<<<<<<<<<<<  How To Solder - Principles, Technics, Etc. >>>>>>>>>>>    Last Post

For those new to the process, soldering is often challenging {and sometimes misunderstood}. 

I have searched the IntoFPV forum for soldering related threads and have found information scattered 
in a variety of places.

In an effort to help those new to soldering, I have started this thread and hope to provide a place 
where it all comes together.

First a little about me. I have been soldering electronics since I was 17 {about 54 years ago} and 
have soldered everything from electronics to copper plumbing pipe {the principles are the same}. 
Over the years, I have soldered in my career in Information Technology as well as things for myself 
and others. Also, I watch a lot of videos about soldering, not because I need to, but because I enjoy 
watching them; some are better than others.

In all of the soldering videos, articles, and threads; I find it curious that the focus is on the process 
of soldering but rarely is a definition of the physics explained nor how soldering actually works. 
Consequently, I have included this information in 
Post #2.

Right up Front, I use a cheap 60 Watt soldering iron with a medium conical (pencil) tip
and the temperature adjustment wheel taped at 425 C degrees. 

       As long as the iron gets hot enough, it will work. That is just a physical Fact.


I intend to update these posts when I find additional information. As mentioned, the useful information 
is scattered in a variety of locations. As I continue to watch soldering videos, I will include the ones 
that I perceive to be the good ones.

Table of Contents:

The definition and process, Post #2

Related IntoFPV threads, Post #3

YouTube Videos and Internet articles, Post #4

Definition and Process:

Let’s start with a definition: Soldering is a thermal bonding process where hot metal workpieces are joined 
with a filler material {solder}. It is the heat in the metal that allows the solder filler to make a successful 
bond. If the metal workpiece is Not Hot enough then the solder filler will NOT bond, period. After the 
solder is applied, allow to cool. The bond is not complete until the joint cools and the solder solidifies.
Wikipedia - Soldering

The thermal bond can NOT be made by applying hot solder to a metal workpiece that is cold or not 
hot enough for a successful bond; this is referred to as a COLD solder joint {because the metal was NOT 
hot and the joint did not thermally bond}. Solder is NOT a glue and does not work like glue.

Now, all metals oxidize which is essentially a thin coating of “rust” which acts as a barrier to the thermal 
bonding process. Removing this oxidation is accomplished with Flux which functions as a cleaner to 
remove the “rust” and aid in the bonding.

So, soldering goes like this:   
1)   Apply Flux.
2)   Heat the metal until it is hot enough to melt the solder.
3)   Apply solder to the hot workpiece.
4)   Remove heat and allow joint to cool.
 
To illustrate, let's start with a plumbing example.
1)   First, a generous amount of flux is applied to the copper pipe.
2)   Next, a torch {normally propane or Mapp gas}  is used to heat the copper pipe joint.
3)   When the pipe is hot enough, solder is applied to the joint, it melts, and is sucked into the joint.
4)   Remove heat and allow to cool.

Notice that the solder is melted by the hot copper pipe, NOT the torch. The only requirement is that 
the pipe be hot enough to melt the solder.

Really, pretty simple: 
1) Use a lot of flux, 
2) Heat the copper, 
3) Apply the solder, 
4) Remove heat and 
5) Allow to cool, done.

Now, let's move to electronic soldering {the bonding process is the same}.  A simple illustration is the 
process of tinning a wire. Take a piece of small insulated wire, strip one end, dip the end into the flux, 
touch the solder to the wire a little down from the end, touch the soldering iron to the underside of the 
wire near the end so it only contacts the wire and does NOT touch the solder. As soon as the solder melts 
it will flow around and through the wire, quickly remove the iron, done. Notice that the iron is only used 
to heat the wire, it is the wire that melts the solder. This concept can not be stressed enough and is often 
not well explained.

