Characterization of Metallized Plastic MEMS
- PDF / 2,985,319 Bytes
- 6 Pages / 411.12 x 635.4 pts Page_size
- 29 Downloads / 239 Views
Figure 1: Capillary electrophoresis chip made from gold, silicone and polystyrene.
97 Mat. Res. Soc. Symp. Proc. Vol. 605 © 2000 Materials Research Society
Various methods exist for depositing metals on plastic, including electroplating, sputtering and vacuum evaporation [3]. Electroplating requires that the surface be primed to make ready for the plating bath. Priming includes the application of both sensitizers and activators-usually these are both in the form of wet chemistry. In some cases, the procedure is to treat the plastic surface with plasma (sensitizer), then treat with a palladium solution (activator) [6]. Short wavelength UV can also be used-the method has been used to pattern thin lines in polyester [7]. Roughening, which is often used for decorative plating, can be used to increase adhesion. The roughening is often at the level of several microns-unsuitable for MEMS with features in the micron scale. Sputtering has been used successfully to plate plastic [3]. The sputtering process can also roughen the surface due to the energetic nature of a plasma discharge. Furthermore, sputtering often results in heating of the plastic. Vacuum evaporation can metallize a plastic surface, so long as the plastic exhibits reasonably low outgassing (i.e., has low volatile content and plasticizers). Such metallization can result in little or no change to the plastic surface, so that the material retains its original chemistry. EXPERIMENT
Deposition Vacuum evaporation was chosen as the method for deposition on plastic. Vacuum evaporation is a relatively simple procedure which can be used to apply a metallic coating to a variety of materials with little or no change to the surface chemistry. Several plastic substrates were used for a preliminary deposition study. These were acrylonitrile-butadiene-styrene (ABS), polycarbonate (PC), high-density polyethylene (HDPE), polyethylene terephthalate (PETG), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), and polyurethane (PU). The plastic surfaces were washed with soapy water, then DI rinsed and allowed to dry under 40 C air for 24 hours. An electron beam evaporator was used to evaporate gold at a pressure of 6x10 6 Torr. 2000 Angstroms of gold was deposited at 10 Angstroms/second. No "adhesion layer" was used. After deposition, a "tape test" was performed to test adhesion. In this test a piece of plastic tape is attached to the gold surface, then removed in a vertical pulling action. If gold is removed from the surface, the material is said to fail the tape test. Polycarbonate and polystyrene exhibited the best adhesion to gold, and these were used for subsequent experiments. Following this, films of polystyrene (10 mil) and polycarbonate (20 mil) were coated with 2kA of gold simultaneously.
Patterning Metal test lines were patterned on to the surface of the polystyrene and polycarbonate. Different test masks were generated, as shown in figure 2. The following method was used. First, a protective tape was attached to the backside of the samples to help pro
Data Loading...
