Question About Soldering Technique

[hizzy]

Hi Everyone!

Long time lurker, first time poster! I have a question that could use some clarification. I've recently gotten into electronics because I've been building joysticks for my old Atari 2600, Before buying a soldering station, I watched many on-line tutorials. I've noticed that people use different methods when soldering, i.e twisting wires together, pre-tinning and then joining wires, "western union" joints, etc..., but one thing has me confused. In the video below, the person demonstrating says that, when joining two wires, your solder and the tip of your iron should never make contact. That is, you hold the iron below the wire, heat up the wire, and then bring the solder to the wire, making contact only with the wire and not with the tip at all. He says this around the 3:20 point.



In other videos, like the next one, the narrator says to have  your solder touch the tip of your iron, where the tip and the wire meet. He says this at around the 4:50 mark of the video:




Is one of these methods wrong? Are both correct? This has been bugging me. I want to make sure I'm soldering correctly. Thanks so much for your advice and help!

[suicidaleggroll]

The first presenter is probably just trying to keep people from balling up a bunch of solder on their iron without letting any of it flow through the joint.  It's easier to ensure the solder is flowing through the joint if you're applying heat and solder on opposite sides, though it helps to put a bit of solder on the tip at first to help the heat transfer into the joint.  As long as the solder is flowing through the joint completely, it doesn't really matter what method you use.

[MosherIV]

The general principle is to heat up the parts you are trying to solder and then let the part(s) melt the solder. That way the solder flows over the parts and not ball up on the iron tip.

(This usually causes cable sleaving to shrink/melt)

[hizzy]

The general principle is to heat up the parts you are trying to solder and then let the part(s) melt the solder. That way the solder flows over the parts and not ball up on the iron tip.

(This usually causes cable sleaving to shrink/melt)

Sorry if this sounds very silly, but is it a bad thing should your solder wire make brief contact with your iron's tip when heating up a wire?

Thank you!

[rstofer]

The general principle is to heat up the parts you are trying to solder and then let the part(s) melt the solder. That way the solder flows over the parts and not ball up on the iron tip.

(This usually causes cable sleaving to shrink/melt)

Sorry if this sounds very silly, but is it a bad thing should your solder wire make brief contact with your iron's tip when heating up a wire?

Thank you!

Not at all!  I frequently add just a touch of solder to the tip to encourage heat transfer to the wire.  Not a big glob of solder, just a little bit.  Then I apply the solder to the far side of the joint.

[IanB]

In the video below, the person demonstrating says that, when joining two wires, your solder and the tip of your iron should never make contact. That is, you hold the iron below the wire, heat up the wire, and then bring the solder to the wire, making contact only with the wire and not with the tip at all.

I think this is a very idealistic view. It may be true in theory, but I doubt anyone really solders this way.

In order for heat to flow from the iron to the joint there needs to be a "bridge" of solder across the gap to conduct the heat (otherwise the iron will be hot, the joint will be cold, and you will never get the solder to flow). What most people do is to touch the end of the solder wire in the gap between the iron and the joint to start the heat flowing, and then move the wire over the rest of the solder joint until the solder has flowed and the surface is fully wetted.

[GreyWoolfe]

If the wires I am trying to solder are thin, I put the tip under the wires and heat them so the solder flows, adding lots of liquid flux.  If the wires are thick, I will touch the solder to the tip while the tip rests on the wires, still using lots of liquid flux.  I will also use western union splices wherever possible.  When I solder PL-259 connectors, I just use the iron to drop solder in all the holes and use my little butane torch to melt the solder in.

[hizzy]

If the wires I am trying to solder are thin, I put the tip under the wires and heat them so the solder flows, adding lots of liquid flux.  If the wires are thick, I will touch the solder to the tip while the tip rests on the wires, still using lots of liquid flux.  I will also use western union splices wherever possible.  When I solder PL-259 connectors, I just use the iron to drop solder in all the holes and use my little butane torch to melt the solder in.

When you say "adding liquid flux" is this a separate product, other than the flux which is in the rosin core solder?

I have purchased this, but haven't tried it yet:

http://www.ebay.com/itm/252346279419?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Thanks!

[hizzy]

The general principle is to heat up the parts you are trying to solder and then let the part(s) melt the solder. That way the solder flows over the parts and not ball up on the iron tip.

(This usually causes cable sleaving to shrink/melt)

Hi!

Another silly question, perhaps: When soldering something like a DB9 connector, would you rest your tip against the bottom of the cup and let the solder fill the cup? Is go to the back or bottom a good soldering technique?

Thank you in advance!

[MosherIV]

Another silly question, perhaps: When soldering something like a DB9 connector, would you rest your tip against the bottom of the cup and let the solder fill the cup? Is go to the back or bottom a good soldering technique?

No silly questions if it leads to better soldering technique.

So with any connector with 'bucket' which accept wires - as I said the general goal is to heat up the parts you want to solder and let the heat from the parts melt the solder.
That said, for the bucket with a wire in it, it is very hard to heat both up at the same time.
personally, I find it easiest to put the soldering iron tip somewhere where it toouches both the wire and the solder bucket, a little solder on the iron will help make good contact.
Simple answer bottom of the open bucket and touch the wire at the same time.

