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Resin-reinforced silver (Ag) sintering material is an effective and highly reliable solution for power electronics packaging. The hybrid material’s process parameters strongly influence its microstructure and pose a significant challenge in estimating its effective properties as a thin interconnect layer. This research demonstrates a novel 3D reconstruction methodology for the microstructural investigation of the resin-reinforced Ag sintering material from OverMolded Plastic (OMP) packages. Based on the reconstructed models with different sintering parameters (temperature and time), the fraction of Ag and Resin volume distribution, the connectivity of silver particles, and the tortuosity factors were estimated. A 99% connectivity of sintered Ag particles was achieved with various sintering conditions, such as 200°C for 2 hours, 200°C for 4 hours, and 250°C for 2 hours. However, coarsening of Ag particles was promoted when sintered at 250°C. Increasing the sintering time at 200°C had insignificant changes. The estimated tortuosity factor also indicated that sintering at 250°C provides the shortest heat transport path between the semiconductor die and the package substrate. In order to quantify the microstructural findings, the OMP packages’ thermal performance with different sintering conditions (temperature, time, and interconnect thickness) was experimentally assessed. Although the experimental measurements were less sensitive to the effective interface thermal resistances’, the measurement results show a good correlation with the microstructural analysis. Sintering the Resin-reinforced Ag sintering material at higher temperatures (250°C) seems to improve the package thermal performance, and increasing the sintering time at 200°C has a negligible effect., Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Electronic Components, Technology and Materials

The objective of this article is to investigate the thermal-fatigue properties of a commercially available lead-free solder alloy (SnBiAgCu) under the use of different types of potting compounds. Solder alloys with lower silver content are expected to substitute the conventional solder alloys SAC305 (Sn-3.0Ag-0.5Cu). First, the tensile behavior and creep behavior of the SnBiAgCu solder alloys were studied at three temperatures (25, 75, 125). Results show that this type of solder alloys presented higher tensile strength and creep deformation endurance than conventional SAC305 solder alloys. Second, a dynamic mechanical analysis was performed to get the storage modulus and glass transition temperature of three types of potting compounds, which were used in the thermal-fatigue simulation. Third, the experimentally determined material data was used for the averaged strain energy density increment calculated by the finite element method. This simulation approach was selected as damage metrics to evaluate solder interconnect reliability under different combinations of materials. It is found that the application of potting compounds will increase strain energy density significantly when compared with the strain energy density calculated without potting compound, which means that potting compounds will deteriorate the thermal-fatigue reliability of solder interconnects. These accurate data-driven simulation models can in the future form the basis for compact digital twins for predicting useful remaining lifetime., Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Electronic Components, Technology and Materials

This article shows the fabrication process and packaging of through polymer optical vias (TPOV). The TPOV enables encapsulation and packaging of silicon photonic systems using film assisted molding (FAM) and the creation of micron-sized through polymer optical vias. The optical vias are lithographically defined in thick film photo-resist (∼ 300 μm) and parallel processed on substrate level. Placing and connecting optical windows on individual chips using pick & place is a difficult and time-consuming process because of the stringent requirements on alignment accuracy, cost and throughput. In this work we provide a solution to this problem by combining microfabrication technology with back-end film assisted molding technology for a new packaging approach for the integration of optical windows. As feasibility study we show through polymer optical windows on optical encoder Si photodiode arrays. The resulting microstructures are transparent in the spectrum of interest and hence serve as optical windows towards the substrate. Furthermore, our results show that the high aspect ratio (5:1) micro structure windows can be achieved and protected using FAM-technology. The optical through package windows are accurately defined (±5 μm accuracy due to mask limitations) and can significantly improve the throughput. The total process time of a single wafer with up to 1260 chips and 20160 windows, including lamination, exposure and development, would approximately take 1-1.5 hours., Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Electronic Components, Technology and Materials

This work describes the design, modelling and realisation of the mechanical part of a non-linear MEMS accelerometer intended for large displacement behaviour. For this, a mass/spring system was designed with an extremely low resonance frequency. In this work the mechanical behaviour was verified by measurements done using an optical setup, including a laser and photodiode. The results are a resonance frequency of 12.6 Hz, which can be further tuned depending on the application by varying the mass, beam thickness and tilt of the structure. This results in a mechanical sensitivity of 0.16 [mm/ms-2]. The future goal of this work is to integrate a read-out scheme on wafer level, for example electrostatically., Accepted author manuscript, Electronic Components, Technology and Materials, Else Kooi Laboratory, EKL Processing

The mechanical part of inertial sensors can be designed to have a large mechanical sensitivity, but also requires the transduction mechanism which translates this displacement. The overall system resolution in mechanical inertial sensors is dictated by the noise contribution of each stage and the magnitude of each sensitivity, see also Figure 1. Maximizing the capacitive sensitivity, results in suppression of noise in the electronics domain. This work focuses on the design and realization of a mechanical to electrical transduction using a capacitive readout scheme. Design considerations and measures are taken to maximize the latter are considered and illustrated using FEM simulations. A capacitive transducer showing a sensitivity of 100 [aF/nm] was designed and realized, by exploiting the large displacement behavior of the inertial sensor which was considered., Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Electronic Components, Technology and Materials, EKL Processing

In this work a method is described to investigate process variations across a wafer. Through wafer MEMS spiral resonators were designed, simulated, fabricated and characterized by measuring the eigenfrequency and corresponding mode shapes. Measuring the eigenfrequency and resulting spectral behavior of resonators on different locations on the wafer was performed by using an optical measurement setup. Two laser beams were used where one is modulated by the periodic movement of the center mass of the resonator. One of the beams is reflected back from the modulated resonator and this beam hits a photo diode. Variations in light intensity due to movement of the resonator is providing a measurement signal correlated to movement. Preliminary measurements showed that measured eigenfrequencies are in correspondence with the simulations within a range of 0-10% deviation., Accepted author manuscript, Electronic Components, Technology and Materials

We explore a methodology for patterned copper nanoparticle paste for 3D interconnect applications in wafer to wafer (W2W) bonding. A novel fine pitch thermal compression bonding process (sintering) with coated copper nanoparticle paste was developed. Most of the particle size is between 10-30 nm. Lithographically defined stencil printing using photoresist and lift-off was used to apply and pattern the paste. Variations in sintering process parameters, such as: pressure, geometry and ambient atmosphere, were studied. Compared to Sn-Ag-Cu (SAC) microsolder bumps, we achieved better interconnect resistivity after sintering at 260 °C for 10 min, in a 700 mBar hydrogen forming gas (H2/N2) environment. The electrical resistivity was 7.84 ± 1.45 μΩ·cm, which is about 4.6 times that of bulk copper. In addition, metallic nanoparticle interconnect porosity can influence the electrical properties of the interconnect. Consequently, we investigated the porosity effect on conductivity using finite element simulation. A linear relationship between the equivalent conductivity and particle overlapping ratio was found., Accepted Author Manuscript, Electronic Components, Technology and Materials, EKL Processing