Sensor data fusion is essential for environmental perception within smart traffic applications. By using multiple sensors cooperatively, the accuracy and probability of the perception are increased, which is crucial for critical traffic scenarios or under bad weather conditions. In this paper, a modular real-time capable multi-sensor fusion framework is presented and tested to fuse data on the object list level from distributed automotive sensors (cameras, radar, and LiDAR). The modular multi-sensor fusion architecture receives an object list (untracked objects) from each sensor. The fusion framework combines classical data fusion algorithms, as it contains a coordinate transformation module, an object association module (Hungarian algorithm), an object tracking module (unscented Kalman filter), and a movement compensation module. Due to the modular design, the fusion framework is adaptable and does not rely on the number of sensors or their types. Moreover, the method continues to operate because of this adaptable design in case of an individual sensor failure. This is an essential feature for safety-critical applications. The architecture targets environmental perception in challenging time-critical applications. The developed fusion framework is tested using simulation and public domain experimental data. Using the developed framework, sensor fusion is obtained well below 10 milliseconds of computing time using an AMD Ryzen 7 5800H mobile processor and the Python programming language. Furthermore, the object-level multi-sensor approach enables the detection of changes in the extrinsic calibration of the sensors and potential sensor failures. A concept was developed to use the multi-sensor framework to identify sensor malfunctions. This feature will become extremely important in ensuring the functional safety of the sensors for autonomous driving.

In electric vehicles with lithium-ion battery systems, the temperature of the battery cells has a great impact on performance, safety, and lifetime. Therefore, developing thermal models of lithium-ion batteries to predict and investigate the temperature development and its impact is crucial. Commonly, models are validated with experimental data to ensure correct model behaviour. However, influences of experimental setups or comprehensive validation concepts are often not considered, especially for the use case of prismatic cells in a battery electric vehicle. In this work, a 3D electro–thermal model is developed and experimentally validated to predict the cell’s temperature behaviour for a single prismatic cell under battery electric vehicle (BEV) boundary conditions. One focus is on the development of a single cell’s experimental setup and the investigation of the commonly neglected influences of an experimental setup on the cell’s thermal behaviour. Furthermore, a detailed validation is performed for the laboratory BEV scenario for spatially resolved temperatures and heat generation. For validation, static and dynamic loads are considered as well as the detected experimental influences. The validated model is used to predict the temperature within the cell in the BEV application for constant current and Worldwide harmonized Light vehicles Test Procedure (WLTP) load profile.

Soldering is a dominating process for semiconductor packaging. For electronic manufacturing tin based solders play a key role. The surface of most solder alloys is oxidized under an oxygen containing atmosphere. Usually reducing chemicals, called fluxing agents, are used to enable the formation of solder contacts. However, standard liquid flux leaves aggressive residues on the electronic devices. Clean processes were developed using gaseous flux, i.e. formic acid vapor. Despite the competitiveness of the reducing effect of formic acid vapour on many solder alloys, only little is known about the corresponding reaction mechanism, especially at the surface. An oxidized copper powder and a tin–silver–copper alloy were investigated using thermogravimetric and mass spectra analysis under formic acid flow. Details on the adsorbed and desorbed species and the formation of intermediates and decomposition products are presented. Activation temperatures are estimated and correlated with heating processes.

For environmental perception, autonomous vehicles and intelligent roadside infrastructure systems contain multiple sensors, i.e. radar (Radio Detection and Ranging), lidar (Light Detection and Ranging), and camera sensors with the aim to detect, classify and track multiple road users. Data from multiple sensors are fused together to enhance the perception quality of the sensor system because each sensor has strengths and weaknesses, e.g. resolution, distance measurement, and dependency on weather conditions. For data fusion, it is necessary to transform the data from the different sensor coordinates to a common coordinate frame. This process is referred to as multi-sensor calibration and is a challenging task, which is mostly performed manually. This paper introduces a new method for auto-calibrating three-dimensional (3D) radar, 3D lidar, and red-green-blue (RGB) mono-camera sensors using a static multi-target-based system. The proposed method can be used with sensors operating at different frame rates without time synchronization. Furthermore, the described static multi-target system is cost-effective, easy to build, and applicable for short to long-distance calibration. The experimental results for multiple sets of measurements show good results with projection errors measured as maximum root mean square error (RMSE) of (u,v) = (2.4, 1.8) pixels for lidar-to-camera calibration, RMSE of (u,v) = (2.2, 3.0) pixels for 3D radar-to-camera calibration and RMSE of (x,y,z) = (2.6, 2.7, 14.0) centimeters for 3D radar-to-lidar calibration.

