CA2053751C - Water-soluble soldering paste - Google Patents
Water-soluble soldering pasteInfo
- Publication number
- CA2053751C CA2053751C CA 2053751 CA2053751A CA2053751C CA 2053751 C CA2053751 C CA 2053751C CA 2053751 CA2053751 CA 2053751 CA 2053751 A CA2053751 A CA 2053751A CA 2053751 C CA2053751 C CA 2053751C
- Authority
- CA
- Canada
- Prior art keywords
- water
- oil
- acid
- paste composition
- paste
- 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
- 238000005476 soldering Methods 0.000 title abstract description 23
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims abstract description 45
- 229910000679 solder Inorganic materials 0.000 claims abstract description 35
- 230000004907 flux Effects 0.000 claims abstract description 30
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 15
- 150000007524 organic acids Chemical class 0.000 claims abstract description 14
- 239000002562 thickening agent Substances 0.000 claims abstract description 14
- 230000009974 thixotropic effect Effects 0.000 claims abstract description 11
- 229920002261 Corn starch Polymers 0.000 claims abstract description 6
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 6
- 239000008120 corn starch Substances 0.000 claims abstract description 6
- 125000002843 carboxylic acid group Chemical group 0.000 claims abstract description 5
- 239000000839 emulsion Substances 0.000 claims abstract description 4
- 235000015165 citric acid Nutrition 0.000 claims description 13
- 239000003921 oil Substances 0.000 claims description 13
- 235000019198 oils Nutrition 0.000 claims description 13
- 239000000203 mixture Substances 0.000 claims description 12
- 239000003205 fragrance Substances 0.000 claims description 6
- XNGIFLGASWRNHJ-UHFFFAOYSA-N phthalic acid Chemical compound OC(=O)C1=CC=CC=C1C(O)=O XNGIFLGASWRNHJ-UHFFFAOYSA-N 0.000 claims description 6
- KDYFGRWQOYBRFD-UHFFFAOYSA-N succinic acid Chemical compound OC(=O)CCC(O)=O KDYFGRWQOYBRFD-UHFFFAOYSA-N 0.000 claims description 5
- 239000000843 powder Substances 0.000 claims description 4
- BJEPYKJPYRNKOW-REOHCLBHSA-N (S)-malic acid Chemical compound OC(=O)[C@@H](O)CC(O)=O BJEPYKJPYRNKOW-REOHCLBHSA-N 0.000 claims description 3
- FEWJPZIEWOKRBE-JCYAYHJZSA-N Dextrotartaric acid Chemical compound OC(=O)[C@H](O)[C@@H](O)C(O)=O FEWJPZIEWOKRBE-JCYAYHJZSA-N 0.000 claims description 3
- WHUUTDBJXJRKMK-UHFFFAOYSA-N Glutamic acid Natural products OC(=O)C(N)CCC(O)=O WHUUTDBJXJRKMK-UHFFFAOYSA-N 0.000 claims description 3
- WHUUTDBJXJRKMK-VKHMYHEASA-N L-glutamic acid Chemical compound OC(=O)[C@@H](N)CCC(O)=O WHUUTDBJXJRKMK-VKHMYHEASA-N 0.000 claims description 3
- FEWJPZIEWOKRBE-UHFFFAOYSA-N Tartaric acid Natural products [H+].[H+].[O-]C(=O)C(O)C(O)C([O-])=O FEWJPZIEWOKRBE-UHFFFAOYSA-N 0.000 claims description 3
- BJEPYKJPYRNKOW-UHFFFAOYSA-N alpha-hydroxysuccinic acid Natural products OC(=O)C(O)CC(O)=O BJEPYKJPYRNKOW-UHFFFAOYSA-N 0.000 claims description 3
- 239000004220 glutamic acid Substances 0.000 claims description 3
- 235000013922 glutamic acid Nutrition 0.000 claims description 3
- 239000001630 malic acid Substances 0.000 claims description 3
- 235000011090 malic acid Nutrition 0.000 claims description 3
- OSWPMRLSEDHDFF-UHFFFAOYSA-N methyl salicylate Chemical compound COC(=O)C1=CC=CC=C1O OSWPMRLSEDHDFF-UHFFFAOYSA-N 0.000 claims description 3
- 235000002906 tartaric acid Nutrition 0.000 claims description 3
- 239000011975 tartaric acid Substances 0.000 claims description 3
- 239000009637 wintergreen oil Substances 0.000 claims description 3
- 244000151018 Maranta arundinacea Species 0.000 claims description 2
- 235000010804 Maranta arundinacea Nutrition 0.000 claims description 2
- 235000019482 Palm oil Nutrition 0.000 claims description 2
- 235000019483 Peanut oil Nutrition 0.000 claims description 2
- 235000012419 Thalia geniculata Nutrition 0.000 claims description 2
