覆纳米银铜粉焊膏的制备及其连接性分析

提出将纳米银与覆纳米银铜粉按照比例混合制备焊膏,用于低温连接纯度为99.99%的无氧紫铜板:首先利用液相化学还原法制备出平均粒径为20~35 nm的纳米银颗粒,同时利用化学镀制备覆纳米银铜粉颗粒.之后将纳米银与覆纳米银铜粉机械混合制备焊膏并在200℃烧结温度,10 MPa压力,保温30 min条件下烧结连接无氧紫铜板,并与纳米银焊膏单独烧结情况做对比分析,通过扫描电镜(SEM)观察连接接头形貌,其中纳米银与覆纳米银铜粉混合焊膏得到的烧结接头界面连接紧密,接头组织内有一定的孔隙率,其平均抗剪强度达20 MPa.     

低温烧结纳米铜焊膏的制备及其连接性能分析

甲酸处理铜纳米颗粒的方法制备可低温烧结的纳米铜焊膏可用于低温连接大功率器件.首先利用改良后的多元醇法制备平均粒径为30 nm的铜纳米颗粒,然后利用甲酸浸泡去除铜纳米颗粒表面的氧化物,之后将铜纳米颗粒与乙二醇混合后制备固含量为70%的焊膏,并在160~320℃的烧结温度、10 MPa压力、保温5 min的条件下烧结连接DBC陶瓷基板和金属化的SiC芯片.结果表明,通过扫描电镜和透射电镜观察连接接头形貌,烧结接头内部烧结组织粗大,烧结铜层和铜焊盘的界面通过冶金结合紧密连接,形成了拥有高抗剪强度、高导电性的连接接头.     

微米氧化银膏原位生成纳米银的低温烧结连接

为降低纳米银膏用于低温烧结电子互连封装的成本,用较低廉的微米级Ag2O粉末与三甘醇配制成膏.文中研究了其原位生成纳米银的反应机理、低温烧结特性并用其低温烧结连接镀银铜块.结果表明,三甘醇还原微米级Ag2O原位生成纳米银的温度远低于Ag2O粉本身的分解温度,同时生成可以逸出的气体,且随温度升高和保温时间延长,生成的银颗粒增多并逐渐烧结长大形成颈缩式颗粒.在烧结连接温度250℃和外加压力2 MPa条件下,烧结保温时间延长可显著提高接头强度,保温5 min可获得抗剪强度为24 MPa的接头,并对典型条件下的接头断口和横截面显微组织结构进行了分析.     

Ag2O焊膏中添加镀银铜粉的低温烧结连接及其性能

微米尺寸Ag₂O焊膏相对于纳米银焊膏成本低廉且在高温电子互连封装行业中有应用前景.为了进一步降低连接成本及提高接头的抗电化学迁移能力,向Ag₂O焊膏中加入镀银铜粉制得了新型混合焊膏.文中对比了用原有微米尺寸Ag₂O焊膏与加入镀银铜粉后的新型混合焊膏连接所得接头的抗剪强度以及两种焊膏烧结后的抗电化学迁移能力.结果表明,在连接温度为250℃时,用含镀银铜粉的混合Ag₂O焊膏连接的接头抗剪强度下降明显,但焊膏烧结后的抗电化学迁移能力获得显著提升,水滴试验结果表明其电迁移短路时间延长了一倍以上.     

SAC305-纳米铜复合焊膏焊后性能及孔隙形成机理

通过在SAC305焊膏中添加纳米铜,研究其对SAC305焊膏焊后焊点微观组织、孔隙率及力学性能的影响,并对焊点中空隙的形成机理进行分析. 结果表明,纳米铜的添加明显细化了钎料中的β-Sn相和Ag3Sn化合物,且细化效果随纳米铜添加量的增加而更为显著. 焊点中的孔隙率随纳米铜添加量的增加呈逐渐增加的趋势,当添加量达到1%(质量分数,%)时,焊点中的孔隙率明显提升,比无添加的SAC305焊膏增加了2.2%. 添加纳米铜的SAC305复合焊膏焊后接头的抗剪强度在细晶强化作用下得到一定程度的提高,同时接头中增加的孔隙率又使其力学性能恶化;综合这两种因素,当纳米铜添加量为0.5%时,其力学性能较好,抗剪强度提高了10%.     

