What is billed as the first micromanufacturing technology to allow fabrication of 1-mm-tall and taller 3D microsystems has been developed by Microfabrica Inc., Burbank, Calif. (www.microfabrica.com). The firm says its EFAB process can produce complex 3D designs for numerous miniature metal parts in military, medical and consumer electronics applications.
Other micromanufacturing technologies, such as LIGA (lithographic, galvanoformung, and abformung), can produce only single-layer extruded shapes. In LIGA, X-ray lithography generates the tall primary microstructures. Electroforming (galvanoformung) produces microstructures in metal on the basic geometry. Then molding (abformung) produces secondary microstructures in polymers, metals, or ceramics.
In contrast, EFAB technology is an additive microfabrication process based on multilayer selective electrodeposition of metals. It is analogous to stereolithographic processes used in rapid prototyping. EFAB rapidly stacks large numbers of independently patterned metal layers on top of each other to create geometries with micron-level precision.
Each layer is generated in three basic steps. First a layer of sacrificial metal is deposited in a pattern corresponding to a cross section of the device to be fabricated. A second material is electroplated onto the substrate, covering the previous layer completely. Finally, in the third step, the two materials are planarized to yield a single two-material layer.
To continue building the device, the same process repeats until all cross sections of the design have been constructed. Once all layers have formed, a release etchant removes the sacrificial material, leaving behind the freestanding final device.
The basic EFAB process uses just one structural and one sacrificial material. But in practice, multiple sacrificial and structural materials can serve to create complex multimaterial devices.
Examples of applications that can take advantage of tall 3D microstructures include critical components in the military such as the safing and arming mechanisms which prevent unintended functioning of ammunition. Unlike extrusion-based techniques, say Microfabrica officials, the EFAB process can build these concurrently and monolithically, eliminating the need for manual assembly.