Electroless copper plating process of N, N, N′, N′-tetrakis (2-hydroxypropyl) ethylenediamine system with high plating rate

摘要

Electroless copper plating process of N, N, N′, N′-tetrakis (2-hydroxypropyl) ethylenediamine (THPED) chelating agent was researched comprehensively. The results indicate that plating rate decreases with the increase of concentration for THPED, CuSO_4 · 5H_2O and HCHO, pH value and bath temperature. The additive of K_4[Fe(CN)_6]·3H_2O, 2, 2′-dipyridyl and polyethylene glycol(PEG) decrease plating rate and K_4[Fe(CN)_6]· 3H_2O has a bad effect on deposits quality, but 2, 2′-dipyridyl and PEG make deposits quality improve greatly. Low concentration of 2-mercaptobenzothiozole (2-MBT) increases plating rate and improves deposits quality, but decreases plating rate and worsens deposits quality when 2-MBT reaches 5 mg/L. The optimal conditions of this electroless copper plating process are that the concentration of THPED, HCHO, CuSO_4 · 5H_2O, PEG, 2, 2′-dipyridyl and 2-MBT are 16. 8 g/L, 16. 0 mL/L, 13. 3 g/L, 0. 5 g/L, 5. 0 mg/L and 2. 0 mg/L, respectively, pH value is 12. 75, bath temperature is 30℃. Plating rate reaches 9. 54 μm/h plating for 30 min in the bath. The SEM images demonstrate that the surface of copper film is smooth and the crystal is fine.