Influence of phosphorus content on the interfacial microstructure between Sn-3.5Ag solder and electroless Ni-P metallization on Cu substrate
Influence of phosphorus content on the interfacial microstructure between Sn-3.5Ag solder and electroless Ni-P metallization on Cu substrate
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DOI：
10.1109/tadvp.2006.879420
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发表时间：
2007-02
期刊：
影响因子：
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通讯作者：
Mona;A. Kumar;Zhong Chen
中科院分区：
文献类型：
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作者：
Mona;A. Kumar;Zhong Chen
凹凸下金属化(UBM)通常由几个薄的金属层组成，在保护底层金属化不与焊料反应的同时，提供了良好的可焊接表面。具有薄层浸金的化学镀镍(Ni-P)被认为是凸点下和衬底金属化的最有前途的候选之一。然而，与纯Ni相比，化学镀Ni-P中P的存在会引起更复杂的界面反应。Ni-P层中P的含量从微观结构和反应动力学两个方面影响着焊接反应。本文研究了磷含量对铜基化学镀Ni-P合金与锡-3.5Ag焊料界面组织的影响。在铜基上镀制了三种不同磷含量(6.1、8.8和12.3wt.%)相同厚度的化学镀Ni-P层。然后制备了具有Sn3.5Ag/Ni-P/Cu叠层的多层样品，并进行了多次回流试验。不同类型的界面化合物(IFC)，如Ni3Sn4、Ni3P、Ni-SnP、CuSn2和NiCuSn4，取决于回流焊的数量。低磷样品中生成的Ni3Sn4金属间化合物更稳定，而中、高磷样品中生成的Ni3Sn4在回流过程中主要剥落到熔体中。与低磷样品相比，中、高磷样品中Ni3Sn4层裂导致了较厚的铜锡化合物和镍铜锡金属间化合物。文中对观察到的界面微观结构提出了详细的解释
Under bump metallization (UBM), which usually consists of a few thin metallic layers, provides good solderable surface while protecting the underlying metallization from reacting with solder. Electroless nickel (Ni-P) with a thin layer of immersion gold has been considered as one of the promising candidates for under bump and substrate metallizations. However, the presence of P in electroless Ni-P causes more complicated interfacial reactions with solder than pure Ni. The amount of P in the Ni-P layer affects the soldering reaction in terms of microstructure and reaction kinetics. In this work, influence of P content on the interfacial microstructure between Sn-3.5Ag solder and electroless Ni-P metallization on Cu substrate has been investigated. Electroless Ni-P layers of three different P contents (6.1, 8.8, and 12.3 wt.%) with the same thickness were plated on Cu substrate. Multilayered samples with Sn-3.5Ag/Ni-P/Cu stack were then prepared and subjected to multiple reflows. Various types of interfacial compounds (IFCs) such as Ni3Sn4, Ni3P, Ni-Sn-P, Cu-Sn, and Ni-Cu-Sn formed depending upon the number of reflows. Ni3Sn4 intermetallic compound formed in the low P sample was found to be more stable, whereas, Ni3Sn4 formed in the medium and high P samples mostly spalled off into the molten solder during reflow. The Ni3 Sn4 spallation was found responsible for thicker Cu-Sn and Ni-Cu-Sn intermetallics in the medium and high P samples as compared to that of low P sample. Explanation for the observed interfacial microstructure is proposed in the paper in detail