不同尺寸電子銲點中之相生成與相變化

Phase formation and phase transformation in the electronic solder joints of different sizes

黃育智(Yu-chih Huang)

指導教授 ： 陳信文

國立清華大學/工學院/化學工程學系/博士(2010年)

摘要

銲點中的相生成與相變化對銲點的性質影響甚鉅，並進而左右電子產品的可靠度，由於不同的構裝層次中有不同尺寸的銲點，尺寸效應是軟銲技術中的一個重要議題；本研究探討不同尺寸電子銲點在固化與界面反應中的相生成與相變化，並建構相關系統的相圖，對固化與界面反應中的相生成與相變化現象有清楚的解釋。
本研究探討銲料合金的過冷現象與固化路徑，銲料合金的過冷程度同時受到第一析出相以及基材種類的影響，而在第一析出相以及基材皆相同時，過冷仍會稍微受到組成的影響；過冷程度隨著合金尺寸下降而升高，但彼此之間的相對大小維持不變。本研究完成Sn-Zn-Cu三元系統的液相線投影圖，並根據實驗結果建立其熱力學模型，此系統共有十個第一析出相、六個第二類反應、以及一個第三類反應。
本研究探討銲料合金與基材的界面反應，Sn-0.7wt%Cu/Fe比起Sn-37wt%Pb/Fe有較劇烈的反應速率與溶解行為；Sn-37wt%Pb/Fe與Sn-57wt%Bi/Fe在高溫時反應生成相的變化可以由三元系統中缚線的改變得到合理的解釋。Sn-8.8wt%Zn/Cu與Sn-57wt%Bi/Cu中反應生成相的厚度隨著銲料合金中Co添加的含量增加而分別減低與增加；Sn-8.8wt%Zn/Cu中反應生成相的變化以及Sn-57wt%Bi/Cu中反應生成相的型態皆同時受到微量Co的添加以及銲點尺寸的影響。
本研究建立Sn-Zn-Cu三元系統的熱力學模型，並以其計算液相線投影圖與計算等溫截面圖討論Sn-Zn/Cu銲點中的固化與界面反應；建立Sn-Zn-Co三元系統的液相線投影圖，並用以瞭解Sn-Zn-(Co)銲料合金的固化；建立Sn-Fe二元系統、Sn-Pb-Fe三元系統、以及Sn-Bi-Fe三元系統的熱力學模型，並依據其計算等溫截面圖解釋Sn-Pb/Fe與Sn-Bi/Fe銲點中的界面反應。

關鍵字

固化 ； 過冷 ； 界面反應 ； 尺寸效應 ； 相圖 ； 無鉛銲料

並列摘要

Very different sizes of solder joints are produced in different packaging levels. The phase formation and phase transformation in the solder joints are crucial to the reliabilities of electronic products. This study examines the phase formation and phase transformation from the solidification and interfacial reactions in the solder joints of different sizes. Phase diagrams are also proposed in this study based on phase equilibria, and the results in solidification and interfacial reactions are well illustrated by the phase diagrams.
The degrees of undercooling of various solder alloys are examined. The primary factors controlling undercooling are the primary solidification phase and the substrates. When the primary solidification phase and the substrates are the same, the degrees of undercooling could be different if the compositions of the melts are different. However, this compositional effect is not very significant. The degrees of undercooling and their variations are more significant for smaller-sized solders, but the relative orders of undercooling of various solders remain the same. The liquidus projection of Sn-Zn-Cu ternary system is experimentally determined, and the thermodynamic modeling is developed. Ten primary solidification phases, six class II and one class III invariant reactions are found.
Interfacial reactions between solders and substrates are investigated. The reaction rates and substrate dissolution in the Sn-0.7wt%Cu/Fe couples are higher than those in the Sn-37wt%Pb/Fe couples. The reactive phase transitions at higher temperatures in the Sn-37wt%Pb/Fe and Sn-57wt%Bi/Fe couples are caused by the ternary phase equilibria tie-line shift. With increasing Co additions, the reaction phase thicknesses in the Sn-8.8wt%Zn/Cu and Sn-57wt%Bi/Cu couples are decreased and increased, respectively. The transition of different reaction stages in the Sn-8.8wt%Zn/Cu couples and the morphology of reaction phase in the Sn-57wt%Bi/Cu couples are influenced by both the minor Co additions and the sizes of solder joints.
Phase diagrams including Sn-Zn-Cu liquidus projection and isothermal section, Sn-Zn-Co liquidus projection, Sn-Fe phase diagram, Sn-Pb-Fe isothermal sections, and Sn-Bi-Fe isothermal sections are established. The solidification phases and solidification paths of solder alloys and the reaction phases and reaction paths in the interfacial reactions are well illustrated by the phase diagrams.

並列關鍵字

Solidification ； Undercooling ； Interfacial reaction ； Size effect ； phase diagram ； Pb-free solder

參考文獻

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