The effect of the fluorides and pH value of the electrolyte on the structure of copper coatings deposited onto aluminum

Abstract

The copper coatings were electrodeposited directly onto aluminum from the following solution: CuSO4-⋅5H2O (55 g/dm3) + CH2 NH2 - CH2OH (100 g/dm3) (NH4)2SO4 (30 g/dm3) + Na2SO4 - 10H2O (75 g/dm3) + Na2CO3 (3g/dm3), room temperature, current density j = 0.6 A/dm2 at pH = 10.3-8.5. It is shown in this paper that by lowering the pH value, the coverage of the base metal is decreasing and the coating is continuing its growth on the already created centers of crystallization. The fluorides in the form of NaF, concentration varying from 0.5 to 3 g/dm3, were added to the electrolyte for copper electrochemical deposition. Increasing the concentration of the fluorides the structure of the copper coating is changing; crystalline grains are larger, the coating is more porous and the coverage of the base metal is smaller, but the growth of the new layers of coating onto already existing centers of crystallization is more intense.

Prevlake bakra taložene su elektrohemijskim putem neposredno na aluminijum iz elektrolita sastava: CuSO4-5H2O (55g/dm3) + CH2 NH2 - CH2OH (100g/dm3) (NH4)2SO4(30g/dm3) + Na2SO4-10H2O (75g/dm3) + Na2CO3 (3g/dm3), temperatura sobna, gustina struje j = 0,6 A/dm2 i pri pH vrednosti 10.3 - 8.5. U radu je pokazano da sa smanjenjem pH vrednosti ispod 10.3 opada i pokrivenost osnovnog metala i da prevlaka nastavlja rast na već stvorenim centrima kristalizacije. U elektrolit za taloženje prevlaka bakra dodavani si fluoridi u obliku NaF u koncentraciji od 0.5 do 3 g/dm3. Sa povećanjem koncentracije fluorida menja se struktura prevlake bakra; kristalna zrna su krupnija, prevlaka postaje poroznija, pokrivenost osnovnog metala je sve manja, ali je intezivnije narastanje novih slojeva prevlake na već stvorevim centrima kristalizacije.