A partly lithographic method of fabrication is being developed to enable the economical mass production of mesoscale electrically conductive coils for miniature electro- magnets, solenoids, electric motors, and the like. This or a similar method is needed to overcome the limitations of prior techniques:

Coil Turns are formed lithographically, then stacked and bonded together to make coils.

  • The practical limit of fabricating miniature coils by conventional winding has been reached at a minimum wire width of ≈25 μm. At this limit, fabrication is a slow, expensive process that requires very skilled technicians.
  • Current techniques of microfabrication (e.g., those used to make microelectromechanical devices and integrated circuits) are limited to coils of no more than about 25 turns. This number of turns is insufficient for many anticipated applications in which hundreds of turns would be needed to generate sufficient magnetic flux.

In the present developmental method, thick-film optical lithography is used to generate a series of spiral patterns, and copper is plated into the patterns, thereby forming individual turns of a coil. Then the turns are freed, stacked, and bonded together with the turns electrically connected in series (see figure). It should be possible to make coils of hundreds of turns in very small packages. It should also be possible to scale coils down to sizes smaller than those achievable by conventional winding. This method is compatible with batch fabrication and is expected to cost much less than does fabrication of the smallest conventionally wound coils.

This work was done by Victor White, Juergen Mueller, and Dean Wiberg of Caltech for NASA’s Jet Propulsion Laboratory.


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Lithographic Fabrication of Mesoscale Electromagnet Coils

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This article first appeared in the July, 2002 issue of NASA Tech Briefs Magazine.

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