Views:0 Author:Site Editor Publish Time: 2021-08-10 Origin:Site
When a metal electrode has both a cathode reaction and an anode reaction, it is called a bisexual electrode. The phenomenon in which the cathode and anode reactions occur simultaneously on two different surfaces of the bipolar electrode is called bipolar phenomenon.
The simple principle is as follows (take the 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 where the current flows from the electrolyte into the metal is the cathode (in fact, In electrochemical theory, the technical term is one type of conductor (such as metal) and the second type of conductor (such as electrolyte). If a metal A that is not connected to an external power source (rectifier) is placed between the anode and cathode of the electrolytic cell, the If the electrolytic cell is divided into two cells, the current between the anode and the cathode cannot completely flow from the anode to the cathode through the electrolyte, and a channel must be borrowed from A." Therefore, when the current reaches the surface of A from the anode, the cathode reacts Occurs on the surface of A. The current flows from the electrolyte into the metal), and the anodic reaction occurs on the other surface of A (the current flows from the metal into the electrolyte). Therefore, the side of the electrode facing the sun is plated with metal, and the metal A facing the cathode The other side may dissolve. The principle is as follows. In practice, according to electrochemical theory, a certain anode or cathode reaction must reach a certain electrode potential (not voltage) before the reaction starts.
Take copper plating as an example: Generally, as long as the voltage difference is about 0.6V, the cathodic reaction (reduction of copper ions to metal) occurs in acid copper plating. Assuming that the titanium basket in the vertical electroplating bath has resistance due to poor contact with the conductive copper strips, there will be a potential difference between the titanium basket and two adjacent titanium blues. As long as the potential difference exceeds a certain value, titanium blue will change to the above-mentioned A and become a bipolar electrode. The titanium blue direction facing the partition wall is plated with copper, and the anode facing the cathode direction.
Countermeasure: After understanding the above principles, 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 whether each point of the anode is at a uniform potential. In the application of electroplated copper and printed circuit boards, this problem mostly occurs in the anode-titanium blue.
Therefore, professional and technical personnel tell you that you can take the following measures:
1. Clean the hook of the conductive copper bar and the titanium blue to ensure a good electrical connection between the titanium blue and the conductive copper bar.
2. Add copper balls in time to ensure close contact between the copper balls.
3. If the clamp of the cathode is not tight and voltage is not applied to one of the substrates, the cathode (substrate) becomes a bipolar electrode. At this time, the substrate will dissolve.