# Soldering gun.



## prr1361(inactive) (Nov 11, 2009)

Ok rather silly question. When buying a soldering gun, how many watts should I look for? The work im doing is mostly On postwar items


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## Dave Sams (Nov 24, 2010)

I recently bought a Radio Shack 15/25 watt iron.

So far, I've been able to solder anything I've tried.


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## servoguy (Jul 10, 2010)

You really need two soldering irons. A solder gun of 250 watts is good for soldering anything that needs a lot of heat. However, it is way overkill for soldering wires. A smaller iron like the one Dave recommended is much better for soldering wires and semiconductors.


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## prr1361(inactive) (Nov 11, 2009)

Ok, how about a 40 watt iron is that sufficient or is that too much for wires?


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## NIMT (Jan 6, 2011)

40 watt is still on the high side! The wire can take the heat but the insulation and what ever your connecting it too might not like it. With it being that hot you have to be very quick as not to destroy parts. 25 watt is more of a norm for wiring on the O's.


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## prr1361(inactive) (Nov 11, 2009)

Ok thanks. I appreciate all the advice


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## gunrunnerjohn (Nov 10, 2010)

I've been using a 100/140 watt Weller soldering gun for more years than I care to remember. It's used for all the "bulk" soldering like track, etc. For wiring, I have a Weller temperature controlled soldering station. 

FWIW, it's not the wattage capacity of the soldering iron that will damage things, it's the heat. My 60 watt soldering station works for the finest circuit boards, because the heat is controlled, only enough power to do the job is used.


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## Big Mike (Dec 2, 2011)

I just got a weller form lowes, it takes three AA batterys, I didn't think it would do so good ,but it works great on the small stuff, hot in 15 seconds, I get just about anywere with it,problem is ,it sucks up batterys,so I got a few nickle metel hydride re-chargeables,its all good now.

O, I also have a 500 watt monster from Mac Tools for the BIG stuff,I think I could melt lead with this thing LOL!.........mike


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## CW Burfle (Jan 11, 2012)

gunrunnerjohn said:


> I've been using a 100/140 watt Weller soldering gun for more years than I care to remember.


I use a 100/140 Weller gun for most of my work too. Folks looking for soldering guns might like to know that the Weller guns made today are a bit different than the gun I have (and gunrunnerjohn probably has too). The older guns were 100/140 watt, and had little nuts that held the tip in place. 
More recent guns are 140/100 watt, and use set screws to hold the tip. 
In my experience those set screws don't work very well, and must be retightened frequently. 
In my area the older guns are frequently found in garage sales for about five to ten dollars. Our local used tool store gets fifteen to twenty.


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## prr1361(inactive) (Nov 11, 2009)

Thanks for all the advice. What advice can anyone give for soldering and desoldering? I know it sounds very dumb and it would be much easier to have someone else do it. But I want to learn how to do it myself


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## servoguy (Jul 10, 2010)

For soldering, make sure everything is clean. If necessary, polish the things to be soldered with a Dremel tool and a sanding disc or wire wheel. Use rosin core solder. To desolder, you can use solder wick (available at Radio Shack, although they call it something else) or a solder sucker. I don't know if RS has solder suckers or not. 

If something doesn't take solder, it is either not hot enough or it is dirty.

Be careful soldering things that are close to something that is plastic. For example, the connections on a 1122 switch usually are not good because of corrosion, but you have to be quick with the soldering iron to avoid melting the plastic.


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## gunrunnerjohn (Nov 10, 2010)

RS has solder suckers, and for bigger jobs they're really the way to fly.


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## Dave Sams (Nov 24, 2010)

servoguy said:


> If something doesn't take solder, it is either not hot enough or it is dirty.
> 
> .



When I am working on something that has been soldered previously, I apply a little (keyword little) rosin flux from Radio Shack. It makes all the difference.

It works well on my old cruddy 027 track. I can wire brush the daylights out of it and I find a little flux helps.


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## newB (Feb 3, 2011)

Here's a tip for you. If you ever come across rosin-core solder that is NOT marked ROHS, use it! You'll thank me later.

Pre ROHS (old style lead/tin) solder flows nice, melds at a slightly lower temperature, and is very forgiving (it's easy to do a good solder job).

ROHS solder (modern lead-free solder) doesn't flow as well, needs a higher temperature to melt, is harder to make a good solder joint, and has a 'lifetime'. By 'lifetime' I mean that the soldered joint will eventually fail due to the deterioration of the tin in the solder from 'tin pest'.

