Capillary Geometry Research Articles

Characterization and Modeling of Fine-Pitch Copper Ball Bonding on a Cu/Low-k Chip

Cu ball bonding faces more challenges than Au ball bonding, for example, excessive deformation of the bond pad and damage of Cu/low-k structures, because of the much greater hardness of Cu free air balls. In this study, dynamic finite-element analysis (FEA) modeling with displacement control was developed to simulate the ball-bonding process. The three-dimensional (3D) FEA simulation results were confirmed by use of stress-measurement data, obtained by use of stress sensors built into the test chip. Stress comparison between two-dimensional (2D) and 3D FEA models showed the 2D plain strain model to be a reasonable and effective model for simulation of the ball-bonding process without loss of accuracy; it also saves computing resources. The 2D FEA model developed was then used in studies of a Cu/low-k chip to find ways of reducing Al bond pad deformation and stresses of low-k structures. The variables studied included Al pad properties, capillary geometry, bond pad design (Al pad thickness, Al pad coated with Ni layer), and the effect of ultrasonic bonding power.

Investigation of hysteresis in high current ion beam guiding through micro-glass capillary: time and dimension dependence

Guiding of high current density (0.1–3 A m−2) argon ion beams through a straight and tapered micro-glass-capillary is studied. It is observed that the ion beam requires a minimum threshold energy to pass through the capillary. The variation of beam current with applied voltage exhibits hysteresis due to the charges accumulated on the inner wall of the capillary. The dependence of hysteresis and beam transmission on the time interval between successive experiments including capillary dimensions and geometry are investigated. The guiding capability of a tapered capillary is demonstrated where beam size reduction without compromising total current is achieved. A particle-in-cell simulation code, developed by solving the Poisson’s equation and the equation of motion simultaneously, shows reasonable agreement with the experimental results.

A phase-field model of two-phase Hele-Shaw flow

AbstractWe propose a continuum model of two-phase flow in a Hele-Shaw cell. The model describes the multiphase three-dimensional flow in the cell gap using gap-averaged quantities such as fluid saturation and Darcy flux. Viscous and capillary coupling between the fluids in the gap leads to a nonlinear fractional flow function. Capillarity and wetting phenomena are modelled within a phase-field framework, designing a heuristic free energy functional that induces phase segregation at equilibrium. We test the model through the simulation of bubbles and viscously unstable displacements (viscous fingering). We analyse the model’s rich behaviour as a function of capillary number, viscosity contrast and cell geometry. Including the effect of wetting films on the two-phase flow dynamics opens the door to exploring, with a simple two-dimensional model, the impact of wetting and flow rate on the performance of microfluidic devices and geological flows through fractures.

Formation of steady compound cone-jet modes and multilayered droplets in a tri-axial capillary flow focusing device

A novel method for forming steady cone-jet modes and multilayered droplets is developed based on capillary flow focusing geometry using tri-axial needles. The needles manufactured by a laser beam welding process can be readily cleaned, assembled and aligned. A tri-axial capillary flow focusing (TCFF) device is assembled in order to focus a combination of different liquids in the core of a high-speed gas stream co-flowing through a small orifice. The effects of main control process parameters on the characteristics of compound cone-jet mode are studied. Under appropriate working conditions, steady cone-jet configurations with three layers of liquids are obtained, resulting in multilayered droplets with outer shell, middle layer and inner core. The process can also produce monodisperse droplets at smaller scales by releasing the outer shell and the middle liquid. The new design of tri-axial needles and TCFF devices enables reliable encapsulation of multiple components in one shell for potential applications in multimodal imaging, drug delivery, material processing and biomedicine.

Taguchi Method for Development of Mass Flow Rate Correlation using Hydrocarbon Refrigerant Mixture in Capillary Tube

The capillary tube is an important control device used in small vapor compression refrigeration systems such as window air-conditioners, household refrigerators and freezers. This paper develops a non-dimensional correlation based on the test results of the adiabatic capillary tube for the mass flow rate through the tube using a hydrocarbon refrigerant mixture of 89.3% propane and 10.7% butane (HCM). The Taguchi method, a statistical experimental design approach, was employed. This approach explores the economic benefit that lies in studies of this nature, where only a small number of experiments are required and yet valid results are obtained. Considering the effects of the capillary tube geometry and the inlet condition of the tube, dimensionless parameters were chosen. The new correlation was also based on the Buckingham Pi theorem. This correlation predicts 86.67% of the present experimental data within a relative deviation of -10% to +10%. The predictions by this correlation were also compared with results in published literature.

