LIGA is a German acronym for Lithographie, Galvanoformung, Abformung (Lithography, Electroplating, and Moulding) that describes a fabrication technology used to create high-aspect-ratio (HAR) microstructures. UV LIGA utilizes an inexpensive ultraviolet light source, like a Hg lamp, to expose a polymer photoresist, typically SU-8 or PMMA. Because heating and transmittance are not an issue in optical masks, a simple Cr mask can be substituted for the technically sophisticated X-ray mask. These reductions in complexity make UV LIGA much less expensive and more accessible than its X-ray counterpart. However, UV LIGA is not as effective at producing precision molds and is thus used when cost must be kept low and very high aspect ratios are not required.

SU-8: Benefits/Attributes

  • High aspect ratio imaging
  • Excellent chemical & temperature resistance
  • Coatings to hundreds of microns

SU-8 Microgear
B. Loechel, et. al., Abstracts HARMST 2003, 55 (2003)

50µm x 2.5mm SU-8 LIGA gear mold.
Courtesy of ZG Ling, CAMD, Louisiana State Univ. (2003)

Source: Univ. of Alabama, Huntsville
The LIGA-fabrication process is composed of
(a) exposure
(b) development
(c) electroforming
(d) stripping and
(e) replication