Compact Magnetic Shielding Using Thick-Film Electroplated Permalloy

Speaker: Jimmy Wu
Affiliation: Ph.D. Candidate

Abstract: Compact integration of clocks and inertial sensors using atomic, molecular, and optical (AMO) technology is necessary to create a self-contained navigation system resistant to external interference. However, the trend in miniaturization of AMO systems places the magnetic field of particle traps, optical isolators, and vacuum pumps close to other system components. Stray fields and field fluctuations cause changes in atomic transition frequencies, raising the noise floor and reducing valuable stability in these precision devices. Therefore, it is critical to shield these magnetic fields away from sensitive subsystems by shunting them through low reluctance paths. This is accomplished with high permeability magnetic materials which either surround the precision components or the source of the magnetic field itself. Current magnetic shields are conventionally machined single or multi-layer structures made of various iron alloys. At smaller size scales, these methods are ineffective at accommodating the various device and interconnect shapes, making multi-system integration challenging.

This work demonstrates batch fabricated high permeability magnetic shielding using permalloy electroplating techniques to simultaneously push the limits of minimum size, maximum shielding factor, and cost. In particular, it presents the first experimental demonstration of electrodeposited high permeability, compact magnetic shielding at millimeter and sub- millimeter scales of fields exceeding 15 mT. Single layer shields of 300 µm permalloy with inner dimensions varying from 3 mm to 6.5 mm were fabricated on 3D printed polymer molds using a novel double-anode plating process to enable conformal deposition. Multilayer shields of 10 µm permalloy and copper layers with inner dimensions of 1.5 mm to 6 mm were microfabricated using a bulk micromachining technique. The electroplated shields were designed with thicknesses to avoid saturation at the appropriate fields and shapes to allow sophisticated interconnect extraction – a task that is challenging for conventional machining yet simple for microfabrication and electroplating. The size and shielding factor of these structures can enable compact integration of magnetic devices for AMO microsystems and other magnetic microelectronics, such as magnetic random-access memory and haptic actuators.

Biography: Jimmy Wu is currently a PhD candidate in the Electrical & Computer Engineering Department at the University of California, Los Angeles under Prof. Rob Candler. He received his B.S. in Electrical Engineering and Computer Sciences at the University of California, Berkeley where he completed the Honors Program with an elective in Physics in 2013. He received his M.S. in Electrical & Computer Engineering from UCLA in 2015. His current research interests include the applications of thick- film batch fabricated magnetic materials at size scales where conventional and micromachining techniques intersect. These include miniaturized electromagnets for particle beam focusing and steering to develop room-scale free electron lasers and compact multilayer magnetic shielding for atomic, optical, and molecular systems to realize chip-scale atomic clocks. He was a finalist for the Henry Samueli Excellence in Teaching Award in 2019.

For more information, contact Prof. Robert Candler (rcandler@ee.ucla.edu)

Date/Time:
Date(s) - Mar 09, 2020
9:00 am - 10:30 am

Location:
Boelter Hall – Room 7702
580 Portola Plaza, Los Angeles 90095