LTCC millimeter wave circuits and packaging up to 100 GHz

Topic

Figure1: 6x6 Zoll HF-LTCC wafer with 5 parallely manufactured circuits (Design: Fraunhofer FHR).

Ceramic materials are with outstanding RF-properties (er, tand), high thermal conductivities for heat removal in combination with a very good thermomechanical adaption to typical semiconductors. Especially the chance to embed functional elements like conductor wirings, resistors and capacitors inside the ceramic and at the same time to manufacture in mass-producible multiple panel substrates (ceramic wafers) the multilayer ceramic technology is an interesting alternative.

Figure 1 shows a radio frequency circuit manufactured at IKTS on a 6“x6“ multiple panel (material: 9K7).

The decisive factors for the manufacturing of ceramic compatible RF-structures are the choice of appropriate materials for functional integration and the optimization of the manufacturing technology for the generation of geometrically accurate designs. Special attention must be paid to the accuracy of the printed structures and of the implemented cavities, used for the placement of the monolithic RF-semiconductor chips.

The figures 2 and 3 show examples of further radio frequency circuits manufactured at IKTS.

Figure 2: HF-signal redirection into the ceramic substrate surrounded by a via fence.
Figure 3: X-Ray of a HF-circuit board with 5 signal layers and an overall thickness of about 500 µm.

Another essential advantage of the multilayer ceramic technology in comparison to polymer based Rogers-materials is the ability to manufacture complex self-supporting three-dimensional structures.

Figure 4 shows an example of an RF-circuit with 10 parallel self-supporting Vivaldi antennas.

Figure 4: Test structure with 10 parallel Vivaldi antennas on a ceramic substrate (Design: Fraunhofer FHR).