A hybrid wafer-dicing process for GaAs MMIC production

A dicing process for GaAs MMIC (monolithic microwave integrated circuit) wafers using spin-on wax for wafer mounting and a hybrid process of wet chemical etching/mechanical sawing for chip dicing is described. This process minimizes ragged chip edges and reduces generation of microcracks in addition to the elimination of the plated gold burrs on the backside of the diced MMIC chips. This process gives a uniformity of -3 μm across a 2-in wafer following the completion of the whole backside process. This GaAs chip dicing technique is amenable to production because it exhibits both a very high chip yield (>90%) and nearly flawless edges     

Reference free part encapsulation: Materials,machines and methods

Reference Free Part Encapsulation (RFPE) is an automatic, universal workholding process developed by researchers at the Massachusetts Institute of Technology and the University of California-Berkeley. The process encapsulates the stock by freezing it in a low melting point material during machining and transfers datums from one setup to another by refilling and restoring the encapsulation to a known shape after each setup. This paper describes the encapsulator materials and machines developed to test and demonstrate RFPE. The encapsulation material must satisfy stringent thermal properties, and a process is described that concludes that the tin–bismuth eutectic is ideal. The similarities of the encapsulation process to manufacturing processes such as die casting and injection molding are considered; however, it is shown that many intrinsic differences exist between the encapsulation process and injection molding or die casting. Two encapsulation machines are presented. The first is a larger encapsulation machine capable of forming encapsulations with a 6 in. by 6 in. footprint. The second, a much smaller portable machine capable of forming encapsulations with a 2 in. by 2 in. footprint, is also presented. Special features of each encapsulation machine are highlighted and various design decisions are discussed.     

Designing the MPC105 PCI bridge/memory controller

The MPC105 peripheral component interconnection bridge/memory controller provides a platform-specification-compliant bridge between Power PC microprocessors and the PCI bus. With it, designers can create systems using peripherals already designed for a variety of standard PC interfaces. This bridge chip also integrates a secondary cache controller and high-performance memory controller that supports DRAM or synchronous DRAM and ROM or flash ROM     

Spatially resolved X-ray diffraction phase mapping and α → β → α transformation kinetics in the heat-affected zone of commercially pure titanium arc welds

Spatially resolved X-ray diffraction (SRXRD) is used to map the α → β → α phase transformation in the heat-affected zone (HAZ) of commercially pure titanium gas tungsten arc welds. In situ SRXRD experiments were conducted using a 180-μm-diameter X-ray beam at the Stanford Synchrotron Radiation Laboratory (SSRL) (Stanford, CA) to probe the phases present in the HAZ of a 1.9 kW weld moving at 1.1 mm/s. Results of sequential linear X-ray diffraction scans made perpendicular to the weld direction were combined to construct a phase transformation map around the liquid weld pool. This map identifies six HAZ microstructural regions between the liquid weld pool and the base metal: (1) α-Ti that is undergoing annealing and recrystallization; (2) completely recrystallized α-Ti; (3) partially transformed α-Ti, where α-Ti and β-Ti coexist; (4) single-phase β-Ti; (5) back-transformed α-Ti; and (6) recrystallized α-Ti plus back-transformed α-Ti. Although the microstructure consisted predominantly of α-Ti, both prior to and after the weld, the crystallographically textured starting material was altered during welding to produce different α-Ti textures within the resulting HAZ. Based on the travel speed of the weld, the α → β transformation was measured to take 1.83 seconds during heating, while the β → α transformation was measured to take 0.91 seconds during cooling. The α → β transformation was characterized to be dominated by long-range diffusional growth on the leading (heating) side of the weld, while the β → α transformation was characterized to be predominantly massive on the trailing (cooling) side of the weld, with a massive growth rate on the order of 100 μm/s.     

Panic and Comorbid Anxiety Symptoms in a National Anxiety Screening Sample: Implications for Clinical Interventions.