[Ian.M]

There is no such thing as a DB9 connector.  In the D-subminiature connector series the second letter codes the shell size, and B is the size for the 25 pin connector.
See https://en.wikipedia.org/wiki/D-subminiature

However the D series connectors are invariably somewhat of a PITA to solder, and if you have the choice, use a shell that takes crimp contacts, with the correct contacts and specific crimp tool for it.   If you do have to solder them, its essential to pre-tin and trim the wire ends then you should pre-apply Hellerine expanding sleeving that you can ease over the joint after soldering.  Heatshrink is useless as you wont be able to get it far enough away from the joint to avoid it shrinking prematurely without cutting back the jacket and shield further than most backshells can accommodate.  You can only get away without sleeving if the wire has high temperature low shrinkage insulation.

Most D-sub contact cups will have a low side facing out, so your only real choice is to heat the side of the cup on the side you haven't wired the next pin on yet. If you attempt to heat the wire as well as the cup, you'll get excessive insulation burn-back and the bit will block the access you need to feed solder.  Because the wire has been pre-tinned, as soon as you feed a tiny bit of solder into the cup, the cup will effectively transfer heat to the wire.  Feed solder till the cup is fractionally short of full - nearly flat but slightly concave is far easier to inspect for suspect joints than an overfilled cup.  There should be minimal excess solder on the outside of the pin.

Exception: if you ever have to solder large diameter solid wire into D-sub cups, you will need to tin and flux the wire then heat both it and the cup due to the solid wire's much higher thermal conductivity.

Also many shells have thermoplastic insulators, so you need to support the contacts by plugging it into a mating connector while soldering it and not dwell excessively on each joint.  A three clip 'helping hands' tool is a big help here - two clips to hold the shell and one to position the cable so there is no sideways strain on the wire.

[tggzzz]

Here's a set of nine expert, succinct, and accurate videos on soldering, showing you what you need to acheive and why, how to achieve it, recognising mistakes and avoiding mistakes - including variants. https://www.youtube.com/playlist?list=PL926EC0F1F93C1837 But please, no sniggering at the pronounciation of "solder and "soldering"

One of the problems nowadays is that anyone can make a video blog. While some are very good and useful, most aren't; in the worst the Dunning-Krueger effect is strong One often overlooked advantage of the good old days (cough) was that because it was hard and expensive to make videos, people only made videos when they were required to pass on information, and they planned exactly the minimum that needed to be said.

[hizzy]

There is no such thing as a DB9 connector.  In the D-subminiature connector series the second letter codes the shell size, and B is the size for the 25 pin connector.
See https://en.wikipedia.org/wiki/D-subminiature

However the D series connectors are invariably somewhat of a PITA to solder, and if you have the choice, use a shell that takes crimp contacts, with the correct contacts and specific crimp tool for it.   If you do have to solder them, its essential to pre-tin and trim the wire ends then you should pre-apply Hellerine expanding sleeving that you can ease over the joint after soldering.  Heatshrink is useless as you wont be able to get it far enough away from the joint to avoid it shrinking prematurely without cutting back the jacket and shield further than most backshells can accommodate.  You can only get away without sleeving if the wire has high temperature low shrinkage insulation.

Most D-sub contact cups will have a low side facing out, so your only real choice is to heat the side of the cup on the side you haven't wired the next pin on yet. If you attempt to heat the wire as well as the cup, you'll get excessive insulation burn-back and the bit will block the access you need to feed solder.  Because the wire has been pre-tinned, as soon as you feed a tiny bit of solder into the cup, the cup will effectively transfer heat to the wire.  Feed solder till the cup is fractionally short of full - nearly flat but slightly concave is far easier to inspect for suspect joints than an overfilled cup.  There should be minimal excess solder on the outside of the pin.

Exception: if you ever have to solder large diameter solid wire into D-sub cups, you will need to tin and flux the wire then heat both it and the cup due to the solid wire's much higher thermal conductivity.

Also many shells have thermoplastic insulators, so you need to support the contacts by plugging it into a mating connector while soldering it and not dwell excessively on each joint.  A three clip 'helping hands' tool is a big help here - two clips to hold the shell and one to position the cable so there is no sideways strain on the wire.

I watched this video, and thought it was called DB9.




Thank you for your clarification! Also, I have never heard of Hellerine expanding sleeving. Do you have a link to it? Thanks again!

[helius]

Here's a set of nine expert, succinct, and accurate videos on soldering, showing you what you need to acheive and why, how to achieve it, recognising mistakes and avoiding mistakes - including variants. https://www.youtube.com/playlist?list=PL926EC0F1F93C1837

Yes, that series really is excellent, although also rather old (early '80s?)! The segment on "cup terminals" is appropriate for D-sub and circular connectors, and its recommendation to use solder preforms and resistance tweezers is quite useful.

[hizzy]

Here's a set of nine expert, succinct, and accurate videos on soldering, showing you what you need to acheive and why, how to achieve it, recognising mistakes and avoiding mistakes - including variants. https://www.youtube.com/playlist?list=PL926EC0F1F93C1837 But please, no sniggering at the pronounciation of "solder and "soldering"

One of the problems nowadays is that anyone can make a video blog. While some are very good and useful, most aren't; in the worst the Dunning-Krueger effect is strong One often overlooked advantage of the good old days (cough) was that because it was hard and expensive to make videos, people only made videos when they were required to pass on information, and they planned exactly the minimum that needed to be said.

I like that series a bit, but do they have a video showing how to join two wires together? That is what I find myself doing most often.

For the cup connector, does anyone use the technique show in the pace video? I don't know how it would work in small cups.

Thanks!

[T3sl4co1l]

Heat transfers entirely because the joint is "wet" and "sticky".  You reach this state by using flux and solder as liberally as you can!

"Can" means, don't leave it globby, shake or wick off excess if you went nuts.  But there's nothing wrong with that, soldering doesn't have to be an additive-only process.

