Ultra-high-density interconnection technology of three-dimensional packaging

The study of 20-μm-pitch interconnection technology of three-dimensional (3D) packaging focused on reliability, ultrasonic flip–chip bonding and Cu bump bonding is described. The interconnection life under a temperature cycling test (TCT) was at an acceptable level for semiconductor packages. Failure analysis and finite element analysis revealed the effect of material properties. Basic studies on ultrasonic flip–chip bonding and very small Cu bump formation were investigated for low-stress bonding methods. The accuracy of ultrasonic flip–chip bonding was almost the same level as that of thermocompression bonding and the electrical connection was also confirmed. Atomic-level bonding was established at the interface of Au bumps. For Cu bump bonding, a dry process was applied for under bump metallurgy (UBM) removal. Electroless Sn diffusion in Cu was investigated and the results clarified that the intermetallic layer was formed just after plating. Finally, we succeeded in building a stacked chip sample with 20-μm-pitch interconnections.     

Chain Length Distribution of Amylopectin and Physicochemical Properties of Starch in Myanmar Rice Cultivars

Three different types of amylopectin: long chain length of amylopectin (L-type), medium chain length of amylopectin (M-type), and short chain length of amylopectin (S-type) were classified in 16 rice cultivars (3 for L-type, 6 for M-type, and 7 for S-type amylopectin) based on chain length distribution of amylopectin by fluorophore-assisted carbohydrate electrophoresis through capillary electrophoresis. Frequency distribution of amylopectin chain ratio and short chain ratio supported three types of amylopectin. Ta Soke Pwa and Thet Nu Saba Net Pyan had high values of transition temperatures in a range from (70.7, 74.0, and 77.6°C) to (71.4, 75.0, and 78.8°C) in differential scanning calorimeter analysis. Alkali spreading values and starch gelatinization characteristics in 4 M urea solution showed the association between chain length distributions of amylopectin in Myanmar rice cultivars. A simple linear regression in Myanmar rice cultivars was observed for fa, fb1, amylopectin chain ratio, and short chain ratio with alkali spreading values, with R² values of 0.68, 0.84, 0.84, and 0.81, respectively.     

Fabrication of CuZr(Al) bulk metallic glasses by high pressure torsion

In this paper, pure Cu, Zr and Al metal sheets were alternatively stacked and, then, cold roll-bonded. The overall compositions of the stacks were Cu₇₁Zr_29, Cu₆₂Zr_38, Cu₅₃Zr₄₇ and Cu₅₂Zr₃₈Al₁₀. The bonded materials were subsequently sliced into disks and, then, used for high pressure torsion (HPT) process. After HPT process up to maximum equivalent strain of about 1200 at ambient temperature, bulk materials with 10 mm in diameter and 0.30 mm in thickness were obtained. The phase constitution and microstructural evolutions of the HPTed samples with various rotations ranging from 0.5 to 20 were studied by XRD, FESEM and TEM. Thermal properties of the HPTed samples were analyzed by DSC. It was found that CuZr(Al) BMGs could be fabricated with a wide composition range by the HPT process. Tensile tests were used to measure the mechanical properties of the HPT processed samples. The mechanism of the solid-state amorphization during the HPT process was put forward and discussed.     

Digital video recording

Through mutual technology transfer between consumer and professional video recorders, the last 20 years has witnessed a rapid evolution from analog to digital recording. Each new digital videotape recorder (VTR) uses different channel coding. This implies that improving the recording density involves the development of new channel-coding schemes together with evolutionary magnetic tapes and heads. As a result, professional digital VTR's offer the best features for video recording. This paper reviews state-of-the-art magnetic recording devices, signal processing techniques for digital recording. It also describes the specifications for home-use digital recorders for current television systems, and discusses disk recording technology in the future