Additive for fluxes and soldering pastes

Abstract: An additive contains a deactivation agent functioning at soldering temperature. This novel additive is used for fluxes and soldering pastes. In the course of soldering, the deactivation agent in the additive deactivates an activator such as organic acids contained in the flux and the soldering paste in order for removal of an oxide film from a metallic base used for electric circuit. By use of the additive, corrosion of the metallic base with the activator is protected even though the activator remains on the base. The additive enables to omit an unnecessary washing step from a preparation of electric circiut.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to the use of blocked isocyanates and/or polyvalent metal compounds and/or epoxy resins as a deactivation agent for fluxes and soldering pastes. In the field of electronics, fluxes are widely used for the purpose of removal of an oxide film on a metallic base. A flux obtained according to the present invention never corrodes metallic bases even though it remains on the metallic bases after soldering. Description of Prior Art In a general method for soldering electronic parts on a metallic base (for example, copper base) for electronic circuits, a surface of the base is treated with a flux to remove an oxide film and then the surface is dipped into a melted solder bath. However, this method requires two steps: (1) treatment with the flux and (2) dipping into the solder bath. Further, in this method, some of electronic parts put on the base have removed occasionally from the base in the course of the steps. In order to solve these problems, the method using a soldering paste containing a flux and solder particles has been developed. According to the method, the soldering paste is applied on a base by, for example, a dispenser and then heated or irradiated with ultraviolet light to complete soldering. Since the soldering paste is viscous, electronic parts are easily held on the base. However, even the above method has some disadvantages. The soldering paste contains an activator such as organic acids and organic acid salts in order to remove an oxide film on the base perfectly. After soldering, the soldered base has to be washed to remove the activator because the corrosion of the base with remaining activator continues after completion of the soldering operation. In general, a solvent of fluorohydrocarbons such as Freon and water are used for this washing. However, the use of fluorohydrocarbons tends to be prohibited because they have harmful effects on the atmospheric environment. Further, if water is use for the washing, the resulting waste water is polluted with heavy metals and cannot be discharged without removal of the metals. In FR-A-2 143 734 fluxes are disclosed containing resinous synthetic polymers carrying functional radicals which produce active hydrogen at soldering temperatures for reducing metal oxides present on the metallic base to be soldered. The functional radicals may be amide, amine, carboxyl, imine and mercaptan. They provide for controlled polymerisation of the synthetic polymeric resin. Besides those, other functional radicals like epoxides or isocyanates may be introduced into the polymers by means of a supplementary reaction. From GB-A-1 300 427 fluxes are known comprising epoxide resin, rosin, triethanolamine and a fluoroborate of a polyvalent metal. During soldering, the fluoroborate decomposes. Boron trifluoride which is active to remove oxide films on the metallic base to be soldered acts as a hardener for the epoxide. As it is completely consumed in the hardening reaction, no corrosive compound remains on the soldered part after soldering. An object of the present invention is to improve soldering pastes which contain an activator such that they do not continue to corrode a base after soldering even though the soldered base is not subjected to a washing step. Another object of the present invention is to improve fluxes which contain an activator such that they do not continue to corrode a base after soldering even though the flux is contained in a soldering paste and the base soldered with this paste is not subjected to a washing step. SUMMARY OF THE INVENTION The present invention relates to the use of blocked isocyanates and/or polyvalent metal compounds and/or epoxy