電化學沉積三元熱電材料之技術開發

Abstract

本研究利用電化學沉積三元熱電材料，添加SeO2於鍍液中沉積n型及p型 Bi-Te-Se熱電材料，探討因添加SeO2後所造成鍍層表面形貌與成份比例變化。同時，量測其最佳熱電特性，其中包含席貝克係數、導電率以及藉由平行線量測熱傳導係數。最後，利用已知熱電特性的三元熱電材料，搭配微機電製程技術與覆晶接合技術，進行微致冷晶片之研製與性能評估。 本實驗以HNO3 1 M、Bi2O3 7.5 mM、TeO2 10 mM、SeO2 3 mM金屬氧化粉末進行三元熱電材料之電化學沉積。經分析結果證實，於鍍液中添加SeO2後所形成之三元熱電鍍液，有助鍍層的熱電特性提升。經實驗發現在SeO2添加量為3 mM時，根據不同電流密度調變下，可促使Bi-Te-Se三元熱電材料n型與p型特性轉換，當電流密度為1 mA/cm2時，材料為p型特性；當電流密度高於1.85 mA/cm2時，材料為n型特性。量測n型Bi28.8Te43.8Se27.4熱電材料熱電特性，其席貝克係數為-459 V/K、導電率為6.23 103 Ω-1cm-1，故功率因子為1.32  10-3 W/K2m，其值為二元p型Bi2Te3的11.3倍；p型 Bi20.1Te46.7Se33.2熱電材料，席貝克係數為407 V/K、導電率為7.36 103 Ω-1cm-1，故功率因子為1.22 10-3 W/K2m，其值為二元p型Sb2Te3的2倍。上述的實驗結果證實，二元熱電材料Bi2Te3在添加SeO2下，對於熱電特性有良好的改善效果。 將已知熱電特性的熱電材料，藉由電化學沉積技術搭配微機電製程與覆晶接合技術，成功研製出24對的三維微致冷晶片，其熱電接腳尺寸為200 m的方形陣列，電鑄高度約為10 m，後續將製作完成元件並量測其致冷性能，並比較在不同通過電流條件下的致冷能力。In this study, n-type and p-type Bi-Te-Se ternary thermoelectric materials are electroplate by added SeO2 electrochemical deposition method. The effect of SeO2 added on electroplated film, surface and component ratio were discussed in this thesis. Measured thermoelectric properties of ternary thermoelectric materials which Seebeck coefficient, conductivity and thermal conductivity by parallel line method. Therefore, the ternary thermoelectric materials with known properties were applied to fabricate micro-cooler by MEMS process and flip chip bonding technique. The concentration of Bi2O3, TeO2 and SeO2 metal powder was 7.5 mM, 10 mM, and 3 mM. The experiments confirmed electroplate thin film analysis, added SeO2 could improve the thermoelectric properties. The added concentration of SeO2 is 3 mM. The material propertiy is p-type when the current density under 1 mA/cm2. The material propertiy is n-type when current density is higher than 1.85 mA/cm2. The measurement results, the n-type Bi28.8Te43.8Se27.4 electroplated films exhibited the Seebeck coefficients of -459 μV/K, conductivity of 6.23 103 Ω-1cm-1 and a maximum power factor of 1.32×10−3 W/K2m, the value is 11.3 times of Bi2Te3. The p-type Bi20.1Te46.7Se33.2 electroplated films exhibited the Seebeck coefficients of 407 μV/K, conductivity of 7.36 103 Ω-1cm-1 and a maximum power factor of 1.22×10−3 W/K2m, the value is double of Sb2Te3. In Bi2Te3 material, the thermoelectric characteristic could be improved by adding SeO2. Micro-coolers with 24 Bi28.8Te43.8Se27.4/ Bi20.1Te46.7Se33.2 pairs were fabricated by electrochemical deposition, MEMS techniques and flip chip bonding techniques, in which the dimension of the thermoelectric legs is 200 m and thickness of the electroform is 10 m. Furthermore, the comparison of the cooling capability under different conditions will be measured.