A generalized dimensionless local power-law correlation for refrigerant flow through adiabatic capillary tubes and short tube orifices

This paper presents a new method to obtain generalized dimensionless correlation of refrigerant mass flow rates through adiabatic capillary tubes and short tube orifices. The dimensionless Pi groups were derived from the homogeneous equilibrium model, which is available for different refrigerants entering adiabatic capillary tubes or short tube orifices as the subcooled liquid, two-phase mixture, or supercritical fluid. To mitigate the potential over-fitting risk in neural network, a new “local” power-law correlation reformed from the homogeneous equilibrium model was proposed and compared with the conventional “global” power-law correlation and recently developed neural network model. About 2000 sets of experimental mass flow rate data of R12, R22, R134a, R404A, R407C, R410A, R600a and CO2 (R744) in the open literature covering capillary and short tube geometries, subcritical and supercritical inlet conditions were collected for the model development. The comparison between the recommended six-coefficient correlation and experimental data reports 0.80% average and 8.98% standard deviations, which is comparable with the previously developed neural network and much better than the “global” power-law correlation.

Experimental Study on The Effect of Capillary Tube Geometry on The Performance of Vapour Compression Refrigeration System

A domestic refrigerator of 5 ft3 capacity is used to study the effect of coiled diameter and pitch distance of a capillary tube. Five capillary tubes of 2 mm in diameter and 1500 mm length each are used, as same as original capillary tube of the refrigerator. The capillary tubes is formed in five shapes, each one has different coil diameter (D) namely 25, 50, 75, 100 and 125 mm in diameter, in addition three distances between each coil (pitch (P)) is tested, namely 6, 8 and 10 mm. The pressure at inlet and outlet of capillary are measured to calculate the cycle COP, as well as the power consumed by the cycle compressor is measured to calculate the mass flow rate of refrigerant. The work show that the coiled diameter of capillary tube affect the cycle COP strongly, as the capillary coiled diameter (D) increases from 25 to 100 mm the cycle COP increases from 2.8 to 3.7 when the cabinet temperature equals to 8oC. The increases of coiled diameter more than 100 mm shows insignificant effect on the cycle COP. While the pitch space of capillary tube coiled shows minor effect on the cycle COP. Moreover, to the mass flow rate of refrigerant increases with approximately ranges from 1.2−2.7

Visualization experiments on extrudate swell behavior at the microscale

Extrudate swell exerts a significant impact on the shape and dimensional accuracy of extruded products. It is one of the important factors to be considered when designing the extrusion die and controlling the quality of products. The die swell ratio (B) is used to evaluate the degree of extrudate swell. In this article, comparative experiments were performed in order to simulate and observe in a precise fashion the extrudate swell behavior of carboxymethyl cellulose solution at a microscale by means of a visualization device. We chose micro dies capillaries where the inner diameter was in the range of 0.1–0.5 mm. The effects of capillary geometry, entrance velocity, and shear rate (shear stress) on extrudate swell were investigated. The results indicated that shear rate (shear stress) increases and the value of B is enhanced with decreasing capillary diameter under the same capillary entrance velocity. At different entrance velocities, the die swell behavior from 0.3- to 0.5-mm-diameter capillaries was similar to that of conventional ones, and the value of B increased with increasing shear rate. Additionally, the extrudate swell from the 0.2-mm-diameter capillaries revealed a decline, whereas that from the 0.1-mm-diameter capillaries first diminished and then increased concomitantly with rising shear rate. We expect that this was due to wall slip that occurred analytically in our micro channel.

Upgrades to the XRD1 beamline optics and endstation at the LNLS

XRD1 was the first X-ray diffraction beamline to be built at the LNLS and after approximately 12 years of operation it was substantially updated to improve beam stability, increase the reliability of the monochromator movement as well as provide an experimental hutch that would meet the demands of users. The improvements included the construction of an independent concrete slab below the mirror and monochromator to minimize the vibrations originating from the floor. In addition, the installation of new monochromator mechanisms as well as the replacement of the two Si(111) crystals were performed in order to attain higher precision, stability and reproducibility during operation. Moreover, the diffractometer was replaced by a 3-circle heavy duty diffractometer from Newport to collect XRD patterns primarily in capillary geometry. A robotic arm was installed for fast and automated replacement of samples as well as to secure a cryojet or a hot air blower in front of the sample during measurements. In addition, a housing equipped with 24 Mythen detectors was installed at the beamline allowing for extremely fast data acquisition. Another upgrade was the integration of motors and control systems from PXI National Instruments and Galil controllers with Phytron. These systems are crucial for the next upgrade that is underway at the beamline: enabling remote access for users to collect their measurements without the need to travel to the LNLS.

Effect of capillary tube on the performance of a simple vapour compression refrigeration system

It is essential to study the effect of capillary tube geometry on the performance of refrigeration systems. The literature review focuses on the effect that geometrical parameters like capillary tube length, bore diameter, coil pitch, number of twist and twisted angle have on the pressure drop, coefficient of performance (COP) and mass flow rate of the system. These parameters can be further studied using physical models and mathematical modeling concepts. The parameters stated above can be further optimized in order to enhance the performance of the refrigeration system.

