SU922186A1 - Electrolyte for depositing coatings from tin and cobalt alloy - Google Patents

Description

() ELECTROLYTE TO DEPOSE COATINGS FROM TIN-COBALT ALLOY

I /, , This invention relates to Hvans; : stegs, in particular, for electrolytic deposition of tin-cobalt alloy coatings for protective decoration; for the finishing of products instead of the chrome plating process and for the production of brazed mounting products, for example, printed circuit boards. / An electrolyte is known for precipitating well-soldered poke (eg tin-bismuth, the contents of tin tin and bismuth sulfates, sulfuric acid, fln-10 synthanol, brightener and formalin til. However, the sulfuric acid content in this electrolyte is high (120-160 g (l) and the instability of the tin-bismuth alloy in etchant solutions makes it impossible for the printed circuit boards to cover up, since it does not provide a reliable preservation of the photoresist during the deposition of the protective metal coating and ketalloresist during the etching process of the printed circuit boards. When the bismuth salt concentration in the electrolyte is so low (0,, 0 g / l), bismuth is replaced by electrolyte by metallic tin, the bismuth content in the alloy decreases, and this, in turn, decreases the capacity and leads to needle formation on the floor. The electrolyte has a low scattering capacity (% Ao %%. The electrolyte is relatively unstable electrochemically. It needs to be replaced after passing 70-100 A.h / l of electricity. This is a disadvantage, since tin salts are funded with 1 material. Tin-bismuth alloy coatings are not guaranteed after a year of storage. . The closest to the invention of the technical entity is an electrolyte for the deposition of coatings FROM a tin-cobalt alloy containing tin and cobalt chlorides, hydrochloric acid, sodium fluoride, the preparation OC-20 and water f2. However, although the ability to solder coatings obtained from a known electrolyte meets the requirements of the industry standard, the spreading rate of the solder dose; the coating (K), which determines JHOCTb soldering method, is relatively low, 9–1.2. . In addition, over time, compounds of tetravalent tin formed in a known electrolyte with sodium fluoride in the composition of ectrolyte are poorly soluble and impair the absorption and appearance of the coatings. The electrolyte is relatively difficult to prepare, has a low scattering capacity (5-50), which leads to a decrease in the content of cobalt in the holes of the printed circuit boards. This in turn causes deterioration of the coating capacity and needle formation during storage of printed circuit boards. The low pH of rolectrolyte (3.5 does not ensure reliable preservation of the photoresist during the deposition of a protective metal coating. Tin dichloride, which is part of the electrolyte, is a relatively deficient material. The aim of the invention is to increase the scattering ability of electrolyte and soldering ability This goal is achieved by the fact that the electrolyte containing salts of tin and cobalt, kineral acid, fluoride ions, is a surfactant and water, as salts of tin and cobalt, the mineral Noah, a source of fluoride ions and a surfactant, contains, respectively, tin and cobalt sulfates, sulfuric acid, ammonium fluoride and synthanol (primary fatty alcohols ethoxylated fraction) or syntamide (ethoxylated alkylamines) in the following ratio of components: tin sulfate, g 30-100 Cobalt sulfate, g 2-50 Sulfuric acid, ml I Ammonium fluoride, g 30-100 Sintanol or SintaWood, l In addition, the invention improves the allowable current density from 2 to A / dm. -4,5 , 15-25 ° C, current density 0.5-t using tin anodes of grade 01 or 02. To prepare the electrolyte, a prescription amount of sulfuric acid is added to a small amount of water and ammonium fluoride is injected. After the ammonium fluoride is dissolved, tin sulfate is introduced in small portions with stirring. Cobalt sulfate solution is gradually added to the solution containing the complex tin salt. After that, synthanol or syntamide, previously dissolved in a separate portion of hot water, is injected into the solution, and the pH of the electrolyte is adjusted with ammonia solution. In this solution, DS-10 synthanol or a mixture of syntamide 5 and syntamide 519 is used as a surfactant. silvery white, fine crystalline, uniform in thickness and composition of the coating. The deposition rate at a current density of 5 A / dm is µm / h. The content of cobalt in the alloy increases with an increase in the content of cobalt in the electrolyte, as well as with an increase in current density and temperature. The table shows the electrolyte compositions, the mode and the results of electrolysis. Note.

As can be seen from the table, the invention allows to significantly improve the ability of the coatings to be brazed, provides a long-term conservation of the supply of coatings.

The high scattering capacity of the proposed electrolyte (75-85%) ensures the constancy of the composition of the deposited coating both on the surface of the conductors and in the holes of the printed circuit boards.

Table continuation.

A higher pH value of the electrolyte allows coating of printed circuit boards without destroying the photoresist.

Claims (2)

 The introduction of ammonium fluoride instead of sodium fluoride into the electrolyte eliminates the formation of an insoluble sodium complex with tetravalent iono-mol and iso-mint, which contributes to the improvement of the coating and appearance of the tin-cobalt alloy coating. The scattering ability is determined in a slit cell of a Moler with a collapsible cathode, CL is the spreading coefficient determined by OSTC G0.05h, 089. The proposed electrolyte is capable of functioning after passing more than 250 A h / l of electricity, easily corrected by all components. The economic effect of introducing a tin-cobalt alloy coating is achieved in terms of replacing other metals, such as expensive and scarce silver. In the production with an annual program of 30,000 printed circuit boards per year, the economic effect from the introduction of an opaque-cobalt alloy coating is 50,000 rubles. in year. For example, when replacing a tin-lead coating with an alloy of tin-cobalt, the economic effect is achieved by reducing labor costs and time (by 1.5 hours per printed circuit board) for the fluxing operation, alloying and washing the flux. With the annual program ZODOO of printed circuit boards per year, the labor saving is iS.OQO h. When converted to the average wage of a worker, this value is about 50,000 rubles. per year at one enterprise and about 1 million rubles. per year at 20 enterprises. Electrolyte for precipitating a tin-cobalt alloy coating containing tin and cobalt salts, mineral acid, fluoride ions, a surfactant, and water, due to the fact that, in order to increase the electrolyte scattering ability and the soldering ability of coatings, as salts of tin and cobalt, mineral acid, a source of fluorine ions and a surfactant, cJH contains, respectively, sulfates of tin and cobalt, sulfuric acid, ammonium fluoride, and sintanol (ethoxylated primary fatty acids with Irta fractions C) or syntamide (ethoxylated alkylamines) with the following respectively | The components are as follows: Tin sulphate, r30-tOO Cobalt sulphate, r2-50 Sulfuric acid, ml5-15 Ammonium fluoride, r30-100 Sintanol or Sintamide, r1-10 Water , l Up to 1 Sources of information taken into account during the examination 1. OK Galdikene, A. Katkus. New sulphate electrolyte of brilliant tinning. - Modern methods of protecting metals from corrosion. Saratov, 1979, pp.16-17. 2. Koptev R.8, et al. Electrodeposition, add with an admixture of cobalt from chloride-fluoride electrolyte. Electrolytic coatings with alloys. M. 1975, pp.24-26.