Laura Galloway
As electronic systems become smaller, faster, and more functionally integrated, the packaging technologies that connect them must evolve. Traditional approaches like printed circuit boards, LTCC, and lithography-based fabrication often fall short when it comes to routing complex electrical pathways—especially in compact 3D architectures or between non-planar components.
A recent study led by HRL Laboratories introduced a novel approach: fabricating ceramic interposers with thousands of high-aspect-ratio, curved, and angled vias using additive manufacturing. These interposers were designed to electrically link curved infrared (IR) detectors with flat readout integrated circuits (ROICs) and to fan out fine-pitch arrays into wider pitches—enabling new form factors in advanced imaging and sensing systems.
High-Precision Additive Manufacturing at the Core
To realize these complex geometries, researchers used the microArch® S230 from Boston Micro Fabrication (BMF), a projection micro stereolithography (PµSL) printer capable of micron-level resolution. The platform’s ability to produce highly detailed features with repeatable accuracy made it essential to the project’s success.
Using a custom preceramic siloxane resin formulation filled with silica nanoparticles, the team printed interposers with:
- Via diameters as small as 9 µm, spaced as closely as 18 µm apart
- Aspect ratios up to 150:1 across centimeter-scale components
- Dimensional accuracy within ±2 µm for 90% of vias—critical for pixel-level alignment, enabling smooth transitions and curved paths
After printing, the parts were converted to ceramic through pyrolysis and metallized by melt infiltration using a CuInTi solder alloy. This produced conductive pathways with electrical resistivity of approximately 4 × 10⁻⁸ Ω·m—comparable to bulk copper and suitable for high-density signal routing.
Fig. 1. Schematic of additive interposer fabrication (a): Micro-DLP of preceramic resins is used to 3D print preceramic polymer interposers, (b) the preceramic polymer is converted to ceramic by pyrolysis heat treatment, (c) the vias are metallized by melt infiltration with a solder alloy, (d) the interposer is integrated with a curved infrared (IR) detector and a flat read out integrated circuit (ROIC) to route the signal from the pixels on the curved surface to the planar surface.
Real-World Designs and Applications
Two interposer designs were developed to demonstrate the potential of this fabrication method:
- Curved-to-planar interposer: Designed to connect a hemispherical IR sensor to a planar ROIC, this structure contained more than 75,000 curved vias across a 16 mm × 16 mm part. The ability to decouple pixel geometry from chip layout enables imaging systems with wider fields of view, better optical performance, and reduced size and complexity.
- Fan-out interposer: This structure redistributed vias from a 30 µm pitch to 70 µm across the part, enabling designers to optimize both sensor resolution and ROIC footprint. Traditional manufacturing processes cannot achieve this type of routing without multiple steps, custom tooling, or increased cost.
These capabilities are particularly relevant to fields like 3D heterogeneous integration (3DHI), defense and aerospace imaging, and next-generation sensor systems that demand compact, high-performance packaging with tight tolerances.
How BMF’s Technology Made It Possible
The success of the study hinged on BMF’s micro-scale 3D printing capabilities, which allowed researchers to prototype and iterate complex designs with minimal lead time and no need for custom tooling or masks. The microArch platform delivered:
- Ultra-high resolution with consistent voxel fidelity
- Design freedom to print arbitrarily curved or angled vias
- Compatibility with preceramic materials and post-processing workflows
- High repeatability across thousands of critical features
This combination of precision, flexibility, and process control is what made it possible to fabricate interposers that go beyond the constraints of conventional packaging.
Fig. 3. Via-array in the as-printed state (a) and after conversion to ceramic, with a pitch of 18 μm (b). The sample was not polished before taking images. (c) Vias printed at a 45◦ angle. The vias are filled with epoxy resin from the mounting and polishing process conducted before imaging. (d) Angled via shows steps from print layers. (e) SEM image of microstructure after conversion to ceramic showing SiO2 nanoparticles.
Unlocking New Potential in Electronics Packaging
This work highlights how micro-precision additive manufacturing can break through long-standing barriers in electronics packaging. For applications that require dense interconnects, complex routing, and space-efficient architectures, platforms like BMF’s microArch offer a powerful and scalable solution.
By enabling designs once considered impossible—such as curved ceramic interposers with thousands of micron-scale conductive pathways—BMF’s technology is helping engineers push the boundaries of what’s possible in electronic integration and device miniaturization.
🔍 Read the Full Study
Explore the complete technical paper published by HRL Laboratories:
🔗 Learn More About HRL Laboratories
For more information about HRL’s research in advanced packaging and electronics: