When a metal electrode has both cathodic and anodic reactions, the metal electrode is called an amphoteric electrode. The phenomenon that the anode and the anode react simultaneously on two different surfaces of an amphoteric electrode is called a bipolar phenomenon.
The simple principle is as follows (taking the most common copper plating as an example): in the electrolytic cell, the current flows from the metal (anode copper ball) into the electrolyte (plating solution) as the anode, and the electrode from which the current flows into the metal from the electrolyte is the cathode. (In fact, in electrochemical theory, the technical terms are the first type of conductor (for example: metal) and the second type of conductor (for example: electrolyte). If an anode and an anode are placed in the electrolytic cell, they are not connected to an external power source. (Rectifier) The connected metal A separates the electrolytic cell into two cells, so the current between the cathode and the anode cannot completely flow from the anode to the cathode through the electrolyte, and must be borrowed from A. "Therefore, when the current from the anode reaches the surface of A At this time, a cathodic reaction occurs on this surface (for divergence errors? A current flows from the electrolyte into the metal), and an anodic reaction occurs on the other surface of A (a current flows from the metal into the electrolyte). Therefore One side of the rising sun pole is coated with metal, while the other side of the metal A facing the cathode may be dissolved. The principle is so, in practice, according to electrochemical theory, a certain anode or cathode reaction must reach a certain level The electrode potential (not the voltage) is required to start the reaction.
Take copper plating as an example: Generally, a cathodic reaction (copper ions are reduced to a metal) will occur under a voltage difference of about 0.6V in acid copper plating. Assume that a titanium basket in the vertical plating bath has a resistance due to poor contact with the conductive copper bar, so there will be a potential difference between this titanium basket and the two adjacent titanium blues, as long as this potential difference exceeds a certain value At this time, the titanium blue becomes A in the above, and becomes a bipolar electrode. The titanium blue facing the wall is copper plated, while the anode facing the cathode.
Countermeasure: Understanding the above principle, it is very simple to solve this problem: ensure that all anodes are at a uniform potential height relative to the cathode. That is, one end is grounded, and the other end measures each point of the anode. Application and PCB electroplating copper, this problem mostly occurs on the anode-titanium blue.
Therefore, the following measures can be taken:
1. Clean the conductive copper bar and titanium blue hook to ensure good electrical connection between titanium blue and conductive copper bar.
2. Add copper balls in time to ensure close contact between copper balls and copper balls.
3. If the clamp of the cathode is not tight, and no voltage is applied to one of the substrates, the cathode (substrate) becomes a bipolar electrode. At this point the substrate will be dissolved a sector.
Yantai Yuntong Electroplating Co., Ltd., a professional manufacturer of electroplating in Yantai, was founded in 1991 and is headquartered in Muping District, Yantai City, Shandong Province. It specializes in surface treatment of various materials and has more than 30 years of professional electroplating experience. One of the larger surface treatment enterprises in Shandong Province has a high reputation in the province and domestic surface treatment industry.