錫中微量添加鈷對銀、銅、鎳基材界面反應之影響與錫-鈷-銀三元系統相平衡

The Effect of Minor Additions of Co upon Interfacial Reactions between Sn and Ag, Cu, and Ni Substrates and Sn-Co-Ag Ternary Phase Equilibria

詹雅婷(Ya-Ting Chan)

指導教授 ： 陳志吉

中原大學/工學院/化學工程研究所/碩士(2012年)

https://doi.org/10.6840/cycu201200396

摘要

在銲料中添加微量元素為銲料改質之重要手段，在眾多量添加元素中，Co由於可增強銲點之機械強度，受到很大注目。本研究探討於Sn中添加微量Co對Ag、Ni、Cu等常用之電子材料表面處理層之界面反應影響，並以實驗方法決定出Sn-Co-Ag於250oC下之相平衡。
在Sn-Co-Ag三元系統於250oC下之相平衡研究中，沒有發現三元相，共決定出9個單相區、10個兩相區，以及7個三相區。三相區為: Liquid-CoSn3-Ag3Sn、CoSn3-CoSn2-Ag3Sn、CoSn2-CoSn-Ag3Sn、CoSn-Ag3Sn-Ag4Sn、CoSn-Co3Sn2-Ag4Sn、Co3Sn2-Co-Ag4Sn、Ag4Sn-Co-Ag。兩相區為Liquid-CoSn3、Liquid-Ag3Sn、CoSn3-Ag3Sn、CoSn2-Ag3Sn、CoSn-Ag3Sn、CoSn-Ag4Sn、Co3Sn2-Ag4Sn、Co-Ag4Sn、Ag4Sn-Ag、Co-Ag。單相區有Liquid、Co3Sn2、CoSn3、CoSn2、CoSn、Co、Ag3Sn、Ag4Sn、Ag。絕大部分的單相近乎沒有第三元溶解度，而Ag4Sn則溶有7at%Co以及Ag溶有2.5at%Co。
Sn(-Co)/Ag之界面反應在界面處皆只生成Ag3Sn相。當Co的添加量越高，反應速率越慢，活化能降低。Co的添加對反應速率的影響以對Cu基材的影響最大，其次為Ni基材，影響最小為Ag基材。在銲料中添加微量Co會使反應生成相晶粒變小，改變程度以Cu6Sn5最強烈，其次為Ni3Sn4，影響程度最小為Ag3Sn。

關鍵字

無鉛銲料 ； 微量添加 ； 固態擴散

並列摘要

Because of the property reinforcement of soldering joints, minor element alloying has attracted great attentions in Pb-free solders development. Among the alloying elements, Co is reported effective in reducing the undercooling of the solders, and is likely caused by small Co solubility in Sn. This thesis investigates effects of minor Co additions upon the interfacial reactions between the pure Sn and Ag, Cu, ands Ni substrates. The phase equilibria of the Sn-Co-Ag ternary system at 250oC are determined as well. The phase equilibria information is crucial to the analysis of the reaction path at soldering joints.
No ternary phase is found at the 250oC isothermal section of the Sn-Co-Ag ternary system. Seven three-phase regions, ten two-phase regions, and nine single-phase regions are determined. There is no noticeable ternary solubility in most equilibrated phases except the Ag4Sn and FCC-Ag phases. The maximum Co solubility in the Ag4Sn and FCC-Ag phases are 7 and 2.5at%, respectively.
Only the Ag3Sn phase is observed in Sn-Co/Ag couples. With higher Co additions in the pure Sn, the Ag3Sn growth rate is slower, and the activation energy is lower down. The effect of minor Co additions to the reaction rates with different substrates is Cu>Ni>Ag. Co addition also refines the grains of the reaction phases. The Co effect upon the grain size of the reaction phase is Cu6Sn5>Ni3Sn4> Ag3Sn.

並列關鍵字

Electronic packaging ； Lead-free solder

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