The Contribution to Residual Stress by Differential Resin Shrinkage

Motahhari, Siamak; Cameron, John H.

doi:10.1177/073168449901801104

Cited by 12 publications

(7 citation statements)

References 6 publications

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“…Apparently, shrinkage due to solvent evaporation and contraction due to differences in the thermal properties are more important than shrinkage due to polymerization. Other authors have shown that dimensional change during cross-linking is minimal for epoxy resins and might be neglected in the discussion of the bending [33].…”

Section: Influence Of Post-exposure Bake Temperaturementioning

confidence: 99%

Fabrication of thin SU-8 cantilevers: initial bending, release and time stability

Keller

Haefliger

Boisen

2010

J. Micromech. Microeng.

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SU-8 cantilevers with a thickness of 2 μm were fabricated using a dry release method and two steps of SU-8 photolithography. The processing of the thin SU-8 film defining the cantilevers was experimentally optimized to achieve low initial bending due to residual stress gradients. In parallel, the rotational deformation at the clamping point allowed a qualitative assessment of the device release from the fluorocarbon-coated substrate. The change of these parameters during several months of storage at ambient temperature was investigated in detail. The introduction of a long hard bake in an oven after development of the thin SU-8 film resulted in reduced cantilever bending due to removal of residual stress gradients. Further, improved time-stability of the devices was achieved due to the enhanced cross-linking of the polymer. A post-exposure bake at a temperature T PEB = 50 • C followed by a hard bake at T HB = 90 • C proved to be optimal to ensure low cantilever bending and low rotational deformation due to excellent device release and low change of these properties with time. With the optimized process, the reproducible fabrication of arrays with 2 μm thick cantilevers with a length of 500 μm and an initial bending of less than 20 μm was possible. The theoretical spring constant of these cantilevers is k = 4.8 ± 2.5 mN m −1 , which is comparable to the value for Si cantilevers with identical dimensions and a thickness of 500 nm.

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Section: Influence Of Post-exposure Bake Temperaturementioning

confidence: 99%

Fabrication of thin SU-8 cantilevers: initial bending, release and time stability

Keller

Haefliger

Boisen

2010

J. Micromech. Microeng.

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“…Excellent control of the curing process is required for production of a composite part with required shape and properties. For an accurate simulation of the curing process, exact knowledge of cure-dependent polymer properties and heat transfer is needed [1][2][3][4]. Development of matrix properties, chemical shrinkage and thermal conductivity are strongly coupled with the degree of cure.…”

Section: Introductionmentioning

confidence: 99%

Characterization of the cure shrinkage, reaction kinetics, bulk modulus and thermal conductivity of thermoset resin from a single experiment

et al. 2012

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International audienceThe use of thermoset composites has increased remarkably during the recent past in naval, automobile and aeronautical applications. Despite superior mechanical behaviour, certain problems, e.g. shape distortion, fibre buckling and matrix cracking, are induced in composite part, especially during fabrication due to the heterogeneous nature of such materials. Excellent control of the curing process is required for production of a composite part with required shape and properties. For an accurate simulation of the curing process, exact knowledge of cure-dependent polymer properties and heat transfer is needed. Several instruments are required to identify these parameters, which is time consuming, and costly. In the present study, results on the simultaneous characterization of bulk modulus, chemical shrinkage and degree of cure of vinylester resin using PVT-alpha device are presented. Determination of cure and temperature-dependent thermal conductivity of the matrix using the same device is also discussed. The obtained results are compared with the available literature results

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“…Particularly during the first minutes of the PEB, the cross-linking of epoxy resist leads to densification. Further, there is a loss of mass due to solvent evaporation [19]. The shrinkage due to polymerization and solvent evaporation results in tensile intrinsic stress.…”

Section: Introductionmentioning

confidence: 99%

Processing of thin SU-8 films

Keller¹,

Blagoi

Lillemose

et al. 2008

J. Micromech. Microeng.

150

132

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This paper summarizes the results of the process optimization for SU-8 films with thicknesses 5 μm. The influence of soft-bake conditions, exposure dose and post-exposure-bake parameters on residual film stress, structural stability and lithographic resolution was investigated. Conventionally, the SU-8 is soft-baked after spin coating to remove the solvent. After the exposure, a post-exposure bake at a high temperature T PEB 90 • C is required to cross-link the resist. However, for thin SU-8 films this often results in cracking or delamination due to residual film stress. The approach of the process optimization is to keep a considerable amount of the solvent in the SU-8 before exposure to facilitate photo-acid diffusion and to increase the mobility of the monomers. The experiments demonstrate that a replacement of the soft-bake by a short solvent evaporation time at ambient temperature allows cross-linking of the thin SU-8 films even at a low T PEB = 50 • C. Fourier-transform infrared spectroscopy is used to confirm the increased cross-linking density. The low thermal stress due to the reduced T PEB and the improved structural stability result in crack-free structures and solve the issue of delamination. The knowledge of the influence of different processing parameters on the responses allows the design of optimized processes for thin SU-8 films depending on the specific application.

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The Contribution to Residual Stress by Differential Resin Shrinkage

Cited by 12 publications

References 6 publications

Fabrication of thin SU-8 cantilevers: initial bending, release and time stability

Fabrication of thin SU-8 cantilevers: initial bending, release and time stability

Characterization of the cure shrinkage, reaction kinetics, bulk modulus and thermal conductivity of thermoset resin from a single experiment

Processing of thin SU-8 films

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