Development of an atomic force microscope (AFM) probe for local electrical conductivity measurement is reviewed. Electrical conductivity of a 99.999% aluminum wire having a 400nm width and a 350nm thickness was measured by the four-point (4P) AFM probe. This technique is a combination of the principles of the four-point-probe method and standard AFM. The instrument is capable of simultaneously measuring both surface topography and local conductivity. The repeatability of conductivity measurements indicates that this 4P-AFM probe could be used for fast in situ characterization of local electrical properties of nanocircuits and nanodevices.
In this study, we observed anomalous softening in elasticity of Co/Pt superlattice thin films by measuring the out-of-plane elastic constant using the picosecond laser ultrasounds. It showed correlation with the strain energy of Co and Pt layers; as the strain energy increased, the elastic constant was lowered. In Co/Pt superlattice, the strain of each layer becomes more than 0.01 because of 10.7% lattice misfit at the interfaces, which will be partially released by occurrence of noncohesive-bonding regions. We consider that as the strain energy increases, the volume fraction of the noncohesive-bonding region increases, and the elastic constant is lowered. This view is supported by the micromechanics calculation.
The mechanical properties of copper thin films formed by electroplating were compared with cold-rolled copper films using tensile test and nano-indentation. Both the Young's modulus and tensile strength of the films were found to vary drastically depending on the microstructure of the films. Though the Young's modulus of the cold-rolled film was almost same as that of bulk material, that of the electroplated thin film was about a fourth of that of bulk material. The microstructure of the electroplated film was polycrystalline and a columnar structure with a diameter of a few hundreds-micron and the strength of the grain boundaries of the columnar grains seemed to be rather week. The superplastic deformation was observed in the film due to the cooperative grain boundary sliding. In addition, there was a sharp indentation depth dependence of Young's modulus of the film. There was also a plane distribution of Young's modulus near the surface of the film depending on the distribution of the diameter of the columnar grains.
Au alloys have great potentialities as solder joints of electronic packaging. However, studies on mechanical properties of Au solders, especially on creep properties, are very limited. Mechanical properties of Au-20Sn and Au-12Ge were measured by indentation tests ranging between nano and macro scales. First, macro indentation creep tests were carried out at various temperatures, i.e. 295K, 323K, 373K, 398K and 423K. It was found that the indentation creep deformation was observed at room temperature for Au-20Sn, while above 373K for Au-12Ge. Second, the indentation creep properties were measured for ζ and δ phases of Au-20Sn using a nano-indentation testing machine in order to investigate the influences of microstructure on the creep properties. Finally, we evaluated anisotropy of textured microstructure of Au-12Ge, where the dent shapes were distorted. This behavior was attributed to the three dimensional configurations, namely pile-up and sink-in. Based on the results of nano-indentation tests, numerical model for the microstructure of Au-12Ge was established and the mechanisms of the pile-up and sink-in were discussed.
Brittle strength of single crystal silicon is greatly affected by surface etching damage. ICP-etching induced notching is well-known to be most dominant damage in MEMS process. Many experimental approaches toward notching-free process have been carried out. In this study, we have proposed the bending test for evaluating the effect of notching damage on the brittle strength. The test was applied to five kinds of specimens involving identical geometry and different etching damage. Etching damage was quantified by the surface roughness which was measured by laser microscope. It was found that linear relationship between brittle strength and notching roughness can be seen and the strength increases about 200MPa as the roughness decreases 0.1μm.
In order to secure the certain operation of MEMS devices, it is very important to design a hermetically sealed package which protects the device from wet environments, taking into account the reliability of cap bonding of MEMS packages. Anodic bonding is a popular cap bonding method. In this process, glass and single crystal silicon are bonded at high temperature under high voltage conditions. In this study, the new production method of device size specimen with an interface crack by wafer process is proposed. And an attempt is made to establish a method of testing the cap bonding strength of packages and to make clear the interface strength of anodic bonding between the glass and single crystal silicon.
This paper describes a novel local heat process technique for MEMS soldering technology. Al/Ni multilayer film deposited by DC magnetron sputtering shows self-propagating exothermic reaction. By applying a spark to the reactive film, the film generates heat enough to melt Au-Sn solder film. The heat of reaction depended on Al/Ni bilayer thickness and the total film thickness. We used the Al/Ni multilayer film as a local heat source in MEMS soldering packages. Au-Sn solder film-bonded silicon elements by the local heating was fabricated without other external heat sources, and the bond strength was characterized. The local heating technique by Al/Ni multilayer film's exothermic reaction would likely have the potential for MEMS soldering technology.
In an effort to utilize saccharide-iron oxide nanoparticles in medicine, we synthesized the magnetic particles coated with various types of saccharides using a coprecipitation method. The effects of various coating materials (saccharides) and conditions for their synthesis on the magnetic properties and particle diameter were investigated. All synthesized samples presented superparamagnetic behavior. Magnetic properties of saccharide-iron oxide nanoparticles were mainly dependent on the pH conditions during their synthesis. There was an adequate pH condition at which high magnetic property can be obtained. The size of the colloids could be controlled by a well-chosen temperature during synthesis and concentration of saccharide solution. Moreover, the type of saccharide coating had a significant effect on the size of the colloids and their magnetic properties. Magnetic particles coated with polysaccharides showed higher magnetization than those coated with low-molecular saccharides, and the diameter of colloids coated with polysaccharides was larger than that of those coated with low-molecular saccharides. The ultimate saturation magnetization was 24.0 [A·m2/kg], and the mean diameter of colloids could be controlled in range of 74.5 [nm]–455.1 [nm].
