LTCC technology and its applications in high frequency front end modules

The ongoing developments of low temperature co-fired ceramic (LTCC) technique are making it more and more attractive for applications in microwave and millimetre wave frequency band. The most active areas for high frequency applications include Bluetooth module, front end module (FEM) of mobile phones, wireless local access network (WLAN). Local multipoint distribution system (LMDS) and collision avoidance radar etc. The recent development of LTCC substrate material extend the applicable frequency of the technique up to 100GHz. Owing to the feature of low conductor loss, low substrate loss, and up to 50 laminated layers, LTCC provide a harmonic bed for embedded microwave and mm wave passive components and accessories including antennas. In addition, LTCC substrate material has a wide tuneable range of thermal expansion coefficient. It is this feature that makes the LTCC substrate very attractive for various integrated packaging. In the presentation, the present status of the technology will be reviewed, from its manufacturing process, material properties to RF and microwave performance of typical LTCC modules. The LTCC market projection and cost issue will be also discussed to have a globe view of the technology. A large number of practical examples for high frequency applications will be followed to display the current technology status. The examples include, but not limited to, (1) RF front end module for mobile phones, (2) antennas for WLAN and Bluetooth devices, (3) laminated waveguide and other new form of transmission lines for mm wave applications, (4) integrated mm wave antenna arrays, and (5) Integrated RF modules such as high performance VCO. balanced LNA, miniaturized RF filters and balun. Since the most challenge issue in LTCC module designs is the integrated passives, the emphasis of the examples will be placed on the embedded passives and system integration. Some practical LTCC modules developed in The Chinese University of Hong Kong are listed in the following. The details of these modules can be found in the listed references and will be further elaborated in the presentation.