CA2068357C - Water-soluble flux for cored solder - Google Patents
Water-soluble flux for cored solderInfo
- Publication number
- CA2068357C CA2068357C CA 2068357 CA2068357A CA2068357C CA 2068357 C CA2068357 C CA 2068357C CA 2068357 CA2068357 CA 2068357 CA 2068357 A CA2068357 A CA 2068357A CA 2068357 C CA2068357 C CA 2068357C
- Authority
- CA
- Canada
- Prior art keywords
- flux
- solder
- cored
- citric acid
- water
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- 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
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/02—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape
- B23K35/0222—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape for use in soldering, brazing
- B23K35/0227—Rods, wires
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- 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
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
- B23K35/36—Selection of non-metallic compositions, e.g. coatings, fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest
- B23K35/3612—Selection of non-metallic compositions, e.g. coatings, fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest with organic compounds as principal constituents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- 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
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
- B23K35/36—Selection of non-metallic compositions, e.g. coatings, fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest
- B23K35/3612—Selection of non-metallic compositions, e.g. coatings, fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest with organic compounds as principal constituents
- B23K35/3618—Carboxylic acids or salts
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
- H05K3/32—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits
- H05K3/34—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by soldering
- H05K3/3457—Solder materials or compositions; Methods of application thereof
- H05K3/3478—Applying solder preforms; Transferring prefabricated solder patterns
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
- H05K2203/04—Soldering or other types of metallurgic bonding
- H05K2203/0415—Small preforms other than balls, e.g. discs, cylinders or pillars
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
- H05K3/32—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits
- H05K3/34—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by soldering
- H05K3/3447—Lead-in-hole components
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
- H05K3/32—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits
- H05K3/34—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by soldering
- H05K3/3489—Composition of fluxes; Methods of application thereof; Other methods of activating the contact surfaces
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Electric Connection Of Electric Components To Printed Circuits (AREA)
- Coating With Molten Metal (AREA)
Abstract
A non-toxic, non-corrosive water-soluble flux for cored solders comprises citric acid. The flux of the in-vention produces solder joints of high metallic luster and excellent quality. Clean-up of flux residues is accom-plished using only water.
Description
WATER-SOLUBLE FLUX FOR CORED SOLDER
TECHNICAL FIELD
The present invention relates to a novel water-soluble, environmentally-safe flux for cored solders, primarily useful in electronic industry soldering processes.
BACKGROUND ART
Most fluxes and defluxing chemicals used by industry to manufacture electronic circuits, such as military hard-ware, are either contributing to ozone depletion of the atmosphere or are considered by local environmental agencies, such as the Air Quality Management District in the Los Angeles basin, as environmental pollutants or health hazards. For example, it has been reported that if CFCs (chlorofluorohydrocarbons), which are used in vapor degreasing to clean soldered parts where a rosin flux is employed, are released to the atmosphere, they will remain there as an ozone depletant for nearly 100 years. other chemicals such as rosin fluxes, alcohols, and the like pose health risks and disposal problems for industry.
Water-soluble fluxes for cored solders are formulations that combine a soldering flux with a thickening agent maintained within a hollow tube of solder.
What is desired is a simple, non-toxic, non-corrosive, environmentally-safe solder flux for cored solders that produces solder joints of high metallic luster and excellent quality.
TECHNICAL FIELD
The present invention relates to a novel water-soluble, environmentally-safe flux for cored solders, primarily useful in electronic industry soldering processes.
BACKGROUND ART
Most fluxes and defluxing chemicals used by industry to manufacture electronic circuits, such as military hard-ware, are either contributing to ozone depletion of the atmosphere or are considered by local environmental agencies, such as the Air Quality Management District in the Los Angeles basin, as environmental pollutants or health hazards. For example, it has been reported that if CFCs (chlorofluorohydrocarbons), which are used in vapor degreasing to clean soldered parts where a rosin flux is employed, are released to the atmosphere, they will remain there as an ozone depletant for nearly 100 years. other chemicals such as rosin fluxes, alcohols, and the like pose health risks and disposal problems for industry.
Water-soluble fluxes for cored solders are formulations that combine a soldering flux with a thickening agent maintained within a hollow tube of solder.
What is desired is a simple, non-toxic, non-corrosive, environmentally-safe solder flux for cored solders that produces solder joints of high metallic luster and excellent quality.
DISCLOSURE OF INVENTION
In accordance with the invention, a water-soluble flux for cored solder is provided, comprising citric acid. The citric acid is co-extruded with a hollow cylinder of solder to form the composite cored solder.
The flux of the invention eliminates harmful environmental emissions normally associated with rosin-based fluxes, flux thinner (such as iso-~ropanol), and associated defluxing solvents (such as CFCs The flux of the invention is environmentally safe, non-toxic, and easy to use. Soldered assemblies can be cleaned in deionized water, thus eliminating the high capital costs associated with vapor degreasing equipment. The resulting soldered joint exhibits high metallic luster and excellent electrical quality.
