Intaglio printing plate electroplating process - Copper plating: Configuration methods and process conditions of the plating solution


Release Time:

Jul 14,2017

1.  Method for preparing plating solution

First, dissolve the calculated amount of copper sulfate in warm water accounting for 2/3 of the total volume. Once the copper sulfate is completely dissolved and cooled, slowly add sulfuric acid while stirring continuously (the addition of sulfuric acid is an exothermic reaction). Let the plating solution stand and filter it, then add the specified additives. If the trial plating is qualified, it can be put into production.

 

2.Process conditions

(1) Current density (DK)

The current density is 15-18 A/dm2 when fully immersed in the drum, and 20-30 A/dm2 when partially immersed. Whether the current density can be increased depends on the composition of the plating solution and other conditions, such as: increasing the temperature of the plating solution, enhancing stirring, and having a higher concentration of the plating solution can all increase the working current density.

 

(2) Temperature

The plating solution temperature is suitable at 40±1℃ when fully immersed and 38±1℃ when partially immersed. If the plating solution temperature is too low, not only is the allowable working current density low, but copper sulfate is also prone to crystallization; if the plating solution temperature is too high, it can enhance the conductivity of the plating solution but will make the coating rough. If the plating solution temperature exceeds 45℃, the copper layer will soften and the surface will turn white.

 

(3) Copper plating time

The copper plating time should be determined based on the required hardness of the copper layer, generally ranging from 1 to 1.5 hours per tank.

 

(4) Anode in the copper plating tank

The anode is a phosphor copper ball with a diameter of 40mm, and the phosphorus content should be between 0.035-0.06%. Currently, domestic copper balls have a phosphorus content greater than 0.05%, while imported ones have only 0.038%, but they are too expensive. Phosphor copper balls often produce copper powder in sulfate copper plating solutions, leading to burrs and roughness in the coating. The phosphorus content of the copper ball should be appropriate and evenly distributed to reduce copper powder and avoid pinholes. If the phosphorus content of the copper ball is too high, a thick film will form on its surface, making it difficult for the anode to dissolve, resulting in a decrease in the copper ion content in the plating solution.

 

(5) Anode distance

The anode distance is 50-80mm.

 

(6) Plate roller speed

The plate roller speed changes according to the diameter of the plate roller, generally controlled at a linear speed of 0.8-1.2 m/s.

 

(7) Selection and use of hardness agents

Choosing the best hardness agent for electroplating performance based on the company's equipment conditions is an important step, as controlling the hardness of the copper layer mainly relies on adjusting the amount of additives in the plating solution.

 

Pulsar CompanyCopper plating additivesofJapanese original imported acidic fast electroplating hard copper additive KY-Z seriesis a good choice,its advantages include a long shelf life (up to over 1 year), easy hardness enhancement (up to over 220 HV), good brightness and leveling (can appropriately reduce copper thickness, saving copper balls and electricity), good positioning effect, high temperature resistance, and oxidation resistance.It is very suitable for the equipment and process conditions of domestic plate-making factories, has a high cost-performance ratio, and possesses a professional service team and technical research and development team, equipped with professional analysis and testing equipment, thus being favored by plate-making companies.

 

The ratio of copper plating solution and the amount of hardness additives must reach the best. Ensuring a balance between the brittleness and flexibility of the copper layer is key, as this can achieve the best hardness for the copper layer while extending shelf life and reducing usage. If the amount is too much, the copper layer will be too hard and brittle, easily worn and prone to burrs; if the flexibility is too strong, carving at 30° or 38° may easily produce burrs, and a scraper should be used during carving. The method to judge toughness is: the copper skin should be folded once without breaking, and then folded back and forth once, breaking after two folds is ideal.

 

Common problems in actual production are that the hardness of the copper layer is either too high or too soft, leading to instability. For example, if the sulfate ion concentration is low and the current is high, it results in high hardness, brittleness, and poor toughness, causing cracking over time; if the copper layer is too soft, it leads to deformation of the dots. Therefore, it is essential to achieve the best matching of various elements to balance the brittleness and flexibility of the copper layer and maintain stability, which relies on strict and careful management.

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