lab flux type for diff electrical connection purposes

[coppercone2]

I use 951 for very clean things, like fresh parts with nice PCB
https://www.kester.com/DesktopModules/Bring2mind/DMX/Download.aspx?Command=Core_Download&EntryId=3764&language=en-US&PortalId=0&TabId=96

and 186 for everything else
https://www.kester.com/DesktopModules/Bring2mind/DMX/Download.aspx?Command=Core_Download&EntryId=3764&language=en-US&PortalId=0&TabId=96

I am particularly interested in thermal performance, like if you need to over-heat your iron to do a big joint. I noticed 186 works well with this, and it says that its good for high temperature, but there are no metrics.

Are there even better fluxes stable at higher temperatures?

Also,

Is it remotely imaginable for you to think that using the same flux pen on different solder compositions like lead free and lead bearing can slowly transfer some kind of soluble ions or dust between the irons over a long time period?

[mmagin]

I am particularly interested in thermal performance, like if you need to over-heat your iron to do a big joint. I noticed 186 works well with this, and it says that its good for high temperature, but there are no metrics.

This is one reason I really like having a iron that has lots of power and good temperature control, like my 30 year old Metcal with one of the bigger chisel tips

[GreyWoolfe]

I am particularly interested in thermal performance, like if you need to over-heat your iron to do a big joint. I noticed 186 works well with this, and it says that its good for high temperature, but there are no metrics.

This is one reason I really like having a iron that has lots of power and good temperature control, like my 30 year old Metcal with one of the bigger chisel tips

I can use my Metcal to solder a PL-259 connector on coax with a 3.2 mm chisel tip without effort.

[David Hess]

Most soldering can be made easier by using a shorter and thicker tip for lower thermal resistance and higher thermal capacitance.  I have never had problems with PL-259s on my ancient Weller Magnastat irons with a short thick tip.

[nanofrog]

Both of those fluxes will work properly to 500C IME (500C is the max temp on my Quick 861DW). And these two particular fluxes are also compatible with one another, so no issues there. 

If the flux is turning into a dark baked on crud, then you're staying on the joint too long. Same would happen with any other flux that's heated too long.

As others have mentioned, if you're having to crank your iron to make high demand joints, then you should:

• make sure you're using a tip with sufficient thermal mass
• check the actual tip temp vs. set temp, and calibrate the station if necessary

Otherwise your iron just isn't really up to the job and you're running a risk of damaging the PCB by cranking the temp (i.e. time to get a better station).