Transmission property of flip chip package with adhesive interconnection for RF applications

The radio frequency (RF) and high frequency performance of the flip chip interconnects with anisotropic conductive film (ACF) and non-conductive film (NCF) was investigated and compared by measuring the scattering parameters (S-parameters) of the flip chip modules. Low cost electroless-Ni immersion-Au (ENIG) plating was employed to form the bumps for the adhesive bonding. To compare the accurate intrinsic RF performance of the ACF and NCF interconnect without lossy effect of chip and substrate, a de-embedding modeling algorithm was employed. The effects of two chip materials (Si and GaAs), the height of ENIG bumps, and the metal pattern gap between the signal line and ground plane in the coplanar waveguide (CPW) on the RF performance of the flip chip module were also investigated. The transmission properties of the GaAs were markedly improved on those of the Si chip, which was not suitable for the measurement of the S-parameters of the flip chip interconnect. Extracted impedance parameters showed that the RF performance of the flip chip interconnect with NCF was slightly better than that of the interconnect with ACF, mainly due to the capacitive component between the bump and substrate and self inductance of the conductive particle surface in the ACF interconnect.