- 229940119170 jojoba wax Drugs 0.000 claims description 2
- 239000001525 mentha piperita l. herb oil Substances 0.000 claims description 2
- 239000002540 palm oil Substances 0.000 claims description 2
- 239000000312 peanut oil Substances 0.000 claims description 2
- 235000019477 peppermint oil Nutrition 0.000 claims description 2
- 229920001592 potato starch Polymers 0.000 claims description 2
- 239000001384 succinic acid Substances 0.000 claims description 2
- 235000003132 food thickener Nutrition 0.000 claims 2
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims 1
- 231100000252 nontoxic Toxicity 0.000 abstract description 6
- 230000003000 nontoxic effect Effects 0.000 abstract description 6
- 239000002932 luster Substances 0.000 abstract description 3
- 230000009972 noncorrosive effect Effects 0.000 abstract description 3
- 229960004106 citric acid Drugs 0.000 description 12
- RSWGJHLUYNHPMX-UHFFFAOYSA-N Abietic-Saeure Natural products C12CCC(C(C)C)=CC2=CCC2C1(C)CCCC2(C)C(O)=O RSWGJHLUYNHPMX-UHFFFAOYSA-N 0.000 description 7
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 7
- KHPCPRHQVVSZAH-HUOMCSJISA-N Rosin Natural products O(C/C=C/c1ccccc1)[C@H]1[C@H](O)[C@@H](O)[C@@H](O)[C@@H](CO)O1 KHPCPRHQVVSZAH-HUOMCSJISA-N 0.000 description 7
- KHPCPRHQVVSZAH-UHFFFAOYSA-N trans-cinnamyl beta-D-glucopyranoside Natural products OC1C(O)C(O)C(CO)OC1OCC=CC1=CC=CC=C1 KHPCPRHQVVSZAH-UHFFFAOYSA-N 0.000 description 7
- 229910045601 alloy Inorganic materials 0.000 description 4
- 239000000956 alloy Substances 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 239000012190 activator Substances 0.000 description 3
- 238000004140 cleaning Methods 0.000 description 3
- 239000008367 deionised water Substances 0.000 description 3
- 229910021641 deionized water Inorganic materials 0.000 description 3
- 230000007613 environmental effect Effects 0.000 description 3
- 229960004592 isopropanol Drugs 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 235000005985 organic acids Nutrition 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 2
- 150000001298 alcohols Chemical class 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 238000005238 degreasing Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- UOCLXMDMGBRAIB-UHFFFAOYSA-N 1,1,1-trichloroethane Chemical compound CC(Cl)(Cl)Cl UOCLXMDMGBRAIB-UHFFFAOYSA-N 0.000 description 1
- 235000019737 Animal fat Nutrition 0.000 description 1
- 206010013786 Dry skin Diseases 0.000 description 1
- 239000002202 Polyethylene glycol Substances 0.000 description 1
- 125000003118 aryl group Chemical group 0.000 description 1
- 230000000712 assembly Effects 0.000 description 1
- 238000000429 assembly Methods 0.000 description 1
- 239000012298 atmosphere Substances 0.000 description 1
- KDYFGRWQOYBRFD-NUQCWPJISA-N butanedioic acid Chemical compound O[14C](=O)CC[14C](O)=O KDYFGRWQOYBRFD-NUQCWPJISA-N 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000012153 distilled water Substances 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 235000013305 food Nutrition 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- 150000002334 glycols Chemical class 0.000 description 1
- 239000000383 hazardous chemical Substances 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 231100000206 health hazard Toxicity 0.000 description 1
- 230000005802 health problem Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000001683 mentha spicata herb oil Substances 0.000 description 1
- 231100000989 no adverse effect Toxicity 0.000 description 1
- 239000004014 plasticizer Substances 0.000 description 1
- 229920001223 polyethylene glycol Polymers 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 235000019721 spearmint oil Nutrition 0.000 description 1
- 239000003981 vehicle Substances 0.000 description 1
- 238000009736 wetting Methods 0.000 description 1
Landscapes
- Electric Connection Of Electric Components To Printed Circuits (AREA)
