Solder Doesn't Stick

[minions]

I've been trying to solder my guitar wiring with a 25W soldering iron and lead-free, resin core solder. Sometimes it is easy enough, but other times, I find it difficult to make the solder stick to the wires and contacts. The melted solder will stay on the end of the solder wire but when touched to the iron or wire, it will not come off. I've tinned the tips that I'm using as well as cleaned them a few times. Is the solder supposed to stick more easily or is what happens to me what always happens?

Thanks.

[D2o]

Hi minions,

You will not likely fry a pot with 25 watts. As for getting the solder to stick, here is what I do.

I have a 25 watt iron as well - which works just fine, and I like to use the thinnest electronic rosin core solder that I can find.

Make sure that you allow your iron to properly heat up for at least 5 minutes, that you always keep the tip of your iron clean, and that you tin it (melt a thin layer of solder on the tip).

When I am soldering to something like the back of a pot, I lay the side of the tip of the iron on the surface to be soldered to for a good 30 seconds before placing the wires that are to be soldered to it on the surface and then laying the side of the tip of the iron on the wires that are on the surface for another good 30 seconds or so.

Then I press the point of the tip of the iron on the wires, and make sure I've got ample solder to make a huge honkin' glob of solder on a fairly hot surface, so that I have the best chance of getting a good and durable solder connection. I have never damaged a pot doing this - although that could happen with a much more powerful soldering iron, so best stick with about 25 - 40 watts.

Cheers,
D2o

Edit: minions – I was sort of responding to two of your posts at once … I forgot to mention that if you have been trying to solder the same thing a few times and you have not been properly cleaning the old solder away with a solder pump, you sometimes end up with a bit of an accumulation of what looks like a yellowish oily substance – which makes good solder joints difficult.

In case that is what you are experiencing, you can melt and clean off old solder with a solder pump and alleviate your frustration.

[minions]

Oh that's great to hear about the 25W irons. I was getting worried that my pots were already fried.

Also, I'd like to report that I tried what you told me to do, and it worked perfectly.

Thanks so much!

[sumgai]

Weeeelllllllllllllllllll,

Time to don my Professor's Hat, once again.


When heating the back of a pot for soldering purposes, it pays to remember that heat flows into it from the iron only so quickly. If the pot shell can dissipate heat more rapidly than it's coming in from the source, then it will take seriously longer for the shell to become hot enough to melt solder. By this time, the whole shell is more than warm, and depending on the quality of the pot's construction, you may be endangering its innards.

Better to use a higher heat iron (higher even than 40 or 50 watts), or even one of those old-school guns. (The kind usually associated with Weller (the company), and are at least 100 watts.) This way, the heat from the gun's tip flows into the pot shell much quicker than it can be dissipated, thus the solder melts sooner, and thus you are done much sooner. The further regions of the shell are probably still cool, or lukewarm at the most. Less chance of damage that way.

This lesson also applies when soldering to those little "tabs" on an amp's chassis, or even to the chassis itself. In such a case, your 100/250 watt gun is your best friend.... your 25 (or 32 or 40) iron will burn itself out trying to make those kinds of connections.


BTW, that yellow-brownish waxy substance is old flux, from the previous solder job. It should just chip up, but if you want, you can heat it up and then brush it away. Don't be anal about getting every last little bit, just the majority of it will be good enough for the next aplication of heat and solder.


HTH




sumgai

[D2o]

My observations using the 25 watt iron are from my own actual results using the 30 second sequences as described, and it has always worked well and without damage.

Nevertheless, sumgai, as always, makes a good point about the selective application of higher powered soldering guns.

In fact, I have found that taking solder off of pots has been, on occasion, another instance where a high powered iron would have been welcome. Apparently, some types of solder are more difficult to melt than others.

While I have found the soldering method that I have described to work well, if I was a betting man, I would bet on sumgai's advice over my own ... I might even just go and buy me a soldering gun to add to the arsenal.

D2o

[cynical1]

I was taught to melt a bit of solder onto the wire, then heat the surface with the wire and solder laying on the surface. This way it always melted into the connection and I didn't have to fumble as much with the solder, iron and wire...and once the solder melted the connection was made and I could remove the iron without overheating the surface.

Is this practice fundamentally flawed?

HTC1

[newey]

Is this practice fundamentally flawed?

I hope not. That's what I do, too.

I find the lead-free solder considerably harder to work with, and it definitely wants a higher-powered iron.

