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In this paper, a reconfigurable graphene transmission array is proposed for the generation of vortex radio waves at THz. By perforating the substrate with holes of various diameters, different values of effective permittivity are obtained. The transmission coefficient can be adjusted by changing the chemical potential of graphene. With the excitation of planar wave, the phase-compensation of corresponding...
A very compact ultra-wideband (UWB) multiple-input-multiple-output (MIMO) ground linearly tapered slot Antenna (LTSA) is presented in this paper. On a cost-effective FR4 substrate, it consists of a ground plane and two microstrip feed lines. Its overall dimension is only 22×26 mm2. To miniaturize, two linearly tapered slots on the ground plane, acts as the main radiator. Then it does not need extra...
Terahertz grapheme surface plasmon polaritons (GSPPs) radiation source excited by electron beam has been presented. Here we show the theoretical analysis and initial experimental results on this kind of terahertz source. The theoretical calculations of greatly enhancement due to GSPPs and wide tunability indicate that this mechanism has huge potential. THz TDS is utilized to obtain conductance of...
We demonstrated InGaN/GaN multiple quantum well (MQW) solar cells with vertical structure using aluminum (Al) reflectors in this study. The Al reflectors at the bottom of the solar cells can reflect large amount of photons back into the absorber layer, which greatly enhanced the photovoltaic properties of the MQW solar cells. These solar cell devices exhibit excellent performances, including an open-circuit...
In order to reduce the cost of solder materials and retard the thermal shock of temperature-sensitive electronic components during packaging process, SnBi solder paste was explored to replace SnAgCu solder paste due to the low melting temperature. In this study, BGA structure Cu/solder-ball/solder-paste/Cu joints were designed and prepared to study the interfacial reactions and microstructural evolution...
The dynamic wetting behavior and formation of solder ball spattering of Sn-58Bi solder paste on Cu substrate during reflow soldering process were studied by the soldering interrupt test method; meanwhile, the formation mechanism of solder ball spattering was analyzed. Further, the effect of reflow process parameters on the severity of solder ball spattering defect during reflow soldering process was...
With increasingly serious energy and environmental problems, development of new energy saving products is critical to the modern society. Vacuum glass has excellent thermal insulation properties and attracted wide spread attention. The preparation of vacuum glass involves vacuum technology, materials science, machinery, automation technology and other fileds. The key technology of vacuum glass is...
Size effect of solder balls on the interfacial reaction and microstructural evolution of BGA structure Cu/Sn3.0Ag0.5Cu-ball/Sn3.0Ag0.5Cu-paste/Cu joints during isothermal aging at 125 °C was systematically investigated. Results show that a large amount of bulk Cu6Sn5 phase distributes in the solder matrix of joints with large solder ball size, resulting from larger outflux Cu atoms from the interface...
In order to adapt the harsh service condition of the interconnects between the power semiconductors (chips) and substrates, there is an urgent need to develop alternative interconnect materials. Hybrid silver pastes consisting of microscale Ag flakes, nanoscale or sub-microscale Ag particles and volatile solvents have been considered as one of the most promising candidates. In this study, a hybrid...
A beam-steering array operating in the 28-GHz band is described, including a 1-by-4 patch antenna array, liquid crystal (LC) based microstrip meander line phase shifters and feeding networks. The RF signal is coupled to the patch antenna array from the slots in the ground plane. The LC phase shifters are implemented in a kind of inverted microstrip line (IMSL) topology by filling liquid crystal between...
The solder joint's volume and interfacial reaction during the soldering significantly affect its solidification behavior and microstructure feature; further, the microstructure of the solder matrix and the intermetallic compounds (IMC) have a direct impact on the performance and reliability of the solder joint. In this study, the effects of the solder volume and interfacial reaction on the undercooling...
The solder joint's volume and interfacial reaction during the soldering significantly affect its solidification behavior and microstructure feature; further, the microstructure of the solder matrix and the intermetallic compounds (IMC) have a direct impact on the performance and reliability of the solder joint. In this study, the effects of the solder volume and interfacial reaction on the undercooling...
Future broadband mobile communication networks such as 5G and beyond will most likely use millimeter-wave frequencies. There is, however, little knowledge about millimeter-wave antenna design for cellular mobile devices. This paper reports a microstrip grid array antenna on an FR4 substrate in a standard PCB technology. It is shown that the microstrip grid array antenna covers a footprint of 15×15...
The effect of the activators and surfactants in halogen-free fluxes on the wettability of Sn-0.7Cu-0.05Ni solder on Cu substrate (or under bump metallization, UBM) was investigated in this study. The spreading area of Sn-0.7Cu-0.05Ni solder on Cu substrate was used to estimate the wetting performance of the solder influenced by the activators with different amounts added in halogen-free fluxes. The...
During soldering process employing Sn-based lead-free solders, an intermetallic compound (IMC) layer forms between the molten solder and pad/under bump metallization (UBM), whose morphology and thickness play an important role in controlling the service performance of the solder joints, in particular for solder interconnects with the decreasing size where the interfacial IMC layer takes up a high...
This paper presents a high-gain grid array antenna (GAA) on FERRO A6M low temperature co-fired ceramic (LTCC) for 60-GHz antenna-in-package (AiP) applications. The high-gain GAA includes four sub-antennas. Dimensions of the sub-antenna are 15 × 15 × 1 mm3, which is composed of four subarrays. Measured results show that the sub-antenna features impedance bandwidth (BW) 50 – 65.6 GHz, 3-dB gain BW 58...
The morphological evolution of Cu6Sn5 grains formed at the interfaces of “Sn-3.0Ag-0.5Cu/Poly-crystal Cu (PC-Cu)” and “Sn-3.0Ag-0.5Cu/Single crystal Cu (SC-Cu)” under different reflow conditions was investigated. Reflow experiments were performed at different peak temperatures of 230, 260 and 290°C corresponding to the dwelling time of 20s, 60s and 600s, respectively. The results show that Cu6Sn5...
The solidification behavior of Sn-3.0Ag-0.5Cu solders and Sn-3.0Ag-0.5Cu/Cu joints was investigated by using differential scanning calorimetry (DSC) incorporated into the reflow process. The critical factors influencing the undercooling behavior of the solders and joints, such as the solder size, composition and substrate size, were examined. The results show that the type of the primary solidification...
Recent advances in design of transmit/receive (T/R) switches in complementary metal oxide semiconductor (CMOS) technology for radio transceivers are reviewed in this paper. First, the evolution of wireless communication systems and CMOS technology are introduced for the purpose of design of T/R switches. Then, typical T/R switch topologies, key performance parameters, and device circuit models are...
CuInSe2 (CIS) thin films were prepared by ion-beam sputtering at different substrate temperatures. The films prepared at room temperature were annealed at different temperatures. Films annealed at appropriate temperatures are dense, uniform and of single-phase.
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