WO1991003355A1

WO1991003355A1 - Abrasive and water-soluble soldering flux

Info

Publication number: WO1991003355A1
Application number: PCT/JP1990/001125
Authority: WO
Inventors: Takehiko Kurashima
Original assignee: Nakajima All Precision Kabushiki Kaisha
Priority date: 1989-09-05
Filing date: 1990-09-03
Publication date: 1991-03-21
Also published as: JPH0394995A; AU6281690A

Abstract

Conventional water-soluble soldering fluxes include those prepared by dissolving a large quantity of a carboxylic acid in pure water and adding thereto a tin (II) compound, an air shielding agent, etc. They have, however, such a strong acidity that the residue of soldering becomes corrosive. The water-soluble soldering flux of the invention is prepared by dissolving at least one organic acid selected from among malic, tartaric, malonic and ascorbic acids in glycerol to solve the aforementioned problem. Part of the flux is esterified in the course of soldering or when heated during polishing to liberate water, which causes dissociation of the organic acid which exhibits a strong acidity to thereby enable polishing of a metal surface. On the contrary, when the temperature of the flux is lowered, the acidity is reduced to thereby reduce the corrosiveness of the residue as much as possible.

Description

Specification

Name of the invention

Abrasives and water-soluble solder flux

Technical field

The present invention relates to an abrasive and a water-soluble soldering flux which is non-polluting and has little residual corrosion.

Background technology

When soldering, remove the oxide film on the metal surface with a soldering flux.

A common solder flux is a rosin-based flux obtained by dissolving pine resin etc. in alcohol. However, in the case of electronic components, it is necessary to wash and remove the flux residue after soldering, but in the case of rosin-based flux, an organic solvent must be used for the cleaning solution, which is costly. Not only does this cause a rise, but it is also well known that when using the most frequently used cleaning fluid, the destruction of the atmospheric ozone layer has been pointed out.

Therefore, a water-soluble solder flux has been developed that can wash away the residue with water.

For example, in Japanese Patent Application Laid-Open No. 62-485696, thiourea is added to pure water in an amount of 2 wt% or more, divalent tin compound is added in an amount of 0.3 wt% or more, and carboxylic acid is added in an amount of 8 to 45 wt%. %, And a water-soluble solder flux containing l to 5 wt% of an air barrier agent is shown.

Examples of the above carboxylic acids include the use of lingic acid and tartaric acid, and the use of glycerin / polyethylene glycol as an air barrier agent.

With the above-mentioned water-soluble solder flux, new paper is used at the same time as cleaning the metal surface. In addition, since a tin film with good adhesion is formed on the metal surface, there is an advantage that soldering with excellent adhesion can be performed.

However, the present inventor has studied and found that the above-mentioned conventional water-soluble solder flux has the following problems.

That is, since a large amount of carboxylic acid is dissolved in pure water, the acidity is strong and the residue after soldering is corrosive. Decreasing the amount of carboxylic acid reduces the corrosiveness, but naturally reduces the reducing power and reduces the function as a solder flux. Solder flux is usually heated and used. However, the above-mentioned conventional water-soluble solder flux is solidified when cooled after heating, and cannot be reused because it does not melt even when reheated. Therefore, it is considered that the water-soluble solder flux of the leverage is used at room temperature without heating, but since it is inevitably heated at the time of soldering, the residue remaining on the metal surface solidifies after cooling, Although it is water-soluble, it has a problem that it is not easy to wash and remove and it takes a long time. In addition, since the tin compound is owned, there still remains a problem in the drainage treatment of the cleaning liquid.

Therefore, the present invention has been made to solve the above problems, and an object of the present invention is to provide an abrasive which is non-polluting, hardly corrodes residues, and is easy to wash and remove with water. Providing a water-soluble solder flux.

Disclosure and examples of the invention

The abrasive according to the present invention for the above object is characterized in that at least one organic acid selected from linoleic acid, tartaric acid, malonic acid or ascorbic acid is dissolved in glycerin.

Further, in the water-soluble solder flux according to the present invention, One or more organic acids selected from tartaric acid, malonic acid or ascorbic acid are dissolved in glycerin.

The viscosity of the above abrasive and water-soluble solder flux may be adjusted by adding a lower glycol such as ethylene glycol or isopropyl alcohol or a lower alcohol. Also, if necessary, a surfactant such as sodium lauryl sulfate is added. By adjusting the viscosity and adding a surfactant, the liquid drainage when used as an abrasive and the spread on a metal surface when used as a water-soluble solder flux are improved.