resins as a deactivation agent for fluxes and soldering pastes, the fluxes and soldering pastes containing an activator selected from non-polymeric organic acids and organic acid salts and the deactivation agent reacting with the organic acid or the organic acid salt in the course of soldering. The deactivation agent may be used in the form of an additive containing additional components, e.g. catalysts or solvents. DETAILED DESCRIPTION OF THE INVENTION The present invention will now be explained in detail below. Fluxes and soldering pastes contain a non-polymeric organic acid or an organic acid salt as the activator removing an oxide film on a metallic base. The present invention utilizes the reaction of the non-polymeric organic acid or the organic acid salt with a deactivation agent in the course of soldering. The deactivation agent used according to the present invention does not function at ordinary temperature but functions in the vicinity of soldering temperature. That is, the deactivation agent is selected from the compounds which do not react with the acid or the salt at ordinary temperature but react in the vicinity of soldering temperature. The deactivation agent is selected from the group consisting of blocked isocyanates, polyvalent metal compounds and epoxy resins. The "blocked isocyanate" is a compound represented by the formula RNHCOB and obtained by reacting an NCO group of an isocyanate compound (R-NCO) with a volatile active hydrogen compound (HB) worked as a blocking agent. The blocked isocyanate is inacitve to the activator, i.e. to the non-polymeric organic acids or organic acid salts at ordinary temperature and exhibits reactivity to the activator at an elevated temperature because the blocked isocyanate is decomposed at an elevated temperature and produces the isocyanate compound (R-NCO) reactive to the activator. The blocked isocyanate used is determined by taking account of the melting point of the used solder particles and the soldering temperature applied. The decomposition temperature of the blocked isocyanate has to be lower than the soldering temperature. The decomposition temperature suitably ranges from about 50 to 350 °C, preferably in the vicinity of the melting point of the solder particles, for example from about 150 to 250°C. Examples of the active hydrogen compound used as the blocking agent include alcohols, phenols, ε-caprolactam, oximes and active methylene compounds. It is provided that the active hydrogen compound is not limited to these compounds. The blocked isocyanates are classified into two groups, monomers and polymers, and both of blocked isocyanates are usable to the present invention. It is possible to add various catalysts to the additive in order to control reactivity of the blocked isocyanate. Examples of the catalysts include N-methylmorpholine. An adding amount of the catalyst to the additive may be determined on the basis of the type and the amount of the blocked isocyanate and the type of the catalyst. For instance, in the case that an HDI (hexamethylenediisocyanate) type isocyanate using phenol as the blocking agent is used as the blocked isocyanate and N-methylmorpholine is used as the catalyst, 0.001 to 1 parts by weight of the catalyst is suitably used with respect to 100 parts by weight of the blocked isocyanate. The "polyvalent metal compound" is a compound forming a salt with the non-polymeric organic acid or the organic acid salt in the course of soldering. The polyvalent metal compounds used in the present invention are the compounds inactive to the activator, i.e. to the non-polymeric organic acids or the organic acid salts at ordinary temperature and exhibiting reactivity to the activator at an elevated temperature. That is, the polyvalent metal compounds used as the deactivation agent are the compounds which are decomposed at an elevated temperature and produce salts with the non-polymeric organic acid and the organic acid salt acting as the activator. The polyvalent metal compound used is determined by taking account of the melting point of the used solder particles and the soldering temperature applied. The decomposition temperature of the polyvalent metal compound has to be lower than the soldering temperature. The decomposition temperature ranges from about 50 to 350°C, preferably in the vicinity of the melting point of the solder