Likewise, desoldering doesn't have to be a subtractive-only process, in fact it can't possibly be only that!  I've gotten weird looks from naive people before, when using solder to tin the tip of a desoldering (hollow tip) iron.  Well, how else do you expect the joint to heat up?!  (Also, flowing in leaded solder is a great help with desoldering lead-free joints.  Lower melting point, easier flow.)

Don't crank the iron temperature up.  Be patient and use lots of flux or solder.  Time at temp is what burns out the tip.  For leaded solder, 650F is fine.  Only turn it up as needed for big and stubborn joints.  (If you don't have a temp controlled iron, you should get one.  It's much easier to use, lasts longer, and only costs a hundred bucks -- it will easily repay itself in months to years, depending on how much you need it.)

Tim

[helius]

Desoldering tips certainly should be kept tinned (and should be covered in solder after use to protect the plating from oxidation). But if you want to really transfer heat in a hurry when desoldering, especially on old, dull joints, a thin coat of liquid flux works well. (The problem is that that flux gets sucked into the desoldering gun and gums up the filter faster). If you mess up and leave some solder down inside the hole, adding more solder is the only way you'll get it desoldered correctly.

[GreyWoolfe]

If the wires I am trying to solder are thin, I put the tip under the wires and heat them so the solder flows, adding lots of liquid flux.  If the wires are thick, I will touch the solder to the tip while the tip rests on the wires, still using lots of liquid flux.  I will also use western union splices wherever possible.  When I solder PL-259 connectors, I just use the iron to drop solder in all the holes and use my little butane torch to melt the solder in.

When you say "adding liquid flux" is this a separate product, other than the flux which is in the rosin core solder?

I have purchased this, but haven't tried it yet:

http://www.ebay.com/itm/252346279419?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Thanks!

This is what I buy.
http://www.all-spec.com/Catalog/Soldering-Rework/Soldering-Chemicals/Solder-Flux/835-100ML-33018?utm_source=bing&utm_medium=cpc&utm_campaign=Product%20Listing%20Ads%20-%20Shopping&utm_term=1100404856838&utm_content=PLA

[mariush]

Here's how you tin wires (paranoid nasa grade style) :



The whole series is nice, though really over the top with cleaning the components.

[tggzzz]

Heat transfers entirely because the joint is "wet" and "sticky".  You reach this state by using flux and solder as liberally as you can!

"Can" means, don't leave it globby, shake or wick off excess if you went nuts.  But there's nothing wrong with that, soldering doesn't have to be an additive-only process.

Likewise, desoldering doesn't have to be a subtractive-only process, in fact it can't possibly be only that!  I've gotten weird looks from naive people before, when using solder to tin the tip of a desoldering (hollow tip) iron.  Well, how else do you expect the joint to heat up?!  (Also, flowing in leaded solder is a great help with desoldering lead-free joints.  Lower melting point, easier flow.)

Don't crank the iron temperature up.  Be patient and use lots of flux or solder.  Time at temp is what burns out the tip.  For leaded solder, 650F is fine.  Only turn it up as needed for big and stubborn joints.  (If you don't have a temp controlled iron, you should get one.  It's much easier to use, lasts longer, and only costs a hundred bucks -- it will easily repay itself in months to years, depending on how much you need it.)

The videos in https://www.eevblog.com/forum/beginners/question-about-soldering-technique/msg1062935/#msg1062935 demonstrate all those points, along with how to select the right iron tip and temperature, then verify the selection by seeing good and bad results.

That is an invaluable addition to correct (but less than completely helpful) statements that the right temperature and tip should be used.

[hizzy]

Is there a difference in the quality of flux from paste & liquid?

Thanks!

[hizzy]

Here's how you tin wires (paranoid nasa grade style) :



The whole series is nice, though really over the top with cleaning the components.

Watching this video a couple times, I find myself more confused. The solder makes scant contact with the wire. It looks like the solder is coming more from the bottom, and it looks like he is using the iron's tip to "brush" the solder over the wire. What do other people think?

[helius]

Is there a difference in the quality of flux from paste & liquid?

Liquid flux is easier to overapply, and flows more easily around the board and under components (which can be good or bad). Watch out because many paste fluxes are not intended for electronics and are too corrosive. There's also tacky flux, which can be applied through a syringe but is a bit easier to control than liquid while retaining most of the latter's properties.

[helius]

Watching this video a couple times, I find myself more confused. The solder makes scant contact with the wire. It looks like the solder is coming more from the bottom, and it looks like he is using the iron's tip to "brush" the solder over the wire. What do other people think?

Because the wire is fluxed, it will be wetted by the solder that's on the tip of the iron. The goal is not to cover the wire with solder: it would be too stiff and brittle especially if it travels up under the insulation.
Ultimately molten solder wants to move towards the heat source, but it will spread over and wet fluxed metal surfaces along the way, as long as they get hot enough. The same way that you only need to heat a through-hole on a double sided board from one side, as long as there is enough flux, the same applies to wire tinning.

[T3sl4co1l]

I've got an old tin of Radio Shack flux.  It's transparent and amber in color, a smooth gel.  Best I've ever used, better than anything dissolved in IPA (it doesn't spatter and run away from the heat!), and better than the most common types of name brand fluxes!

Tim

[IanB]

Watching this video a couple times, I find myself more confused. The solder makes scant contact with the wire. It looks like the solder is coming more from the bottom, and it looks like he is using the iron's tip to "brush" the solder over the wire. What do other people think?

