Thin film substrate technology and FC interconnection for very high frequency applications

High speed interconnections for the next generation Internet or high frequency measurement systems need ultra fast photodetectors and appropriate high frequency transmission lines. A highly critical aspect for packaging these devices is the interconnection and the appropriate substrate technology. Thin film substrates using BCB are a suitable approach due to the high accurate manufacturing technology and the possibility to use low k dielectrics. FC assembly is the best interconnection technology for this very high frequency application, and it is already proven in production. Ultra-fast InP-photodetectors (100 GHz) with CPW signal pads (GSG) had to be connected to a 1 mm RF plug via a micro-stripline (MS). Flip chip bumps on InP and interconnection schemes for CPW to MS transitions were investigated. The electrical performance of these structures has been simulated and is discussed with respect to the electrical tests done on the samples. The process compatibility of the chosen materials was verified separately and the properties adapted, if necessary. Reliability tests have been performed on test samples and are discussed also in the paper with respect to substrate technology and to the FC assembly.