Photocurable adhesive compositions, reaction products of which have low halide ion content

Abstract

The present invention is directed to a photocurable composition for use as an encapsulant, for underfill or attachment adhesives, capable of curing at wavelengths greater than 290 nm. Reaction products of these photocurable compositions have a low level of extractable halide ion, such as less than 100 ppm. In use, the photocurable composition may be applied, for instance, over the wire bonds that electrically connect a semiconductor device to a substrate to maintain a fixed positional relationship and protect the integrity of the electrical connection from vibrational and shock disturbances, as well as from interference from environmental contaminants.

1 . A photocurable composition curable under exposure to radiation in the electromagnetic spectrum, reaction products of which have a low level of extractable halide ion, comprising: 
 (i) an epoxy resin component,    (ii) optionally, a photosensitizer, and    (iii) a cationic photoinitiator, the counter ion of which includes at least one halide atom bound covalently to a carbon atom of the counter ion.    
     
     
         2 . The composition according to  claim 1 , further comprising an adhesion promoter.  
     
     
         3 . The composition according to  claim 1 , wherein the composition is capable of curing through a volume of at least about 1 mm.  
     
     
         4 . The composition according to  claim 1 , wherein the composition is capable of curing radiation at a wavelength of at least 290 nm  
     
     
         5 . The composition according to  claim 1 , further comprising an inorganic filler component.  
     
     
         6 . The composition according to  claim 1 , wherein the the low level of extractable halide ion is less than 100 ppm.  
     
     
         7 . The composition according to  claim 1 , wherein the composition is capable of curing in a time of less than about 15 seconds.  
     
     
         8 . The composition according to  claim 1 , wherein the epoxy resin component is a member selected from the group consisting of cycloalphatic epoxy resins; C 4 -C 28  alkyl glycidyl ethers; C 2 -C 28  alkyl- and alkenyl-glycidyl esters; C 1 -C 28  alkyl-, mono- and poly-phenol glycidyl ethers; polyglycidyl ethers of pyrocatechol, resorcinol, hydroquinone, 4,4′-dihydroxydiphenyl methane, 4,4′-dihydroxy-3,3′-dimethyldiphenyl methane, 4,4′-dihydroxydiphenyl dimethyl methane, 4,4′-dihydroxydiphenyl methyl methane, 4,4′-dihydroxydiphenyl cyclohexane, 4,4′-dihydroxy-3,3′-dimethyldiphenyl propane, 4,4′-dihydroxydiphenyl sulfone, and tris(4-hydroxyphyenyl)methane; polyglycidyl ethers of the chlorination and bromination products of the above-mentioned diphenols; polyglycidyl ethers of novolacs; polyglycidyl ethers of diphenols obtained by esterifying ethers of diphenols obtained by esterifying salts of an aromatic hydrocarboxylic acid with a dihaloalkane or dihalogen dialkyl ether; polyglycidyl ethers of polyphenols obtained by condensing phenols and long-chain halogen paraffins containing at least two halogen atoms; phenol novolac epoxy resins; cresol novolac epoxy resins; and combinations thereof.  
     
     
         9 . The composition according to  claim 1  wherein the epoxy resin component is a cycloalphatic epoxy resin, bisphenol A epoxy resin, bisphenol F epoxy resin and combinations thereof.  
     
     
         10 . The composition according to  claim 1 , wherein the epoxy resin component is used in an amount of up to about 98 percent by weight of the total composition.  
     
     
         11 . The composition according to  claim 1 , wherein the photosensitizer is selected from the group consisting of thioxanthones, anthracene, perylene, phenothazine, 1,2 benzathracene, coronene, pyrene, tetracene and combinations threof.  
     
     
         12 . The composition according to  claim 1 , wherein the photosensitizer is a thioxanthone.  
     
     
         13 . The composition according to  claim 1 , wherein the photosensitizer is used in an amount within the range of about 0.01 to 1 percent by weight.  
     
     
         14 . The composition according to  claim 1 , wherein the cationic photoinitiator includes a cationic counter ion within the following structure:  
       
         
           
           
               
               
           
         
       
       wherein R 1 , R 2 , R 3,  R 4 , R 5  and R 5′  may or may not be present, but when not present are hydrogen and when any are present may individually be selected from C 1-6  alkyl, C 2-6  alkenyl, halogen, hydroxyl and carboxyl, with R 1 , R 2 , R 5  and R 5′  being present individually up to 5 times on each aromatic ring to which it(they) is(are) attached, and R 3  and R 4  being present individually up to 4 times on each aromatic ring to which it(they) is(are) attached, n is 0-3 and m is 0-1.  
     
     
         15 . The composition according to  claim 1 , wherein the cationic photoinitiator includes a counter ion selected from the group consisting of  
       
         
           
           
               
               
           
         
       
     
     
         16 . The composition according to  claim 1 , wherein the cationic photoinitiator includes a counter ion selected from the group consisting of  
       
         
           
           
               
               
           
         
       
       wherein for structure IV R 6 , R 7 , R 8 , R 9  and R 10  may or may not be present, but when not present are hydrogen and when any are present may individually be selected from alkyl of from 1 to 5 carbon atoms, halogen, hydroxyl, and carboxyl, for of structure V R 6 , R 7 , R 8 , R 9 , R 10 , R 6′ , R 7′ , R 8′ , R 9′ , and R 10′  may or may not be present, but when not present are hydrogen and when any are present may individually be selected from alkyl of from 1 to 5 carbon atoms, halogen, hydroxyl, and carboxyl, and for structure VI R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , R 20 , and R 21  may or may not be present, but when not present are hydrogen and when any are present may individually be selected from alkyl of from 1 to 5 carbon atoms, halogen, hydroxyl, and carboxyl.  
     
     
         17 . The composition according to  claim 1 , wherein the cationic photoinitiator includes a counter ion selected from the group consisting of  
       
         
           
           
               
               
           
         
       
     
     
         18 . The composition according to  claim 1 , wherein cationic photoinitiator is used in an amount within the range of about 0.1 to about 2 percent by weight of the total composition.  
     
     
         19 . The composition according to  claim 1 , wherein the counter ion of the cationic photoinitiator are halogenated tetraphenyl borates.  
     
     
         20 . The composition according to  claim 1 , wherein the counter ion of the cationic photoinitiator is pentafluorotetraphenyl borate.  
     
     
         21 . A smart card module assembly, comprising: 
 a carrier substrate dimensioned to receive a die;    a die having two surfaces, a first of which having bond pads disposed thereon and a second of which dimensioned for placement on the carrier substrate, wherein the second surface of the die is disposed on the carrier substrate so that the bond pads on the first surface of the die are in a position relative to the bond pads on the carrier substrate to make electrical connection therewith by way of the wire connectors;    a plurality of bond pads, some of which being positioned on one surface of the die and others of which being positioned on the carrier substrate;    a plurality of wire connectors; and    a composition according to  claim 1 , wherein the second surface of the die is disposed on the carrier substrate so that the bond pads on the first surface of the die are in a position relative to the bond pads on the carrier substrate to make electrical connection therewith by way of the wire connectors, and wherein the composition is disposed over at least a portion of the smart card module assembly so as to cover the wire bond connections established.    
     
     
         22 . A smart card comprising: 
 a plastic card; and    a smart card module assembly of  claim 21  having been exposed to radiation in the electromagnetic radiation at a wavelength of at least 290 nm, encased in the plastic card.    
     
     
         23 . (canceled)