particles, for example from about 150 to 250°C. Polyvalent metal complexes are exemplified as the polyvalent metal compound. Any metal with 2 or more of valences can be used as the polyvalent metals contained in the polyvalent metal complex. Examples of the polyvalent metals include beryllium, cadmium, copper, calcium, magnesium, zinc, zirconium, barium, strontium, aluminum, bismuth, antimony, lead, cobalt, iron, nickel and titanium. Examples of the ligands for formation of the polyvalent metal complexes include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glycollic acid, malic acid, tartaric acid, lactic acid, citric acid, diglycollic acid, benzoic acid, salicylic acid, ethylenediamine, iminodiacetic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid, glycine, sarcosine, alanine, octanediol, hexanediol, acetylacetone, methylacetoacetate, ethylacetoacetate, diacetone alcohol, diethyltriamine, triethylenetetramine, triaminotriethylamine, pentaethylenehexamine, N-hydroxyethylethylenediamine, N,N'-dihydroxyethylethylenediamine, triethanolamine, N,N'-dimethylethylenediamine, N,N'-tetramethylethylenediamine, 1,3-diaminopropane, 1,2-diaminopropane, pyridine, dipyridyl, terpyridyl, N-dihydroxyethylglycine, N-hydroxyethyliminoacetic acid, N,N'-ethylenediaminediacetic acid, N-hydroxyethylethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid,1,2-cyclohexanediaminetetraacetic acid, trimethylenediaminetetraacetic acid, ethyleneglycoldiethyletherdiaminetetraacetic acid, ethyldiaminetetrapropionic acid, β-aminoethylphoshoric acid N,N-diacetic acid, aminomethylphoshoric acid N,N-diacetic acid, ascorbic acid, thioglycolic acid, 2,3-dimercaptopropanol, thiourea, sodium diethyldithiocarbamate, 8-oxine, acetylacetone, phenanthrene, aspartic acid, dimethylglyoxime, glyoxal-bis, thenoyltrifluoroacetone, carbonic acid, ammonia and amine. Examples of the polyvalent metal complexes include titanium acetylacetate, dipyridyl copper, acetylacetone cobalt, bis(dimethylglyoxymate) nickel, titanium octylglycolate, titanium lactate and titanium lactate ethylester. In the present invention, epoxy resins having an epoxy group inactive to the non-polymeric organic acid or salt used as the activator at ordinary temperature and exhibiting reactivity to the activator at an elevated temperature are usable as the epoxy resin. The epoxy resin used is determined by taking account of the melting point of the used solder particles and the soldering temperature applied. The reaction starting temperature of the epoxy resin with the activator has to be lower than the soldering temperature. The reaction temperature suitably ranges from about 50 to 350 °C, preferably in the vicinity of the melting point of the solder particles, for example from about 150 to 250°C. It is provided that epoxy resins having two or more epoxy groups in a molecule are particularly preferred from the viewpoint that they make polymers by cross linkage reaction with the activator. Examples of types of the epoxy resin include bisphenol A type, halogenated bisphenol type, bisphenol F type, resorcin type, tetrahydroxyphenolethane type, novolak type, polyalcohol type, polyglycol type, glycerin triether type, polyolefine type, epoxy soybean oil and alicyclic type. In particular, it is preferred to use bisphenol A type, halogenated bisphenol type, bisphenol F type and resorcin type epoxy resins. It is possible to add various catalysts to the additive, the flux and the soldering paste in order to control reactivity of the epoxy resin. Examples of the catalyst include diethylenetriamine, ethylenediamine and the like. An adding amount of the catalyst may be determined on the basis of the type and the amount of the epoxy resin and the type of the catalyst. For instance, in the case that bisphenol A is used as the epoxy resin and diethylenetriamine is used as the catalyst, about 10 to 15 parts by weight of the catalyst is suitably used with respect to 100 parts by weight of the epoxy resin. The concentration of the deactivation agent in the additive used according to the present invention is not limited but preferably ranges, for example, between about 50 and 100 wt% based on the weight of the additive. The additive used according to the present invention may further comprise a solvent. Any solvent dissolving the deactivation agent is usable without limitation. It is