Application Titanium Anodes

Application of titanium anodes

Titanium anode (MMO) is prepared by sintering titanium substrate coated with noble metal iridium salt at high temperature, and is widely used in electro-plating (copper/gold electro-plating to satisfy high demand of deep hole in circuit board industry), electrolysis and other wet-process metallurgy industries. The electrode is prepared and applied in a comparatively mature way, and has been applied for 40 years. In compared conventional with platinum-plated electrode, the titanium anode has the following advantages:
1. Technical characteristics: high current, high efficiency, excellent bacterium and corrosion resistance, and long service life; the titanium anode is applicable to comparatively high current density; the operating current density is not greater than 10, 000A/m2, belonging to oxygen evolution type anode taking industrial pure titanium as base layer; 
2. It is well-known that catalysis activity of the titanium anode is high; different from platinum-plated electrode which is an electrode having high oxygen evolution over-potential (1.563V, compared with mercurous sulphate), the MMO anode is an electrode with low oxygen evolution over-potential (1.385V, compared with mercurous sulphate), which makes it easy to realize oxygen evolution in anode oxygen evolution zone; in the process of electrolysis, the bath voltage is comparatively low to save electric energy, which is remarkable in post-treatment of alkaline copper-plated wall in the copper foil; 
3. No pollution: MMO anode coating is ceramic oxide of noble metal iridium, which is a comparatively stable oxide and is nearly insoluble in any acid and alkali; the oxide coating is about 20-40 microns, and the integral coating oxide amount is comparatively low, which avoids pollution to the electro-plating liquid as the platinum-plated electrode;
4. High cost performance, and same service life as platinum-plated electrode (with coating 3.5 mm thick); price of the MMO anode is about 80% of the platinum-plated electrode; MMO anode shows excellent electro-chemical stability in alkaline electro-plating copper electrolysis liquid, and has excellent electrolysis activity and durability. From aspect of cost, the MMO anode is more economic compared with PT electrode;
5. Pulse periodical reverse (PPR) is required in application of copper in printed circuit, but platinum-plated titanium insoluble anode is forbidden (platinum layer will strip off after a duration with presence of chloride in the sulphuric acid electrolysis liquid); the anode with stable size can avoid such phenomenon, and can present performance advantage of insoluble anode technology in the application;
6. The least maintenance: it is unnecessary to shut down to clean or supply anode, or to change anode bag or apply new coating to the anode (so as to improve production efficiency and reduce labour cost);
7. Service life of the insoluble anode is determined by type, working current density, as well as contact with various electro-plating chemical materials; positive pulse (PPR) electro-plating anode.
Along with increasing price of metal raw material, copper ion is easy to rapidly deposit on the edge part (the current density is comparatively high) of hole while slowly deposit in centre (the current density is comparatively low), which causes problem of uneven distribution of copper (the phenomenon is called bone shape); bone-shape phenomenon occurs if operating by medium current density, cylinder cracking is caused if operating by comparatively low current density, and burning phenomenon occurs if operating by comparatively high current density, which is unquestionably a heavy impact for electro-plated circuit board.
To solve said problem, reverse pulse electro-plating anode is generated. Pulse periodical reverse (PPR) is required in application of copper in printed circuit, and platinum layer will strip off after a duration with presence of chloride in the sulphuric acid electrolysis liquid; the positive reverse pulse electro-plating anode has the following features:
1. Geometric size of anode is unchanged to optimize current distribution;
2. Low maintenance of anode: it is unnecessary to shut down to clean or supply anode, or to change anode bag, so as to improve production efficiency and reduce labour cost;
3. Solving the problem about uniformity of plating layer of deep hole electro-plating: high current efficiency, and capable of bearing current density of 1000A/M2;
4. No pollution to electro-plating medium: the positive/negative pulse electro-plating anode is oxygen evolution type anode which takes industrial pure titanium (TA2) as substrate; and the anode has long service life and excellent corrosion resistanc