Yes, that is exactly what is happening. He creates a solder bead on the iron and then he allows the solder to get sucked onto the wire using surface tension and capillary action. You may think he is breaking a "rule", but this just shows that all rules are made to be broken. The reason it works in this case is that the wire was first covered with liquid flux. The rule about not applying solder directly to the iron applies when no extra flux is being used and the only flux is inside the solder. In the latter case you want the flux to melt onto the work and not onto the iron.

If you watch videos on drag soldering of SMT components you will see exactly the same technique being applied, where a solder bead is dragged along the pins. Once again this only works when lots of additional flux has first been applied to the work.

[IanB]

Ultimately molten solder wants to move towards the heat source

This is not really the case. Solder will flow over any surface it can wet, just like other liquids. The appearance that solder flows towards heat is a side effect of heat activating the flux which allows the solder to wet the fluxed surfaces. But otherwise the solder will flow anywhere it can, for example it will flow up under the insulation of a wire even when that is not wanted.

[rx8pilot]

Ultimately molten solder wants to move towards the heat source

This is not really the case. Solder will flow over any surface it can wet, just like other liquids. The appearance that solder flows towards heat is a side effect of heat activating the flux which allows the solder to wet the fluxed surfaces. But otherwise the solder will flow anywhere it can, for example it will flow up under the insulation of a wire even when that is not wanted.

Sort of....as the solder flows away from the heat the temperature rapidly falls and the solder cools and stop flowing. It flows best close the heat source because it is fully molten in that area. By the time the solder melts, the chemical action of the flux has already been used up.

Personally, I have my own technique similar to what GreyWoolfe described. Whether it's wire-wire or wire-to-contact I use sticky flux on both sides of the joint, then put a blob of solder on the tip of my iron, touch the blob to the joint that already has flux on it. The flux activates and the solder flows very quickly and without unnecessary heating of the joint. The instant the blob of solder makes contact with the flux, the heat transfer is very good and the brief moment where the flux has done it's work - the solder is there ready to go. The biggest reason I do it this way is that I only have two hands - one for the iron and the other for the wire. I don't have to hold the solder wire at all.

This one, although you can get smaller packages.
https://www.digikey.com/product-search/en/soldering-desoldering-rework-products/flux-flux-remover/1311241?k=flux&k=&pkeyword=flux&pv16=15070&FV=fff40014%2Cfff80209%2Cfffc013b&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25

[CraigHB]

I don't think touching or not touching the tip to the splice is going to make any appreciable difference.  The main thing is to get the joint hot enough for the solder to wet and flow.  For any solder job contact with molten solder from the tip is required for heat to flow into the joint.  The distance of the tip from the joint is probably not a critical thing as long as melted solder is in contact.  Now if the tip is dirty or there is a lack of wet solder the joint will not absorb enough heat to solder properly.  That's kind of just basic soldering technique.

Solder splicing stranded wires is something that seems to be a need more often than you would think.  It's always a pain and twisting them together results in a bulge of solder and wire at the splice.  What I've been doing lately is kind of knitting my splices.  What I do is push the two bare ends together so the strands interlace then I bind them with a wrap using a thin strand from a high strand count wire.  After binding and fluxing I get a joint that's not much thicker than the single wire itself.  After a shrink wrap it looks really clean.  It does take some time to bind the wires, but it's worth it to avoid the wires invariably loosening up and turning into a big blob of solder.

[hizzy]

I don't think touching or not touching the tip to the splice is going to make any appreciable difference.  The main thing is to get the joint hot enough for the solder to wet and flow.  For any solder job contact with molten solder from the tip is required for heat to flow into the joint.  The distance of the tip from the joint is probably not a critical thing as long as melted solder is in contact.  Now if the tip is dirty or there is a lack of wet solder the joint will not absorb enough heat to solder properly.  That's kind of just basic soldering technique.

Solder splicing stranded wires is something that seems to be a need more often than you would think.  It's always a pain and twisting them together results in a bulge of solder and wire at the splice.  What I've been doing lately is kind of knitting my splices.  What I do is push the two bare ends together so the strands interlace then I bind them with a wrap using a thin strand from a high strand count wire.  After binding and fluxing I get a joint that's not much thicker than the single wire itself.  After a shrink wrap it looks really clean.  It does take some time to bind the wires, but it's worth it to avoid the wires invariably loosening up and turning into a big blob of solder.

Would you have a photo of the knitted splice? Thanks!

[P90]

I've got an old tin of Radio Shack flux.  It's transparent and amber in color, a smooth gel.  Best I've ever used, better than anything dissolved in IPA (it doesn't spatter and run away from the heat!), and better than the most common types of name brand fluxes!

Tim

Not to mention  IPA ruins your iron tips...

[CraigHB]

Would you have a photo of the knitted splice? Thanks!

Sorry I don't have a photo, but if I get a chance I can do an example splice like that and post a photo.

[hizzy]

Hi Everyone!

Thank you for all of your help. It's interesting to see that the rules of soldering are not as rigid as I thought. There are many different techniques that can deliver great results.

I was curious about how most of you go about tinning your iron before soldering. There seems to be a slight difference in how people do this. I have noticed that some people clean the tip on their sponge/brass sponge, add solder to the tip, and then go straight to soldering. Others, clean the tip, add solder, and then clean the tip a second time, wiping excess solder off of the tip. Is one method preferable over the other or is this just another example of how soldering is flexible in its methods?

Thanks again!

