[sdiy] Larry's MOTM/diy/AH pages

[KA4HJH]

>> The melt temp seems to be lower.  It goes on very easy.  However, being able
>> to wash is the prime advantage.
>
>Probably it just seems lower since the flux is much more
>agressive.  I guess I'm just too old .... ;^)

I didn't notice much of a difference myself. I certainly didn't notice that
the alloy was different, which is is the only thing that would change the
melting point of the solder itself.

This reminds me of something that always bugs me. I've never seen a book on
electronics/soldering that bothers to mention what a difference some clean
solder and fresh flux makes. Most books on the "art" spend most of their
time preaching about "thoroughly heating the joint", which is funny because
putting some fresh solder (with its flux) on a joint will get everything
hotter faster the best physical contact you can possibly contrive between
the tip of the iron, the board, and the part being soldered. Yet this is
precisely what they always tell you NOT to do! There is a WRONG way to do
this and it would be easy for a beginner to mess up at first (no sense
learning any bad habits at the start, either). But done right it will get
you the best possible joint and reduce the heating time to boot.

Whenever I'm desoldering I always throw a blob of fresh solder on there
first. Amazing how much faster and easier it all comes off after that. I've
had really old solder refuse to melt with a 250W gun until I put fresh
solder on it! This is also useful when working with untinned boards (like
homemade boards). You'll have a lot fewer questionable-looking joints. Give
the flux time to clean the copper!

Of course I'm using a Weller WTCP iron (what else?). 45W, thermostatically
controlled and worth every dime I paid for it (I just replaced the tip for
the first time). I've working with some mighty big heat sinks using that
iron and this technique. Stuff that you'd never get with a cheap pencil
from Radio Shack. And I've never fried a component with heat and I don't
use a sink (tinning the shield on coax doesn't count--I have a special
alligator clip that I use just for that).


>    Being a big user of Organic solder myself, I must emphasize that
>when you use organic core flux (I use Kester 331), you MUST! clean what
>you solder.  When you solder wires, the flux will wick up the wire,
>under the insulation, where you cannot get at it, and it will corrode
>the wires, no doubt about that.  Keeping the two solders straight can be
>a big pain in the neck.  I sometimes grab the wrong roll.

I just remember that the solder with the red label is the potentially
dangerous stuff. As long they don't change the color I think I'll be OK...I
hope.

>And while on
>the subject.  Never mix rosin and organic flux.  You must completely
>remove one flux before using the other, otherwise, you end up with a
>very corrosive MESS!.

Perhaps it would be a good idea to only use the stuff on NEW circuits, not
repairing old ones? (even if there are no water-damagable components on the
board?). Not that I've been tempted to try THAT yet.


>I wish I had taken pictures of the results of
>mixing both fluxes.  The results are extremely dramatic (espesially when
>you also combine a 300AMP power supply in the mix).

Yeah, I'd love to see that. Wish I had pictures of some of the lightening
damage I've seen.


-- 
Terry Bowman, KA4HJH
"The Mac Doctor"