Thermosetting soldering flux and soldering process

Abstract

A soldering flux suitable for soldering of small electronic components comprises 0.1-50 mass percent of an organic acid, 5-40 mass percent of a solvent, and 10-95 mass percent of a thermosetting resin (including a curing agent), which is preferably a bisphenol A epoxy resin and an acid anhydride or amine curing agent. This flux can be used to prepare a solder paste by mixing with solder powder. This soldering flux can secure an electronic component simultaneously by soldering and by the resin, simply by a soldering operation at a soldering temperature of at least 150° C., and cleaning after soldering is no longer necessary.

1 . A soldering flux comprising 0.1-70 mass percent of an organic acid, 5-40 mass percent of a solvent, and a total of 10-95 mass percent of a thermosetting resin and a curing agent, wherein during soldering of a component, the flux exhibits a function of securing the component by the thermosetting resin.  
     
     
         2 . A soldering flux as described in    claim 1    wherein the organic acid is one or more classes selected from the group consisting of rosins, carboxylic acids and carboxylic acid anhydrides.  
     
     
         3 . A soldering flux as described in    claim 2    wherein the organic acid contains a rosin as at least a portion thereof.  
     
     
         4 . A soldering flux as described in    claim 1    wherein the thermosetting resin is an epoxy resin.  
     
     
         5 . A soldering flux as described in    claim 4    wherein the thermosetting resin is a bisphenol A epoxy resin.  
     
     
         6 . A soldering flux as described in    claim 5    wherein the curing agent is one or more classes selected from the group consisting of carboxylic acid anhydrides and amines.  
     
     
         7 . A soldering flux as described in    claim 6    wherein the organic acid contains 0.1-50 mass percent of at least one class of organic acid other than a carboxylic acid anhydride.  
     
     
         8 . A soldering flux as described in    claim 1    further comprising 0.1-10 mass percent of a thixotropic agent.  
     
     
         9 . A soldering paste which is a mixture of a powder of a solder alloy having a melting point of at least 150° C. and the flux described in    claim 1   .  
     
     
         10 . A soldering paste as described in    claim 9    wherein the total amount of the thermosetting resin and the curing agent in the flux is 50-95 mass percent.  
     
     
         11 . A solder paste as described in    claim 9    wherein the thermosetting resin in the flux is an epoxy resin.  
     
     
         12 . A solder paste as described in    claim 9    wherein the flux further contains 0.1-10 mass percent of a thixotropic agent.  
     
     
         13 . A method for simultaneously achieving securing by solder and a resin in which a first member is soldered to a second member using the flux described in    claim 1    and solder.  
     
     
         14 . A method for simultaneously achieving securing by solder and a resin in which a first member is soldered to a second member using the solder paste described in    claim 9   .  
     
     
         15 . A method as described in    claim 13    wherein the first member is an electronic component and the second member is a substrate having a large number of electrodes and the soldering temperature is at least 150° C.  
     
     
         16 . A method as described in    claim 14    wherein the first member is an electronic component and the second member is a substrate having a large number of electrodes and the soldering temperature is at least 150° C.