Abstract
Fabrication technologies for micro-sockets used in the packaging of Josephson chips are reported. Packaging technologies for Josephson chips are required to satisfy the conditions of high package density, and usability at low temperature and heat cycles. For this purpose, specially designed micro-sockets fabricated on Si substrate with tapered cavities containing mercury drops are studied. Photolithographic and anisotropic etching techniques using a KOH solution are applied to form the tapered socket cavities in the substrate. These techniques make possible batch fabrication as well as obtaining of precise socket pitch and aperture width. In order to fill the socket cavities with very small mercury drops, an automatic injection apparatus is developed, which takes advantage of mercury's good stickness with SiO2 surface. Precisely uniform mercury drops can be injected by transferring the pressed and appeared mercury drop on the glass tube top into the substrate cavities. Fabrication technologies for the micro-sockets used in high package density (pitch 300 μm) with precise mercury drop size (diameter 210± 10 μm) can be realized.
