A Submillimeter Package for Microsystems in High-Pressure and High-Salinity Downhole Environments

This paper describes a submillimeter-scale package intended for microsystem components in high-pressure and high-salinity environments, such as downhole environments in oil wells. The outer dimensions of the package are 0.8
$\times 0.8 \times $
0.8
$\mathrm{mm}^{3}$
, whereas the interior cavity is 0.4
$\times 0.4 \times 0.45~\mathrm{mm}^{3}$
. The package consists of a stainless steel 17–4 PH metal can and a borosilicate glass lid, and is hermetically sealed by an Au–In bond. The measured bond strength is
$\approx 13$
MPa. A component integration strategy is demonstrated: test silicon chips are assembled into a stack using a folded flexible polyimide cable that provides electrical interconnections among the chips. The packages coated with thin-film alumina by atomic layer deposition and Parylene-C survive >48 h in the American Petroleum Institute standard brine (with 8 wt% NaCl and 2 wt% CaCl
₂
in deionized water) at 80 °C, and subsequently, in 50-MPa (
$\approx 7250$
psi) hydraulic pressure. [2014-0108]