The press-pack housing was initially available only in monolithic thyristors, diodes and GTOs for high power applications with strict reliability requirements. Due the technological developments of ...the last years, the IGBT became a common solution for power electronics converters including the higher power range. This trend and the positive experiences on the package created a demand for press-pack IGBTs. However, since the structure of the IGBT cannot be produced on a single wafer, the press pack housing was adopted for a multi die configuration resulting in a completely new structure. The electrical, thermal and mechanical behaviour of such a package is very sensitive to the applied clamping pressure. This paper discusses this dependency for different clamping devices and their resulting pressure distributions.
Mechanical analysis of press-pack IGBTs Poller, T.; Basler, T.; Hernes, M. ...
Microelectronics and reliability,
09/2012, Letnik:
52, Številka:
9-10
Journal Article, Conference Proceeding
Recenzirano
At present two packages for IGBT devices are available for applications in the MW power range: the bonded power module and the press-pack housing. Power modules have been object of extensive research ...including their thermo-mechanical characterisation under variable operating conditions and the analysis of their failure mechanisms. These aspects have been critical to improve the manufacturing process, increase reliability and provide lifetime estimations. The press-pack package eliminates bonding wires and solder layers, and is claimed to offer improved power cycling lifetime. However, the knowledge on press-pack devices is much less mature with only limited data published in literature related to their thermo-mechanical behaviour. This paper presents results of FEM simulations on a full 3D model of a press pack IGBT under power-cycling conditions and during the clamping process.
•A physic-based approach for life-time estimation in power cycling tests is presented.•The presented approach is supported by numerical simulations.•The simulation data is updated in each crack ...propagation step.
For the calculation of the lifetime of power modules only empirical lifetime models are available. These models represent a best-fit of a large number of results from power cycling tests, and are not derived from a physical model. In this paper a physic-based approach will be presented. Crack propagation in a solder layer, the increase of the thermal resistance and therewith the expected lifetime is calculated.
The target asymmetry
T
, recoil asymmetry
P
, and beam-target double polarization observable
H
were determined in exclusive
π
0
and
η
photoproduction off quasi-free protons and, for the first time, ...off quasi-free neutrons. The experiment was performed at the electron stretcher accelerator ELSA in Bonn, Germany, with the Crystal Barrel/TAPS detector setup, using a linearly polarized photon beam and a transversely polarized deuterated butanol target. Effects from the Fermi motion of the nucleons within deuterium were removed by a full kinematic reconstruction of the final state invariant mass. A comparison of the data obtained on the proton and on the neutron provides new insight into the isospin structure of the electromagnetic excitation of the nucleon. Earlier measurements of polarization observables in the
γ
p
→
π
0
p
and
γ
p
→
η
p
reactions are confirmed. The data obtained on the neutron are of particular relevance for clarifying the origin of the narrow structure in the
η
n
system at
W
=
1.68
GeV
. A comparison with recent partial wave analyses favors the interpretation of this structure as arising from interference of the
S
11
(
1535
)
and
S
11
(
1650
)
resonances within the
S
11
-partial wave.
Abstract
The target asymmetry
T
, recoil asymmetry
P
, and beam-target double polarization observable
H
were determined in exclusive
$$\pi ^0$$
π
0
and
$$\eta $$
η
photoproduction off quasi-free ...protons and, for the first time, off quasi-free neutrons. The experiment was performed at the electron stretcher accelerator ELSA in Bonn, Germany, with the Crystal Barrel/TAPS detector setup, using a linearly polarized photon beam and a transversely polarized deuterated butanol target. Effects from the Fermi motion of the nucleons within deuterium were removed by a full kinematic reconstruction of the final state invariant mass. A comparison of the data obtained on the proton and on the neutron provides new insight into the isospin structure of the electromagnetic excitation of the nucleon. Earlier measurements of polarization observables in the
$$\gamma p \rightarrow \pi ^0 p$$
γ
p
→
π
0
p
and
$$\gamma p \rightarrow \eta p$$
γ
p
→
η
p
reactions are confirmed. The data obtained on the neutron are of particular relevance for clarifying the origin of the narrow structure in the
$$\eta n$$
η
n
system at
$$W = 1.68\ \textrm{GeV}$$
W
=
1.68
GeV
. A comparison with recent partial wave analyses favors the interpretation of this structure as arising from interference of the
$$S_{11}(1535)$$
S
11
(
1535
)
and
$$S_{11}(1650)$$
S
11
(
1650
)
resonances within the
$$S_{11}$$
S
11
-partial wave.
