PCB circuit board copper plating protector layer

The copper layer is electroplated with a copper-plating protectant. It is not easily oxidized in the air. It is extremely easy to oxidize when not used. The reason is that it is easily oxidized and loses its luster. The copper is soft and easy to activate, and it can form a good metal with other metal plating. - Intermetallic bonding to achieve good adhesion between the coatings. Therefore, copper can be used as the bottom layer of many metal electrodepositions, and copper plating plays an important role in the production process of printed boards. Copper plating of printed circuit boards includes electroless copper plating and electroplating copper, among which electroplating copper is an important process in PCB fabrication. The article mainly introduces the process technology of electroplating copper, the technical problems that should be paid attention to and the causes and treatment schemes of some common faults.

    Measures to eliminate such failures include: controlling the proportion of brightener in the bath by the Hall test or by looking at the condition of the workpiece; do not 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 areas in the low current density region, and the complex parts will be embossed. When the brightener is less bright, consider whether it is too much. At this time, if a small amount of hydrogen peroxide is added and the brightness is increased, part of the brightener should be disposed of. For any electroplating additive, we must adhere to the principle of less addition and diligence.

    Brighteners have many components (such as M and N type copper plating), and it is necessary to accumulate the appropriate brightener distribution ratio in long-term production practice. Experience has shown that the ratio of open-cylinder and supplement of bright copper plating is very strict. The consumption of sodium polydithiodipropane sulfonate in the plating solution is different at different bath temperatures, and the ratio of consumption of M to N is also different. To obtain a universal supplement ratio, only the ratio of 25 ° C to 30 ° C can be considered. The most ideal situation is to prepare a variety of brighteners into standard dilute solutions, and use the Hall slot for experimental adjustment.

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

    Accumulation of the decomposition products of the brightener in the plating solution may result in poor brightness and flatness of the plating layer and no bright current density region. When it is found that the same proportion of brightener is used at a similar bath temperature, the consumption is much higher than the normal value, and it is suspected that the organic impurities are excessive. There are too many organic solvents, and there is no copper powder in the plating solution; however, copper powdery precipitates with poor adhesion are deposited on the plating layer. The organic impurities in the bath should be treated at this time. In addition, do not neglect the adverse effects of organic impurities on the brightness of low current density regions. The sensitivity of currents to organic impurities is particularly strong. It has been proved that the long-untreated bright copper plating solution uses 39/L high-quality activated carbon to adsorb organic impurities, and the full-light range of the low current density region of the Hall slot test piece may extend by several millimeters.