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We study the dynamics of acoustic phonons in ultra-thin free-standing silicon membranes both experimentally and theoretically. We discuss the impact of the lifetimes of the acoustic phonons on the thermal transport properties of the membranes with thicknesses ranging from 8 nm to 1.5 µm. The phonon lifetimes are determined by measuring the dynamic variation of the reflectivity using ultra-fast pump-probe...
Acoustic properties of materials in the high gigahertz range are still barely understood, even for well characterized materials like silicon. Acoustic phonons play an important role in dephasing processes as well as in thermal transport in general. Silicon thin films are widely used in the semiconductor microelectronics industry. By measuring the phonon lifetimes in silicon membranes, we hope to further...
This paper investigates the thermal behaviour of thin crystalline silicon solar cells and determines whether the decrease in cell thickness affects the temperature dependences of the solar cell parameters. For the investigation crystalline solar cells with different photoactive layer thicknesses were processed. Sample cells were formed on n+-substrate wafers with n epitaxial layers where due to the...
The paper presents a new, nondestructive method of determination of the air-tightness of metal packagings of transistors. This method is based on the thermoacoustic approach with a microphone detection. Thermoacoustic approach means that the sound is generated by the periodical temperature of the element caused by the periodical electric power dissipation in it. In the paper both the experimental...
This paper details current status of modelling for power electronics modules and details the challenges in terms of electrical, thermal, reliability and robustness analysis. Multi-domain, multi-physics and multi-objective optimisation toolsets are urgently required for future integrated power electronics. The paper illustrates future trends in power module designs and provides examples of current...
In this paper an effective approach is proposed for generating stochastic compact thermal models of electronics components and packages. The approach exhibits high levels of accuracy for very small state space dimensions of the model. It is also efficient since it requires the solution of few deterministic thermal problems in the frequency domain. The achieved stochastic compact models can be used...
Natural convection heat transfer occurs when the fluid buoyancy motion is induced by density differences themselves caused by the heating. A temperature gradient causes a density variation in a cooling fluid with a related local change in the refractive index. The gradient of refractive index has the effect of bending the light. The thermal load of the device causes an optical deflection in the cooling...
In this work, we present a toolset suitable for the analysis of thermal behavior of FPGA devices. The toolset allows for the automatic synthesis of a unified temperature measurement and heat generation infrastructure combined with the necessary control structures and communication interfaces. The tools insert temperature sensors and heaters based on ring oscillators through the low level manipulations...
Various techniques allow measuring the thermal conductivity of materials ranging from bulk to thin-film sizes. Among them, one can find the 3ω method, scanning thermal microscopy or Raman thermometry. The standard 3ω method is not spatially-resolved since it requires a long deposited metallic wire. It is also intrusive. In contrast, the two other techniques have spatial resolution ranging from few...
Since the semiconductor silicon carbide presents attractive opportunities for the fabrication of novel electronic devices, there is significant interest in improving its material quality. Shrinking component sizes and high demands for efficiency and reliability make the capability to release excess heat an important factor for further development. Experience from Si and Diamond tells us that isotopic...
Polymers are important enablers for electronic systems. Current trends and challenges for the application of polymers in electronics are described. The transition to electro mobility leads to rising power density of automotive electronics. Therefore, polymers with high thermal stability and excellent heat dissipation are required. Within the EU funded FP7 project NANOPACK, Bosch investigated different...
This paper deals with the development und fabrication of a thermal test chip (TTC) to be used for thermal characterisation and qualification of materials and packages. The TTC is designed as a modular chip with the smallest full functional chip cell of 3.2mm × 3.2mm and consists of a heater structure and a temperature sensor. The chips can be applied in any required matrix. Heater and temperature...
We have investigated various kinds of nanowires (Si, Bi2Te3, SiGe) in order to evaluate the influence of the nanostructuration on their thermal conductivity. The method used is a 3ω-SThM (Scanning Thermal Microscopy) technique which enables to simultaneously measure the topography and the thermal conductivity on an assembly of NWs. We detail the procedure from the measurement itself to the nanowire...
New packaging technologies are necessary to meet the demand for smaller and more reliable electronic devices. The socalled system-in-package (SiP) concept brings different technologies, material combinations and processes together in one package. To ensure the reliability of such a package reliable, fast and non-destructive failure analysis are needed. Transient thermal methods provide techniques...
Thermal Transient Testing is a method practically used to determine the thermal model of an integrated circuit's case and cooling facilities. The traditional measurement setup of this diagnostic examination does not allow in-circuit testing in case of fully digital semi-custom devices, such as complex programmable logic devices (CPLDs), field programmable gate arrays (FPGAs) and programmable system...
This paper discusses how the square-root-t method improves the measurement of the virtual junction temperature Tvj in a power cycling test setup. By applying this method, the measurement becomes more tolerant to measurement delays and EMC noise, thus it enables to sharpen the basis of life time estimations. However the virtual junction temperature remains a one dimensional mapping of the three-dimensional...
We report on the reduction of the thermal conductivity in ultra-thin suspended Si membranes with high crystalline quality at room temperature. A series of membranes with thicknesses ranging from 9 nm to 1.5 µm was investigated using Raman thermometry, a novel contactless optical technique for thermal conductivity determination. The temperature rise of a laser spot focused on the membranes was monitored...
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