Metal Cap Research Articles

Tailoring the performance of ceramic-metal piezocomposite actuators, ‘cymbals’

A unique design of metal-ceramic actuators exhibits very high displacement and large generative forces. This new metal-ceramic composite actuator design, the ‘cymbal’, consists of a piezoelectric disk sandwiched between two truncated conical metal endcaps. The radial motion of the piezoelectric ceramic is converted into flextensional and rotational motions in the metal endcap. Based on previous studies of ceramic-metal composites, a simplified model has been developed to evaluate the properties of cymbals and to aid in materials selection. The influence of the stiffness of the metal, the piezoelectric coefficients of the ceramics and the characteristics of the epoxy bond on actuator performance have been evaluated. It is found that the higher the transverse piezoelectric coefficient, the higher the displacement of the actuator. The stiffness of the metal reduces the displacement but allows the composite to support higher loads. There is a thermally induced displacement of the piezocomposite with the temperature that is related to the thermal expansion mismatch between the metal endcaps and the ceramic. By selecting appropriate materials, it is possible to avoid this thermally induced displacement. Very low or negligible temperature dependence of the displacement is attained by using PZT ceramics with temperature-independent properties together with metal caps having higher Young's modulus and lower thermal expansion coefficients than the ceramics.

Compact radiating element

A new, compact, low profile radiating element is described which has a number of interesting and useful characteristics that are not easily obtained from microstrip patches or other low profile radiators. The element, which is shaped like a small square metal cap, has a very compact footprint and a height of the order of one-eighth of a wavelength. Both circularly polarised and linearly polarised variants have been investigated, and a bandwidth in excess of 17% has been demonstrated.

Photolithographic patterning of vacuum-deposited organic light emitting devices

We demonstrate a photolithographic technique to fabricate vacuum-deposited organic light emitting devices. Photoresist liftoff combined with vertical deposition of the emissive organic materials and the metal cathode, followed by oblique deposition of a metal cap, avoids the use of high processing temperatures and the exposure of the organic materials to chemical degradation. The unpackaged devices show no sign of deterioration in room ambient when compared with conventional devices fabricated using low-resolution, shadow mask patterning. Furthermore, the devices are resistant to rapid degradation when operated in air for extended periods. This work illustrates a potential foundation for the volume production of very high-resolution, full color, flat panel displays based on small molecular weight organic light emitting devices.

THE LINGUAL BARBELL: A NEW ETIOLOGY FOR THE CRACKED-TOOTH SYNDROME

( attooing and body piercing are companion customs that have been observed across cultures over many centuries. Historically, both practices have satisfied people's need to participate in proscribed cultural, spiritual, sexual and decorative practices. Body piercing is currently experiencing increasing popularity in the United States as a form of personal esthetic expression. According to Armstrong, part of the motivation or preference for body piercing over tattooing is the perceived lack of permanence of the former activity.' Common body-piercing sites include the ears, lip, eyebrow and nose. Additional sites involve the navel, nipples and genitals. Of particular interest to the dentist is tongue piercing. Three recent reports in the dental literature describe this intraoral practice and conclude with the caution that as tongue piercing increases, dentists may see damage to the teeth.2'4 Boardman and Smith questioned patients who had undergone tongue piercing about oral complications; they identified chipped teeth, trauma to the lingual anterior gingiva, increased salivary flow and infection as the most commonly occurring sequelae of the procedure.' Prior to these reports, the greatest concerns had been infection and edema of the tongue, both of potentially serious consequence.6'7 The technique is fairly straightforward and accomplished without anesthetic. The tongue is generally pierced in the midline anterior to the lingual frenum. The piercing is accomplished with a large-bore needle followed immediately by insertion ofthe barbell stem. An oversized (long) stem is placed initially to accommodate the lingual swelling that accompanies the procedure. After the swelling subsides, a shorter stem is inserted so that the metal balls or caps of the barbell rest close to the dorsal and ventral surfaces of the tongue.

