9 research outputs found
Removing epoxy underfill between neighbouring components using acid for component chip-off
International audienc
Focussed microwave heating using degenerate and non-degenerate cavity modes
Microwave ovens have long been recognised as a means of reducing heating times versus
conventional convection ovens. The principle design feature is based on the procurement
of uniform heating within any material placed in the interior of the microwave cavity
oven. Materials within the oven are subjected to a degree of heating dependent on their
electromagnetic properties. For many applications, it is desirable to maintain control over
the distribution of heat deposition. This can be achieved through focussing of the electromagnetic
field within the cavity. Two new mechanisms are identified where an increased
level of control over the heating pattern and its location could be advantageous.
The research described within this thesis aims to improve heating selectivity in microwave
cavity ovens by the identification and enhanced control of modal patterns in degenerate
and non-degenerate resonators. This is achieved through the analysis of two novel oven
arrangements. The first of these addresses the requirement for highly selective heating in
hyperthermia treatment. It is demonstrated that proper selection of a forced degenerate
mode set can lead to an enhancement in field focussing within the centre of the cavity
through constructive and destructive interference of the fields in each mode pattern. It is
found that a highly selective peak of field can be produced within the centre of a large
cylindrical waveguide cavity for the purpose of hyperthermia treatment. The peak is produced
using a quasi degenerate mode set excited at approximately 1:3GHz.
The second example presents an open oven design for the curing of epoxy and encapsulant
materials within the micro-electronics packaging industry. It is intended that the
oven be placed on the arm of a precision alignment machine such that the curing and
placement stages of production be combined, suggesting an increase in production efficiency.
Two excitation schemes are presented based on the coupling of quasi degenerate
mode sets through a wide frequency range and the excitation of a single high order mode
enabling uniform field distribution for heating of encapsulant material and increased selective
heating through spatial alignment of modal field peaks, respectively.
Experimental results demonstrate the viability of the open-ended microwave oven for curing.
Both proposed excitation methods within the open oven design are investigated with
results presented. Optimisation of the heating fields is achieved through inclusion of lowloss
materials within the oven. Curing of an encapsulant material covering a commercial
chip package is achieved and the overall design validated
Nanowires for 3d silicon interconnection – low temperature compliant nanowire-polymer film for z-axis interconnect
Semiconductor chip packaging has evolved from single chip packaging to 3D heterogeneous system integration using multichip stacking in a single module. One of the key challenges in 3D integration is the high density interconnects that need to be formed between the chips with through-silicon-vias (TSVs) and inter-chip interconnects. Anisotropic Conductive Film (ACF) technology is one of the low-temperature, fine-pitch interconnect method, which has been considered as a potential replacement for solder interconnects in line with continuous scaling of the interconnects in the IC industry. However, the conventional ACF materials are facing challenges to accommodate the reduced pad and pitch size due to the micro-size particles and the particle agglomeration issue. A new interconnect material - Nanowire Anisotropic Conductive Film (NW-ACF), composed of high density copper nanowires of ~ 200 nm diameter and 10-30 µm length that are vertically distributed in a polymeric template, is developed in this work to tackle the constrains of the conventional ACFs and serves as an inter-chip interconnect solution for potential three-dimensional (3D) applications
Glass multilayer bonding for high density interconnect substrates
The aim of this research was the investigation of bonding borosilicate glass sheets, its trade mark CMZ, 100μm thickness, to create multilayer substrates capable of supporting high-density electrical interconnections. CMZ glass was chosen as it has a coefficient of thermal expansion that is close to that of silicon, thereby minimising thermal stresses in assemblies generated by manufacturing processes or service conditions. Two different methods of bonding the glass were used in this study; pressure assisted low temperature bonding (PALTB), and water glass bonding, using Sodium Trisilicate (Na2Si3O7) solution. These two bonding methods have already been applied in electronics manufacturing applications, such as silicon wafer bonding and multichip modules (MCMs). However, glass-to-glass bonding is a relatively new subject and this study is an attempt to standardise bonding processes. Additionally, the concept of using glass as a multilayer substrate provides a foundation for further exploration by other investigators.
