# US 5,334,260 A · No-clean, low-residue, volatile organic compound free soldering flux and method of use > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,334,260 A - Document ID: US5334260A - Status: Granted - Kind: A - Application number: 08/014,201 - Filed: 1993-02-05 - Granted: 1994-08-02 - Earliest claimed: 1993-02-05 - Assignees: Litton Systems, Inc. - Inventors: Krystyna Stefanowski - Web page: https://patentgrep.com/patent/US5334260A ## CPC - B23K 35/3612: {with organic compounds as principal constituents} - B23K 35/3618: {Carboxylic acids or salts} - B23K: SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM ## Abstract A no-clean, low-residue, rosin-free foam flux solution is described which comprises a cosolvent system free of volatile organic compound solvents which is comprised of (i) at least about 90% by weight demineralized water based on total weight of the flux solution and (ii) from about 1% by weight to about 5% by weight based on total weight of the flux solution of a non-volatile organic solvent forming a cosolvent with said demineralized water, said nonvolatile organic solvent having a boiling point above about 190.degree. C. and a vapor pressure below 0.1 millimeters Hg at 25.degree. C.; a fluxing agent present in an amount from about 1% to about 4% by weight based on total weight of the soldering flux, said fluxing agent comprising at least two carboxylic acids selected from the group consisting of C.sub.2 -C.sub.10 dicarboxylic acids, monocarboxylic acids and hydroxy acids, said fluxing agent being present as solute in said cosolvents; and nonionic surfactant present in an amount of less than about 1% by weight based on total weight of soldering flux. ## Claims ### Claim 1 A no-clean, low-residue, rosin-free foam soldering flux solution comprising: a. at least about 95% by weight of a cosolvent system free of volatile organic compound solvents which is comprised of (i) at least about 90% by weight demineralized water based on total weight of the soldering flux solution and (ii) from about 1% by weight to about 5% by weight based on total weight of the soldering flux solution of a non-volatile organic solvent forming a cosolvent with said demineralized water, said nonvolatile organic solvent having a boiling point above about 190.degree. C. and a vapor pressure below 0.1 millimeters Hg at 25.degree. C.; b. from about 1% to about 4% by weight of fluxing agent consisting essentially of two or more carboxylic acids selected from the group consisting of C.sub.2 -C.sub.10 dicarboxylic acids, monocarboxylic acids and hydroxy acids, said fluxing agent being present as solute in said cosolvent system; and c. nonionic surfactant in an amount not exceeding about 1% by weight based on total weight of soldering flux solution. ### Claim 2 (depends on 1) The foam flux solution of claim 1 wherein a plurality of nonvolatile organic solvents are present in the cosolvent system. ### Claim 3 (depends on 1) The foam flux solution of claim 1 further comprising an anticorrosion agent present in an amount less than about 0.5% by weight based or total weight of the flux. ### Claim 4 (depends on 2) The foam flux solution of claim 2 further comprising an anticorrosion agent present in an amount less than about 0.5% by weight based or total weight of the flux. ### Claim 5 (depends on 1) The foam flux solution of claim 1 wherein fluxing agent is present in an amount by weight based on total weight of the soldering flux of from about 2% to about 3%. ### Claim 6 (depends on 2) The foam flux solution of claim 2 wherein fluxing agent is present in an amount by weight based on total weight of the soldering flux of from about 2% to about 3%. ### Claim 7 (depends on 3) The foam flux solution of claim 3 wherein fluxing agent is present in an amount by weight based on total weight of the soldering flux of from about 2% to about 3%. ### Claim 8 (depends on 4) The foam flux solution of claim 4 wherein fluxing agent is present in an amount by weight based on total weight of the soldering flux of from about 2% to about 3%. ### Claim 9 (depends on 1) The foam flux solution of claim 1 wherein the fluxing agent contains a plurality of C.sub.2 -C.sub.10 dicarboxylic acids. ### Claim 10 (depends on 2) The foam flux solution of claim 2 wherein the fluxing agent contains a plurality of C.sub.2 -C.sub.10 dicarboxylic acids. ### Claim 11 (depends on 3) The foam flux solution of claim 3 wherein the fluxing agent contains a plurality of C.sub.2 -C.sub.10 dicarboxylic acids. ### Claim 12 (depends on 4) The foam flux solution of claim 4 wherein the fluxing agent contains a plurality of C.sub.2 -C.sub.10 dicarboxylic acids. ### Claim 13 (depends on 1) A soldering process, characterized by applying on the surfaces intended for soldering, prior to the soldering, a foam flux solution according to claim 1 and preheating said surfaces to vaporize the deionized water solvent, followed by heating to the temperature required for soldering. ### Claim 14 (depends on 13) The process of claim 13 wherein the soldering surfaces are soldering surfaces of silver, copper, tin, or alloys thereof. ### Claim 15 (depends on 13) The process of claim 13 wherein the soldering surface is copper or an alloy of copper on a circuit board.