Flux residue cleaning process optimization effect on Flip Chip Ball Grid Array reliability

Abstract

This paper discusses the evaluation and characterizations of the cleaning the organic residues on Flip Chip Ceramic Ball Grid Array (FCCBGA) package. Flux used for Control Collapse Chip Connection (C4) die attachment during assemblies could remain on the die surface as organic residues, thus affecting the integrated circuit performance. Therefore, the effect of implementation flux-cleaning process on the die cleanliness was evaluated. Design of Experiments (DOE) for cleaning chemical parameters using water-based solvents was carried out to investigate the flux-cleaning efficiency. The response for the experiments conducted was die surface cleanliness. The presence and levels of contaminations would be analyzed and characterized using Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and Ion chromatography (IC). The optimization process required the integration between mechanical and chemical parameters. Chemical cleaning parameters optimization was aided with Micro Phase Cleaning (MPC) as solvent. Wash temperature and solvent concentration were varied to find the optimal cleaning. Whilst for mechanical parameters, washing pressure, and nozzle orientation are the expected parameters that would give impact to the cleaning process. From the experiments, the cleaning process is optimized with 3% of MPC solvent added into the pure DI water with longer wash exposure time 0.3 m/mm at 10 Psi with 75°C. The optimization result is proven with thermal cycle testing where no delammation or voids are detected even after 2500x.