[Ian.M]

It depends - its a lot easier to get the tip retinned evenly with excess solder then wiping it off, and for some work you need a clean tip with minimal extra solder but its far faster to simply wet the face of the bit with a little solder and go straight to the joint.  As long as you do a proper job of retinning the bit evenly before leaving the iron in its rest for more than a few minutes so you don't end up with oxidised unwettable spots, you can get away with the shorter method for most work.

[nanofrog]

NASA's Student Workbook for Hand Soldering might be of interest, as is their Pictorial Inspection site.

[hizzy]

The links above are very interesting! The NASA example confuses me, though because tinning the tip is step number 7. They don't seem to tin the tip before to soldering.

[IanB]

The links above are very interesting! The NASA example confuses me, though because tinning the tip is step number 7. They don't seem to tin the tip before to soldering.

You clean the tip just before soldering, so that it is bright and shiny. Cleaning removes any old solder, oxides and dirt so that these do not contaminate the joint. As long as the tip was already covered in solder before cleaning it will remain tinned (tinned just means covered with a film of solder).

[hizzy]

I was under the impression that I should clean and tin, prior to soldering each joint/wire/etc... Prior to use, each time I solder I clean the tip, add solder, and then wipe the tip again. I thought that was "standard", but I'm starting to think my method is flawed.

[suicidaleggroll]

I was under the impression that I should clean and tin, prior to soldering each joint/wire/etc... Prior to use, each time I solder I clean the tip, add solder, and then wipe the tip again. I thought that was "standard", but I'm starting to think my method is flawed.

That's pretty excessive.  You can do many joints in a row before needing to clean the tip again.  Just keep an eye on it, when it starts to accumulate a significant amount of cooked flux to the point where it becomes difficult to get good contact with the joint (or when it accumulates a blob of solder large enough that it starts causing problems), you need to clean it.  With small joints this might happen every 5-10.  With large joints it's quite a bit more.  In addition to that, clean and tin when you first start soldering, and again before putting the iron back in the holder when you're going to leave it for a while.

[GreyWoolfe]

+1.   When I am done, I take an extra step that when I turn off my stations, I add a blob of solder to completely cover the tip.  That gets removed when I turn the stations on again.

[Brumby]

If you're becoming confused about the 'rules' of soldering - it's because you are overthinking things.  You need to just understand the basics ... and then learn by doing.

Basic No 1.  Flux.
Note: In the following, I will be talking about using a flux-cored solder, with no external flux - for one very specific reason ... you will get to understand the basic process much better.  This will mean that, when you come to do your own soldering, with or without additional flux, you will know what's going on - and have a better idea of what you can and can't get away with.
Solder bonds to clean metal - not dirty, oily or oxidised surfaces.
 - If the object to be soldered is particularly dirty, mechanical cleaning may be necessary.  For critical applications - such as aerospace - mechanical cleaning may be required on any surface to be soldered, no matter how clean it may look, to ensure it is as free from contaminants as possible.
 - Even freshly cleaned metal will oxidise in a short time - and heating the metal will accelerate this
 - Flux is used to dissolve these oxides and allow the solder to bond with the metal
Now for the biggie....
 - Flux will deteriorate from the heat of soldering.  Since it is important to have it working on the surfaces to be soldered, a lot of the 'rules' circle around this very specific issue.  If you keep just this one thought in mind, then a LOT of what might be confusing to you now will become much clearer.

Putting a blob of solder on the tip of an iron and then transferring this blob to the workpiece with the intention of using this blob of solder as the jointing material is the absolutely WRONG thing to do.  If you see people who have been soldering for a while doing this ... look more closely.  You will probably find they are simply adding a blob of solder that they can bring to the workpiece to allow better heat transfer from the iron to the work (The molten solder wraps around the joint and provides more surface area for heating - even if that solder doesn't 'wet' the joint.)  Once the joint is heated, you can apply flux cored solder where the flux removes the oxides and the solder wets the joint. (Yes, you will probably see some of the blob get sucked into the joint, but that wasn't the point.)

Heating the joint and applying the solder can be done in one of 3 ways - and how good or bad each method is is directly related to the degree of degradation of the flux.
1. Heat one side of the joint and apply solder to the other, so that the solder is melted by the joint, not directly by the iron.  While this is best for flux preservation, the joint will be subjected to more heat - so you need to be aware of this and consider the risk of heat damage to what is being soldered.
2. Heat the joint and apply the solder to the joint and the iron at the same time.  This gives quick melting of the solder and the flux is very close to where it needs to be.
3. Adding solder to the iron and then applying this to the joint.  A bad practice to get into - but if you do find it necessary to do something like this (in drag soldering, for example) you are going to need external flux for a reliable result.  With this method, as you carry the blob to the workpiece, that wisp of smoke is the flux burning up - so you need to have flux already on the workpiece.


Basic No 2. Heat.
You will need a certain amount of heat to complete a joint.  This is a function of time and temperature.  Too high a temperature can cause a lot of problems .. from flux vaporising before it can do anything to frying components.  Too low a temperature is also bad if it increases the time it takes to do a joint.  You might feel it's doing less damage, but you are just using the 'slow cooker' approach.  If the iron is hot enough to melt solder, it's hot enough to do damage.  Look at a few videos of people with some experience to see how long they take to do a joint - a lot of the time it's under 2 seconds.

Basic No 3. Tip - size and shape. 
Use a tip on the soldering iron that is appropriate to the joint.  Thick tips can hold more heat closer to the joint, so you can finish the joint sooner, but they can be clumsy.  Also, use a tip with a shape that reasonably matches the surfaces being joined.  Better surface contact will carry heat into a joint more quickly.  This is why nobody here has much in the way of positive comments on round tips.

