Lightfield Directing Array Qualified Packaging Development (LDAQPD)

The aerospace-compatible packaging will improve the precision and stability of the (Lightfield Directing Array) LDA unit in several ways: i) reduce unit size so the sensors are closer to the actuators thus improving closed-loop control performance and reducing power demand, ii) closely match the packaging to the coefficient of thermal expansion between the MEMS and the package material so that the optical surface will remain stable across the range of expected operating temperatures and iii) improve thermal management of the full package through improved thermal conductivity and heat removal.  Lastly the proposed effort will create a technologically advanced manufacturing capability within domestic supply chains.The team will work with Draper to explore state-of-the-art 3D Heterogeneous Integration (3DHI) packaging techniques to create a co-packaged solution consisting of the MEMS actuator, silicon interposer layers, and ASICs.  This effort will leverage several key areas of expertise at Draper:  high routing layer density, via formation technology and through-substrate vias (TSV), and precision aligned component bonding and electrical interface formation.  This will result in a thermal and ambient pressure-stable [JZ1] package design that allows the ASICs necessary to control and drive the MEMS device to be accommodated in a footprint only slightly larger than the optical aperture.  This further improves the SWaP of the LDA and makes it possible to closely tile apertures when the application demands – e.g., OCS systems with high optical channel counts.This project will push beyond the present packaging state-of-the-art in multiple areas: i) creation of a dense array of interconnect traces (>2,400 traces in a 4cm2 area); ii) fully shielding these traces from capacitive cross-talk through the use of grounded isolation layers; iii) the capability to sustain voltages up to 250V for all traces; iv) the development of a design and aligned bonding process to allow Drive/Sense ASICs to be distributed over multiple layers of the 3DHI interposer structure; and v) the ability to integrate the ASICs into this multi-layer structure.  The project will use packaging component test structures to reduce risk by developing assembly process steps and demonstrating their functional performance. The principal challenge is expected to be found at the intersection of increased routing density and 3D packaging (multiple layers). The aerospace package prototypes will be tested for functionality limits to improve LDA precision and stability in future defense aerospace applications.  The aerospace package prototypes will also be an important milestone for future work in creating tile-able aerospace packages for large (>4cm2) apertures required for future defense applications.