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Author Topic: Tinning ESC and Motor Wires  (Read 439 times)
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Buster11
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« on: February 14, 2019, 07:43:14 AM »

I'm having some difficulty in tinning ESC and motor wires after shortening them. As supplied, the ends are properly tinned, but when shortened the wires, which have silvery-coloured strands, are very resistant to tinning. I'm using proper (as opposed to low-lead) resin-cored solder, and a 25 watt iron. Any suggestions? I'm reluctant to use the paste flux which I use for steel and brass as I'm not sure about subsequent corrosion problems.
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frash
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« Reply #1 on: February 14, 2019, 12:21:43 PM »

Use rosin if you can.

The experts say that the acidic flux for "hard" soldering is not good for electrical work. I am NOT an expert.

Fred Rash
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DavidJP
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« Reply #2 on: February 14, 2019, 12:47:04 PM »

I don't recall having trouble with Bakers and my last "tin" was 30 years old before I had used it all - but then have also used cored solder with no problems.  Certainly I share th view that "hard solder flux" is not good at all.
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Konrad
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« Reply #3 on: February 14, 2019, 01:31:04 PM »

If you shortened the enameled/epoxy wires you will need to clean off this insulation. This is best done with an acid. You don't want to scratch the copper. Then it is best to passivate the copper with a base to get a neutral PH.

If you are dealing with the flexible multi stranded extension leads it is best to use a non-acid rosin to help clean the strands an carry the heat to the adjacent strands. The number one problem with soldering is using too little heat! This can be to low a temperature or soldering tip that doesn't have enough thermal mass (soldering gun tip are a classic form of this problem) What size (weight) is your soldering tip?

Clean off all (Any) fluxes (rosins) prior to heat shrinking. I like alcohol as my flux cleaner.

Does your past flux etch your brass work? If not then it isn't likely to be much of a problem with the copper ESC PCB etch.

Sometimes you are forced to use acid fluxes; but neutralize and clean well after.
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fred
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« Reply #4 on: February 14, 2019, 05:58:11 PM »

Yeah it would tough to tin Varnished insulation Motor wires  Grin
 Simply scrape the varnish off with a #11 blade ..'till nice 'n shiny.
 It works .. reliably.
Been fooling with motors and wires for decades.
 There is no easier, more direct method.  But yer welcome to try
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Buster11
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« Reply #5 on: February 14, 2019, 06:29:15 PM »

Thanks for the suggestions. Meanwhile I've done a spot of Googling and one intriguing idea is to lay the wire on an aspirin while applying the iron. Aspirin is, of course, salicylic acid and the heat releases this to remove the insulation. I'll give it a try.

A related point of confusion that's come up in some replies. Acid fluxes, like Baker's Fluid in the UK, are not for hard soldering, but used for metals like steel or brass when soft soldering. Hard soldering fluxes are often borax based and the powder is mixed to a paste with water and then used with a butane torch or similar and with silver solder or brazing spelter, which needs the metal to be near red heat to flow.
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Konrad
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« Reply #6 on: February 14, 2019, 09:33:15 PM »

Thanks for the suggestions. Meanwhile I've done a spot of Googling and one intriguing idea is to lay the wire on an aspirin while applying the iron. Aspirin is, of course, salicylic acid and the heat releases this to remove the insulation. I'll give it a try.

A related point of confusion that's come up in some replies. Acid fluxes, like Baker's Fluid in the UK, are not for hard soldering, but used for metals like steel or brass when soft soldering. Hard soldering fluxes are often borax based and the powder is mixed to a paste with water and then used with a butane torch or similar and with silver solder or brazing spelter, which needs the metal to be near red heat to flow.
Aspirin has never worked for me. Mechanically removing the varnish insulation has always damaged the wire. A #11 blade gives me the worst possible results. I've been known to use a very fine melamine foam sponge.

Never heard the term "hard soldering". On this side of the pond I think we use the term brazing.

If you are finding the wire in multi-stranded wire it is a problem to solder it is likely a heat problem. Are you using a 5mm or wider chisel point tip? A small pencil tip isn't likely to transfer enough heat the the wires to flow any solder. Pencil tips are best for light PCB work.
« Last Edit: February 14, 2019, 10:05:26 PM by Konrad » Logged

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Don McLellan
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« Reply #7 on: February 14, 2019, 09:58:31 PM »

I've always used Lucky Bob's flux for soldering steel wire, brass, and aluminum wire without an issue.  (Just remember to clean the surfaces a little prior to soldering).  I believe it is a slot car product, so you may have to hunt around for it.  Also not sure if there is a UK equivalent, but is available from North American slot car suppliers. 

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USch
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« Reply #8 on: February 15, 2019, 07:25:01 AM »

Maybe we are mixing up things which are best kept divided.

First and most important for modellers is soft soldering as the use of, for DIY applications, an alloy of 60% tin and 40% lead with a melting point of 191°C. Dont care about lead-less solder, that's mainly for industrial electronics and more difficult to use. Soldering must be divided in soldering of electronic components and soldering of materials like steel, stainless steel and aluminium. Electronic soldering means ANY soldering of components, wires, connectors in electrical conducting systems. It also means the material to be soldered is mainly copper, copper plated metal or brass which has a very weak oxidation layer, easily destroyed by a faint, no acid, flux. Having to solder steel and/or aluminium you will use an acid based flux but treat it as a different work respect to the electronic soldering, maybe even with a different soldering iron! Because the acid will easily destroy your fine soldering tip and his plating.

