Spring copper plated

Low-concentration copper bath formula (base plating bath formula)

Coprous cyanide CuCN 20g/l

Sodium cyanide (sodium cyanide) NaCN 30g/l

Sodium carbonate (sodium carbonate) Na2CO3? 15g/l

pH 11.5

Temperature 40℃

Current efficiency 30~60%

Current density 0.5~1A/cm2

4.4.2 The formula of the concentration bath in copper

Coprous cyanide CuCN 60g/l

Sodium cyanide (sodium cyanide) NaCN 70g/l

Sodium hydroxide (sodium hydroxide) NaOH 10~20g/l

Free cyanide 5~15g/l

pH 12.4

Temperature 60~70℃

Current density 1~2A/dm2

Current efficiency 80~90%

4.4.3 Copper cyanide high concentration bath formula

Cuprous cyanide CuCN 120g/l

Sodium cyanide NaCN 135g/l

Caustic soda NaOH 42g/l

Brightener 15g/l

Free sodium cyanide) 3.75~ 11.25g/l

pH 12.4~12.6

Temperature 78~85℃

Current density 1.2~11A/dm2

Current efficiency 90~99%

4.4.4 Cyanide copper plating full potassium bath formula

Cuprous cyanide CuCN 60g/l

Potassium cyanide KCN 94g/l

Potassium carbonate 15g/l

Potassium hydroxide KOH 40g/l

Free potassium cyanide 5~15g/l

pH value <13

Bath temperature 78~85℃

Current density 3~7A/dm2

Current efficiency 95%

4.4.5 Advantages and disadvantages of electroless copper plating full potassium bath

High current density can also get gloss, coating, high conductivity

Wide gloss range brings out less loss

Good gloss, more expensive medicine

Good smoothing effect

4.4.6 Potassium sodium tartrate cyanide copper plating bath formula (Rochelle cyanide Buths)

Cuprous cyanide CuCN 26g/l

Sodium cyanide NaCN 35g/l

Sodium carbonate Na2CO3? 30g/l

Sodium potassium tartrate NaKC4H4O6‧6H2O 45g/l

Free sodium cyanide 5~10g/l

pH 12.4~12.8

Bath temperature 60~70℃

Current density 1.5~6A/d㎡

Current efficiency 50~70%

4.4.7 The role and influence of the components of the electroless copper plating bath

1. Main salt: NaCu(CN)2 and Na2Cu(CN)3 exist in two forms, and its functions are:

CuCN+NaCN=NaCu(CN)2? CuCN+2NaCN=Na2Cu(CN)3? Na2Cu(CN)3? 2Na + (aq) +Cu(CN)3-(aq) Na2Cu(CN)3? 2Na+ (aq ) +Cu(CN)3-(aq) Cu(CN)3-? Cu++3CN- Cu(CN)2-? Cu++2CN-

Because the ionization constants of copper complex ions Cu(CN)2- and Cu(CN)3- are very small, the cathode has a great polarization effect, making it difficult for copper to be replaced and precipitated. Therefore, copper can be plated directly on steel. The current efficiency is reduced, hydrogen is generated, and the plating output is reduced. The main salt has a great influence on the cathode polarization, and the increase of the main salt concentration can reduce the cathode polarization, help the anode dissolve, and prevent the formation of anode passivation.

2. Free cyanide, NaCN, KCN, help anode dissolve, prevent wrong salt precipitation, stabilize the plating bath. Too much content will deepen the polarization and produce a large amount of hydrogen and reduce the current efficiency.

3. Sodium carbonate prevents sodium cyanide from being hydrolyzed, reduces anode polarization and helps anode dissolution.

4. Caustic soda, reduce hydrogen ion concentration, increase conductivity, improve current efficiency and use of electricity

Flow density.