JPH0890284A - Flux for soldering - Google Patents

Abstract

PURPOSE: To improve the spreading rate of solder and to enable soldering at a lower temp. by using 1-isopropyl-4-methyl-bicyclo[2,2,2]octa-5-en-2,3- dicarboxylic anhydride(IMA) as an essential component of a flux for soldering. CONSTITUTION: The flux is prepd. by incorporating the IMA consisting of a reaction mixture composed of p-mentadienes and maleic anhydride at 70 to 90wt.% into the flux. Flux activity is insufficient if the ratio thereof is <70wt.%. An isopropyl alcohol is added as the solvent into the flux. Residues are lower than with the rosin based flux. The m.p. is low and the flux has low sublimatability and, therefore, soldering is completed up to 200 deg.C and the heat history to be incurred on precision electronic parts, etc., is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soldering flux. More specifically, the present invention relates to a soldering flux having low residue and having wettability even in a low temperature range, which is used when soldering an electronic component or the like to a printed wiring board or the like.

[0002]

2. Description of the Related Art When soldering a joining metal to a metal to be joined, a flux is generally used. This flux is intended to remove the oxide film on the surface of the metal to be joined, reduce the surface tension, and improve the adhesion of the solder. Before soldering, the flux can be used to form a flux film by coating or dipping it on the surface of the metal to be joined, or by mixing the solder fine particles and the paste-like flux in advance so that it has an appropriate viscosity. Used as processed cream solder.

When the joining metal is a very fine portion such as an electronic part and the metal to be joined is a conductor portion of a printed wiring board, cream solder is generally used for soldering. Cream solder is used, for example, by applying cream solder to a conductor portion by screen printing or the like, installing leads of electronic parts on it and heating it, and then melting the cream solder to perform soldering. ing.

The above-mentioned conventional flux comprises a base resin such as rosin, an activator such as a halogen compound, a functional additive such as a thixotropic agent and an antioxidant, a mixture of a solvent and the like. Specifically, JP-A-5-391 and JP-A-5-80
81, JP-A-5-42388, and JP-A-5-6918.
No. 9, JP-A-5-185228, JP-A-5-2376.
88, JP-A-5-318169, and JP-A-5-318.
No. 176, JP-A-5-337687 and the like.

[0005]

With the recent miniaturization of electronic devices, the spacing between conductors (metals to be joined) of printed wiring boards has become finer. Along with this, more sophisticated flux is desired. However, the rosin contained in the conventional flux has the functions of both the base resin and the activator, and also has the property that residues easily remain after soldering. It has been pointed out that this residue causes insulation failure and hinders the checker pin inspection in the inspection process.

Furthermore, since the cleaning effect on the metal surface is not so high with rosin alone, the cleaning effect is enhanced by adding a halogen compound or an organic amine hydrogen halide as an activator, which enables good soldering. There is. However, the residue of these additives causes the deterioration of the insulating property by corroding the metal surface or absorbing moisture.

Conventionally, a halogen-based solvent such as Freon or trichlene has been used for cleaning the residue after soldering, but it is difficult to use it because it may cause environmental damage. Therefore, there is a demand for a flux that does not require cleaning after soldering. In addition, as another problem, the rosin-based flux had to be applied with a high temperature in order to obtain desired wettability and vaporize, but this application of a high temperature has a bad influence on precise parts arranged in high density. There is concern about giving. Therefore, there is a demand for a flux that can be soldered at a lower temperature.

[0008]

In view of the above problems, the inventors of the present invention have made earnest studies, and as a result, 1-isopropyl-4-methyl-bicyclo [has been conventionally used as a curing agent for epoxy resins or a raw material for agricultural chemicals. The inventors have found that 2.2.2] oct-5-ene-2,3-dicarboxylic acid anhydride is useful as a soldering flux, and have reached the present invention.

Thus, according to the present invention, 1-isopropyl-4-methyl-bicyclo [2.2.2] oct-5-
Provided is a soldering flux containing ene-2,3-dicarboxylic acid anhydride as a main component. The soldering flux of the present invention can be used in any field for household use or industrial use such as electronic and electric field.
In particular, the metal to be joined is a printed wiring board and the metal to be joined is an electronic component, which is effective when both are soldered.