Abstract
A non-toxic, non-corrosive water-soluble soldering paste comprises at least about 80 wt% of particulate solder and the balance a thixotropic flux base having a viscosity of at least about 200,000 cp. The flux base comprises (a) a botanical oil, (b) an aqueous emulsion of a thickening agent, such as corn starch or an ethoxylated linear alcohol in water, and (c) an organic acid having at least two carboxylic acid groups, such as citric acid. The paste of the invention produces solder joints of high metallic luster and excellent quality. Clean-up of paste residues is accomplished using only water.
Description
WATER-SOLUBLE SOLDERING PASTE
TECHNICAL FIELD
The present invention relates to a novel soldering paste which contains an environmentally-safe flux used in surface mount component 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 at-A
TECHNICAL FIELD
The present invention relates to a novel soldering paste which contains an environmentally-safe flux used in surface mount component 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 at-A
mosphere or are considered by local environmental agencies, such as the Air Quality Management District in the Los An-geles basin, as environmental pollutants or health hazards.
For example, it has been reported that if CFCs (chlorofluo-rohydrocarbons), 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 could be the simple solution for this major problem. However, most water-soluble fluxes are formulated with harsh activators, such as hydrochloric acid and complex glycols, which create major cleaning and resi-due problems for the printed circuit board and the electri-cal circuitry thereon and which tend to severely corrode the metal being soldered or contaminate the dielectric, causing a tendency for electromigration. Other water-solu-ble fluxes are formulated with iso-propanol and/or plasti-cizers, which create disposal and health problems.
Water-soluble solder pastes are formulations that com-bine a soldering alloy, typically in powder form, with a water-soluble organic activator and a water-soluble organic vehicle; see, e.g., U.S. Patent 4,872,928. While citric acid is mentioned as an example of an organic acid that acts as an activator, the paste also includes other materi-als that are not environmentally desirable, such as poly-ethylene glycol.
What is desired is a simple, non-toxic, non-corrosive, environmentally-safe liquid soldering paste that produces solder joints of high metallic luster and excellent quali ty.
DISCLOSURE OF INVENTION
In accordance with the invention, a novel soldering paste is provided, comprising particulate solder alloy and a thixotropic flux base. The thixotropic flux base, itself also novel, comprises (a) a botanical oil, (b) a thickening agent, and (c) a water-soluble organic acid having at least two carboxylic acid groups.
Another aspect of this invention is as follows:
A water-soluble solder paste comprising:
(a) at least about 80 wto particulate solder; and (b) the balance a thixotropic flux base having a viscosity of at least about 200,000 cp and comprising (1) a botanical oil, (2) an aqueous emulsion of a thickening agent, and (3) a water-soluble organic acid having at least two carboxylic acid groups, said organic acid selected from the group consisting of citric acid, malic acid, tartaric acid, glutamic acid, phthalic acid, and succinic acid.
The paste of the invention eliminates harmful environmental emissions normally associated with rosin-based fluxes, flux thinner (such as iso-propanol), and associated defluxing solvents (such as CFCs). The paste of the invention is environmentally safe, non-toxic, and easy to use. Soldering time and defluxing (cleaning) time are both reduced significantly over those corresponding times required for rosin-based fluxes, for example. 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.