Ag-In复合焊膏的高温抗电化学迁移行为

低温烧结纳米银焊膏具有优越的热、电和力学性能，成为宽禁带半导体器件封装互连的关键材料之一，高服役温度下，烧结银的氧化和分解会引起电化学迁移的发生，可能导致电子器件的短路失效.在纳米银焊膏中添加氧亲和力更高的铟颗粒，采用竞争氧化的思路可以抑制烧结银的电化学迁移.与烧结纳米铟焊膏(382 min)相比，烧结Ag-3In和Ag-5In(质量分数，%)焊膏的电化学迁移寿命提高至779和804 min，提高约1倍；分析了铟粉对烧结银在高温干燥环境中电化学迁移失效的抑制机理.服役过程中，铟颗粒优先于银颗粒与氧气发生反应生成In₂O₃，从而抑制了烧结银的氧化、分解和离子化过程，显著提高了烧结银的电化学迁移失效时间，与此同时，与烧结银焊膏相比，烧结Ag-1In与Ag-3In(质量分数，%)焊膏的抗剪强度分别提升了30.92%和32.37%.结果表明，纳米铟粉的引入可以显著提高烧结银的电化学迁移寿命.     

多尺度纳米银烧结接头连接强度及塑性

以低温烧结连接使用的纳米银膏为研究对象,通过计算获得银膏中纳米银颗粒与微米银颗粒的最佳配比并制备复合银膏. 研究了银膏中不同溶剂对接头孔隙形成的影响,对比了纳米银膏与复合银膏硬度、弹性模量及塑性因子. 结果表明,在250 ℃的烧结温度下松油醇和酒精的混合有机溶剂有利于烧结接头质量的提升,其烧结层孔隙率明显低于乙二醇制备的复合银膏烧结接头. 与纳米银膏烧结接头相比,复合银膏烧结层压痕面积较大,硬度与弹性模量较低. 当烧结时间为10 ~ 30 min时,复合银膏烧结层塑性因子高于纳米银膏烧结层.     

用于IGBT焊接的具有高热导率的柔韧性纳米银膜

设计制备了一种新型的焊接材料——纳米银膜,其结构不同于以往纳米银焊膏的形式(预成形为片状),可韧性弯曲和自由剪裁。纳米银膜的银含量在w(Ag)80%左右,所选用的纳米银粉平均粒径为20 nm,其余组成部分是含有不同官能团的有机物质。采用0.1 mm厚的纳米银膜模拟绝缘栅双极晶体管(IGBT)焊接试验,在280℃温度和10 MPa压力下真空保温30 min,烧结接头取得216W/(m·K)的热导率和53 MPa的抗剪强度。研究结果表明,纳米银膜能够直接焊接在无镀层处理的氧化铝陶瓷覆铜(DBC)基板上,且致密性良好,空洞率极低。结果研究进一步表明,纳米银膜具有低温烧结、高热导率和残渣率低的特点;纳米银膜能够有效替代传统合金焊料应用于功率半导体封装中。     

TiO2纳米掺杂对SAC105焊膏喷印流变特性及接头力学性能的影响

利用不同含量TiO2纳米颗粒掺杂的方法对SAC105焊膏进行改性,利用旋转流变仪、粘度仪等设备研究了改性焊膏的喷印流变特性,利用拉伸机、扫描电镜等设备研究了改性焊膏焊接接头的力学性能和微观结构.结果 表明,TiO2纳米颗粒掺杂改性SAC105焊膏焊接接头的剪切强度最高达71.4MPa,比未掺杂的SAC105接头剪切强度...     

