Optimizing Component Design Via Coated Micro-AM Parts For Exacting Precision Engineering And Semi-Conductor Applications

Recently, micro-AM technologies have developed into cost-effective, relatively quick, and highly precise production technologies, which can build to micron level tolerances, and more importantly, can do so repeatably with economically viable yields. The materials that can be processed by the various micro-AM technologies available today, however, are almost exclusively polymers, and as such manufacturers looking to embrace the power of micro-AM but requiring non-metallic conductive, environmentally resistant, or metallic properties have been left frustrated. Horizon Microtechnologies’ proprietary coating processes have been developed to bridge this gap.

Imagine a suite of coating processes that adds material and functionality to a microstructure (the template), developed to work with a range of template materials (but most commonly plastic) and nearly independently of the template’s shape, which makes them particularly suited as post-printing treatments for micro-AM derived templates. Imagine how this can disrupt the production of micro-parts, impactfully making micro-AM a credible manufacturing alternative to traditional production processes in a range of industrial sectors and specific applications where the functionality of plastic was inappropriate for end-use effectiveness.

It is with that vision in mind that Horizon developed its 3D template based microfabrication processes that add a homogeneous / conformal coating across an entire part, the thickness tolerance of the coating being more precise than the 5 micrometer tolerances that can be attained through an optimized micro-AM process. The process is also different from other more traditional coating processes, and has been designed to work with often complex 3D shapes and to coat intricate and complicated geometries and internal channels.

AM has of course already disrupted the ways in which various sectors produce end-use parts for an array of applications. It has been recognised across industry as affording manufacturers access to an agile, cost-effective, and versatile technology that promotes hitherto impossible geometric complexity while at the same time democratising manufacturing. Micro-AM technologies have opened up the advantages of AM for micro manufacturers, and by developing microfabrication technologies it is possible to extend the areas in which AM can have a positive influence.

PROPRIETARY COATING TECHNOLOGIES

What precisely are the processes that Horizon has developed? Well put simply, they are post-micro AM build coating technologies that can add non-metallic conductive coatings, environmentally resistant coatings, and metallic coatings to micro-AM produced parts.

Non-metallic conductive coatings. To introduce conductivity while maintaining  transparency, once the part is produced on a polymer-AM platform, it is either wholly or selectively coated with a non-metallic conductive, transparent layer. Even difficult to treat areas such as long narrow channel and undercuts can be coated homogeneously. The process is especially powerful with challenging parts where other legacy coating processes struggle. For example, it is able to coat parts with aspect rations of 150:1, more than 10 times greater than standard coating technologies can achieve. Sheet resistances as low as 16 Ω/ can be produced.

The ability to add non-metallic conductive coatings to all or selected parts of a 3D microprinted part is obviously of interest to manufacturers of electrodes, electrical sensor heads, and ESD-safe components. In a gas flow sensing application, for example, product designers may find themselves in need of a conductive part for heating or readout purposes based on the temperature coefficient of resistance. At the same time it may be necessary to balance the opposing requirements of high surface area and low flow resistance. Here, the design freedom and precision of polymer micro-AM allows the printing of a tailored, repeating lattice structure (as opposed to say an irregular foam) with exactly the desired surface to volume ratio, pore sizes, and flow resistance, as illustrated in Figure 2. The non-metallic conductive coating renders the polymer part conductive and allows for heating as well as electrical readout.

Environmentally resistant coatings. Microfabricated 3D templates can also be coated with metal-oxides to make parts compatible with aggressive chemical environments and in some cases can notably increase the resistance to high temperatures and mechanical stresses.

The ability to add environmental resistant coatings to parts is important because it enables the creation of microscale devices that are more durable, reliable, and better suited for use in harsh environments, and this can lead to improved performance and longer lifetimes for these parts and components, making them more suitable for use in a wide range of applications.

One such example is the fabrication of nozzles and 3D microfluidic devices. Micro AM is well suited to the design and small batch production of geometrically complex multi-level microfluidic chips, including chips with integrated interfaces or filters. However, micro-AM compatible materials are sometimes not suitable for use with aggressive solvents, acids or bases. Horizon’s post-build coating process solves this problem by hermetically encapsulating the part and works reliably even on the inside of microfluidic channels. Hence, it allows the combination of environmental resistance with the design freedom stimulated through the use of micro AM for a broader range of fluids than previously possible.