3a 2 p 5 3 7 5 1 BEST MODES FOR CARRYING OUT THE INVENTION
The soldering paste of the invention comprises partic-ulate solder alloy and a thixotropic flux base. The thixo-tropic flux base comprises (a) a botanical oil, (b) an aqueous emulsion of a thickening agent, and (c) a water-soluble organic acid having at least two carboxylic acid groups. Examples of suitable organic acids include citric acid, malic acid, tartaric acid, glutamic acid, phthalic acid, succinic acid, and the like.
However, the best results have been obtained with cit-ric acid, and while the class of organic acids indicated above is useful, the remainder of the description which follows is directed to the use of citric acid as a flux in solder pastes used in soldering components.
Without subscribing to any particular theory, it ap-pears that the citric acid chelates the oxide on the basis metal being soldered, but not the metal itself. As a re-sult, there is little or no corrosion of the basis metal by the flux of the invention. Thus, to the extent that members of the above class of organic acids behaves simi-larly to citric acid, then such members are also included within the ambit of the invention.
The particulate solder may comprise solder balls hav ing a mesh size and composition typically employed in sol der pastes. As an example, the solder balls may range from -325 to +400 mesh and preferably from -200 to +325 mesh, although larger mesh sizes may also be employed. Typical ly, the concentration of the particulate solder in the paste is about 80 to 90 wt%, the balance being the flux base.
The particulate solder may comprise any of the common ly employed soldering alloys, 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 solders are used.
As indicated above, the thixotropic base comprises ( a ) botanical oil, (b) thickening agent in water, and (c) the water-soluble organic acid. The thixotropic flux base may be combined with the particulate solder to form the solder paste of the invention. Alternatively, the thixotropic flux base may be formulated separately as a paste for use in soldering operations.
The thickening agent may comprise any of the thicken ers commonly used in food processing, such as corn starch, potato starch, lichen, arrowroot powder, and the like.
Ethoxylated linear alcohols may also serve as a thickener in the practice of the invention. The minimum viscosity of the flux base after adding the thickening agent must be at least 200,000 centipoise (cp) at room temperature for use in the practice of the invention. For corn starch, this requires a minimum of 170 g/2 concentration in water. When an ethoxylated linear alcohol is used, a ratio of at least 1:1 of alcohol to water is used.
Deionized water is advantageously employed in the practice of the invention, although for extremely sensitive electronic circuits, distilled water may be used.
For example, it has been reported that if CFCs (chlorofluo-rohydrocarbons), 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 could be the simple solution for this major problem. However, most water-soluble fluxes are formulated with harsh activators, such as hydrochloric acid and complex glycols, which create major cleaning and resi-due problems for the printed circuit board and the electri-cal circuitry thereon and which tend to severely corrode the metal being soldered or contaminate the dielectric, causing a tendency for electromigration. Other water-solu-ble fluxes are formulated with iso-propanol and/or plasti-cizers, which create disposal and health problems.
Water-soluble solder pastes are formulations that com-bine a soldering alloy, typically in powder form, with a water-soluble organic activator and a water-soluble organic vehicle; see, e.g., U.S. Patent 4,872,928. While citric acid is mentioned as an example of an organic acid that acts as an activator, the paste also includes other materi-als that are not environmentally desirable, such as poly-ethylene glycol.
What is desired is a simple, non-toxic, non-corrosive, environmentally-safe liquid soldering paste that produces solder joints of high metallic luster and excellent quali ty.
DISCLOSURE OF INVENTION
In accordance with the invention, a novel soldering paste is provided, comprising particulate solder alloy and a thixotropic flux base. The thixotropic flux base, itself also novel, comprises (a) a botanical oil, (b) a thickening agent, and (c) a water-soluble organic acid having at least two carboxylic acid groups.