Questionnaire data from 2,033 participants in the National Anxiety Disorders Screening Day sample were used to assess the presence of panic and comorbid anxiety problems. These participants were selected from more than 15,000 attendees on the basis of never having received treatment for a psychiatric disorder and meeting screening criteria for panic disorder. With each comorbid anxiety problem (generalized anxiety disorder, posttraumatic stress disorder, social phobia, and obsessive-compulsive disorder), participants had a corresponding increase in interference in daily living as well as readiness to seek treatment. The addition of generalized anxiety or depression with panic symptoms resulted in marked increases in interference scores. Clinical treatment implications for panic disorder are discussed in terms of the effects of comorbid anxiety problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preparation of 2-Aroyl-3-methyl-1H-1,4-benzothiazines. ESR Study of 2-benzoyl-1,3-dimethyl-1H-1,4-benzothiazine

2-Aroyl-3-methyl-1 H-1,4-benzothiazine ylids ( 2a – k ) were prepared by alkylation of the corresponding 4H-benzothiazines 1 . The ylids 2 are labile at room temperature; proper analytical and ¹H-n.m.r. data were obtained for their picrates. E.s.r. studies of u. v. irradiated polycrystalline form of ( 2 ; R¹ = Me, R² = H) gave evidence for a long-lived benzothiazinyl radical with the odd electron residing on nitrogen 6 .     

Immunomodulatory Properties and Osteogenic Activity of Polyetheretherketone Coated with Titanate Nanonetwork Structures

Polyetheretherketone (PEEK) is a potential substitute for conventional metallic biomedical implants owing to its superior mechanical and chemical properties, as well as biocompatibility. However, its inherent bio-inertness and poor osseointegration limit its use in clinical applications. Herein, thin titanium films were deposited on the PEEK substrate by plasma sputtering, and porous nanonetwork structures were incorporated on the PEEK surface by alkali treatment (PEEK-TNS). Changes in the physical and chemical characteristics of the PEEK surface were analyzed to establish the interactions with cell behaviors. The osteoimmunomodulatory properties were evaluated using macrophage cells and osteoblast lineage cells. The functionalized nanostructured surface of PEEK-TNS effectively promoted initial cell adhesion and proliferation, suppressed inflammatory responses, and induced macrophages to anti-inflammatory M2 polarization. Compared with PEEK, PEEK-TNS provided a more beneficial osteoimmune environment, including increased levels of osteogenic, angiogenic, and fibrogenic gene expression, and balanced osteoclast activities. Furthermore, the crosstalk between macrophages and osteoblast cells showed that PEEK-TNS could provide favorable osteoimmunodulatory environment for bone regeneration. PEEK-TNS exhibited high osteogenic activity, as indicated by alkaline phosphatase activity, osteogenic factor production, and the osteogenesis/osteoclastogenesis-related gene expression of osteoblasts. The study establishes that the fabrication of titanate nanonetwork structures on PEEK surfaces could extract an adequate immune response and favorable osteogenesis for functional bone regeneration. Furthermore, it indicates the potential of PEEK-TNS in implant applications.     

Direct patterning of vertically aligned carbon nanotube arrays to 20 μm pitch using focused laser beam micromachining

We present a scalable approach for the fabrication of large-area arrays of carbon nanotube (CNT) structures using focused laser beams in the 0.05–10 W range. We show that CNT films can easily be micromachined into arrays of columns using a wide variety of commercially available pulsed lasers – Excimer, diode-pumped solid-state (DPSS), and CO₂ – operating at wavelengths from 248 nm to 9300 nm. We demonstrate that vertically aligned carbon nanotube (VACNT) arrays with pitches from 20 to 500 μm can be produced with aspect ratios greater than 20:1. Machining speeds up to 425 mm/s were demonstrated and trenches were produced from 10 to 200 μm wide depending on the laser method and beam size. The CO₂ laser had the largest beam diameter of 175 μm and produced the widest columns with the most taper. The remaining lasers, having beam diameters between 10 and 100 μm, produced smaller columns and finer pitch arrays. The VACNT arrays were shown to have high surface quality with no observable residue left behind, demonstrating focused laser micromachining as a readily available soft tooling means for direct manufacturing of VACNT devices. Laser micromachining methods are compared to evaluate the tradeoffs between quality and manufacturing costs.     

Seeded growth of Tl 3AsSe3

A technique for seeded growth of Tl ₃AsSe₃ has been developed. The growth conditions were initially determined from calculations using a simple treatment of the thermal transfer during growth. The origin of optical opacity observed in some as-grown Tl ₃AsSe₃ boules is also discussed.