Metal Finishing Guide Book

2011-2012 Surface Finishing Guidebook

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Zero Crossing Time (ZCT) Reference Betatec As plated Pressure cooker 8 h As plated Pressure cooker 8 h 0.35 sec No wetting 0.35 sec 0.41 sec Fmax 2.89 mN –0.55 mN 2.92 mN 1.49 mN Table 4: Solderability Results for Untreated and Betatec-treated Samples on Tin Deposits the tin but also provide preferable increased corrosion resistance. Oxide formation of tin (evident as surface discoloration) greatly impairs sol- derability properties. Therefore, Betatec-treated samples were subjected to 8- hour pressure cooker tests. The results shown in Figure 10 highlight the beneficial corrosion resistance of the Betatec treatment. SOLDERABILITY STUDY OF TIN DEPOSITS The solderability study of tin deposits was undertaken using the same parame- ters and conditions used for gold. All samples were plated with 1.2 µm nickel and 8 µm tin. It is clearly apparent that without Betatec post-dip treatment, no wet- ting occurs within the 10-second test period. The solderability results are sum- marized in Table 4. CONCLUSIONS Comprehensive test results have been presented for a new and patented gold post- dip treatment that significantly improves the corrosion resistance of nickel/gold deposits and contributes to the reduction of gold costs. Extended NAV testing (to two times the ASTM B-735 standard) shows a significant increase in corro- sion resistance for a 0.3 µm gold thickness. It has been demonstrated that the Betatec post-dip can impart beneficial hydrophobic properties to the gold surface with subsequent blocking of pores. This hydrophobic and protective mechanism has been evaluated by water contact angle measurements on pure copper, nickel, and gold deposits together with nick- el/gold plating on copper (before and after treatment with the gold post-dip). Results show that this beneficial post-treatment has no adverse effects on elec- trical, solderability, or bonding properties of the gold electrodeposits. It has also been demonstrated that this treatment can provide a dramatic increase in pro- tection of tin deposits, allowing for easy incorporation into most selective gold plating lines. REFERENCES 1. Kaiser H. Edelmetallschichten. Bad Saulgau: Leuze Verlag, 2002. 2. Braunovic M, Konchits VV, Myshkin NK. Electrical Contacts. CRC Press, 2007. 3. KITCO Precious Metals. Historical Data and Charts. Available at: www.kitco.com/charts/. 154

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