Another aspect of this invention is as follows:
A water-soluble solder paste comprising:
(a) at least about 80 wto particulate solder; and (b) the balance a thixotropic flux base having a viscosity of at least about 200,000 cp and comprising (1) a botanical oil, (2) an aqueous emulsion of a thickening agent, and (3) a water-soluble organic acid having at least two carboxylic acid groups, said organic acid selected from the group consisting of citric acid, malic acid, tartaric acid, glutamic acid, phthalic acid, and succinic acid.
The paste of the invention eliminates harmful environmental emissions normally associated with rosin-based fluxes, flux thinner (such as iso-propanol), and associated defluxing solvents (such as CFCs). The paste of the invention is environmentally safe, non-toxic, and easy to use. Soldering time and defluxing (cleaning) time are both reduced significantly over those corresponding times required for rosin-based fluxes, for example. 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.
3a 2 p 5 3 7 5 1 BEST MODES FOR CARRYING OUT THE INVENTION
The soldering paste of the invention comprises partic-ulate solder alloy and a thixotropic flux base. The thixo-tropic flux base comprises (a) a botanical oil, (b) an aqueous emulsion of a thickening agent, and (c) a water-soluble organic acid having at least two carboxylic acid groups. Examples of suitable organic acids include citric acid, malic acid, tartaric acid, glutamic acid, phthalic acid, succinic acid, and the like.
However, the best results have been obtained with cit-ric acid, and while the class of organic acids indicated above is useful, the remainder of the description which follows is directed to the use of citric acid as a flux in solder pastes used in soldering components.
Without subscribing to any particular theory, it ap-pears that the citric acid chelates the oxide on the basis metal being soldered, but not the metal itself. As a re-sult, there is little or no corrosion of the basis metal by the flux of the invention. Thus, to the extent that members of the above class of organic acids behaves simi-larly to citric acid, then such members are also included within the ambit of the invention.
The particulate solder may comprise solder balls hav ing a mesh size and composition typically employed in sol der pastes. As an example, the solder balls may range from -325 to +400 mesh and preferably from -200 to +325 mesh, although larger mesh sizes may also be employed. Typical ly, the concentration of the particulate solder in the paste is about 80 to 90 wt%, the balance being the flux base.
The particulate solder may comprise any of the common ly employed soldering alloys, 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 solders are used.
As indicated above, the thixotropic base comprises ( a ) botanical oil, (b) thickening agent in water, and (c) the water-soluble organic acid. The thixotropic flux base may be combined with the particulate solder to form the solder paste of the invention. Alternatively, the thixotropic flux base may be formulated separately as a paste for use in soldering operations.
The thickening agent may comprise any of the thicken ers commonly used in food processing, such as corn starch, potato starch, lichen, arrowroot powder, and the like.
Ethoxylated linear alcohols may also serve as a thickener in the practice of the invention. The minimum viscosity of the flux base after adding the thickening agent must be at least 200,000 centipoise (cp) at room temperature for use in the practice of the invention. For corn starch, this requires a minimum of 170 g/2 concentration in water. When an ethoxylated linear alcohol is used, a ratio of at least 1:1 of alcohol to water is used.
Deionized water is advantageously employed in the practice of the invention, although for extremely sensitive electronic circuits, distilled water may be used.
The botanical oil serves to level the solder, minimize splattering during the soldering process, and prevent dry-ing of the paste. Examples of suitable botanical oils in-clude jojoba oil, palm oil, and peanut oil. A relatively small amount of oil is required, as shown below for the preferred composition. Animal fat oils do not clean up easily, and are to be avoided in the practice of the in-vention.
The concentration range of citric acid in the flux base must be sufficient to activate the board solder (it is not necessary to activate the particulate solder in the paste). The minimum concentration of citric acid accord ingly must be at least about 3 wt% and can range up to saturation of the flux base. If necessary, a non-toxic medium which ties up free water may be used with lower concentrations of citric acid.
The organic acid may be used in crystal or powder form. For extremely sensitive electrical circuits, it may be desirable to employ 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 .
An odorant may optionally be added. Examples of such an odorant, which is intended to be a pleasant aroma for the user, include wintergreen oil, spearmint oil, and pep permint oil. The concentration of the odorant is about 1 to 30 ppm.
