Soldering doesn't hold

[eborn]

Hi,

I'm replacing the board of my P1.1.1 with a P2 board. All the ESC's and the G power cable are soldered fine. But the V cable won't hold. I think the initial solder joint (which snapped right off) heated some of the plastic around the gold connector. And now the gold connector is 'smudged' and won't hold any load. I've attached a picture. I tried cleaning the gold connector by heating it and wiping it off with a small brush. But that doesn't work. I can get some fresh tin on the connector, but when I heat it to join the cable, it just comes off...

Any help in cleaning this up? Or is the board fried?

 

[J Dot]

From the looks of it, looks like resin from the solder, lightly sand it with some sandpaper, or fingernail file ( cardboard one, not metal one ) shine it back up, also clean wire end, for a fresh new bond! ( NOTE: make sure your soldering iron tip is clean and shinny as well if not sand it as well ) Try this, as I had that problem once installing a 4mm patch antenna on my GPS MODULE!
Worked for me!

I put a dab of solder on my iron tip, then place a dab on the MC ( for Pos lead, tin the wire, now everything has solder on it, now place together touch iron too it, to mend! If you are leaving iron on joint for more than a second, something is not right, and you will OVER HEAT joint. Usually due do dirty tip on your iron! Hope this helps, keep us informed!

Take care, Fly safe!
Jerry D
( J Dot )

 

[grrquadman]

The solder in "the 'ole days" was 100% easier to use, (but it had to be replaced because it contained lead.)
At least that's what I heard.
I've built many a Heathkit, Allied Radio, etc. stuf and that solder was a pleasure to use.
Not so easy these days. (!)

 

[Pilot_FML]

Not being able to re-solder a connection is definitely no reason to junk the board.

I had trouble seeing detail on your attached picture so I found a picture of the board I think you're describing and have attached it to this post.

Describe exactly where on this picture you're having the problem... if you can add an arrow to picture showing the exact plug or connector that's a problem, it would make it much easier for me to try and help.

ier.

 

[J Dot]

I believe it is his main power lead to board from battery ( positive ) RED lead!

Here is a picture

Hope this helps
J Dot

 

[eborn]

Thanks for all the quick replies. It is indeed the spot at the arrow. The V cable to the battery. My board did not come with the tin blobs attached (my original upgrade board did, if I recall correctly). But that board already has a XT60 plug attached anyway.

 

[Pilot_FML]

Is what I see in the picture (with the arrow) the other side of the board that has the golden connector that you described in your first post?

I'm unsure of how what you call a golden connector has anything to do with getting a good solder connection.

Does the V cable connect to the board through this gold connector or is the V cable soldered directly to the board?

If its soldered directly to the board and its not holding now, I'm guessing that the solder pad that the v cable went through has been lifted off the board and is broken.

If its broken, find the break and just solder a thick gauge wire across the break to restore the circuit path.

Be careful not to accidentally "bridge" across any other circuit traces when you solder the wire on or you'll short circuit the board when power gets applied.

Also think about gluing the new soldered wire in place to prevent the new solder joints from breaking apart again when or if vibrations occur.

 

[eborn]

Is what I see in the picture (with the arrow) the other side of the board that has the golden connector that you described in your first post?

No, the same. The photo has blobs of solder on it. My board did not. Below the solder are the golden plates that the cables attach to.

Does the V cable connect to the board through this gold connector or is the V cable soldered directly to the board?

The gold plate is embedded in the board and the cable has to be soldered to it. Like this:

Also think about gluing the new soldered wire in place to prevent the new solder joints from breaking apart again when or if vibrations occur.

Definitely, thanks for the reminder!

 

[Pilot_FML]

Based on your above descriptions and the first picture you posted, I think I see how V cable was connected to the board.

The fact that the circuit traces from the gold plate are buried within the board makes using the jumper wire technique I mentioned earlier, a shot in the dark at best.

You're probably much better off trying to find some way to re-establish the original solder connection with a blob of solder to hold the wire. DJI's design was very poor to begin with because relying on a solder blob to make both a good electrical and a reasonably strong mechanical connection makes for a very brittle connection.

You got a bad problem at this point because everything depends on whether or not there's even still a good connection between the plate and the circuit it connects to.

Not only that but by adding more heat to plate when you attempt to re-solder greatly increases the chances of completely breaking the trace where the plate (if its not already broken) and the rest of circuit meet.

Before trying any re-soldering, see if you can find a schematic of this board. If you can, I might be able to give you a possible fix that just shunts the bad plate out of the circuit and replaces it with a simple pad that you could add wire(s) to duplicate this original part of the circuit. There a lot of if's involved but it might turn out to be a very simple fix.
..
P.S. I'm assuming that you can't see where the traces within the board go to when I say try to find a schematic. If you can actually see the circuit within the board (and can get a clear picture for me), you might not need the schematic.

Good luck....

 

[eborn]

I've sanded it lightly and the solder blob now does hold. But not for long. I think it's because there is quite some tension on the cable. So I'll go back to the beginning: remove the board, remove the cables from the internal power connector. Attach fresh cables, tin them, tin the board and try again. I'll do it all outside the shell, so I won't accidently touch it and prevent tension on the cables.
I've also ordered a 3rd hand tool and a fresh solder tip. That should to the trick. I'll report back when everything has come in by mail.

 

[Pilot_FML]

I've sanded it lightly and the solder blob now does hold. But not for long. I think it's because there is quite some tension on the cable. So I'll go back to the beginning: remove the board, remove the cables from the internal power connector. Attach fresh cables, tin them, tin the board and try again. I'll do it all outside the shell, so I won't accidently touch it and prevent tension on the cables.
I've also ordered a 3rd hand tool and a fresh solder tip. That should to the trick. I'll report back when everything has come in by mail.

