Abstract
This paper reports on fabrication technologies for package parts of Josephson chips, and the mechanical & electrical characteristics of model packaging system measured in liquid helium. Solder bonding technology is applied to connect the pinned substrate & chip mounted substrate, and it has become possible to line up and connect the substrates pattern pitches as fine as 100 μm. In order to connect I/O cable and patterned substrate, a flat cable is applied, and Cu ball bonding technology is developed. By pressing the cable onto the Cu balls which are solder bonded on the patterned substrate, a stable connection can be obtained in liquid helium. Using these packaging parts, a model packaging system is constructed on a molybdenum holder. The mechanical & electrical characteristics are evaluated on the system. The results are as follows : The system operated successfully in liquid helium, and series connection was possible. The model system showed the stable connection in heat cycles. The DC resistance of the fillets, micro-connectors, and flat cable connectors measured in liquid helium was sufficiently small for practical use. Through these development, high-density packaging technologies are developed, and a model packaging system for Josephson chips can be realized.