Hard soldering, as called over here, is brazing, normally with a torch, at far superior temperatures and silver solder with melting points of over 600°C. Also the flux is different as the one for soft soldering.

The original question however was how to tin copper wire which has some platting for electronic purposes. As Konrad said it is mainly a temperature and mass of the tip problem. To small a tip and you cannot transfer enough heat to the to be soldered work. Set the soldering iron to 300-350°C. Remember also to create always a "bridge" of fluid tin between solder-tip and work so as to have a large surface for transmitting heat. I remember Graupner for some time had plated multi-stranded wire on there JR connectors which gave some problem for tinning, but also then heat and mass did the job.

A last remark about shortening the wires of brushless motors. That's a real problem because the wires are isolated by a temperature resistant coating. Mechanical abrasion is difficult because of space and multiple wires. Professional builders of motors use high temperature solder, over 400°C melting point, lead, tin and silver as components. This solder burns away the varnish during tinning. Try to find such a solder in a specialised shop.

Urs
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Konrad
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« Reply #9 on: February 15, 2019, 10:01:14 AM »

Urs, Nice remarks.

As this thread is about power leads as part of the motor and ESC, here is a technique I like to use. I found this from the motor firms Aveox and Neu.

I hate the lap joint often seen with wires. Unless one takes the time to wrap the lap joint with thin copper wire the mechanical or electrical contact area is less than ideal.

I like to use a brass tube as my splice coupler. This offers a lot of mechanical and electrical of contact area to the joint. It also has the benefit of keeping the cross section of the splice very close to that of the original wires. This makes it easy to thread the wires where they may need to go in the airframe.

All the best,
Konrad

P.S.
I'm finding that the new formulations of lead free solder actually flow out better than the classic 60/40 of old. Yes, they still need a bit more heat than the 60/40 solder.
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VictorY
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« Reply #10 on: February 15, 2019, 02:58:15 PM »

In my experience a large tip just gets in the way when working in tight spaces unless you are making stained glass windows and need massive amounts of transfer. I get plenty of heat transfer through a 3mm chisel tip on my Hakko 936, enough to do the largest connectors in the rc business. It's more about the quality of the iron and technique. Buy a good one and it will be the last one you spend money on. Look for something with a ceramic heating element. The 936 is only available as a clone now and you have to know which one to buy in order to get the good components, so I recommend the FX-888D. I'm still on the original tip after 15+ years. Smiley
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Buster11
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« Reply #11 on: February 15, 2019, 05:48:14 PM »

 That's a real problem because the wires are isolated by a temperature resistant coating.
[/quote]

Urs, that's what's puzzling me. Why would the individual strands within each cable need to be themselves insulated from each other? One would think that having the strands in electrical contact with each other would be what's needed. 
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Konrad
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« Reply #12 on: February 15, 2019, 06:00:59 PM »

Urs, that's what's puzzling me. Why would the individual strands within each cable need to be themselves insulated from each other? One would think that having the strands in electrical contact with each other would be what's needed.  
Buster you are thinking correctly. But the reality is that there are often many individual wires in each bundle. This is done to allow the wires to actually be able to be wound on the stator.

You want to remove the insulation coating from each wire for 360° to make sure you have good electrical contact with the lead, leading out to the ESC.

Now you want the insulation on the wires so that the windings aren't shorted to each other as they go around the stator.
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Buster11
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« Reply #13 on: February 15, 2019, 06:51:03 PM »

 Konrad, you say "But the reality is that there are often many individual wires in each bundle. This is done to allow the wires to actually be able to be wound on the stator."

The several individual strands of wire in the cable connecting the motor to the ESC are silver-coloured; the insulated wires on the stator are copper. They are not the same.
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USch
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« Reply #14 on: February 15, 2019, 07:21:33 PM »

….. the cable connecting the motor to the ESC are silver-coloured; the insulated wires on the stator are copper.....

I guess the silver coloured wires are nickel-plated copper, but still "tinnable".

The fact that the copper wires coming from the motor are insulated has to do that instead using a big diameter wire for the windings it is mechanically easier to use a number of smaller diameter wires to make up to the needed cross section. Another explanation is that the current runs on the circumference of the wire and for a certain section multiple wires do have more circumference than a single wire.

Urs
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Konrad
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« Reply #15 on: February 15, 2019, 09:27:39 PM »

Urs covered it well.

Generally the heavy gage copper wire is part of the wire under the magnetic fields of the magnets. (In motor theory you would be looking at cooper vs iron losses).

The wire made up of small multi strands can be thought of as leads and generally need to be much more flexible for their intended application (joining the motor to the ESC).

This is why we don't want to nick the heavy copper wire as there is still some force (Vibratory) that will allow force concentration to build up failing the cooper winding wire. When this happens the motor repair is often very difficult in not impossible without a total rewind of the motor.

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DavidJP
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« Reply #16 on: February 16, 2019, 05:26:59 AM »

That is very interesting Konrad &Urs.  Thank you.  It does help me understand the occasional problem I have had.  But largely I have used cored solder for very many years on wiring and small components.  Bakers I used for larger things like piano wire undercarriages or brass sheet etc. 

Silver soldering I have used baking powder on occasions but then bought a small pot at anexhibition years ago.  On another occasion l have used a “paste”.  I do not recall any failures save those due to sloppy workmanship. 

I suppose then I have benefitted from beginners luck and ignorance is bliss?  However no excuses now for not trying to do it properly.
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