Author: Claude Drevon Company: Alcatel Space Industries Date Published: 4/1/2001
Abstract: Among the various possibilities of flip-chip, the use of thermocompression with gold bumps is the way for connecting GaAs bare dice off the shelves. This paper describes and comments the choices made by Alcatel Space on flip-chip for RF applications. The electrical and thermomechanical results presented, both on alumina and aluminum nitride substrates, show that this technology is really mature and could be used for any RF hybrid, specially when the electrical performances are a function of the length of the connections. In term of bonding reliability, the results give values over more than five times the limits from the standards, even after 500 thermal cycles. From an electrical point of view, the RF measurements made after flip-chip bonding are close to the wafer level measurements, with a shift on gain less than 1 dB on all the frequency range. Some prospects, mainly for the thermal management of power RF hybrids are also developed with preliminary choices and calculations. Power flip-chip could give at least 40% reduction in the Rth for an amplifier with flip-chip mounted MMIC with emitter bumps.
Keywords: flip-chip, power flip-chip, RF, space application.