Various aspects of the invention are defined as follows:
A composite cored solder comprising a hollow cylinder of a solder, said hollow filled with flux, said flux comprising citric acid.
A method of soldering a metal comprising applying to a surface thereof of a cored solder containing a flux therein and heating said metal to a desired soldering temperature, characterized in that said soldering flux comprises citric acid.
BEST MODES FOR CARRYING OUT THE INVENTION
The flux of the invention comprises citric acid.
Citric acid has a melting point of about 149 C. The inventors have found that in the liquidous state, citric acid can be co-extruded with any of the common tin-based solders.
Citric acid granules or crystals are heated to a liquid state (approximately 149 in a stainless steel container. The heated liquid citric acid is then poured into a pressurized heated extruding vat. As the solid solder wire is extruded into a hollow cored wire, the liquid citric acid is fed into the extruding chamber and then into the core. Air pressure inside the vat is preferably adjusted to assure void-free extrusion inside the core. The extruded, flux-filled solder wire is then wound on spools, labeled, and packaged for use.
Without subscribing to any particular theory, it appears that the citric acid chelates the oxide of the basis metal, but not the metal itself. As a result, there is little or no corrosion of the basis metal by the flux of the invention.
The grade or class of the citric acid is not critical in the practice of the invention. However, for extremely sensitive electrical circuits, it may be desirable to em-ploy a fairly high grade of citric acid.
The flux may contain other components, such as impuri-ties, whether accidental or deliberate, so long as such ad-ditives have no adverse effect on the soldering results.
Any of the common tin-based soldering alloys may be employed, including 60/40 Sn/Pb, 62/2/36 Sn/Ag/Pb, 63/37 Sn/Pb, and 96/4 Sn/Ag. Typically, 60/40 and 63/37 tin-lead solders are used.
The flux/cored solder is most advantageously employed in surface mounted and through hole mounted component sol-dering processes. The flux contains no volatile organic compounds (VOCs) or other evaporative solvents, such as iso-propyl alcohol. The water-soluble solder flux of the invention avoids the use of rosin-cored solders, which ne-cessitate the use of chlorofluorocarbon-type defluxing agents; rather, the flux of the invention is easily de-fluxed using deionized water.
The flux of the invention provides the following ad-vantages:
1. It eliminates harmful environmental emissions normally associated with rosin-cored fluxes, flux thinner (such as iso-propyl alcohol), and associated defluxing agents (such as 1,1,1-trichloroethane). Indeed, cleaning of the flux is simply done in warm or hot water. Thus, the new flux is environmentally safe.
2. It provides soldering personnel with a non-toxic, extremely safe, and highly effective flux/cored sol-der to use.
3. Its use provides solder joints that evidence a more lustrous connection with excellent wetting and an estimated 80% reduction in solder defects, compared with rosin-cored solders.
INDUSTRIAL APPLICABILITY
The flux/cored solder of the invention is expected to find use in commercial soldering operations, particularly in soldering electrical components in circuit boards.
EXAMPLE
Five electronic assembly personnel conducted a hand soldering operation comparing solder wire cored using Mil-Spec rosin flux to that employing citric acid. A total of 280 solder joints were made. The solder joints (connec-tions) involved the insertion of the leads of dual in-line packages (DIPs) into plated-through holes on printed wiring ~8~5~
boards. Following component (DIP) installation, each as-sembler performed the soldering/flux comparison using both types of flux cored solder. Following the evaluation, the five assemblers jointly concluded that the solder wire com-prising citric acid produced solder ~oints superior inquality and luster to those of rosin cored solder. Both types of solder wire were of the same solder composition, Sn 63/Pb 37.
Thus, there has been disclosed a non-toxic, non-cor-rosive, environmentally-safe, water-soluble flux for cored solders, suitable for use in soldering electrical compo-nents. It will be clear to those skilled in the art that various changes and modifications of an obvious nature may be made, and all such changes and modifications are consid-ered to fall within the scope of the invention, as defined by the appended claims.
In accordance with the invention, a water-soluble flux for cored solder is provided, comprising citric acid. The citric acid is co-extruded with a hollow cylinder of solder to form the composite cored solder.
The flux of the invention eliminates harmful environmental emissions normally associated with rosin-based fluxes, flux thinner (such as iso-~ropanol), and associated defluxing solvents (such as CFCs The flux of the invention is environmentally safe, non-toxic, and easy to use. Soldered assemblies can be cleaned in deionized water, thus eliminating the high capital costs associated with vapor degreasing equipment. The resulting soldered joint exhibits high metallic luster and excellent electrical quality.
Various aspects of the invention are defined as follows:
A composite cored solder comprising a hollow cylinder of a solder, said hollow filled with flux, said flux comprising citric acid.
A method of soldering a metal comprising applying to a surface thereof of a cored solder containing a flux therein and heating said metal to a desired soldering temperature, characterized in that said soldering flux comprises citric acid.
BEST MODES FOR CARRYING OUT THE INVENTION
The flux of the invention comprises citric acid.
Citric acid has a melting point of about 149 C. The inventors have found that in the liquidous state, citric acid can be co-extruded with any of the common tin-based solders.
