Investigation of reduction mechanisms and current stressing properties of self-assembled carboxylate-protected silver nanoparticles

By utilizing the drastically reduced sintering temperature of nano-sized particles (NPs), one of the trends in microelectronic packaging is to manufacture highly conductive interconnections at a low processing temperature using noble metallic nanoparticles. In order to obtain excellent electrical conductivity for nanoparticle deposits, the surfactants have to be removed and the particles should be well linked. To prevent heat damage of the substrates and components, this study developes innovative reduction techniques for interconnections on flexible substrates (polymers and paper) suitable for roll-to-roll processes. temperature reduction/coalescence of carboxylate-protected Room Ag nanoparticles in ambiance, including kinetics as well as the mechanisms, is systematically investigated. Particle coalescence and thus good electrical conductivity for the Ag nanoparticles can be effectively achieved in several minutes by selected reductants, ascorbic acid solution and liquid formic acid at room temperature. Experimental results indicate that the ways for surfactant desorption are different for chemical reduction and thermal reduction, thereby the carboxylates with long carbon chains are easy to remove in chemical reduction but difficult to desorb thermally. In situ synchrotron radiation XRD, TGA, and image analysis are applied to estimate the activation energy for reduction and particle coalescence. The calculated activation energy for decanoic acid-protected Ag nanoparticles chemically reduced by ascorbic acid solution is about 69.2 KJ × mole-1, similar to that for grain boundary diffusion of Ag. Current-stressing performance of the reduced Ag tracks through various methods are also evaluated, including high voltage pulse, and critical current to failure. The amount of residual surfactants and the grain size of the sintered Ag are important factors affecting the electrical properties. When the residual amount of surfactants is low, reduced Ag tracks with large grains possess low electrical resistivity and high critical current again fusion.利用奈米金屬粒子之低熔點與低燒結溫度特性為現今微電子導線發展相當 重要的一環。奈米金屬粒子並非良導體，需移除表面活性劑並達到粒子間充分融合，其沉積物才會具有良好電導性。配合軟板基材(高分子以及 紙)roll-to-roll 製程，本研究針對羧酸保護銀奈米粒子進行常溫還原/融合創新技術開發與學理探討，深入調查還原過程中保護劑脫附與粒子融合行為與動力學解析，釐清羧酸碳鏈長度效應並比較化學還原與熱還原的機制差異。實驗結果發現碳鏈長短對化學還原與熱還原之影響不一致。利用熱重分析(TGA)以及同步輻射 XRD 觀察粒子熱還原行為，估算不同碳鏈之烷羧酸保護銀奈米粒子之保護劑脫附以及粒子融合 (coalescence) 活化能。推斷奈米銀粒子於熱還原過程中保護劑脫附為由終端開始熱裂解，碳鏈越長越難脫附，奈米粒子還原/融合的活化能亦因而較高。化學還原之趨勢卻恰恰相反，碳鏈越短越難脫附。選用 ascorbic acid 溶液或液態 formic acid 做為還原劑可有效於室溫將奈米粒子沈積物還原成良導體。以 ascorbic acid 溶液浸泡進行正癸酸保護粒子還原之活化能估算為 69.17KJ/mol 接近銀的晶界擴散活化能。以 FTIR 鑑定 formic acid 還原月桂酸保護粒子過程中官能基變化，推測化學還原機制為吸附於粒子表面之羧酸根由還原劑獲得氫離子直接脫附，碳鍊較短之羧酸根鹼性較低，因而脫附較不易。本研究亦對於不同還原方法製備之銀導線承受高壓脈衝與臨界電流進行通電可靠度分析。結果顯示保護劑的殘留以及晶粒徑為電性表現之影響要因，當殘留量少時，晶粒徑較大者具有較低的電阻率與較高的臨界燒斷電流。摘要 ........................................................ i Abstract ........................................................ii 總目次 ...................................................... iv 表目次 ....................................................... vi 圖目次 .......................................................vii 第一章 緒論 ........................................................ 1 第二章 文獻回顧 ......................................................... 3 2.1. 金屬奈米材料...................................................... 3 2.1.1.奈米材料性質與發展現況 ....................................................... 3 2.1.2. 金屬奈米粒子製備方法 ........................................................ 3 2.1.3. 銀奈米粒子 ....................................................... 4 2.2. 自組裝單層分子保護銀奈米粒子 ........................................................ 4 2.2.1. 自組裝單層分子 (Self-assembled monolayers, SAMs) ............ 4 2.2.2. 烷羧酸保護銀奈米粒子 ......................................................... 5 2.3.奈米金屬還原與融合行為 ......................................................... 6 2.3.1. 保護劑效應及還原行為 ......................................................... 6 2.3.2. 金屬奈米粒子融合行為 ................................................. 7 2.3.3. 影響金屬奈米粒子還原之因素 ................................................. 7 2.3.4. 化學還原與光還原 ......................................... 9 2.4. 奈米金屬燒結導線之電性與可靠度 .................................................. 10 第三章 實驗目的與方法 ....................................................... 27 3.1. 奈米粒子合成...................................... 27 3.1.1. 合成以羧酸為保護劑之銀奈米粒子 (Ag-O2CX, X=8,10,12) ...................................................... 27 3.1.2. 奈米粒子粗製物清洗 ....................................................... 27 3.2. 試片製備與奈米粒子還原方法 ....................................................... 27 3.2.1. 基板清洗 ....................................................... 27 3.2.2. 旋轉披覆 ....................................................... 28 3.2.3. 熱還原方法 ........................................................ 28 3.2.4. 化學還原方法 ....................................................... 28 3.3. 儀器與樣品製備 ........................................................ 28 3.3.1. 紫外/可見光吸收光譜儀 ...................................................... 28 3.3.2. 場發射穿透式電子顯微鏡 ....................................................... 29 3.3.3. 傅立葉轉換紅外光譜儀 ................................................ 29 3.3.4. 熱重分析儀 (Thermal gravity analysis, TGA) ........................ 30 第四章 實驗結果與討論 ........................................................ 36 4.1. 烷羧酸保護銀奈米粒子性質鑑定 ...................................................... 36 4.2 烷羧酸保護銀奈米粒子熱還原融合行為 ............................................ 36 4.2.1.奈米粒子升溫過程中保護劑脫附動力學探討 ......................... 36 4.2.2. 以臨場同步輻射 X 光繞射探討粒子融合行為 ...................... 36 4.2.3. 熱還原動力學分析 ...................................................... 37 4.3 烷羧酸保護銀奈米粒子化學還原融合行為 ........................................ 38 4.3.1. 化學分析電子能譜儀 ...................................................... 38 4.3.2. 低掠角 X 光繞射圖譜 ................................................... 38 4.3.3. 銀奈米粒子化學還原動力學探討 ........................................... 39 4.3.4. 化學還原官能基變化與機制探討 ........................................... 40 4.3.5. 熱還原與化學還原機制比較 ................................................... 40 4.4 化學還原與熱還原比較 ................................................. 41 4.4.1. 熱分析 .................................................. 41 4.4.2. 奈米粒子還原後之顯微形貌與電性 ....................................... 41 4.4.3. 奈米銀導線之可靠度測試 ....................................................... 42 4.4.4. 還原方式與導線組織及電性相關性探討 ............................... 42 第五章 結論 ....................................................... 63 第六章 參考文獻 ..................................................... 6

