熱電材料與銅電極之固液擴散接合研究

Thin Film Solid-Liquid Interdifusion Bonding of Thermoelectric Materials with Cu Electrode

楊忠霖(Chung-Lin Yang)

指導教授 ： 莊東漢

國立臺灣大學/工學院/材料科學與工程學研究所/博士(2013年)

https://doi.org/10.6342/NTU.2013.11135

摘要

熱電材料是近年來興起的一種綠色能源，能將熱能與電能互相轉換，傳統熱電材料與電極間的接合方式以軟銲或硬焊為主，由於熱電材料在高溫下操作，因此軟銲及硬焊皆有其不適用的地方，為了克服傳統接合的缺失，本研究使用低熔點金屬薄膜Sn以及In，Ag為高熔點金屬以固液擴散接合的方式將熱電材料與Cu電極接合，所選用的熱電材料為低溫熱電材料Bi0.5Sb1.5Te3及中溫熱電材料GeTe(Pb)，各接合條件下的界面微結構分析、介金屬動力學分析、接合強度測試、以及破斷面分析，最後還有電阻量測都將被探討。

實驗結果顯示，經過固液擴散接合之接點已全部反應成高熔點之介金屬，Ag/Sn/Ag接點生成Ag3Sn介金屬，其熔點可達480℃，時效至275℃時間1000小時Ag3Sn已轉成熔點更高的介金屬Ag5Sn (724℃)，而Ag/In/Ag接點則生成熔點為660℃以上的Ag9In4介金屬，可滿足日後熱電材料在高溫環境下使用接點熔化的問題，因此達到固液擴散接合「低溫接合，高溫使用」的目的。除此之外，本研究以預鍍Sn製程增強Ni層與熱電材料間的鍵結力，以及增加接合壓力這兩種方式大幅提高了接合強度及穩定性，斷面顯示都在預鍍Sn擴散層端甚至深達熱電材料內部。接合後的試片進行電阻量測，發現各系統接合界面接觸電阻率占整體電阻率3%左右，對於日後熱電模組效率影響甚小，藉由接合界面接觸電阻率也可知道經過固液擴散接合後各系統的接合品質良好。

關鍵字

固液擴散接合 ； 熱電材料 ； 界面反應 ； 強度測試 ； 電阻量測

並列摘要

Thermoelectric materials have gained attention in recent years for use in green energy applications that involve the exchange of heat energy and electrical energy. Traditionally, soldering or brazing methods are employed for the bonding of thermoelectric materials with electrodes. However, because thermoelectric materials operate at high temperature, soldering and brazing methods are not applicable. In order to overcome the shortcomings of traditional bonding methods, researchers have developed a novel bonding technique called solid-liquid interdiffusion bonding (SLID). This study employs Sn or In as a low-melting point metallic thin-film interlayer and Ag as a high-melting point metallic via SLID method to bond thermoelectric materials and Cu electrode. Bi0.5Sb1.5Te3 and GeTe(Pb) thermoelectric materials are employed as the low-temperature thermoelectric material and middle-temperature thermoelectric material, respectively. The morphology of the intermetallic compounds that formed at the interfaces after various SLID conditions were observed and their chemical compositions were analyzed. In addition, the shear strengths during SLID of the TE modules were measured to evaluate the bonding ability of the specimens, and the electrical resistance was also analyzed.

Experimental results indicated that the Ag/Sn/Ag or Ag/In/Ag joints formed high melting point intermetallic compounds. The melting point of Ag3Sn intermetallic compound is 480oC; Ag3Sn transforms to a higher melting point (724oC) Ag5Sn phase after aging at 275oC for 1000 hrs; and the Ag/In/Ag joint formed intermetallic compound Ag9In4, which has a melting point of 660oC. This approach fully achieved bonding at low temperature and application at high temperature. In addition, a Sn pre-coating process was used to enhance the bonding force between thermoelectric materials and Ni, and the bonding strengths were increased by increasing the bonding pressure. Shear strength tests indicated that the fracture face occurred at the pre-coating Sn alloy or thermoelectric materials matrix. The electrical contact resistivity of the bonding interface was less than 3% of the total electrical resistivity. This small proportion implies that the bonding performance is quite good during SLID.

並列關鍵字

solid-liquid interdiffusion bonding ； thermoelectric materials ； interface reaction ； strengh test ； electrical resistance measurement

參考文獻

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