1-Isopropyl-used in the present invention
4-Methyl-bicyclo [2.2.2] oct-5-ene-2,3-dicarboxylic acid anhydride (hereinafter referred to as IMA) has a melting point of about 60 ° C and a boiling point of 160 to 180 ° C / 3.
It is known to be a solid compound of Torr. The IMA can be obtained by an addition reaction of α-terpinene and maleic anhydride. As the reaction conditions, the conditions used in the known Diels-Alder reaction can be applied as they are. Regarding the reaction ratio, it is necessary to add maleic anhydride in an equimolar amount or more to α-terpinene. If necessary, a solvent such as n-heptane, benzene, toluene, xylene and cyclohexane may be added to the reaction system. The reaction temperature is in the range of 50 to 150 ° C, preferably 70 to 130 ° C. Further, in order to suppress side reactions in the reaction system, hydroquinone, methoxyquinone, quinone, pt-butylcatechol, 2,6-t-
It is preferable to add a radical inhibitor such as butyl-p-cresol in an amount of 0.01 to 20% by weight based on α-terpinene.

Α-Terpinene can be obtained by a known method, for example, isomerization reaction of turpentine oil under acidic conditions, α-pinene treated with concentrated sulfuric acid, oxalic acid dehydration of α-terpineol, linalool or It can be obtained by various methods such as treatment of geraniol with concentrated formic acid and heat treatment of sabinene, α-ferrandrene or limonene in the presence of dilute sulfuric acid. α-Terpinene has a boiling point of 173-175 ° C.,
The specific gravity (d ²⁰ ₄ ) is 0.837. This α-terpinene is industrially available. However, the available products have a purity of α-terpinene of 20 to 70% and contain non-conjugated double bonds such as terpinolene, 3-p-menthadiene, and 1,4-p-menthadiene as impurities.
It contains a compound that contains individual. However, since these impurities do not undergo the Diels-Alder reaction with maleic anhydride, they can be used as they are in the production of IMA, and the reaction mixture obtained can be purified to obtain IMA at a desired concentration. In the present invention, α-terpinene and its isomer terpinolene, 3-p-menthadiene,
Compounds containing two non-conjugated double bonds such as 1,4-p-menthadiene are collectively called p-menthadienes.

In the present invention, the main component is 70% IMA.
It is meant to contain at least wt%. Below 70% by weight,
Flux activity (oxidation resistance, wettability, etc.) cannot be sufficiently obtained, which is not preferable. Here, IMA is a reaction mixture of pure α-terpinene and maleic anhydride, or p-
The reaction mixture of menthadienes and maleic anhydride can be obtained as it is or at a desired concentration by purification such as distillation under reduced pressure. In addition, the components included other than IMA are:
Examples of the reaction by-products include unreacted α-terpinene and maleic anhydride, p-menthadiene polymers, p-menthadiene polymers, and a small amount of a compound of unknown structure. Here, even if pure IMA is used as the flux of the present invention, it has sufficient flux activity, but it is possible to obtain a better flux activity by containing a small amount of the reaction by-product.
It is obtained from the experimental results. Therefore, the flux of the present invention preferably contains 70 to 90% by weight of IMA,
Further, it is preferably 80 to 90% by weight.

When the purification is carried out by vacuum distillation, the flux for soldering according to the present invention containing IMA as a main component can be obtained by removing the substance that distills out at least up to 105 ° C./3 Torr. Further, when a flux having an IMA content of 90% is desired, 160 to 175
It can be obtained by collecting the distillate at ℃ / 3 Torr.

The IMA soldering flux of the present invention can be used satisfactorily as it is, but various functional materials and solvents which are usually blended with the flux may be added within the range not impairing the object of the present invention. Examples of the functional material include antioxidants, activators and thixotropic agents. Examples of the antioxidant include 2,6-t-butyl-p-cresol and the like. This antioxidant is flux 10
For example, 0.1 to 10 parts by weight can be added to 0 parts by weight.

Examples of the activator include hydrohalic acids such as ethylamine, diethylamine, triethylamine and aniline, benzoic acid, succinic acid, maleic acid, adipic acid, lactic acid, hydroxypivalic acid, dimethylolpropionic acid, citric acid and malic acid. , Organic acids such as glyceric acid, and amines such as diphenylguanidine and triethanolamine. This activator is flux 10
For example, 0.1 to 10 parts by weight can be added to 0 parts by weight.

Examples of the thixotropic agent include polyethylene glycol, hydroxyethyl cellulose, hydroxypropyl cellulose, castor wax, higher fatty acid amide and the like. This thixotropic agent can be added to, for example, 10 to 100 parts by weight with respect to 100 parts by weight of the flux. Examples of the solvent include alcohols such as isopropyl alcohol, butyl carbitol, and benzyl alcohol, esters such as ethyl acetate, hydrocarbons such as toluene, and ketones such as methyl ethyl ketone. Of this,
Preference is given to using isopropyl alcohol. This solvent is, for example, 1 part with respect to 100 parts by weight of the flux.
100 to 1000 parts by weight can be added.

