Influences of pretreatment and hard baking on the mechanical reliability of SU-8 microstructures

Abstract

In this paper, the influences of pretreatment and hard baking on the mechanical characteristics of SU-8 microstructures are described. Four types of samples with different combinations of O2 plasma ashing, primer coating and hard baking were prepared for shear strength tests and uniaxial tensile tests. Specially developed shear test equipment was used to experimentally measure the shear adhesion strength of SU-8 micro posts on a glass substrate. The adhesiveness was strengthened by hard baking at 200 °C for 60 min, whereas other pretreatment processes hardly affected the strength. The pretreatment and hard baking effects on the adhesive strength were compared with those on the fracture strength measured by uniaxial tensile testing. There were no influences of O2 plasma ashing on both the strengths, and primer coating affected only tensile strength. The primer coating effect as well as the hard baking effect on stress relaxation phenomena in uniaxial tension was observed as well. Fourier transform infrared spectroscopy demonstrated that surface degradation and epoxide-ring opening polymerization would have given rise to the primer coating effect and the hard baking effect on the mechanical characteristics, respectively.

Liquid immersion thermal crosslinking of 3D polymer nanopatterns for direct carbonisation with high structural integrity

“…This implies that some ether groups decomposed into the carbonyl group during the heat treatment 18 . The polymer crosslinking could also be directly proven by the enhancement of mechanical strength 25 . The elastic modulus and the hardness of the SU8 nanopatterns were measured via nanoindentation, as shown in Figure S4 .…”

Ultrahigh Elastic Strain Energy Storage in Metal-Oxide-Infiltrated Patterned Hybrid Polymer Nanocomposites

“…This new nanocomposite method has proven useful for enhancing various physical and chemical properties of polymers, − including mechanical strength. , We applied the infiltration synthesis of aluminum oxide (AlO x ) to polymer nanopillars lithographically patterned from a commercial epoxy-based resist SU-8 . Designed for negative-tone (i.e., cross-linkable) lithographic patterning and being one of the strongest polymeric materials (σ y ∼ 60 MPa) with moderate E (∼2–4 GPa), , SU-8 is the primary polymer system utilized extensively for MEMS/NEMS applications. , Thus, our nanopillar was made using conventional MEMS fabrication techniques and its dimension and material properties are similar to those of typical MEMS SU-8 components.…”

SU-8 for Microsystem Fabrication

“…With the coating of the adhesive promoter, which is 100 wt% hexamethyldisilazane (Tokyo Ohka Kogyo Co., Ltd; OAP) and enables the reduction of the SU-8 polymer chains breakage, SU-8 would exhibit higher yield strength and higher tensile strength in primer-coated tensile specimens. 4 Wouters and Puers found that the SU-8 epoxy will swell on being immersed in a solution because of the absorption or desorption of water to result in the volume change, or alternatively a change in built-in stress. 5 In addition, experimental results showed the built-in stress of SU-8 reached its maximum value when submersed in propylene glycol methyl ether acetate and in isopropyl alcohol and the stress will be strongly correlated with the formation of cracks and delamination in SU-8.…”