provided that the use of the solvent with a boiling point lower than the melting point of soldering particles is preferred. The soldering temperature has to be relatively higher than the melting point of the soldering particles. If the solvent with a boiling point higher than the melting point is used, there is the possibility to deteriorate the properties of the obtained electronic circuit. In particular, with respect to solvents with a carboxyl group or a hydroxyl group, a boiling point of the solvent is preferably lower than the decomposition temperature or the reaction starting temperature of the deactivation agent from the viewpoint of facility of reaction between the deactivation agent and the activator. That is, a boiling point of the solvent is preferably lower than the decomposition temperature of the blocked isocyanate and the polyvalent metal compound, and a boiling point of the solvent is preferably lower than a reaction starting temperature of the epoxy resin with the activator. Examples of the solvents include aliphatic compound (n-hexane (b.p. 68.7)(hereinafter, the number in parentheses is a boiling point), isohexane (60-64), n-heptane (98.4)), esters (isopropyl acetate (89.0), methyl propionate (79.7), ethyl propionate (99.1)), ketones (methylethylketone (79.6), methyl-n-propylketone (103.3), diethylketone (102.2)), alcohols (ethanol (78.3), n-propanol (97.2), isopropanol (82. 3), isobutanol (107.9), and secondary butanol (99.5)). The flux obtainable according to the present invention will now be explained. According to the present invention a flux results which contains the above-mentioned deactivation agent and the activator, i.e. non-polymeric organic acids and organic acid salts and if necessary the catalyst for the deactivation agent and a solvent. The non-polymeric organic acid and the organic acid salt act as the activator. The activator in the flux acts to remove an oxide film on the base at ordinary temperature as the soldering paste containing the flux is applied on a metallic base. Examples of the non-polymeric organic acid include monocarboxylic acids (formic acid, acetic acid, propionic acid, capronic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid), dicarboxylic acids (oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid), oxycarboxylic acids (oxysuccinic acid, citric acid, tartaric acid, hydroxyacetic acid, salicylic acid, (m-, p-) hydroxybenzoic acid, 12-hydroxydodecanoic acid, 12-isobutyric acid, (o-, m-, p-) hydroxyphenylacetic acid, 4-hydroxyphthalic acid, 12-hydroxystearic acid) and the like. Examples of the organic acid salt include salts of the above-mentioned organic acid with an amine (for example, diethylaminoethanol), ammonia and an alkali metal (for instance, sodium, potassium and the like). The flux obtained by the use according to the present invention may also contain the above-mentioned solvent. The content of the blocked isocyanate to the non-polymeric organic acid or the organic acid salt (or a mixture thereof) in the flux is expressed in the molar ratio of NCO groups in the blocked isocyanate against COOH groups contained in the organic acid or the organic acid salt and suitably ranges from 1:0.05 - 3, preferably 1:0.5 - 1.5 from the viewpoint of effective prevention of a metallic base from corroding. It is suitable that the content of the non-polymeric organic acid, the organic acid salt, the blocked isocyanate and the solvent in the flux are as follows: non-polymeric organic acid or organic acid salt: 0.1 - 30 parts by weight, blocked isocyanate: 0.1 - 50 parts by weight, solvent: 20 - 99.8 parts by weight. The content of the polyvalent metal compound to the non-polymeric organic acid or the organic acid salt (or a mixture thereof) in the flux is expressed in the equivalent ratio of polyvalent metal of the polyvalent metal compound against COOH groups contained in the organic acid or the organic acid salt and suitably ranges from 1:0.05 - 5, preferably 1: 0.5 - 2 from the viewpoint of effective prevention of a metallic base from corroding. It is suitable that the content of the non-polymeric organic acid, the organic acid salt, the polyvalent metal compound and the solvent in the flux are as follows: non-polymeric organic acid or organic acid salt: 0.1 - 50 parts by weight, polyvalent metal compound: 0.05 - 40 parts by weight, solvent: 10 - 99.85 