Soldering iron problems

Hi,

I know this should be simple but isn't. I need to resolder a DC power connector on a laptop, due to dry joints.

I can't find my old, rarely used soldering iron, so I went to Maplin and bought their cheapo 30W soldering iron.

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I would have thought that is good enough for PCB soldering, but I can barely get the old solder on the board to melt, let alone re-solder the joint. I can't work like this, I'm going to arse about for hours and still not get it done properly. Is the problem likely to be the fine point nib that it came with? I have always used flat-tip bits in the past. Or is the Maplin iron crap, and should I have bought the Antek 30W instead -

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All advice appreciated.

I should mention that I also tried my 100W soldering gun, like this one:

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No luck here, but then I have always hated this tool and never been able to use it effectively. It's rated for 12 seconds use in a minute (don't know what happens if you go above that), but takes about 9 seconds to even get hot enough to melt solder. Are these crap, or am I not using the thing properly?

Antony

Reply to
Antony Gelberg
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Yep.

It is lead free, but that doesn't matter when I'm trying to desolder the OEM joint. I think it's just not hot enough but I'm surprised - I thought 30W would be plenty.

Reply to
Antony Gelberg

Do some practicing with other things first. A few things:

- As someone pointed out, you may have lead-free solder, which has a higher melting point. But you should use it for the repair, since the connector probably has the same stuff already on it.

- There may be an invisible coating on the soldering iron tip, or it may not be properly tinned. The last couple of mm of the tip should have a coating of melted solder, applied by you.

- Some coaxial connectors have a nickel (?) coating that is hard to solder. Using fine sandpaper on them really helps, as does a rotary wire brush.

Your soldering iron looks fine (low-end, of course). Is the tip tightly attached? Try loosening and retightening the screw while it is hot (use care).

Reply to
mc

Make sure the tip is tight. Make sure you're using the correct solder?, 60 tin and 40 lead for repair work. Use some extra solder paste to clean the area.. It's possible you have Lead Free Solder, that's hard to work with..

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Reply to
Jamie

I'm just trying to desolder the existing joints at the moment.

It does.

But would this stop me desoldering existing joints?

It's back in the packaging. :) Don't think swapping it for a 50W iron is a better idea? How about a flat tip instead of fine point?

Reply to
Antony Gelberg

Mass is more important that wattage.

BH

Reply to
BH

If the laptop was manufactured fairly recently, it will have been constructed with lead-free solder - dull grey looking joints, and the board may have "Pb Free" or "PbF" either etched or silk screened on it. If it is lead-free, then there is your first problem, as the melting point is higher than solder that you are used to. The second problem is that you are attempting to solder a fairly large component, that will leech heat out of an iron very quickly, which brings us to the next point that the iron used must have good thermal inertia to overcome this effect, and a pointy tip is far from ideal to achieve this. Also, 30 watts may be a bit on the low side, particularly if it is lead-free solder. On the other hand, I would have said that the job *could* be done with that iron, by a person used to soldering daily. Remember for a start that old solder - even leaded - is much more difficult to melt than new, and it is usual to feed some new solder into an old joint, before sucking or wicking the joint clean.

As far as your Weller gun goes, this should easily be able to cope. I still have my original one of these with a black bakelite casing, from when they first came out over 40 years ago, and it still works as good as new. Yours should certainly not take 9 seconds to get hot. 3 seconds tops. The problem is that you are not slackening and re-tightning the bit-wire retainer nuts. These irons work by the bit being a short circuit across a single turn transformer secondary, the primary being a coil connected directly across the mains. The single turn produces a low voltage, but with huge amounts of amps flowing round it, via the copper bit-wire, which then gets very hot as a result. However, the surface of this (soft) copper wire oxidises from the heat, and the resistance of the contact points, under the retainer nuts, goes up. It only needs to go up by a few tens of milliohms, to significantly reduce the current flowing round the shorted turn, and hence the amount of heat being generated in the bit.

Click the iron's trigger on, and whilst holding it on, take your bit retainer nut spanner, and back each nut off a half turn, and re-tighten, one at a time. That should then give you virtually 'instant' heat each time you trigger it on, for the rest of the soldering session. You should repeat this procedure whenever you get the iron out to use. As far as exceeding the duty cycle of the gun, I have done this many many times. The effect is that the case becomes uncomfortably hot to hold, as a result of the transformer primary winding overheating. I suppose that if you managed to hold onto it for long enough, the insulation on the wire making the winding would fail, but I think that you would be seriously burning your hand by the time this happened, and already, your nose would be telling you to stop ...

Arfa

Reply to
Arfa Daily

My desoldering tool can do up to 60 watts/. I would get something in the line of 45 watts or so for desoldering Lead Free or, mix in some Leaded solder to soften it.