Tinning is the process of bonding solder to some material. When you touch solder to the iron, it melts
and "tins" the iron. As long as the iron is hot, the solder will remain molten. When the solder cools it
will be bonded to that material. To tin a workpiece, the material is heated with the iron then solder is 
applied to the HOT material (wire, pad, etc.), the solder melts and covers the material. When the heat 
is removed, the solder becomes solid again; bonded to the material. Tinning is the process of bonding 
solder to a material workpiece (generally a wire or pad). The iron is considered to be "tinned" when
solder covers the tip even though it is molten as long as the iron is on.   

When I tin a pad, I apply a lot of flux to the pad {there is no such thing as too much flux}, touch the iron 
to one corner of the pad,  touch the solder {I use ultra thin .5mm solder} to the diagonal corner of the 
pad, when the solder melts, done. This generally takes about second or two.  In actual practice, I 
generally touch the pad with the iron and solder at the same time...and sometimes the solder touches 
the tip of the iron as well {after all , these are very small parts}.

For really tiny pads, I will sometimes touch the solder to the tip of the iron and then the iron to the pad. 
This is a lot trickier to accomplish because the pad still needs to get hot, but the solder is already melted. 
I try to only touch part of the pad, if the solder flows over the entire pad, then it is good. Still only takes a 
second or two. For pads and tiny connections, if it takes longer than a couple of seconds, then there is a 
problem. Remove the Heat. Generally, there is not enough flux or the iron is not hot enough.

While it is technically possible to make a soldered connection between two materials that have not been 
tinned, it is much easier and quicker to accomplish between pre-tinned components. When both materials 
are tinned, the bond will be accomplished at the melting point of the solder.

Since most pads are extremely small, I put the wire on top of the pad, then touch the iron to the wire 
using very, very light pressure. The instant the solder melts, the wire will sink into the solder on the pad. 
Quickly remove the heat and allow to cool. Done.

For larger work that takes longer to reach temperature, applying solder at the point where the iron 
contacts the workpiece {generally a big wire} will create a heat bridge that will allow the metal to reach 
temperature faster. I use a conical, pencil, tip and will lay the tip  on its side if the wire is really large. 
This puts more of the tip in contact with the wire. I apply solder between the tip and the wire which also 
helps the heat transfer.

Now that we see how soldering works, let's talk iron temperature. Since solder melts at 183 C degrees
for {63/37} and between 188-190 {60/40}, one school of thought says that you only need to set the 
iron temperature above 200 C degrees. From what I can tell 350-375 C degrees is quite common. While
this is "technically" correct, a hotter iron always seems to work better when actually doing the work. 
The part heats quicker and you are in-and-out faster. The hotter iron definitely works better for larger 
wires and pads.

In order to understand the effects of iron temperature, let's consider how heat is conducted. If 450 C 
degree heat is applied to the end of a bare copper wire that you are holding, the wire does not 
immediately heat to 450 C degrees. Neither does a pad. Now, if solder is touching the wire or pad, 
the very instant that the wire or pad reaches the solder’s melting point, 183 C degrees {63/37 solder} 
or 188-190 C degrees {60/40 solder}, the solder melts and the heat is removed. Now ask yourself...
how hot did the wire or pad get???  That's right, just slightly above the solder's melting point 
and likely not much over 200 C, if that. The hotter iron only allows the material to heat faster 
{NOT necessarily get any hotter}.

Keep in mind, that TIME is the enemy. The longer the iron is on the pad {regardless of  the 
temperature of the iron}, the more the heat dissipates through the entire board to other 
components. Although it would seem that a hotter iron would be worse than a cooler iron, 
that is NOT necessarily the case. A hotter iron heats the part fast so you are in-and-out quicker 
with actually less heat dissipation through the board. A cooler iron takes longer to heat the pad 
and heat is actually dissipated for a longer period of time. If the bond is not accomplished in a 
couple of seconds, REMOVE the heat. If that iron sits on the pad for more than a couple of 
seconds you run the risk of cooking something on the board. Larger pieces such as the battery 
lead wire will take longer to heat up, but don’t panic, if the solder doesn’t melt, then the 
temperature of the piece is still less than 200 C degrees.

