DSA-coated titanium electrodes for PCB use
(Dimensionally Stable Anode), a dimensionally stable anode, is a coated titanium anode that is regarded as one of the most important inventions in the field of electrochemistry in the 20th century. It is a metal-on-titanium (Ti) New Insoluble Electrode for Active Coatings Based on Platinum Group Metal Oxides. It replaces the traditional insoluble graphite anode with its outstanding advantages of corrosion resistance, little change in the polar distance, high catalytic activity and long service life. It is widely used in industrial production and widely used in chemical industry, metallurgy, electroplating, water treatment, environmental protection, Marine, cathodic protection and other fields.
Printed Circuit Board (PCB for short) is a basic component of electronic products and is also an important part of modern electronics assembly technology. Printed circuit board plating is built on the hole metallization of the pre-treatment, electroless plating, electroplating, stripping and other technology processes.
With the development of PCB industry, its pollution to the environment is equally inevitable. PCB production process on the environment pollution is mainly waste water, waste, exhaust and a waste, etc., these pollution exists, but also more and more serious. In this case, cleaner production has also been placed on the agenda.
Currently used electrochemical processing methods to deal with PCB industry wastewater, waste will not produce secondary pollution to the environment, the industry's favor. The DSA coated titanium anode, as the electrode in the electrolysis process, has broad application prospects in the PCB plating process and cleaner production due to its superior plating quality, small power consumption, stable size and electrode insolubility.
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DSA PCB in the production process of technical feasibility, for the plating process, the current PCB industry is the most used in the soluble anode (dissolved anode) of the plating method to the copper as an example, the copper The anode is composed of an anode basket and a phosphor bronze ball in the basket, and an anode bag wrapped in a basket. The cathode is plated with copper plating. In the acidic copper plating tank, the copper in the anode basket The ball is continuously dissolved into Cu2 +. When Cu2 + diffuses evenly to the cathode, electrons are absorbed and reduced to metallic copper, which is filed on the circuit board to form a uniform and bright coating. The main reaction of the yin and yang poles is as follows:
Anode: Cu-Cu2 ++ 2e-
Cathode: Cu2 + + 2e-Cu
The use of such a soluble anode has its advantages, such as the ability to stabilize the copper ion content of the bath in a convenient and continuous manner and reduce labor resources, but also has great drawbacks: (1) high current density requirements, high density will be easy Causing anode passivation and oxide film formation, so that the anode dissolution is too slow or stop, the formation of insoluble anode, resulting in oxygen, excessive consumption of copper ion plating bath and other brightener; (2) the soluble anode usually contain 0.03% Plus 0.06% phosphorus to prevent passivation and polarization of high current density electrodes, but the addition of phosphorus increases the production cost; (3) the use of this soluble anode inevitably produces some anode slime , Resulting in a certain degree of pollution of the electrolyte, thus affecting the quality of plating: (4) the copper ball is not fully filled or "bridged" between the copper ball, the protective titanium oxide layer of the basket surface will be damaged, Shorten the life of titanium basket.
The new process of using insoluble anodes in PCB electroplating generally requires the provision of a Cu2 + replenishment system to maintain the stability of the Cu2 + concentration. To HDI (High Density Interconnect Panel) copper plating, it is typical to add an additional copper regeneration tank to the anode system, dissolve the copper from the regeneration tank and transport it to the plating tank Go in.
Improve the quality of products: the use of insoluble coated titanium anode, is from the following three aspects to improve product quality: (1) for the plating surface distribution, largely depends on the anode conditions, when the anode is very Good maintenance, the result is acceptable, but the dissolution of the anode is easy to passivation, with the progress of the hourly plating, passivation is more obvious, making the distribution of the coating worse, the insoluble electrode does not exist this problem, Plating surface distribution will not be extended by the electroplating time worse, that is, to improve the quality of plating. (2) anode is not dissolved, there will be no anode sludge generation, and thus will not pollute the plating solution, coupled with the circulation of the electrolyte was filtered circulation, plating quality higher. (3) DSA-coated titanium anode is dimensionally stable. During the electrolysis process, the distance between the electrodes does not vary to ensure that the electrolysis operation is stable in the cell voltage. In the case of the DSA coating, a stable reaction system is provided for the bipolar electrodes, which help to improve the placing the quality of.
Increase economic benefits:
(1) After using DSA-coated titanium anode plating system, it does not need to use phosphor bronze ball, but instead utilize low-cost copper ball, and also can use the recycled copper in production to reduce the production cost and increase Economic benefits.
(2) adding ferrous sulfate to the plating electrolyte, the reaction of the anode becomes Fe2 + to form Fe3 +, thereby eliminating any oxygen escape at the anode surface and reducing the consumption of copper ions and other additives in the plating solution, Save costs.
(3) The working voltage of DSA anode is low, so the power consumption is insignificant, which can save the power consumption and reduce the production cost.
Strengthen the production management: the introduction of the new system, the following management advantages:
(1) The use of two separate systems greatly reduces the current density requirements. Extreme density current density does not cause passivation and oxide film formation on the surface of the copper ball, minus the regular cleaning of the phosphor bronze ball.
(2) two independent systems, there is no electrolytic sludge plating system, electrolyte management more convenient.
(3) The current use of anode bags, should be frequently cleaned and checked (about once a week) whether it is damaged, the operation is more cumbersome, once the anode bag damaged, the loss caused by the production is also great, but also to bring management of production Great inconvenience, no anode bags in the new system, eliminating some of the management problems.
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In the PCB production process, the use of DSA-coated titanium anode plating process, not only can enhance the quality of plating, but also reduce production costs and improve economic efficiency and facilitate production management. At the same time, it is equally feasible to use DSA electrolytic method to process etching waste liquid, recover copper and realize the regeneration of etching waste liquid in the process of PCB cleaner production. This method cannot only reduce the environmental pollution but also bring the enterprise A large part of the economic benefits.
