How Do I Solder DC Motors With Flimsy Copper Pieces To Wires?

Hello all, brand new to soldering and I was hoping somebody could explain the proper way to solder wires to the flimsy copper "flaps" that stick out of the ends of the motors? They are small motors that came with a Tamiya twin motor gearbox and I believe they are "Type F130" motors or something like that.

I've been reading soldering tutorials and watching YouTube videos so I know the basics in theory (waiting on a few supplies to arrive in the mail before I can start practicing). That said, I'm confused about how to properly do this type of solder joint.

Would I hold the solder on the copper piece and heat the copper piece to "tin" it? If so, wouldn't the copper heat up and melt the plastic housing of the DC motor? Or not?

Should I solder with regular hook up wire (I have single solid wire, 22 AWG) or should I solder some male-to-male jumper wires (also 22 AWG) with the already tinned ends to the copper flaps? I have Kester electronic rosin core solder that is 60/40 (tin/lead).

Here is a link to a picture of the motors, you can see the little copper flaps I am talking about. They seem pretty fragile, I'm concerned about breaking them. http://www.pololu.com/picture/view/0J2740

Also, is there a way to determine which flaps are positive and which are negative? I have a DMM I'm just not sure how to check this yet.

Is this the correct way? To bend the wires like this or should it be flat or what? http://www.youtube.com/watch?v=xSWKnnvGWBs

Thank you to anyone who can advise me on this.

Just solder it up, that plastic is quite tough.

is there a way to determine which flaps are positive and which are negative?

All that changing the polarity does for a motor is change its direction so wire it up and see what way it spins. If it is wrong then swap the wires over.

Grumpy_Mike: Just solder it up, that plastic is quite tough.

Personally, I would not bet on that.

Ensuring the tabs are clean is perhaps the first most important thing - a gentle polish with steel wool whilst holding the motor so that the tabs point down and any debris from the steel wool falls downward and away from the motor as you do this. Actually, that is probably not such a good idea to do with a motor as its magnets will tend to attract the steel wool. A cleaning compound such as "Jif" may be more appropriate, applied in a "pinch" on a damp cellulose sponge, also whilst holding the motor so that the tabs point down and any moisture drops away, then completely wiped off with a rinsed sponge.

The skill in soldering is to apply the iron to the tab and touch the solder not to the iron and not just to the "work", but to "wedge" the tip of the solder to the very angle where the iron is actually contacting the work so that the solder as it melts, immediately conducts the heat from iron to work and flows in the capillary between.

And - you are using too heavy a gauge of solder; finer gauges release more flux.

KalELonRedkryptonite:
Hello all, brand new to soldering and I was hoping somebody could explain the proper way to solder wires to the flimsy copper “flaps” that stick out of the ends of the motors?

They are not flimsy copper, they are phosphor bronze, a tough alloy used for hard wearing
electrical parts and springs - here the spring that presses the graphite brushes against
the commutator.

As with all soldering it is vital to have an iron that is hot enough, enough flux, and be quick.

MarkT: be quick.

This.

MarkT: They are not flimsy copper, they are phosphor bronze, a tough alloy used for hard wearing electrical parts and springs - here the spring that presses the graphite brushes against the commutator.

As a kid, I took apart a number of these cheap toy 3-6 volt motors to know that there aren't any "graphite brushes" contacting the commutator; I don't know what the material is (could still be phosphor bronze), but inside the motor, it's basically just a simple strip of metal that contacts the copper commutator, nothing more than that.

You don't start to see graphite or carbon brushes on small motors until you start to spend more than 99 cents per each...

When you get your supplies, practice soldering wires together. The trick to solder tiny things embeded in in soft plastic is proper preparation. Test the plastic to get an idea of how easily it melts. Touch the iron tip against a non-critical spot on the motor body, noticing what it takes to melt it. It won't be much. Practice tinning two wire ends. You should be able to quickly add solder to the ends leaving just a tiny ball of solder on the tips of each of 2 wires. Then practice attaching the 2 wires by touching them together and very quickly remelting the solder on them to make it all flow together. Smile ya done good.

Take a sharp knife point and scrape the oxide coating from the solder terminals on the motor. Close inspection should show a mostly shiny surface. Tin the terminals. Remember how quickly the plastic melts and don't linger anymore than necessary.

Tin the wire. Melt the 2 together. Then do the other one. Congratulate yourself and celebrate with an adult beverage.

Brushed DC motors are ambidexterous. Attach the wires to a battery of the appropriate voltage and it runs in one direction. Reverse the wires on the battery and it will run the other direction.

Have fun. You just learned something that less than 1 in a 1000 people know how to do.