Initial tests that were carried out before standardising the procedures for these two methods showed that a two-stage bonding process provided optimum results. A preliminary stage commenced by placing the cleaned (using Decon 90 solution) samples in a vacuum oven for 15 minutes, then heating at 100oC for 1hr. The permanent stage was then achieved by heating the samples in a conventional oven at temperatures from 200 to 400oC, for different periods. At this stage, the main difference between the two methods was the application of pressure (1-2MPa) during heating of the PALTB samples.
To evaluate the quality of the bonds, qualitative tests such as visual, optical microscope and dye penetrant were used. In addition, to estimate the strength and the rigidity of the interlayer bonds, two quantitative tests, comprising of deflection under cyclic stresses and crack opening were used. Thermal cycling and humidity tests were also used to assess resistance of the bonds to environmental effects.
The results showed that heating to 100oC was insufficient to enhance the bonds, as occasionally a sudden increase of deflection was observed indicating slippage/delamination. These bonds were enhanced during the permanent bonding stage by heating to 300oC in PALTB, under a pressure of 1-2MPa. The crack-opening test showed that the delamination distances of the bonds in the permanent stage were lower than that for preliminary bonding in both bonding methods. The delamination distances from the crack opening tests were used to calculate the strain energy release rate (GIC) and fracture toughness (KIC) values of the interlayers. The results showed that the KIC values of the permanent PALTB and water glass interlayers were higher than 1MPa.m0.5, while the KIC value of the CMZ glass, determined by linear elastic fracture mechanics, was around 0.8MPa.m0.5. The optical observations revealed that the prepared bonded sheets did not delaminate or break after thermal cycling and humidity tests
Human activity recognition for pervasive interaction
PhD ThesisThis thesis addresses the challenge of computing food preparation context in the kitchen. The automatic
recognition of fine-grained human activities and food ingredients is realized through pervasive sensing
which we achieve by instrumenting kitchen objects such as knives, spoons, and chopping boards with
sensors. Context recognition in the kitchen lies at the heart of a broad range of real-world applications. In
particular, activity and food ingredient recognition in the kitchen is an essential component for situated
services such as automatic prompting services for cognitively impaired kitchen users and digital situated
support for healthier eating interventions. Previous works, however, have addressed the activity
recognition problem by exploring high-level-human activities using wearable sensing (i.e. worn sensors
on human body) or using technologies that raise privacy concerns (i.e. computer vision). Although such
approaches have yielded significant results for a number of activity recognition problems, they are not
applicable to our domain of investigation, for which we argue that the technology itself must be genuinely
“invisible”, thereby allowing users to perform their activities in a completely natural manner.
In this thesis we describe the development of pervasive sensing technologies and algorithms for finegrained
human activity and food ingredient recognition in the kitchen. After reviewing previous work on
food and activity recognition we present three systems that constitute increasingly sophisticated
approaches to the challenge of kitchen context recognition. Two of these systems, Slice&Dice and Classbased
Threshold Dynamic Time Warping (CBT-DTW), recognize fine-grained food preparation
activities. Slice&Dice is a proof-of-concept application, whereas CBT-DTW is a real-time application
that also addresses the problem of recognising unknown activities. The final system, KitchenSense is a
real-time context recognition framework that deals with the recognition of a more complex set of
activities, and includes the recognition of food ingredients and events in the kitchen. For each system, we
describe the prototyping of pervasive sensing technologies, algorithms, as well as real-world experiments
and empirical evaluations that validate the proposed solutions.Vietnamese government’s 322 project, executed by the Vietnamese Ministry of
Education and Training
Microstructural and mechanical characteristics of micro-scale intermetallic compounds interconnections
Following the continually increasing demand for high-density interconnection and multilayer packaging for chips, solder bump size has decreased significantly over the years, this has led to some challenges in the reliability of interconnects. This thesis presents research into the resulting effects of miniaturization on the interconnection with Sn-solder, especially focusing on the full intermetallics (IMCs) micro-joints which appear in the 3D IC stacking packaging. Thereby, systematic studies have been conducted to study the microstructural evolution and reliability issues of Cu-Sn and Cu-Sn-Ni IMCs micro-joints.
