— Typically, placement algorithms attempt to minimize the total net length of a printed circuit board (PCB). However, an MCM’s increased throughput and dense circuitry can easily result in failure if the board contains “hot spots”. Therefore, an accurate thermal model of an MCM was needed in the development of a new placement algorithm designed to consider both total net length and thermal constraints. This algorithm uses a combination of simulated evolution and simulated annealing in an iterative approach. Each chip has a maximum thermal tolerance that it can withstand before it is known to fail. The fitness method evaluates the maximum temperature for each chip, considering every chip’s thermal dissipation at the chip’s hottest point. Results are presented that compare the effects of various parameters.