Ultra low-profile self-matched HTCC SAW-duplexer: manufacturing and performance challenges

Providing the required ability of simultaneously transmitting and receiving RF signals, duplexers are one of the key components in the well established 3G (W)-CDMA communication systems. For mobile terminals, duplexers in micro-acoustic filter technology have been used for several years. Generally, these duplexers are composed of two band pass filters and additional passive elements to improve the electrical performance. Based on the prototypical packaging approach which has been used for the recently published demonstrator of the ultra low profile self-matched SAW-duplexers we will present details of the preliminary extension of the well established Cu-frame CSSP3 packaging technology. This extension enables the integration of miniaturized planar copper coils on the top layer of an HTCC substrate. Therefore, it leads to a new miniaturization potential for the coming generations of packages for self-matched duplexers in SAW or BAW technology. Additionally, we will present some novel investigation results regarding the influence of the manufacturing process on the Q-factor. Here, the surface roughness determined by the manufacturing process and by the roughness of the HTCC at the interface of the coil and the HTCC affects the Q-factor. Including the surface roughness in the electro-magnetic simulation allows us to determine the resulting Q-factor of the planar coils very precisely. The excellent match of measured and simulated Q-factors approves this approach. Furthermore, using an EM-model with the roughness modeling for the coils, we have been able to predict the insertion loss of our filters accurately which will be demonstrated by the very good agreement of measured and simulated scattering parameters of the ultra low-profile self-matched duplexer.