Rheological and microstructural characterization of WPI-stabilized O/W emulsions exhibiting time-dependent flow behavior

LWT ◽  
2012 ◽  
Vol 46 (2) ◽  
pp. 375-381 ◽  
Author(s):  
Pablo Bellalta ◽  
Elizabeth Troncoso ◽  
Rommy N. Zúñiga ◽  
José M. Aguilera
Keyword(s):  
Flow Behavior ◽  
Microstructural Characterization ◽  
Time Dependent ◽  
Dependent Flow

Time-Dependent Rheological Behavior of Fluids For Electronics Packaging

2005 ◽  
Vol 127 (4) ◽  
pp. 370-374 ◽  
Author(s):  
X. B. Chen
Keyword(s):  
Rheological Behavior ◽  
Printed Circuit Boards ◽  
Flow Behavior ◽  
Electronics Packaging ◽  
Time Dependent ◽  
Circuit Boards ◽  
Printed Circuit ◽  
Fluid Behavior ◽  
Surface Mounting

In electronics packaging, one of the key processes is dispensing fluid materials, such as adhesive, epoxy, encapsulant, onto substrates or printed circuit boards for the purpose of surface mounting or encapsulation. In order to precisely control the dispensing process, the understanding and characterization of the flow behavior of the fluid being dispensed is very important, as the behavior can have a significant influence on the dispensing process. However, this task has proven to be very challenging due to the fact that the fluids for electronics packaging usually exhibit the time-dependent rheological behavior, which has not been well defined in literature. In the paper a study on the characterization of the time-dependent rheological behavior of the fluids for electronics packaging is presented. In particular, a model is developed based on structural theory and then applied to the characterization of the decay and recovery of fluid behavior, which happen in the dispensing process due to the interruption of process. Experiments are carried out to verify the effectiveness of the model developed.

Characterization of the Time-Dependent Rheological Behavior of Fluids for Electronics Packaging

2003 ◽  
Author(s):  
X. B. Chen ◽  
W. J. Zhang ◽  
G. Schoenau ◽  
B. W. Surgenor
Keyword(s):  
Rheological Behavior ◽  
Flow Behavior ◽  
Electronics Packaging ◽  
Structural Theory ◽  
Time Dependent ◽  
Fluid Behavior ◽  
Proposed Model ◽  
Key Issues

To effectively control the dispensing process by which fluids are delivered onto substrates in electronics packaging, one of the key issues is to understand and characterize the flow behavior of the fluids being dispensed. However, this task has proven to be a demanding one as the fluids used for electronics packaging usually exhibit the time-dependent rheological behavior, which has not been well documented in the literature. In this paper, the characterization of time-dependent rheological behavior of fluids is studied. In particular, a model using the structural theory is proposed and applied to the characterization of the decay and recovery of fluid behavior, which are typically encountered in a dispensing process. Experiments are conducted to validate the proposed model.

Rheological Characterization of a New Alloy for Thixoforming

2008 ◽  
Vol 141-143 ◽  
pp. 301-306 ◽  
Author(s):  
Annalisa Pola ◽  
Roberto Roberti ◽  
Michael Modigell ◽  
Lars Pape
Keyword(s):  
Flow Behavior ◽  
Thermodynamic Simulation ◽  
Semisolid State ◽  
Rheological Characterization ◽  
Scanning Calorimetry ◽  
Globule Size ◽  
Semisolid Alloy ◽  
Dependent Flow ◽  
Mechanical Performances

A new aluminum alloy (AlSi5Mg0.5Cu0.3Ag) for semisolid die-casting applications was designed, starting from computational thermodynamics calculations by Computherm Database. The goal was to obtain a combination of good castability and proper concentration of hardening elements for strengthening precipitation treatment. The predicted thixotropic properties were verified by measuring the microstructural conventional parameters, such as globule size and shape factor, and the solidification range, by means of differential scanning calorimetry. To complete the characterization of this new alloy and to evaluate its applicability in industrial production, the shear rate and time-dependent flow behavior of the alloy in the semisolid state was studied in a Searle-type rheometer. A future aim of the present research is to try to use rheology testing as the tool to optimize the chemical composition, in order to design an alloy characterized by good mechanical performances and easy processability. Considering the strong influence of the solid fraction content on semisolid alloy viscosity, the rheology tests were interrupted after a certain time and the alloy was deeply freezed using vaporized liquid nitrogen, in order to fix the microstructure and verify the correctness of the thermodynamic simulation.

Microstructural characterization of CoPtCr/Cr thin film disks by cross-section TEM and elongated probe micro-diffraction

1991 ◽  
Vol 49 ◽  
pp. 762-763
Author(s):  
M.A. Parker ◽  
K.E. Johnson ◽  
C. Hwang ◽  
A. Bermea
Keyword(s):  
Magnetic Recording ◽  
Electron Probe ◽  
Microstructural Characterization ◽  
Crystallographic Structure ◽  
Recording Media ◽  
Layer By Layer ◽  
Cross Sectional ◽  
New Techniques ◽  
Polished Side

We have reported the dependence of the magnetic and recording properties of CoPtCr recording media on the thickness of the Cr underlayer. It was inferred from XRD data that grain-to-grain epitaxy of the Cr with the CoPtCr was responsible for the interaction observed between these layers. However, no cross-sectional TEM (XTEM) work was performed to confirm this inference. In this paper, we report the application of new techniques for preparing XTEM specimens from actual magnetic recording disks, and for layer-by-layer micro-diffraction with an electron probe elongated parallel to the surface of the deposited structure which elucidate the effect of the crystallographic structure of the Cr on that of the CoPtCr.XTEM specimens were prepared from magnetic recording disks by modifying a technique used to prepare semiconductor specimens. After 3mm disks were prepared per the standard XTEM procedure, these disks were then lapped using a tripod polishing device. A grid with a single 1mmx2mm hole was then glued with M-bond 610 to the polished side of the disk.

Microstructural Characterization of Au-Ge-Ni based ohmic contacts to GaAs/AlGaAs modfet device

1987 ◽  
Vol 45 ◽  
pp. 326-327
Author(s):  
A.K. Rai ◽  
A.K. Petford-Long ◽  
A. Ezis ◽  
D.W. Langer
Keyword(s):  
Contact Resistance ◽  
Ohmic Contact ◽  
Ohmic Contacts ◽  
Microstructural Characterization ◽  
Almost Everywhere ◽  
Spacer Layer ◽  
Good Contact ◽  
The Relationship ◽  
Lower Contact

Considerable amount of work has been done in studying the relationship between the contact resistance and the microstructure of the Au-Ge-Ni based ohmic contacts to n-GaAs. It has been found that the lower contact resistivity is due to the presence of Ge rich and Au free regions (good contact area) in contact with GaAs. Thus in order to obtain an ohmic contact with lower contact resistance one should obtain a uniformly alloyed region of good contact areas almost everywhere. This can possibly be accomplished by utilizing various alloying schemes. In this work microstructural characterization, employing TEM techniques, of the sequentially deposited Au-Ge-Ni based ohmic contact to the MODFET device is presented.The substrate used in the present work consists of 1 μm thick buffer layer of GaAs grown on a semi-insulating GaAs substrate followed by a 25 Å spacer layer of undoped AlGaAs.

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