Common Problems and Solutions of PCB Copper Sulfate Electroplating Process (3)

3. Electroplating Pits

There are many processes caused by this defect, from copper immersion, pattern transfer, to electroplating pretreatment, copper plating and tin plating. The main cause of copper immersion is the poor cleaning of the sinking copper hanging basket for a long time. During microetching, the pollution liquid containing palladium copper will drip from the hanging basket on the surface of the PCB board, causing pollution pits. The graphics transfer process is mainly caused by poor equipment maintenance and developing cleaning. There are many reasons such as the brush roller suction stick of the brushing machine contaminates the glue stains, the internal organs of the air knife fan in the drying section are dried, there is oily dust, the board surface is filmed or the dust is removed before printing improperly, the developing machine is not clean, the washing after developing is not good, the defoamer containing silicon contaminates the board surface, etc.

Pre-treatment for electroplating, because the main component of the bath liquid is sulfuric acid, whether it is acidic degreasing agent, micro-etching, prepreg, and the bath solution. Therefore, when the water hardness is high, it will appear turbid and contaminate the board surface. In addition, some companies have poor encapsulation of hangers. For a long time, it will be found that the encapsulation will dissolve and diffuse in the tank at night, contaminating the tank liquid. These non-conductive particles are adsorbed on the surface of the board, which may cause different levels of electroplating pits for subsequent electroplating.

4. The surface of the board is whitish or uneven in color.

The acid copper electroplating tank may have the following aspects: the air blast tube deviates from the original position, and the air is agitated unevenly; the filter pump leaks or the liquid inlet is close to the air blast tube to inhale air, generating fine air bubbles, which are adsorbed on the board surface or the edge of the line, especially at the side of the horizontal line and the corner of the line. Another point may be the use of inferior cotton cores, which is not completely handled. The anti-static treatment agent used in the production of the cotton core contaminates the bath and causes plating leakage. This situation can be added blow up, clean up the liquid surface foam in time. After the cotton core is soaked in acid and alkali, the color of the board surface is white or uneven. Mainly because of the polishing agent or maintenance problems, and sometimes it may be the cleaning problem after acid degreasing, micro-etching problem, misadjustment of the brightening agent in the copper cylinder, serious organic pollution, and excessively high bath temperature may all be caused.

Acidic degreasing generally does not have cleaning problems, but if the pH of the water is relatively acid and there are more organics, especially the recycled water washing, it may cause poor cleaning and uneven micro-etching. Micro-etching mainly considers excessive micro-etching agent content Low, high copper content in the microetching solution, low bath temperature will also cause uneven microetching on the board surface. In addition, poor cleaning water quality, longer washing time or contamination of the pre-soak acid solution may cause slight oxidation of the board surface after treatment. In the copper bath electroplating, because it is acidic oxidation and the plate is charged into the bath, the oxide is difficult to remove, and it will also cause uneven color of the plate surface; in addition, the plate surface is in contact with the anode bag, and the anode conduction is uneven. Anode passivation and other conditions can also cause such defects.

Concluding Remarks

Some common problems in the acid copper plating process summarized in this article. At the same time, the acid copper plating process is widely used because of its simple basic composition, stable solution and high current efficiency. Adding appropriate brighteners can obtain coatings with high brightness, high leveling properties and high throwing power. The quality of the acid copper plating layer depends on the choice and application of the acid copper brightener. Therefore, we hope that you can accumulate experience in daily work, not only to find and solve problems, but also to radically improve the level of craftsmanship in an innovative way.