Basic No 4.   Solder.
There's a lot to discuss here - but if you're just getting into it, a 60/40 or 63/37 flux cored solder is where I would start.

Basic No 5.   Iron.
Some might complain this should be higher up in the list - but if you understand what is going on, you can do decent solder joints using a nail and a blowtorch.  It won't be easy and it won't be efficient, but it can be done.
The main thing is, to get something appropriate to the type of work you will be doing - and if you're serious about electronics work, spend the money on a decent temperature-controlled iron.

[SeanB]

The one thing that gets me is every person who handles bare solder with fingers. I always use a small tube and coil up some solder inside, using as a source of tubes those plastic packs you get vitamin tablets in, or for a lot of my use a small plastic push on handle for piping, with a bottle cap as an end, and a hole in the end to feed the solder out. keeps the solder from contamination by oil, and also keeps your hand free of wiped off lead as well.

As a bonus you can have 3 tubes with different sizes of solder in a small tray, and no mucking about with reels that unwind, fall over or that simply are unwieldy to use. To refill I use a plastic BIC pen, and chuck it in the cordless drill, start the one end with solder into the chuck, and wind away off the roll making even layers till it is the right thickness to just fit the tube, then stop, remove the pen and put it in the tube. The end placed in the chuck then is fed out the hole, and you put the cap on and are done for a few dozen meters of solder.

[mariush]

Or you could buy some nitrile gloves like Louis Rossman does and this way you can still FEEL the solder in your hands as you work with it, instead of messing about with tubes and other things.
They're around 10 cents or less, if you buy in volume.

[CraigHB]

I've been handling my solder bare handed for years.  I have no idea the risk of lead poisoning that way.  Can you even get lead poisoning through your skin?

[SeanB]

Do you wipe your face without noticing it, scratch your face or just generally touch without washing your fingers, then you will get some transfer of the oxides to your interior, and with damp fingers some soluble lead compounds ( from reaction with sulphur and amines in your skin) will be diffused through.  As lead is a cumulative poison it is best to minimise exposure, though the major source of lead in your body is from water ( Hello Flint!), the air you breath ( TE lead in fuels and in coal burnt in power plants and in burning of garbage) and in your food. Solder is a pretty low amount, but still worth minimising.

Fun thing is the 2 sources of mercury you are exposed to is fillings with amalgam, and fish, with the fish being the higher source of it as well, especially salmon, but it is there in all predatory fish, along with DDT.

[Ian.M]

There's minimal skin contact risk from solder wire unless you smoke or eat without washing your hands.  SnPb solder paste is a different matter as the combination of micro-particles and flux activators may result in traces of organo-Lead compounds and the solvents increase the risk of skin adsorption,.

[P90]

Or you could buy some nitrile gloves like Louis Rossman does and this way you can still FEEL the solder in your hands as you work with it, instead of messing about with tubes and other things.
They're around 10 cents or less, if you buy in volume.

I don't care for gloves... you lose the sence of feel... same goes for condoms...   

[T3sl4co1l]

Please... remember to practice safe soldering.  Or else you'll need to take the pill*!

(*Which I think is actually injections, not a pill, so have fun with that.  Of course, it would only come to medical treatment (chelation therapy) if you're really daft, and eat the stuff, or rub it all over your body.  Just... don't do that.  Washing hands after handling?  Stupidly effective.)

Tim

[P90]

Please... remember to practice safe soldering.  Or else you'll need to take the pill*!

(*Which I think is actually injections, not a pill, so have fun with that.  Of course, it would only come to medical treatment (chelation therapy) if you're really daft, and eat the stuff, or rub it all over your body.  Just... don't do that.  Washing hands after handling?  Stupidly effective.)

Tim

I played with lead toy soldiers and cars when I was a little kid, probably chewed on them more than I can remember, I turned out fine... I think... anyway, they make too big a deal out of lead. I'd be more concerned about mercury...

[tggzzz]

Do you wipe your face without noticing it, scratch your face or just generally touch without washing your fingers, then you will get some transfer of the oxides to your interior, and with damp fingers some soluble lead compounds ( from reaction with sulphur and amines in your skin) will be diffused through.  As lead is a cumulative poison it is best to minimise exposure, though the major source of lead in your body is from water ( Hello Flint!), the air you breath ( TE lead in fuels and in coal burnt in power plants and in burning of garbage) and in your food. Solder is a pretty low amount, but still worth minimising.

Fun thing is the 2 sources of mercury you are exposed to is fillings with amalgam, and fish, with the fish being the higher source of it as well, especially salmon, but it is there in all predatory fish, along with DDT.

Your case would be more convincing if you replaced the adjectives with numbers, even rough numbers.

You should compare the risks from lead in a solder wire, with lead in solder paste, with lead from the environment. Examples of the latter: 20 miles from my house you can't grow and eat your own vegetables due to the Pb and Cd in the soil, and some of the water pipes coming to my house are made of lead.

For the latter, I've removed adjectives and measured the results of taking and not taking simple precautions.

You should then compare the micromorts associated with lead wire, radon, smoking, and - especially in South Africa, "traumatic lead poisioning".

FFI on micromorts, see https://plus.maths.org/content/os/issue55/features/risk/index

[SeanB]

I avoid fish from my local harbour, especially since they decommissioned the TE lead tank there, and had a small announcement about finding a crack in the tank, and that around 25 tons of the TE lead concentrate went into the ground, and from there around 50m directly into the harbour, right near the best fishing spot ( and about the only one you do not need a harbour permit to get to, so very popular) in the harbour.

http://www.oilwatch.org/doc/paises/sudafrica/sudafrica2003ing.pdf

[hizzy]

Hi,

I was wondering what popular opinion is on this technique for soldering dsub connectors:

http://www.aeroelectric.com/articles/dsubs/d_solder.html

Does this look like a method I should emulate?

