Ultra thick epoxy-based dry-film resist for high aspect ratios

This work presents a new type of high-resolution dry-film resist laminates for the fabrication of extremely thick epoxy based polymer structures. Via a lamination process a resist thickness of up to d = 360 μm can be applied by one single process step. Afterwards, the dry-film resist is patterned by standard UV-lithography. An epoxy based resist mixture which contains epoxy resins, reactive diluents, additives, and a photo acid generator is deposited onto a PET supporting film by doctor blading for fabrication of the resist film. The films can be cut defect-free into favoured sheet sizes. Currently, dry-film resists with a layer thickness of up to 400 μm can be produced reproducible. With the tested d = 360 μm thick dry-film resist an aspect ratio of 15:1 (height:width) has been achieved. By lamination and UV-patterning of two layers resist a master for 700 μm thick electroplated Nickel structures was fabricated. Thereby, steep side walls with an angle deviation of α < 1° have been generated.

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► We present a new epoxy based dry-film photoresist for lamination and UV-patterning.
► A layer thickness of up to d = 400 μm can be achieved by one single lamination step.
► The resist features an achievable aspect ratio of more than 15.
► Steep 700 μm high side walls with an angle deviation of α < 1° have been realized.
► Several centimetre large-scaled structures have been fabricated without any cracks.