Soldering

[cccpro]

Hello: I need a few pointers on soldering. What type of flux should I use? I have seen some fluxes but they are not labeled acid or non-acid. Should I tin the iron - the solder seems to flow better from the iron. Suggestions? Thanks.

[TomDiehl]

Basics of soldering: Clean the metal parts to be joined using some form of abrasive. My favorite is an old style typing eraser (looks like and is sharpened like a pencil) and buff the area to be soldered shiny. Heat the iron and (VERY important) keep the tip clean. A small bubble of solder on the tip will help with the heat transfer. Don't touch the cleaned area and join the pieces together. Remember, you won't be able to hold the pieces together with your fingers (HOT), so if necessary, have something to hold them with so you don't need to touch them. Very sparingly, apply flux (don't let the label fool you, ALL fluxes are acids) Paste or liquid flux is a matter of personal preference, so experiment with both to see which you prefer. I use liquid flux in a needle point bottle for rail feeder to rail joints, just as an example. When the iron is hot, touch the solder to the tip to get a small bubble of melted solder on it, then touch this to the joint. The flux should vaproize in less than a second. Do NOT breathe these fumes or get them in your eyes (acid, remember). As soon as the vapor stops coming off the joint, touch the solder to the metal (not the iron tip) and apply just enough to make a good joint. Don't believe the old adage "The bigger the blob, the better the job." Only use enough to make a good joint. Remove the iron and let the joint cool. The iron should only be on the joint for a couple seconds total. When the joint cools, clean the flux residue off with a stiff plastic or wire bristle brush. Tip cleaning is best done with a wet sponge. Most soldering iron stands have a tray for a sponge for just this reason. Wipe the tip of the iron after every joint to remove the flux residue. Then place it back in the saftey stand.

[cacole]

You should use only resin flux or resin-core solder for electronics. Small diameter solder is easier to use, too.

Melt a very small amount onto the tip of your soldering iron to help with heat transfer to the material being soldered. Hold the iron to the material and then touch more solder to the iron, working it as close as possible to the area where the iron touches the material. It may take one second or less for the solder to begin melting, depending on what is being soldered and the wattage of your iron. A small wattage iron will cool rapidly when touched to rail and will take longer to recover than a high wattage iron.

[cccpro]

QUOTE: Originally posted by TomDiehl

Basics of soldering: Clean the metal parts to be joined using some form of abrasive. My favorite is an old style typing eraser (looks like and is sharpened like a pencil) and buff the area to be soldered shiny. Heat the iron and (VERY important) keep the tip clean. A small bubble of solder on the tip will help with the heat transfer. Don't touch the cleaned area and join the pieces together. Remember, you won't be able to hold the pieces together with your fingers (HOT), so if necessary, have something to hold them with so you don't need to touch them. Very sparingly, apply flux (don't let the label fool you, ALL fluxes are acids) Paste or liquid flux is a matter of personal preference, so experiment with both to see which you prefer. I use liquid flux in a needle point bottle for rail feeder to rail joints, just as an example. When the iron is hot, touch the solder to the tip to get a small bubble of melted solder on it, then touch this to the joint. The flux should vaproize in less than a second. Do NOT breathe these fumes or get them in your eyes (acid, remember). As soon as the vapor stops coming off the joint, touch the solder to the metal (not the iron tip) and apply just enough to make a good joint. Don't believe the old adage "The bigger the blob, the better the job." Only use enough to make a good joint. Remove the iron and let the joint cool. The iron should only be on the joint for a couple seconds total. When the joint cools, clean the flux residue off with a stiff plastic or wire bristle brush. Tip cleaning is best done with a wet sponge. Most soldering iron stands have a tray for a sponge for just this reason. Wipe the tip of the iron after every joint to remove the flux residue. Then place it back in the saftey stand.

[Blind Bruce]

As an old time solderer, I offer the following things to add to those already mentioned.
I agree that all fluxes have acid but the ones that are suitable for electrical work have much less of it and utilize rosin in its place. So be sure that your flux type is rosin.
Some people will tell you that the solder itself has a rosin core and therefore, additional flux is not necessary. This is only true for solder that is less than 2 years old as the flux activator deteriorates with age. Also the amount of flux available in small diameter solder is minimal at best.
The two second rule is very true. If your joint will not melt the solder in that time, use a higher wattage iron.
BB

[cccpro]

QUOTE: Originally posted by Blind Bruce

As an old time solderer, I offer the following things to add to those already mentioned.
I agree that all fluxes have acid but the ones that are suitable for electrical work have much less of it and utilize rosin in its place. So be sure that your flux type is rosin.
Some people will tell you that the solder itself has a rosin core and therefore, additional flux is not necessary. This is only true for solder that is less than 2 years old as the flux activator deteriorates with age. Also the amount of flux available in small diameter solder is minimal at best.
The two second rule is very true. If your joint will not melt the solder in that time, use a higher wattage iron.
BB

I have a flux with zinc chloride from Bernz-a-matic. Is that OK for track & wiring? Thanks so much for the info.

[TomDiehl]

Any type of flux should work OK for track and wiring. The most important thing to remember is to remove the residue after it cools.

[orsonroy]

QUOTE: Originally posted by cacole

You should use only resin flux or resin-core solder for electronics. Small diameter solder is easier to use, too.

