Laurens Weiss

A thermodynamic noise model for nonlinear resistors

A Gaussian white noise model for passive nonlinear resistors, valid in the linear quadratic current-voltage (I-V) approximation at zero bias, is suggested. Although approximative, the model, which has originally been developed by R.L. Stratonovich, is thermodynamically well founded. The model is applied to the shot noise of exponential diodes and tunnel junctions as well as to the thermal noise of JFETs and MOSFETs. Within the range of the linear-quadratic approximation, the results are in full agreement with the well-known device specific standard low frequency thermal and shot noise models for these devices. The model can he considered as a linear-quadratic short circuit noise current generalization of Nyquists formula.

Noise analysis of nonlinear electrical circuits and devices

In this paper we discussed the mathematical modelling of thermal noise in linear and nonlinear electric networks and its physical interpretation. A new approach of thermal noise analysis in nonlinear networks with a well-defined physical interpretation is presented. It is illustrated by means of a few network examples.

Generalized Telegraphist's Equations for Deformed Waveguides

ABSTRACT Only in a few cases of special symmetries, an analytic solution of Maxwells Equations together with appropriate boundary conditions can be found. Among other things, difficulties occur because Maxwells Equations represent a set of coupled partial differential equations (PDEs). Therefore, methods have been developed to convert the PDEs with boundary conditions into a set of ordinary DEs. This simplification usually goes along with a loss of accuracy. In this paper, the prerequisites for the derivation of (stochastic) Generalized Telegraphists Equations (GTEs) for (irregular) deformed waveguides are discussed. It turns out that a systematic approximative derivation of GTEs is only possible in rare cases. In any case, further knowledge about the fabricational cause of the surface imperfections is needed to fix the stochastic properties of the GTEs. The methods application to an irregular deformed helix is used as an illustrating example.

Virtual prototyping methodology for assessment of the interaction between wire bond pad design and bond process parameters to enhance the robustness of copper wire bond interconnect

Wire bond interconnection still remains to be one of the most important fields of study in IC packaging development. The robustness of the interconnection between the bond wire and the bond pad are highly dependent on several key factors, mainly: 1) bond pad design, 2) capillary design, and 3) wire bond profile. Consequently, these factors also affect the package quality and reliability. Destructive test methods such as bond pull test and bond shear test are commonly used for Process Control to evaluate the interfacial strength between the bond wire and bond pad. However, these types of destructive test methods provide little or no insight about how the interaction of the aforementioned factors might affect the under-pad layers susceptibility to damage.

Characterization of adhesives for microelectronic industry in DMA and relaxation experiments for interfacial fracture toughness characterization — Difficulties and solution

Electrically conductive adhesives are widely used in semiconductor technology. The focus of this work is set on Isotropic Conductive Adhesives (ICA) with a high amount of electrically conductive filler particles. The aim of this work is the material characterization of highly filled epoxy based die attaches materials by dynamic mechanical analysis (DMA) and relaxation experiments in order to derive elastic and viscoelastic material models in a wide temperature range. The measurement of the epoxy based highly filled die attach material is a challenging topic. We show how to overcome the difficulties in measuring these materials. Critical interface fracture data, which include the Critical (Strain) Energy Release Rate Gc(Ψ) as a function of temperature, humidity or aging, are crucially needed in microelectronic industry for failure modeling, lifetime prediction and design evaluation associated with reliability [1], but they are rarely given in literature. Therefore fast measurement methods are needed [2, 3]. This work shows a measurement method of the critical fracture mechanic properties with the micro Mixed Mode Tester (μMMT) [2] on samples cut from real products and their numerical evaluation using linear elastic fracture mechanics and cohesive zone modeling.