Cleaning and drying of electronic assemblies

Abstract

Components, especially of an electronic or electrical type, are cleaned by contact with a flammable liquid organic solvent (21), especially an alcohol. The surface of the solvent is covered with a non-flammable highly fluorinated compound vapor blanket (26), which vapor may also be used to transfer heat to the organic solvent. Both highly fluorinated compound and organic solvent are condensed and re-cycled.

I claim: 
     
       1. A method of cleaning and drying components by contact with a hydrogen-containing flammable, liquid organic solvent in a container, wherein the solvent surface is covered by a vapour layer rich in a highly fluorinated organic compound, which transfers heat to the organic solvent, . .and.!. wherein the component to be cleaned is contacted with the liquid organic solvent, removed therefrom, vapour-rinsed or dried in the highly fluorinated compound-rich vapour layer and then removed from the cleaning environment, .Iadd.and further wherein said highly fluorinated organic compound comprises carbon and fluorine atoms, optionally including hydrogen, oxygen, or nitrogen, but lacking chlorine and bromine atoms, said highly fluorinated organic compound and said liquid organic solvent form immiscible liquid phases, and said vapour layer rich in the highly fluorinated organic compound is maintained above the surface of the solvent.Iaddend.. 
     
     
       2. The method according to claim 1, wherein the organic solvent is a lower aliphatic C 1  -C 5  alcohol. 
     
     
       3. The method according to claim 1, wherein the component is an electronic or electrical component and the highly fluorinated compound is selected from the group consisting of perfluoroalkanes, perfluoro-alicyclic compounds, perfluoro-amines and perfluoro-ethers. boiling between 30° and 100° C. 
     
     
       4. The method according to claim 3, wherein the highly fluorinated compound is a perfluoroalkyl- or perfluoropolyalkyl-cyclohexane. 
     
     
       5. The method according to claim 1, wherein the organic solvent contains a highly fluorinated compound up to the saturation solubility of that compound in the organic solvent. 
     
     
       6. The method according to claim 1, wherein the organic solvent layer contains water up to the azeotropic composition of the water/organic solvent system. .Iadd. 
     
     
       7.  The method according to claim 1, wherein the highly fluorinated compound has a boiling point between 100° C. and 250° C. .Iaddend..Iadd.8. The method according to claim 7, wherein said liquid organic solvent has a boiling point 50° C. greater than said highly fluorinated compound. .Iaddend..Iadd.9. The method according to claim 3, wherein said liquid organic solvent has a boiling point 50° C. greater than said highly fluorinated compound. .Iaddend..Iadd.10. The method according to claim 1, wherein the boiling point of said highly fluorinated compound is between 30° C. and 250° C. .Iaddend..Iadd.11. The method according to claim 1, wherein said transfer of heat to said organic solvent from said highly fluorinated compound is accomplished by bubbling heated highly fluorinated compound through said solvent. .Iaddend..Iadd.12. The method according to claim 1, wherein said transfer of heat to said organic solvent from said highly fluorinated compound is accomplished by the highly fluorinated compound vapor. .Iaddend..Iadd.13. The method according to claim 1, further comprising, prior to removing said component from the cleaning environment, a step of spray rinsing said component within the vapour layer. .Iaddend..Iadd.14. A method of cleaning and drying components by contact with a hydrogen-containing flammable, liquid organic solvent in a container, wherein the organic solvent is heated, wherein the solvent surface is covered by a vapour layer rich in a highly fluorinated organic compound, wherein the component to be cleaned is contacted with the liquid organic solvent removed therefrom, vapour-rinsed or dried in the highly fluorinated compound-rich vapour layer and then removed from the cleaning environment, and further wherein said highly fluorinated organic compound comprises carbon and fluorine atoms, optionally including hydrogen, oxygen, or nitrogen but lacking chlorine and bromine atoms, said highly fluorinated organic compound and said liquid organic solvent form immiscible liquid phases, and said vapour layer rich in the highly fluorinated organic compound is maintained above the surface of the 
     
     
        solvent. .Iaddend..Iadd.15.  The method according to claim 14, wherein said organic solvent is heated prior to contact with the component to be 
     
     
        cleaned with the solvent. .Iaddend..Iadd.16.  The method according to claim 14 wherein heat is provided to said container by an electrical element or a heating coil. .Iaddend..Iadd.17. The method according to claim 14, wherein said organic solvent is heated directly by said highly fluorinated organic compound. .Iaddend..Iadd.18. The method according to claim 14, further comprising, prior to removing said component from the cleaning environment, a step of spray rinsing said component within the vapour layer. .Iaddend.