parts by weight. The content of the epoxy resin to the non-polymeric organic acid or the organic acid salt (or a mixture thereof) in the flux is expressed in the molar ratio of epoxy groups in the epoxy resin against COOH groups contained in the organic acid or the organic acid salt and suitably ranges from 1:0.05 - 10, preferably 1:0.5 - 5 from the viewpoint of effective prevention of a metallic base from corroding. It is suitable that the content of the non-polymeric organic acid, the organic acid salt, the epoxy resin and the solvent in the flux are as follows: non-polymeric organic acid or organic acid salt: 0.1 - 30 parts by weight, epoxy resin: 0.1 - 90 parts by weight, solvent: 10 - 99.8 parts by weight. The flux obtained by the use according to the present invention may contain a rosin in addition to the components such as the non-polymeric organic acid and the like. Various rosins may be used as the rosin. Rosin modified with maleic acid, rosin ester modified with maleic acid, hydrogenated rosin, disproportionated rosin, polymerized rosin, gum rosin, wood rosin, tall oil rosin and the like are exemplified. Especially, taking into considaration of corrosiveness of solder, the use of esterified rosin such as rosin ester modified with maleic acid is preferred. The main component of the rosin is abietic acid or abietic acid type compounds such as isomers or polymers of abietic acid. Abietic acid and abietic acid type compounds do not exhibit activity at ordinary temperature, and under heating at 90°C or more, they melt and exhibit activity to remove an oxide film on a metallic base. Thus they are not corrosive in storage at ordinary temperature. Therefore, in the present invention, any rosin containing abietic acid or abietic acid type compounds is usable. The content of rosin may range, for example from 10 to 10000 parts by weight based on 100 parts by weight of the non-polymeric organic acid or the organic acid salt. The soldering paste obtained by making use of the present invention contains solder particles in addition to the above-mentioned flux. The "solder particles" used herein include not only tin-lead alloys generally known as the solder but also alloys further containing silver, bismuth, gold, iridium and the like. The shape of the solder particles is not limited. The particle size suitably ranges from 10 to 1000 mesh, preferably from 250 to 400 mesh. The weight ratio of the solder particles to the flux is not limited but it is preferred that the amount of the solder particles ranges from 40 to 95 parts by weight and that of the flux ranges from 5 to 60 parts by weight. The soldering paste may further contain a thixotropic thickener and the content of the thicker may be between 0.1 and 20 weight %, preferably between 1 and 15 weight % of the paste. The present invention will be illustrated more in detail with reference to Examples. EXAMPLES Example 1 (Flux composition) A non-polymeric organic acid (or an organic acid salt), a rosin, an activator and a solvent are added to a preparation vessel with an agitation apparatus and stirred to dissolve perfectly all components. After dissolution of the materials, an additive is added to obtain a flux composition. The charging amounts of each component are listed in Table 1. The spread factor and corrosiveness of the resulting flux compositions are estimated. The spread factor is measured according to U.S. Standard QQ-S-571E. The corrosiveness is measured based on JIS-Z-3197 6.6. The results are shown in Table 3. Additives (Blocked isocyanate) OLESTER NP-1060PB: Mitsui Toatsu Chemicals Inc. EPOKEY EPR-170: Mitsui Toatsu Chemicals Inc. OLESTER PB3537: Mitsui Toatsu Chemicals Inc. OLESTER XQ5095PB: Mitsui Toatsu Chemicals Inc. CORONATE 2507: Nippon Polyurethane Industry Inc. CORONATE 2513: Nippon Polyurethane Industry Inc. Additive Average Molecular Weight Effective NCO % Nonvolatile matter % OLESTER NP-1060PB 1200 9.3 60 EPOKEY EPR-170 1350 4.3 70 OLESTER PB3537 1400 5.0 60 OLESTER XQ5095PB 1300 5.0 55 CORONATE 2507 800 11.6 80 CORONATE 2513 800 10.2 80 Flux Spread factor Corrosiveness Composition of Present Invention 1 80 Ex 2 81 Ex 3 74 Ex 4 72 Ex 5 75 Ex - P(F) 6 83 Ex 7 80 Ex 8 75 Ex 9 78 Ex 10 81 Ex Comparative Example 11 81 P(C) 12 81 P(C) 13 77 P(A) 14 75 P(B) 15 77 P(C) Estimation of Corrosiveness Ex : Suitable flux (Deposited copper or plated