[D2o]

That’s what I do most of the time, too. Other times I will jerry-rig an alligator clamp to hold a wire in place, if it’s a particularly fussy wire or space.

I may have muddied the issue in this post because I decided to opine on both this post and about minion’s other thread immediately after this thread – the one about frying the pots.

I don’t do any wacky 30 second stuff on anything other than the backs of pots.

D2o

[JohnH]

I use a 25W iron for everything - it's one I bought in 1975 when I was 15, and its nothing special, but it suits me better than any other due to the shape of the handle, the tip and a light thats on it. But its not enough to solder to a pot case, so I never do that in my guitar wiring, instead, I use a tag on the pot shaft, and make a bare ground wire, to which all other grounds can be easily soldered. My pot cases stay neat looking and unsoldered to, and don't get heated.

My general soldering technique is to tin each part, then put them in contact and heat both parts of the the joint with the iron, and feed a little more solder into the junction, making sure it melts on the wires rather than the iron. Then I pull off the iron and hold steady for 10 seconds while it sets. Delicate components get a time limit of 3 seconds to make the joint, then if thats not enough I pull off and let cool for 15 sec or so.

John

[sumgai]

John's method of using a ring terminal around the shaft of the pot is the preferred "best practices" method, for the very same reason he cites: no chance of damage to other components. That said, it's easy to see why factories and others use the pot shell - it's convenient as all get out, and it does the job. The only downside is the risk of damage to the pot.

What are the odds? Not very high. And of course, it depends...... On what size iron you're using, on the type of solder (RoHS-compliant "solder" is not solder. Solder is defined as containing some portion of lead, a key ingredient that's missing from the new stuff.), on your technique itself, and finally, on your attention span. Oh, and whatever Mr. Murphy is doing at that particular time of the day....

From this thread we can gather an idiom: there are two kinds of people in the world - those that make do with whatever they have at hand, and those that use the proper tool for the job. Make of it what you will.

'Nuff said.



sumgai

[Teleblooz]

Jan 1, 2010 23:50:26 GMT -5 sumgai said:

RoHS-compliant "solder" is not solder. Solder is defined as containing some portion of lead, a key ingredient that's missing from the new stuff.

Not so.

Wikipedia: Solder is a fusible metal alloy with a melting point or melting range of 90 to 450 °C (200 to 840 °F), used in a process called soldering where it is melted to join metallic surfaces.

I work at a chip manufacturer. The whole issue of RoHS and Lead-free solder is very present for me on a daily basis. My job entails materials / environmental reporting.

[D2o]

Jan 20, 2010 15:07:07 GMT -5 Teleblooz said:

Jan 1, 2010 23:50:26 GMT -5 sumgai said:

RoHS-compliant "solder" is not solder. Solder is defined as containing some portion of lead, a key ingredient that's missing from the new stuff.

Not so.

Wikipedia: Solder is a fusible metal alloy with a melting point or melting range of 90 to 450 °C (200 to 840 °F), used in a process called soldering where it is melted to join metallic surfaces.

I work at a chip manufacturer. The whole issue of RoHS and Lead-free solder is very present for me on a daily basis. My job entails materials / environmental reporting.

Teleblooz,

Huh! Interesting stuff.

Starting at the bottom of page 3 of this era study report is a discussion of the exemption of lead-free solder until such time as there is sufficient evidence that it will not put the well-being of the public at risk due to five types of failure:

- manufacturing defects ;
- thermal fatigue ;
- tin whiskers ;
- vibration and effects of g-forces ; and
- corrosion

I have no idea if that report is the be-all end-all of reports, but it speaks to what you are saying. One example given is the risk of solder corrosion on PCBs.

Interesting stuff … I didn’t know that.

D2o

P.S. … having said that, I am only guessing, but we’re still stuck with RoHS compliant lead-free here in guitarnutz-land, right?

[betweenthees]

you guys using "pens" or "guns"?

ive been using the gun- has a nice light on it that turns on when you pull the trigger for heat-
plug in and pull the trigger, warms up real fast, but....
My bro swears by the pen, saying that im losing so much persicion with the gun and that i should bite the learning curve and get some patiance.

I keep 2 gauges of solder on the bench- super thin (maybe 22g?) and some med (maybe 18) each have many practical uses when working. thin stuff melts faster and you can more detailed with how much applied. if you need a "chunch" on there (say when grounding to back of pots) grab the thicker stuff.

i keep a wire brush on the bench too, i try my best to keep it cleen (glances over to iron) which it is not right now

just some thoughts on how ive been working