Metal Finishing Guide Book

2012-2013

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Zero Crossing Time (ZCT) 0.35 sec 2.89 mN No wetting ���0.55 mN As plated 0.35 sec 2.92 mN Pressure cooker 8 h Reference Fmax 0.41 sec 1.49 mN As plated Pressure cooker 8 h Betatec 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 solderability properties. Therefore, Betatec-treated samples were subjected to 8hour 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 parameters and conditions used for gold. All samples were plated with 1.2 ��m nickel and 8 ��m tin. It is clearly apparent that without Betatec post-dip treatment, no wetting occurs within the 10-second test period. The solderability results are summarized in Table 4. CONCLUSIONS Comprehensive test results have been presented for a new and patented gold postdip 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 corrosion resistance for a 0.3 ��m 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 nickel/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 electrical, solderability, or bonding properties of the gold electrodeposits. It has also been demonstrated that this treatment can provide a dramatic increase in protection 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/. 281

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