If you go on EBay and search for solder paste - the pro stuff costs an arm and a leg for small amounts, so I was wondering if it is possible to make entry grade solder paste at home. After looking at several forums, I found a forum conversation in which someone used shavings from a filed block of solder mixed with solder flux to create paste, and reported it as success. I decided to recreate this, and in the process discovered that it is much easier than i thought. And the bonus is that working with the pre-tinned pcbs is so much easier, soldering times are now significantly reduced.
WARNING: THIS PROJECT INVOLVES FILING SOLDER - WHICH IS AT LEAST 40% LEAD. WORK IN WELL VENTILATED AREA AND WEAR A FACE MASK AND GLOVES. ALSO MAKE SURE LEAD DOES NOT END UP IN FOOD.
Also read this: http://en.wikipedia.org/wiki/Lead_poisoning
What you will need:
1) Solid Solder - 50-50 or 60-40. You can use solder that has flux in it - as long at it is NOT acid based flux which will corrode your components
2) A medium to fine file - the finer the file - more work but better quality paste
3) Solder Flux - also called "solder paste" but do not confuse this with real solder paste. Make sure it is not acid based for intended for soldering! Radio shack sell some of this stuff.
4) a toaster oven, fire, or oven.
This instructable has 12 steps.