copper is not corroded with flux.) P : Unsuitable flux A : Copper under flux is corroded and disappeared. B : Copper under the edge of flux is corroded and disappeared. C : Copper under the center of flux is corroded and disappeared. D : The edge of flux is discolored because of corrosion and looks an umbrella. E : The center of flux is discolored because of corrosion. F : The edge of flux looks opaque dark brown. Example 2 (Soldering paste) A thixotropic thicker is added to the flux composition obtained in Example 1 by use of an ink mixer (high viscosity mixer) to dissolve completely. Then solder particles are added to the dissolved flux composition and agitated until an uniform soldering paste is obtained. The flux composition and the amount of solder particles are shown in Table 4. The spread factor, formation of solder balls and corrosiveness of the resulting flux compositions are estimated. The spread factor is measured according to U.S. Standard QQ-S-571E. The solder ball test is conducted according to U.S. Standard ANSI/IPC-SP-819. The corrosiveness is measured based on JIS-Z-3197 6.6. The results are shown in Table 5. Soldering Paste Spread factor Solder ball test Corresiveness Present Invention 1 83 A Ex 2 84 A Ex 3 76 A Ex 4 81 A Ex 5 78 B Ex Comparative Example 6 81 A P(C) 7 80 A P(C) Estimation of solder ball test A : Preferred B : Acceptable C : Unacceptable Estimation of Corrosiveness Ex : Suitable flux (Deposited copper or plated copper is not corroded with flux.) P : Unsuitable flux A : Copper under flux is corroded and disappeared. B : Copper under the edge of flux is corroded and disappeared. C : Copper under the center of flux is corroded and disappeared. D : The edge of flux is discolored because of corrosion and looks an umbrella. E : The center of flux is discolored because of corrosion. F : The edge of flux looks opaque dark brown. Example 3 (Flux composition) A non-polymeric organic acid (or an organic acid salt), a rosin, an activator and a solvent are added to a preparation vessel with an agitation apparatus and stirred to dissolve perfectly all components. After dissolution of the materials, an additive is added to obtain a flux composition. The charging amounts of each component are listed in Table 6. The spread factor and corrosiveness of the resulting flux compositions are estimated. The spread factor is measured according to U.S. Standard QQ-S-571E. The corrosiveness is measured based on JIS-Z-3197 6.6. The results are shown in Table 7. Flux Spread factor Corrosiveness Composition of Present Invention 1 81 Ex 2 80 Ex 3 78 Ex 4 75 Ex 5 73 Ex - P(F) 6 83 Ex 7 78 Ex 8 75 Ex 9 80 Ex 10 79 Ex Comparative Example 11 80 P(C) 12 78 P(C) 13 78 P(A) 14 74 P(A) 15 77 P(D) The corrosiveness is shown by the same categories as those used in Example 1. Example 4 (Soldering paste) A thixotropic thickener is added to the flux composition obtained in Example 3 by use of an ink mixer (high viscosity mixer) to dissolve completely. Then solder particles are added to the dissolved flux composition and agitated until an uniform soldering paste is obtained. The flux composition and the amount of solder particles are shown in Table 8. The spread factor, formation of solder balls and corrosiveness of the resulting flux compositions are estimated. The spread factor is measured according to U.S. Standard QQ-S-571E. The solder ball test is conducted according to U.S. Standard ANSI/IPC-SP-819. The corrosiveness is measured based on JIS-Z-3197 6.6. The results are shown in Table 9. Soldering Paste Spread factor Solder ball test Corrosiveness Present Invention 1 83 A Ex 2 82 A Ex 3 77 A Ex 4 80 A Ex 5 75 B Ex Comparative Example 6 82 A P(C) 7 80 A P(C) The solder ball test and the corrosiveness are shown by the same categories as those used in Example 2. Example 5 (Flux composition) A non-polymeric organic acid (or an organic acid salt), a rosin, an activator and a solvent are added to a preparation vessel with an agitation apparatus and stirred to dissolve perfectly all components. After dissolution of the materials, an additive is added to obtain a flux composition. The charging amounts of each component are listed in Table 10. The spread factor and corrosiveness of the resulting flux compositions are estimated. The spread factor is measured according to U.S. Standard QQ-S-571E. The corrosiveness is