When working with larger wires or pads, it takes longer to heat up the material, but a hotter 
iron will still heat the material quicker than a cooler one. A bigger tip helps, too. As the material 
heats up, the iron cools down. Now, here is where the "heat refresh rate" of the iron comes into 
play. A higher wattage iron will refresh quicker and maintain tip temperature better. That is why 
a super high wattage solder GUN will heat large wires faster than an iron even set to the same 
temperature. 

For larger work such as battery lead wires, applying solder at the point where the iron contacts 
the workpiece {generally a big wire} will create a heat bridge that will allow the metal to reach 
temperature faster.

My iron is set at 425 C degrees and the adjustment wheel is taped so it won't move. {Sometimes 
I catch some criticism, but it works so I don't care}. Yeah, I use a 15 dollar (US) iron that is AC
powered and rated at 60 Watts that I bough on AMAZON years ago. I also use the same conical 
(pencil) tip for pretty much everything. I have tried the thinner needle tips, but they just don't 
seem to transfer heat fast enough. I might consider a chisel tip for some things, but so far, I have 
never really needed one. For me, a chisel tip is just too large for those tiny pads on an FC board. 
Back in the day on 30x30 boards, the pads were likely bigger, however, the boards that we work 
on today have very tiny pads.

To clean the tip of the soldering iron, I use one of those little brass "brillo pad" things that looks 
like wire hair to clean the bulk of solder from the tip and a wet folded up paper towel. It is amazing 
how well the wet paper towel works although it does cool the tip a bit. For some reason, the water 
really makes the solder shine. Well, at least if the solder is a quality grade.

Over the decades, I have used a wide variety of solder, but mostly 60/40 rosin core solder for 
electronics. More recently, I have switched to 63/37 rosin core solder {Kester brand} due to the 
lower {and consistent – eutectic } melting point. This is my solder of choice. Although cheap solder 
may work, it is generally not as good and the melt point is not as consistent. Also, some cheap 
solder simply does NOT shine, so it makes one think that the joint is bad; watch out for this as the 
joint may actually be ok, but still NOT shine. Just buy a quality brand such as Kester 63/37 Rosin 
core solder and be done with it.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2022-01-09 UPDATE ---->>   SOLDER        The ultra thin (0.5mm) solder 
                                                                    works really well on tiny pads.

I use Kester 63/37  0.5mm (0.020 inch)

Similar: Team Black Sheep (TBS) 63/37  0.5mm

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 

To summarize the basic steps:

Set iron temperature as Hot as you are comfortable with. {mine is set to 425 C degrees}
Apply a lot of flux,
Use thin (.5mm) {high quality} rosin core solder,
Heat the workpiece with the iron {when joining, touch both parts at the same time},
Apply solder to workpiece {when joining, touch both parts at the same time},
When solder melts, remove heat,
Allow to cool, done.

TIP:   If it takes longer than a couple of seconds, REMOVE the heat and take a break.
         Relax. When you go back to it, use a lot of flux, a hot iron, and heat the material 
                                                                                                      (pad, wire, etc.). 

Finally, there must be hundreds of YouTube videos and internet articles about 
soldering; some are better than others. Although the core principles are the same, 
there is a wide range in presentation and technics. In addition to “How To” videos, 
there are “How Not To” videos. There are general videos, quad specific videos, and 
videos for particular situations; like soldering a USB connector to a circuit board.
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Oscar's How to Solder


2022-03-13 Edit:  ADD  ===========================================================

Now, let's consider "Anti-Static" protection. Technically speaking, any time you touch any electronic 
components your body "could" discharge static and damage something. This is ANY time that you are 
working with the circuit boards, NOT just when soldering. In fact, anti-static protection might be 
considered ANY TIME that you touch the electronics on the quad. 

