Designing robust power distribution network with decreasing power supply voltage and increasing power density in given N-metal layer resources is very critical for chip performance and reliability. In this paper, we present novel and efficient IR-Drop models for designing correct by construct power distribution network of N-metal layer system for wire-bond and flip-chip designs based on the given design constraints such as chip power dissipation, total IR drop budget and power supply voltage along EM and manufacturability constraints as per the technology. Using these models, designer can also perform trade-off for effective metal resources utilization in desired metal layers system for power distribution network and signal routing resource needs. Results have been verified with industry standard EMIR analysis tool and are within 1-5% for both wire-bond and flip-chip designs. These models have been validated on 90nm, 65nm production designs.