Thanks!

[nanofrog]

Yes, that's a good method. 

IF you want to meet NASA/Mil-Spec standards however, the gold plating inside the solder cups has to be removed first. So you'd fill the cup with solder, then wick it out. And finally complete it with the steps as described. No need to do this at a hobbyist level IMHO however.

[hizzy]

Thankfully, I don't think I have plating in my solder cups. They just look like plain silver!

[Ian.M]

Hopefully that's tin plate, which takes solder readily if its not old and badly oxidised.

While the techniques that pre-load the cup with solder are good for individual wires, I always found them to be a PITA if working with a cable and a short back-shell as manipulating a short wire constrained at the other end to insert it while the solder is molten has a high risk of insulation damage.   *IF* the cups take solder readily, I would recommend fluxing them lightly with liquid Rosin based flux, shaking or blotting off excess and allowing them to dry to leave a trace film of flux inside the cup, then inserting the pre-tinned and trimmed wire cold then soldering, feeding solder as required to correctly fill the cup.   If they *DON'T* take solder well you'll need to pre-tin and wick NASA style.  It does require a slightly longer dwell time as its essential that any pockets of flux or air bubbles have enough time to come to the surface.

Unless you are 100% certain the insulator is themoset, not thermoplastic, always protect the insulator against distortion by mating the connector with its opposite gender one to support the contacts while soldering.   The only thing worse than breaking a pin on the centre row of a DE-15 plug because it skewed out of alignment due to the insulator softening, is a skew pin distorting the contacts of a PCB mounted socket so that a correctly assembled un-distorted plug no longer makes reliable contact  . . . . 

[hizzy]

How does this look? I think he could have tinned the wire first. Should there be less solder on the tip of his iron?





Thanks!

[Ian.M]

In addition to failure to tin and trim the wire, you can see it move as he finishes the joint - so that's a possible dry joint right there.   Then he shrinks heatshrink by direct contact with the bit. If you are going to use a soldering iron to shrink heatshrink, hold it just above but NOT in contact with the barrel near the tip and let the hot air convection do the job.

As we don't get to see a closeup, we cant tell if he's transferred excessive solder to the side of the pin or how good the joint is .

[mariush]

What you do in the video is just ... acceptable.

One observation ... you don't clean the tip on the sponge.   Add a bit of solder on the tip if there's not much, get a paper towel or "chemwipe" (lint free handkerchief sort of) , clean the tip with this paper towel/ whatever (run the tip over the paper and rotate it a bit).  Now that it's clean of solder, rub it a bit on the wet sponge to break whatever oxides are still there, and put a tiny amount of solder to minimize oxidation.  You're ready to solder. When you're done, add some solder to the tip to protect it until next use (you'll remove this solder with your paper towels next time)

The technique is not that great because you have little control over how deep the solder actually goes in.

Pace Worldwide (they make soldering stations and lots of soldering related tools) has on their channel very good videos. Among them there's a series called "Basic Soldering Lessons" which may seem dated, but the information in the videos is still quite valid.  You should definitely watch parts 1, 6 and 7 as a refresher, and below you can see Lesson 3 which is about cup terminals (similar to what you have on those D connectors)



The basics : TIN the wires first... it's important.  Fill the cups with solder (bend solder wire in 2 or 3 or as many times as needed to get thick enough solder to get right amount in cups).  Heat until flux boils at the top then insert tinned wire, remove tip and hold in place until everything solidifies.

This guy does it the paranoid nasa avionics grade ultra ridiculous whatever way - seriously you'd probably roll your eyes half way into the video :

[CraigHB]

In my many years of soldering electronics I've come to like brass wool for tip cleaning the best.  I use the Hakko replacement pads.  It cleans any stubborn oxidation easily.  A wet sponge works well, but in some cases it doesn't get all the gunk off.  The down side with the wool is there may be some abrasion that occurs, but I haven't noticed it reducing the life of the tip at all.  The down side with a wet sponge is the temperature shock suffered by the tip, but again have not noticed any tip degradation due to that.

[hizzy]

I ordered a brass cleaner this morning, along with a few different tips!

[helius]

If you use a sponge to clean your iron with solder on it, it quickly gets covered in solder blobs. With the brass wool there's no problem, the solder just pools and hardens in the bottom of the container. :thumbsup:

[hizzy]

When soldering a d sub connector, is there a preferred tip I should be using? Should I go for the smallest one possible? Thanks!!

[T3sl4co1l]

I'd go with a flat wedge, or whatever they call the tilted-faced-cylinder thing.

Tim

[nanofrog]

When soldering a d sub connector, is there a preferred tip I should be using? Should I go for the smallest one possible? Thanks!!

Personally, I'm fond of bevel/hoof shapes as well as chisels and bent chisels. As per size, you need the tip sized to the joint, so No, don't use the smallest one possible as you won't get sufficient thermal transfer.

Hakko's Tip Selection page should be of interest, as it shows you what the different shapes are used for, and how to size a tip to the joint (lots of illustrations and movies).

[hizzy]

Hi,

Thank you all for the replies! I was wondering: Would it be a good idea to get some magnifying glasses? Is that commonplace among most soldering gurus out there?

Thanks again!

