Photoresists & Specialty Chemicals
LIGA
Part of the Applications Notes Line
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 |
 50µm x 2.5mm SU-8 LIGA gear mold. |
 Source: Univ. of Alabama, Huntsville |
The LIGA-fabrication process is composed of
(a) exposure
(b) development
(c) electroforming
(d) stripping and
(e) replication