Citric acid granules or crystals are heated to a liquid state (approximately 149 in a stainless steel container. The heated liquid citric acid is then poured into a pressurized heated extruding vat. As the solid solder wire is extruded into a hollow cored wire, the liquid citric acid is fed into the extruding chamber and then into the core. Air pressure inside the vat is preferably adjusted to assure void-free extrusion inside the core. The extruded, flux-filled solder wire is then wound on spools, labeled, and packaged for use.
Without subscribing to any particular theory, it appears that the citric acid chelates the oxide of the basis metal, but not the metal itself. As a result, there is little or no corrosion of the basis metal by the flux of the invention.
The grade or class of the citric acid is not critical in the practice of the invention. However, for extremely sensitive electrical circuits, it may be desirable to em-ploy a fairly high grade of citric acid.
The flux may contain other components, such as impuri-ties, whether accidental or deliberate, so long as such ad-ditives have no adverse effect on the soldering results.
Any of the common tin-based soldering alloys may be employed, including 60/40 Sn/Pb, 62/2/36 Sn/Ag/Pb, 63/37 Sn/Pb, and 96/4 Sn/Ag. Typically, 60/40 and 63/37 tin-lead solders are used.
The flux/cored solder is most advantageously employed in surface mounted and through hole mounted component sol-dering processes. The flux contains no volatile organic compounds (VOCs) or other evaporative solvents, such as iso-propyl alcohol. The water-soluble solder flux of the invention avoids the use of rosin-cored solders, which ne-cessitate the use of chlorofluorocarbon-type defluxing agents; rather, the flux of the invention is easily de-fluxed using deionized water.
The flux of the invention provides the following ad-vantages:
1. It eliminates harmful environmental emissions normally associated with rosin-cored fluxes, flux thinner (such as iso-propyl alcohol), and associated defluxing agents (such as 1,1,1-trichloroethane). Indeed, cleaning of the flux is simply done in warm or hot water. Thus, the new flux is environmentally safe.
2. It provides soldering personnel with a non-toxic, extremely safe, and highly effective flux/cored sol-der to use.
3. Its use provides solder joints that evidence a more lustrous connection with excellent wetting and an estimated 80% reduction in solder defects, compared with rosin-cored solders.
INDUSTRIAL APPLICABILITY
The flux/cored solder of the invention is expected to find use in commercial soldering operations, particularly in soldering electrical components in circuit boards.
EXAMPLE
Five electronic assembly personnel conducted a hand soldering operation comparing solder wire cored using Mil-Spec rosin flux to that employing citric acid. A total of 280 solder joints were made. The solder joints (connec-tions) involved the insertion of the leads of dual in-line packages (DIPs) into plated-through holes on printed wiring ~8~5~
boards. Following component (DIP) installation, each as-sembler performed the soldering/flux comparison using both types of flux cored solder. Following the evaluation, the five assemblers jointly concluded that the solder wire com-prising citric acid produced solder ~oints superior inquality and luster to those of rosin cored solder. Both types of solder wire were of the same solder composition, Sn 63/Pb 37.
Thus, there has been disclosed a non-toxic, non-cor-rosive, environmentally-safe, water-soluble flux for cored solders, suitable for use in soldering electrical compo-nents. It will be clear to those skilled in the art that various changes and modifications of an obvious nature may be made, and all such changes and modifications are consid-ered to fall within the scope of the invention, as defined by the appended claims.
Claims (6)
1. A composite cored solder comprising a hollow cylin-der of solder, said hollow filled with flux, said flux com-prising citric acid.
2. The flux composition of Claim 1 wherein said solder consists essentially of a tin-based solder.
3. The flux composition of Claim 2 wherein said solder consists essentially of a tin-lead solder.
4. A method of soldering a metal comprising applying to a surface thereof a cored solder containing a flux therein and heating said metal to a desired soldering tem-perature, characterized in that said soldering flux com-prises citric acid.
5. The method of Claim 4 wherein said solder consists essentially of a tin-based solder.
6. The method of Claim 5 wherein said solder consists essentially of a tin-lead solder.
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US523,765 | 1990-05-15 | ||
| US07523765 US5085365B1 (en) | 1990-05-15 | 1990-05-15 | Water soluble soldering flux |
| US60720090A | 1990-10-31 | 1990-10-31 | |
| US607,200 | 1990-10-31 | ||
| US708,961 | 1991-05-31 | ||
| US07/708,961 US5192360A (en) | 1990-05-15 | 1991-05-31 | Water-soluble flux for cored solder |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2068357A1 CA2068357A1 (en) | 1992-12-01 |
| CA2068357C true CA2068357C (en) | 1995-03-14 |
Family
ID=27414878
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2068357 Expired - Fee Related CA2068357C (en) | 1990-05-15 | 1992-05-11 | Water-soluble flux for cored solder |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2068357C (en) |
-
1992
- 1992-05-11 CA CA 2068357 patent/CA2068357C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2068357A1 (en) | 1992-12-01 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |