| 摘要: | 隨著碳化矽與氮化鎵等寬能隙功率元件的快速發展，封裝材料需承受更高的操作溫度與電流密度的要求日益提升。傳統焊料，如高鉛焊料或含金合金，受限於環保、成本與可靠性等問題。雖然已有數種無鉛高溫焊料作為替代方案被提出，但仍存在製程溫度高、可靠性差或界面不穩定等缺點。因此，銅奈米粒子燒結因其優異的導電與導熱性能、高抗電遷移能力及低成本，被視為極具潛力的替代技術。
本研究以抗壞血酸作為還原劑，進行綠色合成奈米銅粒子，並探討 pH 值與反應時間等合成參數對粒徑與粒徑分布的影響。同時提出一套模型，用以評估粒徑與表面能與氧化物還原能之間的關係。為找出能達到最高剪切強度與最緻密燒結結構的最佳粒徑，本研究將奈米銅粒子與聚乙二醇混合製成銅膠，並在 300 °C 下、氮氣環境中進行一小時的低溫無壓 Cu-Cu 直接接合。此外，亦製備不同溶劑條件下的奈米／微米銅混合膠，探討溶劑極性對顆粒分散行為的影響。實驗結果顯示，溶劑極性對銅粒子的分散、燒結後微結構與接合品質皆有顯著影響。為進一步提升混粉銅膠的燒結效果，本研究亦引入電流輔助燒結技術，使其燒結後的微結構可媲美純奈米銅膠的結果。此外，研究也評估了混合銅膠在電遷移可靠性方面的表現，並發現隨著溫度升高，電遷移主導的失效機制逐漸明顯。;With the rapid development of wide-bandgap (WBG) power devices, such as SiC and GaN, packaging materials are increasingly required to withstand higher operating temperatures and current densities. Traditional solders, including high-lead or Au-based alloys, are limited by environmental concerns, cost, and reliability issues. Although several lead-free high-temperature solder alternatives have been proposed, they often suffer from drawbacks such as high processing temperatures, poor reliability, or interfacial instability. As a result, copper nanoparticle (Cu NP) sintering has emerged as a promising alternative due to its excellent electrical and thermal conductivity, high electromigration resistance, and low cost.
This study focuses on the green synthesis of Cu NPs using ascorbic acid, investigating how synthesis parameters such as pH and reaction time influence particle size and distribution. A model was proposed to evaluate the relationship between surface energy and oxide reduction energy as a function of particle size. To identify the optimal particle size for achieving the highest shear strength and densest sintered structure, Cu NPs were mixed with polyethylene glycol (PEG) solvent to form a Cu NP paste, and low-temperature, pressureless Cu-to-Cu direct bonding was carried out at 300 °C for 1 hour under a nitrogen atmosphere. Cu nano/micro particle mixed pastes were also prepared using different solvents, and the influence of solvent polarity on particle dispersion was investigated. The results showed that solvent polarity significantly affects particle dispersion, sintering microstructure, and joint quality. To further improve the sintering performance of the Cu mixed paste, electrically assisted sintering was introduced, resulting in a microstructure comparable to that achieved by pure Cu NP sintering. In addition, the electromigration reliability of the Cu mixed paste joints was evaluated, revealing failure mechanisms that became dominant at elevated temperatures. |
