Eiji Horikoshi

Magnetic Properties and Ferromagnetic Shielding of Ni-Fe-Mo Alloys at Cryogenic Temperatures

Excellent magnetic shielding performance at 4.2 K is required for the superconducting quantum interference devices to avoid influences of electromagnetic noises. This could be provided by a ferromagnetic shield using high permeability material. For cryogenic uses, a quaternary alloy of Ni-Fe-Mo-Cu has already been proposed.l

High-Reliability Solder Connection for ZIF Connectors

A new type of zero insertion force (ZIF) connector is proposed. In this new connector, the contact pair consists of an input/ output (I/O) pin and solder. An appropriate amount of solder fills cavities formed in the connector housing, and the position of the cavities corresponds with that of the I/O pins attached to the large-scale integration (LSI) module. The I/O pins are inserted or withdrawn, while the solder is melted. The possibility of this type of connector was examined using In-48%Sn (percent symbol stands for mass percent) solder and three kinds of surface finishes for the I/O pins; Au/Ni, Pd/Ni, and Au (very thin top layer)/Pd/Ni films. The solder was filled in the cavities formed in a glass-ceramic substrate, and electrical resistance between the I/O pin and solder was measured. A combination of the In48%Sn solder and Au/Pd/Ni film exhibits low electrical resistance even after many insertion/withdrawal cycles, indicating that these materials have suitable characteristics for the new type ZIF connector. A connector model using these materials shows low electrical resistance, below 10 m \Omega after 50 insertion/withdrawal cycles. Experimental results indicate that the new type of connector has a high potential for use as a ZIF connector for future high-density pin grid array connections.