Besi (Netherlands)

In this paper, we describe a method to predict the thickness of a stretched molding foil inside a mold. Because this foil will influence the overall dimensions of packages after molding, it is necessary to predict its thickness in advance when it is deployed in the cavity. In this way, dimensional corrections of the mold in the design phase can be made to meet the tight dimensional tolerances. Furthermore, the foil is not allowed to tear during molding. To assess the change of foil-thickness and the risk to tearing, models are developed. Firstly, a simplified foil stretching model is described for calculating the foil thickness in a two-dimensional rectangular geometry. Comparisons with measurements are made to prove this model. Secondly, a three-dimensional FEM simulation with the hyper elastic Odgen model on a complex geometry is performed and compared with measurements.

There is a high demand for the implementation of metallic nanoparticle (NP) sintering technology for die attach in high-power electronics. The performance of this technology is superior to that of the technology involving the use of lead-free solders. Although Cu NP paste is potentially a low-cost material, it faces the challenge of oxidation during sintering. This may result in a significant deterioration of the mechanical, thermal, and electrical properties. Therefore, there are limited studies on the in-air sintering of Cu NP pastes. The present study demonstrated the in-air pressure-assisted low-temperature sintering of a commercial Cu NP paste. Furthermore, the sintering was performed without using a protective atmosphere, unlike that in most of the previously reported investigations. The sintering behavior was investigated at three levels of temperatures (200–240 °C) and five levels of pressures (5–25 MPa). The joints that were sintered at high temperatures and pressures exhibited condensed microstructures and high bonding strengths. High sintering temperatures accelerated the diffusion between Cu NPs, while high sintering pressure facilitated the removal of evaporated organic compounds and the air between NPs. This not only facilitated sintering but also prevented the oxidation of Cu. The optimal sintering conditions promoted the formation of 3D connections between the Cu NPs, thereby increasing the shear strength of the sample. The samples that were sintered at 240 °C and 10 MPa experiences the highest increase in the shear strength, furthermore, the microstructures were optimized under this condition. The shear strength of 28.1 ± 8.47 MPa was achieved under this condition, which satisfied the requirements for die attach in high power electronics applications, moreover, the sintering process was moderate and cost-effective. Therefore, the optimal sintering temperature and pressure for the in-air sintering of the Cu NP paste was concluded to be 240 °C and 10 MPa, respectively. The results indicated that in-air sintering with pressure assistance can be applied for die attach in the high-power electronics.

In this work, a new wafer-level 3D packaging technology is developed to enable integration of an ultra-thin QFN-like (quad-flat no-leads) 3D package that targets both effective electrical and thermal properties and a thickness smaller than 200 µm. The proposed architecture allows 3D interconnection of stacked staggered dies and integration of compact, high-performance 3D integrated passive devices inside the package for added functionality and electrical performance. The developed technology consists of using debonding from a temporary carrier, Cu 2D-RDL (Redistribution Layer), accurate thin die pick & place, 3D-RDL and overmolding processes to integrate a QFN-like 3D package. Interconnection between die and package I/O is achieved using conformal 3D-RDL, thus without wire-bond, flip-chip or TSV.

Caused by its superior performance regarding bandwidth, power loss and form factors compound semiconductors like GaN or SiC recently moved into the interest of the semiconductor industry, particularly for applications in the high power segment. These improved performance parameters go along with increased power densities and thus, require a specifically optimized thermal concept of the packaging. Ag-sintering as die-attach process has been widely accepted as a promising alternative to soldering techniques with respect to thermal conductance. However, the thermal and the mechanical behavior of the sinter layer is influenced by its composition on the micro -and the macroscopic scale with respect to the presence of voids, inclusions and delamination but also the fractional content of porosity. Scanning acoustic microscopy (SAM) uses acoustic waves that interact with the mechanical properties of the sample materials and is thus, widely established for the non-destructive detection of voids, inclusions and delamination in microelectronic components. The current paper investigates the potential of SAM as a method for the assessment and characterization of the porosity in sintered Ag layers targeting the die-attach technology for novel power semiconductor devices.

An ultra-thin multi-LED package is designed, manufactured and its thermal performance is characterized. The objective of this study is to develop an efficient thermal modelling approach for this system which can be used for optimization of the thermal-performance of future ultra-thin designs. A high-resolution thermal imaging camera and thermocouples were used to measure the temperature distribution of the multi-LED package and the LED-die temperature for different operating powers. Finally, we compare the thermal measurements with the finite element simulation results. It is concluded that the modelling approach can assist in the thermal optimization of future multi-LED package designs.

Aus verschiedenen Bestandsaufnahmen balzender Hahne im Fruhjahr ergibt sich, das der Birkhuhnbestand in den Niederlanden die letzten Jahre weiterhin rucklaufig war. Ursache dafur durfte wohl der geringe jahrliche Zuwachs sein. Zu dessen Untersuchung wurden einige Hennen mit kleinen Sendern ausgerustet. Aus den vorlaufigen Ergebnissen geht hervor, das nicht alle Hennen erfolgreich bruten und auch Gelegeverluste sowie Kukenmortalitat von Bedeutung sind. Aus dem Verhalten der Hennen bei der Nahrungssuche ist herzuleiten, das das Kulturland um Heide- und Moorflachen herum als Nahrungsgebiet eine bedeutende Rolle spielt. Der Verlust des ursprunglichen Charakters dieses Kulturlandes durch veranderte Bewirtschaftungsmethoden, Meliorationen und Senkung des Grundwasserspiegels durfte der geringen Fortpflanzung der Birkhuhner zugrunde liegen.