Microwave and mm-meter wave applications: a new challenge for ceramic thick film technology

Applications for microwave circuitry are expanding rapidly, particularly in the field of portable communication systems, and the operating speeds of digital integrated circuits (ICs) continue to increase, creating the need for suitable interconnect materials, integrated components and packaging solutions. Several papers have been written in the last five years to describe the characterisation and the performance of ceramic thick film in high frequency applications and to compare these properties with other interconnect technologies such as thin film and high performance PWBs under the same test conditions. This paper briefly discusses these issues and reviews the reasons for the choice of thick film in some recent microwave and mm-wave modules for wireless communication and airborne radar applications, where the operating frequencies are in the medium-high GHz range. In particular, different modules are discussed and details given of their design and construction. The first two examples considered are two converter modules, both mm-wave, one down-converter operating in the 7.0-8.5 GHz frequency range and one transmitting up-converter, operating at a frequency of 23 GHz. Both modules have been manufactured using thick film materials on alumina substrates. The other applications described are a highly integrated mm-wave module operating in the frequency range of 27 to 30 GHz and a high power Ka band amplifier. Both application use LTCC multi-layer substrates. The paper also reviews in some detail the packaging solutions adopted in each case, including some information about the choice of materials, components and interconnect technologies. (6 pages)