Stay away from that Red Kryptonite. It's evil stuff.

John

Do I need flux if the solder says it has a rosin core? Isn't that flux?

If you want repeatable success, whether there is flux in the core or not, use a flux pen or similar

Rosin core means after you have melted some solder, some flux gets on the part and then the solder starts to bond.

By putting flux on the parts beforehand, the solder bonds immediately when the parts and solder is hot enough. This gives you more instant bonding which is important when dealing with tiny parts, particularly when they are mounted on meltable plastic.

John

LarryD:
If you want repeatable success, whether there is flux in the core or not, use a flux pen or similar

I would disagree.
I never use extra flux, the flux in the core should be enough. If you must use extra flux make sure it is not corrosive like stuff for plumbing is.

I'm with Grumpy Mike on the extra flux being extraneous, but it probably wouldn't hurt as long as it doesn't get into anything. But it might help more if you have a mediocre soldering iron. Really the two biggest things is to minimize contact to the motor. While it is designed to be soldered to, it also has limits (which it probably says in a datasheet somewhere that may be inaccessible). That being said, you do want a good solder joint, which the easiest way is to tin both the wire and the motor, then solder the two together so they are all in one continous piece of solder. It should be shiny, and cover both parts (Though with the motor tab, the part is basically one side of the tab.) I would also recommend using heat shrink to cover the joint to reinforce it, and also figure out a way to strain relieve your wires as close to the motor as possible, as that joint will eventually break if left unattended, since motors tend to vibrate. Basically, you want there to be no force being applied to the joint in any direction, or it may just break off after being used for a while.

mirith: the easiest way is to tin both the wire and the motor, then solder the two together so they are all in one continuous piece of solder.

I had a mind to comment earlier - it is not a bad idea to tin both the tab (both sides) and the wire, not leaving any more than a thin coating of solder - "wiping" the solder off with the iron is one of those skills. I always twist stranded wire before tinning, and pull back the insulation which will slip over again after tinning.

Then fold the wire over the tab - or insert it through the hole if there is one and (gently) crimp it over the tab, then you can quickly solder them together, adding a little.

For electrical work, you always use rosin core colder. As previously explained, finer solder gauges are preferable and provide plenty of flux.

I don't know what gauge my solder is, but it does say "hi-tech electronic" and "for electronic repair" on the container.

2 mm or so sounds about right.

Paul__B: 2 mm or so sounds about right.

That is way big. I go for the smallest you can get, normally 0.8mm or smaller.

The latest person I got to try the small stuff said to me last month:- "I can't believe I spent so long soldering with the big stuff, this is so much better"

Grumpy_Mike: That is way big. I go for the smallest you can get, normally 0.8mm or smaller.

OK, OK, I was talking through my hat and guesstimated wrong. I was browsing at work, away from my "hobby" workpile.

The two gauges I have are actually 0.75 and 1.1 mm, and the finer is preferred.

Grabbed a spool of real leaded solder at a garage sale a few weeks back. That will keep me going.

Grabbed a spool of real leaded solder at a garage sale a few weeks back. That will keep me going.

Farnell still sell it.

Paul__B: The two gauges I have are actually 0.75 and 1.1 mm, and the finer is preferred.

As was mentioned... Clean is important. If something doesn't look bright-shiny clean it will be a -little- harder to solder. It'll still work but part of the job of the flux is to remove oxide. The drawback of keeping the heat on to burn through the oxide will, as seen in your video, much more easily melt the wire insulation. But common hobby wire insulation is such crap there's generally nothing you can do about it.

As was mentioned, yes, aim the solder where the iron touched the metal you're soldering. The iron heats the part(s), then you touch the solder in and as -that- heats up the rosin core melts and flows into the joint and does its cleaning job. Then the solder flows.

You pulled the iron away kind slow/gently. Try to pull it out as quickly as possible, with a bit of a snap-wipe along the wire. You don't want the iron to 'keep on heating' the joint - you want to get the heat away and let it start cooling as quickly as possible.

--- > And the real reason I'm replying to this... There are -two- important reasons you want to use an 'appropriately' sized solder. The larger stuff was too big because 1) the joint doesn't -need- that much solder, and 2) between the time you touch the solder to the joint, till it melts, it is actually sucking heat -out- of the joint. Yet, the wire/motor/whatever is still pulling heat -into- the part. The idea is to touch the the iron to the part, heat it up quickly, get the solder in quickly, and get the iron out. The intent is to avoid applying too much heat to the part. Typical Rat Shack connectors are HORRIBLE because you can't get the solder joint done before the whole plastic housing falls apart.