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From: Ecnerwal on 4 Jul 2010 16:30
In article
<none-0307101819110001(a)dialup-4.231.175.251.dial1.losangeles1.level3.net
>,
none(a)given.now (Joe) wrote:

> A couple of days ago I did a small repair to an electronic timer. It just
> need a bit of solder to reconnect a wire.
>
> I had a devil of a time with that small repair, the solder just didn't
> want to flow over the wire and onto the pad on the PCB.
....
> Is there a definite life for unused solder?

I've got a roll or two of Multicore that's easily 3 decades old, and
still works fine. Now, when doing repairs, you are often up against a
filthy joint and the crufty remains of the flux last used, plus any dirt
or corrosion it's attracted since it was made - and there just might be
a layer of varnish or the like applied to the thing post-assembly to
additionally complicate life, and none of those will help a bit.

If you can't make it clean mechanically (the preferable option, IMHO),
additional flux might help.

--
Cats, coffee, chocolate...vices to live by
From: Meat Plow on 5 Jul 2010 09:57
On Sun, 04 Jul 2010 07:28:40 -0700, Smitty Two ǝʇoɹʍ:

> In article
> <none-0307101819110001(a)dialup-4.231.175.251.dial1.losangeles1.level3.net
>>,
> none(a)given.now (Joe) wrote:
>
>> A couple of days ago I did a small repair to an electronic timer. It
>> just need a bit of solder to reconnect a wire.
>>
>> I had a devil of a time with that small repair, the solder just didn't
>> want to flow over the wire and onto the pad on the PCB.
>>
>> A little while later, it occurred to me that maybe the problem was that
>> I had used some old solder - about a foot or so are remaining on
>> probably a 5 or 10 foot spool.
>>
>> The big Aha! came when I realized that all during that soldering
>> attempt, there was absolutely no odor of rosin flux.
>>
>> Questions:
>>
>> Are there any obvious ways to tell if old solder has lost its flux,
>> other than trying it out on say, soldering some scrap wire?
>>
>> What happened to the rosin core of that solder? It doesn't look like
>> the end was left open.
>>
>> Is there a definite life for unused solder?
>>
>> --- Joe
>
> I'm the militant s.e.r. liquid flux advocate. If you're going to solder
> at all, especially to make repairs, you *need* liquid flux, period. One
> of these days I'll make a video for youtube demonstrating how flux
> facilitates soldering. I don't care if you think you've been soldering
> fine without it for 50 years, if you don't use it, you have no idea what
> you're missing.

Never used anything but rosin core flux except to solder copper pipe.
Maybe you could 'explain' what it is I might have been missing over the
last 30 years?
From: William Sommerwerck on 5 Jul 2010 10:11
>> I'm the militant s.e.r. liquid flux advocate. If you're going to solder
>> at all, especially to make repairs, you *need* liquid flux, period.
>> One of these days I'll make a video for youtube demonstrating
>> how flux facilitates soldering. I don't care if you think you've been
>> soldering fine without it for 50 years, if you don't use it, you have
>> no idea what you're missing.

> Never used anything but rosin core flux except to solder copper
> pipe. Maybe you could "explain" what it is I might have been
> missing over the last 30 years?

I've never had trouble "wetting" an old joint with a bit of new rosin-core
solder.


From: Jeffrey D Angus on 11 Jul 2010 14:39
Smitty Two wrote:
> So don't take my word for it. Go to any manufacturing
> facility that does any hand soldering, and you'll find
> a little bottle of flux at every workstation. Try it
> yourself and you'll see why.

Oh yeah, I keep one on each active bench here.

Jeff


--
�Egotism is the anesthetic that dulls the pain of stupidity.�
Frank Leahy, Head coach, Notre Dame 1941-1954

http://www.stay-connect.com
From: Jeff Liebermann on 11 Jul 2010 16:20
On Sun, 11 Jul 2010 10:46:33 -0700, Smitty Two
<prestwhich(a)earthlink.net> wrote:

>What you may have been missing is the speed, ease, and quality of
>soldering with liquid flux vs. relying solely on the resin core.
(...)

Nice list.

I've been soldering for about 50 years and only recently have started
to use bottled flux. I quickly tin both ends of whatever I'm
soldering first. That leaves a little flux on each end. If done
correctly, I haven't found the need for liquid flux for large
components. Tinning and intentionally leaving flux on the components
requires more skill than is commonly available and isn't suitable for
tiny components.

I've recently been dealing with badly reflow soldered BGA chips,
usually inside laptops. The trick is to reflow the solder bumps
(usually with a hot air gun) without moving anything. Without a
wetting agent (flux), the solder bump and PCB solder pad will not
reflow together. Getting the flux to flow under the BGA is a major
problem. My current method is to use a bent needle syringe, but that
only works for small BGA's. Spraying with an atomizer and air hose
works well, but also makes a huge mess.

For soldering big heavy lugs and cables, flux is also required. The
small amount of flux (about 5%) found in common solder is
insufficient. By the time the solder melts and flows into the wire,
all the flux has been burned off. The only choice is to add more
flux. To avoid the drippy mess, I use rosin paste flux for lugs and
cables.

Another headache is mixing leaded and unleaded solder. I have
separate irons and solder rolls for each. I can mix solder types and
get a usable joint, but it takes more effort and often looks more like
dross than a proper connection.

There's also such a thing as defective solder. I once bought a small
roll of "electronic solder" at a hardware store that was awful. The
flux would sputter and spray small balls of solder everywhere. I
managed to do the soldering only to find that nothing less than
acetone would remove the flux residue. Alcohol wouldn't touch it.

More on flux:
<http://yarchive.net/metal/soldering_flux.html>

Make your own flux:
<http://www.instructables.com/id/Make-your-own-Eco-friendly-soldering-flux/>
I've done this with violin rosin and pine tree pitch. It works.
Unfortunately, it smells like a burning forest, causing everyone in
the lab to panic.

As for the old solder, I haven't had much trouble with flux loss with
rosin core solder. I have several rolls "liberated" from a previous
employer that are easily 20 years old, and are still in use. That's
not the case with acid core solder (not suitable for electronics). My
roll of acid core plumbing solder looks corroded. The steel reel on
which it's rolled is also corroded, indicating that the acid flux is
somehow leaking and attacking everything nearby. The OP's solder
collection is rosin, so flux loss should not be a problem.


--
Jeff Liebermann jeffl(a)cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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