JPS6020470B2 - Tin or tin alloy stripper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stripping solution for tin or tin alloys, and more particularly, the present invention relates to a stripping solution for tin or tin alloys, and more particularly, to remove tin or tin alloys from a copper substrate by a concentrated dissolution method or a spray method without damaging the substrate. tin or tin alloy that can be selectively peeled off in a short time and also prevent the formation of white precipitates and the measling that is currently seen when tin or tin alloys are peeled off in the manufacture of printed wiring boards. This relates to stripping liquid.

Conventionally, solder deposited on a copper substrate, such as a printed wiring board, by electrolytic solder plating on a copper plate is processed using an aqueous solution containing, for example, hydrofluoric acid and hydrogen peroxide. Although it is removed by dripping, such a stripping solution is not suitable for stripping solder on a slope of printed wiring because the amount of copper dissolved is not small due to the action of the acid.

Also, a mixed aqueous solution of hydrogen peroxide and acid is used to strip tin or tin alloy from a copper substrate, but when treated with this stripping solution, after the tin or tin alloy is stripped, the tin is re-coated with copper. It has a tendency to precipitate on top and form a film-like white precipitate. Therefore, in order to remove the redeposited white precipitate, an additional peeling operation such as brushing is required, resulting in a disadvantage that the peeling process becomes complicated. In addition, a large amount of white precipitate is produced during long-term operation. In addition, stripping solutions containing fluoride are also used to prevent the formation of this white precipitate, but fluoride generally corrodes glass, and this is especially true in the manufacturing area of printed wiring boards. When a steel substrate is treated with a stripping solution, the epoxy glass cloth substrate is severely damaged and causes measling. Chromic acid and the like are also used as other stripping solution components, but these components generate toxic substances, require a large amount of equipment and expense to prevent pollution, and are unfavorable in terms of environmental hygiene.

Since the stripping solution according to the present invention has ordinary inorganic acids and/or organic acids as its main components, it can prevent the formation of precipitates that occur during long-term operation, and by adding a silicon compound, it can be compared with conventional stripping solutions containing fluorine ions. Defects such as measling and glass corrosion caused by this are improved, and tin or tin alloys are quickly melted. In addition, it contains a double cyclic compound that does not contain a sulfur atom but contains a nitrogen atom in the form of =NH or 3N as a ring member, and this compound is adsorbed on the copper surface to form copper. The dissolution of tin ions and the redeposition of tin ions to the copper surface can be prevented, and the oxidation of copper can be prevented. The present invention improves the conventional drawbacks as described above and provides an acid stripping solution suitable for stripping tin or tin alloy from a steel substrate without damaging the substrate.

The stripping solution of the present invention is composed of the following components.

The first component of the stripping solution of the present invention is a fluorine-containing ion, such as a shelf-hydrofluoride ion (BF4-), a fluorotitanate ion (TiF62-), a fluoride cirate ion (S
iF62-), fluorinated aluminate ion (YamaF63-)
etc.

The fluorine-containing tsuba ions stabilize the dissolved tin ions and quickly strip off the tin or tin alloy due to the interaction with the acid.

Tin or tin alloys can be dissolved in acidic solutions alone, but the reaction is extremely slow and is not of practical use. The concentration of the fluorine-containing rust ions is preferably in the range of 0.1 to 350 evening/night, more preferably 3 to 250 evening/night in terms of the amount of fluorine.

If the fluorine-containing key ion is used at less than 0.1 m/s, the above effect cannot be expected, and if the fluorine-containing key ion is used at 350 m/s, no greater effect can be expected. The second component in the stripping solution of the present invention is a fluoride or a salt thereof as a suspending agent.

Although fluorine-containing bell ions alone have some effect in preventing precipitation, the effect is not fully satisfactory. The effect of the addition concentration of the second component is 0.05 to 150 fluoride/
It was found that the formation of white precipitate was significantly prevented.

Below 0.05 m/s, no white precipitate prevention effect is observed, and above 150 m/s, no greater effect can be expected and it is uneconomical in practice. Problems such as corrosion of equipment and deterioration of the working environment also occur.

Therefore, the concentration of the fluoride or its salt, which is an anti-settling additive, is preferably 0.05 to 150 m/m. The third component in the stripping solution of the present invention is a citric acid compound as a measling or glass corrosion inhibitor, such as citric acid and its salts, hexafluorosilic acid and its salts, and the like.

The concentration of the third component to be added is at least 0.001 m/silicon, more preferably from 0.01 to 50 m/m/silicon.

If it is used at less than 0.001 m/s, the above effect cannot be expected, and if it is used at more than 50 m/s, no greater effect can be expected and it is uneconomical in practice, and on the contrary, a white precipitate is formed. This is inappropriate because the generation of

Examples of acids in the stripping solution of the present invention include inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid, and organic acids such as cyanoic acid, sulfamic acid, and citric acid. Either an acid that produces a solution or an acid that forms a precipitate once a solution is formed may be used.

