Morphology adjustable microlens array fabricated by single spatially modulated femtosecond pulse

Silica microlens arrays (MLAs) with multiple numerical-apertures (NAs) have high thermal and mechanical stability, and have potential application prospects in 3D display and rapid detection. However, it is still a challenge to rapidly fabricate silica MLAs with a larger range of NAs and how to obtain multiple NAs in the same aperture diameter. Here, a wet etching assisted spatially modulated femtosecond laser pulse fabricating technology is proposed. In this technology, Gaussian laser pulse is modulated in the axial direction to create a pulse with a large aspect ratio, which is used to modify the silica to obtain a longer modification distance than traditional technology. After that, a microlens with a larger NA can be obtained by etching, and the NA variable range can be up to 0.06–0.65, and even under the same aperture, the variable NA can range up to 0.45–0.65. In addition, a single focus is radially modulated into several focus with different axial lengths to achieve a single exposure fabricating of MLA with multiple NAs. In characterization of the image under a microscope, the multi-plane imaging characteristics of the MLA are revealed. The proposed technology offers great potential toward numerous applications, including microfluidic adaptive imaging and biomedical sensing.

High Density RDL Technologies for Panel Level Packaging of Embedded Dies

The ongoing miniaturization and functional heterogeneity in electronics packaging are pushing the demand for advanced substrate technologies. Highly integrated, advanced multi-chip packaging solutions combine application, logic and computing dies with memory or components for power management in a single package. A solution to achieve low fabrication costs is the close embedding of thin dies in IC Substrates based on large formats (600 x 600 mm²), known from PCB fabrication. In a consortium of partners from industry and research advanced technologies for Panel Level Packaging (PLP) are developed. This paper will show the development of 5µm L/S RDL routing density and chips with 50µm bump pitch. Here, the 6x6 mm² dies are symmetrically embedded into an organic laminate matrix. A PCB core (100µm thickness) with very low coefficient of thermal expansion (CTE) containing laser cut cavities is used, acting as a frame layer. Besides mechanical and handling stability, the usage of such a frame offers the advantage of pre-integrating additional features like local fiducials, through vias or power lines by conventional PCB processes. Within that frame, the dies are embedded by lamination of an organic build-up film with 25µm thickness equal to bump height. The chip contacts are then opened without the need of any micro via formation. Here a strong focus is set on RIE etching of the polymer material. Highly accurate measurement of the real die position is essential for the following processing. The formation of the redistribution layer (RDL) is done in a semi-additive process (SAP) utilizing sputtering technique and direct imaging (LDI). To achieve the fine pitch demands, an adaptive imaging process is applied. Therefore, a newly developed LDI machine is used to write structures in a 7µm photoresist. This exposure also combines the measurement data of the real die position and the adaption of the exposure artwork, in order to achieve highest registration quality.

Learned adaptive multiphoton illumination microscopy for large-scale immune response imaging

Multiphoton microscopy is a powerful technique for deep in vivo imaging in scattering samples. However, it requires precise, sample-dependent increases in excitation power with depth in order to generate contrast in scattering tissue, while minimizing photobleaching and phototoxicity. We show here how adaptive imaging can optimize illumination power at each point in a 3D volume as a function of the sample’s shape, without the need for specialized fluorescent labeling. Our method relies on training a physics-based machine learning model using cells with identical fluorescent labels imaged in situ. We use this technique for in vivo imaging of immune responses in mouse lymph nodes following vaccination. We achieve visualization of physiologically realistic numbers of antigen-specific T cells (~2 orders of magnitude lower than previous studies), and demonstrate changes in the global organization and motility of dendritic cell networks during the early stages of the immune response. We provide a step-by-step tutorial for implementing this technique using exclusively open-source hardware and software.