Mechanical Characterization of Compact Rolled-up Microtubes Using In Situ Scanning Electron Microscopy Nanoindentation and Finite Element Analysis

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 transfer is typically conducted by a pick-and-place process exerting enormous mechanical loads onto the 3D components that may cause catastrophic failure of the device. Herein, the mechanical deformation behavior of SRMs using experiments and simulations is investigated. SRMs using in situ scanning electron microscopy (SEM) combined with nanoindentation are characterized. This allows us to mimic and characterize mechanical loads as they occur in a pick-and-place process. The deformation response of SRMs depends on three geometrical factors, i.e., the number of windings, compactness of consecutive windings, and inner diameter of the microtube. Nonlinear finite element analysis (FEA) showing good agreement with experiments is performed. It is believed that the insights into the mechanical loading of 3D self-assembled architectures will lead to novel techniques suitable for a new generation of pick-and-place machines operating at the microscale. © 2021 The Authors. Advanced Engineering Materials published by Wiley-VCH Gmb

TILGen: A Program to Investigate Immune Targets in Breast Cancer Patients - First Results on the Influence of Tumor-Infiltrating Lymphocytes

Background: Despite advancements in the treatment of primary and metastatic breast cancer, many patients lack a durable response to these treatments. Patients with triple-negative breast cancer (TNBC) and human epidermal growth factor receptor 2(HER2)-positive breast cancer who do not have a pathological complete response (pCR) after neoadjuvant chemotherapy (NACT) have a very poor prognosis. Tumor-infiltrating lymphocytes (TILs) have been identified as a predictive marker for pCR after NACT in TNBC and HER2-positive breast cancer. These patient populations could also be suitable for novel treatment strategies including neoepitope-based therapies. This work analyses the effect of TILs on the pCR in neoadjuvantly treated patients in the TILGen study and presents the procedures aimed at establishing neoepitope-based therapies in this study. Methods: Neoadjuvantly treated HER2-positive and TNBC patients were eligible for the presented analysis concerning the association between TILs and pCR. A total of 146 patients could be identified within the TILGen study. TILs were evaluated as percentage of stromal tumor tissue in core biopsies at primary diagnosis. The phenotype ‘lymphocyte-predominant breast cancer' (LPBC) was associated with pCR by logistic regression adjusted for estrogen receptor status, progesterone receptor status, HER2 status, age at diagnosis, and grading. Results: LPBC was seen in 24 (16.4%) patients. In this patient group, 66.7% achieved a pCR, while the pCR rate was 32.8% in patients with a low TIL count. The adjusted odds ratio was 6.60 (95% confidence interval 2.02-21.56; p < 0.01). Conclusion: TILs are a strong predictor of pCR in TNBC and HER2-positive breast cancer patients. Implications for the use of this information including the effect on prognosis might help to identify patients most likely to benefit from a neoepitope-based therapy approach

Thermo-Mechanische Zuverlässigkeit von Flip-Chip Aufbauten mit Kühlkörpern

Flip-Chip Aufbauten auf organischem Substrat und rückseitig aufgebrachtem Kühlkörper werden auf ihre thermo-mechanische Zuverlässigkeit hin untersucht. Die Lebensdauer der Lotverbindungen unter der sich dabei ergebenden mechanischen Belastung wird mittels m odular-parametrischer FE-Simulation und im Experiment unter periodischer thermischer Wechselbelastung bestimmt. Zum ersten Mal liegen nun Design Regeln für solche Aufbauten vor.Flip-chip assemblies on organic substrate and reverse-side attached heat-spreaders are examined with respect to their thermo-mechanical reliability. The lifetime of the solder interconnects is determined under given mechanical and periodically varying thermal loads using modular-parametric Finite-Element simulation and thermal cycling experiments. For the first time design guidelines could be derived for such assemblies

Pull-Out Testing of SWCNTs Simulated by Molecular Dynamics

In this paper we present our results of simulating a pull-out test of single walled carbon nanotubes (SWCNT) out of a single crystal gold lattice by means of molecular dynamics. We compare the obtained force-displacement data of the pull-out test to results of simulated uniaxial tensile strain tests of SWCNTs. In doing so, we make a theoretical estimation about the quality of the clamping of SWCNTs in a gold crystal. We investigated the influence of chirality of SWCNTs and of the system temperature. Dependent on SWCNT chirality two different pull-out behaviours can be described. Zigzag nanotubes show stronger pull-out resistance than chiral or armchair nanotubes. Our results indicate a minor influence of embedding length of the SWCNT in the gold matrix on pull-out forces. The system temperature has only little effect on the maximum pull-out forces. The presented results have impact on design criteria of SWCNT-metal interfaces

Fracture mechanical characterization of micro- and nano-filled polymers by a combined experimental and simulative procedure

With the development of micro- and nanotechnological products such as sensors, MEMS and NEMS and their broad application new reliability issues will arise. The authors present a combined experimental and simulative approach targeted on unsolved questions of size effects within newly developed nanomaterials and highly integrated systems. The experimental approach is based on in-situ SPM scans of the analyzed object carried out at different thermomechanical load states. With the application of digital image correlation techniques displacement fields with nanometer accuracy are derived. A simulative approaches is performed by homogenization which is the modeling of a representative volume of bulk material taking into account spatial distribution of filler particles. The results of the homogenization are input data for standard finite element codes

Finite element simulations and raman measurements to investigate thermomechanical stress in GaN-LEDs

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 are applied to analyze and predict stress phenomena in gallium nitride (GaN) crystals grown on sapphire and implemented in blue light emitting diodes. The LEDs are assembled onto copper substrates by AuSn reflow soldering. The manufacturing process is simulated through FEM to investigate the stress distribution on the GaN layer. To validate the model, Raman measurements are performed to study the change in position of peaks in the spectrum in relation to the stress phenomena. Compressive stress with values of ca. 1400 MPa are recorded in the central area of the LEDs. Along the borders and at the corners, relaxation processes occur. The validation of the model allows to predict the behavior of the semiconductors in different thermal regimes, between -50 and 180 °C. The stress values do not change linearly by increasing the temperature. To take AuSn creep pohenomena in the FEM into account, after cross sectioning of the assembly, nanoindentation measurements were performed and creep deformation on the AuSn interconnection was measured at room temperature

Experimental contact angle determination and characterisation of interfacial energies by molecular modelling of chip to epoxy interfaces

This work presents an investigation of interfacial interaction between an industrial grade epoxy molding compound and a native silicon dioxide layer usually found at chip surfaces. The free surfaces of both solid materials were subjected to an experimental contact angle analysis of three different liquids (water, diiodomethane and glycerol). Results are compared to interaction energies found by analysis of molecular models of the interfaces, yielding reasonable agreement. Results of the simulation furthermore allow a qualitative prediction about the influence of water at the interface between chip and molding compound