| Chemical gold plating is widely used in electronic components such as electrical appliances,connectors,printed circuit board(PCB),integrated circuit(IC)and so on.Mainly because the plating layer has excellent conductive thermal conductivity,high weldability,good corrosion resistance and bonding force to meet a variety of assembly requirements.The cyanide in the cyanide plating solution is contained poisonous to producing great potential safety hazard for the technological process and post-treatment,especially the cyanide corroded for PCB substrate lead to the application restricted in microelectronics industry.In recent years to pursue of environmental friendly and resource saving production mode and the improvement of environment,the disadvantage of cyanide plating is more and more obvious,more attention paid to the non cyanide plating process.The research purpose of this paper is to synthesize a new kind of cyanide-free aurous complex,with dimethylthiourea as hgand.At the same time,the kind of complexes were characterized,and the last,carry out study on the chemical plating performance of aurous complex solution.In the hope of the aurous complex solution stability,and the effect of coating can meet the industry requirements.The research content could be splited into several parts and as follow:(l)By using selective reduction-ligand exchange method,we want to synthesize cyanide-free aurous complex.To explore the optimum process conditions of synthesis by changing the ratio,pH,temperature,concentration;And the same time,the stability of cyanide-free gold complexes solution were studied.(2)Characterizing the cyanide-free gold complexes,the molecular structure of cyanide-free gold complexes would be determined by elemental analysis,ultraviolet spectrum analysis,infrared spectrum analysis and differential thermal analysis.(3)Studying the ehemical plating technology of cyanide-free aurous complexes,such investigating the effect factors of gold concentration,temperature,pH,concentration of the ligands,plating time influencing the plating rate,and further exploring the optimal process conditions.(4)Testing of the plating layer performance on the coating thickness,apparent morphology and combining power.The research results indicated:(1)By using selective reduction-ligand exchange method,we successfully synthesized cyanide-free aurous complex.(2)Through element analysis of the complexes is made on the percentage of Au,C,N,H,S,respectively,41.68%,18.31%,14.98%,3.72%,21.31%,and coupled with ultraviolet spectrum analysis,infrared spectrum analysis we can conclude the molecular formulas of cyanide-free aurous complex is Au(DMTU)2SCN.(3)The cyanide-free aurous complex is slightly soluble in water,soluble in ethanol aqueous.The molar conductivity in water is 2.1 8×10-3 S·m2·mol-1,thermal decomposition temperature is 190?.(4)The optimum process conditions of Au(DMTU)2SCN as:pH=1,n(Au/SCN-)=3:1,n(Au/Tu)=2.5:1 and solution temperature is 25 C.(5)The stability of cyanide-free aurous complexes solution was studied as:the complexes solution was stayed in less than 70 C,its pH rangs from 3 to 7 and keeping stay in airtight shading.(6)The optimum process conditions of chemical plating are as follows:gold solution concentration is 2.5 g/L,dimethylthiourea concentration is 1.5 mol/L,the operating temperature is 50 C,PH 4.plating time is 20 min.under this condition,the chemical coating binding,colour and lustre are best state.The research shows that,the cyanide-free plating system give priority to with Au(DMTU)2SCN,not only can meet the requirements of chemical plating in PCB industry,but also it can significantly reduc environment pollution and used to alternate the highly toxic cyanide.The cyanide-free aurous complex is a environmental chemical product that is expected to widely applly in plating industry. |
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