熱電模組(thermoelectric modules)能直接將熱能轉換成電能使用，是一極具潛力的廢熱回收裝置。熱電模組的構成，是將P-N熱電材料元件連接於金屬基材上，因此熱電模組中存在許多接點，接點的性質對於熱電模組的可靠度具有相當大的影響。由於熱電模組的應用溫度較高，以中溫型熱電材料為例，應用溫度為300oC~500oC，高於傳統含錫軟銲合金的連接溫度，因此並不適用於熱電模組的連接製程，而銀銅硬銲合金的連接溫度過高，超過熱電材料的熱穩定性範圍，可能對熱電材料本身的性質造成破壞，因此熱電模組的連接製程須具備「連結製程溫度不能高，卻要在高溫進行應用」的條件。固液擴散接合(solid-liquid interdiffusion bonding, SLID bonding)具有上述特性，其概念為將銲料加熱熔融成液態，在欲連接的金屬間發生液固界面反應，進而生成介金屬相轉變為固態、完成連接製程，因此值得我們深入去探討應用在熱電模組中的可行性。在熱電模組的構成中，為了避免熱電材料與銲料接觸發生反應，通常會於銲料與熱電材料之間引入阻障層(diffusion barrier layer)。因此本研究專注於研究金屬基材、銲料以及阻障層之間的界面反應情形，選用Cu作為金屬基材，Ga作為銲料，Co、Ni則為常見之阻障層材料，對Cu/Ga/Co及Cu/Ga/Ni相關的界面反應與相平衡系統進行研究。
　　Cu/Ga的界面反應部分，於200oC之實驗結果中，觀察到3-Cu9Ga4以及CuGa2之反應層；在350oC則是生成2-Cu9Ga4為反應層；於500oC觀察到1-Cu9Ga4的反應層。Co/Ga的界面反應於200oC並無觀察到反應層的生成情形；於350oC及500oC反應皆生成介金屬相CoGa3之反應層。Ni/Ga界面反應中，在200oC和350oC的實驗結果皆發現Ni3Ga7的單一反應層；而在500oC的界面反應中則生成介金屬相Ni2Ga3之反應層。Cu/Ga/Co於200oC的界面反應中，觀察到3-Cu9Ga4以及CuGa2之生成相，並無觀察到Co相關的介金屬相生成；在350oC的反應中觀察到2-Cu9Ga4以及CoGa3之反應層 ；於500oC則觀察到1-Cu9Ga4以及CoGa3的生成情形。Cu/Ga/Ni界面在200oC的反應中生成3-Cu9Ga4、CuGa2，並無觀察到Ni相關之介金屬相；於500oC則觀察到2-Cu9Ga4以及Ni3Ga7的生成情形，在500oC的Cu/Ga/Ni界面反應中則生成1-Cu9Ga4以及Ni2Ga3的介金屬相為反應層。
在Co-Cu-Ga的等溫橫截面圖的建構中，本研究以計算相圖 (Calculation of phase diagram, CALPHAD)的方法，蒐集並評估相關的二元參數，彙整在一起計算出Co-Cu-Ga於200oC、350oC及500oC時的等溫橫截面圖，以確立初步的相平衡關係，並進一步以實驗方法，建構出Co-Cu-Ga於500oC的等溫橫截面圖，其中包括五個三相區: -Co+Cu+CoGa、Cu+CoGa+-Cu7Ga2、CoGa+-Cu7Ga2+1-Cu9Ga4、CoGa+1-Cu9Ga4+CoGa3、1-Cu9Ga4+CoGa3+Liquid，並沒有三元相產生。

Thermoelectric modules can convert heat into electricity directly and have great potential in waste heat recovery. Thermoelectric modules are composed of P-N arrays devices. Therefore, there are many joints in thermoelectric modules and are usually critical to the reliability. Solid-liquid interdiffusion (SLID) bonding, uses low melting temperature solders. The solders melt at the joining temperatures, and are completely consumed after a certain length of reaction time. The solid-liquid interdiffusion bonding is thus conducted at lower temperatures, and the modules can be used at relatively higher temperatures, and is a potential joining technology for thermoelectric modules. At the joints, the solders are connected to the barrier layer, Ni or Co, and the Cu plate. When Ga is used as a solder, the possible structures of the joints are Cu/Ga/Ni and Cu/Ga/Co. This study examines the interfacial reactions in the Cu/Ga/Ni and Cu/Ga/Co samples. The results are fundamentally important for processing optimization and assessment of products’ reliability if Ga solid-liquid interdiffusion bonding is used.
The interfacial reactions in the Cu/Ga, Co/Ga and Ni/Ga couples and Cu/Ga/Co and Cu/Ga/Ni sandwich samples were examined at 200oC, 350oC and 500oC. In the Cu/Ga couples, 3-Cu9Ga4 and CuGa2 phases are the reaction phases at 200oC. The 2-Cu9Ga4 reaction layer was formed in the couples reacted at 350oC and the 1-Cu9Ga4 reaction layer was formed at 500oC. In Co/Ga reactions, no reaction phase layer was found at 200oC, but CoGa3 is the reaction phase obseved at 350oC and 500oC. In the Ni/Ga couples, Ni3Ga7 was formed in those reacted at 200oC and 350oC while Ni2Ga3 was formed at 500oC. In the Cu/Ga/Co sandwich couples, 3-Cu9Ga4 and CuGa2 are the reaction phases at 200oC. 2-Cu9Ga4 and CoGa3 were formed at 350oC while 1-Cu9Ga4 and CoGa3 were formed at 500oC. In the Cu/Ga/Ni sandwich samples. 3-Cu9Ga4 and CuGa2 phases were formed at 200oC, 3-Cu9Ga4 and Ni3Ga7 were formed at 350oC, and 1-Cu9Ga4 and Ni2Ga3 were formed at 500oC.
By the calculation of phase diagram (CALPHAD) method, isothermal sections of Co-Cu-Ga at 200oC, 350oC and 500oC were established. And isothermal section of Co-Cu-Ga at 500oC were also established by experimental method. Five tie-triangles: -Co +Cu+CoGa、Cu+CoGa+-Cu7Ga2、CoGa+-Cu7Ga2+1-Cu9Ga4、CoGa+1-Cu9Ga4+CoGa3、1-Cu9Ga4+CoGa3+Liquid are determined. No ternary compound is found in this study.

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