INFLUENCE OF THE COMPOSITION AND STRUCTURE OF HYDROXYLCONTAINING SURFACTANTS ON THE PROCESS OF ELECTROCHEMICAL TIN‒ BISMUTH ALLOY DEPOSITION

The possibility of electrochemical deposition of tin‒bismuth alloy with an increased tin quota which is in demand for microassembly in electronics was revealed. Modification of the acid EDTA electrolyte with hydroxyl-containing surfactants differing in the length of hydrocarbon chain and the number of hydroxyl groups provided the deposition of Sn–Bi alloys with tin content 36.0–63.0 wt.%. in the presence of 1,4-butyndiol (BD), and up to 80.0 wt.% using polyvinyl alcohol (PVA-10) or a product of processing a mixture of alkylphenols with ethylene oxide (OP-10). The reasons for different surfactants action were found. PVA-10 and OP-10, unlike BD, slow down the diffusion of Bi(III) ions by 3‒4 times. All surfactants accelerate the diffusion of Sn(II) ions, which is especially noticeable in the case of BD. This effect of BD is due to its complexation with Sn(II) ions instead of EDTA, as a result of which the diffusion of positively charged particles to the cathode is accelerated.