Compression studies on three-dimensional foam-like graphene and h-BN (3D-C and 3D-BN) revealed their high cross-plane thermal conductivity (62-86 W m K) and excellent surface conformity, characteristics essential for thermal management needs. Comparative studies to state-of-the-art materials and other materials currently under research for heat dissipation revealed 3D-foam's improved performance (20-30% improved cooling, temperature decrease by ΔT of 44-24 °C).

This paper presents a microassembly method for low-profile three-dimensional probe arrays for neural prosthesis and neuroscience applications. A silicon (Si) lead transfer structure, Si interposer, is employed to form electrical connections between two orthogonal planes-the two dimensional probes and the dummy application-specific integrated circuit (ASIC) chip. In order to hold the probe array and facilitate the alignment of probes during assembly, a Si platform is designed to have through-substrate slots for the insertion of probes and cavities for holding the Si interposers. The electrical interconnections between the probes and the dummy ASIC chip are formed by solder reflow, resulting in greatly improved throughput in the proposed assembly method. Moreover, since the backbone of the probe can be embedded inside the cavity of the Si platform, the profile of the probe array above the cortical surface can be controlled within 750 μm. This low-profile allows the probe array not to touch the skull after it is implanted on the brain. The impedance of the assembled probe is also measured and discussed.

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A modified thermoset polymer resin (PR) is evaluated as a form of alternative packaging material to traditional epoxy. It is understood that the thermoset cross-links to a higher degree at high temperature. Hence, its mechanical properties can be improved by changing treatment duration and temperature, rendering the material mechanically stronger for application temperatures beyond 300°C. Material strength was evaluated through a modified compressive testing setup which shows neat PR is comparable to epoxy. Concurrently, adhesion to silicon die and ceramic substrate were evaluated by means of bond shear using the DAGE-4000 shear tester both at room temperature and elevated temperature. Bond shear strength of PR is observed to be higher at room temperature as compared to elevated temperatures when bonded to Silicon (Si) and Alumina (Al2O3), a phenomenon which can be attributed to mismatches in coefficient of thermal expansions (CTE). For high pressure only applications, PR is a good alternative. Pre- and post-pressure loading analysis was carried out by forming an encapsulation analogous to that of a glob top on DIP packages. Observation shows no crack formation, indicating that the material is suitable for high pressure loading up to 207 MPa. For high pressure and high temperature applications (HPHT), pure PR is good up to 250°C at 25 kPsi (172 MPa).

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