How to neatly solder the following TRRS connector?
The most common mistake most people make when soldering connections like this is to use a soldering iron without enough power, which causes the connector to heat up slowly and in the process transfer heat to the plastic and melt it. The key is preparation and speed, get in get out as fast as possible and you won't melt the plastic; to do this you have to be able to get a lot of heat into the connector very quickly.  The MetCal (on Amazon.com, now unavailable) soldering iron is what I use, and is ideal for this sort of task it can very quickly put huge amounts of power into the connector (if you want to know how look up how RF soldering irons work, very clever.). You must prepare the wires by tinning them first with solder, and also the connector separately. Following this, allow them to cool and ensure the tinned ends are trimmed to just the right length. After that, place the tinned wire-end on top of the tinned connected, heat with a very powerful iron for less than a second and hold the wire still while it cools, and you will have a perfect connection.