the only thing i've seen cause cop's to melt, is extreme engine temp (major overheating), or internally shorted coil shorting through its own body/insulation (usually due to a crack or defect). the spark is going to find the shortest way to a good ground, if thats through a crack in the side of the coil thats where it will jump. check for white residue on the body of the coil (indicating a shorted coil).