基于VMM的外部存储接口模块的验证平台搭建

本文首先介绍了VMM层次化验证方法学的基本思想和方法,将其与传统的芯片验证技术进行了对比,并进一步对基于VMM(Verification Methodology Manual For System Verilog)方法学的验证平台结构和各个组成模块进行了详细的介绍。最后以外部存储接口(EMI)模块为例对VMM验证平台的搭建进行了具体说明,并给出了验证结果。     

NFO/PZT复合磁电薄膜生长制备及性能的研究

采用脉冲激光沉积(PLD)法,在制备有SrRuO3底电极的SrTiO3(001)基片上生长高质量的NiFe2O4/Pb(Zr0.52Ti0.48)O3双层复合磁电薄膜.用X-射线衍射(XRD)对复合薄膜的微结构进行详细表征,结果表明,复合薄膜中NiFe2O4、Pb(Zr0.52Ti0.48)O3结晶良好,且具有单一的面外取向,Φ扫描模式显示NiFe2O4、Pb(Zr0.52Ti0.48)O3均延SrTiO3(001)方向外延生长.磁电性能表征结果表明,由于界面应力效应的作用,复合薄膜的铁电性较单层Pb(Zr0.52Ti0.48)O3明显减弱,而铁磁性基本保持NiFe2O4的软磁特性.     

Experimental and numerical analysis of BGA lead-free solder joint reliability under board-level drop impact

Board-level solder joint reliability is very critical for handheld electronic products during drop impact. In this study, board-level drop test and finite element method (FEM) are adopted to investigate failure modes and failure mechanisms of lead-free solder joint under drop impact. In order to make all ball grid array (BGA) packages on the same test board subject to the uniform stress and strain level during drop impact, a test board in round shape is designed to conduct drop tests. During these drop tests, the round printed circuit board assembly (PCBA) is suffered from a specified half-sine acceleration pulse. The dynamic responses of the PCBA under drop impact loading are measured by strain gauges and accelerometers. Locations of the failed solder joints and failure modes are examined by the dye penetration test and cross section test. While in simulation, FEM in ABAQUS software is used to study transient dynamic responses. The peeling stress which is considered as the dominant factor affecting the solder joint reliability is used to identify location of the failed solder joints. Simulation results show very good correlation with experiment measurement in terms of acceleration response and strain histories in actual drop test. Solder joint failure mechanisms are analyzed based on observation of cross section of packages and dye and pry as well. Crack occurred at intermetallic composite (IMC) interface on the package side with some brittle features. The position of maximum peeling stress in finite element analysis (FEA) coincides with the crack position in the cross section of a failed package, which validated our FEA. The analysis approach combining experiment with simulation is helpful to understand and improve solder joint reliability.     

Effects of periphery encapsulation material on the characteristics of micro vacuum dielectric capacitor

The effects of the periphery sealant on the electrical characteristics of vacuum dielectric capacitors (VDCs) are modeled. For the square shape VDCs, their characteristics are predominantly determined by the ratio of capacitor side length versus the width of boundary sealant layer, r. The smaller of the r value, the smaller of the dissipation factor, and the better frequency response of the VDCs are found. To achieve a dissipation factor of less than 10⁻⁵ at 1 GHz, the dimension parameter, r, should be smaller than 0.05 which has been achieved based on the present technology for a capacitor with size larger than 4 mm × 4 mm. The leakage current can also be reduced significantly in the VDCs. We found that the leakage current is mainly governed by the Poole-Frenkel emission of electrons over the periphery region. The present results have demonstrated that the VDC structure is a promising technology option for making high-frequency micro capacitors.     

Epitaxy and Characteristics of Resonant Cavity LEDs at 650 nm

Resonant-cavity light-emitting diodes (RCLED) at 650 nm wavelength were grown by metal organic chemical vapor deposition. In order to improve the interface quality and reduce the device voltage, an AlGaInP material system has been chosen to grow the top DBRs. The emission properties of the RCLED were characterized by measuring PL and EL spectra. The average emission power of the device is 0.5 mW at 20 mA and 2.2 V, and its spectrum full width at half maximum is about 10 nm.     

Light extraction efficiency enhancement of GaN-based light emitting diodes by a ZnO current spreading layer

preading layers are analyzed.     

Impacts of additive uniaxial strain on hole mobility in bulk Si and strained-Si p-MOSFETs

Hole mobility changes under uniaxial and combinational stress in different directions are characterized and analyzed by applying additive mechanical uniaxial stress to bulk Si and SiGe-virtual-substrate-induced strained-Si (s-Si) p-MOSFETs (metal-oxide-semiconductor field-effect transistors) along <110> and <100> channel directions. In bulk Si, a mobility enhancement peak is found under uniaxial compressive strain in the low vertical field. The combination of (100) direction uniaxial tensile strain and substrate-induced biaxial tensile strain provides a higher mobility relative to the (110) direction, opposite to the situation in bulk Si. But the combinational strain experiences a gain loss at high field, which means that uniaxial compressive strain may still be a better choice. The mobility enhancement of SiGe-induced strained p-MOSFETs along the (110) direction under additive uniaxial tension is explained by the competition between biaxial and shear stress.     

A direct digital frequency synthesizer with high-speed current-steering DAC

A high-speed SiGe BiCMOS direct digital frequency synthesizer (DDS) is presented. The design in tegrates a high-speed digital DDS core, a high-speed differential current-steering mode 10-bit D/A converter, a serial/parallel interface, and clock control logic. The DDS design is processed in 0.35 μm SiGe BiCMOS standard process technology and worked at 1 GHz system frequency. The measured results show that the DDS is capable of generating a frequency-agile analog output sine wave up to 400+ MHz.     

Estimation of electron mobility of n-doped 4, 7-diphenyl-1, 10-phenanthroline using space-charge-limited currents

The electron mobilities of 4, 7-diphenyl-1, 10-phenanthroline (BPhen) doped 8-hydroxyquinolinatolithium (Liq) at various thicknesses (50-300 nm) have been estimated by using space-charge-limited current measurements. It is observed that the electron mobility of 33 wt% Liq doped BPhen approaches its true value when the thickness is more than 200 nm. The electron mobility of 33 wt% Liq doped BPhen at 300 nm is found to be ～5.2 × 10~(-3) cm~2/(V·s) (at 0.3 MV/cm) with weak dependence on electric field, which is about one order of magnitude higher than that of pristine BPhen (3.4 × 10~(-4) cm~2/(V·s)) measured by SCLC. For the typical thickness of organic light-emitting devices, the electron mobility of doped BPhen is also investigated.     

交流异步电动机的软起动

由于传统交流异步电动机的起动方法有两次冲击电流,可对负载产生冲击转矩,采用晶闸管技术实现交流异步电动机软起动,介绍了该技术的工作原理.针对重载起动,传统软起动的局限性,提出采用交一交变频起动和晶闸管调压软起动相结合的方法,并通过试验测试该软起动方法能够解决重载起动时的电压波动影响,具有实际应用价值.