Maskless additive printing processes for miniaturization of sensors and microcircuits

LTCC and HTCC multilayer technology is used to manufacture miniaturized ceramic sensors and microcircuits. It is based on the structuring of ceramic films by means of punching and laser technology and their functionalization by means of mask-based printing processes, such as screen and stencil printing. These printing processes are established, reliable and enable high process throughput. However, in the case of low quantities or required flexibility in design, mask printing represents a significant disadvantage for cost and time reasons. In addition, the geometric freedom is limited to two-dimensional components and thus, the achievable degree of miniaturization.

Digital printing technologies, such as inkjet or aerosol jet, are a cost-effective alternative that can be used to produce small quantities and individualized products economically. These printing processes are completely additive and maskless, making them highly flexible. Comparatively large geometries, such as conductor tracks and contact pads, are printed using the inkjet process, while fine-scale areas (< 50 µm) are printed using the aerosol jet process. The combination of both printing technologies enables large-area and simultaneously precise structuring of multilayer ceramics on the one hand, and the creation of three-dimensional structures on the other.

A special feature are the dielectric ceramic inks based on LTCC, which replace conventional ceramic green films. Furthermore, sacrificial inks are used to implement self-supporting structures, such as membranes or webs. This increases the flexibility of the manufacturing process, the geometric degree of freedom and the achievable integration density. The challenge here is to adapt the materials and processes in terms of material compatibility and sintering-related shrinkage.

© Fraunhofer IKTS
Maskless LTCC process for additive manufacturing of sensors and microcircuits (AJ: aerosol jet printing, IJ: inkjet printing).
© Fraunhofer IKTS
Inkjet-printed vias with a diameter of 0.03 mm and overlying layer with conventionally manufactured, stencil-printed vias (0.3 mm).
© Fraunhofer IKTS
Buried aerosol jet printed meanders (line width 0.01 mm).
© Fraunhofer IKTS
Scanning electron micrograph of an aerosol jet-printed test pyramid (height approx. 40 µm). A ceramic LTCC ink was printed on a dielectric green tape.
© Fraunhofer IKTS
Micrograph of the sintered LTCC structure: modified microstructure of the aerosol jet-printed layer (top) compared to the dielectric green tape (bottom).

A more advanced goal is to demonstrate the novel additive LTCC processes for miniaturized ceramic microsystems using sensors (pressure, flow, IR and quantum sensing) and circuits as examples.

Print resolution of aerosol jet and inkjet printing on LTCC tapes

Parameters
Aerosol jet printing Inkjet printing
Conductor width from approx. 15 µm from approx. 75 µm
Layer thickness approx. 1–30 µm (depending on print repeat and print speed) 1–5 µm
Via diameter - approx. 20–50 µm
Printable metallizations Silver, gold, platinum, RuO2 glass, copper, CuNi Silver, gold, copper
Printable dielectric layers LTCC, carbon (carbon black) Carbon (carbon black)

Services offered

  • Development of hybrid ceramic sensors and microcircuits based on additive printing processes incl. suitable inks
  • Sample production (small series)
  • Technology transfer

 

Project name: High-resolution additive printing and manufacturing processes for the production of hybrid functional ceramic components (MuSKeL)

Funding: IGF

Project management agency: AiF

Funding code: 21339 BG

Project period: 01.01.2021 until 31.12.2022

Project partners:

  • Hahn-Schickard-Gesellschaft für angewandte Forschung e.V.