On Aug 3, 5:36*pm, Bob Engelhardt wrote:
This is soldering flux that has powdered solder in it. *You apply it to
the joint, heat, & apply solder. *Just like you do for regular flux. *So
why use C-flux?

It's not pre-tinning, as that means wetting the joint surfaces before
assembly.

And if the C-flux isn't applied to the whole joint, the whole joint
isn't going to be wetted, just like regular solder.

The Rector Seal web site says "When heated, it reduces the surface
tension in the joint and allows the solder to flow easily and uniformly
into the joint." *Which is what regular solder does.

What am I missing?

Thanks,
Bob

Hi, Bob.
We use solder paste to solder surface mount components to circuit
boards. Both leaded solder and lead free solder. The solder paste will
melt(fuse) at slightly lower temperature than solid solder. There is
no advantage for us, except when doing boards with components on both
sides. The first side is done and soldered in a oven, then turned over
and paste applied to the pads and that side's components are mounted.
Then the board goes back through the convection oven to melt the
solder paste for the new components. If the oven profile is just
right, the paste will melt, but the solid solder on the bottom will
not melt.

However, if things are not quite right, capillary action will still
hold the bottom components. If the component is too heavy and the
solder melts, we loose the component and have to add it by hand.

In your case, I don't know if there is any advantage to solder paste.
Just a lot more expensive.

Paul