Lead in solder stabilizes the tin preventing 'tin pest'. A pre ROHS (lead/tin) soldered joint lasts forever.

The tin in ROHS (lead-free) solder will eventually deteriorate. It may take a few years or a few hundred years. But it will happen. I once saw ROHS solder, unused and still on the spool, that was already deteriorating.


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## servoguy (Jul 10, 2010)

The military will not allow RoHS solder due to reliability problems. There is a lot of military electronics that needs to have a service life exceeding 40 years, and the electronics is often in very bad environments. I think the whole RoHS idea is stupid. This is the opinion of an electrical engineer with 48 years of experience doing engineering.


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## gunrunnerjohn (Nov 10, 2010)

I have a couple of 1 lb spools of solder that was made before it was turned into crap.


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## Xnats (Dec 5, 2010)

This stuff is pretty interesting, thanks guys.
What is the census with silver bearing rosin core?


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## gunrunnerjohn (Nov 10, 2010)

Silver bearing solder usually has a few percent silver, but still has lead and tin. I have a small spool of it left over from when I used to fix older Tektronix test equipment. They had ceramic barrier strips that needed silver bearing solder not to deteriorate when you soldered them.


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## Dave Sams (Nov 24, 2010)

newB said:


> Here's a tip for you. If you ever come across rosin-core solder that is NOT marked ROHS, use it! You'll thank me later.
> 
> Pre ROHS (old style lead/tin) solder flows nice, melds at a slightly lower temperature, and is very forgiving (it's easy to do a good solder job).
> 
> ...



This is what I use:




















BTW I was soldering incorrectly for too many years until I encountered this forum!


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## gunrunnerjohn (Nov 10, 2010)

I use 60/40 as well, but it's .028" in diameter. Mine is the multi-core rosin, works fine for what I use it for.


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## servoguy (Jul 10, 2010)

The 60/40 solder is 60% lead and 40% tin. It should work just fine.


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## Dave Sams (Nov 24, 2010)

It works well.

A number of my old connections were soldered using plumbing flux.

If I put a little rosin flux on it, and apply a little more solder for the new wire, I end up with a nice shiny connection.


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## gunrunnerjohn (Nov 10, 2010)

If you used plumbing flux, you need to THROUGHLY clean those joints! Plumbing flux is acid based and will corrode those connections. Just putting rosin on them isn't sufficient.


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## newB (Feb 3, 2011)

Some random thoughts, in random order. I know solder and I hope these help you...

1) Never ever use acid (plumbing) flux for electronics soldering. If you do, the soldered joint will still look good and will work good for a while but some of that acid residue may still be in there. The residue will act as an electrical insulator, increasing the electrical resistance of your soldered joint. Need I say more?

2) Pre ROHS lead solders usually have one or two numbers associated with their alloy content. The 1st is usually the tin and if there is a second, it's the lead. So '60/40' is 60% tin and 40% lead. '63/37' is 63% tin and 37% lead. And just '63' is shorthand for '63/37'. Get the idea? 

3) With pre ROHS solders, the more tin it has (or the less lead), the lower the temperature it melts. Lower temperatures mean easier soldering and lower potential heat damage to adjacent parts.

4) I wouldn't bother trying to use '50/50' solder for electronics soldering. It melts at too high a temperature. '50/50' is usually used for plumbing.

5) Solders sometimes don't actually say 'tin' or 'lead' on the labels. They might say 'Sn' (for tin) and 'Pb' (for lead). These are their symbols from the periodic table. 

6) Flux core silver solder is really fantastic stuff but it's going to melt at a higher temperature than 60/40. If I were to use it, I'd be real careful and use heat sinks to cool adjacent components while soldering.

7) Not all brands of solder are equal. It's kinda like paint. For a solder that flows nice and even, you'll pay more. 'Kester 44' brand solder used to be the cat's meow of solders for electronics work. But I don't know if that's true anymore. I don't even know if they still make it.

8) I use 63/37 for electronics soldering. It melts slightly lower than 60/40, and has special properties that I don't need to go into at this point.

9) I find that thin wire solder is easier to use than thicker stuff. I really like 0.025" diameter. But everyone has their own preferences...


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## Dave Sams (Nov 24, 2010)

What is the meaning of ROHS?



FWIW, I know what is said about acid flux.

However, I have several hundred joints on my layout. Some were done almost 25 years ago.

So far, no failures.

I have corrected my ways and use only the rosin flux.

For some reason, the tips of my irons are lasting longer.

Go figure.


