JPH07116889A - Flux for soldering - Google Patents

Abstract

PURPOSE:To provide the flux for soldering for non-washing having excellent active power and excellent electrical insulating characteristic by using a carboxylic acid having a monocyclic structure, heterocyclic structure or ester bond structure as an activator. CONSTITUTION:The carboxyl group of the carboxylic acid has an effect of activating at a soldering temp. and removing the oxides on the surfaces of joining metals by reacting with these oxides. The carboxylic acid having the monocyclic structure, heterocyclic structure or ester bond structure is, the reupon, used as the activator of the flux for soldering, by which multicarboxylation is made possible and the excellent active power is obtd. Dissolution is extremely little even in the presence of moisture as is evident from the structure. The flux is, therefore, excellent in the electrical insulating characteristic and hardly generates current leakage and migration. Further, the flux hardly forms copper soap and whitens even if the flux remains as residues.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soldering flux, and more particularly to a soldering flux containing a carboxylic acid as an activator.

[0002]

2. Description of the Related Art Soldering is a joining technique which is used in various industrial fields including a fine joining technique in the fields of electronic equipment and precision equipment. Generally, when soldering, a flux is used in order to prevent the base material and the solder from being oxidized at the soldering temperature and to ensure the wettability. As the flux, rosin dissolved in an organic solvent is widely used, and usually an activator is added to further improve solderability. The activator has a function of cleaning the oxide on the surface of the joining metal, preventing regeneration of the oxide, and facilitating the wetting of the solder.

As conventional activators used for the flux, amine hydrohalides such as diethylamine hydrochloride, diethylamine hydrobromide and pyridine hydrobromide are known. Organic carboxylic acids are also widely used as activators, but their types are limited to some extent, and mainly alkyl monocarboxylic acids and dicarboxylic acids. Specifically, an organic carboxylic acid having a linear or side chain structure such as adipic acid, succinic acid, stearic acid, glutaric acid is used.

As other activator, a dicarboxylic acid having 4 to 12 carbon atoms is used (Japanese Patent Publication No. 1-4).
9599) and those using gallic acid esters (Japanese Patent Publication No. 4-33557).

[0005]

However, although the flux using an amine hydrohalide as an activator is excellent in the activity, the hydrohalic acid is liberated with the passage of time to cause corrosion. It has been confirmed that

The organic carboxylic acid having a linear or side chain structure as described above, when used as an activator,
While it has the advantage that corrosion is unlikely to occur when using amine hydrohalides, it also has many problems caused by moisture absorption. For example, an organic carboxylic acid having a relatively small molecular weight (having 3 to 6 carbon atoms) has excellent activity because the carboxyl group is relatively easily ionized (COOH → COO ⁻ + H ⁺ ), but is dissolved in the presence of water. And it is easy to become an ion. Therefore, it often causes current leakage or migration. Further, an organic carboxylic acid having a large molecular weight has a problem that its carboxylic group is difficult to be ionized and its activity is weak.

When a flux using an organic carboxylic acid having a linear or side chain structure as described above becomes a residue after soldering, it reacts with copper oxide in the presence of water to produce a green copper soap. Cleaning is indispensable because it may cause whitening or cause whitening.

The present invention has been made by paying attention to such a conventional technique, and provides a flux for soldering without cleaning, which is excellent in activation power, is excellent in electric insulation and is unlikely to cause current leakage or migration. It is the one we are trying to provide.

[0009]

In order to solve the above-mentioned problems, the soldering flux according to the present invention activates one or more compounds selected from the group consisting of compounds represented by the following formulas. It is used as a soldering flux that is contained as an agent.

[0010]

[Chemical 25] [R is, -COCH _3, -NHCOCH _3, -OCOC
H _3, represents -NH _2, -OH, a -COC ₆ H _5. )

[Chemical formula 26] [R is, -CONHCH _2, represents a -C ₂ H _2. )

[Chemical 27] [R represents -OCH _3, -NHNH _2, to -OH. )

[Chemical 28]

[Chemical 29]

[Chemical 30]

[Chemical 31]

[Chemical 32] [R is, -H, represent -OCH _3. )

[Chemical 33]

[Chemical 34]

[Chemical 35]

[Chemical 36]

[Chemical 37]

[Chemical 38]

[Chemical Formula 39]

[Chemical 40]

[Chemical 41]

[Chemical 42]

[Chemical 43]

[Chemical 44]

[Chemical formula 45]

[Chemical formula 46]

[Chemical 47]

[Chemical 48]

The soldering flux according to the present invention contains 0.3 to 15 wt% of such an activator.

The carboxyl group of the carboxylic acid has a function of activating at the soldering temperature and reacting with the oxide on the surface of the joining metal to remove the oxide. Since the flux according to the present invention uses, as an activator, a carboxylic acid having a monocyclic structure, a polycyclic structure, or an ester bond structure as described above, it can be polycarboxylated and thus has excellent activity. Become. Moreover, since such a structure is similar to that of abietic acid, which is the main component of rosin, it has a property of being easily dissolved in rosin. In other words, it is very easy to get used to rosin,
Therefore, the residue becomes a uniform matrix.

