3D-Printed High-Frequency Components for 6G, Terahertz Applications, and Industry 4.0

Leipold Düsenfabrik is a well-established manufacturer of waveguides and amplifiers, serving demanding companies in the fields of communications, radar, medical technology, and industrial measurement and testing. To supply these companies with precise RF components even more flexibly and quickly in the future, we intend to fundamentally rethink the manufacturing and integration processes within the project.

The core innovation of the project »TERA-AMP« is the use of 3D laser micro-printing based on two-photon polymerization. Using this technology, we are manufacturing high-precision coupling structures for high-frequency applications – a world first in this field, according to current knowledge.

What Is 3D Laser Microprinting?

In 3D laser microprinting, a focused near-infrared laser is directed into a photoresist. Through two-photon polymerization, the material cures exclusively within the focal voxel. By precisely moving this focal point through space, we can create virtually any three-dimensional microstructure – with deviations from the design in the range of a few hundred nanometers.

Originally used in optics and nanotechnology, we are now applying this process to high-frequency technology: complex microstructures are directly transformed into functional coupling, filter, and antenna structures.

Integration Instead of Assembly and New Design Freedom

Instead of laboriously assembling individual components, we integrate couplers, filters, and, if necessary, antennas directly onto the MMIC or into the waveguide housing. This opens up new possibilities for design and prototyping:

• more compact, integrated RF interfaces
• fewer interfaces and thus lower losses
• features (e.g., built-in filters) that are difficult or impossible to implement using traditional methods
• coupling structures adapted to universal waveguide housings and any chip geometries

Additive manufacturing enables the creation of entirely new classes of highly integrated, application-specific RF components that we can quickly tailor to meet individual business needs.

Another advantage: The availability of this technology in Europe is becoming a key competitive factor. Our goal is to reduce dependence on non-European supply chains and to provide customized components in Europe on short notice.

In the project »TERA-AMP«, we are developing new manufacturing methods for waveguide amplifiers with integrated MMICs. The focus is on the direct integration of MMICs into waveguide housings, 3D-printed coupling structures between the chip and the waveguide, and integrated filter and antenna structures for functional integration.

We are systematically investigating and comparing three additive manufacturing approaches:

1. Direct 3D Printing of Polymer With a Metal Coating

We first print the HF structure using polymer and then apply a metallic coating (e.g., via sputtering or vapor deposition). The goal is to achieve smooth, conductive surfaces with high dimensional accuracy.

2. Reverse 3D Printing Followed by Electroplating

We print a negative pattern in the polymer, deposit the conductive metal structure using electroplating, and then remove the polymer. This results in a pure metal structure. The goal is to achieve excellent conductivity and RF properties in complex geometries.

3. Direct Printing of Metal (Currently Silver)

We manufacture the RF structures directly using additive metal fabrication. This can shorten the process, as no subsequent coating is required. The goal is to investigate the suitability of direct metal printing for EHF and THz components.

For all three approaches, we develop coupling structures, test them on waveguides and amplifier chips, and evaluate their RF performance.

Technical Objectives and Performance Parameters

In the frequency range from 75 GHz to 220 GHz, the newly developed components are expected to be at least on par with conventional solutions, with significant potential for performance improvement.

The main technical objectives are:

• minimal insertion and transition losses while maintaining maximum bandwidth
• optimized S-parameters, such as good S11 (insertion loss) and high S21 across the target frequency range
• reproducible fabrication of structures with submicrometer tolerances

We systematically compare the coupling, filter, and antenna structures produced using 3D laser microfabrication with conventionally manufactured reference structures, which are created through complex multi-step processes and assembled manually. Measurements using vector network analyzers (VNAs) show in which frequency bands the new approaches offer advantages in terms of attenuation, reflection, and bandwidth.

