碳化矽等高溫電子元件具有高溫穩定性，可用於地底探勘、電動車與航太科技等高功率嚴苛環境中。高鉛合金之物化性質良好，傳統上常用於高溫電子元件之固晶材料，然而鉛對人體與環境有害，歐美日等國紛紛立法禁止含鉛之電子產品，雖然目前因為仍無可靠的替代材料，高鉛銲料得以暫獲豁免，但開發高溫無鉛銲料的研究需要立即性的投入。金鍺合金具有良好電、熱性質，其共晶點達361 oC，可與高溫電子元件相匹配，為極具潛力的高溫無鉛銲料，而銅為工業中常見的基材材料，金鍺合金與銅基材之間的界面反應顯得更為重要。本研究以反應偶實驗方法探討金鍺共晶合金與與銅基材在400 oC下之界面反應，以模擬固晶製程中的焊接過程，測定界面生成相的種類與觀察其型態，並提出界面反應與反應相成長的機制。於此反應中總共有三個不同的相生成，為F.C.C.-(Au, Cu, Ge)、ζ相以及位於ζ/Cu界面處之X相。同時為了鑑定生成相在相圖上的位置，對於Au-Cu-Ge在400 OC下之等溫橫截面圖進行SEM影像觀察、EPMA成分相鑑定以及XRD結構分析。同時觀察金鍺合金與銅基材在300 OC之下之固固界面反應。

Silicon carbide (SiC) has superior physical properties, low power loss, and high stability at high temperatures, so the SiC-based devices are commonly used in high power applications and under harsh environments, such as aerospace and oil-drilling. Conventionally Pb-Sn alloys containing 85 – 97 wt. % Pb, so-called “high-Pb solders”, are used as die attach solders in SiC-based electronics. However, Pb is proven to be harmful to the environment and human health. As the result, the eutectic and near-eutectic Pb-Sn alloys have been banned by the RoHS from the European Union (EU) and other countries worldwide. Despite the neural toxicity of Pb and the higher Pb contents in the “high-Pb solders”, currently there is no high temperature Pb-free alternative for the industry and “high-Pb solders” are temporarily exempted from the regulations. The eutectic point of the Au-Ge system at 361OC is higher than the liquidus temperatures of the high-Pb solders and thus the eutectic Au-Ge alloy can fulfill the requirement of SiC-based devices at high operation temperatures. Moreover, the eutectic Au-Ge alloy is recently reported to be with good wettability, electrical performance, and mechanical properties. Therefore, the eutectic Au-Ge alloy is considered to be one of the most promising Pb-free die attach materials for high temperature and high power applications. In the study, we examined the soldering reactions between eutectic Au-Ge alloy and Cu substrate. The Au-12Ge/Cu reaction couples are prepared and annealed at 400 OC under vacuum for various predetermined lengths of time. The interfacial morphologies as well as the compositions of the intermetallic compounds (IMCs) formed at the joints were analyzed with optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and electron probe microanalysis (EPMA), respectively. At initial stage of the reactions, a scallop-type ternary FCC solid solution formed at on the top on the Cu substrate surface. The FCC solid solution was identified as a ternary extension of the F.C.C.-(Au, Cu, Ge) continuous solid solution from the Au-Cu binary system. Following the formation and growth of the F.C.C.-(Au, Cu, Ge) phase, a planar ζ phase formed between Cu substrate and F.C.C.-(Au, Cu, Ge) phase and thus the Cu/liquid couple became Liquid/F.C.C.-(Au, Cu, Ge)/ζ/Cu. After longer annealing time, the X phase form between ζ/Cu, and the ζ was differentiate to two parts. In order to identify those IMCs formed in the reaction, the isothermal section of Au-Cu-Ge system at 400 OC is proposed. In the third part of this thesis, Au-12Ge/Cu solid/solid reaction couples are prepared and annealed at 300 OC under vacuum for various predetermined lengths of time. The interfacial morphologies as well as the compositions of the IMCs formed at the joints were analyzed.

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