Keyboard switch removal problems
If you heat the board for too long, or get it too hot the material under the copper layer starts to burn and the copper gets loose.  you were probably smelling the burning of the resin in the board. 

this can be caused but soldering too slowly, not using enough flux, or the wrong temperature on the soldering iron.

if it's too cold it takes too long to make the joint and the board or the parts are damaged before the joint is completed. if it's too hot the flux burns up and makes it hard to make a good joint, same bad result.  

try 370 next time, see if that's better.