The target asymmetry
T
, recoil asymmetry
P
, and beam-target double polarization observable
H
were determined in exclusive
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π
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and
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photoproduction off quasi-free protons and, for the first time, off quasi-free neutrons. The experiment was performed at the electron stretcher accelerator ELSA in Bonn, Germany, with the Crystal Barrel/TAPS detector setup, using a linearly polarized photon beam and a transversely polarized deuterated butanol target. Effects from the Fermi motion of the nucleons within deuterium were removed by a full kinematic reconstruction of the final state invariant mass. A comparison of the data obtained on the proton and on the neutron provides new insight into the isospin structure of the electromagnetic excitation of the nucleon. Earlier measurements of polarization observables in the
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γ
p
→
π
0
p
and
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γ
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reactions are confirmed. The data obtained on the neutron are of particular relevance for clarifying the origin of the narrow structure in the
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η
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W
=
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GeV
. A comparison with recent partial wave analyses favors the interpretation of this structure as arising from interference of the
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11
(
1535
)
and
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S
11
(
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)
resonances within the
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S
11
-partial wave.
We compared the amount of radiation-induced DNA damage and the extent of DNA repair in human melanoma cells (MeWo) using the 'comet assay' after neutron, boron neutron capture and X-irradiation. ...Using a colony-forming assay it was shown earlier that lethal effects in tumour cells treated with fast neutrons may be increased by the neutron capture reaction 10B(n,alpha)7Li. The effectiveness of boron neutron capture in killing tumour cells depends on the number of 10B atoms delivered to the tumour, the subcellular distribution of 10B and the thermal neutron fluence at the side of the tumour. Using the 'comet assay' the DNA damage of fast neutrons (mean energy 5.8 MeV) was shown to be significantly greater than for the same absorbed dose of X-rays. The presence of 600 ppm 10B (boric acid H3 10BO3) in the cell medium during irradiation with d(14)+ Be neutrons in a phantom enhances the DNA damage by 20 compared with neutron irradiation alone. After DNA damage induction by neutrons and neutron capture of boron, the DNA repair capacity of the MeWo cells is significantly reduced in comparison with X-irradiation resulting in proportionally more residual DNA damage after 180 min of repair time.
This thesis explores the process of archaeological interpretation by considering how we can interpret the Iron Age settlement in Wigtownshire, SW Scotland. Traditional images of Iron Age warfaring ...hierarchical societies have persisted through the use of well-established classifications, such as 'fort' or 'roundhouse' and by the uncritical acceptance of the definition and identification of 'settlement' in the archaeological record. Alternative interpretations of Iron Age settlement landscapes are possible by considering a variety of other observations, which traditional classifications ignore, such as the landscape context of specific monuments. This thesis presents a critical review of these alternative interpretations and other more traditional classifications used to define Iron Age settlement and illustrates how multiple narratives of the past can co-exist. This thesis emphasises the essential part classification plays in archaeological interpretation. Interpretation is a complex and ongoing process and it is important to be aware of the assumptions that we make and how these may affect further interpretations of the archaeological evidence. Common standardised classifications stress the importance of certain morphological characteristics over other observations and the interpretations of the archaeological evidence are therefore restricted. Traditional approaches neglect the importance of context, which is integral to the interpretation of the archaeology on many levels. Understudied, but archaeologically rich, Wigtownshire is an ideal case-study. Rather than limiting the discussion of archaeological features by only comparing them through traditional 'typologies', here experiential observations of the evidence - within their landscape context - offer an alternative approach by which the iron Age in Wigtownshire can be considered. A flexible process of classification is advocated - dependent upon the research questions that are addressed in particular studies. My approach to the re-evaluation of the Iron Age settlement in Wigtownshire is also influenced by a critique of the definition of the term 'settlement' in archaeology. The identification of 'domestic' practices in contrast to 'ritualised' ones in the Iron Age evidence is questioned and from a variety of perspectives the complex processes of settlement in the Iron Age are explored.
In this book the authors review the field and explore the potential role of RNAi and other RNA technologies in cardiovascular medicine and research. They highlight the impressive recent progress but ...also the hurdles that still must be overcome before this promising technology is finally ready for translation and clinical use.
