本研究使用各樣的實驗方法探討改變Al的重量百分比對Sn-8.5Zn-0.5Ag-0.1Ga-xAl銲錫合金的影響，探討添加量對凝固微組織、熔解熱、固液相溫度、兩相區間、合金的凝固模式和熱傳導及熱膨脹係數等熱物性質所造成的影響。
就Sn-8.5Zn-0.5Ag-0.1Ga-xAl銲錫合金的顯微組織觀察與分析，合金的金屬液凝固下來，Sn-8.5Zn-0.5Ag-0.1Ga合金會形成Ag-Zn介金屬化合物、針狀鋅與β-Sn的層狀共晶組織以及β-Sn基地；Sn-8.5Zn-0.5Ag-0.1Ga-xAl合金(x = 0.01、1、2、3、4)則會形成Ag-Zn介金屬化合物、Al-Zn固溶物、針狀鋅與β-Sn的層狀共晶組織及β-Sn基地。隨著Al的含量增加，Ag-Zn介金屬化合物減少，針狀鋅與β-Sn的層狀共晶組織增加。
除了Sn-8.5Zn-0.5Ag-0.1Ga-xAl合金的潛熱釋放模式為生成兩條垂直線，一條代表β-Sn的生成，一條代表Sn-9Zn共晶相的析出。隨著Al添加量的增加，代表β-Sn生成的垂直線消失，都只有呈現Sn-9Zn共晶相析出的垂直線，代表潛熱釋放模式趨向共晶。跟示差熱掃描分析圖的結果，顯示Al添加量的增加，峰值出現的溫度也是顯示出共晶形成的溫度。而液相溫度改變最大介於Al = 0~1.0wt%，之後，Al的添加量則無影響；固相溫度則有隨著Al的添加量變多而降低；溫度區間則以Al = 0wt%最大值，這與形成β-Sn及Sn-9Zn共晶相的析出造成溫度區間最大，而之後的Al = 0.01~4wt%，隨著Al的添加量變多，溫度區間則會先減少再增加的趨勢，溫度區間約略在3~4℃。
Sn-8.5Zn-0.5Ag-0.1Ga-xAl合金的熱傳導係數，就Al的添加量增加，傳導性質會有變佳的表現，原因或許出自於只改變鋁的添加量，Ag、Zn及Ga成分百分比未變，唯一變的成分是Sn，而Al的熱傳導係數大於Sn的結果所導致。
Sn-8.5Zn-0.5Ag-0.1Ga-xAl合金是顯示出瞬時熱膨脹係數在溫度區間30~40℃時，會快速上升，超過90℃時，瞬時熱膨脹係數約略為定值；而Sn-8.5Zn-0.5Ag-0.1Ga平均熱膨脹係數最高為26x10-6/K，Al = 2wt%時最小為21.7 x10-6/K，Al = 1、3、4wt%時則介於22~24 x10-6/K之間。雖然沒有趨勢說明添加Al的添加量對熱膨脹係數的影響，跟Sn-37Pb銲錫23.3x10-6/K相比的話，Al = 1、2、3wt%熱膨脹係數皆小於Sn-37Pb銲錫合金。

The solidification microstructure and the thermal physical properties of Sn-8.5Zn-0.5Ag-0.1Ga-xAl lead-free solder alloys, where x varies between 0.0 and 4.0 wt.%. A Computer Aided-Cooling Curve Analysis (CA-CCA) technique was used to determine the pasty ranges、liquidus temperature、solidus temperature and latent heat release modes for the alloys. The Differential scanning calorimetry was also used to measure fusion heat of alloys. The morphology of alloys and intermetallic compounds were observed with Scanning electron microscope and Electron probe microanalyzer. Energy dispersive spectrometer and Wave dispersive spectrometer were used to analyze the chemical compositions and elemental dispersion of intermetallic compounds. The thermal conductivity of The Sn-8.5Zn-0.5Ag-0.1Ga-xAl alloys is measured by thermal conductivity measurement. The CTE is measured by using a dilatometer with a heating rate of 1 ℃/min from 30 ℃ to 110 ℃. The effects of weight percentage of aluminum on the liquidus temperature, solidus temperature, pasty ranges, latent heat release modes, fusion heats and coefficient of thermal expansion and conductivity were investigated.
The solidification microstructure of the Sn-8.5Zn-0.5Ag-0.1Ga lead-free solder alloys shows β-AgZn, ε-AgZn3, γ-Ag5Zn8 and Zn-rich phases dispersed in the β-Sn matrix. As we add aluminum, the Al-Zn solid solution appears and become more and more. With the increased addition of Al, the Ag-Zn IMCs decrease but the eutectic Sn-Zn and Al-Zn phases increase.
The CACCA results show that as the aluminum content of the Sn-8.5Zn-0.5Ag-0.1Ga-xAl alloy increases, the solidus temperature rises and the pasty range broadens slightly. As long as the aluminum content is 0 wt%, the plot of the fs-T relationship shows two distinct vertical regions. One corresponds to the primary tin phase and the other to the eutectic phase. As the aluminum content increases, one vertical region corresponding to the primary tin disappears. The microstructure is basically the eutectic Sn-9Zn and the fs-T relationship is nearly a vertical line. This in turn causes the proportion of the primary tin phase to decrease and that of the zinc-tin eutectic phase to increase. As the aluminum content further increases, the effects of intermetallic compound formation become even more obvious. The Al-Zn phase diagram shows that, αAl solid solution has a maximum solubility of 67at% Zn at 382℃ but has a maximum solubility of 59.4at% Zn at 275℃. Also the diagram indicates that the solubility of αAl decreases as the temperature decreases. The results of WDS showed that the Al-Zn solid solution has only solubility of 6.5at% Zn at room temperature. Consequently, the released Zn reacts with Sn to form the more tin-zinc phase.
The thermal conductivity is increased with increasing the content of aluminum. The reason may be the thermal conductivity of aluminum is lager them that of tin. When the content of aluminum increased, that of tin decreased. The results also shows that Sn-8.5Zn-0.5Ag-0.1Ga-xAl (x＞0) lead-free solder alloys have much better thermal conductivity than Sn-37Pb solder alloy.
The CTE is increased with increasing temperature. When the temperature between 30~40℃, the increase becomes sharply. When the temperature reaches 90℃, the increase becomes not so obvious. Furthermore, CTE doesn’t increase linearly with increasing aluminum content. As the aluminum contents are between 1~3wt%, the values of CTE are smaller than the conventional Sn-37Pb alloy and is near the copper.

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