Further, as is clear from the structure, the carboxylic acid having a monocyclic structure, a bicyclic structure or an ester bond structure as described above has a very low solubility even in the presence of water. Therefore, the flux using such an activator has excellent electrical insulation properties and is unlikely to cause current leakage or migration. Furthermore, even if it becomes a residue, it is difficult to generate copper soap or to cause whitening.

The reason why the content of the activator is 0.3 to 15 wt% is that if the content is less than 0.3 wt%, the soldering is not performed, and if it exceeds 15 wt%, precipitation or separation of the activator occurs. is there. The preferable content of this activator is 1 to 5 wt%.

[0015]

EXAMPLES Examples of the activator of the soldering flux according to the present invention will be shown below. -2-Acetylbenzoic acid-o-acetylaminobenzoic acid-acetylsalicylic acid-anthranilic acid-salicylic acid-o-benzoylbenzoic acid-hippuric acid-t-cinnamic acid-p-anisic acid-p-hydrazinobenzoic acid-p- Hydroxybenzoic acid, 2-methoxyphenylacetic acid, hydroxyphenylacetic acid, pyromellitic acid, m-toluic acid, vanillic acid, syringic acid, 2,4 dihydroxybenzoic acid, 2,6 dihydroxybenzoic acid, 2-hydroxy-3-naphthoic acid Acid 1-naphthoic acid biphenylcarboxylic acid 2-naphthoxyacetic acid 1-oxy-2-naphthoic acid 1-naphthylacetic acid biphenyl-2,3'-dicarboxylic acid salicyl salicylate N-phenylanthranilic acid 2 -Phenoxymethylbenzoic acid-p-toluyl-o-benzoic acid - N, N'-dibenzylethylenediamine diacetate diethylamino hydroxybenzoyl benzoic acid aniline phthalate

Each of the above activators was examined for electrical insulation and solderability. That is, a flux containing 3 wt% of any of the above activators, 3 wt% of gum rosin, and 94 wt% of isopropyl alcohol was added to JI
Apply to a 2 type comb substrate defined in S Z 3197, and
After heating at 00 ° C. for 30 minutes, the insulation resistance value after 176 hours under the condition of 50 V _{DC in} an 85 ° C./85% RH chamber was measured using a silometer (manufactured by Alpha Metals). At the same time, after soldering was performed using an automatic soldering device, the solderability was examined by an appearance test of icicles, bridges and the like. The results are shown in Table 1.

[0017]

[Table 1]

As is clear from Table 1, the activator according to the present invention has a practically sufficient performance in electrical insulation and solderability even when compared with the comparative examples adipic acid, succinic acid and glutaric acid. I understand.

[0019]

As described above, since the soldering flux according to the present invention uses a carboxylic acid having a monocyclic structure, a polycyclic structure or an ester bond structure as an activator, it can be polycarboxylated. Therefore, it has high activity. Therefore, the amount of rosin used can be reduced, which is advantageous in cost. Also, these activators have an advantage that they are excellent in electrical insulation because they are very little dissolved in water for the same structural reason, and they are less likely to cause current leakage and migration.

Further, the soldering flux according to the present invention can be used as a non-cleaning flux because it is unlikely that the soap is produced or whitening occurs even when it remains as a residue. Therefore, it can be used for soldering electronic parts and precision parts that are weak in cleaning, and the reliability of the joint can be improved. Furthermore, since it is not necessary to perform cleaning after soldering, it is not necessary to use a cleaning agent that may adversely affect the environment or to process a used cleaning agent, which is advantageous in terms of environmental hygiene. The cleaning cost can be reduced.

Claims (2)

[Claims] 1. A soldering flux containing a carboxylic acid as an activator, which comprises as an activator one or more compounds selected from the group consisting of compounds represented by the following formulas: Flux for soldering. [Chemical 1] [R is, -COCH _3, -NHCOCH _3, -OCOC
H _3, represents -NH _2, -OH, a -COC ₆ H _5. ) [Chemical 2] [R is, -CONHCH _2, represents a -C ₂ H _2. ) [Chemical 3] [R represents -OCH _3, -NHNH _2, to -OH. ) [Chemical 4] [Chemical 5] [Chemical 6] [Chemical 7] [Chemical 8] [R is, -H, represent -OCH _3. ) [Chemical 9] [Chemical 10] [Chemical 11] [Chemical 12] [Chemical 13] [Chemical 14] [Chemical 15] [Chemical 16] [Chemical 17] [Chemical 18] [Chemical 19] [Chemical 20] [Chemical 21] [Chemical formula 22] [Chemical formula 23] [Chemical formula 24] 2. The soldering flux according to claim 1, which contains 0.3 to 15 wt% of an activator. [0001]