Bernhard Wunderle

• Prof. Dr.-Ing. Dipl.-Phys
• Head of Department at Chemnitz University of Technology

Among biobased materials, date palm leaf fiber (DPLF) is a cellulose-rich fiber with considerable potential for use in sustainable composites, where it can improve mechanical properties and reduce weight. In this study, a flexible piezoelectric generator (PEG) composed of a polydimethylsiloxane (PDMS) polymer, lead-free barium titanate (BaTiO3), an...

Hybrid piezoelectric nanocomposites (HPCs) for nanogenerators are strongly dependent on the properties of the used materials. Traditional methods like solid-state approaches yield low piezoelectric properties, leading to nanogenerators (PENGs) with reduced capabilities. In this work, the piezoelectric material composition Ba0.85Ca0.15Zr0.10 Ti0.90O...

With current advances in automated driving, optical sensors like cameras and LiDARs are playing an increasingly important role in modern driver assistance systems. However, these sensors face challenges from adverse weather effects like fog and precipitation, which significantly degrade the sensor performance due to scattering effects in its optica...

In the realm of automated driving, the need for highly reliable environmental perception sensors is paramount for ensuring the safe operation of advanced driving assistance systems (ADAS). Moreover, these systems represent a sharply increasing cost factor in modern vehicles. Hence, numerous works focus on investigating and modeling sensor performan...

The vision of a deep learning-empowered non-destructive evaluation technique aligns perfectly with the goal of zero-defect manufacturing, enabling manufacturers to detect and repair defects actively. However, the dearth of data in manufacturing is one of the biggest obstacles to realizing an intelligent defect detection system. This work presents a...

Graphical abstract to our paper titled "Synthetic data generation using finite element method to pre-train an image segmentation model for defect detection using infrared thermography". For more details, read the article (open access), the doi: https://doi.org/10.1007/s10845-024-02326-1

The majority of qubit chip integration is realized in a two-dimensional (2D) architecture. Whereas 3D architecture enables more advantages like efficient interconnect routing, allowing for more compact qubit coupling geometries, reducing form factor, and increased connectivity beyond nearest-neighbor interactions. Flipchip (FC) assembly has been de...

With the rise of driving automation, optical sensors like cameras and LiDAR are playing a crucial role in vehicle perception. However, these sensors face challenges from harsh environmental conditions, including extreme temperatures and weather effects like fog and precipitation, which degrade their performance due to particle scattering. Consequen...

In the realm of automated driving simulation and sensor modeling, the need for highly accurate sensor models is paramount for ensuring the reliability and safety of advanced driving assistance systems (ADAS). Hence, numerous works focus on the development of high-fidelity models of ADAS sensors, such as camera, Radar as well as modern LiDAR systems...

In this work, a Thermal Test Vehicle (TTV) is developed to demonstrate the thermal characterization utilities for large die area packages. The TTV consists of a silicon Thermal Test Chip (TTC) on organic interposer assembled with lid and thermally conductive adhesive as thermal interface material. The setup mimics the system-level application and t...

The thermo-mechanical robustness of Advanced Driving Assistance Systems is crucial to leverage the growing market of automated driving. Especially in case of optical sensors, such as camera and Light Detection and Ranging (LiDAR) sensors, the thermo-mechanical state of the sensor front end is closely coupled with its optical performance. Deformatio...

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) are 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 transfe...

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...