Not sure I understand why you're removing (desoldering??) "all" ?? the other cables. If that's what you're doing, you run the risk of duplicating your problem at every cable connection.

If these cables are as stiff as you suggest, they must apply a lot of tension at the solder joint. You're playing with fire if you constantly remove and reattach these cables.

Why not instead just try and remove the tension from the cable where your poor solder connection exists?

One technique to do this, (if the the cable isn't to too stiff) is to bend it into a u shape, wire the u shape together to keep it from straightening out and then reattach the solder end of cable back onto the board into a "vertical" position. Anything you can do to keep the cable vertical near the solder joint takes tension off the solder joint.

Having said that, I don't feel that just relying on a solder joint that can only be attached to only part of the pad (plate) , will end up giving you a reliable connection. If the connection can be broken free just because of cable tension, I sure wouldn't trust the fix to something up in the air...

 

[eborn]

Not sure I understand why you're removing (desoldering??) "all" ?? the other cables. If that's what you're doing, you run the risk of duplicating your problem at every cable connection. If these cables are as stiff as you suggest, they must apply a lot of tension at the solder joint. You're playing with fire if you constantly remove and reattach these cables.

The VCC and ground are coming from the Phantom 2 internal power connector. I've used the two existing cables for attaching a XT60 plug and soldered two additional cables (16AWG) to the connector. Those are the two cables that I need to attach to the board. The VCC cable is rather short and that gives the tension. My idea is to remove that VCC cable and replace it by a longer one, with new tin. By lifting the board from the shell, I can solder the connection without the tension. My ESC's are already soldered, but I'll just lift them by putting some cardboard under it.

Having said that, I don't feel that just relying on a solder joint that can only be attached to only part of the pad (plate) , will end up giving you a reliable connection. If the connection can be broken free just because of cable tension, I sure wouldn't trust the fix to something up in the air...

Isn't that (in the end) how all Phantoms are flying? Since Phantom 1, all power connection from the battery to the board are made with those two solder joints. The only difference is that they are (most of the times) made in the factory. But you are right, I won't trust it without seeing a good joint. Hopefully I can get one by starting fresh. And by adding one or two CM of cable that will release the tension. That will allow me to make the kind of U shape you are referring to.

Btw, thanks for all the usefull advice and playing 'advocate of the devil'.

 

[syotr]

Are you sure that the copper pad has not come off of the board? It is difficult to tell from your photo. Sometimes these are attached with plated-through holes to a pad on the opposite side of the circuit board. If the pad has come off on this side, it may be possible to solder the wire to the opposite side of the board.

 

[eborn]

Are you sure that the copper pad has not come off of the board? It is difficult to tell from your photo. Sometimes these are attached with plated-through holes to a pad on the opposite side of the circuit board. If the pad has come off on this side, it may be possible to solder the wire to the opposite side of the board.

I don't think so, because after sanding it, I can still see the golden (copper?) pad that is also visible in the picture a few posts back. I've sanded until no more 'brownish' material came of.
I've unscrewed the motherboard, unscrewed the power connector, disconnected my cable and attached a fresh (longer) one.
I've also added a blob of solder to the V pad and increased the blob on the G pad. The cable there was attached, but barely. So I'll redo that tomorrow, when I have the new tools available.

(Btw, I've removed the small pieces of solder that are still visible on this picture.)

 

[J Dot]

A+
Final picture looks like you have it licked, looks 100% better than picture one! Keep us updated, as we are eager to see you airborne again! Keep up the great work!

J Dot

 

[Pilot_FML]

The VCC and ground are coming from the Phantom 2 internal power connector. I've used the two existing cables for attaching a XT60 plug and soldered two additional cables (16AWG) to the connector. Those are the two cables that I need to attach to the board. The VCC cable is rather short and that gives the tension. My idea is to remove that VCC cable and replace it by a longer one, with new tin. By lifting the board from the shell, I can solder the connection without the tension. My ESC's are already soldered, but I'll just lift them by putting some cardboard under it.

Must be me having a bad day but I'm still not sure what your doing will improve the reliability of any connection.

I still see your biggest problem as one of getting a good reliable solder connection on the pad where the cable barely holds.

Isn't that (in the end) how all Phantoms are flying? Since Phantom 1, all power connection from the battery to the board are made with those two solder joints. The only difference is that they are (most of the times) made in the factory. But you are right, I won't trust it without seeing a good joint. Hopefully I can get one by starting fresh. And by adding one or two CM of cable that will release the tension. That will allow me to make the kind of U shape you are referring to.

In the end (as you put it) that is how DJI has chosen to do it, but all their connections depend on having a full pad to solder to.... I'm not sure you have that luxury any more.

In any regard, best of luck ... hopefully your redesign gets your bird back up in the air.

 

[eborn]

Must be me having a bad day but I'm still not sure what your doing will improve the reliability of any connection.
I still see your biggest problem as one of getting a good reliable solder connection on the pad where the cable barely holds.

That's true. But I still think the pad itself is there and working. After sanding it, it did look intact the way I got it. But, like you said, the whole connection is fragile to begin with. I never put much thought into it, because my boards came pre-soldered. But thinking about it, there are far better ways to connect these (important) connections. If it holds after I put everyhing back (which is test one, because I have to but some tension on the cables), I will definitely put some hot glue on top of the connections to make them a bit more secure.

I'll let you know what happens!

 

[eborn]

After two attempts I now have a working connection for both VCC and Ground. And both connections feel strong, even without adding hot glue. I still want to add glue and fix the cables somehow. But for now, I can continue connecting and testing on the ground!

Thanks for all the help! In the end, the pad was still functional and did not come off the board. I still have a lot of testing to do, but for now, it seems normal.