MEMS Rotary Engine Power Systems Project Soft Magnetic

MEMS Rotary Engine Power Systems Project Soft Magnetic Pole Integration Debbie G. Jones Department of Mechanical Engineering dgjones@newton. berkeley. edu APP 4 8 BSAC © 2003 Fall IAB. Confidential Information. Not to be made public without permission from UC Regents.

Research Overview MEMS Rotary Engine Power Systems Project Objective – To electroplate soft magnetic material (nickeliron) into silicon mold of magnetic poles for the integrated generator design. Wankel Rotor D=2. 4 mm H=900 m Si Soft Magnetic Pole Requirements – Thick deposit, 900 microns Electric Power – High saturation Generator magnetization APP 4 – Good mechanical BSAC © 2003 Fall IAB. Confidential Information. Not to be made public without permission from 8 UC Regents. properties

Fabrication Process MEMS Rotary Engine Power Systems Project Si Mold Seed Layer Handle Wafer Si (900 m) Deep reactive ion etching (DRIE) of silicon mold Cr-Cu (6500 Å) Photoresist (2 m) Si (500 m) Photoresist (2 m) Deposition of chrome-copper (Cr-Cu) seed layer onto photoresist Bond Si mold to seed layer handle wafer Electroplated Ni. Fe Electroform nickel-iron (Ni. Fe) into Si mold Chemically release mold from seed layer with acetone Chemical mechanical polish (CMP) both sides of wafer APP 4 8 BSAC © 2003 Fall IAB. Confidential Information. Not to be made public without permission from UC Regents.

Electroplating MEMS Rotary Engine Power Systems Project Pump for Mass Transfer • Cell conditions (temperature, p. H, bath concentration, duty cycle & current density) affect Ni S-Rounds in Anode the deposition rate, Basket composition, and grain Anode (+) size Cathode (-) T=45 o. C p. H=6 Citrate-Complexed Nickel-Iron Electrolyte (H. V. Venkatasetty) APP 4 8 Wafer holder with insulating top plate Electroplatin g Bath 10 L Experimental Cell BSAC © 2003 Fall IAB. Confidential Information. Not to be made public without permission from UC Regents.

Results: Magnetic Properties MEMS Rotary Engine Power Systems Project Saturation magnetization of ~1. 5 Tesla attained APP 4 8 BSAC © 2003 Fall IAB. Confidential Information. Not to be made public without permission from UC Regents.

Results: Electroforming MEMS Rotary Engine Power Systems Project APP 4 8 SEM photograph of 500 μm thick silicon mold fabricated with DRIE SEM photograph of electroformed Ni. Fe in cleaved silicon mold. SEM photograph of electroformed Ni. Fe in silicon mold. Magnified photograph of Ni. Fe overgrowth in silicon mold. BSAC © 2003 Fall IAB. Confidential Information. Not to be made public without permission from UC Regents.