The development process for the project follows a clearly structured sequence:

1. Requirements Analysis and Specification
   We define the target frequency ranges and S-parameters and specify the interfaces between the MMIC and the waveguide.
2. Simulation and Design of RF Transitions
   We perform electromagnetic simulations of coupler, filter, and antenna structures and optimize them for loss, bandwidth, and manufacturability.
3. 3D Microprinting and Integration
   We manufacture the structures using 3D laser micro-printing (or direct printing of metal), integrate them directly onto the chip or into the waveguide housing, and, if necessary, perform subsequent steps such as metallization or electroplating.
4. Installation of the Waveguide Amplifiers
   We combine MMICs, 3D-printed structures, and waveguides to ensure mechanical stability and reliable RF contact.
5. Measurement and Validation
   We characterize the components using vector network analyzers, compare the S-parameters with those of conventional reference components, and derive optimization measures for the next iteration cycle.

Through this iterative process, we gradually develop robust design and manufacturing guidelines for 3D-printed high-frequency components.

Extending 3D laser microprinting to the EHF and THz ranges is technologically challenging.

Key challenges lie in material properties and conductivity – such as ensuring sufficient electrical conductivity in metallized or directly printed structures at high frequencies, as well as in finding suitable, low-loss dielectrics.

Surface roughness and the skin effect also play a decisive role: at frequencies above 200 GHz, current flows only in a very thin surface layer, so that even the smallest irregularities directly affect attenuation. Added to this are requirements for adhesion, delamination resistance, and process stability, particularly with regard to reproducible manufacturing processes for small-batch production.

At the same time, development requires a significant commitment of highly qualified resources, while investments in additional large-scale facilities remain comparatively low, as existing infrastructure is utilized. In parallel, we keep a close eye on market access and international competitors: The technology must hold its own against established processes not only technically, but also in terms of production time and costs.

The market for waveguide amplifiers and RF components in the EHF and THz ranges is currently dominated primarily by U.S. and a few European suppliers.

Current solutions are primarily based on conventionally manufactured waveguides – such as those produced by milling, electrical discharge machining, or micromechanical fabrication – as well as on the manual integration of MMICs via bonding, adhesive bonding, or wire bonding. Design flexibility remains limited, as the geometries must be adapted to the respective manufacturing processes.

By utilizing 3D laser micro-printing, the project is taking a different approach:

• unique selling point of 3D manufacturing: highly complex geometries, directly optimized for electromagnetic performance
• customization as standard: customer-specific couplers, filters, and antennas without the need for new tools or complex fixtures
• integration as a USP: multiple functions (coupling, filtering, radiation) combined in a single component

By combining multiple functions – such as coupling, filtering, and radiation – into a single component, a clear technological advantage over the current state of the art is achieved.

The project is based on close collaboration between industry and applied research:

• Düsenfabrik Leipold
  • brings many years of experience in the manufacture of waveguides and amplifiers.
  • supplies and manufactures MMIC amplifier chips and waveguides.
  • provides access to relevant markets and companies in the fields of communications, radar, medical technology, and Industry 4.0.
• We at Fraunhofer ITWM
  • develop and operate 3D laser microprinting for high-frequency applications.
  • handle the simulation, design, and 3D micro-printing of the coupling, filter, and antenna structures.
  • characterize materials and components and oversee their transition to small-scale production.

We can offer the technology both in the form of licensing models and as a contract manufacturer for small-batch production – and use the components we develop in our own non-destructive testing systems.

The 3D-printed high-frequency components developed in the project open up new possibilities in a wide range of applications. For example:

• High-Speed Communications and Satellite Systems
  • front-end modules for 6G and beyond
  • compact waveguide amplifiers in satellite links and backhaul links
• Radar, Sensors, and Industry 4.0
  • high-resolution radar sensors for automation and robotics
  • precise RF interfaces for measurement and testing systems in production
• Medical Technology and Non-Destructive Testing
  • imaging and Diagnosis in the Terahertz Range
  • testing and inspection systems in which we at Fraunhofer ITWM are already using high frequencies today

The project »TeraAmp« (Terahertz Amplifier), which includes the subproject »TeraFAB« (Terahertz Component Fabrication), is part of the Central Innovation Program for SMEs (ZIM) and runs until the end of August 2026; The goal is to translate the technology into marketable products, licensing models, and small-batch production, thereby creating a sustainable competitive advantage for European industry partners.