The present paper deals with the characteristic functions of distributed RC one-ports. It presents a detailed discussion about two characteristic functions of distributed RC networks: the time-constant density function and the dipole intensity function. Based on the properties of these functions, their transformation schemes are presented. Distributed and lumped-element examples are shown as a demonstration of the practical operations of these schemes. The paper also deals with the relation of these characteristic functions to the complex admittance, and introduces an identification method of RC one-ports in the admittance domain.

This paper deals with the description of general linear passive circuit features by using convolution equations. For this purpose, the variables of linear networks are transformed to the logarithmic scale, which is widely used in the case of frequency variable. On the other hand, it is an unconventional method for complex frequency and time variables.

This paper deals with the verification of thermal transient evaluation implementations. This subject is relevant because e.g. the upcoming standard will describe the thermal transient measurement as a standard method to estimate the junction-to-case thermal resistance [1], [2], thus anybody can create their own implementation of the evaluation method. We have to have a method to verify these implementations. For this reason we examined the result of the NID (Network Identification by Deconvolution) method from different aspects. For these examinations we defined a multilayer structure as a reference structure and we analytically expressed the unit-step response and the cumulative structure function of this structure. Using the unit-step response as an input data set for the implementation in question we got an approximation of the structure function. Analysing this and the reference RC network we could define a practical maximum tolerance for the deviation between the analytical and the calculated functions.

The transient thermal properties of an IC package are typically characterized by the thermal step-function response and/or by the time-constant spectrum. The temperature response is acquired from measurements or simulations while the time-constant spectrum is obtained from this response, using the NID method (Network Identification by deconvolution). The NID method is accurate only if the calculation is based on the exact step-function response. However, practical measurements provide us with responses which are more or less accurate but never absolutely exact. In our paper we present the sources of deviations and a method to eliminate their effect. We demonstrated the process on examples where the level of the corrected errors can be seen at various time-constants.

Integrated circuits exhibit coupled electro-thermal phenomena. The circuit elements dissipate heat, which propagates in the chip, rising the temperature of all circuit elements. Since the operation of the latter is temperature dependent, their dissipation will also change. This change results in the variation of the element voltages and currents, causing further changes in the dissipation, etc. Therefore we are facing a pair of couplings: an electronic → thermal one and a thermal → electronic one, meaning that all integrated circuits constitute essentially a mutually coupled electronic and thermal system. In this paper a detailed discussion of the electrothermal phenomena is presented regarding the practical implementation. The final implementation is a SPICE compatible electro-thermal solver (qSPICE), which implements some of the major industry standard models with extended coupled thermal capabilities. The accuracy of qSPICE is demonstrated on multiple examples.

This paper proposes a novel approach to measure and characterize thermal field changes caused by convective heat transfer through fluid flow in microchannels. A measurement technique is described to record thermal transfer impedance matrices. Fabrication and finite element simulation of a simple device are presented in order to demonstrate thermal coupling effects. A dimensionless number which describes the thermal coupling is also introduced.

The thermal management of semiconductor devices and systems has become a widely discussed topic over the past decades due to the ever increasing integration and the resulting power densities inside the packages. The increasing junction temperature is a great threat for the operation and the long-term reliability of the packaged device. One of the most important barriers in the heat conduction path is the thermal interface material. Their thermal performance significantly influences the overall thermal resistance of a system from the junction to the ambient. In this paper two approaches are described for the accurate thermal conductivity measurement of these materials; both techniques were developed in the framework of the European Nanopack project. One of them is a highly accurate, scientific method which benefits from the improvements of the semiconductor industry: the TIM is measured between two bare sensor chip surfaces. The other method is based on thermal transient testing and allows the measurement of a given grease or paste in its real environment. Both of them are capable of the measurement of highly conductive, nanoparticle based TIM materials. In this paper these two methods are explained in more details and measured results are compared with each-other. The effect of the measurement arrangement on the measured thermal resistance values is also discussed.

Due to the miniaturization seen in the last decades, several macro models that neglect some parameters have to be revised in order to evaluate the behavior of different types of microsystems precisely. In this paper we present the analysis of one such parameter which affects the thermal functionality, namely, the conduction of natural gases. In macro scale this parameter is usually neglected, because the conductivity of gases is several magnitudes smaller than that of the base materials. With the advance of microfabrication really good thermal isolation can be achieved and so the values of the conductivity of the air and of the base material can be evenly compared and as a consequence the former models have to be revised. This effect can be easily modeled on microstructures whose thermal resistance can be compared to the thermal resistance of natural gases. In order to observe its behavior appropriately, different types of cantilevers with embedded thermopiles and heating resistors were used. The modeling and experimental results show that in microsystems that are sensitive to temperature change, the parallel heat flow created by the surrounding gases may have significant impact on the operation.

Electro-statically driven micro-mechanical structures are an interesting and frequently used category of MEMS elements. Investigation of their properties is important both for better understanding the device operation and for fault detection and diagnosis. To follow the movement of micro-parts in such elements involves difficulties since device packages inhibit looking into the chip. Our motivation is to develop methods for tracing the movement of MEMS parts without optical inspection. This “blind” tracing seems to be possible by the recording and analysis of the charging/discharging current of the electro-static actuator.

