Metal treatment – Compositions – Fluxing
Patent
1986-03-18
1988-08-09
Rosenberg, Peter D.
Metal treatment
Compositions
Fluxing
148 24, 148 25, 228223, 228224, B23K 3534
Patent
active
047625732
DESCRIPTION:
BRIEF SUMMARY
This invention is related to a fluxing agent for soldering e.g. electronic components and a process for soldering using said fluxing agent.
When soldering with a solder based preferably on tin and tin alloys a fluxing agent is conventionally used, which improves the contact of the solder with the surfaces intended to be soldered and bonding to said surfaces, especially surfaces of such metals as copper, brass, iron, etc. Examples of such conventional fluxing agents are water-based fluxing agents and resin-based fluxing agents. The main purpose of such fluxing agents is to remove the oxide layer and to improve spreading on the surface, and they usually comprise (1) an acid cleaving agent, (2) an organic acid, (3) a carrier, (4) solvent and (5) a tenside.
Examples of literature discussing fluxing agents are: Multicore Solders Ltd., Hemel, Hempstead, Hearts. 1980. Production, July, 1980, 89.
The fluxing agent according to the invention is distinguished from these conventional fluxing agents and is based on a combination of nonionic surface active agent and/or another substance with similar capacity to form liquid crystals together with at least the main part of the other constituents of the fluxing agent, at least after evaporating at least 50%, at least 80%, at least 95% or at least 98% of the volatile solvent, and water and for a satisfactory soldering effect suitable quantities of so-called activators capable of reacting with impurities on the surfaces intended for soldering, e.g. halides and carboxylic acids. The fluxing agent comprises also volatile solvent, preferably as a main constituent and frequently in a quantity of at least 80% by weight. The contents of nonionic surface active agent (and/or another substance with similar capacity to form liquid crystals, as mentioned above) and water and the remaining constituents are preferably selected so that the fluxing agent after application on a surface and evaporating the volatile solvent to at least 50% and preferably to at least 80% or 90% by weight comprises the remaining constituents dissolved in the mixture of surface active agent (and/or another substance with similar capacity to form liquid crystals) and water or with the formation of liquid crystals in the fluxing agent film remaining after evaporating the solvent.
The contents of the main constituents nonionic surface active agent (and/or another substance with similar capacity to form liquid crystals), water and volatile, especially organic, solvent are suitably at least 0.5% by weight, preferably at least 1% by weight, at least 2% by weight or at least 5% by weight, and preferably at most 20% by weight, especially at most 15% by weight or at most 12% by weight nonionic surface active agent (and/or another substance with similar liquid crystal forming activity), at least 0.5% by weight, preferably at least 1% by weight, at least 2% by weight or at least 5% by weight water and preferably at most 80%, especially at most 50% at most 20%, at most 15% or at most 10% by weight water and balance mainly volatile solvent, preferably in a quantity of at least 50%, especially at least 80% or at least 90% by weight, said weight percentage figures being based on the total weight of the fluxing agent or optionally on the weight of the three main constituents nonionic surface active agent (and/or another substance with similar liquid crystal forming activity), water and volatile solvent. Furthermore, it is important that the ratio of nonionic surface active agent (and/or another substance with similar liquid crystal forming activity): water is preferably at least 1:8, suitably at least 0.5:1 or at least 0.75:1, and suitably at most 5:1, especially at most 2:1 or at most 1.5:1. A suitable value of said ratio is frequently about 1.
Examples of suitable nonionic surface active agents are mono or dialkylphenol ethylene oxide and/or propylene oxide adducts, preferably mono or di-C.sub.3 -C.sub.18 alkylphenol-2-150-EO/PO (i.e. alkylphenol ethylene oxide/propylene oxide adducts comprising 2-150 ethylene oxide units a
REFERENCES:
patent: 4077815 (1978-03-01), Schuessler
patent: 4151015 (1979-04-01), Cooper
patent: 4168996 (1979-09-01), Zado
patent: 4342607 (1982-08-01), Zado
patent: 4523712 (1985-06-01), Zado
patent: 4561913 (1985-12-01), Zado
Dougherty Ralph H.
Rosenberg Peter D.
Ytkemiska Institutet
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