Bernhard Wunderle

Technische Universität Chemnitz · Department of Electrical Engineering and Information Technology

New reliability requirements for power modules due to increasing demands, new materials and new technologies render classical empirical lifetime models not sufficient anymore. The paradigm change towards a physics-of-failure framework for lifetime modeling within power electronics offers the possibility to connect stress tests, microstructural anal...

The employment of sintered silver (SAG) as die attach material is one of the most promising solutions to utilize the advantages of wide bandgap semiconductors in modern power electronic packaging. Its electrical, thermal and mechanical – i.e. reliability correlated – properties are far superior to those of time honored eutectic solders. To master t...

Autonomous driving is a key vehicle capability for future mobility solutions that relies on the reliability of its high-performance vehicle computer. As for any electronics for automotive applications, thermal management is a crucial point. A very extensively employed approach for improving heat removal is the usage of heat spreaders in the form of...

Electronic components of which reliability cannot be quantified are unacceptable and potentially hazardous, especially in safety-relevant areas such as driver assistance systems and medical technology where the zero-error principle applies. Reliability as a quality criterion has its origin in production, i.e. process variations have a negative infl...

In the paper, μ-Raman spectroscopy is applied as non-destructive test method to access the creep in chip intercon-nection materials. To develop the method, a silicon test chip is soldered onto a copper substrate using SAC305 and the strain of the silicon crystal in the top surface of the chip is measured time dependent after assembly by the Raman s...

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...

Barium Titanate (BaTiO3) lead-free ceramic has recently gained the attention for the fabrication of nanogenerators. Herein, lead-free piezoceramics (Ba, Ca) (Zr, Ti)O3 was synthesized using the sol-gel method. In order to improve the material properties, Ca²⁺ and Zr⁴⁺ were introduced into the BaTiO3 crystal network to replace Ba²⁺ and Ti⁴⁺, respect...

Wearable sensors are gaining attention in human health monitoring applications, even if their usability is limited due to battery need. Flexible nanogenerators (NGs) converting biomechanical energy into electrical energy offer an interesting solution, as they can supply the sensors or extend the battery lifetime. Herein, flexible generators based o...

In this study, we demonstrate the capabilities of lock-in thermography (LIT) for the inspection of sintered chip interconnections. The laser LIT technology is used to detect delamination in the sintered layer between copper pad and SiC chip. This work will present a LIT system for the failure analysis (FA) without spray coating for industrial inspe...

The prediction of high-resolution mechanical stress distributions in electronic chips with a view to improving prognostic and health management in electronics and N/MEMS via artificial intelligence-based processing of measurement data is the focus of this study. Temperature, shear, and differential stress time-series data acquired through piezo-res...

The mechanical stability of self-assembled Swiss-roll microstructures (SRMs) is explored by in-situ scanning electron microscopy, nanoindentation and finite element analysis. In this article, number 2100412, by Somayeh Moradi, Dmitriy D. Karnaushenko, Oliver G. Schmidt, and co-workers, the influence of geometric parameters on the stability of SRMs...

Self‐assembled Swiss‐roll microstructures (SRMs) have been widely explored to build up microelectronic devices such as capacitors, transistors or inductors as well as sensors and lab‐in‐a‐tube systems. These devices often need to be transferred to a special position on a microchip or printed circuit board for the final application. Such a device tr...

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...

Sintered silver (SAG) is a widely-used die attach (DA) technology in automotive industry, especially for power modules in electric vehicles (EV) defined by higher power densities. High operation temperatures (> 175°C) are particularly resulting from the application of dies based on wide bandgap semiconductors materials like SiC and GaN. The thermo-...

Nowadays, the development of sustainable and wearable energy harvesters is gaining an increasing interest. Herein, an approach used to develop a high performance flexible nanogenerator based on hybrid piezoelectric composite is reported. The approach consists first of employing solution mixing method with different solvents to determine the suitabl...

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...

Typical failures in microelectronics range from misalignments, non-uniform filling, delamination, missing solder bumps, large voids and cracking. Many non-destructive methods are available to inspect and detect these functional faults. Raman spectroscopy and Finite Element Modeling (FEM) are applied to analyze and predict stress phenomena in galliu...

Local thermomechanical stress can cause failures in semiconductor packages during long‐time operation under harsh environmental conditions. This study helps to explain the packaging‐induced stress in blue GaN‐LEDs soldered onto copper substrates using AuSn alloy as lead‐free interconnect material. Based on the finite element method, a virtual proto...

Nanoanalysis Sensoric micro and nanosystems involve research from materials chemistry, solid‐state physics, and microelectromechanical engineering. In article number 1900106, Evgeniya Sheremet, Peter Meszmer, Raul D. Rodriguez and co‐workers present recent advances in scanning probe microscopy applied to micro‐ and nanoelectromechanical systems.

We explore the capabilities of creep testing for the reliability and robustness assessment of die attach layers within this paper. To this end we conducted finite element simulations and experiments. We optimised our setup in terms of thermal stability and measurement accuracy with the introduction of a temperature monitoring system, and with the i...

This article features the evolution of carbon nanotubes (CNTs) as functional material in nano and microelectromechanical systems (N/MEMS). Introducing material morphologies for the CNTs in a homologue series (single CNTs – bundles, fibers, yarns – networks and thin films), different concepts for mechanical sensors based on the intrinsic and extrins...

In this study we present the capabilities of an infrared failure analysis system to (automatically) detect defects in various samples from different fields of application in electronic industries. For this purpose, we developed a production line simulator with a sample transfer via conveyor belt and an integrated pulsed infrared thermography system...

Interfacial delamination in semiconductor packages during their lifetime is a reliability risk. For the realisation of a “Design for Reliability” approach, the whole product needs to be studied virtually using Finite Element simulations. Only this approach allows for the evaluation of possible failure mechanisms, which is an integral part of risk a...

This feature article covers the nano‐analysis methods for four key material characteristics: electrical and electronic properties, optical, stress and strain, and chemical composition. With the downsizing of the geometrical dimensions of electronic, optoelectronic, and electromechanical devices from the micro to the nanoscale at the one hand and th...

Carbon nanomaterials are important for future sensors and electronics. Defects determine the material properties, therefore, it is critical to find new ways to investigate defects at the nanoscale. In this context, Raman spectroscopy (RS) is the tool of choice to study defects in carbon nanomaterials. On the other hand, Kelvin probe force microscop...

Active power cycling (APC) is a standardized and well-established method for reliability assessment and product qualification in power electronics (PEs) technologies. Repetitive pulses of load current are applied to cause cyclic thermal swings in the p–n junction and in the whole semiconductor device. They induce thermo-mechanical stresses, which u...

This paper reports on concepts, technology, integration aspects, and results of a MEMS‐based test platform for reliability tests of micro and nano objects. Building blocks of this platform to be used in in‐plane push‐pull‐configurations are a thermal actuator, a force sensor, and a displacement sensor as well as several types of samples to be integ...