Solder Flux Syringe & Needle
Another type of flux to the hard flux that is used for the your soldering iron tips
This is ideal for adding a tiny amount to the PCB pad or component that you want to solder. This cleans and help the solder flow making a good solid joint.
Choose either Paste or Liquid
This stuff goes along way so you don't need much but it will help.
The most common mistake i see is people not using flux
Comes in a syringe with a needle approx 10ml A little bit goes a long way