(1) Phenomenon of IMCs planar growth: The planar IMCs interlayer was asymmetric and composed of (Cu,Ni)6Sn5 mainly in Ni/Sn (2.5~5 µm)/Cu interconnect. Meanwhile, it was symmetric two-layer structure in Cu/Sn (2.5~5 µm)/Cu interconnect with the Cu3Sn fine grains underneath Cu6Sn5 cobblestone-shape-like grains for each IMCs layer. Besides, it is worth noticing that the appearance of Cu-rich whiskers (the mixture of Cu/Cu2O/SnOx/Cu6Sn5) could potentially lead to short-circuit in the cases of ultra-fine (<10 µm pitch) interconnects for the miniaturization of electronics devices.
(2) Microstructural evolution process of Cu-Sn IMCs micro-joint: The simultaneous solidification of IMCs interlayer supressed the scalloped growth of Cu6Sn5 grains in Cu/Sn (2.5 µm)/Cu interconnect during the transient liquid phase (TLP) soldering process. The growth factor of Cu3Sn was in the range of 0.29~0.48 in Cu-Cu6Sn5 diffusion couple at 240~290 °C, which was impacted significantly by the type of substrates. And the subsequent homogenization process of Cu3Sn grains was found to be consistent with the description of flux-driven ripening (FDR) theory. Moreover, Kirkendall voids appeared only in the Cu3Sn layer adjacent to Cu-plated substrate, and this porous Cu3Sn micro-joint was mechanically robust during the shear test.
(3) Microstructural evolution of Cu-Sn-Ni IMCs micro-joint: There was obvious inter-reaction between the interfacial reactions in Ni/Sn (1.5 µm)/Cu interconnect. The growth factor of (Cu,Ni)3Sn on Cu side was about 0.36 at 240 °C, and the reaction product on Ni side was changed from Ni3Sn4 into (Cu,Ni)6Sn5 with the increase of soldering temperature. In particular, the segregation of Ni atoms occurred along with phase transformation at 290 °C and thereby stabilized the (Cu,Ni)6Sn5 phase for the high Ni content of 20 at.%.
(4) Micro-mechanical characteristics of Cu-Sn-Ni IMCs micro-joint: The Young s modulus and hardness of Cu-Sn-Ni IMCs were measured by nanoindentation test, such as 160.6±3.1 GPa/ 7.34±0.14 GPa for (Cu,Ni)6Sn5 and 183.7±4.0 GPa/ 7.38±0.46 GPa for (Cu,Ni)3Sn, respectively. Besides, in-situ nano-compression tests have been conducted on IMCs micro-cantilevers, the fracture strength turns out to be 2.46 GPa. And also, the ultimate tensile stress was calculated to be 2.3±0.7 GPa from in-situ micro-bending tests, which is not sensitive with the microstructural change of IMCs after dwelling at 290 °C
New techniques in astronomical spectroscopy for 8-m telescopes
The purpose of this thesis is to investigate new instrument technology to enhance the capabilities of 8-m telescopes. This thesis first describes the theory, design, construction, and testing of an immersed grating. Immersed gratings can be used to provide R≥ 10(^4) with a multi-object and/or integral field spectrograph on an 8-m telescope. Immersed gratings allow high resolution to be achieved whilst maintaining the required pupil size at a level similar to that on 4-m telescopes. This thesis describes laboratory tests which verify that immersed gratings provide high resolution. The throughput penalty in using an immersed grating is shown to be small with losses due to air-glass reflections, which can be eliminated with antireflection coatings, and metal-dielectric losses. This work demonstrates that immersed gratings provide a good method to reach R=10(^4) (and above) with a multi-aperture spectrograph on an 8-m telescope. The second part of this thesis describes the construction of a microlens-fibre based integral field unit (IFU): the SMIRFS-IFU. This instrument provides a unique J and H-band integral field capability for use with the CGS4 spectrograph at UKIRT. The optical design, assembly, laboratory testing, and telescope commissioning of the SMIRFS-IFU are described. The microlens arrays for use with SMIRFS-IFU were tested