Novel approach to copper sintering using surface enhanced brass micro flakes for microelectronics packaging

Copper pastes suitable for low temperature and low pressure die-attach bonding were developed to enable sintering at 275 °C under N2 atmosphere. First, brass flakes were treated with HCl to selectively etch Zn and to realize enhanced surface modifications on the flakes. Then, polyethylene glycol was added as binder to the modified flakes due to its reducing effects on copper oxides and its property to prevent agglomeration. Shear strength of ca. 50 MPa was achieved while sintering with 10 MPa bonding pressure thereby providing suitable, easy and low-cost sintering pastes for microelectronics packaging applications

INFRA-3DRC Dataset

The INFRA-3DRC Dataset is a public dataset comprised of 3D automotive Radar and RGB camera data generated using an intelligent roadside infrastructure (also known as smart infrastructure) setup. This work is supported by the Bavarian Ministry of Economic Affairs, Regional Development and Energy (StMWi), Germany within the Project “InFra — Intelligent Infrastructure.

Copper die bonding using copper formate based pastes with alpha- terpineol, amino-2-propanol and hexylamine as binders

Copper sintering is gaining prominence as a prospective alternative to silver sintering in die-attach applications. However, process temperatures and sintering times are still high compared to silver sintering and a challenge for large scale industrialization. In this paper, rapid and low temperature die-attach bonding using copper formate based inks is investigated. While these inks are successfully used to form metal traces on substrates by inkjet and aerosol printing, they reveal a substantial challenge for die-attach bonding. Based on results using polyethylene glycol (PEG) as binder, different pastes were realized and investigated using binders which form metal complexes with copper formate. Beside the promising result using PEG, best bonding results were obtained using α- terpineol as binder while traditional conductive ink binders amino-2-propanol and hexylamine caused challenges during pre-drying, degassing and in establishing a reliable interconnect

Multi-Sensor Data Fusion for Real-Time Multi-Object Tracking

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

Die-attach bonding for high temperature applications using thermal decomposition of copper(II) formate with polyethylene glycol

A copper paste based on commercial available copper(II) formate microparticles and polyethylene glycol as binder has been developed for bonding of semiconductor dies onto substrates below 300 \ub0C. Thermal decomposition of copper(II) formate leads to the formation of copper nanoparticles, which are used to connect the chip electrically and mechanically to the substrate by a sinter process. The binder provides printability of the paste, protects the copper particles from oxidation and supports the formation of fine copper nanoparticles. Shear tests of the sintered interconnects return shear strength values of 60 MPa, offering a promising solution to form pure copper interconnects

Comparison of Nondestructive Testing Methods for Solder, Sinter, and Adhesive Interconnects in Power and Opto-Electronics

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

Detection of Solder Joint Cracking of High Power LEDs on Al-IMS During Temperature Shock Test by Transient Thermal Analysis

An innovative sensitive test method is developed to detect solder joint cracking for high power LED packages. The method is based on transient thermal analysis and can replace the dominating Light-On test. Test groups of LED packages were soldered with two different lead free solders (SnAgCu 305 and Innolot FL-640) on Aluminum Insulated Metal Substrate and exposed to temperature cycles. Transient thermal measurements were performed directly after assembly and after specific cycle numbers. After data processing the increase of the relative thermal resistance between the initial signal at \u20180\u2019 cycles and \u2018n\u2019 cycles is obtained and correlated with cracks in the solder joint by cross sections. The transient curves are reproduced by time resolved finite element analysis. Based on the simulation, a failure criterium is defined representing a crack length of 30% of the solder joint area. A higher creep resistance for the test group soldered with Innolot FL-640 compared to the test group soldered with SAC 305 is observed

Simulations and Experiments to Analyze Stress Phenomena in Soldered and Sintered Interconnections between Silicon Nitride chips and Copper Substrates

Thermomechanical stress in microelectronics packaging systems is a very complex phenomenon. Understanding of behaviours of the systems, in terms of origin, assessment and impact of the stress on an assembly, is a successful strategy to develop devices with high performances and reliability. Based on the fine element method, virtual prototypes can be investigated to simulate the thermomechanical behaviour and stress in real assemblies. Micro-Raman spectroscopy is a valid method to determine the stress distribution in a material because the perturbation due to stress can be observed as variation of wavenumber of phonon modes. In this paper, a FEM model is developed and experimental results of Raman investigations are compared to the theoretical results obtained from the model. The model and the processing approach are validated by the analysis of the stress in test assembles where Si3N4 chips are bonded onto Cu substrates via AuSn-soldering, SAC305-soldering, and Cu-sintering. Compressive stress with values between 150 and 1100 MPa is determined in Si3N4/AuSn/Cu assemblies