measured based on JIS-Z-3197 6.6. The results are shown in Table 12. Additives (Epoxy resin) EPICLON 840: Manufactured by Dainippon Ink Chemical Industry Inc., Bisphenol A type EPICLON 830S: Manufactured by Dainippon Ink Chemical Industry Inc., Bisphenol F type EPICLON 860-90X: Manufactured by Dainippon Ink Chemical Industry Inc., Solvent diluted type EPICLON 153-60T: Manufactured by Dainippon Ink Chemical Industry Inc., Flame-retardant type EPICLON 707: Manufactured by Dainippon Ink Chemical Industry Inc., polyalcohol ether type EPICLON 430: Manufactured by Dainippon Ink Chemical Industry Inc., polyglycidyl type Additive Epoxy Equivalent Nonvolatile matter % Viscosity (25°C) EPICLON 840 180-190 100 9000-11000CPS EPICLON 830S 180-190 100 3000-4500CPS EPICLON 860-90X 165-185 90 Z₃-Z₆(GARDNER) EPICLON 153-60T 390-410 100 Less than A (GARDNER) EPICLON 707 300-340 100 50-100CPS EPICLON 430 110-130 100 8000-14000CPS Flux Spread factor Corrosiveness Composition of Present Invention 1 78 Ex 2 78 Ex 3 87 Ex 4 82 Ex 5 80 Ex - P(C) 6 85 Ex 7 78 Ex 8 81 Ex 9 78 Ex 10 80 Ex Comparative Example 11 78 P(C) 12 78 P(D) 13 86 P(F) 14 80 P(F) 15 80 P(B) The corrosiveness is shown by the same categories as those used in Example 1. Example 6 (Soldering paste) A thixotropic thickener is added to the flux composition obtained in Example 5 by use of an ink mixer (high viscosity mixer) to dissolve completely. Then solder particles are added to the dissolved flux composition and agitated until an uniform soldering paste is obtained. The flux composition and the amount of solder particles are shown in Table 13, The spread factor, formation of solder balls and corrosiveness of the resulting flux compositions are estimated. The spread factor is measured according to U.S. Standard QQ-S-571E. The solder ball test is conducted according to U.S. Standard ANSI/IPC-SP-819. The corrosiveness is measured based on JIS-Z-3197 6.6. The results are shown in Table 14. Soldering Paste Spread factor Solder ball test Corrosiveness Present Invention 1 80 B Ex 2 78 A Ex 3 82 A Ex 4 76 A Ex 5 74 A Ex Comparative Example 6 80 B P(E) 7 76 A P(C) The solder ball test and the corrosiveness are shown by the same categories as those used in Example 2.

Claims: The use of blocked isocyanates and/or polyvalent metal compounds and/or epoxy resins as a deactivation agent for fluxes and soldering pastes, the fluxes and soldering pastes containing an activator selected from non-polymeric organic acids and organic acid salts and the deactivation agent reacting with the organic acid or the organic acid salt in the course of soldering. The use of claim 1 wherein the fluxes and soldering pastes contain a non-resinous, non-polymeric organic acid or a non-resinous, non-polymeric organic acid salt. The use of claim 1 or 2 wherein the molar ratio of NCO groups in the blocked isocyanate to COOH groups in the organic acid or in the organic acid salt (NCO:COOH) ranges from 1:0.05 to 3:1. The use of claim 1 or 2 wherein the polyvalent metal compound is a compound forming salts with the organic acid or the organic acid salt in the course of soldering. The use of any one of claims 1, 2, 4 wherein the equivalent ratio of polyvalent metals of the polyvalent metal compound to COOH groups in the organic acid or in the organic acid salt (equivalent of metal:COOH) ranges from 1:0.05 to 5:1. The use of claim 1 or 2 wherein the molar ratio of epoxy groups in the epoxy resin to COOH groups in the organic acid or in the organic acid salt (epoxy group:COOH) ranges from 1:0.05 to 10:1. The use of any one of claims 1 to 6 wherein the flux or soldering paste further comprises a solvent with a boiling point lower than the melting point of the solder. The use of any one of claims 1 to 7 wherein the flux or soldering paste further comprises abietic acid or abietic acid derivatives. The use of any one of claims 1 to 8 wherein the soldering paste further comprises soldering particles. The use of claim 9 wherein the soldering particles are selected from the group consisting of tin-lead alloys, silver-tin-lead alloys, bismuth-tin-lead alloys, gold-tin-lead alloys and iridium-tin-lead alloys.

Inventors: GOMI TADASHI, KANEKO KAZUE, OTA HIROKO, GOMI, TADASHI, KANEKO, KAZUE, OTA, HIROKO
Applicants: YUHO CHEMICALS INC, YUHO CHEMICALS INC.
Application year: 1990
Main classification: B23K35
IPC codes: B23K35