Production Method of Millimeter-Wave Absorber with 3D-Printed Mold

TL;DR

This paper presents a novel production method for millimeter-wave absorbers using 3D-printed molds with a periodic pyramid shape, enabling easy prototyping and achieving low reflectance at 100 GHz.

Contribution

The study introduces a new manufacturing process utilizing transparent 3D-printed molds for millimeter-wave absorbers, facilitating shape variation and rapid prototyping.

Findings

Achieved approximately 1% reflectance at 100 GHz.

Demonstrated mechanical strength suitable for cryogenic conditions.

Validated the process with a test model immersed in liquid nitrogen.

Abstract

We established a production method of a good millimeter-wave absorber by using a 3D-printed mold. The mold has a periodic pyramid shape, and an absorptive material is filled into the mold. This shape reduces the surface reflection. The 3D-printed mold is made from a transparent material in the millimeter-wave range. Therefore, unmolding is not necessary. A significant benefit of this production method is easy prototyping with various shapes and various absorptive materials. We produced a test model and used a two-component epoxy encapsulant as the absorptive material. The test model achieved a low reflectance: $\sim 1\%$ at 100 GHz. The absorber is sometimes maintained at a low temperature condition for cases in which superconducting detectors are used. Therefore, cryogenic performance is required in terms of a mechanical strength for the thermal cycles, an adhesive strength, and a sufficient thermal conductivity. We confirmed the test-model strength by immersing the model into a liquid-nitrogen bath.