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Publications (84)
The tilt of semiconductor dies is a common issue during assembly in power electronics as, e.g. die bonding during silver sintering caused by inhomogeneous thicknesses of applied die-attach material, problems with a homogeneous force application, uneven substrates etc. This tilt usually leads to reliability problems later during testing or operation...
Pulsed Infrared Thermography (PIRT) is a very fast and non-destructive technique for testing various types of specimens. This makes PIRT interesting for inspections in industrial production lines. Especially for the die attach interface inspection of sintered and soldered electronic components and layer to layer interfaces in fiber-reinforced plast...
Tilt of semiconductor dies is a common issue during assembly in power electronics as e.g., die bonding during silver sintering caused by inhomogeneous thicknesses of applied die-attach material, problems with a homogeneous force application, uneven substrates etc. This tilt usually leads to reliability problems later during testing or operation in...
This study shows a technique to avoid the necessary spray-coating of devices under test with low- emissivity surfaces in failure analyses by pulsed IR thermography. Such samples can be sintered or soldered electronic components. The mentioned technique is based on a vacuum foil lamination process, which does not contaminate the samples and saves th...
Defekte elektronische Bauelemente zeigen oft eine anormale Verteilung oder zusätzliche Verlustleistungsquellen. Durch Joulesche Wärmeerzeugung führt dies zu lokalen Temperaturerhöhung. Neben stationärer Thermografie, die auf Temperaturänderung größer einiger 100 mK begrenzt ist, nutzt man die IR LockIn-Thermografie (LIT), um Temperaturänderungen bi...
Integration of more functionality and smaller chips into decreasing package volume leads to increasing heat generation. In addition, the use of new compound semiconductors like SiC and GaN require a high thermal conductivity of the interconnect materials. One of the promising solutions is a layer of sintered silver between semiconductor and substra...
This paper deals with the development of a new test stand for thermal diffusivity measurement based on Ångström's method (called TIMAwave™). The concept of the test stand has been proved by FE simulation and experiments on standard samples. The test stand has been realized and integrated into the hardware of the already existing test stand LaTIMA™,...
On the present work, samples of carbon fiber/epoxy composites with different void levels were fabricated using hand layup vacuum bagging process by varying the pressure. Thermal nondestructive methods: thermal conductivity measurement, pulse thermography, pulse phase thermography and lock-in-thermography, and mechanical testing: modes I and II inte...
The cost and the package size driven size reduction of semiconductors lead to much higher heat generation. Also the use of new high power technologies on the basis of SiC produces is a need for high conductivity of the interconnect materials. Therefore the requirements for mechanical, thermal and electrical properties of interconnect materials incr...
This paper deals with the development of an innovative test stand for the measurement of thermal and electrical conductivity of metals, semiconductors, highly conductive die attaches and substrates using the steady state technique for thermal characterization and four-terminal sensing with pulse delta technique for electrical characterization. We p...
Today, there is no non-destructive, simple, inexpensive and yet accurate in-situ monitoring technique for cracks and delamination available for routine use in electronic package testing. However, such a method is highly desirable, as delamination testing is part of every qualification programme in industry. Rapid failure analytical techniques which...
In dieser Arbeit wurde eine neue fehleranalytische Methode zur industriellen Anwendung an neuen Technologien der Aufbau- und Verbindungstechnik entwickelt. Das Verfahren basiert auf der Wechselwirkung von thermischen Wellen und Defekten.
Die Besonderheit ist dabei die Zerstörungsfreiheit, die Geschwindigkeit, das Auflösungsvermögen und die durch n...
This paper deals with the development of a new test stand for determination the thermal conductivity of metals, semiconductors, highly conductive die attaches and substrates using the steady state technique. We designed the test stand and optimized it by FE simulation to have flexibility for the selection of the sample size and measurement paramete...
In this paper, a novel concept of a thermo-mechanical MEMS actuator using aluminum thin-film heaters on a thermal oxide for electrical insulation is presented. The actuator is part of an universal tensile testing platform for thermo-mechanical material characterization of one dimensional materials on a micro- and nano-scopic scale under different e...
The steady state method is a commonly used and in principle simple way to measure thermal resistance and conductivity of thermal interface materials (TIMs). The sample must be positioned between a hot and a cold plate with constant temperatures, whereby a heat flow through the sample and temperature gradient across the sample are generated. To dete...
This paper deals with the system design, technology and test of a novel concept of integrating Silicon power dies along with thermo-electric coolers and a phase change heat buffer in order to thermally manage transients occurring during operation. The concept features double-sided cooling as well as new materials and joining technologies to integra...
The steady state method is a commonly used and in principle simple way to measure thermal resistance and conductivity of thermal interface materials (TIMs). A heat flow through the TIM has to be generated and the temperature gradient across the TIM has to be measured. This is also defined by the ASTM standard ASTM D5470 [4]. To generate the heat fl...
In this paper, a new and dedicated phase change cooling concept is discussed, following the goal to buffer periodic overload operations of electric power modules and thus keeping junction temperatures constant. A top-mounted latent heat storage material (LHSM) buffer is applied, to soak the overload heat in conjunction with thermo-electric coolers...
In this paper, building blocks of a MEMS tensile testing platform are presented. The building blocks include a thermo-mechanical MEMS actuator, driven by an aluminum thin-film heater on a thermal oxide for electrical insulation, a capacitative displacement sensor and a piezoresistive force sensor, capable of measuring forces on a nano-newton scale....
This paper deals with the system design, technology and test of a novel concept of integration Si and SiC power dies along with thermo-electric coolers in order to thermally manage transients occuring during operation. The concept features double-sided cooling as well as new material and joining technologies to integrate the dies such as transient...
