Do a good job of acidic bright copper plating, the influence of phosphorus content can not be ignored

The significance of the phosphorus content of 01 acid copper anode

The phosphorus content of acid copper anodes is mostly 0.1% in China. Foreign studies have shown that the phosphorus content in phosphorus copper anodes is more than 0.01%. There is a black film formation, but the film is too thin and the binding force is not good. The phosphorus content Too high, the black film is too thick, the anode sludge is too much, and the anode solubility is poor, resulting in a decrease in the copper content in the plating solution. The anode phosphorus content is preferably 0.03%-0.075%, and the best is 0.035-0.07%.

The domestic production equipment and technology are backward, the mixing is uneven, and the phosphorus content is not guaranteed to be evenly distributed. Usually increase the phosphorus content to 0.1-0.3%. Foreign countries use electrolysis or oxygen-free copper and phosphorus copper alloys as raw materials, and use intermediate frequency induction furnaces. Smelting, the purity of raw materials is high, and the phosphorus content is easy to control.

Using intermediate frequency induction, the magnetic stirring effect is good, the copper and phosphorus melting and stirring are uniform, and it is automatically controlled.

The copper anode produced in this way has uniform phosphorus distribution, uniform dissolution, fine crystals, fine grains, high anode utilization, which is conducive to smooth and bright coatings, and reduces burrs and rough defects.

02 The influence of phosphorus content on anode phosphorus film

1. Copper anodes with a phosphorus content of 0.03-0.075% form a black film with moderate thickness, compact structure, firm bonding, and not easy to fall off.

Copper anodes with too high phosphorus content before the danger. Phosphorus distribution is uneven, and the dissolution will cause too much anode mud, which will contaminate the bath solution and block the anode bag holes, causing the cell voltage to rise, which may cause The anode film falls off. In actual production, it is easy to produce burrs when the anode is replaced while electroplating.

2. Phosphorus copper anode with a phosphorus content of 0.1%, the phosphorus distribution will be uneven, the black phosphorus film is too thick, the solubility of copper is poor, so it is often necessary to hang the anode full, not to make the anode-to-cathode area ratio 1:1 .

A lot of copper anodes are actually hanging, and the copper content in the bath is still declining, and it is difficult to maintain a balance. It is necessary to add copper sulfate frequently. From the perspective of the cost of electroplating, it is also uneconomical. Inferior phosphor copper anodes and anode slime increase, and the actual cost will also increase.

3. In fact, the thickness of the black film produced by the copper anode with high phosphorus content is too thick, and the resistance increases. To maintain the original current, the voltage must be increased. The increase of the cell voltage is conducive to hydrogen ion discharge and the generation of pinholes. The odds increase.

This phenomenon is rare for the domestic “MNSP.P.AEO” system, because there are more surfactants, but for some imported light agents, the chance of pinholes will greatly increase, and the need In addition, add wetting agent and try to reduce the voltage.

4. In fact, the high phosphorus content, the thick black film and uneven distribution, will also cause the low-current area to be not shiny and fine grind-like. Although the thickness of the copper anode black film with a phosphorus content of 0.1% can reduce the entry of cuprous ions into the bath, the effect is greatly reduced due to its loose structure and uneven distribution.

Use copper anode with low phosphorus content. Because the black phosphorus film is dense, it is difficult for the cuprous force to dissolve into the bath. Just use air to stir and control the concentration of sulfuric acid not to be low, the current density is slightly higher, and the area is not bright. It can be overcome by tingling.

03 Change of anode during electroplating process

There are three changes in the anode as the current density increases during the electroplating process: 1. The anode dissolves when the anode potential moves in the positive direction. As the potential becomes positive, the metal dissolution rate increases.

2. When the limit current density is exceeded, the metal dissolution rate not only does not increase, but drops sharply, and the anode becomes passivated.

3. The upper plate of the electrode will produce other electrode reactions with the metal solution, such as hydroxide ion oxygen evolution at the anode, which will adversely affect the additives and the anode black film. Since the current is generally determined by the cathode plating, the only way to provide an appropriate anode current density is to adjust the anode area.