The chemical species and equilibria in electroless copper plating baths consisting of copper sulfate, EDTA, glycine, hexacyanoferrate and formaldehyde were investigated by visible-spectrum measurements at 25°C. Chemical species were mainly CuOHL
3-, CuL
2-, G
-, M
-, MG
2-, HMG
-, CuLG
3-, CuLfe
6-, fe
4-, L
4- and HL
3- at pH11.75∼12.50, where H
4L=EDTA, HG=glycine, HCHO+H
2O=HM and Fe (CN)
4-=fe
4-. Glycine and formaldehyde form condensation products such as HMG
-, resulting in a decrease in the concentration of free formaldehyde, but the concentration of M
-, the electrochemically active species of formaldehyde, increased in the high pH region. Three mixed-complexes were found in the solution: CuL
2-, and OH
- formed CuOHL
3-([CuOHL
3-] [H
+]/[CuL
2-]=10
-11.8, molar absorptivity ε
730=45); CuL
2- and G
- formed CuLG
3- ([CuLG
3-]/[CuL
2-] [G
-]=10
1.5, ε
730=45.5); and CuL
2- and fe
4- formed CuLfe
3-([CuLfe
3-]/[CuL
2-] [fe
4-]=10
1.2, ε
490=315). The concentrations of CuLG
3- and CuLfe
4- were considerably lower than the other Cu (II) -EDTA complexes.
抄録全体を表示