[John Coloccia]

Hi,

I was wondering what popular opinion is on this technique for soldering dsub connectors:

http://www.aeroelectric.com/articles/dsubs/d_solder.html

Does this look like a method I should emulate?

Thanks!

Bob is the man when it comes to aircraft wiring techniques! I've had the pleasure to chat with him a couple of times over the years. Always a gentleman. I'd encourage you to buy his book. It's money well spent and a lot of techniques are directly applicable in your own projects.

[nanofrog]

Hi,

Thank you all for the replies! I was wondering: Would it be a good idea to get some magnifying glasses? Is that commonplace among most soldering gurus out there?

Thanks again!

It's not really necessary for thru-hole, but smaller SMD, it's quite useful. In the latter category, some have even opted for a binocular or trinocular scope (~7x - 45x). Amscope is popular due to the value they offer.

[tggzzz]

HI was wondering: Would it be a good idea to get some magnifying glasses? Is that commonplace among most soldering gurus out there?

That entirely depends on your eyes, so there's no way anyone can give a useful answer.

At my age I use a head-mounted visor, and have a surprisingly good ex-school stereo microscope for close inspection.

[CraigHB]

I'm older and my close vision is not so close anymore.  I use a stereo microscope at 10x most of the time.  It also has a 30x setting, but I only use that for inspection.  I think in my youth I could have done larger components like 0805 (2012 metric) without visual aid, but even then I probably would have needed magnification for 0603 and smaller (back then it was all through hole).  In any case there's lots of options.  The visor style that watchmakers use is popular.  You can use a magnifying glass on a stand or just reading glasses.  I have a set of readers in 3x and I use them a lot for bigger stuff like soldering wires to PCBs.  With better close vision a set of 3x readers would probably do for most stuff.

[GreyWoolfe]

I use a headband magnifier also, even for through hole.  I am far sighted with amblyopia and astigmatisms in both eyes so magnification just works all around for me.  I even use the magnifier for threading needles.  Don't forget good lighting.  I upgraded the lighting on that half of the workbench and it made a big difference.

[CraigHB]

Yes lighting does help a lot when you have limited vision.  I run a couple bright LED floodlights over my work bench.

[steverino]

I use a headband magnifier also (old eyes).  I don't know if I'll ever go the microscope route, uses valuable desk space and just looks like a hassle.  I need a #7 lens on my optivisors and this level of magnification has a focal length that puts my nose about 4 inches from the board (maybe more) which then blocks my lighting.  The best task light I've found so far for close work like this is the Ikea gooseneck lamp, which is only about $22 on ebay.

[CraigHB]

I'm not much further using the microscope, but yeah it is kind of a hassle.  The main problem is the platform isn't always big enough.  I need one that uses a flat mount to allow use of the whole desktop.  What I like about it is the magnification is greater with a lot less distortion than a simple magnifying task light or glasses.  It makes small things look big and easy to work on.  Now having nerves steady enough to do the work without making a mess of it is another thing.

[IanB]

I'm surprised audiophiles haven't cottoned on to this. Shouldn't high end audio equipment be assembled with AuSn solder? 

[John Coloccia]

This guy does it the paranoid nasa avionics grade ultra ridiculous whatever way - seriously you'd probably roll your eyes half way into the video :

That's very normal in avionics and especially astronomical electronics. Gold must be removed before soldering as gold and tin often form a number of different brittle inter-metallic compounds which give you trouble after many times of thermal cycling.
The general rule in avionics is either you have a lot of gold, or none. For some really critical connections that oxidization is not acceptable even in harsh environments, people use gold-tin solder with very high concentration of gold to inhibit the form of IMC as well as to inhibit corrosion. When the cost of AuSn solder can't be justified, people just get rid of gold completely.
Another use of AuSn solder is in high voltage applications where any flux contamination are not accepted. Imaging you are building a power module of 20kV, then any trace amount of baked flux (essentially carbon) will cause long term reliability issue. AuSn solder, thanks to the superior wettability and fast solid phase diffusion speed of gold, doesn't need flux to wet most surfaces, and the bond will grow stronger over time, rather than degrade over time.

Aircraft have massive vibration problems also, especially piston driven aircraft. For example, it's not uncommon to have a wire that was left slightly loose and able to touch part of the airframe, and during annual inspection you find that it's rubbed completely through the insulation.

[tautech]

Hi,

Thank you all for the replies! I was wondering: Would it be a good idea to get some magnifying glasses? Is that commonplace among most soldering gurus out there?

YES, even if it's only some +1,2 or 3 $2 spectacles but the visor type headsets are better.
For new TH work after some experience they are of questionable need, but for any faultfinding of poor joints, cracked traces, reading component ID#'s and SMD, any magnification is welcomed but normally if your eyesight is reasonable 5X is plenty.
Start with say 2-3X for little $ and go from there as need dictates. 

[CraigHB]

The general rule in avionics is either you have a lot of gold, or none.

Gold is an amazing metal, it's really useful in electronics, too bad it's so darn rare.  Need to mine asteroids to make the stuff more available for this kind of use.

[CraigHB]

Aircraft have massive vibration problems also, especially piston driven aircraft.

Vibration is a bitch to deal with.  Motorcycles can have the same problem, especially the ones with only one or two cylinder engines.

[hizzy]

Here is the ultimate stupid question: What wire size would you use when soldering a de-9 connector? Would it be 22 awg or higher?

Thanks again!

[nanofrog]

Here is the ultimate stupid question: What wire size would you use when soldering a de-9 connector? Would it be 22 awg or higher?

Thanks again!

Check the datasheet to be sure, but IIRC, 20AWG is typically the largest wire size.