The soldering flux of the present invention is a pre-flux for protecting a printed wiring board, a hot air leveler flux used for solder plating for protecting a printed wiring board, and a component for a printed wiring board. It can be used for any application such as post flux used when reflow soldering after mounting.
As the method for applying the soldering flux of the present invention, the method used in the conventional rosin-based flux can be used as it is, and for example, a screen printing method can be mentioned.

The soldering flux of the present invention can be made into so-called cream solder by adding solder powder. As the solder powder, a solder commonly used in this field can be used.
n-Pb type alloy, Sn-Pb-Bi type alloy, Sn-Pb
-A solder made of an Ag-based alloy or the like can be used. Further, the shape thereof may be a true sphere or an irregular shape. Further, the particle size of the solder powder may be, for example, 20 to 60 μm.

The addition ratio of the solder powder contained in the cream solder is 100 times the soldering flux of the present invention.
It is 500 to 1000 parts by weight, and particularly preferably 800 to 900 parts by weight, relative to parts by weight. Further, other functional materials and solvents may be added as long as the object of the present invention is not impaired.

[0020]

According to the present invention, 1-isopropyl-4-methyl-bicyclo [2.2.2] oct-5-ene-2,3
-Since it contains dicarboxylic acid anhydride as a main component, it has a good solder spreading rate, can be soldered at a lower temperature, and has less residue than the conventional rosin-based flux.

The content of 1-isopropyl-4-methyl-bicyclo [2.2.2] oct-5-ene-2,3-dicarboxylic acid anhydride in the soldering flux is 70 to 90% by weight. %, A soldering flux with less residue can be obtained. Furthermore, a flux containing 1-isopropyl-4-methyl-bicyclo [2.2.2] oct-5-ene-2,3-dicarboxylic acid anhydride as a main component is formed of p-menthadiene and maleic anhydride. It is conveniently obtained as a reaction mixture.

Further, by adding isopropyl alcohol as a solvent to the above flux, it can be used for various fluxes.

[0023]

【Example】

Production Example 783 g of maleic anhydride and 300 g of toluene are heated at 120 ° C.
It was heated to dissolve and then 3000 g of a p-menthadiene mixture (α-terpinene content 36.2%) was added dropwise. The reaction was carried out at the same temperature for 6 hours to obtain 4061 g of a crude reaction oil which was light yellow and transparent.

This crude reaction oil was distilled under reduced pressure using a Claisen distillation tube to remove components distilled out at 105 ° C./3 Torr to obtain 1681 g of a viscous product A.
This product A was found to have 12.4 g of 1-isopropyl-4-methyl-bicyclo [2.2.2] oct-5-ene-2,3-dicarboxylic acid anhydride measured by gas chromatography.
It contained by weight%. The product A solidified when left to stand.

2000 g of crude reaction oil obtained in the same manner as above was distilled under reduced pressure using a Claisen distillation tube to obtain 1
Collect the components that distill at 60-175 ° C / 3 Torr,
13.2 g of product B was obtained. This product B is 1-isopropyl-4-methyl- by gas chromatography measurement.
It contained 89.0% by weight of bicyclo [2.2.2] oct-5-ene-2,3-dicarboxylic acid anhydride.

Example 1 In order to measure the wettability of the soldering flux of the present invention, a spreading test was conducted by the following method. As a test piece, the surface was washed with isopropyl alcohol 0.3
An untreated copper plate of mm × 50 mm × 50 mm and a copper oxide plate whose surface was oxidized by heating the untreated copper plate in an electric furnace at 150 ° C. for 1 hour were used.

The solder used for the test is H60A-W.
1.6 filamentous solder (manufactured by Nippon Genma Co., Ltd .: specific gravity 8.5)
Was wound on a rod having a diameter of 3.2 mm, and one turn thereof was used. The weight of one turn was about 250 mg. Solder was placed on the test piece, and 50 mg each of rosin (WW grade: melting point about 130 ° C.) and the products A and B were heated in the ring of the solder and heated. A hot plate is used for heating, and the condition is to heat to 200 ° C in 4 minutes,
Then, when the power was turned off and allowed to cool, heating was performed to 240 ° C. in 5 minutes, and then the power was turned off and allowed to cool in two ways.

Regarding each of the obtained sample pieces, JIS-Z-3
The spread rate (%) of the solder was measured by the method specified in 197. That is, the height of the solder is set to JIS-B-7502.
It measured using the micrometer prescribed | regulated in 1 and calculated according to the following formula. Spread rate (%) = (D−H) × 100 / D (where D is the diameter (mm) when the solder used in the test is regarded as a sphere, and D = 1.24V ^1/3 V is the mass / specific gravity.
H is the height (mm) of the spread solder. The obtained results are shown in Table 1 below. It should be noted that the larger the spread rate is, the better the wettability is.

