Heraeus (Germany)

Abstract Understanding the aging mechanisms of materials is essential for improving the reliability of power modules in the field of power electronics. This study investigates the reliability of silver-sintered joints, focusing on the fatigue behavior of copper active-metal-brazed (AMB) substrates under thermal cycling with respect to the copper grain size ranging from 250 to 960 µm. Analytical techniques, including confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD), were used to analyze the fatigue behavior of bare copper substrates. Silver joint reliability of sintered samples was evaluated by scanning acoustic microscopy (SAM), die shear testing, and cross-sectional microstructural observation. The findings indicate that thermal cycling induces thermo-mechanical stresses, resulting in localized plastic deformation, surface defects, and out-of-plane displacement of individual grains in the copper sheet, leading to surface roughening and crack formation in the silver layer. In terms of Ag joint reliability, a clear correlation to the copper grain size is revealed. Larger copper grains exhibit pronounced deformation, leading to high thickness variations in the adjacent silver layer, which critically affects the joint reliability. This research emphasizes that fine-grained copper substrates can enhance the reliability of the silver joints in power electronic applications.

Wire bonding is an important technique in microelectronics packaging; high precision vertical wire bonding (vertical array arrangements) is investigated in detail in the memory sector with stacked devices. This study focuses on the development of vertical wire bonding using bonding wires ranging from 18 to 30μm in diameter, including gold (Au), silver (Ag), and copper (Cu) based wires. The vertical wire bonding method is evaluated on four stacked and conventional devices. Factors such as vertical wire post height, wire diameter, and wire elongation are examined. Bonding assessments encompass a range of vertical wire post heights from 100μm to 1mm. A stable bonding process window is determined for a low variation in post height (ΔH) within 10μm for tested ranges from 150 to 500μm. Wires with moderate ductility, exemplified by a 4% Elongation (EL) in 4N (99.99%) Au and Coated-Ag, exhibited with low variation in X-shift and Y-shift, along with post height across the studied elongation range of 2-8% EL. All the examined wire types: 4N Au, 2N (99%) Au, gold coated silver (Coated-Ag), Alloyed-Ag, gold flash palladium (Pd) coated copper (AFPC), and bare Cu (soft 4N Cu), met the precision requirements for vertical wire bonding. The study reveals that vertical wire bonding, a key process for microelectronics assembly in stacked devices, can be achieved with a collection of wire materials, given that proper attention is directed towards optimizing factors such as wire diameter, elongation, vertical wire post height, and capillary types/dimensions.

BackgroundAmphotericin is admixed to Polymethylmethacrylic (PMMA) spacers for fungal periprosthetic joint infections (PJI) during two-stage exchanges. We aimed to analyse the mechanical properties of PMMA cement with admixed Amphotericin B.Materials and methodsWe tested Amphotericin in PMMA cement mechanically, its elution properties in vitro and present two cases of fungal PJI treated with Amphotericin B powder in Copal cement in vivo.ResultsSterile Amphotericin B is not available as a pure substance but only as powder for infusions. PMMA mixed with such pharmaceutical Amphotericin B formulations colored the cement orange. Compression strength was slightly decreased, bending and impact strength significantly decreased whereas bending modulus was increased. Drug elution was high within the first 24 h and decreased over time until day 5. Amphotericin B in combination with Copal was successfully used in two cases with Candida ssp. infections. No negative side effects, especially no nephrotoxic effects, were observed. Sterile Amphotericin B powder for preparing an infusion solution contains only small amounts of pure drug. In vivo polymicrobial Candida-infections with bacterial co-infection were successfully treated using the combination of Copal cements with added Amphotericin B without systemic nephrotoxic impact.ConclusionsThe addition of Amphotericin B to PMMA cement affects the cement’s properties in vitro whereas in vivo the combination with Copal is clinically successful in treating complex cases of fungal PJI.Level of evidenceLevel IV.

The aim of this work is to explore the laser powder bed fusion (LPBF) processability window of the nanocrystalline soft magnetic Finemet alloy. With that purpose, several laser power and scan speed values and a meander scanning strategy were probed to process simple geometry specimens. Good dimensional accuracy was obtained within the entire processing window investigated. Relative densities as high as 89% were achieved for processing conditions including high laser power and low scan speeds. The fraction of amorphous phase, which peaked at 49%, was found to be mostly dependent on the scan speed and only slightly influenced by the laser power. The microstructure of the crystalline domains is formed by ultrafine, equiaxed grains with random orientations. Irrespective of the processing conditions, the LPBF-processed samples exhibit a similar saturation magnetization, lower permeability, and higher coercivity than fully amorphous melt-spun ribbons of the same composition. The coercive field of the additively manufactured specimens is fairly independent of the relative density and exhibits a moderate inverse variation with the amorphous fraction. Consistent with earlier works, this study suggests that the average grain size is an important contributor to coercivity.

