Heat aging to simulate long-term storage or operation at elevated ambient temperatures resulted in the formation of an intermetallic compound between the copper or nickel substrate and the tin in tin-lead plated samples. Two intermetallics, Cu/sub 6/Sn adjacent to the substrate followed by Cu/sub 6/Sn/sub 5/, were formed on the aged copper samples, while only one nickel-tin, a Ni/sub 3/Sn/sub 4/ intermetallic, was found on the nickel samples. Increasing the aging duration resulted in increased thickness of the intermetallic compounds. As the intermetallic compound adjacent to the substrate, either the Cu/sub 3/Sn or Ni/sub 3/Sn/sub 4/, increases in thickness the lead from the tin-lead plating is rejected, although there is some evidence that not all the lead is rejected from the Cu/sub 6/Sn/sub 5/ phase. The rejected lead agglomerates result in an enriched lead surface. The copper-tin intermetallics tend to grow faster than the nickel-tin intermetallic compounds, suggesting that usage of a nickel barrier plating may retard the growth rate of the copper-tin intermetallics. Contact resistance vs. force curves exhibit small increases in resistance as long as there is still some unreacted tin-lead on the plated surfaces.
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机译:为了模拟在高温环境下的长期存储或操作而进行的热老化,导致镀锡铅样品中的铜或镍基板与锡之间形成金属间化合物。在老化的铜样品上形成了两种金属间化合物,即与基底相邻的Cu / sub 6 / Sn,然后是Cu / sub 6 / Sn / sub 5 /,而只有一种镍锡,即Ni / sub 3 / Sn / sub。在镍样品上发现了4 /金属间化合物。老化时间的增加导致金属间化合物厚度的增加。尽管有一些证据表明,由于与基材相邻的金属间化合物Cu / sub 3 / Sn或Ni / sub 3 / Sn / sub 4 /的厚度增加,所以拒绝了锡铅镀层中的铅。从Cu / sub 6 / Sn / sub 5 /相中排除了所有铅。废弃的铅附聚物会导致富集的铅表面。铜-锡金属间化合物倾向于比镍-锡金属间化合物增长更快,这表明使用镍阻挡层镀层可能会阻碍铜-锡金属间化合物的生长速率。只要在电镀表面上仍有一些未反应的锡铅,接触电阻与力的关系曲线就会显示出电阻的小幅增加。
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