in detail and found to provide excellent image quality but with some scattered light. The assembly of the SMIRFS-IFU was achieved with high precision. The overall performance of the SMIRFS-IFU was found to be high and close to theoretical expectations. This instrument demonstrates that the technology of microlenses linked to fibres does provide a means of constructing high performance (i.e. high throughput, high spatial and spectral resolution) IFUs. Integral field spectroscopy is even more important for 8-m telescopes to take advantage of their enormous fight gathering power. The SMIRFS-IFU is an important upgrade to CGS4 to perform high spatial resolution integral field spectroscopy
The durability of solder joints under thermo-mechanical loading; application to Sn-37Pb and Sn-3.8Ag-0.7Cu lead-free replacement alloy
Solder joints in electronic packages provide mechanical, electrical and thermal connections. Hence, their reliability is also a major concern to the electronic packaging industry. Ball Grid Arrays (BGAs) are a very common type of surface mount technology for electronic packaging. This work primarily addresses the thermo-mechanical durability of BGAs and is applied to the exemplar alloys; traditional leaded solder and a popular lead-free solder.
Isothermal mechanical fatigue tests were carried out on 4-ball test specimens of the lead-free (Sn-3.8Ag-0.7Cu) and leaded (Sn-37Pb) solder under load control at room temperature, 35°C and 75°C. As well as this, a set of combined thermal and mechanical cycling tests were carried out, again under load control with the thermal cycles either at a different frequency from the mechanical cycles (not-in-phase) or at the same frequency (both in phase and out-of-phase).
The microstructural evaluation of both alloys was investigated by carrying out a series of simulated ageing tests, coupled with detailed metallurgical analysis and hardness testing.
The results were treated to produce stress-life, cyclic behaviour and creep curves for each of the test conditions. Careful calibration allowed the effects of substrate and grips to be accounted for and so a set of strain-life curves to be produced. These results were compared with other results from the literature taking into account the observations on microstructure made in the ageing tests.
It is generally concluded that the TMF performance is better for the Sn-Ag-Cu alloy than for the Sn-Pb alloy, when expressed as stress-life curves. There is also a significant effect on temperature and phase for each of the alloys, the Sn-Ag-Cu being less susceptible to these effects. When expressed as strain life, the effects of temperature, phase and alloy type are much diminished. Many of these conclusions coincided with only parts of the literature and reasons for the remaining differences are advanced
SPATIAL TRANSFORMATION PATTERN DUE TO COMMERCIAL ACTIVITY IN KAMPONG HOUSE
ABSTRACT Kampung houses are houses in kampung area of the city. Kampung House oftenly transformed into others use as urban dynamics. One of the transfomation is related to the commercial activities addition by the house owner. It make house with full private space become into mixused house with more public spaces or completely changed into full public commercial building. This study investigate the spatial transformation pattern of the kampung houses due to their commercial activities addition. Site observations, interviews and questionnaires were performed to study the spatial transformation. This study found that in kampung houses, the spatial transformation pattern was depend on type of commercial activities and owner perceptions, and there are several steps of the spatial transformation related the commercial activity addition.
Keywords: spatial transformation pattern; commercial activity; owner perception, kampung house; adaptabilit