Factors Affecting the Quality of Coating in Gravure Printing

In actual production, the factors affecting the quality of the coating summarized by everyone mainly include the following aspects, which should be analyzed, studied, and controlled.

(1)   Composition of the Electrolyte

The electrolyte consists of simple salts, which usually results in a rough electroplated layer because the formation of crystallization nuclei is slower than the growth of crystals. To obtain a dense electroplated layer, the concentration of salts (CuSO4) in the electrolyte can be increased, and the current density can be raised.

(2)   Purity of Anode Metal

Metals containing impurities will precipitate a lot of residues during the electrolysis process, and these residues adhere tothe anodemetal surface, which slows down the electrolysis speed. Therefore, the anode metal (electrolytic copper ball) with good solubility should have a dense structure and contain as few impurities as possible.

(3)   Temperature of the Plating Solution

Increasing the temperature of the plating solution can enhance the dissociation degree of salts (Cu²⁺·SO₄^2-) and improve the conductivity of the electrolyte, which will promote the formation of a rough coating structure. However, if the solution temperature is increased along with the current density, a dense electroplated layer will form. If the temperature is too low, it is easy to produce pinholes, and burrs are likely to occur at both ends of the roller; if the temperature is too high, the copper layer becomes soft, affecting the electro-engraving. Therefore, in production, it is essential to strictly control the temperature within the optimal range (40±1℃).

(4)   Current Density

Increasing the current density can improve the deposition of metals, but it will also consume the solution near the cathode plate (roller), causing the concentration of metal ions near the cathode plate to become insufficient. The decrease in metal ion concentration will promote the structure of the coating to become dense, but if the current density is increased without sufficient stirring of the solution or if the temperature is too low, it will lead to uneven or rough coatings. If the current density is too high, the formed coating will have an increased hydrogen content, resulting in brittleness or excessive hardness.

(5)   Concentration of Hydrogen Ions and Properties of the Cathode

During the electroplating process, the acid anions are continuously consumed, and due to the different diameters of the rollers, hydrogen precipitation may occur to varying degrees. The precipitated hydrogen will adhere to the copper layer, making it brittle. By increasing the pH value, temperature, and current density of the solution within the normal process specifications, the precipitation of hydrogen and its negative impact on the quality of the coating can be reduced. Additionally, the quality of the coating is also affected by other factors such as solution capacity, circulation rate, filtration, and the distance between the anode and cathode. In the copper plating process, only through accurate analysis of various chemical and physical factors, proper record-keeping, and optimal matching of various elements can high-quality gravure printing rollers be produced.