Desoldering a tricky DC jack

Question

I'm trying to replace a faulty DC power jack on a laptop, and having quite a difficult time with it. At this point, I'm not sure if the problem is with my equipment, or my technique.

Equipment:

• Weller 50w temp controlled iron (max temp: 850f, ETA tip)
• Dremel gas powered iron / hot air gun (this thing)

There are six pads on the underside of the board I need to desolder to remove the old jack. The four on the outside, far as I can tell, only provide mechanical support rather than electrical connectivity.

This is what the board looks like from the top:

And the bottom:

(It's a bit of a mess due to my previous attempts. The black/brown crap is just flux, not char on the board)

It took a lot of messing around to get it out as far as it currently is.

The main problem is that removing the existing solder is proving to be nigh impossible - I've got both some desoldering wick, and a solder sucker.

• The sucker has proven all but useless, the moment I move the iron out of the way to get the sucker in place, the solder has already rehardened.

• The wick kinda works, but it seems to take a very long time to get very little solder absorbed. As in, you can see the faintest hint of silver color in the copper wick.

My technique was to set my iron to max temp (850f), let it get up to temperature (verified on the digital display), add some flux, hold the wick in place on top of the pad and press the tip of the iron into it.

My understanding is that this high temperature is required due to factory solder being trickier to deal with than the stuff you buy on a spool, and also likely to be the lead free kind, which requires a higher melting temperature.

Now the other option I have is the torch/hot air gun, but I don't want to mess around with it too much for fear of scorching the board. Hence why I'm here, asking someone who's hopefully an expert.

How do I tell when my work area is getting too hot? Given what I've described here, am I doing anything obviously wrong? Am I missing some crucial piece of equipment to make this job easier?

Answer 1

The jack is faulty, so...

Cut all the plastic away with side cutters, leaving just the metal terminals. Now you can remove each terminal separately.

Hold the circuit board vertically in a vise. Get your iron hot as usual, and apply more solder to the pad to improve heat transfer. Grab a terminal (on its edge to reduce heat transfer) with your pliers, then heat the pad with your iron. The solder should melt quickly, then you simply pull the terminal out of the board.

Finally, use a solder sucker and/or desoldering braid to remove excess solder from the hole.

Answer 2

The pump is your friend. Incorrect technique with the pump is your problem:

The sucker has proven all but useless, the moment I move the iron out of the way to get the sucker in place, the solder has already rehardened.

Of course, you must apply the pump while the solder is still molten. Keep heating the solder with the tip of the iron, then bring in the pump, quickly press the button, and remove both tools.

Be sure to remove solder from the pump every couple of uses.

Solder pump tips are made to withstand some heat. You can do this without jamming the pump tip into the soldering iron tip: basically, just approach the tools to the solder blob from different angles. The pump creates a small area of vacuum around its tip; it doesn't have to be in contact with the solder blob when you trigger it.

Apply the suckage to each joint multiple times. Wicking is not going to be of much use here, because wick will not remove stubborn solder from the inside of a plated through-hole. Wicking is more useful for cleaning up solder pads when a part is removed, or fixing accidental solder bridges between closely spaced pins or traces.

If the pump has done all it can and the part is still stuck, there are ways to loosen it with the equipment you have. You can heat the pins on one side of the jack together at the same time while applying pressure to get them to move a little bit. (Or while pulling on the part from the component side.) Then do the same on the opposite side and repeat. By alternating this way, little by little, you will get the part out.

Answer 3

Well, repair of consumer electronics is off-topic, but the general problem is that there are a LOT of copper planes (including inside ones) in the area of the power jack of pretty much any computer, and they act as a very effective heat-sink.

You need to pre-heat the whole board, (in an oven) then heat the area you are trying to remove the jack from further. In most cases "removing the solder" is fruitless (you won't get it out where it counts, inside the board), you may well do better to add some solder to get better heat conduction - and then yank the jack out as fast as you can. Worry about removing solder after the thing is out, so you can get the new one in.

While a common enough problem, it's not that simple of a repair - it's not uncommon to damage the board in removing the jack. If the thing was well designed it wouldn't need replacing, so you know ahead of time that there are issues there.

Answer 4

Do you have a hot air paint stripper?

Set it for about 250C, maybe a little more, and point it at the solder side of the board. Direct the airflow to cover the connector and immediate surroundings and little else (the tool comes with clipon air deflectors which may help).

When you see solder starting to melt across the affected area, pull the connector straight upward (not with fingers!)

This is not a technique to use in every circumstance. If the jack is definitively broken then cutting it up and removing individual pins has lower risk of collateral damage.

But if there was a need to preserve the connector - e.g. for post mortem analysis, it's worth having in the armoury.

It does carry some risk - e.g. the temperatures need to be calibrated, e.g. with a thermocouple, and practice on a strap board is recommended. Too much temperature and airflow risks blowing 0402's all over the place. In such cases, makeshift windshields of Kapton tape and cardboard may be necessary.

Answer 5

Forgive I just joined. I would remove the jack using any tool that will not harm the board. Once the jack is removed use your soldeering iron and sucker to clean up the connections you need for the new jack. Observe carefully that you have not created solder short circuits. Also consider not installing a jack at all but connecting short wires to an external jack to be used external to the circuit board.

Good luck Stephen

Answer 6

Feed your solder wire onto one side, and the middle pin so that you have a puddle (That connects all 2 or 3 on one side, the whole puddle spreads over those pins.) Then bend this side up away from the board on the other side of the connector, hold this position until the puddle cools. There will be some torque on the board from the connector but probably not enough to break anything. At this point you have 2 pins to go, so repeat on the other side. Use plenty of flux. Once completed use braided wire to clean the solder off the board and some isopropyl alcohol to clean off the flux. I would normally use a heat gun in tandem with a soldering iron to remove a connector like the one shown but you might be able to get by without it. I would recommend a jig to hold the board, allowing one hand to apply the iron tip to one side of the board, and the other hand free to shimmy the connector off (you could use a razor blade in between the board and connector, twist it slightly to apply pressure.) Let the heat do the work, if you're struggling too hard then you're doing it wrong.

A word of caution, a hot solder puddle (much less any liquid metal at this temperature) is extremely dangerous and one small mistake with something of this nature has the capacity to impact the rest of your life. If this seems to be giving you too much trouble or you feel a bit awkward just skip it and find a better solution.