We have derived a gas ingress and egress equation from the first principles of ideal gases. This work is intended to benefit the hermetic microelectronics packaging community, but it may be applied to other fields that require a deep understanding of gas ingress and egress dynamics. The equation outlined herein encompasses package material properties, package characteristics, hermetic testing conditions, and service conditions. It serves as a practical utility for calculating package pressure changes due to gas ingress and egress and, therefore, a power tool for component and system service life predictions.
In this paper, a closed-form mathematic equation that governs gas ingression of hermetic packages is derived from first principles and applied to moist air and water vapor ingression conditions. The equation models internal gas partial pressure change as a function of time, external conditions, and package characteristics. The equation provides the theoretical basis for direct comparisons of ingression behaviors of different gases into hermetic packages. Comparing the rates of internal air pressure increase due to air ingression and water vapor partial pressure buildup due to water vapor ingression, the authors theorize that vacuum decay may present a greater challenge to the performance of microelectromechanical systems (MEMS) devices within hermetic packages than that of water vapor content induced corrosion failures. This paper also examines gas ingression of hermetic enclosures with multiple layers of seals.
With the next generation of semiconductor materials in development, significant strides in the Size, Weight, and Power (SWaP) characteristics of power conversion systems are presently underway. In particular, much of the improvements in system-level efficiencies and power densities due to wide-bandgap (WBG) and ultra-wide-bandgap (UWBG) device incorporation are realized through higher voltage, higher frequency, and higher temperature operation. Concomitantly, there is a demand for ever smaller device footprints with high voltage, high power handling ability while maintaining ultra-low inductive/capacitive parasitics for high frequency operation. For our work, we are developing small size vertical gallium nitride (GaN) and aluminum gallium nitride (AlGaN) power diodes and transistors with breakdown and hold-off voltages as high as 15kV. The small size and high power densities of these devices create stringent requirements on both the size (balanced between larger sizing for increased voltage hold-off with smaller sizing for reduced parasitics) and heat dissipation capabilities of the associated packaging. To accommodate these requirements and to be able to characterize these novel device designs, we have developed specialized packages as well as test hardware and capabilities. This work describes the requirements of these new devices, the development of the high voltage, high power packages, and the high-voltage, high-Temperature test capabilities needed to characterize and use the completed components. In the course of this work, we have settled on a multi-step methodology for assessing the performance of these new power devices, which we also present.
The Icarus camera is an improvement on past imagers (Furi and Hippogriff) designed for the Ultra-Fast X-ray Imager (UXI) program to deliver ultra-fast, time-gated, multi-frame image sets for High Energy Density Physics (HEDP) experiments. Icarus is a 1024 × 512 pixel array with 25 μm spatial resolution containing 4 frames of storage per pixel. It has improved timing generation and distribution components and has achieved 2 ns time gating. Design improvements and initial characterization and performance results will be discussed. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525.
We report on the progress made to date for a Laboratory Directed Research and Development (LDRD) project aimed at diagnosing magnetic flux compression on the Z pulsed-power accelerator (0-20 MA in 100 ns). Each experiment consisted of an initially solid Be or Al liner (cylindrical tube), which was imploded using the Z accelerator's drive current (0-20 MA in 100 ns). The imploding liner compresses a 10-T axial seed field, B z ( 0 ) , supplied by an independently driven Helmholtz coil pair. Assuming perfect flux conservation, the axial field amplification should be well described by B z ( t ) = B z ( 0 ) x [ R ( 0 ) / R ( t )] 2 , where R is the liner's inner surface radius. With perfect flux conservation, B z ( t ) and dB z / dt values exceeding 10 4 T and 10 12 T/s, respectively, are expected. These large values, the diminishing liner volume, and the harsh environment on Z, make it particularly challenging to measure these fields. We report on our latest efforts to do so using three primary techniques: (1) micro B-dot probes to measure the fringe fields associated with flux compression, (2) streaked visible Zeeman absorption spectroscopy, and (3) fiber-based Faraday rotation. We also mention two new techniques that make use of the neutron diagnostics suite on Z. These techniques were not developed under this LDRD, but they could influence how we prioritize our efforts to diagnose magnetic flux compression on Z in the future. The first technique is based on the yield ratio of secondary DT to primary DD reactions. The second technique makes use of the secondary DT neutron time-of-flight energy spectra. Both of these techniques have been used successfully to infer the degree of magnetization at stagnation in fully integrated Magnetized Liner Inertial Fusion (MagLIF) experiments on Z [P. F. Schmit et al. , Phys. Rev. Lett. 113 , 155004 (2014); P. F. Knapp et al. , Phys. Plasmas, 22 , 056312 (2015)]. Finally, we present some recent developments for designing and fabricating novel micro B-dot probes to measure B z ( t ) inside of an imploding liner. In one approach, the micro B-dot loops were fabricated on a printed circuit board (PCB). The PCB was then soldered to off-the-shelf 0.020- inch-diameter semi-rigid coaxial cables, which were terminated with standard SMA connectors. These probes were recently tested using the COBRA pulsed power generator (0-1 MA in 100 ns) at Cornell University. In another approach, we are planning to use new multi-material 3D printing capabilities to fabricate novel micro B-dot packages. In the near future, we plan to 3D print these probes and then test them on the COBRA generator. With successful operation demonstrated at 1-MA, we will then make plans to use these probes on a 20-MA Z experiment.
The Ultra-Fast X-ray Imager (UXI) program is an ongoing effort at Sandia National Laboratories to create high speed, multi-frame, time gated Read Out Integrated Circuits (ROICs), and a corresponding suite of photodetectors to image a wide variety of High Energy Density (HED) physics experiments on both Sandia's Z-Machine and the National Ignition Facility (NIF). The program is currently fielding a 1024 x 448 prototype camera with 25 μm pixel spatial resolution, 2 frames of in-pixel storage and the possibility of exchanging spatial resolution to achieve 4 or 8 frames of storage. The camera's minimum integration time is 2 ns. Minimum signal target is 1500 e-rms and full well is 1.5 million e-. The design and initial characterization results will be presented as well as a description of future imagers.
Microsystems packaging involves physically placing and electrically interconnecting a microelectronic device in a package that protects it from and interfaces it with the outside world. When the device requires a hermetic or controlled microenvironment, it is typically sealed within a cavity in the package. Sealing involves placing and attaching a lid, typically by welding, brazing, or soldering. Materials selection (e.g., the epoxy die attach), and process control (e.g., the epoxy curing temperature and time) are critical for reproducible and reliable microsystems packaging. This paper will review some hermetic and controlled microenvironment packaging at Sandia Labs, and will discuss materials, processes, and equipment used to package environmentally sensitive microelectronics (e.g., MEMS and sensors).