JPH0428478B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to cream solder. Cream solder is a solder in the form of a cream solder in which powdered solder is dispersed in a flux containing rosins, activators, solvents, appropriate viscosity modifiers, and other additives. This is mainly used by coating or printing on metal substrates to be bonded. Therefore, the performance required for cream solder is
In addition to the performance required for general solder flux such as safety for the human body, good solderability, high insulation, non-corrosion, and no deterioration during storage, it also has excellent printing characteristics and post-soldering cleanability. It is particularly required that In particular, when cream solder is used for precision electronic components, it is necessary that it has excellent ejection properties during printing, that it ejects better than a screen plate or nozzle, and that the ejected material does not bleed or sag. A certain level of fluidity is required in order to have good dispensing properties, but if the fluidity is high, it will cause bleeding or sagging, so it is important for cream solder to have viscosity characteristics that satisfy both. is important. Conventionally, in order to obtain cream solder having such properties, a suitable viscosity modifier is added to the flux. For example, ester-based substances; hydrogenated oils such as coconut oil, tallow, castor oil, whale oil, rapeseed oil, semi-hardened oils, wood wax, beeswax, candelilla wax, carnauba wax, etc.; free acids; adipic acid, corkic acid; , azelaic acid, sebacic acid, dodecanedioic acid,
Myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, coconut oil fatty acid, tallow fatty acid, rapeseed oil fatty acid, montanic acid, polyethylene glycolic acid, benzoic acid, phthalic acid, trimellitic acid, etc. and inorganic or organic extender pigments; for example bentonite , organic bentonite, ultrafine silica,
Ultrafine powder alumina, aluminum stearate, etc. have been used. However, the above-mentioned ester-based substances have insufficient cleanability after soldering and tend to impede the wetting of molten solder onto the metal base, resulting in poor solderability. Organic or inorganic extender pigments inhibit the wetting of molten solder onto metal substrates and impede solder flow. This will worsen the problem and cause solder balls to form. In order to enable precision soldering of minute parts, the present inventors have developed a cream solder that has advanced printing and dispensing characteristics, good solderability, and aims to shorten the cleaning process. As a result, the inventors discovered that it is possible to produce cream solder with excellent thixotropy by blending a carboxylic acid having a hydroxyl group into the flux of cream solder, and completed the present invention.
That is, the present invention provides a cream solder consisting of solder and a flux containing at least a rosin, an activator, a solvent, and a viscosity modifier, which contains a hydroxycarboxylic acid having 16 to 24 carbon atoms as the viscosity modifier. do. In the present invention,
The hydroxycarboxylic acid having 16 to 24 carbon atoms is preferably an aliphatic carboxylic acid, having one or more hydroxyl groups, and preferably having no unsaturated groups. Examples of such hydroxycarboxylic acids are 12-hydroxystearic acid, 2-hydroxystearic acid,
-Hydroxypalmitic acid, 2-hydroxystearic acid, 2-hydroxyarachidic acid, 2-hydroxybehenic acid, 2-hydroxylignoceric acid, fatty acids of hydrogenated castor oil, oleic acid, linoleic acid or linolenic acid oxides, 12 -Hydroxystearic acid, 9,10-dihydroxystearic acid, 9,10,12-trihydroxystearic acid,
9,10,12,13-tetrahydroxystearic acid and the like. Particularly preferred hydroxycarboxylic acids are
