SU1373739A1 - Method of preparing borohydrofluoric electrolyte for depositing tin-lead alloy coating - Google Patents

Abstract

The invention relates to the field of electrodeposition of alloys, namely to the preparation of a fluoride electrolyte for the deposition of a tin-lead alloy, and may find application in various fields of technology. The purpose of the invention is to increase the stability of the electrolyte. The method involves the preparation of tin boron fluoride by adding hydrofluoric acid in the tin hydroxide washed by decantation. Before the introduction of hydrofluoric acid into the washed tin hydroxide, a solution of hydroquinone with a concentration of 0.6-0.8 g / l is introduced. Tin hydroxide is obtained by mixing hydrochloric acid, stannous bicarbonate and sodium carbonate, with sodium carbonate being introduced in dry form in portions of 54 g / l. Lead fluoride is prepared by adding lead carbonate to hydrofluoric acid, and prior to introducing lead carbonate into hydrofluoric acid, it is mixed with a solution of boric acid with a concentration of 5-10 g / l. After mixing of the boron fluoride salts of tin and lead, additives DS-10 and DS-sodium are added. S (l

Description

The invention relates to the electro-deposition of alloys, namely to the rectification of a fluoride electrolyte for the deposition of a tin-lead alloy, and may find application in various fields of technology.

The purpose of the invention is to increase the stability of the electrolyte.

According to the preparation of a hydrofluoric electrolyte for the precipitation of a tin-lead alloy, tin fluoride and lead fluoride are prepared in advance:

In the preparation of tin boron fluoride, sodium chloride must be introduced with stirring into a solution of two tin chloride in acidified with hydrochloric acid in small amounts in small quantities in an amount of 5A g / l. As a result of the exothermic reaction, along with the formation of tin hydroxide, the tin ion is reduced to metallic, being a good antioxidant and better able to be washed off sodium and chlorine ions, which reduces the residence time of tin in the alkaline and neutral bHoi i environment that promotes the oxidation of bivalent tn tin to tetravalent. An aqueous solution of hydroquinone, which is a strong reducing agent, is prevented into the washed precipitate by introducing hydrofluoric acid, which prevents the oxidation of divalent tin to tetravalent one.

In the preparation of lead boron fluoride, the lead salt must be moistened with a solution of boric acid, which, preventing sharp fluctuations in the pH of the solution, prevents the decomposition and formation of lead fluoride, which precipitates.

The method of electrolyte preparation practically prevents the oxidation of bivalent tin to tetravalent and thus prevents the formation of methaolic acid and its derivatives, which precipitate outward, deplete electrolyte with tin and organic additives. In addition, lead fluoride is prevented from forming, which also precipitates, contributes to a change in the ratio of salts in the electrolyte and, consequently, in the ratio of metals in the alloy.

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Fluoride electrolyte for deposition of tin-lead alloy contains, g / l:

Two-tin tin45-48

Sodium carbonate 50-54 Acid salt on

(, 19), ml 36-38 Lead carbonate (basic) 18-20 Born acid 5-10 Acid boron hydrogen chloride (40%), ml 250-280 DS-10 additive (10%), m50-60

Additives DS-sodium (10%), ml 5-6 Hydroquinone 0.6-0.8 The invention is illustrated with an example.

.Example. The calculated amount of hydrochloric acid is introduced into the water bath and the calculated amount of tin dichloride is dissolved. Then, with stirring, sodium carbonate powder in an amount of 54 g / l is introduced in small portions, as a result of which a mixture consisting mainly of metallic tin, which is a good reducing agent, and tin hydroxide, which can be better washed, precipitates into the bottom of the bath. than pure tin hydroxide.

Then the bath is watered with water to the desired level, stirred, the pH is measured, settled and the solution is decanted by the method of decanting. Washing the precipitate is repeated several times until chlorine ions are absent. A solution of hydroquinone antioxidant at the rate of 0.6-0.8 g / l is introduced into the washed precipitate, carefully transferred and hydrochloric acid is added until hydroxide is completely dissolved. In another container, the calculated amount of carbon dioxide of lead is poured with a solution of boric acid at the rate of 5-10 g / l to a mushy state, and hydrofluoric acid is introduced, completely dissolving the lead salt. Combining both solutions and introducing des-percent solutions of additives DS-10 and DS-sodium, electrolyte is filtered through a chlorine filter.

into the working bath and left for processing. The introduction of hydroquinone below the indicated limits (below 0.6 g / l) is insufficient for antioxidant action. Increasing the concentration of hydroquinone (more than 0.8 g / l) due to the activation of redox reactions leads to large outgassing and anode corrosion.

The introduction of boric acid in the range (5-10 g / l) is sufficient to prevent decomposition of the yeast boron chloride during its preparation. In addition, this acid, together with boric acid, which is formed during the operation of an electrolyte from hydrofluoric acid, enhances the buffer properties of the electrolyte in pH.

The electrolyte prepared according to the method of the invention is stable, has a good scattering ability, it allows to obtain evenly thin crystalline coatings with good soldering ability, which is maintained for a year.

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Claims (1)

CLAIMS A method for the preparation of hydrogen borftoristo- electrolyte for depositing tin alloy coatings - lead comprising preparing borftoristogo stannous by administering fluoboric acid in washed by decantation tin hydroxide, the resulting displacement of hydrochloric acid, Risto dvuhlo- tin and sodium carbonate, and the preparation of lead borftoristogo by adding lead carbonate to hydrofluoric acid, mixing tin fluoride salts and lead, followed by the addition of DS-S and DS-nat In order to increase the stability of the electrolyte, upon receipt of tin hydroxide washed by decantation, sodium carbonate is injected in dry portions in an amount of 54 g / l, and before introducing hydrofluoric acid into the tin hydroxide washed by decontamination, the hydroquinone solution is injected 0,6-0,8 g / l, and before the introduction of carbon dioxide lead in bortoboric acid, it is mixed with a solution of boric acid concentration of 5-10 g / l.