無鉛銲料合金之熱力學性質

Thermodynamic properties of Pb-free solder alloys

陳鳳鴒(Feng-Ling Chen)

指導教授 ： 陳信文 ； 謝克昌

國立清華大學/工學院/化學工程學系/碩士(2006年)

摘要

摘要
無鉛銲料之開發是近年來電子工業中最重要議題之一。目前文獻中關於無鉛銲料之研究，以針對合金之溼潤性、界面反應與機械性質討論為主。本研究擬探討無鉛銲料合金之熱力學性質，以提供十分重要但文獻中卻缺少之知識。本研究測定無鉛銲料之熔點、熔化焓(enthalpy of fusion)、與活性(activity)，並探討應用於無鉛銲料合金之Sn-Bi、Sn-Zn與Sn-Bi-Zn系統之熱力學性質。本研究主要使用微差熱卡儀(Differential Scanning Calorimetry, DSC)來測定熔化溫度與熔化焓，並建構一可靠的電動勢(electromotive force, EMF)實驗方法，以量測 Sn或Zn之活性。EMF方法主要是量測液態Sn或Zn與合金間平衡之開路電位(open circuit potential，OCP)，由於純物質與合金中(添加不同莫耳分率之Bi與Zn)的Sn或Zn其氧化還原能力不同，當反應達到平衡即有一平衡電位，利用熱力學與電化學平衡關係式可求得，在平衡狀態下電位與活性之關係，進一步求得其它熱力學性質。Sn在Sn-Bi合金的活性呈正偏差趨勢；其混合焓相當小，略呈吸熱反應。Zn在Sn-Bi-Zn、 Sn-Zn合金的活性呈正偏差趨勢；在Sn-Zn添加入與Sn分率相等的Bi時，會使Zn於合金中的活性較單純Sn-Zn系統中增大，但整體自由能則較Sn-Zn合金低；Sn-Bi-Zn合金所量測Class I ：L ↔ (Sn) + (Bi) + (Zn) 相變化溫度為134 oC，而非文獻值之130 oC。

關鍵字

無鉛銲料 ； 熱力學性質 ； 電動勢量測方法 ； 錫鉍合金 ； 錫鋅合金 ； 錫鋅鉍合金

並列摘要

Abstract
Development of lead-free solders is an important subject in the electronic industry. Present investigations of lead-free solders focus on the wettability, interfacial reaction and mechanical properties. Thermodynamic properties of lead-free solder alloys which are important but only few information is available, are investigated in this study. Thermodynamic properties, such as melting temperatures, fusion enthalpies and activities, of Sn-Bi, Sn-Zn, Sn-Bi-Zn lead-free solders materials are determined. The melting temperatures and fusion enthalpies of alloys are measured by differential scanning calorimetry. Reliable electromotive force method (EMF method) is developed to measure the activities of Sn or Zn. EMF method measures the open circuit potential between the Sn (or Zn) and alloys in liquid state. The equilibrium potentials of the difference of the red-ox ability of pure element and the alloy samples are determined. The relationship of the potentials and the activities and other thermodynamic properties are calculated by using the thermodynamic and electrochemical equilibrium functions. The mixing enthalpies are very small in the Sn-Bi alloys. The activities of Sn in Sn-Bi alloys are nearly ideal and show slightly positive deviation. The activities of Zn in Sn-Bi-Zn and Sn-Zn alloys show positive deviation; in the same content of Zn and temperature, the activities of Zn in Sn-Bi-Zn alloys are larger than in Sn-Zn alloys, but mixing Gibbs free energy of Sn-Bi-Zn alloys are lower than Sn-Zn alloys. The invariant temperature of the class I: L ↔ (Sn) + (Bi) + (Zn) phase transformation in Sn-Bi-Zn alloys is 134 oC.

並列關鍵字

lead-free solder ； thermodynamic properties ； electromotive force method ； Sn-Bi alloy ； Sn-Zn alloy ； Sn-Zn-Bi alloy

參考文獻

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