12-hydroxystearic acid, and these are used in an amount of about 5 to about 20%, based on the weight of the flux. Hydroxycarboxylic acids having less than 16 carbon atoms have a low melting point and do not have a sufficient viscosity adjusting effect. Moreover, hydroxycarboxylic acids having more than 24 carbon atoms lack industrial practicality. Furthermore, hydroxycarboxylic acids having unsaturated groups, such as ricinoleic acid, have a low melting point, and if they are used alone, a sufficient viscosity adjusting effect cannot be obtained. When oxycarboxylic acid is added to flux as a viscosity modifier for cream solder, a hydrogen-bonding gel is formed due to the interaction between the hydroxyl group in the hydroxycarboxylic acid molecule, the relatively long carbon chain, and the free carboxyl group. formation, giving it very large thixotropic properties. If the amount of hydroxycarboxylic acid is less than 5% of the total flux, the above effect will be insufficient, and if it is more than 20%, good viscosity properties will not be obtained. Therefore, when the performance required for cream solder is well suited to the solderability, high insulation, non-corrosion, etc. obtained by these hydroxycarboxylic acids, it is recommended to use rosin instead of the rosin compounded in the flux. Alternatively, it may be used in place of a part of it. When hydroxycarboxylic acid is used as a thickener, solderability is significantly improved without impairing non-corrosion and high insulation properties.Furthermore, since it dissolves in chloride-based or fluorocarbon-based cleaning agents, it can be used after soldering. Improves cleaning performance. The present invention will be explained below with reference to Examples. Examples 1 to 3 A cream solder flux is prepared according to the following formulation. Prescription parts by weight Hydroxystearic acid 10 Polymerized rosin 55 Diethylene glycol monobutyl ether 34 Diethylamine hydrobromide 1 87 parts by weight of powdered solder was added to 13 parts by weight of the above-mentioned flux and thoroughly kneaded to obtain cream solder. Solderability of the obtained cream solder,
The thixotropic properties and detergency are shown in Table 1. Comparative Examples 1 to 7 Cream solder fluxes were prepared according to the following formulations. Formula 1 part by weight Stearic acid 10 Polymerized rosin 50 Diethylene glycol monobutyl 30 Etherhydroabiethyl alcohol 5 Methylhydroabietate 4 Diethylamine hydrobromide 1 Formula 2 parts by weight Hardened beef tallow 10 Polymerized rosin 50 Diethylene glycol monobutyl 30 Etherhydroabiethyl alcohol 5 Methylhydroabietate 4 Diethylamine hydrobromide 1 formulation 3 parts by weight Polyethylene glycol 20000 10 Polymerized rosin 50 Diethylene glycol monobutyl 30 Etherhydroabiethyl alcohol 5 Methylhydroabietate 4 Diethylamine hydrobromide 1 formulation 4 parts by weight Carnauba Wax 10 Polymerized rosin 50 Diethylene glycol monobutyl 30 Etherhydroabiethyl alcohol 5 Methylhydroabietate 4 Diethylamine hydrobromide 1 formulation 5 parts by weight Ultrafine silica 4 Polymerized rosin 51 Diethylene glycol monobutyl 32 Etherhydroabiethyl alcohol 6 Methylhydro Abietate 6 Diethylamine hydrobromide 1 formulation 6 parts by weight Aluminum stearate 4 Polymerized rosin 51 Diethylene glycol monobutyl 32 Etherhydroabiethyl alcohol 6 Methylhydroabietate 6 Diethylamine hydrobromide 1 formulation 7 parts by weight Hydrogenated castor oil 4 Polymerization Rosin 51 Diethylene glycol monobutyl 32 Etherhydroabiethyl alcohol 6 Methylhydroabietate 6 Diethylamine hydrobromide 1 Powdered solder in 13 parts by weight of the above formulated flux
87 parts by weight was added and thoroughly kneaded to obtain cream solder. Solderability of the obtained cream solder,
The thixotropic properties and detergency are shown in Table-1.

【table】

【table】

Claims (1)

[Claims] 1. A cream solder consisting of solder and a flux containing at least a rosin, an activator, a solvent, and a viscosity modifier, the cream solder containing a hydroxycarboxylic acid having 16 to 24 carbon atoms as the viscosity modifier. . 2 Add hydroxycarboxylic acid to 5% of the total amount of flux.
20% by weight of the cream solder according to item 1. 3. The cream solder according to item 1, wherein the hydroxycarboxylic acid is a fatty acid of hydrogenated castor oil. 4. The cream according to item 1, wherein the hydroxycarboxylic acid is selected from 2-hydroxypalmitic acid, 2-hydroxystearic acid, 2-hydroxyarachidic acid, 2-hydroxybehenic acid, and 2-hydroxygnoceric acid. Solder. 5. The cream solder according to item 1, wherein the hydroxycarboxylic acid is a hydroxycarboxylic acid obtained by oxidizing linoleic acid or linolenic acid.