Mechanical versus Solder connections

[Mojave]

I have been reading forum posts for about a year, looking at current threads and researching the archives. I have seen mention of soldered connections versus mechanical connections; some have argued that mechanical (crimped) connectors last longer than solder joints on our vibration prone UAVs.

For the life span of our rigs:
- does anyone have strong feelings about which is best and why?
- has anyone observed solder joints failing on their UAV?

 

[Av8Chuck]

I have been reading forum posts for about a year, looking at current threads and researching the archives. I have seen mention of soldered connections versus mechanical connections; some have argued that mechanical (crimped) connectors last longer than solder joints on our vibration prone UAVs.

For the life span of our rigs:
- does anyone have strong feelings about which is best and why?
- has anyone observed solder joints failing on their UAV?

I don't have the answer to your question but I do own an airplane and I know that the FAA will not certify anything that has solder joints in any part of the primary flight control system. None of my avionics are connected with solder joints either. I don't know which is better or what kind of mechanical joints are available but I can take a guess which type of connection the FAA will certify.

I also believe that the DJI S900 has some mechanical connections build into it but I've only seen pictures so I don;t know about that either.

Sometimes I wonder why I bother posting...

 

[Mojave]

I don't have the answer to your question but I do own an airplane and I know that the FAA will not certify anything that has solder joints in any part of the primary flight control system. None of my avionics are connected with solder joints either. I don't know which is better or what kind of mechanical joints are available but I can take a guess which type of connection the FAA will certify.

I also believe that the DJI S900 has some mechanical connections build into it but I've only seen pictures so I don;t know about that either.

Sometimes I wonder why I bother posting...

Thanks Chuck - [MENTION=736]Tahoe Ed[/MENTION]; could you address this issue with the DJI S900 (maybe with some photos)?

 

[Tahoe Ed]

Thanks Chuck - @Tahoe Ed; could you address this issue with the DJI S900 (maybe with some photos)?

The lipo connection is soldered as are the ancillary connections for other components. However, the motors are a mechanical connection but the connectors are soldered to the trace in the bottom plate. Because of space limitations, I am not sure if we will ever get away from soldering. The connections between components is all crimped and in some cases encased in a moulded cover. Here is a shot of the S900.

 

[Mojave]

The lipo connection is soldered as are the ancillary connections for other components. However, the motors are a mechanical connection but the connectors are soldered to the trace in the bottom plate. Because of space limitations, I am not sure if we will ever get away from soldering. The connections between components is all crimped and in some cases encased in a moulded cover. Here is a shot of the S900.

Thanks for the quick reply Ed. That layout is a sweet hybrid of soldering and mechanical connections. Here in Las Vegas we have an electronic supply outlet store: Kiesub Electronics. The staff got to know me while I was building my F550. I bought shrink wrap, velcro, and some soldering supplies there. They have an assortment of crimp spade male and female connectors and there is a plethora of other styles available. At the time I did not wish to go against the soldering trend. Now I am trying to see if there are others that are using the mechanical connectors that are available.

 

[cootertwo]

I ain't no electrical engineer, but in my opinion any kind of a crimped connection is about the same as holding the wires together with you fingers. Where as a "properly" soldered connection offers far less resistance, and far less chance of corrosion. An example would be a crimped battery connection on your car. They work, but after awhile, if you cut the shrink wrap off, you'll see all kinds of green stuff growing. I've NEVER had a soldered battery connection fail on a car/truck/motorcycle, but have had to replace many crimped connectors after complaints of hard/slow starting problems.:tennis:

 

[channel 1]

I ain't no electrical engineer, but in my opinion any kind of a crimped connection is about the same as holding the wires together with you fingers. Where as a "properly" soldered connection offers far less resistance, and far less chance of corrosion. :tennis:

Since I am new here I figured "what the heck chime in on this one."

Generally speaking, for the hobbyist a properly soldered connection is a better deal, versus in the production world where a crimped connection is the only way to go.

The problem on the hobby side with a crimped connection, is as you stated maybe the wires are set tight, maybe not, and maybe not is not too cool.

While a properly crimped connection is equal to or better than a soldered connection, to properly crimp such a connection requires a tool designed for that connector and the real ones can be a few hundred dollars or more, for a hand operated tool, and that prices it out of the budget of the hobbyist, so a universal crimp tool is utilized and they often produce improperly crimped connections.

So what is hobbyist to do, if possible find and utilize solder type connector inserts, now many times that is not possible so the next best thing is to use a crimp type insert, then using a universal crimp tool, crimp but do not over-crimp the conductor and solder the crimped connection.

Now when doing this be very careful to not allow solder to wick up under the insulation where you will be making the second crimp of the wire retaining tabs, if solder wicks up under the insulation it can form a solid to stranded transition outside of the wire retaining tabs and this combined with vibration will become a point of failure and a hidden under the insulation intermittent point of failure at that.

Wayne

 

[Mojave]

I ain't no electrical engineer, but in my opinion any kind of a crimped connection is about the same as holding the wires together with you fingers. Where as a "properly" soldered connection offers far less resistance, and far less chance of corrosion. An example would be a crimped battery connection on your car. They work, but after awhile, if you cut the shrink wrap off, you'll see all kinds of green stuff growing. I've NEVER had a soldered battery connection fail on a car/truck/motorcycle, but have had to replace many crimped connectors after complaints of hard/slow starting problems.:tennis:

Cooter - many of the connections we now have in our multirotors are mechanical connections (molex plug modules) these include the ESC connections, the connections from our radio receivers to the flight controller, etc, and these seem to work pretty well. I understand that many of the critical piloted aircraft connections are mechanical. As pointed out elsewhere these crimping tools are not inexpensive. I am not sure that the lead acid systems in our vehicles are analogous to our lithium polymer systems used power our multorotors. I to have had mass produced mechanical connectors fail as well as soldered connections.