Metallic coatings.Horizon is also able to add copper metal coatings to polymer micro-AM and other micro structures. This means that for the first time, companies can produce parts with the functionality of copper but also exploit the design freedom, precision and resolution achievable through micro-AM.

Copper coatings open up an array of application possibilities for companies wishing to add functionality to micro-AM templates. They can offer significant benefits for microfabricated or micro-AM parts, but there are several challenges and problems associated with current coating solutions that Horizon has addressed to ensure the successful application of the copper. The coating process, materials, and deposition parameters have been carefully optimized to overcome these challenges to harness the full potential of copper coating which can now be applied reliably, cost-effectively, and speedily, making it viable for a whole range of applications.

The addition of copper coatings to micro-AM or other 3D microfabricated templates can offer numerous advantages, most importantly improved electrical and thermal conductivity.

Horizon’s coatings are typically in the 1-2 micron thickness range, and importantly the company’s process can also coat internal channels and undercuts to some degree, the channel’s aspect ratio being the limiting factor now rather than the absolute length.

The technology is ideally suited to the very many applications where the use of bulk copper is not required and would be technically impossible or uneconomic. Making geometries via polymer AM not possible through the use of bulk copper, and then adding the functionality of a copper coating is therefore highly disruptive. Additionally — and importantly — if parts are designed well, Horizon’s copper coating can be used not just to coat an entire micro-part, but to selectively coat features on a given template, creating several independent metal features for interconnects, vias, etc. as illustrated in figure X.

Beyond conductivity, copper coatings can also significantly improve the surface properties of micro fabricated parts by adding wear resistance, lubricity, and hardness.

The key application areas for copper coated micro-AM and microfabricated templates are those that require high precision, complex geometries, and advanced materials properties, such as high electrical conductivity,. As such, opportunities exist in the production of micro-electronic devices such as antennas, free-form printed circuit boards, interposers and interconnects; micro-sensors; miniaturized biomedical devices (such as implantable sensors); drug delivery systems; lab-on-a-chip systems, micro-reactors, and microfluidic sensors; and MEMS actuators and transducers.

USE CASE – PASSIVE MICROWAVE & MM-WAVE COMPONENTS

The metallization of micro-AM templates represents a highly intriguing and disruptive advancement in the realm of micro passive microwave & mm-wave component production, including parts such as antennas, filters, and mixers. Micro-AM as already explained has revolutionized the fabrication of micro-scale structures, enabling the creation of complex geometries with exceptional precision. When applied to passive microwave & mm-wave component design, this technology therefore allows for the production of micro-scale parts with unprecedented possibilities for customization, geometrical intricacy, and ease of fabrication.

The metallization process involves coating the 3D-printed structures with copper which confers electrical conductivity. This step is crucial for passive microwave & mm-wave component as it enables efficient electromagnetic wave reception and transmission. The unique geometric freedom afforded by micro-AM empowers engineers to design and optimize passive microwave & mm-wave component with innovative shapes, resulting in improved radiation patterns, novel design options for filters and beam splitting architectures, and enhanced overall performance compared to conventional manufacturing techniques.

Moreover, micro-AM produced passive microwave & mm-wave components promise enhanced miniaturization and integration possibilities. The compact size and customizability of these parts open up new horizons for wireless communication systems and the Internet of Things (IoT). As a disruptive technology, this advancement can lead to a paradigm shift in passive microwave & mm-wave component design, making it more accessible and cost-effective for a wide range of applications. From wearable devices and implantable medical sensors to miniature drones and space-constrained electronics, metal-coated micro-AM antennas, for example, have the potential to revolutionize the way we approach wireless connectivity in the future.

By incorporating all mm-wave system elements into a single micro-AM produced structure, metalized micro-AM templates reduce the risk of misalignments and assembly errors. This leads to improved overall performance and reliability of the mm-wave systems. Furthermore, the elimination of separate parts and connectors reduces the overall weight and size of the mm-wave system, making it highly suitable for applications where space and weight constraints are critical, such as in portable devices and wearable technology. Additionally, the simplified manufacturing process and reduced reliance on manual assembly translate into cost savings and faster production times, making the technology economically attractive for mass production.