That said and duly noted, I have worked with electronics for decades without anti-static protection and 
have {so far} not had any issues regarding static from my body. Most of the time, a person likely is in 
contact with some form of "ground" which basically discharges any potential static. Each person should 
consider whether or not to risk any potential damage due to the body's static electrical potential and
what, if any, anti-static protections that they might need to use.

==============================================================

2023-10-13 Edit:  ADD:   Soldering Through Hole Connectors

When soldering wires or pins using the hole in a through-hole pad NO additional flux 
is needed on the hole and Not on header block pins, however, I suggest tinning wires. 
For wires, I also leave the exposed (tinned) wire a bit long and trim after soldering.

1) Insert the wire or pin through the hole.
2) Place the solder on the hole and up against the wire.
3) Place the iron tip on the hole and up against the wire, but not against the solder.
4) When the solder melts, it will make a sort of tear drop over the hole and around the wire. 
5) Remove the heat. 
6) Trim excess wire if needed. 

This picture shows where and how I position the solder and the iron.

Related IntoFPV Threads:

[Tutorial]  Soldering peripheral leads to battery connections  ( Roger74 )

[Tip & Trick] Soldering for novices   ( Titanv11 )


Soldering for beginners    ( Dins )

How to Solder like a Spaceman   ( Sloscotty )

Soldering equipment   ( Ashbird78 )

Thoughts on my soldering?   ( Ditty_FPV )

How NOT to solder     ( unseen )
            POST #66 is good idea (solder to pads rather than resoldering connector)   ( sevro )

Soldering a DIY 18650 Li-Ion Pack   ( Momobrut )        

Internet Articles:

Oscar's How to Solder article.



YouTube Videos:

===============================================================

2021-11-09 Update : Video Added.   >>>  2023-10-13 EDIT: Revised the Text.   

Regardless of JB's soldering technics or skills, he does a decent job of explaining the PROCESS 
of soldering and how soldering works. Yeah, he could have done a bit better, however, focus
on the how soldering works. 


 

===============================================================
 


  
Even though it is a few years old,
this YouTube video is a pretty good short video:   How To Solder 

Another good video >> Basic Soldering Principles

A couple of good videos in Soldering for beginners,  Post #15 (HERE)


I have watched JJRotoGeek's video several times, not because I need to, but because 
the guy is a riot and fun to watch. He is real down-to-earth practical without the hype...
a get it done type of guy who solders professionally for a living. He does use some "language" 
so sensitive people might get offended, but it doesn't bother me. Kind of keeps it real and 
interesting. 
 
 Tech Teach - Quadcopter Soldering!!!! 


{2021-12-24} Thank You Titanv11.

This is a good "close up" video showing effects of cheap solder.  
Plus, good technique for thru hole soldering.

Here


{2022-01-01} Thank You Romangpro.

This is a good video on soldering iron tip selection. It also demonstrates how 
heat is transferred from the iron to the pad.
 
Notice that the pad does NOT immediately reach the temperature of the iron.  

Use the Largest tip that will fit the work area. 

Largest Tip Video


FLUX. Also shows swipe soldering. 




2022-03-13 Update - Video Added

The following video illustrates connecting two wires together. In it, he explains that 
the iron heats the wire and the wire melts the solder. Also, this is the first time that 
I have seen "silicone" paste used. I will need to explore that product and its potential uses.

Solder Wire Video

Great write up.
I would add:

Keep handy a pump dispenser of isopropyl alcohol of 99%, as well as good old fashioned q-tips. This is to clean flux residue and general debris. Solder doesn't like gunk.

Solder wick is THE ONLY way to effectively clear through holes that are filled with Solder. Always remove old solder when doing repairs. Put a little flux down before using wick, it REALLY helps.