I would like to know if others have observed mechanical or solder connections fail on their UAV or radio controlled aircraft, and if it is common.

 

[Mojave]

Has anyone observed failures of soldered or mechanical connections?

Since I am new here I figured "what the heck chime in on this one."

Generally speaking, for the hobbyist a properly soldered connection is a better deal, versus in the production world where a crimped connection is the only way to go.

The problem on the hobby side with a crimped connection, is as you stated maybe the wires are set tight, maybe not, and maybe not is not too cool.

While a properly crimped connection is equal to or better than a soldered connection, to properly crimp such a connection requires a tool designed for that connector and the real ones can be a few hundred dollars or more, for a hand operated tool, and that prices it out of the budget of the hobbyist, so a universal crimp tool is utilized and they often produce improperly crimped connections.

So what is hobbyist to do, if possible find and utilize solder type connector inserts, now many times that is not possible so the next best thing is to use a crimp type insert, then using a universal crimp tool, crimp but do not over-crimp the conductor and solder the crimped connection.

Now when doing this be very careful to not allow solder to wick up under the insulation where you will be making the second crimp of the wire retaining tabs, if solder wicks up under the insulation it can form a solid to stranded transition outside of the wire retaining tabs and this combined with vibration will become a point of failure and a hidden under the insulation intermittent point of failure at that.

Wayne

Wayne - good points above - thanks. I am not sure about the price tag of a good crimping tool; I spent a lot on my soldering iron. For folks that put together multirotor systems for a living or make their livelihood flying systems; another tool may not be a deal breaker.

Sometimes I wonder if soldering vs. mechanical is an issue or not. Has anyone observed failures?

Following the KISS principle (Keep It Simple Stupid or Parsimony). I would like it if I did not have to play with a hot soldering iron and worry about breathing flux; just strip wire and squeeze metal connections to hold the wire in place. The current building norms that we are exposed to here and in the small UAV systems we read about have solder as the normal process that we participate in. All those molex and other 'micro' connectors are done en masse in huge batches and we purchase them pre-made.

Are the failures of solder vs. mechanical significant in our community? And of course will the FAA make this an issue if, or when they get involved?

 

[cootertwo]

Yes, and yes, but I just got done trouble shooting a video problem on my mini. Turned out to be a loose mechanical connection where the lead from my camera, plugs into my Immersion TX. In automotive, motorcycle etc. "spade" type connectors are used all over the place, and if in a connection where they get heat, cool, heat, cool, etc. etc. they tend to loose their tension, and you can either try to bend them a bit to make them fit tight again, but best to replace. On my little mustang race toy, I decided to solder everything I could when re-wiring, rather than use spade and eye crimp connectors, and where I had to use eye connectors on the gauges, etc, I soldered them after crimping. BUT, the solder makes the wire stiff where it exits the crimp, and can easily break if it gets moved around too much. Sometimes you just can't win.:black_eyed:

 

[scotth]

I don't have the answer to your question but I do own an airplane and I know that the FAA will not certify anything that has solder joints in any part of the primary flight control system. None of my avionics are connected with solder joints either. I don't know which is better or what kind of mechanical joints are available but I can take a guess which type of connection the FAA will certify.

I also believe that the DJI S900 has some mechanical connections build into it but I've only seen pictures so I don;t know about that either.

Sometimes I wonder why I bother posting...

The biggest problem is that people confuse solder with glue. Crimp style connectors are more reliable than soldered joints when done correctly with the correct tool. Not the one from Radio Shack.

 

[RotorJockey]

In the mid-60's I was involved in building Piper aircraft from CKD (completely-knocked-down kits) - Cherokees, Tri-pacer, and others. ALL the general electrical connections were 'quick-disconnect' crimp. They are constructed so that both ends are the same, 90 degree attach and slide to straighten and hook on to each other, which cleans and seals the mating area. Then a plastic sleeve or heat-shrink is applied. There are still Cherokee 140's, 235's, and Sixes flying with those original connectors. A proper crimp connector fuses at molecular level.

Solder, on the other hand, is very 'plastic' in nature. Place a length of solder under constant pull-stretch, and it will elongate at a steady rate until it snaps - a time fuse perhaps? Lay-on solder joints can display this characteristic. The raw wire has to be firmly wrapped around the connector and liberally doused with solder. The solder only serves to increase the contact area and help to hold the connection made.

Elsewhere, I've explained about losses across connectors and solder joints. Across any length of wire there is resistance; so also, across any joint there is a resistance - be it solder or mechanical. This is why there are differing gauges of wire - to lower the resistance, where V=I x R. V=volts, I= current (Amps) and R=resistance in Ohms. Alternately, W=V x I, where W is the power in watts generated over any resistance where a voltage is applied.

Food for thought?

 

[Carapau]

Given the life of most multirotors at this stage and the general need that most people feel to upgrade once in a while I think that what is best is almost a mute point. By the time a good solder joint is likely to fail or a crimp connection is becoming dodgy your average MR owner would have either moved on to a newer machine or, heaven forbid crashed. The joints all last a long time if done properly- years. Who here reckons they will be flying the same machine without having modded or upgraded it in 3 years time?

I have used Anderson Powerpoles with the genuine Anderson crimping tool. These connections are awesome and so quick to do. No chance of cold solders. But that said, I also have a good soldering iron and can solder reasonably well. Given a choice I would go with crimped connectors everytime but space being the premium it is on MRs mean that often soldering is the best bet.