An especially preferred composition consists essen-tially of the following:
about 80 to 90 wt% particulate solder (-200 to +325 mesh); and the balance the thixotropic flux base, consisting essentially of (1) about 1 to 5 wt% botanical oil;
( 2 ) about 47. 5 to 49 . 5 wt% thickening agent, such as 170 g/E of corn starch in water or 1:1 ethoxylated linear alcohol in water; and (3) about 47.5 to 49.5 wt% citric acid solution (3% to saturated).
As indicated above, about 1 to 30 ppm odorant, such as wintergreen oil, may be added to the paste for aromatic purposes.
The paste is most advantageously employed in surface mount component soldering processes. The water-soluble solder paste of the invention avoids the use of rosin-based solder pastes, which necessitate the use of chlorofluoro-carbon-type defluxing agents; rather, the paste of the in-vention is easily defluxed using deionized water.
The paste of the invention provides the following ad-vantages:
1. It eliminates harmful environmental emissions normally associated with rosin-based fluxes, flux thinner (such as iso-propyl alcohol), and associated defluxing agents (such as 1,1,1-trichloroethane). Indeed, cleaning of the paste is simply done in warm or hot water. Thus, the new paste is environmentally safe.
2. It provides soldering personnel with a non-toxic, extremely safe, and highly effective solder paste to use, 3. Its use cuts the actual soldering time by ap-proximately 50~. This enables soldering to proceed at a considerably higher rate than permitted by rosin-based sol-ders, thereby subjecting electronic components to the heat of the solder for a far shorter period of time.
4. 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-impregnated solder pastes.
INDUSTRIAL APPLICABILITY
The solder paste of the invention is expected to find use in commercial soldering operations, particularly in soldering electrical components in circuit boards.
Thus, there has been disclosed a non-toxic, non-cor-rosive, environmentally-safe, water-soluble soldering paste, suitable for use in soldering electrical components.
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 considered to fall within the scope of the invention, as defined by the appended claims.
The concentration range of citric acid in the flux base must be sufficient to activate the board solder (it is not necessary to activate the particulate solder in the paste). The minimum concentration of citric acid accord ingly must be at least about 3 wt% and can range up to saturation of the flux base. If necessary, a non-toxic medium which ties up free water may be used with lower concentrations of citric acid.
The organic acid may be used in crystal or powder form. For extremely sensitive electrical circuits, it may be desirable to employ 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 .
An odorant may optionally be added. Examples of such an odorant, which is intended to be a pleasant aroma for the user, include wintergreen oil, spearmint oil, and pep permint oil. The concentration of the odorant is about 1 to 30 ppm.
An especially preferred composition consists essen-tially of the following:
about 80 to 90 wt% particulate solder (-200 to +325 mesh); and the balance the thixotropic flux base, consisting essentially of (1) about 1 to 5 wt% botanical oil;
( 2 ) about 47. 5 to 49 . 5 wt% thickening agent, such as 170 g/E of corn starch in water or 1:1 ethoxylated linear alcohol in water; and (3) about 47.5 to 49.5 wt% citric acid solution (3% to saturated).
As indicated above, about 1 to 30 ppm odorant, such as wintergreen oil, may be added to the paste for aromatic purposes.
The paste is most advantageously employed in surface mount component soldering processes. The water-soluble solder paste of the invention avoids the use of rosin-based solder pastes, which necessitate the use of chlorofluoro-carbon-type defluxing agents; rather, the paste of the in-vention is easily defluxed using deionized water.
The paste of the invention provides the following ad-vantages:
1. It eliminates harmful environmental emissions normally associated with rosin-based fluxes, flux thinner (such as iso-propyl alcohol), and associated defluxing agents (such as 1,1,1-trichloroethane). Indeed, cleaning of the paste is simply done in warm or hot water. Thus, the new paste is environmentally safe.
2. It provides soldering personnel with a non-toxic, extremely safe, and highly effective solder paste to use, 3. Its use cuts the actual soldering time by ap-proximately 50~. This enables soldering to proceed at a considerably higher rate than permitted by rosin-based sol-ders, thereby subjecting electronic components to the heat of the solder for a far shorter period of time.
