GPD Xd: Soldering Shoulder Ribbon
My apologies. This was gross, but it works.
Try and use a flat iron tip.
Make sure you take note of the direction the ribbon goes, the mechanical button, and the end of the ribbon being brown side, or copper side.
I have had to re-solder because I put it on wrong.
As you are looking down at the ribbon you are soldering:
The shiny part goes down ( copper side of the tip ).
The dull side of the ribbon faces you ( with the brown side showing on the tip )