Microanalysis of plastic strain

A technique for quantifying surface shear strains associated with plastic contact damage has been developed. A complete stereographic mapping of rotational transformations is determined using transmission electron microscopy from trace analysis of contours or convergent beam electron diffraction. A high resolution, quantitative surface mapping technique such as atomic force microscopy is then used to determine local declination. These measurements produce 5 of the 6 necessary relationships to determine completely the first order shear displacements; the sixth relationship must be determined using symmetry and continuity requirements. These techniques are applied to a model system, microindentation of AlN. Surface deformation associated with these indentations consists of a simple (engineering) shear, γ = 0.38, operating about axes coincident with the outer indentation edges and forming an inert layer or ‘dead metal cap’ immediately beneath the indenter tip.

Ultrasound barrier microsystem for object detection based on micromachined transducer elements

This work reports on the fabrication, characterization, and encapsulation of micromachined membrane resonators for ultrasound generation and detection. Based on the encapsulated 1/spl times/1-mm membrane resonators, an ultrasound barrier microsystem for short-distance object detection including the necessary driving circuitry has been developed. Using the ultrasound principle, the barrier microsystem is able to detect, e.g., optically transparent objects. The membrane resonators are fabricated using an industrial silicon technology compatible with bipolar integrated circuit (IC) technology in combination with a postprocessing etching step. Because of the compatibility with IC fabrication technology, the membranes feature electrothermal excitation and piezoresistive detection of transverse vibrations. For the generation of ultrasound, membranes, which exhibit a slight initial buckling due to fabrication-induced compressive stresses, are best suited. At the fundamental resonance frequency f=87 kHz, maximum sound-pressure amplitudes up to 0.25 Pa can be achieved at 50-mm distance. With the piezoresistors arranged in a Wheatstone bridge, a sensitivity for the detection of sound at the resonance S/sub sound/=2 /spl mu/V/mPa (for an applied bias voltage of 5 V) is obtained. To protect the membranes from the environment, they are covered by a metal cap with a periodic grid of holes and a thin, porous membrane. With this encapsulation approach, the generated sound pressure in forward direction is only slightly lowered, while the total beam angle (/spl ap/80/spl deg/) of the generated sound field is distinctly reduced.

Capped ceramic underwater sound projector

The cymbal-type transducer developed at the Materials Research Laboratory at Penn State Univ., which is similar to the ring/shell flextensional transducer, is currently being investigated as a shallow-water (<250 m) sound projector for the 10–75 kHz frequency range. The standard size cymbal transducer is 12.7 mm in diameter and approximately 2 mm in total thickness. It consists of a poled lead zirconate-titanate (PZT) disk capped symmetrically on each face by identical thin metal caps. Each cap is shaped with a cavity on its inner surface so that an air space exists between the PZT disk and the top of the cap. The size of the air space, the thickness of the cap, and the type of cap material all influence the operating performance and allowable operating depth of the device. Parameters necessary to characterize an underwater projector such as resonance frequency, mechanical Q, electroacoustic efficiency, transmit voltage response (TVR), and source level will be presented. Experimental data will be compared with values calculated from the Ansys■ finite-element program. Results from single elements as well as cymbal arrays (both potted and unpotted) will be shown. [This work was funded by the Office of Naval Research Contract No. N00014-96-1-1173.]

Lateral electron equilibrium and electron contamination in measurements of head-scatter factors using miniphantoms and brass caps.

The head-scatter factor (Sh) can be measured with a narrow miniphantom or a metal cap provided it is completely covered by the photon beam and its lateral size is thick enough to prevent electron contamination contributions. The effects of lateral electron equilibrium (LEE) and electron contamination on the Sh values were studied. The EGS4 Monte Carlo technique was used to calculate the minimum beam radii (rLEE) required to achieve complete LEE for photon beams ranging from 60Co to 24 MV. The measurement shows that the error introduced to the Sh value due to lateral electron disequilibrium is negligible. The radii of the miniphantoms or the sidewall thicknesses of the caps can be reduced below rLEE provided they are thick enough to prevent the effect of electron contamination.