Purpose: For soldering, flux is essential because it enables the wetting of the molten solder. Fluxless soldering, i.e. residue-free soldering with the aid of gaseous activators, has been known for many years, but is only well established in the field of opto- and microwave electronics where the solder is applied as preform. In high-volume SMD applications where solder paste is printed, this technology is rarely used until now. The reducing effect of a gaseous activator like formic acid vapor on certain solder alloys is known in practice. However, the corresponding reactions which occur under soldering conditions in nitrogen atmosphere have so far not been systematically investigated for different solder alloys. This study aims to analyze the different chemical reaction channels which occur on the surface of different solders, i.e. catalytical dissociation of formic acid on the pure or oxidized metal surface and the formation and evaporation of metal formates. Based on this analysis, a residue-free solder process under formic acid is developed for solder paste applications. Design/methodology/approach: In this paper, different solder alloys (SnAgCu, SnPb, BiSn, In) were analyzed with thermal gravimetric analysis (TGA) under formic acid flow. Details on mass change depending on the soldering temperature are presented. Activation temperatures are estimated and correlated to the soldering processes. Based on the analysis, fluxless solder pastes and suitable soldering processes are developed and presented. Major paste properties such as printability are compared to a commercial flux solder paste. High-power flip chip LEDs which can be assembled directly on a printed circuit board are used to demonstrate the fluxless soldering. Likewise, the soldering results of standard paste and fluxless paste systems after a reflow process are evaluated and compared. Findings: The experimental results show that TGA is an efficient way to gain deeper understanding of the redox processes which occur under formic acid activation, i.e. the formation of metal formates and their evaporation and dissociation. It is possible to solder residue-free not only with preforms but also with a fluxless solder paste. The resulting solder joints have the same quality as those for standard solder paste in terms of voids detected by X-ray and mechanical shear strength. Originality/value: In the fluxless soldering process, the reduction of oxide layers, and therefore the wetting of the solder spheres, is enabled by gaseous formic acid. After the soldering process, no cleaning process is necessary because no corrosive residues are left on the circuit boards and components. Therefore, soldering using solder paste without aggressive chemical ingredients has a high market potential. Expensive preforms could be replaced by paste dispensing or paste printing.

Reliability is one of the major requirements for power and opto-electronic devices across all segments. High operation temperature and/or high thermomechanical stress cause defects and degradation of materials and interconnects, which may lead to malfunctions with costly or even life-threatening consequences. To avoid or at least reduce failures, nondestructive testing (NDT) methods are common within development and production of power and opto-electronics. Currently, the dominating NDT methods are X-ray, scanning acoustic microscopy (SAM), and transient thermal analysis (TTA). However, they have different strengths and weaknesses with respect to materials and mechanical designs. This paper compares these NDT methods for different interconnect technologies, i.e., reflow soldering, adhesive, and sintered interconnection. While X-ray provided adequate results for soldered interfaces, inspection of adhesives and sintered interconnects was not possible. With SAM, evaluation of adhesives and sintered interconnects was also feasible, but quality depended strongly on the sample under test. TTA enabled sufficiently detailed results for all the interconnect applications. Automated TTA equipment, as the in-house developed tester used within this investigation, enabled measurement times compatible with SAM and X-ray. In the investigations, all methods revealed their pros and cons, and their selection has to depend on the sample under tests and the required analysis depth and data details. In the paper, guidelines are formulated for an appropriate decision on the NDT method depending on sample and requirements.