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The New Electroless Copper Plating System With Iminodiacetic Acid As The Complexing Agent And Super Electroless Nickel Preliminary Study

Posted on:2012-08-08Degree:MasterType:Thesis
Country:ChinaCandidate:J GaoFull Text:PDF
GTID:2191330335472083Subject:Applied Chemistry
Abstract/Summary:PDF Full Text Request
Electroless copper plating is one of the main techniques of surface treatment technology, which has been widely used. Recently, formaldehyde has been still used as the mainly reduction agent, for its low cost and low operation temperature. However, formaldehyde bath was unstable and toxic, which caused cancer and environmental pollution. The electroless copper plating with sodium hypophosphite as the reducing agent is environmental friendly, stable and no deleterious steam. At present, sodium citrate has been widely used as the main complexing agent in sodium hypophosphite the electroless copper plating, which results in the as-deposited copper film with a high percent of nickel, dark red color and high resistance.In this thesis, iminodiaeetic acid was used as the complexing agent to improve the quality of the as-deposited copper film in sodium hypophosphite electroless copper plating. The effects of pH value, bath temperature and components of the bath on the deposition rate and the stability of electroless bath were investigated. The influence of pH value on the deposition rate was also studied by electrochemical method. The deposited Cu films were characterized by scanning electron microscope (SEM), atomic force microscopy (AFM) and X-ray diffractometry (XRD).The experiment results indicated that the copper deposition rate was increased with the increase of reaction temperature, CuSO4·5H2O concentration and sodium hypophosphite. The copper deposition rate was decreased with the increase of the iminodiaeetic acid concentration and pH value, which was in good agreement with the electrochemical results. The reduction peak potential (for cathodic reaction) shifted positive and the current density increased with a pH value of the plating bath. In this paper, the appropriate compositions of the electroless copper plating bath were obtained: copper sulfate 0.04~0.05 mol/L, iminodiaeetic acid 0.06~0.08 mol/L, sodium hypophosphite 0.32-0.36 mol/L, acetic acid sodium,0.2 mol/L; the pH was 4.5-5.0 and the operating temperature was 80℃. The result illustrated that the basic solution was in good stability. The rate of copper deposition reached 2.5μm/h. The copper film with a good ctystal and no nickel containing was obtained. The quality of copper film was improved and the resistance was decreased.The bottom-up filling of electroless nickel is another important research in this paper. Based on the different character of the additives, PAA was used as an inhibitor. Because of inhibition and low diffuse coefficient of PAA3000-5000, the deposition rate of the electroless nickel was decreased gradually from the bottom to the top of the trench, the rate gradient of the electroless nickel was formed. The results showed that PAA (molecular weight 3000-5000) exhibited inhibition for electroless nickel deposition. The deposition rate of electroless nickel was 5.5μm/h without any additives, and it was dropped to 2.5μm/h when PAA concentration was 2.0 mg/L. With a further increase of the PAA concentration, the deposition rate of electroless nickel bath was decreased sliwly. In this research, the nickel plating bath containing PAA with a concentration of 2.0 mg/L was used to investigate the nickel bottom-up filling for different trenches.
Keywords/Search Tags:Electroless copper plating, Sodium hypophosphite, Iminodiaeetic acid, super-filling for electroless nickel
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