Metal-electroactive ceramic composite actuators

First Page

Lead inductance of tape carrier package for high-speed LSI's

Lead inductances of a 432-lead TCP (Tape Carrier Package) with a metal cap are evaluated by treating the leads as multiconductor-coupled lines. A useful inductance evaluating method is obtained by using a quasi-TEM electromagnetic field analysis and matrix operations. This method is demonstrated for the TCP. By a proximity effect of grounded conductors, the effective self inductance of the longest lead can be reduced to 7.3 nH. This result indicates that TCP's can be applied to high-speed LSI's of clock rates up to 100 MHz. >

Nuclear Reaction Probe of Oxygen Vacancy Migration in Electrically Fatigued PZT Thin Film Capacitors

ABSTRACTThe migration of oxygen vacancies and their entrapment near film-electrode interfaces has been proposed as a cause of fatigue (i.e., polarization weakening) in ferroelectric thin film capacitors. To test this idea, lead zirconate titanate (PZT) thin films were epitaxially deposited by laser ablation on LaAlO3 substrates with yttrium barium cuprate (YBCO) base electrodes. Thin film capacitors were formed by deposition of noble metal (Pt) cap electrodes; half of them were then electrically fatigued by repeated polarization reversals (108 cycles). The distributions of oxygen in the two halves were then compared by means of accelerator-based nuclear backscattering (using the narrow elastic resonance at 3.045 MeV in the scattering of 4He from 16O) throughout the bulk of the PZT films and especially right under the Pt electrodes. We were unable to detect any difference in the oxygen profiles to within the accuracy of measurement, which was about 1 % of the oxygen concentration. Compositional changes, at least involving oxygen, do not seem to be responsible for the striking electrical alterations seen in fatigued PZT.

UV curable urethane encapsulant for ceramic chip carriers

A new acrylated methane encapsulant has been formulated for use on ceramic chip carriers. This encapsulant has been implemented on pin grid array (PGA) ceramic carriers and on peripheral leaded surface mount (SMT) ceramic carriers for IBM's C4 chips. The encapsulant is a UV curable material and is used to cover the thin-film circuitry on the ceramic carrier. The encapsulant offers a low-cost alternative to the metal caps that were used on the pin grid array ceramic carriers or to the ceramic cap that was used on the peripheral leaded surface mount carrier. UV curing was chosen as the preferred curing process in order to improve the manufacturing process flow. The packages used with this encapsulant all employ IBM's C4 chips. The C4 joints to the ceramic carrier are strengthened with a silica-filled epoxy encapsulant. The new UV curable urethane encapsulant is used to protect the remaining exposed circuitry from mechanical and environmental damage. The urethane encapsulant covers everything from the chip edge to the outer edge of the package. The backside of the chip is intentionally left uncovered. When thermal enhancement is needed the heatsink is bonded directly to the chip. Significant improvement in internal thermal resistance is realized with this design.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Maturational Changes in Dermal Absorption of 2,3,7,8-Tetrachlorodibenzo- p-dioxin (TCDD) in Fischer 344 Rats

An earlier study indicated that percutaneous absorption of a 40-nmol dose of TCDD decreased with aging in rats, suggesting that the potential for systemic exposure following dermal contact would be decreased in older age groups. In this study, maturational changes in potential for systemic exposure to TCDD following dermal application of a low dose (200 pmol) of this chemical were examined in male Fischer 344 rats. Absorption, tissue distribution, and elimination of TCDD, measured as TCDD-derived radioactivity, were examined 72 hr after dermal application of 200 pmol [ 3H]TCDD (111 pmol/cm 2 applied over 1.8 cm 2) to the interscapular region of 3-, 5-, 8-, 10-, and 36-week-old rats. The dose was applied in 60 μl acetone and the application site was covered with a perforated metal cap; animals were held in individual metabolism cages. Dermal absorption was greatest in 3-week-old rats (∼129 pmol; ∼64% of the administered dose), decreasing to approximately 80 pmol (∼40%) in 5-, 8-, and 10-week-old rats and to 45 pmol (∼22%) in 36-week-old rats. In each age group, 70 to 80% of the radioactivity remaining at the application site 72 hr after dosing could be removed with acetone swabs. Major tissue depots of radioactivity were liver and fat; skin and muscle were minor depots. Changes in distribution of absorbed TCDD-derived radioactivity reflected changes in body mass of these depots; however, tissue concentration also varied. Whole body dissection was performed on rats to determine body mass of tissue depots. Adipose tissue content ( Y) increased linearly with body weight ( X), Y = 0.03 X + 2.1 ( r 2 0.95). Elimination of absorbed TCDD-derived radioactivity was incomplete in all age groups with larger residues being recovered in the carcass. Results indicate that TCDD is absorbed to a greater degree through skin of very young animals and that a significant decrease in potential for systemic exposure may occur during maturation and again during aging.