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## servoguy (Jul 10, 2010)

You are right newB. I got it backwards: http://en.wikipedia.org/wiki/Solder

Copper tips are dissolved by the solder. Most good irons use iron tips which don't dissolve.


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## newB (Feb 3, 2011)

Dave, ROHS = 'Reduction Of Hazardous Stuff'. In other words, get the lead out of consumer electronics.

You can google it for more details. 

And as to your acid flux soldered joints, I'd just leave them be. Should you have problems in the future, you know what to do.


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## Xnats (Dec 5, 2010)

This is a great thread guys. I deal primary in N and Z scale stuff and switched to the silver after having problems with something I bought at radio shack. What ever I bought, did not conduct and I threw it away. I only bought the silver because I know silver conducts. The kids there were no help and nothing was labeled for electronics or PC circuitry. I was going to give a try at soldering up some SMD leds when they arrive. What would the recommendation for these be? Should I ditch the silver and use the 63/37 if I can find it?
Thanks


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## NIMT (Jan 6, 2011)

I use 62/36/2 .015dia for all of my fine decoder and super small stuff!
62% Tin, 36% Lead, 2% silver
It flows well but not to well as to bridge small gaps in circuit board tracings!


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## gunrunnerjohn (Nov 10, 2010)

If I didn't have a ton of the 60/40 multi-core solder, I'd probably opt for some of the 63/37. A small roll of the silver bearing solder would probably be useful, the stuff I have is a bit too large in diameter for PCB work. It was for when men were men and test equipment had tubes!


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## Xnats (Dec 5, 2010)

lol John. Thanks guys, everyone actually, I learned a lot here today :thumbsup:


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## newB (Feb 3, 2011)

Xnats said:


> This is a great thread guys. I deal primary in N and Z scale stuff and switched to the silver after having problems with something I bought at radio shack. What ever I bought, did not conduct and I threw it away. I only bought the silver because I know silver conducts. The kids there were no help and nothing was labeled for electronics or PC circuitry. I was going to give a try at soldering up some SMD leds when they arrive. What would the recommendation for these be? Should I ditch the silver and use the 63/37 if I can find it?
> Thanks


I had to read this twice... You want to solder SMD LEDS. like the little 2x0.8 mm guys?!?

You do realize that these are meant to be handled by machine? That is why they come in the goofy plastic packaging. The machine would pop the components out of the packaging, and insert them onto the circuit board. When the board is fully populated, it would solder it.

Hand soldering these could be considered precision soldering, on a tiny scale.

If I had to hand solder these, I would expect a high failure rate. These guys are so small that I would have to solder quick, before the heat cooks them. Just a few seconds is enough to ruin them. I'd also use the lowest temp professional solder I can find/afford, and the thinnest too. Maybe 63/37 0.015 dia. or so. (Professional solders have specs that they adhere to. If the spec says that it melts at xxx degrees, you can bet that every inch of solder on that roll will melt at exactly xxx degrees. Did your Radio Shack solder even have specs?) I'd also use a professional soldering iron with variable heat, and experiment with the settings to get a good solder joint that doesn't cook the LED. I'd also have the smallest/pointiest tip on the iron. And I'd be doing all this while looking thru a magnifier.

I may have answered more than you asked, and I told you what 'I' would do. It's up to you to figure out how 'you' want to do it. Best of luck!


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## Xnats (Dec 5, 2010)

lol New, I know, I know. I appreciate the advise, this is virgin turf for me. I have done a lot of studying and know I need a jig to hold it with a means to disperse heat. Kids have videos up showing the use of flux to draw the solder. At less then 6 bucks shipped for 12, I'm not in the hole if they all fail. They are 2.7x2.0 so they are a little bigger  Currently I have .015 62/36/2 and radio snacks smallest pencil, we'll see what happens . I was scared when you said the silver needs more heat to melt but at 62/36 I'm near the low temp rating, I think. We'll see :laugh:
I have no idea what the old stuff was, I was so mad it went straight to the trash. Then again maybe I had cold solders on every single one on the powered rail connecters I was working on  All the ones I did with silver worked perfect


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## gunrunnerjohn (Nov 10, 2010)

I've hand soldered tons of SMD LED's as well as other SMD parts. With a fine tipped temperature controlled soldering iron, I've had zero failures of the LED's or any other parts. They're not nearly as fragile as is being made out.

One way is to glue them down before you solder them if you're doing discrete wiring. I typically use #32 wire wrap wire for doing this kind of work, it's not like you need a lot of current capability.


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