Not true at all. In the electronics industry, we mostly use coreless solder, and even silver solder for some applications.

But as advice to beginners, definitely use 60/40 rosin core solder WITH added flux to the work. Makes life a whole lot easier, especially if using a general-purpose iron and tip.

[cccpro]

QUOTE: Originally posted by orsonroy

QUOTE: Originally posted by cacole

You should use only resin flux or resin-core solder for electronics. Small diameter solder is easier to use, too.

Not true at all. In the electronics industry, we mostly use coreless solder, and even silver solder for some applications.

But as advice to beginners, definitely use 60/40 rosin core solder WITH added flux to the work. Makes life a whole lot easier, especially if using a general-purpose iron and tip.

Makes sense. Is flux containing zinc chloride, from Bernz-O-Matic OK? Thanks.

[Blind Bruce]

ABSOLUTELY NOT!!! That flux will appear to solder well but in a few years , the joints will turn white and separate. No amount of resoldering will correct the problem. That flux is designed for NON electrical use such as copper water pipes.
I ran across a Heathkit audio amplifier that was soldered with zinc chloride and it was unrepairable. It was one of there mose expensive kits too!!
BB+

[cccpro]

QUOTE: Originally posted by Blind Bruce

ABSOLUTELY NOT!!! That flux will appear to solder well but in a few years , the joints will turn white and separate. No amount of resoldering will correct the problem. That flux is designed for NON electrical use such as copper water pipes.
I ran across a Heathkit audio amplifier that was soldered with zinc chloride and it was unrepairable. It was one of there mose expensive kits too!!
BB+

Thanks for the heads up!

[trollw]

A few things to look for 'after you have soldered it':
1) The cooled solder should be shiny - if it is dull, one of pieces being soldered may have moved while the solder was cooling - redo the joint
2) If the solder is in a blob, you probably don't have a good joint - it should be apparent that the solder has flowed into the spaces between the items being soldered and should have smooth transitions around the pieces
3) If you are having trouble getting the pieces to solder, tin each of the pieces - apply flux to the area to be soldered, touch the iron to the piece where the flux is, then apply solder to the piece and the solder should flow onto the surface of the piece . If you get too much or you are concerned that you will not be able to get the pieces to mate properly - after the solder melts and flows onto the piece, wipe the area with a damp rag as soon as you remove the iron - there should not be any solder buildup left on the piece but it will still be shiny where the solder flowed 'into' the piece. This area will then take solder much easier when you attach it to other pieces. I ALWAYS tin wires before I twist them together.
4) When making an electrical connection: soldering a feeder to the side of a rail or soldering 2 sections of rail together are the only times when it is proper to solder without a separate mechanical joint (i.e., twist wires together before soldering them).The joints should always have a good mechanical joint before using solder to ensure that there is a good electrical joint - if the two wires won't stay together without being held, 'the joint ain't good enough'.

[Blind Bruce]

My leearned friend from the great state of Texas makes some very good points. Only the part about tinning wire before twisting needs clarification. Yes, tin solid wire before twisting but . I personally, prefer to twist stranded wire before soldering. The strands will bind closer together without the tinning solder and will become a stronger joint.
BB

[trollw]

Good catch, BB. That is, indeed, a good way to get a good joint between two stranded wires. My training in soldering comes from designing and building radar systems for the military. That training says to twist the wire strands on each wire independantly so they don't birdcage, tin each wire, bend the tinned end of each wire into a 'U', hook the 'U's' together, crimp the U's down tight on each other, then solder them together - the wires will break before the joint comes apart.

By the way, the 'belt and suspenders' method of attaching stranded wires to screw terminals is to twist the end of the stranded wire so it won't bidrcage, tin the stranded wire, bend the tinned end into a U and place around the screw shank (threaded portion of the screw). The end of the tinned portion of the wire should extend past the head of the screw and should be on the side of the screw such that as you tighten the screw, the head is tu;rning toward the end of the wire ( in the US with standard thread rotation, this means the insulated part of the wire is on the left side of the screw and the end of the wire is on the right (assuming that you are looking down on the head of the screw and the wire coming into the screw from the same side of the screw that your body is on. Using needle nose pliers, crimp the end of the wire toward the insulated portion of the wire so it circles under the screw head (ideally the wire should wrap around the screw threads with slightly less than one full turn - thus the wire end will be under the screw head). Then tighten the screw. You won't have any of those cute little hairs of wire sticking out that always tend to touch something that they shouldn't.

[TomDiehl]

A minor correction to the above, it's ROSIN core or flux, not resin.

[cccpro]

Thank you for all the info. I am having a little problem having the solder "flow" into the joint. I am using a "pistol" soldering gun, 140/100 watts, rosin core solder. Would one of the thinner types of solder I noticed at Radio Shack work better. Thanks again for the info.

[selector]

Possibly, but it is not likely the solder. Are you certain that you are heating the rail enough? If you touch the inside of the joint/joiner interface, and keep the tip there for a slow count to three, and then touch the solder wire to the outside of the interface immediately as you withdraw the iron, you should get an instant solder flow.

[Anonymous]

If you're using one of those guns (I do for some jobs) make sure the tip is securely in place. A while back I thought my trusty Weller was dying of old age. Turns out the set screws that hold the tip in had worked loose.

Cheers,

Ed