Bi2Te2.55Se0.45熱電材料與Cu/Ag電極之薄膜固液擴散接合研究

Thin Film Solid-Liquid Interdiffusion Bonding of Bi2Te2.55Se0.45 Thermoelectrical Material with Cu/Ag Electrode

林哲緯(Che-Wei Lin)

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/碩士(2011年)

https://doi.org/10.6342/NTU.2011.01371

摘要

熱電材料即近年興起的一種再生能源，它是一種能將熱能與電能互相轉換之材料，此種材料可應用於溫差發電及熱點致冷兩種主要用途。而由於熱電元件將在高溫環境下操作，在元件和電極之間，傳統之軟、硬焊接合方法面臨許多的挑戰。本研究遂於Bi2Te2.55Se0.45熱電材料上電鍍Ni後，採用Ag/Sn薄膜作為固液擴散接合技術之材料，並和Cu/Ag電極接合，利用其低溫接合，高溫應用的特性，接點之介金屬將在相對低溫即可產生，同時在高溫仍然可以保有其穩定性。實驗探Bi2Te2.55Se0.45/Ni以及Ag/Sn薄膜與Cu/Ag電極之界面反應觀察，計算介金屬生長動力學，以及針對不同接合參數下之接點強度做量測。
實驗結果顯示，於Bi2Te2.55Se0.45熱電材料與Ni層間電鍍一層Sn，將能有效改善Bi2Te2.55Se0.45及Ni層之界面強度，此Sn層將和Bi2Te2.55Se0.45生成Sn(Te,Se)，並和Ni生成Ni3Sn4。於250°C以上之溫度接合3分鐘以上，Bi2Te2.55Se0.45/Sn/Ni/Ag與Sn/Ag/Cu接合之界面即可把中間4μm之Sn層完全消耗完畢並形成Ag3Sn、Cu6Sn5及Cu3Sn三種介金屬，其中250°C、275°C時隨著接合時間上升，Ag3Sn及Cu3Sn將消耗Cu6Sn5而逐漸增厚，Cu6Sn5將快速被消耗殆盡；溫度為300°C、325°C時，隨著時間上升，Cu3Sn將消耗Ag3Sn而增厚。本系統之接點強度最高可以達到21.7 MPa，接合條件為250°C-60分鐘，於250°C接合時，平均強度可維持在19 MPa以上。當溫度上升至325°C將使得Bi2Te2.55Se0.45及Ni層之間鍍Sn層的緩衝效果降低，導致接點強度將會快速下降至6.2 MPa。

關鍵字

熱電材料 ； 固液擴散接合 ； 介金屬化合物 ； 界面反應 ； 接點強度

並列摘要

Thermoelectrical materials is one of the renewable energy resourses which has been largely developed recently. It is a material which can transform heat energy to electrical energy reversibly.This materials have two major application:thermal energy and thermoelectric refrigeration. As there are more and more studies dedicate to this field, the energy transform efficiency of thermoelectrical materials has been gradually enhanced. Since thermoelectrical device usually operates in high temperature envi-ronment,the conventional jointing method (ex.soldering、brazing) have faced a lot of challenges. Therefore, this study uses Bi2Te2.55Se0.45 thermoelectrical material, adopts Ag/Sn thin films as the solid-liquid interdiffusion bonding materials joints with Cu/Ag electrode, and tries to make a use of the special feature of this technique : jointing in a relative low temperatures; operating in a relative high temperatures. The intermetallic compounds (IMCs) between the substrates can form in a relative low temperatures but,once formed, they are stable in much higher temperatures. This investigation includes the interfacial reaction between Bi2Te2.55Se0.45 and nickel and between Ag/Sn thin films and Cu/Ag substrate, calculating the kinectic of intermetallic compounds and analysising the shear stress of devices jointing in different parameters.
The results show that electroplating a tin layer between Bi2Te2.55Se0.45 and nickel layer can dramatically enhance the shear strength of this interface. This tin layer form Sn(Te,Se) with Bi2Te2.55Se0.45 and form Ni3Sn4 with nickel. At the temperature above 250°C,3 minute will be enough to exhaust the 4μm tin layer between two substrates. The intermetallic compounds formed at the interface between Cu/Ag/Sn and Ag/Ni/Sn/Bi2Te2.55Se0.45 are Ag3Sn、Cu6Sn5 and Cu3Sn. At 250°C、275°C, as the jointing increase, Ag3Sn and Cu3Sn will consume Cu6Sn5 and get thicker gradually, Cu6Sn5 will be exhausted rapidly. At 300°C、325°C, since there are no Cu6Sn5 anymore, as the jointing increase, Cu3Sn will start to consume Ag3Sn. Sound shear strength of 21.7 MPa have been obtained under bonding condition at 250°C for 60 minute. At 250°C,the average shear strengths can maintain over 19 MPa. Heating at the temperature above 325°C caused the tin buffer layer between Bi2Te2.55Se0.45 and nickel lost its functionality, and the shear strength drastically droped off to 6.2 MPa.

並列關鍵字

thermoelectrical material ； solid-liquid interdiffusion bonding ； intermetallic compound ； interfacial reaction ； bonding strength

參考文獻

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