In this paper the improvement of the original version of the ‘STATIM’ tester, designed for the high precision measurement of cutting-edge TIM materials is explained. Although the first design has validated the concept of the tester, the first hand-on experiences have set further requirements for a possible new design. The measurement of thermally conductive greases requires the precise setting of the bond line thickness, in a fine resolution. As the sensor chips are directly exposed to the samples to be measured, there is a change that they get damaged during the lifetime of the tester. In the following paragraphs the solutions for these problems are explained and measurement results are shown using the redesigned equipment.

Finite element simulation and post-processing results of calorimetric type microfluidic mass flow sensors are presented. The output characteristics of a calorimetric flow sensor are functions of the geometrical position of the temperature sensor elements. A given flow sensor (with a given technology on a given substrate) can be optimized for different flow ranges by determining the position of the temperature sensor elements. The simplified mathematical model of the steady-state thermal profile along the microfluidic channel is presented. It is also shown how the output characteristics depend on the position of the temperature sensors and the ratio of the convective and conductive heat transfer. The optimal parameters of a silicon substrate based microfluidic flow sensor for low and for high flow ranges were calculated by FEM simulation. Based on the simulation results the silicon substrate based microfluidic flow sensor could be optimized for different flow ranges.

The Structure functions based evaluation of the thermal transient measurements is now a broadly accepted way for the characterization of the time dependent behavior of the heat flow path. The usual way of generating structure functions considers one main heat flow path. By using a large mathematical tool set it generates for this path the Rth-Cth map of the structure. This enables an easy detection of partial thermal resistances in the heat flow path, with which we can determine the values of e.g. interface thermal resistances, etc. The accuracy that we can obtain with this methodology, working on simulated results is in the order of 2-5%. In this paper we present a methodology that enhances the accuracy of the structure function based evaluation method in case of measured thermal transient curves. In this procedure on one hand we measure the thermal transients for the system to be characterized and on other hand we measure the "parasitic" heat flow path, that influences our measurement. From the processing of the two measurements theoretically the errorless structure function of the measured structure can be generated. In this paper we present this methodology with mathematical details, and prove it with measured results.

Nowadays as thermal transient measurement is becoming a standard to investigate the thermal behavior of electronic devices, packages etc., the importance of avoiding any disturbances in the measured signal is also more relevant. One such thing that can corrupt the signal is the electrical crosstalk between different parts of the system or between the ambient and the whole system. However if the characteristic behavior of the crosstalk is known then special procedures can be designed in order to clean the corrupted signal from the disturbances. In our paper we present two methods to eliminate the disturbing effects caused by electrical crosstalk. The first approach is based on polarity inversion while the second utilizes multiple excitations to manage signal separation. To verify the feasibility of these methods, the procedure is demonstrated on electro-thermal MEMS devices.

Measuring the thermal resistance of thermal interface materials is an increasingly difficult task. The values to be measured are becoming smaller and smaller as a result of the huge efforts in material science to develop better thermal interface material in order to cope with the growing challenges of thermal management. In this paper we present the concept and some first results of a new TIM tester. The tester is using steady state measurement principle. With the help of dedicated test dies that are used to measure temperature, heat flux and parallelism at the same time, R-th values in the range of as low as 0.01 K/W can be measured with better than 5 % accuracy.

Lighting purpose organic light-emitting devices need special engineering because of the high electrical and thermal requirements of the operation. Our electro-thermal field simulation software is better to satisfy these special demands than the widely used commercial tools. This article surveys the special simulation needs of lighting purpose OLEDs, presents the electro-thermal extension of the FDM-based SUNRED thermal field simulator and the significant algorithmic changes for speed up the program and make it more flexible. The simulation of an existing OLED closes the paper.

In this paper the methodology and the results of a contactless thermal characterization of a high temperature test chamber will be introduced. The test chamber is used for fatigue testing of different MEMS devices where the homogenous temperature distribution within the close proximity from the heating filaments is very important. Our aim was to characterize the evolving temperature distribution inside the test chamber. In order to achieve smaller time constant a new contactless sensor card was developed. The contactless thermal characterization method introduced in this paper enables in situ heat distribution measurement inside the test chamber during operation, with the detection of potentially uneven heat distribution.

Thermal measurement and modeling of multi-die packages with vertical (stacked) and lateral arrangement became a hot topic recently in different fields like RAM chip packaging or LEDs and LED assemblies. In our present study, we present results for a more complex structure: an opto-coupler device with four chips in a combined lateral and vertical arrangement. The paper gives an overview of measurement and modeling techniques and results for stacked and multichip module (MCM) structures. It describes actual measurement results along with our structure function-based methodology which helps validating the detailed model of the package being studied. For stack-die packages, we suggest an extension of the DELPHI model topology. Also, we show how one can derive junction-to-pin thermal resistances with a technique using structure functions.

In this paper the design and implementation of a microfluidic flow sensor constructed on standard PWB (printed wiring board) and PDMS (Polydimethylsiloxane) technology is presented. The measurement principle is based on convective heat transfer. Calculations and computer aided simulations were performed to find optimal working conditions. A pressure-driven measurement system was built to characterize the device. The measurements confirmed that the flow sensor is able to work from 1.6 ml/min up to 10 ml/min range.