[0029]

[Table 1]

As can be seen from Table 1, at 240 ° C., the spreading ratio shows the same result as that of rosin, at 200 ° C., the spreading ratio is superior to that of rosin, and soldering can be performed at a temperature lower than the conventional temperature. I understood. Example 2 As a test piece, a 0.3 mm × 50 mm × 50 mm copper plate whose surface was washed with isopropyl alcohol was precisely weighed, and about 50 mg of a sample (rosin (WW grade: melting point about 130 ° C.)) and the above-mentioned product A were placed on it. And those in which B) was precisely weighed and placed were used. The test piece was heated on a hot plate to a set temperature, then turned off and allowed to cool. Measure the amount of residue of the sample on the test piece and reduce the amount of residue by%
The results are shown in FIG. In the figure, ○ indicates rosin, Δ indicates product A, and × indicates product B, respectively.

As can be seen from FIG. 1, the weight loss at 240 ° C. of the soldering flux of the present invention is the same as that of rosin. However, the weight loss at 200 ° C. is almost 100% in the present invention, while that of rosin is about 2%.
It was 5%, which was found to evaporate at a temperature lower than the conventional temperature and the amount of the residue could be extremely reduced. Example 3 Using SSC5200TG / DTA320 (manufactured by Seiko Denshi Kogyo) as an analyzer, rosin (WW grade: melting point about 130 ° C.) and the differential thermal analysis (DTA) and thermogravimetric analysis (TG) of the above products A and B I went. The measurement conditions were such that each sample was used in an amount of 10 mg and the temperature rising rate from room temperature (30 ° C.) to 500 ° C. was 10 ° C./min under an air flow of 200 ml / min. The obtained results are shown in FIG. In the figure, ○ indicates rosin, Δ indicates product A, and × indicates product B, respectively.

As can be seen from FIG. 2, since the soldering flux of the present invention evaporates at a temperature lower than that of rosin, it was found that the amount remaining as a residue during soldering can be extremely reduced. .

[0033]

The soldering flux of the present invention is 1
-Isopropyl-4-methyl-bicyclo [2.2.2]
Since octa-5-ene-2,3-dicarboxylic acid anhydride is the main component, the residue is lower and the solder spreading rate is better than that of rosin-based flux. Further, when a rosin-based flux was used, it was necessary to heat it to about 250 ° C. to complete the soldering, but the soldering flux of the present invention has a low boiling point and weak sublimation property, so that it is 200 ° C. Soldering can be completed by this time, and heat history given to precision electronic parts and the like can be suppressed. Further, since the soldering can be performed at a lower temperature than the conventional one, energy cost can be reduced. Further, since the soldering flux of the present invention has a sufficient soldering activity as it is, it is not necessary to add an activator or the like. Since the residue is low, it is easy to inspect soldering with a checker pin, and a non-cleaning flux can be realized. Further, since it is possible to prevent the appearance of the flux residue from being contaminated by the flux residue, it is possible to secure the commercial value. Furthermore, since we can provide non-cleaning flux,
It is not necessary to use CFC, which is a cleaning agent whose use is regulated.

Further, by containing 70 to 90% by weight of 1-isopropyl-4-methyl-bicyclo [2.2.2] oct-5-ene-2,3-dicarboxylic acid anhydride, solder with less residue can be obtained. A flux for attachment can be obtained. Furthermore, the flux containing 1-isopropyl-4-methyl-bicyclo [2.2.2] oct-5-ene-2,3-dicarboxylic acid anhydride as a main component is composed of p-menthadiene and maleic anhydride. It can be conveniently obtained as a reaction mixture.

Further, by adding isopropyl alcohol as a solvent to the above flux, it can be used in various fluxes.

[Brief description of drawings]

FIG. 1 is a graph showing a heating decrease curve of a soldering flux and rosin of the present invention.

FIG. 2 is a graph showing a thermal analysis curve (TG-DTA) of the soldering flux and rosin of the present invention.

Claims (4)

[Claims] 1. A soldering flux comprising 1-isopropyl-4-methyl-bicyclo [2.2.2] oct-5-ene-2,3-dicarboxylic acid anhydride as a main component. 2. The flux according to claim 1, which comprises 70 to 90% by weight of 1-isopropyl-4-methyl-bicyclo [2.2.2] oct-5-ene-2,3-dicarboxylic acid anhydride. 3. A flux containing 1-isopropyl-4-methyl-bicyclo [2.2.2] oct-5-ene-2,3-dicarboxylic acid anhydride as a main component comprises p-menthadiene and maleic anhydride. A flux according to claim 1 or 2 which comprises a reaction mixture with an acid. 4. The flux according to claim 1, further comprising isopropyl alcohol added as a solvent.