Lingoic acid, tartaric acid, malonic acid, and ascorbic acid are all solid at room temperature and are not easily dissolved when mixed with glycerin. In the present invention, after mixing dariserin and the organic acid, the mixture is heated to almost the melting point of the organic acid. As a result, the organic acid dissolves in glycerin. <Even if it is cooled to room temperature after heating, it remains in a liquid state.

The liquid prepared as described above exhibits a weak acidity of about pH 5 at room temperature, and shows almost no corrosiveness to metals. The reason that the organic acid is weakly acidic even when it has a large amount of organic acid is that water is not distributed as in the past. It should be noted that, since dalyceline has water absorbency, the weak acidity at room temperature is considered to be due to the slight dissociation of organic acids by the water absorbed by dalyceline.

However, when this liquid is heated, for example, when it is heated to about 230 ° C. for soldering, the PH becomes about 1 strongly acidic. Therefore, this liquid can be suitably used as a solder flux. When used as a soldering flux, heat the liquid to about 230 and apply it on a metal surface (or foam it and attach it to the metal surface). With this, It showed the same level of reducing properties as ox and was able to remove the oxide film on the metal surface. The soldering work was performed in exactly the same way as under normal conditions, and the solder was applied on the metal surface with good adhesion. This water-soluble solder flux is not compatible with solder, and after soldering, liquid material escapes around the solder attached to the metal surface.

Residues remaining on the metal surface dry and solidify when left for a relatively long time to form a non-conductive film on the metal surface, but are easily dissolved and removed by washing with water before solidification. You. Even if it is dried and solidified and remains in the form of a film, this film has little corrosiveness and does not show conductivity, so it is not always necessary to remove it even for electronic parts. In some cases, by leaving a film on the metal surface, it can also act as a protective film on the metal surface.

It should be noted that after the film is formed, it cannot be easily removed by washing with water.

The liquid material itself used as the soldering flux has a larger volume, so it stays liquid even after cooling after heating. Even if it hardens, it will easily become liquid if it is reheated and can be reused.

The above liquid material can also be used as an abrasive. In this case, the metal to be treated may be immersed in an abrasive heated to about 200 mm. Thus, the metal surface can be polished with a strongly acidic polishing agent. After polishing, the residue remaining on the metal surface may be washed away with water, or may be dried and surface-protected, leaving a protective film. The mechanism of the strong acidity of PH 1 when heated as described above is unknown. However, the organic acid and glycerin are partially esterified by heating, and the organic acid is dissociated by the released water. It is considered to be acidic. The mechanism of this esterification is complicated by the fact that linoleic, tartaric and malonic acids are dicarboxylic acids and glycerin is a trihydric alcohol. However, the formed ester is extremely unstable, is easily hydrolyzed as it is cooled, separates into organic acids and glycerin, and has a small amount of water. It is considered to be acidic and almost non-corrosive.

Ascorbic acid is not a carboxylic acid, but it forms a part of ester with dariserin at high temperature almost in the same manner as lingic acid, etc., and exerts its original strong reducing power due to liberated water and cools It is thought that the hydrolysis of the ester also progresses.

In the present invention, since water is not blended as described above, even if the amount of the organic acid is increased, it exhibits a weak acidity at room temperature even when the amount of the organic acid is increased, and shows little corrosiveness. Therefore, the amount of the organic acid can be increased with respect to glycerin, so that a sufficiently strong acidity can be exhibited at high temperatures. In order to obtain a strong acidity of about PH1 at a high temperature of about 150 or more, it is desirable that the amount of the above-mentioned organic acid to glycerin is 1 Owt% or more. When the amount of the organic acid to glycerin is about 5 wt%, the PH at high temperature is about 2 and the reducing power is reduced.

Although there is no particular upper limit on the amount of the organic acid, the limit is about 80 wt% in terms of solubility.

Table 1 shows the change in PH with temperature. Temperature-PH 2 0 4 0 6 0 8 0 100 Organic acid solvent • C • C • C • C • C: 5% by weight of sulfuric acid 4.5 4.5 4.5 4.5 4.0

"30 t% If 4.5 4.5 4.5 4.5 3.0

"50wt% 4.5 4.5 4.0 2.0 2.0 vs: iftt": 30wt% n 4.5 .4.5 4.5 4.5 4.0

'' Acetic acid 30wt% methanol ft 6.5 6.5 6.5 6.5

"30wt% water 1.0

As is evident from the table, glycerin in which lingoic acid and ascorbic acid are dissolved shows a weak acidity of about pH 4.5 at low temperatures, but PHI. It exhibits strong acidity of about 0.