Cu/Nb laminated metallic composites (LMCs) exhibit extraordinary mechanical strength while electrical conductivity is maintained at a high level. In this research, Cu‐based LMCs with varying volume fraction of niobium are produced via accumulative roll bonding (ARB) and additionally cold‐rolled and heat‐treated to identify the role of these heterogeneous phase boundaries on the overall sheet properties. Deformation structures in these layered materials are studied through scanning transmission electron microscopy investigations. The existence of an interface‐affected zone at the phase boundaries and mechanical intermixing is attributed to decreasing electrical and increasing mechanical properties, especially in very thin layered LMCs. Atom probe tomography measurements show that mechanical alloying occurs due to severe plastic deformation during ARB processing of the laminates. An additional subsequent heat treatment leads to chemical demixing at the interfaces of the phase boundaries.

An in‐depth analysis of phase transformations in a Pd–Cu–Ag alloy, crucial for applications in hydrogen membranes and electrical components, is presented. The investigation emphasizes the influence of the deformation rate and addition of Ag on the formation of the ordered CuPd phase. This study focuses on a specific alloy composition, 49.1% Cu–41.3% Pd–8.3% Ag–1.3% Ru, investigating its behavior under various conditions. Through comprehensive analysis, including the influence of the initial state, deformation variations, and chemical composition modifications, high‐energy X‐ray diffraction to unveil detailed phase evolution dynamics is used. Surprisingly, experimental findings deviate from the anticipated phase diagram, uncovering a previously unrecognized three‐phase region with the formation of AgPd. Notably, the study reveals the pivotal role of the alloy's Ag content in the development of ordered CuPd and AgPd phases. The addition of Ru exhibits no involvement in the observed phase transformations, contributing to the understanding of the alloy's composition‐dependent behavior. This research provides valuable insights into the intricate interplay of factors influencing phase transformations, offering a nuanced perspective beyond theoretical predictions. The newfound understanding of Ag's role and Ru's inertness refines material design considerations, enhancing the grasp of the alloy's thermodynamic stability under varying conditions.

Although well-accepted clinical practice guidelines exist for the diagnosis of prosthetic joint infection (PJI), little is known about the quality of diagnosis for PJI. The identification of quality gaps in the diagnosis of PJI would facilitate the development of care structures and processes to shorten time to diagnosis and reduce the significant morbidity, mortality, and economic burden associated with this condition. Hence, we sought to develop valid clinical quality measures to improve the timeliness and accuracy of PJI diagnosis. We convened a nine-member multidisciplinary national panel of PJI experts including orthopedic surgeons, infectious disease specialists, an emergency medicine physician, and a patient previously treated for PJI to review, discuss, and rate the validity of proposed measures using a modification of the RAND-UCLA appropriateness method. In total, 57 permutations of six proposed measures were rated. Populations considered to be at high enough risk for PJI that certain care processes should always be performed were identified by the panel. Among the proposed quality measures, the panel rated five as valid. These novel clinical quality measures could provide insight into care gaps in the diagnosis of PJI.

Periprosthetic joint infection (PJI) in geriatric and/or multimorbid patients is an enormous challenge for orthopaedic surgeons. Revision procedures have also been demonstrated to expose patients to higher infection risks. Prior patient stratification according to presumed infection risks, followed by a more potent local antibiotic prophylaxis protocol with selective use of DALBC, is an interesting strategy to decrease the burden of PJI in high risk patients.The PubMed & EMBASE databases were screened for publications pertaining to the utilization of DALBC in cement for infection prophylaxis & prosthesis fixation. 6 preclinical & 7 clinical studies were identified which met the inclusion criteria and were stratified by level of clinical evidence. Only those studies were considered which compared the PJI outcome in the DALBC vs the SALBC group.DALBC have been shown to exert a much stronger and longer lasting inhibition of biofilm formation on many PJI relevant bacteria (gram-positive and gram-negative pathogens) than single gentamicin-only containing cements.DALBC use (COPAL G+C) in the intervention arm of 7 clinical studies has led to a significant reduction of PJI cases in a) cemented hemiarthroplasty procedures (3 studies, evidence level I and III), in b) cemented septic revision surgeries (2 studies, evidence level III), in c) cemented aseptic knee revisions (1 study, evidence level III) and in d) cemented primary arthroplasties in multi-morbid patients (1 study, evidence level III-IV). These benefits were not associated with more systemic side effects or a higher prevalence of broad antimicrobial resistancies.Use of DALBC is likely to be more effective in preventing PJI in high risk patients. The preliminar findings so far may encourage clinicians to consolidate this hypothesis on a wider clinical range.