Experimental and Modeling Studies of Looping Process for Wire Bonding

Looping is one of the key technologies for modern thermosonic wire bonders, and it has been affected by many interacting factors. In this study, the wire looping process was observed with a high-speed camera, and the evolution of wire profiles during looping and the capillary trace were obtained through experiments. A dynamic finite element (FE) model was developed to learn the details of the looping process, where real capillary geometry dimensions, capillary trace, diameter of bonded ball and the gold wire material were used, and the friction force and air tension force were considered. The simulated profiles were compared with those of the experiment. Using the verified FE model, the effects of material properties, capillary parameters, and capillary traces on the looping process were studied, and the relationships between the final profiles and parameters were discussed.

Bubble in flow field: A new experimental protocol for investigating dynamic adsorption layers by using capillary pressure tensiometry

For many years the model of a dynamic adsorption layer (DAL) is well established as explanation for the behavior of rising bubbles in surfactant solutions. This model explains the velocity profile and the evolution of the shape of a rising bubble based on the hypothesis of the balance between the drag force and the structure of the adsorbed layer governed by Marangoni convection. However, direct measurements of interfacial properties of the bubble during rising are a real challenge. Here we present a new experimental protocol called “bubble in flow field” suitable for direct measurements of dynamic interfacial properties of a bubble surface using the capillary pressure tensiometry under liquid flow conditions. The experimental results for pure water demonstrate the applicability of the technique for measuring the surface tension of bubbles in a liquid flow field. The operational conditions including capillary tip geometry, liquid flow rate, bubble size and distance of the flow outlet to the bubble pole are optimized experimentally to achieve significant flow effects on a fixed bubble, while surface tension measurements are still reliable. The results for surfactant solutions (C12DMPO and CTAB) indicate respective effects depending on the flow conditions around a freshly formed bubble and evidence the formation of a dynamic adsorption layer. The adsorption equilibrium state is reached faster for higher liquid flow rates. However, the effect of the flow field is negligible on pre-aged bubble surfaces, i.e. no net desorption effects caused by the liquid flow are observed.

Controlled formation of double-emulsion drops in sudden expansion channels

Double-emulsion drops or drops-in-drop have provided useful templates for production of microcapsules due to their core–shell geometry. Here, we introduce new capillary microfluidic geometry for the creation of double-emulsion drops, which is composed of a narrowing channel followed by sudden expansion channel. Drops injected through the narrowing channel are highly accelerated to flow, inducing high inertia force. When rear interface of the drops arrives at the sudden expansion channel, the high inertia force deforms the interface and leads to its breakup into a drop in the interior of the injected drop. This insertion is driven by inertia force against capillary force: High linear velocity and low interfacial tension facilitate the insertion. We also apply this emulsification method to double-emulsion drops with single innermost drop; insertion of a water drop creates the double-emulsion drops with two distinct innermost drops. The resultant double-emulsion drops with single- or double-innermost drops provide useful templates to produce polymersomes which encapsulate same fluid to the continuous phase; this will be potentially useful for sampling of the continuous phase and its isolation in a wide range of applications for micro-total analysis system (μ-TAS).

Rise in optimized capillary channels

AbstractMany technological applications rely on the phenomenon of wicking flow induced by capillarity. However, despite a continuing interest in the subject, the influence of the capillary geometry on the wicking dynamics remains underexploited. In numerous applications, the ability to promote wicking in a capillary is a key issue. In this article, a model describing the capillary rise of a liquid in a capillary of varying circular cross-section is presented. The wicking dynamics is described by an ordinary differential equation with a term dependent upon the shape of the capillary channel. Using optimal control theory, we were able to design optimized capillaries which promote faster wicking than uniform cylinders. Numerical simulations show that the height of the rising liquid was up to 50 % greater with the optimized shapes than with a uniform cylinder of optimal radius. Experiments on specially designed capillaries with silicone oil show a good agreement with the theory. The methods presented can be useful in the design and optimization of systems employing capillary-driven transport including micro-heat pipes or oil extracting devices.

X-Ray and Optical Videography for 3D Measurement of Capillary and Melt Pool Geometry in Laser Welding

Abstract This paper describes a method to reconstruct the 3D shape of the melt pool and the capillary of a laser keyhole welding process. Three different diagnostic methods, including X-Ray and optical videography as well as metallographic cross sections are combined to gain the three dimensional data of the solidus-liquidus-surface. A detailed description of the experimental setup and a discussion of different methods to combine the 2D data sets of the three different diagnostic methods to a 3D-model will be given. The result will be a static 3D description of the welding process.