Further, if the acid concentration is 0.1N or less, the dissolving power of tin or tin alloy cannot be practically expected, and if it exceeds 1QN, the dissolution will decrease. The component as a steel inhibitor in the stripping solution of the present invention is a double cyclic compound containing a nitrogen atom in the form of =NH or...N, which does not contain a sulfur atom and is soluble in an acidic solution. For example, pyrazole,
Examples include imidazoles, triazoles and derivatives thereof. The stripping solution of the present invention has a composition that is a combination of the above components, but in addition to the above components, other substances may be added.

For example, hydrogen peroxide, peroxide ions, and their stabilizers such as urea and alcohol can be added. As is clear from the above, the stripping solution of the present invention prevents the formation of precipitates and the corrosion of measling or galatas, and enables smooth stripping of tin or tin alloy over a long period of time. .

Further, the stripping solution in the present invention may be used by any method as long as tin or tin alloy can be removed. method can be used. Next, examples of the present invention will be shown. Example 1 Nitric acid 100%/Hydrofluoric acid 300% Inhibitor (e.g. imidazole) 10% Hydrogen peroxide
ammonium decafluoride
100 Katsura acid
50 water Add until the total amount becomes 1 night.

0 When a plate (solder thickness 10r) plated with solder containing 60% tin and 40% lead on an epoxy glass cloth base material patterned with steel was immersed in a stripping solution having the above composition at 40 oo, the solder was removed. It was completely removed from the board in 2 minutes.

After the solder was removed from the board, the patterned eboxy glass cloth substrate was continued to soak in the stripper solution for an additional 10 minutes. When the board was removed from the stripper and inspected, the copper surface was shiny. No abnormality was observed in the epoxy glass cloth base material either. Further, another solder-plated plate was continued to be dissolved in the stripping solution having the above composition until the amount of solder dissolved was 6.
After dissolving the solution until 50% of the solution was dissolved, the solution was allowed to stand for one day and the presence or absence of precipitate was examined, but no white precipitate was formed. On the other hand, when using a stripping solution without the addition of citrate, the amount of solder dissolution was 65 mm/min.
Although no white precipitate was formed even after dissolving until the
Measling was recognized. In addition, in order to check the corrosion of glass, a glass plate of 50 x 100 x 1.4 (skin) size (
14.750 mm) was soaked in the stripping solution of Example 1 at 4 mm for 1 hour, washed with water, dried, and then its weight was measured.

As a result, the weight of the glass plate was 14.737 mm, and it was slightly corroded by 0.013 mm.

On the other hand, after treating the same glass plate (15.200 mm) under the same conditions with the stripping solution of Example 1 without the addition of citrate, the weight was measured and the result was 14.397 mm. ,
It was found that the fish had been corroded by 0.803 ta due to fishing.

Example 2 Nitric acid 250/yet Hydrofluoric acid 200 Katsura Hydrofluoric acid? 0 inhibitors (e.g. imidazole) 10 weeks hydrogen oxide
1040% hydrogen fluoride
50 water Add until the total amount becomes 1 soybean.

When a solder plate plated under the same conditions as in Example 1 was immersed in the stripping solution at 40:00, the solder was completely removed from the plate in 1 minute and 3 seconds. After the solder was removed from the board, the epoxy glass cloth substrate was continued to soak in the stripper solution for an additional 10 minutes. When the board was removed from the stripper and inspected, the copper surface was shiny and no abnormality was observed in the epoxy glass cloth base material. Example 2 is a plate further plated with solder.
It continues to dissolve in the stripping solution with the composition of
After dissolution until evening/final time, no white precipitate was formed even if it was left to stand for one day. On the other hand, when no hydrofluoric acid was added, no white precipitate was formed even when the amount of solder melted reached 60 days, but measling was observed.

From the above, it was found that the addition of a silicon compound significantly suppresses the corrosion of glass and is sufficiently effective in preventing measling.

Claims (1)

[Claims] 1. The fluorine content of the fluorine-containing complex ion and fluorine ion is 0.1 to 350 g/l and 0.05 to 15 g/l, respectively.
0g/l, and silicon ion is 0.001g as silicon amount.
Acidic stripping solution for tin or tin alloy containing more than /l. 2 Fluorine-containing complex ions and fluorine ions have a fluorine content of 0.1 to 350 g/l and 0.05 to 15, respectively.
0g/l, and silicon ion is 0.001g as silicon amount.
An acidic stripping solution for tin or tin alloys in which a heterocyclic compound that does not contain sulfur atoms and contains nitrogen atoms in the form of =NH or ≡N as a ring member is added to an acidic solution containing at least /l. .