LTCC antenna and packaging technologies from 100 GHz upwards

Topic

Aerosol jet printed transition from LTCC substrate to MMIC chip.
Ceramic antenna housing with FineLine gold metallization (approx. 10 mm x 10 mm).
Detailed view of an MMIC integrated in an LTCC package.

Antenna-on-chip (AoC) and antenna-in-package (AiP) are the technological antenna variants that can be used to realize fully integrated, low-cost and surface-mountable millimeter-wave systems (MMIC, monolithic microwave integrated circuit) for high-frequency applications in telecommunications and radar sensing. However, MMICs with antenna-on-chip solutions have the disadvantage of limited antenna efficiency and directivity. In contrast, antenna-in-package technology, in which the antennas are integrated in the housing of the MMIC's package, offers significantly higher bandwidths and better antenna efficiency.

 

Antenna-in-package technology

 

For high-resolution radar systems or radio applications with high bit rate, very high bandwidths are required to generate a good resolution of the sensor. At Fraunhofer IKTS, an extremely broadband aperture-coupled and stacked antenna-in-package for radio frequency applications has been developed based on LTCC technology, which can be used at a target frequency of 140 GHz.
The antenna physical characteristics include a rectangular aperture, two stacked printed patches, and a two-layer via stacked patch antenna (SPA, stacked patch antenna) fence. The aperture as well as the necessary microstrip lines have a width of approx. 30 µm and were applied to the LTCC substrate by FineLine screen printing, aerosol jet printing or laser structuring.

 

Packaging technology: Aerosol jet printed MMIC contacts 

 

Wire-bond and flip-chip technologies are commonly used for contacting 50 µm thin MMICs for high-frequency applications, which have disadvantages for applications above about 120 GHz: With wire-bond contacting, high losses are to be expected due to the wire length, and the flip-chip solution is difficult to use due to reliability and handling problems. Here, the printing technologies used at Fraunhofer IKTS help to close the existing technological gap. Aerosol jet printing can be used to print coplanar lines directly onto the MMIC chip. This creates a direct transition between the lead on the ceramic LTCC substrate and the contacts on the chip.

 

Packaging technology: Ceramic housing

 

The developed planar SPA antenna is part of an LTCC package that both rewires the MMIC chip with the external contacts and ensures a connection from MMIC to antenna with very short lines. The FineLine tracks (30 µm track width) are realized by screen printing which is compatible with mass production. The LTCC package can be rotated and soldered to a suitable printed circuit board via the contact pads on the outside.  

Technical characteristics

 

  • Miniaturized SPA-LTCC antenna for 140 GHz application with a bandwidth of 15 GHz
  • Aerosol jet printed transition to MMIC: insertion loss of 2 dB at 140 GHz and about 3.3 dB at 200 GHz
  • 10 mm x 10 mm (variable) LTCC package with integrated SPA antenna for 140 GHz applications

 

Services offered

 

  • Development of ceramic multilayer high-frequency components according to customer- specific designs
  • Selection and characterization of suitable LTCC materials, pastes and inks
  • Development and qualification of manufacturing routes for antennas and packages
  • Sample production in small quantities
  • Characterization and transfer of the manufacturing technology

 

The results have been obtained within the BMBF project “TeraKer - Terahertz Ceramic Circuits for Sensors and Communication“.