Introduction and Process Steps

Mechatronics 

LIGA Micro-manufacturing

Principle and Process Steps

Megh D 

Principle

LIGA Micro-machining is a manufacturing process implemented to manufacture micro-mechatronic components. LIGA is an abbreviation used for 3 processes, Lithographie, Galvanoformung, Abformung (Lithography, Electroplating, and Molding). 

LIGA is an additive manufacturing process, used to make molds or directly the end product. Surface or Bulk machining are also micro-machining processes.

Steps

Following are the steps involved in LIGA machining...

Step 1: Substrate

This is the base layer in the LIGA micro-manufacturing process. A Silicon wafer or a polished disk of beryllium, copper, titanium or other similar metal can be used.

The substrate needs to conduct electricity. If not already conductive a thin layer of conductive material is applied.

Step 2: Application of PMMA

Poly(methyl metacrylate) — PMMA also known as Plexiglass is the second layer in the LIGA micro-manufacturing process. 

Step 3: Lithography Mask

A mask is used to let only the shape of the product needed to be exposed. This generally is formed of 2 layers. One layer is transparent to X-ray or UV rays (depending on the process) and other is the absorber material.

Step 4: Expose

PMMA layer is exposed to X-ray or UV rays (depending on the process) for development. Here the mask acts as the template for development. 

Step 5: Development

The PMMA layer gets etched due to the exposure to X-ray or UV rays (depending on the process) and forms high aspect ratio molds, cavities or trenches like for the electroforming process. This is known as the development of the mold.

Step 6: Electroforming

Electroforming is an additive manufacturing process used for very high precision metal parts. Excess material is allowed to deposit to fill all spaces. This process is very similar to electroplating.

Step 7: Chemical Mechanical Polishing

Finishing processes like scrubbing/polishing are used to remove excess material deposition on the PMMA surface.  Some chemicals aiding in polishing and dissolving the excess material. 

Step 8: PMMA Removal

After removing the excess material, the PMMA is removed from the base substrate layer. After removal of the PMMA layer, the finished product remains on the base plate. 

Step 9: Release

The finished part or mold is then removed from the substrate base plate.