Assembly processes for flip chips on substrates

Flip chip assembly is a key capability to enable product miniaturization. Our previous studies have investigated several flip chip interconnection types, including anisotropic conductive film or paste, and Au-Au thermosonic bonding. This project focuses on the assembly of 0.200-and 0.250-mm-pitch solder flip chip devices. Two methods of applying flux for the flip chip are investigated: the dip fluxing method, and jet fluxing of the substrate. The placement accuracy of a traditional SMT pick-and-place system (upgraded for flip chip) is investigated and the results are discussed. The impact of the reflow process in air vs. nitrogen is also examined. Two underfill materials are evaluated for compatibility with the flux. Results of reliability testing (including thermal cycling, mechanical shock and vibration) are presented.