Bond mechanisms and bond strengths of solvent-welded polymethylmethacrylate sheets for use as deep x-ray resist in LIGA-type processing.

摘要

The bonding properties of solvent-welded polymethylmethacrylate, PMMA, for use as a deep X-ray resist in LIGA-type processing, have been examined. A technique which bonds pre-cut PMMA sheets to a variety of planar substrates has been developed. Use of this technique to prepare thick X-ray sensitive layers has shown to be a great improvement to casting. The adhesion mechanism and the resulting material changes which occur due to the bonding process have been investigated. In this dissertation, bond strength, as dependent upon substrate material and solvent employed during bonding, was evaluated through the use of an asymmetric double-cantilever beam test. Information pertaining to solvent solubility parameter and acid-base nature, as well as the acid-base nature of the substrate, was correlated to the adhesion mechanism and the thickness of the solvent affected zone.; The solvents investigated in this work were: dimethylformamide, tetrahydrofuran, methylmethacrylate, dichloromethane, chloroform, and chlorobenzene. The substrate materials bonded to include glass, sputtered chromium, sputtered titanium, and sputtered gold. The effect, and necessity, of the spun-on layer of PMMA was also investigated.; When a spun-on layer of PMMA was used to coat the substrate prior to bonding, the calculated fracture energy varied from 6.6 J/m{dollar}sp2{dollar} for a glass substrate, using dimethylformamide as the bonding solvent, to 360 J/m{dollar}sp2{dollar} for a chromium substrate, using chloroform as the bonding solvent. When no spun-on layer was employed, the calculated fracture energy ranged from 0.95 J/m{dollar}sp2{dollar} for a chromium substrate, using dimethylformamide as the bonding solvent, to 92 J/m{dollar}sp2{dollar} for a glass substrate, using chlorobenzene as the bonding solvent.; It was apparent that acid-base interactions play a critical role in the adhesion of resists to their substrate. For the process of solvent bonding thick PMMA resist to a substrate, not only were the acid-base properties of the PMMA and substrate important, but also the acidic or alkaline nature of the solvent. The acid-base properties of the solvent became less significant when a spun-on layer was employed.