End-faced waveguide mediated optical propulsion of microspheres and single cells in a microfluidic device

Single cell transport in microfluidic devices is a topic of interest as their utility is becoming appreciated by cell and molecular biologist. Cell transport should minimize mechanical stress due to friction or pressure gradients. Optical forces have the advantage of applying their forces across the cell volume and not only at the cell membrane and are thus preferable. Optical pushing by scattering force is a suitable candidate so highly dependent on the photon irradiance field inside the propagation capillary which in turn is determined by the waveguide properties delivering the radiation pressure. Here we present a numerical approach to predict the optical scattering force, speed and trajectory of cells as a function of waveguide and propagation capillary geometry. Experimental verification of the simulation approach is demonstrated using polystyrene microspheres and leukemia cells. Effects of optical fibre to waveguide alignment, capillary wall angle and temperature on the dynamic viscosity on speed and position of the microspheres and cells inside the propagation capillary are demonstrated.

Control of Taper-Pinch Plasma by Geometrical Parameters of Capillary

We propose a new type of plasma source with a tapered pinch discharge to form dense, high-speed plasmas. Parameters controlling the behavior are indicated by considering the pinching dynamics of current sheet based on a 1-D equation of motion. The basic behavior of the plasma has been characterized as a function of those parameters using a prototype device. Results indicate that the plasma flux and velocity formed by the capillary discharge can be controlled by the initial gas density, the discharge current, and the geometry of capillary.

Impact of sulphur contamination on the oxygen transport mechanism through Ba0.5Sr0.5Co0.8Fe0.2O3−δ: Relevant issues in the development of capillary and hollow fibre membrane geometry.

Fabrication of dense perovskite membranes in the form of capillaries or hollow fibres is considered attractive for large-scale oxygen separation applications. For the preparation of such membranes by phase-inversion process polysulphone or polyethersulphone are commonly used as a binder. The decomposition of the sulphur-containing binder during the calcination leads to the formation of sulphates, which negatively affect the oxygen permeation through the membrane. The present work focuses on the comparative analysis of the oxygen transport mechanism through sulphur-free and -containing Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) membranes. The analysis of the thickness dependence of the oxygen permeation fluxes indicated that sulphates decrease the permeation rate mostly due to the partial blocking of the surface oxygen exchange, whilst the bulk ambipolar conductivity remains essentially unchanged. SEM/EDS studies revealed segregation of BaSO4 at the grain boundaries, which might be responsible for the fast oxygen exchange in phase-pure BSCF. The negative impact of sulphur contamination on oxygen permeation was more pronounced at temperatures below 1123K. It has been demonstrated, that, by surface activation, the oxygen flux through sulphur-containing BSCF membranes can be increased to the level of that of sulphur-free membranes.

FINITE ELEMENT ANALYSIS ON FLUID FILTRATION IN SYSTEM OF PERMEABLE CURVED CAPILLARY AND TISSUE

Fluid filtration across a capillary wall, which is associated with many diseases, is noteworthy for its significant role in cancer treatment. In this study, the coupled fluid dynamic phenomenon within a capillary and its surrounding tissues has been numerically analyzed in order to investigate the effect of capillary geometry, filtration coefficient, and tissue pressure on capillary filtration. The computational domain is composed of a fluid capillary subdomain coupled with a porous tissue subdomain. The flows in the sub-domains are described by the Stokes and Darcy equations, respectively, which are solved in a coupled manner by applying a nodal replacement scheme at the capillary wall. Distributions of pressure and flow velocity are presented, which show that the interfacial pressure drop is strongly influenced by permeability, tissue boundary pressure, and capillary radii. These results provide useful information on the relationship between the interstitial flow pattern and oxygen transport.

Mixed Conducting Ceramic Capillary Membranes for Catalytic Membrane Reactors: Performance of Ba<sub>0.5</sub>Sr<sub>0.5</sub>Co<sub>0.8</sub>Fe<sub>0.2</sub>O<sub>3-δ</sub> Capillaries

Oxygen-permeable perovskite ceramics with mixed ionic-electronic conducting properties can play an important role in the high temperature separation of oxygen from air. Such membranes are envisaged for application in catalytic membranes reactors and in oxy-fuel and pre-combustion technologies for fossil fuel power plants enabling CO2 capture. Since large-scale gas separation applications demand high membrane surface/volume ratios, membranes with capillary or hollow fiber geometry have a distinct advantage over tubular and flat sheet membranes. The fabrication and performance of Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) capillary membranes is presented. The capillaries were made by a spinning technique based on phase inversion using a sulfur or non-sulfur containing polymer binder. Attention is given to the polymer solution and ceramic spinning suspension in order to avoid the formation of macrovoids and achieve gastight membranes. The comparison of the performance of sulfur-free and sulfur-containing BSCF capillaries with similar dimensions revealed a profound impact of the sulfur contamination on both the oxygen flux and the activation energy of the overall oxygen transport mechanism. In addition the effect of activation layers on oxygen permeation is studied.