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Reply to
Jamie

Mass of the tip, correct?

Reply to
Antony Gelberg

Greetings.

I hope this message finds you well.

This may sound like a dumb question, but have you tinned the tip of your soldering iron?

-W Gray

Reply to
W Gray

Hello:

The why's of your problem have been explained by other posters. You can solder your dc jack with your 30 watt or the pistol, better yet, get a friend and use both, however, there is a trick to it: you have to preheat the pcb.

To do so, get a hair drier, set it on max and slowly start heating a large area of the board from a distance of 20cms (8inch), then start aproaching and concentrating on the jack, it takes about 5 minutes to do it properly, your board will be very warm overall, then heat the board directly above and bellow the jack with the hairdrier nearly touching them, do this for about 3 seconds each side, repeat about 4 or 5 times, then and only then use the solder iron to remove the jack, if you have a friend you can use both irons, the pistol on the ground connection the other on the other pins. the jack should fall off. be very gentle with the pistol if you use it, because the board is allready hot, such beast will easily damage it if you aproach it like you did when it was cold.

P.S: to use the pistol *first* heat it enough to melt solder *then* touch the parts then turn on-off-on-off at about 1Hz.

Best regards

Steve Sousa

Reply to
Steve Sousa

The soldering iron has to have the right temperature, and have enough BTU's to heat the connection. Make sure you are using 60-40 type solder.

A proper soldering station is what is normaly used. This will allow for proper temperature control, and can put out enough BTU's of heat.

If you do not have a lot of experience at soldering on to circuit boards, it is very easy to damage the solder pads and traces on the board. This is especialy true with multi-layer boards. This type of damage takes a lot of experience to fix, it is not easily repairable. Not having the proper tools and experience can usually lead to damaging the circuit board, and sometimes the components that are being heated.

Jerry G. ======

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Reply to
Jerry G.

Ah. They may have a clear plastic coating.

30W is plenty for electronics; 15W would do.
Reply to
mc

Hi Smitty

I was taking that as a 'given' by assuming that the OP was using conventional flux-cored solder for his attempts, so flux would be automatically put into the equation when new solder was added to the old to help the melting process. However, if he's not, you're dead right, and I should probably have made that clearer as being part of the reason for adding new solder to the old joint ;-)

Arfa

Reply to
Arfa Daily

Antony,

If you can borrow a temperature controlled iron, preferably one in the

45-50watt region, with a fairly broad tip, you should be able to do the job fairly easily.

What is happening is the large area of the multilayer PCB, combined with the rather large track area, is siphoning away the heat from the tip and chilling it. The iron is not temperature controlled so cannot compensate, so its temperature drops below the required heat to melt solder.

If you keep trying with your iron, you will soon destroy the socket, board and PCB pads- the job must be done quickly with a hot iron. I have replaced several laptop power connectors and feel that a cheap hobbyist's iron in the majority of cases would be quite inadequate.

Try eBay- I've seen old Weller magnastat soldering stations for about 15 UKP. Usually tatty to look at but they do a great job. I still use one myself! The temperature is set by tip selection, and there's not much they can't do with a hot tip fitted. Alternatively there's occasionally Antex stations with user-variable temperature dials which go for a reasonable amount. If you intend on servicing your own stuff you really need a temperature controlled iron.

Soldering guns are OK for the appropriate job but not really for PCB use because they can only administer very high heat for short bursts and need cooling off time before they can be operated again.

To answer your question- exceeding the time will burn out the transformer inside! The one I once used went off with quite a loud pop!

Morse

Reply to
Morse

I agree. When I said earlier that 30 watts is plenty, I hadn't quite realized he was wanting to remove something with a substantial amount of metal that needs heating up.

Reply to
mc

I've had success doing what you want to by using the largest iorn I can find and working really fast so that you don't destroy the board. I'd immagine a

45 - 50 Watt iorn would work well. Just don't leave the iorn on the board more than a few seconds, just long enough to liquify the solder and add some more. You will cook those solder pads if you use too small of an iorn or take too long with a big one!

Mike

Reply to
Michael Kennedy

After working with the Weller rework station, all the other irons seem way to large for the hand. The Weller being smaller in size is not small on watts. 80 watts. Pleasure to work with.When I need big watts, i get out the 250 watt Radio Shack gun.

greg

Reply to
GregS

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Is what we used on every bench that did any soldering at Microdyne. I had three, with different tips. They are 70 watt, with adjustable, built in temperature regulation.

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Reply to
Michael A. Terrell

Those thermostaic irons were banned from production work, around anything that's ESD sensitive.

Another tool not allowed in a ESD sensitive setting.

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Reply to
Michael A. Terrell

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