A 2D simulation is carried out using dimensionless phase field formulation to delineate the fate of a droplet at a T-junction microchannel for different viscosity ratios. The model is validated by experimental findings and scaling law from the existing literatures with good agreement. We captured three regimes (for fixed droplet length) namely, breakup with tunnels, breakup with discontinuous occlusion, and no-breakup. Furthermore, the variation in viscosity ratio revealed the existence of regimes that were not found in the literature, for the investigated droplet length, for different Capillary number. Next, we show new breakup characteristics as the viscosity ratio is varied. These classifications are mainly based on the relative dominance of surface tension represented in the Capillary number and viscosity ratio. Finally, we present a phase diagram to illustrate the boundary transitions of different regimes.