4. 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-impregnated solder pastes.
INDUSTRIAL APPLICABILITY
The solder paste of the invention is expected to find use in commercial soldering operations, particularly in soldering electrical components in circuit boards.
Thus, there has been disclosed a non-toxic, non-cor-rosive, environmentally-safe, water-soluble soldering paste, suitable for use in soldering electrical components.
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 considered to fall within the scope of the invention, as defined by the appended claims.
Claims (9)
1. A water-soluble solder paste comprising:
(a) at least about 80 wt% particulate solder; and (b) the balance a thixotropic flux base having a viscosity of at least about 200,000 cp and comprising (1) a botanical oil, (2) an aqueous emulsion of a thickening agent, and (3) a water-soluble organic acid having at least two carboxylic acid groups, said organic acid selected from the group consisting of citric acid, malic acid, tartaric acid, glutamic acid, phthalic acid, and succinic acid.
(a) at least about 80 wt% particulate solder; and (b) the balance a thixotropic flux base having a viscosity of at least about 200,000 cp and comprising (1) a botanical oil, (2) an aqueous emulsion of a thickening agent, and (3) a water-soluble organic acid having at least two carboxylic acid groups, said organic acid selected from the group consisting of citric acid, malic acid, tartaric acid, glutamic acid, phthalic acid, and succinic acid.
2. The paste composition of Claim 1 wherein said solder consists essentially of a tin-based solder.
3. The paste composition of Claim 1 wherein said thickening agent consists essentially of at least member selected from the group consisting of at least one food thickener and an ethoxylated linear alcohol.
4. The paste composition of Claim 3 wherein said food thickener is selected from the group consisting of corn starch, potato starch, lichen, and arrowroot powder.
5. The paste composition of Claim 4 wherein said thickening agent consists essentially of 170 g/l of corn starch in water.
6. The paste composition of Claim 3 wherein said thickening agent consists essentially of an ethoxylated linear alcohol in water in a ratio of at least about 1:1.
7. The paste composition of Claim 1 wherein said botanical oil comprises at least one oil selected from the group consisting of jojoba oil, palm oil, and peanut oil.
8. The paste composition of Claim 1 wherein said organic acid consists essentially of citric acid.
9. The paste composition of Claim 1 further including about 1 to 30 ppm of an odorant pleasing to the smell, said odorant selected from the group consisting of wintergreen oil, spearamint oil, and peppermint oil.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US60720090A | 1990-10-31 | 1990-10-31 | |
| US608,041 | 1990-10-31 | ||
| US607,200 | 1990-10-31 | ||
| US07/608,041 US5141568A (en) | 1990-05-15 | 1990-10-31 | Water-soluble soldering paste |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2053751A1 CA2053751A1 (en) | 1992-05-01 |
| CA2053751C true CA2053751C (en) | 1999-12-07 |
Family
ID=27085452
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2053751 Expired - Fee Related CA2053751C (en) | 1990-10-31 | 1991-10-18 | Water-soluble soldering paste |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPH0741434B2 (en) |
| CA (1) | CA2053751C (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101934437A (en) * | 2010-09-30 | 2011-01-05 | 常州市亚太微电子材料有限公司 | Unleaded solder paste and preparation method thereof |
| JP6592350B2 (en) * | 2014-12-26 | 2019-10-16 | 積水化学工業株式会社 | Anisotropic conductive material, connection structure, and manufacturing method of connection structure |
| JP7668512B2 (en) * | 2019-05-15 | 2025-04-25 | 株式会社弘輝 | Flux and solder paste |
-
1991
- 1991-10-18 CA CA 2053751 patent/CA2053751C/en not_active Expired - Fee Related
- 1991-10-31 JP JP28678391A patent/JPH0741434B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH04262891A (en) | 1992-09-18 |
| JPH0741434B2 (en) | 1995-05-10 |
| CA2053751A1 (en) | 1992-05-01 |
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| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |