Soldering: a technical question

If it is an up to date machine, then it will be manufactured using the dreadful new-fangled save-the-planet brigade's lead-free solder. In order to repair it with any hope of long term chemical stability of any reworked joints, you will need to be using using lead-free solder to rework them, and in order to do this, your iron will need to be around 30 deg C hotter than it needs to be for standard leaded solder. If you look carefully at the board with a strong magnifier, you will likely see that every joint has a dull grey dry ( american " cold " )look to it. Welcome to the world of lead-free ...

Just as a matter of interest, what is the machine, what is the problem that you are trying to fix, and what soldering equipment are you trying to use for the job ?

Arfa

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Are things going to get that bad? I've not met this new health & safety junk yet, eg at the moment repairing a

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Thank you very much for this reply! I knew something was up because I've been soldering for a long time but never seen this. The unit is a Samsung, very fancy DVD player. Sometimes it freezes so I decided to give the main board a look. I did find what appeared to be, like you said, cold solder joints. I guess that's not "cold" after all. Is this lead free solder sold anywhere ?

moonlite

Where are you? - Maplin sell it in the UK, its actually becoming hard to find lead/tin solder!

I niaively thought that if I should come across such a pcb with this lead-free stuff and a cold joint then all I'd have to do was remake the joint by adding traditional solder into the mix. But I take it now that they are incompatible, which presumably means that even solder sucking away all the original from component lead lead and pad would still leave contaminated surfaces that still would not take traditional solder for a more durable joint - opinions/knowledge anyone ?

Most of the monitors I used to repair had been assembled with lead free for a couple of decades - this was by far the most common cause of failure!!!

As of yet I have never bought any lead free solder and the only problem I've had is if the lead free isn't sufficiently diluted with lead/tin, it remains "stringy" and causes solder bridges! Use plenty of flux but be mindful of the measures needed to clean it off after!!!

I wouldn't be surprised if they are using metallic glue (cold) for electrical connections.

"moonlite" wrote in message news: snipped-for-privacy@h48g2000cwc.googlegroups.com...

Well, it's sold everywhere here now, and regular leaded solder is becoming more difficult to obtain, but I'm assuming that you are on the US side of the Atlantic ?? The Americans, as I understand it, have not been so keen to adopt this lead-free technology as the far east and Europe have. It's now law here under a directive called RoHS ( Restriction of Hazardous Substances ). The US military, for instance, flatly refuse to use it on reliability grounds. Over here, the avionics and medical instrument industries have been granted exemptions, and decisions on many others are pending. Never-the-less, the far east have been manufacturing in this technology for about 3 years or so now, so I would guess that most if not all of the US imports of these products from the far east locations, are built with lead-free. This being the case, I would expect that lead-free solder would be readily available. Indeed, Sony for instance, have insisted that their official dealers over here, use ONLY lead-free to repair ALL of their products, for the last 2 years, irrespective of whether they were originally built in leaded or lead-free. As you can imagine, this has gone down like a lead ( Ha ! ) balloon in service departments ... The solder industry itself seems unable to make up its mind as to whether mixing leaded and unleaded solder causes a long term problem. Half say you shouldn't, half say no problem. I recently wrote an article for a magazine on this very subject, and took some expert advice on this point, and his reckoning was don't mix if you don't want a long-term unstable joint.

Anyway, on your Sammy problem. It is rare for a genuine electronic fault to be responsible for any kind of freezing. Commonly, it is caused by either a defective / worn laser, or a mechanical issue with the laser sled transport. As a first move, ensure that the laser moves silky smooth the whole way from one end of its slides to the other. I had a Sammy last week that had a tendency to freeze up about 30 - 40 minutes into a disc. The cause was distortion of the plastic runner that one side of the laser ran on. You could feel the laser get tight as you moved it towards the back of the deck. This was cured by slight rubbing down of the plastic with very fine carb paper, followed by metal polish. You can also get poor sled movement as a result of the pinion on the sled motor splitting. If you move the laser by hand, you get a bump-bump-bump as the pinion rotates past the split.

Sad to say though that the majority of freezing problems are down to the laser itself. If the laser is iffy, it will have a lot more trouble reading home-burns than commercial pressings, and will tend to freeze on them more readily. Conversely, an audio CD will normally play faultlessly. Not an absolutely definative test for laser condition, but usually a good indicator.

Arfa

Arfa, I can't thank you enough for this info and for taking the time to explain this lead-free issue. I am sure the readers of this post also appreciate your effort!

Arfa, I can't thank you enough for this info and for taking the time to explain this lead-free issue. I am sure the readers of this post also appreciate your effort!

I've never had any problems working with lead free boards. The solder is a little harder to remove, but it should take regular Sn/Pb solder fine. I don't know what the long term reliability will be, but everything looks fine and I haven't seen any problems yet.

It sounds like your soldering iron just isn't powerful enough. Multi layer boards with lead free solder will require a much more powerful soldering iron than you can get away with on a single sided board. I highly recommend a 40W or greater temperature controlled soldering station for working on any modern electronics.

Andy Cuffe

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