Precoat composition for organic solderability preservative

Abstract

An improved method of enhancing the solderability of a copper surface comprising the steps of contacting one or more copper surfaces with a pretreatment composition comprising a dilute solution of an aliphatic carboxylic acid and an additive selected from the group consisting of amines and ammonia and thereafter contacting the one or more surfaces with an organic solderability preservative composition. The improved organic solderability preservative process of the invention forms a more uniform coating that has a better appearance and color.

1 . A method of enhancing the solderability of a copper surface comprising the steps of: 
 a) contacting the copper surface with a pretreatment composition comprising a solution of an aliphatic carboxylic acid and optionally, but preferably, an additive selected from the group consisting of amines and ammonia; and thereafter    b) contacting the one or more surfaces with an organic solderability preservative composition.    
     
     
         2 . A method according to  claim 1  wherein the organic solderability preservative composition comprises an aqueous solution of one or more materials selected from the group consisting of substituted or unsubstituted triazoles, substituted or unsubstituted imidazoles, substituted or unsubstituted benzimidazoles, substituted or unsubstituted benzotriazoles, and substituted or unsubstituted azoles.  
     
     
         3 . The method according to  claim 2 , wherein the aliphatic carboxylic acid is selected from the group consisting of carboxylic acids with from 5 to 9 carbons.  
     
     
         4 . The method according to  claim 3 , wherein the aliphatic carboxylic acid comprises heptanoic acid.  
     
     
         5 . The method according to  claim 2 , wherein the additive is used and comprises an amine which is selected from the group consisting of triethanolamine, dimethylamine, dipropylamine, diethanolamine, ammonia, and ethanolamine.  
     
     
         6 . The method according to  claim 5 , wherein the amine is triethanolamine.  
     
     
         7 . The method according to  claim 5 , wherein the aliphatic carboxylic acid and the amine are each present in the pretreatment composition at a concentration between about 1 to about 10 g/l.  
     
     
         8 . The method according to  claim 2 , wherein the pH of the pretreatment solution is between about 4.5 and about 9.5.  
     
     
         9 . The method according to  claim 8 , wherein the pH of the pretreatment solution is about 6.0.  
     
     
         10 . The method according to  claim 2 , wherein the pretreatment composition comprises the additive.  
     
     
         11 . The method according to  claim 2 , wherein a rinsing step is performed between the pretreatment step and the organic solderability preservative step.  
     
     
         12 . The method according to  claim 2 , wherein said step of contacting the electronic component with the pretreatment composition comprises immersing the electronic component in the pretreatment composition.  
     
     
         13 . The method according to  claim 12 , wherein the electronic component is immersed in the pretreatment composition for about 1 to about 5 minutes.  
     
     
         14 . The method according to  claim 1 , wherein the organic solderability preservative composition comprises at least one azole.  
     
     
         15 . The method according to  claim 14 , wherein the at least one azole is an imidazole.