It won't be long until we in the northern hemisphere are complaining about the snow and the cold, but right now, it is all about the heat!
In particular about the heat that is needed to reflow high melting point (HMP) alloys. These are generally high-Pb alloys that see very high operational temperatures. They are used for applications such as automotive under-hood or down-hole drilling equipment .
If you try and use a flux that is not formulated to withstand higher (greater than 220C) temperatures, your flux will burn off and char and never get a chance to really do its job.
So, the key is to use a flux that is specially formulated to activate at higher temperatures, like our 807HMP used in our flux cored wire.
It is ROL1 but has only 650 PPM of halogens. (AUTHOR'S NOTE: After further testing via oxygen bomb, the flux classification for the CW-807 has been found to be ROL0. Added 11 June 2013).
You may also want to consider an alloy with a small amount of indium in it (such as Indalloy #164 which is 92.5Pb 5.0In 2.5Ag) since indium is well known for its thermal fatigue resistance. This alloy works very well with the 807HMP.
Choosing the right alloy and the right flux are key to keeping your cool!