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One of the most important issues whether anisotropic conductive film (ACF) interconnection technology is suitable to be used for flip chip on organic board applications is thermal cycling reliability. In this study, thermally induced deformations and warpages of ACF flip chip assemblies as a function of distance from neutral point (DNP) and ACF materials properties were investigated using in situ high sensitivity moire interferometry. For a nondestructive failure analysis, scanning acoustic microscopy investigation was performed for tested assemblies. To elucidate the effects of ACF material properties and DNP on the thermal cycling reliability of ACF assembly, Weibull analysis for the lifetime estimation of ACF joint was performed, and compared with thermal deformations of ACF flip chip assembly investigated by moire interferometry. Results indicate that the properties of ACF have a significant role in the thermal deformation and reliability performance during thermal cycling testing. Therefore, optimized ACF properties can enhance ACF package reliability during thermal cycling regime. [DOI: 10.1115/1.1846062] Keywords: Anisotropic Conductive Adhesive Joint, Moire Interferometry, Thermal Deformation, Thermal Cycling Reliability, Delamination

Interface degradation between dissimilar materials in the flip chip packages with anisotropic conductive adhesive joint is susceptible to mechanical and electrical failure upon temperature cycling. Particularly the mechanical reliability of flip chip using anisotropic conductive films (ACFs) often depends upon the interface characteristics between the bumping/passivation dielectrics and adjacent materials. This paper investigates the delamination and cracking in polymeric bumping/passivation dielectrics (Cyclotene[TM] 4024) and the damage mechanism of interconnect bump with BCB bumping dielectrics upon temperature cycling. Adhesion and fracture surface morphology after die shear testing show that the weakening and delamination of BCB passivation layer at the die corner is the main cause of the reduction of die adhesion strength after the thermal cycling. The sliding trace on fracture surface after three-point bending fracture reveals that cyclic shear displacement in a polymeric BCB layer fatigue the interface bonding or interconnect bump upon thermal cycling, leading to mechanical delamination and functional bump failure. Passivation cracks also develop around the circumference of BCB passivation over aluminum pad. A model is presented for the degradation of interconnect bump with surrounding BCB passivation. [DOI: 10.1115/1.1756143]

The design of anisotropic conductive film (ACF) materials for chip-on-film and chip-on-glass liquid crystal display packaging technologies was examined by simulating a theoretical electrical conduction model having a physical contact mechanism. Two pressure dependent models were developed to analyze the contact area changes. Results indicate that a better design of ACF materials can be obtained through the understanding of the electrical conductivity of ACF.

The effect of Cu oxidation on the adhesion of Cu-base leadframe to epoxy molding compounds (EMC) was studied by low temperature oxidation of a Cu-base leadframe. The presence of cupric oxide next to the Cu2O verified the oxide layer structure of Cu/Cu2O/CuO/air. It was shown that initial oxidation improved the adhesion strength between EMC and Cu leadframe. Surface wettability and mechanical interlocking effect were found to be responsible fo the adhesion increase at the early stage of oxidation.