Microwave performance of flip chip interconnects with anisotropic and non-conductive films

Anisotropic conductive films (ACFs) and non-conductive films (NCFs) are film-type, adhesive polymer resins that have been used in flat panel display modules to provide high-resolution, light weight, thin profile and environmental friendliness. We investigated the radiofrequency (RF) and high frequency performance of the flip chip interconnects with ACF and NCF by measuring the scattering parameters (S-parameters) of the flip chip modules. The effects of three chip materials, Si, quartz and gallium arsenide (GaAs), 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 were also investigated. The transmission properties of the GaAs and quartz chips were markedly improved over those of the Si chip, which was not suitable for the measurement of the S-parameters of the flip chip interconnect. The RF performance of the flip chip module with NCF was slightly better than that of the module with ACF, mainly due to the capacitance of the epoxy resin between the Au bump and pad and the self-inductance of the conductive particle surface in the ACF interconnect.