Ag-Cu固溶体颗粒制备及低温烧结互连接头性能

通过液相化学还原法制备Ag-Cu固溶体纳米颗粒,采用低温热压烧结工艺制备“三明治”结构的互连接头.采用X射线衍射仪对所制备的Ag-Cu固溶体纳米颗粒及烧结体进行物相表征;采用能谱仪对所制备的Ag-Cu固溶体纳米颗粒的元素进行表征;采用纳米粒度仪对Ag-Cu固溶体纳米颗粒粒径进行表征;通过扫描电子显微镜对互连接头的烧结组织和剪切断面形貌进行观察,分析颗粒烧结情况和互连接头断裂模式. 结果表明,通过液相化学还原的方法实现了室温下铜在银中的超饱和固溶,其中Ag原子分数为62.29%,Cu原子分数为37.71%,远超常温下常规块体材料的固溶度. 所制备的纳米颗粒在250 ℃以内保持相对稳定的固溶体相,260 ℃时发生相分离. 当烧结温度为300 ℃、烧结压力20 MPa时,所获得的互连接头具有优异的力学性能,平均抗剪强度达到105 MPa,且烧结组织呈现完整的脉络状,剪切断面全部为韧窝状,属于韧性断裂.     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

THERMODYNAMICS STUDY ON THE DECOMPOSITION OF CHROMITE WITH KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

INFLUENCE OF HEAT TREATMENT ON DAMPING BEHAVIOUR OF THE MAGNESIUM WROUGHT ALLOY AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

An Easy Way to Quantify the Adhesion Energy of Nanostructured Cu/X(X=Cr,Ta,Mo,Nb,Zr) Multilayer Films Adherent to Polyimide Substrates

An approach based on film buckling under simple uniaxial tensile testing was utilized in this paper to quantitatively estimate the interfacial energy of the nanostructured multilayer films(NMFs) adherent to flexible substrates. The interfacial energies of polyimide-supported NMFs are determined to be *5.0 J/m2 for Cu/Cr, *4.1 J/m2 for Cu/Ta,*2.8 J/m2 for Cu/Mo, *1.1 J/m2 for Cu/Nb, and *1.2 J/m2 for Cu/Zr NMFs. Furthermore, a linear relationship between the adhesion energy and the interfacial shear strength is clearly demonstrated for the Cu-based NMFs, which is highly indicative of the applicability and reliability of the modified models.     

High-Speed Friction Stir Welding of SiC_p/Al–Mg–Si–Cu Composite

A 17 vol% SiCp/Al–Mg–Si–Cu composite plate with a thickness of 3 mm was successfully friction stir welded(FSWed) at a very high welding speed of 2000 mm/min for the first time. Microstructural observation indicated that the coarsening of the precipitates was greatly inhibited in the heat-affected zone of the FSW joint at high welding speed, due to the significantly reduced peak temperature and duration at high temperature. Therefore, prominent enhancement of the hardness was achieved at the lowest hardness zone of the FSW joint at this high welding speed, which was similar to that of the nugget zone. Furthermore, the ultimate tensile strength of the joint was as high as 369 MPa, which was much higher than that obtained at low welding speed of 100 mm/min(298 MPa). This study provides an effective method to weld aluminum matrix composite with superior quality and high welding efficiency.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

A STUDY OF TEMPERATURE-DEPENDENT VALENCE BOND STRUCTURE OF TITANIUM

On the basis of energy and shape method for the determination of the valence bond (VB) structures of crystal, the valence bond structure of titanium is redetermined at room temperature and calculated in the whole temperature range of 0-1943K. The outer shell electronic distribution of Ti is e_c~(2.9907) · (s_c~(0.4980) d_c~(2.4927)) ef1.0093 in crystal. The temperature dependences of the VB structures of hcp and bcc phases are the same. The VB structures of hcp and bcc phases monotonically increase or decrease with the increase in temperature, but show discontinuous changes at the phase-transformation temperature 1155K.