Commonly computational methods are used to determine and enhance the lifetime of electronics and electronic systems. The validity of such methods highly depends on the used material data and therefore on the quality of the accompanying experiments. For this reason different methods were combined to better determine the thermal state of a desired de...
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 appli...
New packaging technologies are necessary to meet the demand for smaller and more reliable electronic devices. The so-called 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 ne...
This paper proposes a guideline for the mechanical acceleration of end-of-lifetime prognostics of metal based thermal interfaces. As die attach material, we used an advanced nano-effect sintered silver layer as interface between die and steel substrate which has very good electrical and thermal conductivities. Two types of experiments/simulations a...
For properties characterization of nanostructured materials and simultaneously to predict their reliability a tensile testing system consisting of a thermal actuator and a lateral nano-Newton force piezoresistive sensor is presented. The implementation of a piezoresistive load sensor in a MEMS-based tensile testing system can be regarded as an inno...
New packaging technologies are necessary to meet the demand for smaller and more reliable electronic devices. The so-called 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 ne...
http://www.leibniz-institut.de/ns2012/abo_ras_thermal_interface_characterization_micro-nano.pdf
This paper presents a comprehensive method for obtaining urgently required critical interface delamination data of material pairings used in electronic packaging. The objective is to thereby enable rapid, inexpensive and accurate lifetime prediction for that failure mode. A new testing method is presented which allows large mode-angle range and enh...
Thermal interface materials (TIMs) are widely needed to improve thermal contacts for facilitation heat transfer in electronic packaging, such as that associated with the flow of heat from microprocessor to a heat spreader or a heat sink in a computer. Due to thermal mismatch between these components mechanical strain occur which cause pump-out, cra...
Thermal interface materials (TIMs) are widely needed to improve thermal contacts for facilitation heat transfer in electronic packaging, such as that associated with the flow of heat from microprocessor to a heat spreader or a heat sink in a computer. Due to thermal mismatch between these components mechanical strain occur which cause pump-out, cra...
Designers of electronic packages and electronic circuits require thermal optimization for electrical and thermal plated through holes (PTH) respectively to obtain a reliability estimate. Reliability depends on PTH-geometry and manufacturing process conditions which influence thermo-mechanical properties of the board (viscous-elasticity) and electro...
The ongoing need for miniaturization and speed in electronics industry has brought a requirement for better performing thermal management systems. One of the major bottlenecks in thermal management is the thermal interface resistance. Characterisation of thermal interface materials become even tougher a challenge at low bond line thicknesses and hi...
As the demand for new thermal technologies and materials has been increasing over the years to provide thermal solutions to the next generation of power electronics, microprocessors and high-power optical systems also thermal characterisation methods have to keep up with the pace of this development with respect to resolution and accuracy. We have...
Nowadays very often IR-thermography is used to analyze the temperature on electronic device surfaces. To measure the absolute surface temperature correctly, the IR-camera detector has to be calibrated with a corresponding evaluation software using a black body calibration device. Commercially available black radiators are heavyweight and a calibrat...
Nowadays very often IR-thermography is used to analyze the temperature on electronic device surfaces. To measure the absolute surface temperature correctly, the IR-camera detector has to be calibrated with an corresponding evaluation software using a black body calibration device. Commercially available black radiators are heavyweight and a calibra...
As the demand for new thermal technologies and materials has been increasing over the years to provide thermal solutions to the next generation of power electronics, microprocessors and high-power optical systems also thermal characterisation methods have to keep up with the pace of this development with respect to resolution and accuracy. Within t...
The use of multilayer ceramic chip capacitors as integrated passive in, e.g., system in package applications needs methods to examine and predict their reliability. Therefore, a nondestructive failure analytical technique is described to detect cracks in the ceramic and the metallic layers within encapsulated 0402 surface mount device (SMD) capacit...
Taking the advantage of the thermo-elastic effect, while using an infrared camera system, the mechanical stress could be made visible. The stress concentrations at the tip of a subcritical crack growth could clearly be detected. Through the observation during the periodic loading of a CT-specimen the crack growth rate can be determined. For this pu...
IR-thermography has become increasingly important for non-destructive testing of microelectronic devices and structures on chip, package and board-level. This paper focuses on the evaluation of best applicability for different pulse excitation modes to detect flaws and damages as well as to determine material properties. Pulse IR thermography using...
Thermal characterisation of thermal interfaces becomes even tougher a challenge at low bond line thicknesses and higher thermal conductivities of the interface materials as more accurate measurement techniques are required. As in parallel the quest for high conductivity adhesives and greases is ongoing, a correlation between thermal bulk or interfa...
This paper proposes a new effective thermal material simulation model as well as a non-destructive failure analysis for multi-layer substrates with thermal vias to derive exact failure data to supplement existing lifetime models. An effective thermal material simulation model is derived which is validated in simulation and experiment in transient m...
Prime concerns in designing liquid cooling solutions are performance, reliability and price. To that end a one-phase liquid cooling concept is proposed, where all pumps, valves and piping are fully integrated on board level. Only low-cost organic board technology and SMT processes are used in the design. This paper addresses the key issues of such...
The use of multi-layer ceramic chip capacitors as integrated passive in e. g. system in package applications needs methods to examine and predict their reliability. Therefore, a nondestructive failure analytical technique is described to detect cracks in the ceramic and the metallic layers within encapsulated 0402 SMD capacitors. After choosing fro...
In this paper new characterization equipment for thermal interface materials is presented. Thermal management of electronic products relies on the effec-tive dissipation of heat. This can be achieved by the optimization of the system design with the help of simulation methods. The precision of these models relies also on the used material data. For...