Bad Solder Joints - cause and effect

[Solitaire]

nunyabizniss34 posted this on another site and I thought I would copy it here. Very good info and I've experienced this on a couple of installs. I hope you don't mind, Colin...

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Here is what Lucien from Innov8tive has to say about this. It's lengthy but very informative, especially the last few paragraphs.

Quote:
"Whenever a motor just quivers back and forth when power is applied, it means that you are only getting power on 2 of the 3 phases. In brushless motors, power is applied between phase A and Phase B, and the motor will rotate to the next magnet. Then power is applied to phase B and C, and the motor rotates again to the next magnet. Then power is applied to phase C and A and the motor again rotates to the next magnet. Then the process repeats again through another phase cycle. When one phase loses connection, the motor will go forward one magnet, then sit still for a cycle, then back up on magnet, then go forward one magnet. When this happens, the motor just quivers back and forth instead of rotating.

The problem with this is that when the motor does not rotate, to the speed controller it appears as a dead short, and will draw a ton of current if you advance the power to full throttle. This will cause the motor, speed controller or both burn up if it is left in this condition for more than a few seconds.

There are a few different causes for an intermittant connection. The most common reason is a bad or cold solder joint on one of the bullet connectors, either on the motor or ESC. Recently I have seen a lot of spped controllers stop working because of a cold solder joint on one of the bullet connectors that the user installed themselves. I must digress at this point and give a bit of history on soldering to explain what is going on here.

Virtually all of the speed controllers that are being manufactured today are done so under the "ROHS" act, which stands for Reduction Of Harmful Substances. In electronics, this means that the products are manufactured so they are free from heavy metal contaminants such as lead and mercury. For speed controllers, this meand that the solder used to assemble the components and solder on the lead wires contains no lead. This solder melts at a higher temperature than conventional tin-lead solder does, and this can cause problems when the two solders are mixed.

Typically, speed controllers come with the lead wires pre-tinned from the factory to prevent fraying of the wire strands. Most people figure that since they are pre-tinned, they are ready to go. Many people will simply slide a bullet connector onto the end of a ESC lead wire and then heat up the bullet connector with a soldering iron until it gets hot enough for solder to start melting. Then they add the solder until it fills in around the wire and pull away the soldering iron. When a connector is soldered this way, in many cases, the wire itself does not get hot enough for the solder on it to melt, since the ROHS solder melts at a hotter temperature than the typical solder that the modelers are using. In the end, you get a wire that is embedded in a glob of solder on the end of the bullet connector that has a mechanical connection only, and little or no actual electrical connection.

A solder joint done this way my work OK for a while, but after you run current through it for a while, and throw in a little vibration, the solder joint will fail. When this happens, the motor locks up, and if it is above half throttle, about 2-3 seconds later either the motor or ESC burns up. I have gotten quite a few speed controllers back from people recently that said everything was running fine, and they were only pulling about 2/3 of the rated current through the speed controller, when suddenly on the 20th flight of a model, the speed controller blows up. They send the speed controller back to us under warranty, and when I get it, I wiggle one of the bullet connectors and it pulls right off the wire in my hand.

When I call the customer and tell them that a bad solder joint was the cause of their speed controller failure, they usually tell me that they have been soldering for 20 years, and there is no way a bad solder joint caused the ESC to fail. It happens all the time, because many of the "Old Time Solderers" are not familiar with the new ROHS typs solders and do not take the proper steps to get a good solder joint.

Now sometimes, there will be a cold solder joint on the motor as well. It is rare, but when someone sits at a bench all day at the factory, and solders several hundred bullet connectors in a day, every once in a while they will get a bad one. So if you check the ESC bullets and the problem still exists, you can check the motor bullets as well.

Hopefully that will get you going!"

Lucien

[akent]

This is an excellent description of what can happen with ROHS pre-tinned wire leads that I have seen more and more often.

If you are soldering with tin/lead, it is always a good idea to cut off the pre-tinned section of the wire and start off with bare wire.

I hate ROHS, personally, but I have to deal with it all the time on circuit boards. I cannot hand solder ROHS nearly as well as tin/lead.

It is a shame that there are so many different types of connectors used with our models.

What would help tremendously would be a sheet of paper included with each and every motor and ESC on how to properly solder connectors onto the wires.
Kent

[19000rpm]

I guess that this means you really need to re-solder everything that comes from the factory. I've had a few bad ones on ESC's. What a pain.

[shakey]

I am glad you posted this, I have had one of my 450's doing this recently. It started after about 4 flights. For no reason at all, about 1/2 throttle it would start missing. I don't know if it should do it all the way through if it is a bad joint, but just does it at 1/2 throttle. So I will check all the connections.

Sorry I have not been around lately, but have had a lot going on.

[Dave]

Jun 21, 2011 17:01:34 GMT -6 shakey said:

..............Sorry I have not been around lately, but have had a lot going on.

Shame on you shakey
All in favor of shakey buying everyone a new heli for missing so many days say "I"



Glad to have you back with us shakey

Dave

[shakey]

Thanks Dave, It has been really hecktic. Now this morning, my wife went for her normal walk in the park and had a seizure. When she fell, she broke her arm, so we spent the day at the hospital. When will it ever end??? I thought bad luck came in 3's. We are working on about 20 now. Arrggghhhh!!

Guess not all bad, since I have not had time to fly, no crashes lol. But all up and working for time being.

[McKrackin]

damn Shake....My best wishes to your family.

[Dave]

What the.....I take it other than the arm she is OK.
Keep us posted Shakey.

Dave