate which chips are underfilled with a reworkable composition which allows one or more chips to be removed from the device and replaced. The reworkable compositions contain a base resin which is not cross-linkable and which forms a matrix with a linear curable component or preferably a combination of linear curable components which curable components are cross-linkable and when cured form a cross-linked domain in the base resin matrix. A suitable cross-linking catalyst such as Pt is used and optionally a filler preferably silane surface treated silica. The preferred base resin is linear polydimethylsiloxane and the preferred curable components are vinyl terminated linear poly dimethyl siloxane and hydrogen terminated linear poly dimethyl siloxane.

1 . A reworkable underfill and dam composition for C4 joint protection comprising:
 a non-cross-linkable or low cross-linkable base resin containing no reactive groups;   at least one linear cross-linkable component;   a catalyst for the cross-linkable component; and   optionally a filler.   
   
   
       2 . The composition of  claim 1  wherein the base resin is linear polydimethyl siloxane. 
   
   
       3 . The composition of  claim 2  wherein the cross-linkable component is vinyl terminated linear siloxane or hydrogen terminated linear siloxane. 
   
   
       4 . The composition of  claim 3  wherein the cross-linkable component is both the vinyl terminated siloxane and the hydrogen terminated siloxane. 
   
   
       5 . The composition of  claim 4  wherein the catalyst is Pt in a cyclic vinyl siloxane. 
   
   
       6 . The composition of  claim 5  wherein the filler is silica. 
   
   
       7 . The composition of  claim 6  wherein the filler is silane surface treated silica. 
   
   
       8 . The composition of  claim 1  wherein the base resin is selected from the group consisting of polyurethane, mineral oil, polyacrylate, polyacrylic ester, CTBN modified ester, polystyrene, isoprene, epoxy modified siloxane, and mixtures thereof. 
   
   
       9 . The composition of  claim 8  wherein the cross-linkable component is selected from the group consisting of ester terminated, carbocyclic anhydride terminated, vinyl terminated linear or branched alkanes; acylic or acrylic ester; polyamide; polyimide and polyurethane. 
   
   
       10 . A method for underfilling and/or forming a dam for electronic components having C4 joints comprising the steps of:
 providing a chip containing an electronic component with C4 solder joints;   underfilling the joined chip and/or forming a dam around the chip with a reworkable underfill composition comprising:
 a non-cross-linkable or low cross-linkable base resin containing no reactive groups; 
 at least one linear cross-linkable component; 
 a catalyst for the cross-linkable component; and 
 optionally a filler; 
   curing the underfilled and/or dammed electronic component; and   reworking the underfilled MCM if necessary by removing the underfill composition and/or dam composition, separating the chip from the MCM and replacing the chip by joining a chip to the MCM and underfilling and damming the joined chip.   
   
   
       11 . The method of  claim 10  wherein the base resin is linear polydimethyl siloxane. 
   
   
       12 . The method of  claim 11  wherein the cross-linkable component is vinyl terminated linear siloxane or hydrogen terminated linear siloxane. 
   
   
       13 . The method of  claim 12  wherein the cross-linkable component is both the vinyl terminated siloxane and the hydrogen terminated siloxane. 
   
   
       14 . The method of  claim 13  wherein the catalyst is Pt in a cyclic vinyl siloxane. 
   
   
       15 . The method of  claim 14  wherein the filler is silica. 
   
   
       16 . The method of  claim 15  wherein the filler is silane surface treated silica. 
   
   
       17 . The method of  claim 10  wherein the base resin is selected from the group consisting of polyurethane mineral oil, polyacrylate, polyacrylic ester, CTBN modified ester, polystyrene/isoprene, epoxy modified siloxane, and mixtures thereof. 
   
   
       18 . The method of  claim 17  wherein the cross-linkable component is selected from the group consisting of ester terminated, carbocyclic anhydride terminated, vinyl terminated linear or branched alkanes; acylic or acrylic ester; polyamide; polyimide and polyurethane.