Flux composition for solder, solder paste, and method of soldering

Abstract

Soldering flux compositions, solder pastes, and methods of soldering using the same are provided, that exhibit excellent wettability, give highly reliable solder joints, and have superior storage stability. The flux composition contains at least one compound having at least one blocked carboxyl group selected from the group including compound (X) obtained by reaction of a carboxylic acid compound and a vinyl ether compound, compound (Y) obtained by reaction of a carboxylic acid anhydride compound and a hydroxy vinyl ether compound, and compound (Z) obtained by reaction of an acid anhydride and a polyhydric alcohol, followed by addition polymerization with a divinyl ether compound, and the flux composition is non-curing.

What is claimed is:  
     
         1 . A soldering flux composition comprising at least one compound having at least one blocked carboxyl group selected from the group consisting of: 
 compound (X) obtained by reaction of a carboxylic acid compound and a vinyl ether compound;    compound (Y) obtained by reaction of a carboxylic acid anhydride compound and a hydroxy vinyl ether compound; and    compound (Z) obtained by reaction of an acid anhydride and a polyhydric alcohol, followed by addition polymerization with a divinyl ether compound;    wherein said soldering flux composition is non-curing.    
     
     
         2 . The composition of  claim 1 , wherein said compound (X) has an acid number of not larger than 5 mgKOH/g, said compound (Y) has an acid number of not larger than 20 mgKOH/g and a weight average molecular weight of 300 to 100000, and said compound (Z) has an acid number of not larger than 10 mgKOH/g and a weight average molecular weight of 500 to 500000.  
     
     
         3 . The composition of  claim 2 , wherein said compound (X) is at least one compound selected from the group consisting of compounds represented by the formulae (1) and (2), said compound (Y) is a compound represented by the formula (3), and said compound (Z) is a compound represented by the formula (4):  
       
         
           
           
               
               
           
         
       
       wherein in the formula (1), x is an integer of 1 to 6, A 1  stands for a carboxyl acid residue without —(COO—) x , and Z 1  stands for the formula (1-1) or (1-2):  
       
         
           
           
               
               
           
         
       
       wherein R 1 , R 2 , R 3 , R 5 , and R 6  each independently stands for a hydrogen atom or an organic group having 1 to 50 carbon atoms, R 4 , R 7 , and R 8  each independently stands for an organic group having 1 to 50 carbon atoms, and Y 1  and Y 2  each independently stands for an oxygen or sulfur atom; in the formula (2), A 2 stands for a carboxylic acid residue without —(COO—) m , Y 3  and Y 4  each independently stands for an oxygen or sulfur atom, R 9  stands for an organic group having 1 to 50 carbon atoms, m is an integer of 1 to 6, and n is an integer of 0 to 5;  
       
         
           
           
               
               
           
         
       
       wherein R 10  stands for a substituted or unsubstituted divalent aliphatic or aromatic group having 1 to 50 carbon atoms, R 11  stands for a divalent hydrocarbon group or glycol residue having 1 to 50 carbon atoms, Y 5  stands for an oxygen or sulfur atom, and s is an integer of 1 to 500;  
       
         
           
           
               
               
           
         
       
       wherein R 12 , R 13 , and R 14  each independently stands for a divalent organic residue, Y 6  stands for an oxygen or sulfur atom, and t is an integer of 1 to 500.  
     
     
         4 . The composition of  claim 1  further comprising at least one member selected from the group consisting of a latent heat catalyst, a photocatalyst, an activator, a thixotropic agent, an antioxidant, a rust preventive agent, and a solvent.  
     
     
         5 . The composition of  claim 1  further comprising a compound having one reactive functional group in a molecule capable of forming a chemical bond with a carboxyl group upon heating.  
     
     
         6 . A solder paste comprising a flux composition of  claim 1  and solder powder.  
     
     
         7 . A method of soldering comprising the steps of: 
 (A) providing a flux composition of  claim 1  on an electrode portion of a substrate;    (B) providing a solder bumped electronic component;    (C) placing said electronic component provided in step (B) on said substrate obtained in step (A); and    (D1) subjecting the substrate with the electronic component obtained in step (C) to reflow for mounting.    
     
     
         8 . A method of soldering comprising the steps of: 
 (A) providing a flux composition of  claim 1  on an electrode portion of a substrate; and    (D2) supplying solder onto the substrate with the flux composition obtained in step (A), by flowing or dipping.    
     
     
         9 . A method of soldering comprising the steps of: 
 (X) printing a solder paste of  claim 3  on an electrode portion of a substrate;    (Y) placing an electronic component on said substrate obtained in step (X); and    (Z) subjecting said substrate with the electronic component obtained in step (Y) to reflow for mounting.