Mid-infrared pulsed laser ablation of the arterial wall

Pulsed mid-infrared lasers are an alternative to excimer lasers for transluminal angioplasty. The mid-infrared lasers, however, were reported to produce "acoustic" wall damage that might impair the immediate and long-term results. To study the immediate and long-term effects on the arterial wall, 184 craters (1 mm diameter and 1 mm depth) were produced perpendicular to the intimal lining in the thoracic aortas of pigs. Three types of craters were evaluated: Ho-YSGG laser-induced (lambda = 2.09 microns, 2 pulses of 500 microseconds, 0.50 joule/pulse, 50 gm force), mechanically drilled, and "acoustic" craters. "Acoustic" craters were produced by two laser pulses delivered into a saline-filled metal fiber cap, which was placed in a mechanically drilled crater. The metal cap was provided with four outlets for water vapor and isolated "acoustic" from optical and thermal laser effects. The pigs survived 3, 14, and 28 days. Arterial wall damage, medial necrosis, and wall healing were assessed microscopically. At 3 days, laser and "acoustic" craters were accompanied by large tissue ruptures (2.7 +/- 0.9 mm and 2.9 +/- 0.8 mm, respectively, mean +/- standard deviation). These were attributed to large vapor bubbles expanding within the tissue. A zone of medial necrosis was observed adjacent to the laser craters (0.43 +/- 0.15 mm) and to the "acoustic" craters (0.17 +/- 0.14 mm). Neither ruptures nor necrosis was observed with the mechanical craters. At 2 and 4 weeks, the necrotic areas were repopulated with smooth muscle cells and all craters were adequately filled with smooth muscle cells, without any sign of an exaggerated proliferative response. We conclude that within the arterial wall, Ho-YSGG ablation was accompanied by the rapid expansion of a water vapor bubble. The formation of the relatively large vapor bubble is inherent to the use of a mid-infrared laser. The risk of creating dissections clinically, when delivering Ho-YSGG laser pulses, remains to be determined. The present study provided no indication that the arterial wall fissures might affect the restenosis rate unfavorably by promoting myointimal proliferation.

Enforced Intermaxillary Fixation (IMF) as a Treatment of Obesity.

Intermaxillary fixation (IMF) using metal cap splints and various linkages was tried in a group of 11 patients who had requested restriction of solid diet as a treatment for their obesity (Quetelet's index > 25-35). Compliance with treatment protocols was successfully addressed by means of support from physicians, dietitians, clinical psychologists and by peer groups. Non-compliance was defined and agreed. The full cap splints for each dental arch, linked and enforced by special rigid locking devices, proved to be a reliable technique of IMF for periods of up to 3 months. Thereafter, the majority of the patients attempted interference with the IMF linkage or detached the splints. Eight patients gained weight after removal of the IMF. Two patients were successful in weight stabilization after 2-14 kg weight loss during IMF. It is probable that psychological and personal factors contributed to their success. It was concluded that by Itself, rigidly enforced IMF for 3 months or longer was an unsuitable treatment mode for the majority of obese patients but could be used as a preparation for other forms of bariatric surgery.

Metal–Ceramic Composite Actuators

A new type of actuator composed of metal (brass) end caps and piezoelectric ceramics has been developed as a displacement transducer. Shallow cavities positioned between the metal caps and the central ceramic disk convert and amplify the radial displacement of the piezoelectric ceramic into a large axial motion of the metal end caps. Large d33 coefficients exceeding 2500 pC/N are obtained with the composite actuators. The behavior of the electrically induced strain with geometric variables, such as the thickness of the metal end caps, and with pressing force and driving frequency has been evaluated. Sizeable strains are obtained with both PZT (piezoelectric lead zirconate titanate) and PMN (electrostrictive lead magnesium niobate) ceramics.

