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Nitrogen-Dioxide-Inhibitor and the Study of Environment-Friendly Rack Coating Stripping Technics

Author: YangZhenXing
Tutor: LiDeLiang
School: Central South University of Forestry Science and Technology
Course: Environmental Engineering
Keywords: Environment-friendly Nitrogen-Dioxide-Inhibitor Application Optimum condition
CLC: TQ153
Type: Master's thesis
Year: 2009
Downloads: 27
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Abstract


The purpose of this paper is to study on the application of nitrogen dioxide inhibitor in PCB industry, including stripping the copper-coating on rack and subsequent disposing the waste stripping liquid by direct-electrodeposition method.The main oxidant of rack coating stripping technics is nitric acid. A lot of yeLlow smoke would be producted during the rack-coating-stripping by nitric acid and this phenomena called "yeLLow dragon" in this industry. In fact,this yellow smoke was a flagrant air contamination—nitrogen dioxide.Besides that, the treament of subsequent waste liquid and residue was also a problem that deserve to be considered.Accordingly, a simple and efficient method was exigent needed to change these actuality. Most of civil enterprise always attached very few importance to the link of rack-coating-stripping and they also didn’t to invest too much on that. But if a little betterment could exchanged biggish environmental benefit and economical benefit,then the enterprise would be apt to accept it.The application of this nitrogen dioxide inhibitor (inhibitor for short) in rack-coating-stripping and subsequent waste stripping liquid treatment by direct-electrodepostion method was embedded studied in this paper. Base on the current rack-coating-stripping technics, the nitrogen dioxide inhibitor was added to eliminate the "yellow dragon" and the defect of low current efficiency during electrodeposite the waste rack stripping solution directly. The content of this research including:1) the effects of several factors (temperature, volume fraction of nitric acid, volume fraction of nitrogen dioxide inhibitor, concentration of metal ion) on average stripping speed, ultimate dissolved amount of copper and effect of nitrogen dioxide-inhibition were discussed by single factor experiment. Then optimize this technological condition combination by orthogonal test and examine the optimum condition by experiment.2)During direct-electrodeposite the subsequent waste stripping liquid, the effects of volume fraction of nitrogen dioxide inhibitor, groove voltage and electrodeposition time on current efficiency and recovery efficiency were studied by single factor test and the best technological condition combination was fixed. Then the result of treatment that with or without this inhibitor were compared. The data was showed that:1)the optimum condition of rack copper coating stripping is:temperature 35℃, volume fraction of nitric acid 40%, volume fraction of nitrogen dioxide inhibitor 30%, concentration of copper ion 30g/L. In the condition, its performances and technicaL index were:average stripping speed of copper coating is 7.47μm/h, the ultimate dissolved amount of copper is 67g/L. It’s almost the same to the index of traditional nitric acid method.2) The best condition of electrodeposited copper was:groove voltage2.6V, time of electrodeposition 4h, volume fraction of nitrogen dioxide inhibitor 20%, the current efficiency of copper could reached 81.4%, the recovery efficiency of copper could be 79.1%;The best condition of eLectro-deposited nickel was:groove voltage 4V, time of electrodeposition 12h, voLume fraction of nitrogen dioxide inhibitor 20%, the current efficiency of nickeL could reached 74.4%, the recovery efficiency of nickel couLd be 84.3%; Tha application of this inhibitor has enhanced the current efficiency and recovery efficiency for around 20 and 15 percentage points respectively. The application of this inhibitor make the new technics has exceeded the original technics so much in environmental aspect and secure aspect, the future of this inhibitor is can’t-be-ignored.

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CLC: > Industrial Technology > Chemical Industry > Electrochemical industries > Electroplating industry
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