PCB Technical - Copper plating protective agent layer of PCB circuit board​

The copper-plated protective agent layer of PCB circuit boards used by PCB manufacturers.

The copper plating layer is not so easy to be oxidized in the air with a copper plating protective agent. If it is not used, it is extremely easy to oxidize. Reason analysis is very easy to be oxidized and lose its luster. Copper is soft and easy to activate, and it can form a good metal with other metal plating. -Bonding between metals, so as to obtain a good bonding force between the plating. Therefore, copper can be used as the bottom layer of many metal electrodepositions, and copper plating occupies an important position in the manufacturing process of printed boards. Copper plating on printed circuit boards includes electroless copper plating and copper electroplating, and copper electroplating is an important process in PCB production. The article mainly introduces the process technology of electroplating copper, the operation technical problems that should be paid attention to and the causes and solutions of some common faults.

The measures to eliminate this type of failure include: control the consumption ratio of brightener in the plating solution by the Hall groove test or the condition of the workpiece; don't think that the more brightener, the better the brightness. When the brightener is excessive, there will be a clear boundary between bright and non-bright in the low current density area, and the coating of complex parts will be blurred. When the more brightener is added, the less bright it is, it is necessary to consider whether it is too much. At this time, if a small amount of hydrogen peroxide is added to the treatment and the brightness is increased, part of the brightener should be disposed of. For any electroplating additives, we must adhere to the principle of adding less and adding more frequently.

There are many brightener components (such as M, N type copper plating), and the appropriate brightener component ratio must be accumulated in the long-term production practice. Experience has shown that the ratio of bright copper plating starter and replenisher is very strict, the consumption of sodium polydisulfide dipropane sulfonate in the bath at different bath temperatures is large, and the consumption ratio of M and N is also different. To obtain a universal supplement ratio, only the ratio at 25°C to 30°C can be considered. The most ideal situation is to prepare standard dilute solutions for various brighteners, and frequently use Hall grooves for test adjustments.

Control the chloride ion content in the plating solution. If it is suspected that the failure is the cause of the chloride ion in the plating solution, test and confirm first. Do not blindly add hydrochloric acid to the large tank, etc., adjust and control the content of copper sulfate and sulfuric acid in the plating solution. Very important, and they are related to anode dissolution and anode phosphorus content.

The accumulation of brightener decomposition products in the plating solution will cause poor brightness and leveling of the coating, and the low current density area will not be bright. When it is found that the consumption of brightener with the same proportion under the conditions of similar bath temperature is much higher than the normal value, it should be suspected that there are too many organic impurities. Too much organic solvent, there is no copper powder in the plating solution; but copper powdery precipitates with poor adhesion will be precipitated on the plating layer. At this time, the organic impurities in the plating solution should be treated. In addition, do not ignore the adverse effects of organic impurities on the brightness of low current density areas. The sensitivity to organic impurities is particularly strong when the current is small. Practice has proved that the bright copper plating solution that has not been treated for a long time, with 39/L high-quality activated carbon alone to absorb organic impurities, the full brightness range of the low current density area of the Hall groove test piece may be extended by a few millimeters.