Effect of components in electroless copper plating solution of polyimide film
Sep 01, 2022
The copper salt is used to provide copper ions for electroless copper plating. The copper salt is selected from one or more of copper sulfate, copper chloride and copper nitrate.
Ascorbic acid or soluble ascorbate is the reducing agent of the electroless copper plating solution. Ascorbic acid or soluble ascorbate is non-toxic and environmentally friendly. It can reduce copper ions under neutral conditions. It is suitable for electroless copper plating on polyimide surfaces. Ascorbic acid or soluble ascorbate is selected from one or more of ascorbic acid, calcium ascorbate and zinc ascorbate.
The complexing agent is a variety of compounds that can complex with copper ions. This product has no special requirements. For example, it can be selected from one or more of citric acid, soluble citrate, tartaric acid, soluble tartrate, malic acid, soluble malate, ethylenediaminetetraacetic acid and soluble ethylenediaminetetraacetate.
The metal catalyst is a water-soluble salt containing nickel, and the addition of the metal catalyst can effectively improve the adhesion of the coating. The metal catalyst can be one or several of white nickel sulfate, nickel chloride and nickel acetate.
The addition of stabilizer can reduce the spontaneous decomposition of electroless copper plating solution, effectively improve the stability of electroless copper plating solution, and also adjust the plating rate. It can brighten the copper deposit and obviously improve the quality of the coating. The concentration of stabilizer in the electroless copper plating solution shall not be higher than 50mg/L, so as not to reduce the plating speed due to excessive stabilizer, or even prevent the deposition reaction of copper on the surface of polyimide film during electroless plating. The stabilizer can be selected from one or more of 2,2 '- bipyridine, potassium ferrocyanide, phenanthroline and its derivatives, mercaptosuccinic acid, dithiosuccinic acid, thiourea, mercaptobenzothiazole, and mercapto diacetic acid.
PH buffers are all kinds of buffers known to those skilled in the art. The addition of pH buffer can effectively hinder the change of pH of electroless copper plating solution due to a small amount of added acid and alkali. The boric acid buffer is preferred.
According to the provided electroless copper plating solution, the electroless copper plating solution also contains a surfactant. Surfactant can help the bubble escape from the surface of polyimide film and reduce the porosity of the coating. The surfactant is a variety of common surfactants, for example, one or several of which can be selected from sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, sodium n-octyl sulfate, and polyoxyethylene surfactants. The concentration of surfactant is 0.05-29 / L.
In the electroless copper plating solution, the pH value of the electroless copper plating solution is 5.5~8.0. The pH value of the electroless copper plating solution is adjusted by a conventional method, for example, by adding an acid-base regulator. Acid base regulators are various acids and bases, such as sulfuric acid, hydrochloric acid, phosphoric acid, sodium hydroxide, potassium hydroxide or ammonia.
