Quantum Sensing
Cryogenic magnetic field measurement devices utilize Josephson junctions embedded within superconducting loops to detect magnetic flux quanta with extreme sensitivity. Operating a squid magnetometer allows non-destructive tracking of microscopic electric current variations inside multi-layer printed circuit board assemblies. This ultra-sensitive sensor detects magnetic flux density variations down to femtotesla levels, exposing minute current leakage channels and latent semiconductor defects.
The operational boundary of this instrument stops at magnetic flux levels exceeding its quantum locking range or at operating temperatures above the superconducting transition point of its sensing loop.
Magnetic Profiling
Superconducting loop circuits convert magnetic flux threading the loop into discrete voltage oscillations through quantum interference mechanisms. When scanning across energized circuit assemblies, a squid magnetometer records minute spatial magnetic anomalies produced by subsurface short circuits, open microvias, or current crowding in power distribution planes. Liquid helium or closed-cycle cryocoolers maintain the sensor at cryogenic temperatures near four kelvin, requiring vacuum insulated cryostat dewars with thin sapphire windows to separate the cold sensor from warm test samples.
Precision non-magnetic gantry tables step the sample beneath the cryostat window at millimeter standoff distances, capturing high-resolution two-dimensional magnetic field maps. Back-projection inversion algorithms process these field maps to pinpoint buried current faults with sub-millimeter spatial accuracy.
Cryogenic Requirement
Operational overhead associated with liquid helium cooling restricts this technology primarily to high-value failure analysis laboratories. Magnetic shielding rooms isolate the unshielded sensor from Earth’s magnetic field and environmental electromagnetic noise. Non-destructive failure isolation capabilities justify setup complexity when diagnosing complex multi-layer board returns.