With our type of soldering, the solder is too thin to carry a significant amount of flux in its core, making it tough to get a good joint without a touch of extra flux. I like the chip quick syringe. Not as thick and sticky as the MG chem syringe, and nice and cheap. Cleans OK, too. The "shoe polish" tubs are useless, and flux pens don't give the precision or bang for buck. Always use flux. Period.

Also of note: if you are using a cheap iron, chances are it's not representing its temp accurately. I solder hot and quick as well, and 400c seems plenty, unless it's a high thermal mass joint. In that case, I will either swap tips to a tip with more volume/thermal mass or I will load up solder on the one I'm using, which temporarily boosts its thermal mass, allowing me to make the joint. Crap irons are great, just don't trust them on temp.

Again, great write up here. It drives me up the wall to see fpv youtube people (Bardwell, I'm looking at you!) Give half assed info on the subject whilst acting like they are the authority on it.

Additional youtube resources to check out:
Livyufpv does detailed board level repairs on his channel, and is the only fpv channel I've found on that level.

Louis Rossmann owns a macbook repair (logic board level repair and smd rework with hot air) company in NY and posts/streams repairs that you can learn quite a bit from, if by osmosis.

Any questions are welcome.

Thanks. 

Hey Harry nice peice of work you got here ! I'm no solder expert so I like to try to improve when I can I've read your article I'll agree with everything and add in that I usually get a better heat transfer if I apply just a touch of solder to the tip of the iron but still once that iron touches the pads my nerves start freaking out like ridiculous in practice I could do it just as good as anyone but in reality my hands go to shaking solder starts smearing etc etc by the time I get the wire solder I'm like dang bout friggin time so I figured out just solder the dang thing if it works then good if not fix it don't over think it

Hi Joey, Thanks.

2021-11-09 Update:  video added to POST #4

Solder wick has never worked well for me. My desoldering gun works great for sucking old solder off of pads and clearing out solder on through hole bits.

I’m always a bit shakey, so a circuit board holder or blue tack works great to hold the components/board/wires. I hot glued some wooden clothes line clips at various angles to a small piece of wood with some blue tack in the middle, makes it easy to clip wires into position on the board that’s stuck in the blue tack. That allows me to have solder in one hand and the iron in the other, and rest the outside edge of my hands on the bench to keep me steady.

Except for the clothes pins, that is the way I do it.

I like the close pin idea, think I will have to try that.

Solder wick is also like solder, the cheaper stuff just doesn't work that well. Not sure what the deal with some of it is if the rosin/flux that's in it dries up or wasn't enough to start. It needs good flux to flow the solder up the braid. As mentioned, you may need to crank up the iron as the wick will rob the heat from the tip like a ground pad.

I was watching a classic video game channel and he gave a good tip on a good desolder pump. I always hated the ones with the plastic tips and they were only really good for heavy blobs of solder like what would be on the pins of a heavy transformer. This one uses silicone tubing so when it ends up melting you can just replace it with a new piece. I've not tried this but I'd pick it up if I was still doing board level work:

https://www.amazon.com/VT-001-SS-Aluminu...B0849MCLDW

I use an electronic desoldering gun with a temperature controllable tip and an electric pump.

It’s not worth the investment if you’re solely working on quads, but I used to do a lot of repair/restoration work on vintage hifi gear.

So far, the only thing that I have used, and only on rare occasions, is a wick 
and then only when I need to suck up a lot of solder which is actually rare. 
I just use my normal "cheap" soldering iron which seems to work fine most 
of the time. I do have one of those syringe things, but I have never actually 
tried to use it. It just looks like more hassle than it is worth. Maybe one day 
when I have time to tinker. Ha, Ha.

(31-Mar-2021, 08:43 PM)Roamfpv Wrote: It drives me up the wall to see fpv youtube people (Bardwell, I'm looking at you!) Give half assed info on the subject whilst acting like they are the authority on it.

I couldn't agree more.  I'm amazed at the number of soldering tutorials out there with no-one taking any anti-static precautions at all  (Bardwell, we're all looking at you now !).