Conversion of the Electrohydraulic Electrode to an Electromechanical Stone Impactor: Basic Studies and a Case Report

A 3.3F electrohydraulic electrode (Wolf 2137.23) has been confined within a spring with a metal end cap, irrigated with water and covered with a 0.003-inch metal sheath (outside diameter 5F). The electrohydraulic lithotripsy discharge (Wolf Generator 2137.50) at El causes the metal cap to extend 3mm. at 1,500cm. per second and creates an impact pressure of 600 to 800 bar. Stone fragmentation efficiency of the electromechanical impactor was equivalent to unshielded electrohydraulic lithotripsy (gallstone 2.83mg. per pulse, struvite/apatite 1.41mg. per pulse, cystine 0.41mg. per pulse, uric acid 1.48mg. per pulse and 100% calcium oxalate monohydrate 0.10mg. per pulse).Studies of the discharge of the electromechanical impactor within the pig ureter showed that minimal ureteral submucosal edema and hemorrhage occurred at 300 shocks discharged at a single point, and disruption of the mucosa and partial injury to the muscle layer occurred after 600 shocks given at the site of a pinched pig ureter. Pushing the electromechanical impactor perpendicular to the wall of the pig bladder will create a mechanical perforation within 35 shocks (electrohydraulic lithotripsy within 2 shocks).One patient had excellent fragmentation of a lower ureteral mixed monohydrate and dihydrate stone under direct vision performed with the electromechanical impactor passed via a 9.5F uretero-scope. There was no evidence of mucosal injury with 500 shocks.The electromechanical impactor has been developed to provide a safe and inexpensive method of ureteral stone fragmentation or disimpaction. These studies were performed to establish limits of safety that may allow use of the electromechanical impactor for stone fragmentation in the ureter without the need for ureteroscopy.

Thermal Effects and Histologic Changes from Nd:YAG Laser Irradiation on Normal and Diseased Aortic Tissue Using a Novel Angioplasty Catheter with a Mobile Optical Fiber: An in Vitro Assessment

Although various laser angioplasty devices are currently being examined, thermal damage and perforation of the vessel wall remains the major acute complication of vascular laser recanalization. Consequently, the aim of this study was to investigate the thermal effects and histologic changes from laser irradiation (Nd:YAG, 1064 nm) on normal and diseased aortic tissue using a novel angioplasty device. During laser emission the coaxially guided optical fiber tip was positioned in reference to the end hole of the metallic capped probe as follows: (1) at the end hole (metal-cap position), (2) protruding 10 mm from that end hole (bare-fiber position), (3) withdrawn 5 mm into the metal cap's lumen (hot-tip position). In total, 96 laser impacts (25 joule: 5 W, 5 s, each) were produced on normal and atherosclerotic aorta in air through a 0.2-mm-core-diameter silica quartz fiber, with direct contact on the intimal surface of the target tissue by both the fiber and the metal cap and by either the fiber or the metal cap (n = 32 each). Tissue temperature was measured by means of special sensors positioned opposite the irradiated intimal spot in direct contact with the adventitial surface. Morphohistologic evaluation of lesions was performed and injury indexes were determined.

Stress analysis of a metal cap with sapphire windows for hybrid ICs

AbstractTo hermetically seal a hybrid IC with several EPROM IC ships, sapphire windows are brazed to a metal cap. Since it was necessary to investigate the pressure resistance of the sapphire windows, stress analysis was performed using the finite element method. In stress analysis, we consider the thermal stress generated in brazing the sapphire window on the metal cap, the forced stress generated in the hermetic seal process of the hybrid IC and the pressured stress generated in the hybrid IC. The allowable stress in sapphire was measured by the bending test with two‐point support to obtain the stress limit of sapphire. The theoretical and experimental results were compared to confirm the validity of the analytical model.The analytical method developed in this study will be helpful to achieve high reliability in a hybrid IC with sapphire windows.

High K-value LDD GaAs MESFET's with SiF/sub 3/-implanted shallow channels

High K-value self-aligned GaAs MESFETs with a reduced short-channel effect that were developed using both shallow SiF/sub 3/-implanted channels annealed with a WSiN refractory metal cap and a lightly doped drain (LDD) structure are discussed. The 0.5- mu m-gate device has a maximum transconductance of 360 mS/mm and a K-value of 504 mS/Vmm with a threshold voltage of 60 mV. The threshold voltage shift was only 90 mV when the gate length was reduced from 2.0 to 0.5 mu m. In addition, more precise control of the threshold voltage was obtained.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>