The New Base Colloidal Palladium Preparation And Applications

Recently years, the rapid development of high-tech such as the computer and communication, especially the rapid development of printed circuit board (PCB) provides vast market for electroless plating technology. The colloid palladium is used broadly in electroless industry, especially in the hole metallization of PCB. However, the report about preparing salt-based colloid palladium is less in the domestic and overseas. The reports about the study of ζ potential on salt-based colloid palladium and Pd recovery from waste colloid palladium are also less.In this paper, the salt-based colloid palladium was prepared successfully, and the optimal conditions of preparing salt-based colloid palladium was gained through studying the effects of preparation methods, technique conditions, additives and ζ, potentials on the activity and stability of salt-based colloid palladium. The feasible Pd recovery technique from waste colloid palladium was put forward through the comparing two kinds of techniques. The plating layer of nice quality was acquired when the salt-based colloid palladium had been used in activation step in the electroless copper plating on PCB and decorative copper plating on ABS plastic. The pollution of hydrochloric acid mist on environment and the pine-ring problem during the hole metallization of PCB because of the use of acid-based colloid palladium were resolved completely in this paper.Three-steps adding method was proved the best method of preparing salt-based colloid palladium according to the preparation technique test. The optimal conditions of preparing salt-based colloid palladium were that the PdCl₂, NaCl, organic substance A, organic substance B and ascorbic acid concentrations were 3.6 ,175, 150, 1.2 and 2 g/L respectively, the mole ratio of Sn to Pd was 50:1, the reaction temperature was 20³5℃,the reaction time was 8 min, the maturation temperature was about 55℃.The test results of optimal conditions showed that the time of starting hydrogen-deposition was 4s, the time of completely coating copper on a test substrate was lmin,the stability time of colloid palladium was 98h after it was diluted into 0.1 g/L(on amount of PdCl₂)when the solution temperature was 20℃, the Pd contents on thesubstrate surface was 20.47% by XPS spectrum analysis, the average particle size of colloid palladium was 98nm measured by Master Sizer.The effects of additives on the activity and stability of salt-based colloid palladium showed that the more the colloid palladium solution concentration, the more the Pd content on the substrate, the less the time of starting hydrogen-deposition and the time of completely coating copper on a test substrate. The average particle size of salt-based colloid palladium was 81, 83, 90, 78 and 104nm respectively when without additive, ascorbic acid, methanol, hydroquinone and organic substance B were added into the colloid solution. Ascorbic acid increased the stability of colloid palladium. Organic substance B increased the adsorption capacity of colloid on the substrate, increased the Pd adsorption quantity on the substrate and increased the activity of colloid palladium. Methanol decreased the activity and stability of colloid palladium. Hydroquinone had less effect on the activity and stability of colloid palladium.The salt-based colloid palladium was proved negative sol through C, potential study on salt-based colloid palladium, the structure of colloid palladium was {(Pd°)m-nSn2+-2 (n+x) CF}2x"- x Sn2+.The ￡ potential value of salt-based colloid palladium under the optimal condition was — 8.65mV. The mole ratio of Sn to Pd had less effect on the ￡ potential of salt-based colloid palladium, which value was about — 8.26mV when Sn/Pd was in the range of 10: 1 to 50: 1. The C, potential absolute value of salt-based colloid palladium was largest and equal to 8.65mV when NaCl concentration was 175g/L. The t, potential absolute value of salt-based colloid palladium decreased with the increases of methanol concentration, increased first and decreased then with the increases of organic substance B.The study of Pd recovery from waste colloid palladium showed that the feasible conditions in heating method were that dilution ration was 3, pH value was 1.3 and temperature was 100°C. After the colloid was broken, the Pd precipitates was dissolved by aqua regia, then pH value was adjusted 9¹0 with ammonia to remove Sn, and then adjusted 1 1.5 with hydrochloric acid to remove other soluble impurity, the Pd(99.92% in purity) was gained by reducing after purifying twice, the recovery rate was high as 98.79%. In the oxidation method, the aqua regia was added to dissolve the waste colloid palladium under the conditions that the Pd content was 0.2607g/L,reaction temperature was 100°C and the volume ratio of waste colloid palladium to aqua regia was 25: 4, Pd was refined by the above process and recovered, the recovery rate was only 60.87 %.The salt-based colloid palladium under the optimal condition was used in the activation step, and electroless copper plating was done on the printed circuit board. The test result showed that the backlight lever of electroless copper plating layer was 9th grade of 10-grade system and the adhesion force of the copper layer was up to GB5270-85 of China after electroless plating for 5 min; the backlight lever of electroless copper plating layer was 10th grade after electroless plating for 10 min; the plating layer surface was pure Cu by XRD analysis and the particle was nice and thin by SEM test after electroless plating for 15min. The above salt-based colloid palladium was used in the activation step, and decorative copper plating was done on ABS plastic. The XRD test result showed that the copper particle grew along (111) and (200) crystal side first when Japanese 210 brightener was added in the plating solution, whereas grew along (111) and (220 ) crystal side when ZS-210 brightener was added thereof. The SEM test showed that the copper particle was thin and plating layer was slippery and smooth in addition of Japanese 210 and ZS-210 brightener thereof. The cathode polarization curve showed that the copper deposition potential moved to negative direction remarkably, the polarizability increased and the exchange current density decreased in addition of Japanese 210 and ZS-210 brightener in the plating solution.