And, despite all the "Do NOT use flux" warnings in the decoder manuals, a very minute amount of solder paste (with the rosin-core solder) will ensure a bright, shiny solder connection at the solder pad. Unless you leave the soldering iron on it for 10 seconds, you're not going to delaminate the pad from the board. I always follow it up a Q-tip dipped in 91%/99% alcohol or Flux-Off to remove any residual flux from the soldered area of the board.