The high-frequency characteristics of tape automated bonding (TAB) interconnects

Tape automated bonding (TAB) tape is modeled as a transmission line, since, above 5 GHz, the tape length is significant compared to the signal wavelength. A test chip was fabricated to allow determination of the microwave characteristics of 3M's 120-lead, two-layer gold-plated electrodeposited copper tape, which has a polyimide support layer and an inner lead pitch of 8 mils. A characteristic impedance of 100+or-10 Omega was found for the tape based upon measurement up to 18 GHz. This compares well with the theoretical model, which predicts an impedance between 98 and 118 Omega . Theoretical models and practical considerations were used to design a TAB tape with a lower impedance and good signal isolation. This design is presented.<
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