电子封装研究综述——从工业生产角度剖析电子封装技术的动向及未来…

以半导体工业学会为半导体工业制定的标准作为依据，描述了当前集成电路封装研究的现状。涉及到以下关键范围：设计、分析和模拟、降低供电电压，强化散热、区域阵列互连，芯片筛选，低成本高密度基极以及小型化的单片封装，除了以上这些范围，着重研究了设计，制造以及可靠性分析中有关的问题。     

In situ and air index measurements: influence of the deposition parameters on the shift of TiO2/SiO2 Fabry-Perot filters

We measure the refractive index of thin films of TiO2 and SiO2 for given deposition parameters. Two complementary methods are used. The first is a postdeposition technique which uses the measurements of reflectance and transmittance in air. The second, in contrast, makes use of in situ measurements (under vacuum and during the actual deposition of the layer). The differences between the values deduced from the two methods can be explained by the amount of atmospheric moisture adsorbed by films. One tries to minimize these shifts for the two materials by choosing deposition parameters. The difficulties come from the absorption losses which must be as small as possible. We use the measured refractive indices of individual layers to give good numerical prediction of the wavelength shift (observed during the admittance of air after deposition in the vacuum chamber) of the transmittance peak of multidielectric Fabry-Perot filters.     

海底实验室用钛合金厚板的焊接及评价

对α+β型厚为20～76毫米并且杂质极少的TA6V(Ti-6AL-4V)和α型621Mo(Ti-6AL-2Nb-TTa-1Mo)钛合金的轧制板,进行了焊接试验和鉴定。这些合金由美国研制成功,并在海水环境中得到了应用。研究了各种不同的熔化焊接法:钨极惰性气体保护焊(TIG),金属极惰性气体保护焊(MIG),等离子焊和电子束焊(FE)。由于焊前对焊接边缘进行了适当的处理,焊时对焊接接头实施了有效地保护,不论使用那一种焊接方法均没有出现特殊的问题,焊缝的致密性令人满意。对焊接接头进行了拉伸、压缩、裂纹扩展和应力腐蚀等鉴定试验,也没有发现任何可造成严重损害的异常现象。就基板而言,TA6V合金的焊接接头,虽然延伸率和断面收缩率降低了,静态强度性能却略有提高。而621Mo合金的焊接接头,其静态强度性能则与基板相同。抗裂纹的扩展能力大体上也是好的。——对了AGV合金,K_(IC)参数值的范围是50MPam1/2(基板厚20毫米)到88MPam1/2(TIC焊接)。——对621Mo合金,K_(IC)参数值的范围是70MPam1/2(基板厚76毫米)到90MPam1/23(用等离子法焊接)。这两种合金(焊接或非焊接态),在应力腐蚀下的抗裂纹扩展能力是好的。但是,对于K_(IC)参数值,621Mo合金显然要比TA6V合金好得多。对持厚板材的焊接,最好的焊接方法看来还是电子束焊和混合焊接法(第一道缝采用等离子焊,而后用MIG焊填充焊缝)。     

Nanomaterials based on phosphorus dendrimers

Dendrimers constitute an increasingly important field of research in chemistry for more than 15 years. After pioneering works concerning synthesis, the interest in dendrimers is now mainly driven by their properties and applications. This Account will emphasize the properties of a special class of dendrimers, that is, phosphorus-containing dendritic macromolecules, as tools for the elaboration of nanomaterials. Indeed, these dendrimers can be considered themselves as materials, or they can be used as an intrinsic constituent of a material or as a modifier of the surface of a material. In this latter case, a fundamental work about surfaces covalently modified by dendrimers recently opened the way to the elaboration of DNA chips.     

Interactions between immunoglobulin-like and catalytic modules in Clostridium thermocellum cellulosomal cellobiohydrolase CbhA

Cellobiohydrolase CbhA from Clostridium thermocellum cellulosome is a multi-modular protein composed starting from the N-terminus of a carbohydrate-binding module (CBM) of family 4, an immunoglobulin(Ig)-like module, a catalytic module of family 9 glycoside hydrolases (GH9), X1(1) and X1(2) modules, a CBM of family 3 and a dockerin module. Deletion of the Ig-like module from the Ig-GH9 construct results in complete inactivation of the GH9 module. The crystal structure of the Ig-GH9 module pair reveals the existence of an extensive module interface composed of over 40 amino acid residues of both modules and maintained through a large number of hydrophilic and hydrophobic interactions. To investigate the importance of these interactions between the two modules, we compared the secondary and tertiary structures and thermostabilities of the individual Ig-like and GH9 modules and the Ig-GH9 module pair using both circular dichroism (CD) spectroscopy and differential scanning calorimetry (DSC). Thr230, Asp262 and Asp264 of the Ig-like module are located in the module interface of the Ig-GH9 module pair and are suggested to be important in 'communication' between the modules. These residues were mutated to alanyl residues. The structure, stability and catalytic properties of the native Ig-GH9 and its D264A and T230A/D262A mutants were compared. The results indicate that despite being able to fold relatively independently, the Ig-like and GH9 modules interact and these interactions affect the final fold and stability of each module. Mutations of one or two amino acid residues lead to destabilization and change of the mechanism of thermal unfolding of the polypeptides. The enzymatic properties of native Ig-GH9, D264A and T230A/D262A mutants are similar. The results indicate that inactivation of the GH9 module occurs as a result of multiple structural disturbances finally affecting the topology of the catalytic center.     

Note: a high transmission Faraday optical isolator in the 9.2 μm range

We have fabricated and characterized an n-doped InSb Faraday isolator in the mid-IR range (9.2 μm). A high isolation ratio (31(2) dB) and low insertion loss (1.9(3) dB) are obtained. Temperature dependance is analyzed. Further possible improvements are discussed, including the realization of a two-stage isolator. A similar design can be used to cover a wide wavelength range (λ ~ 7.5-30 μm).