For the evaluation of the mechanical properties of microelements, bending tests of cantilever beams have been widely used because they are easier than tensile tests to fix the specimens to testing machines. For bending tests, it is very important to apply the load to the specified test position, because the indented position affects the load-displacement curves of the cantilever beams. In this paper, bending tests of polysilicon microelements were conducted by using a nanoindentation system with a help of in situ SPM imaging. The in situ SPM images were obtained by the indenter probe before and after bending tests. The bending specimens tested were 3.8μm thick, 5μm wide, and 20 or 35μm long. The difference between the specified test position and the indented position was within 0.2μm, which affected Young's modulus by 3%. The Young's modulus of polysilicon microelements obtained in this study was 140±11GPa, with a help of FEM analysis.
In the present study, the ultra-bright synchrotron radiation X-ray was applied to the observation of small cracks in steels. It is important to investigate the applicability of synchrotron radiation X-ray and several parameters for the observation of defects in steels, which is widely used in industrial structures. The Synchrotron radiation X-ray micro computed tomography (SR–μCT) was applied to the three-dimensional observation of small cracks which were initiated either in fretting or in torsion fatigue test. It was found that phase contrast imaging technique has enabled the reconstruction of clear crack images with small opening displacement of about 1μm or submicron scale. The shapes of surface and inside cracks obtained by SR–μCT were agreed well with those by the scanning electronic microscopy. SR–μCT can also display characteristic inside shape of fretting fatigue cracks those were not perpendicular to the body axis and coalesced each other under surface. Torsion fatigue cracks of 10∼15μm in depth can be also observed in high-strength steel using SR–μCT.
Ti-SiC nano grain composite is produced by sintering process by using mechanical alloyed powder. Then, its high temperature transformation behavior and the microstructure change of non-equilibrium structures are investigated. TiC/Ti5Si3 powders of elements Ti and SiC whose composition is Ti-20mass%SiC are blended for mechanical alloying (MA). The MA powder whose average particle size is 20∼30μm, has an amorphous structure. The MA powder is compacted by cold compact compression machine for fabrication of a compression-test piece. As the results of the compression-test and TEM observations, it found that new phases were forming during the compression test, and the flow stress changed depending on the initial microstructure of a test piece. Especially, the existence of Ti3SiC2 and a SiC phase affected deformation resistance. Such a deformation behavior is attributed to a pseudo-superplasticity in the material, in which the phase transition of metastable microstructure occurs during the deformation.
Epoxy resin is usually used as a encapsulation of IC chips for electronic parts. Epoxy resin is transformed from liquid to solid by the chemical curing reaction, and then residual stresses and warp deformation are generated in the electronic parts. In this report, the warp deformation behavior for laminated beam caused by the chemical curing process of epoxy resin was examined from both sides of the experiment and theory, which are the thermo-viscoelastic numerical analysis based on the linear viscoelasticity theory and the Finite Element Analysis about the laminated beam consisted of epoxy resin and steel. As a result, it was clarified that the result of thermo-viscoelastic numerical analysis about warp deformation accorded with experimental values almost well, and the warp deformation behavior could be predicted by the thermo-viscoelastic numerical analysis with the precision that there was no problem in practical use.
Compressive loading tests using acrylic acid resin and mortar specimens are conducted to research the fracture of materials with a macroscopic discontinuity under the compression loading in this study. The new types of specimen shape that can produce mode II and mode III deformation are used. The fracture takes place after crack is closed, that is, under the condition that the each crack surfaces are contacted. The fracture under mode II deformation occurs with a well-known wing crack for all specimens. In the experiments under mode III deformation using mortar specimens, the fracture surfaces include partly the fracture surface along the initial crack surface. But almost fracture surfaces are made by the fracture pieces related to the splitting. In the mode III experiments with an acrylic acid resin specimens, the fracture near the crack tip has the coarse surface and the fracture along the initial crack surface is found out.
The authors have conducted a fatigue load test due to a fixed point-loading on the reinforced concrete (RC) slabs strengthened with carbon fiber sheets (CFS) on those bottom sides; subsequently, the reinforcement effects by virtue of their residual strengths after the static load tests were evaluated and then the theoretical equation of the load carrying capacity as to the CFS-reinforced RC slabs has been proposed. As the result, the increasing strength ratios of the non-damaged CFS-reinforced RC slab and the CFS-reinforced RC slabs subjected to the stress hysteresises under the running vibration loads of ±20% and ±30% amplitudes were 1.35, 1.24 and 1.09 times in comparison with the static strength of CFS-unreinforced RC slab, respectively. Furthermore, the theoretical equation of punching shear load carrying capacity of the CFS-reinforced RC slab accumulating the CFS-effective increment to that of the ordinary RC slab has been proposed ; consequently the theoretical value agrees well with the experimental one whether the CFS-reinforced RC slab is non-damaged or not.
This paper presents a basic research on a measurement of strain in the bulk of materials by using high energy white X-rays from a synchrotron radiation source of SPring-8. WEL-TEN780E (JIS G3128 SHY685) whose grain size was 13μm was used as a specimen shaped into G type. The specimen was loaded with bending. The white X-ray beam, which has a height of 50μm and width of 300μm, was incident in the specimen with the Bragg angle θ of 5degree. Bending strain at the surface of specimen was measured by a strain gauge. The strain in the loading direction of the specimen was obtained directly from a rate of change of peak energy of transmitted X-rays through the thickness. As a result, the internal strain of SHY685 of 5mm thickness could be evaluated using white X-rays which range of energy from 60keV to 150keV. It is suitable for the measurement with sufficient accuracy to include more than or equal to 5000 grains of crystal in the gauge volume. The measurement error of strain could be decreased by using the diffracted X-rays with high energy. Furthermore, the measurement with a high degree of accuracy was accomplished using α–Fe321 diffraction in this material. The results showed that the high energy white X-ray is effective for internal strain measurements.