Ball Impact Reliability of Zn-Sn High-Temperature Solder Joints Bonded with Different Substrates

In this study, the high-speed deformation behavior of solder joints formed withPb-free Zn-Sn and commercial Pb-Sn alloys bonded on different substrateswas investigated by the ball impact test method. Overall, Zn-Sn jointsexhibited greater impact strength but inferior impact toughness than Pb-Snjoints. This can be ascribed to the high hardness of Zn-Sn solders resulting inpartial or overall interfacial fracture. In contrast, the joints with soft Pb-Snsolders all showed a ductile fracture feature. It is suggested that, for the jointsrevealing brittle fracture, the impact toughness (impact energy) increasedwith the plastic ability of interfacial intermetallic compounds, while for thoseshowing a ductile fracture mode, the impact energy deteriorated with ahardened solder matrix resulting from substrate dissolution

Kinetic study on low temperature coalescence of carboxylate-protected Ag nanoparticles for interconnect applications

Reduction and coalescence for carboxylate-capped Ag nanoparticles can be achieved in several minutes by soaking the nanoparticle deposits in ascorbic acid aqueous solution. The reduced deposits exhibit a low electrical resistivity in the same order as with bulk Ag. The effect of the chain length of the carboxylates and the kinetics of particle coalescence were explored in this study. Bendable conductive films can be fabricated on a PDMS substrate using this low temperature chemical reduction method

HACE1 deficiency leads to structural and functional neurodevelopmental defects

Objective We aim to characterize the causality and molecular and functional underpinnings of HACE1 deficiency in a mouse model of a recessive neurodevelopmental syndrome called spastic paraplegia and psychomotor retardation with or without seizures (SPPRS). Methods By exome sequencing, we identified 2 novel homozygous truncating mutations in HACE1 in 3 patients from 2 families, p.Q209{*} and p.R332{*}. Furthermore, we performed detailed molecular and phenotypic analyses of Hace1 knock-out (KO) mice and SPPRS patient fibroblasts. Results We show that Hace1 KO mice display many clinical features of SPPRS including enlarged ventricles, hypoplastic corpus callosum, as well as locomotion and learning deficiencies. Mechanistically, loss of HACE1 results in altered levels and activity of the small guanosine triphosphate (GTP)ase, RAC1. In addition, HACE1 deficiency results in reduction in synaptic puncta number and long-term potentiation in the hippocampus. Similarly, in SPPRS patient-derived fibroblasts, carrying a disruptive HACE1 mutation resembling loss of HACE1 in KO mice, we observed marked upregulation of the total and active, GTP-bound, form of RAC1, along with an induction of RAC1-regulated downstream pathways. Conclusions Our results provide a first animal model to dissect this complex human disease syndrome, establishing the first causal proof that a HACE1 deficiency results in decreased synapse number and structural and behavioral neuropathologic features that resemble SPPRS patients