DSA Titanium Anode
DSA technology maturity in the electrolysis industry DSA is used as an insoluble electrode, and the most widely used industry is the chlor-alkali industry. When preparing chlorine and caustic soda by electrolyzing salt water solution, the main reaction on the anode is the chlorine evolution reaction, and the side reaction is the oxygen evolution reaction. The use of RuTi-coated electrodes has minimal loss, greatly reduced chlorine evolution potential, stable size and shape, The generated chlorine bubbles are easy to escape and do not stay in the electrolyte. By the end of the 1980s, titanium electrodes for the chlor-alkali industry had more than 1×105m2 in Japan and more than 1×106m2 in the world. It can be said that the technology of applying DSA as an insoluble anode for electrochemical reactions is very mature in the world.
The technical feasibility of DSA in the PCB production process. For the electroplating process, most of the electroplating methods in the PCB industry currently use soluble anodes (dissolved anodes). Take copper plating as an example. The anode is composed of the anode mesh basket and the phosphor copper balls in the basket and the anode bag wrapped outside the basket. The cathode is the plated piece that needs to be plated with copper-circuit board, in the acid copper plating tank, the copper in the anode basket The ball continuously dissolves into Cu2+. When Cu2+ diffuses evenly to the cathode, it absorbs electrons, reduces to metallic copper, and deposits on the circuit board to form a uniform and bright coating. The main reactions at the yin and yang poles are as follows:
Cu— Cu2++2e-
Cu2++2e- 一 Cu
The use of this soluble anode has its advantages. For example, it can conveniently and continuously stabilize the copper ion content in the plating solution and reduce labor resources. However, it also has big defects: (1) The current density is very high, and high density is easy. Cause anode passivation and the formation of oxide film, so that the anode dissolution is too slow or stopped, forming an insoluble anode, generating oxygen, and excessive consumption of copper ions and other brighteners in the plating solution; (2) Soluble anodes generally contain 0.03% The purpose of adding 0.06% of phosphorus is to prevent the passivation and polarization of the high current density electrode, but the addition of phosphorus increases the production cost; (3) The use of this soluble anode will inevitably produce some anode mud , Causing a certain degree of pollution to the electrolyte, thereby affecting the quality of the plated parts: (4) The copper balls are not completely filled or the "bridging" occurs between the copper balls, and the protective titanium oxide layer on the inner surface of the basket will be damaged. Shorten the life of the titanium basket.
The new process of using insoluble anodes in PCB plating generally requires a Cu2+ supplement system to maintain the stability of Cu2+ concentration. With HDI (High Density Interconnect Board) copper electroplating, it is typical to add a copper regeneration tank containing copper balls in addition to the insoluble anode system. The copper is dissolved in the regeneration tank and then transported to the electroplating tank by a pump.
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