On the other hand, those in which linoleic acid is dissolved in methanol and cooled after heating are considered to be almost esterified, are almost neutral at room temperature, and change in PH even when heated. Almost no reduction was observed, and no reducibility was shown. After heating and cooling, PH ? Does not fluctuate. In addition, if heated to more than 100ΐ, it will volatilize and will not withstand use.

A solution of linoleic acid in water shows strong acidity at room temperature. Although not shown in the table, similar results were obtained when tartaric acid or malonic acid was used in place of lingic acid or ascorbic acid. The same applies when these acids are used as a mixture.

Table 2 shows the applicable metals of the abrasive or the water-soluble solder flux of the present invention.

Example 1

Lingoic acid, tartaric acid, malic acid, ascorbic acid are mixed with glycerin, and the mixture is heated to near the melting point of each organic acid to dissolve the organic acid in glycerin, and then cooled to form a liquid. I got The proportions of organic acids to glycerin were 5 wt%, 10 wt%, 30 wt%, and 50 wt%.

Ethylene glycol was added to the above liquid material in an appropriate amount, for example, about 30 wt% to adjust the viscosity. The solder flux adjusted as above was dropped onto the oxidized copper plate, and a solder ring was placed on it and heated to about 230 ° C.The surface of the copper plate was reduced and cleaned. At the same time, the solder melted and adhered to the copper plate with good adhesion. The organic acid of 5 wt% had a little insufficient reducing power and was not sufficiently purified. After cooling, the residue of the solder flux was easily removed by washing with water.

Some of the samples were left unwashed with water, and a few days later, a film was formed on the copper plate surface due to flux residues. No corrosion of the copper plate surface due to the coating was observed. The skin could not be removed by washing with water.

Note that the same effect was obtained even when the solder flux liquid itself was heated back and forth by 230 and foamed, and this was adhered to a copper plate and used. Even when the solder flux was cooled, it remained liquid and could be reused.

The above liquid was also used as an abrasive. That is, when the liquid material was heated to about 200, and the oxidized copper plate was immersed therein, the oxide film could be polished. When the copper plate was pulled out of the solution and dried as it was, a film was formed on the surface of the copper plate. The coating was left as it was, but no corrosion was observed on the copper plate surface.

When about 1% by weight of sodium lauryl sulfate was added as a surfactant to the above solder flux, the spread on the copper plate was good.

When about 1 wt% of sodium lauryl sulfate was added to the above abrasive, the leakage to the copper plate was further improved. As described above, according to the water-soluble solder flux of the present invention, the following operation and effect can be obtained.

(1) Since it is a non-polluting flux, drainage treatment after substrate cleaning is easy,

(2) The residue is not corrosive because it is weakly acidic at room temperature.

(3) The viscosity can be easily adjusted with other organic solvents.

寿命 Flux has a long service life when stored at room temperature.

⑤ The solder surface is clean.

有する Has sufficient reducing power when soldering to copper.

⑦ By heating, a large amount of acid can be owned.

使用 Even once used, it can be used again after cooling.

Various types of metal surfaces can be polished as a polishing agent, and the polishing agent may be washed with water to remove the polishing agent, or may be left as it is and dried to form a protective film.

Claims

The scope of the claims

1. An abrasive made by dissolving one or more organic acids selected from linoleic, tartaric, malonic or ascorbic acid in glycerin.

2. The polishing agent according to claim 1, wherein the organic acid is dissolved in an amount of 1 O wt% or more and 80 wt% or less.

3. The abrasive according to claim 1 or 2, wherein a required amount of a lower glycol such as ethylene glycol or isoprovir alcohol or a lower alcohol is added for viscosity adjustment.

4. The polishing agent according to claim 1, wherein a surfactant such as sodium lauryl sulfate is added.

5. A water-soluble solder flux made by dissolving at least one organic acid selected from linic acid, tartaric acid, malonic acid or ascorbic acid in dariserin.

6. The water-soluble solder flux according to claim 5, wherein the organic acid is dissolved in a range of 10 wt% to 80 wt%.

7. A water-soluble solder foil according to claim 5 or 6, wherein a lower amount of low-density alcohol, such as ethylene glycol or isoprovir alcohol, is added to adjust the viscosity, or a required amount of lower alcohol is added. LUX.

8. The water-soluble solder flux according to claim 5, wherein a surfactant such as sodium lauryl sulfate is added.