So what's the truth about lead-free solder ?

Come on! The 'Silly Rabbit' is nothing more than a nervous little Chihuahua on Cappuccino yapping his fool head off. His mother had the good sense to sell him to the circus for a quarter the day after he was hatched.

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Reply to
Michael A. Terrell
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I think I'll make up a tool for mechanically scraping this "tin-plating" off the next power tranny. My first idea is two back to back Skarsten scrapper blades to scrape back 2 sides at one time.

Reply to
N Cook

You might find that a tool is already available which works for this purpose. I'm thinking of the things for scraping the enamel off transformer winding wire:

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Chris

Reply to
Chris Jones

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What's the application that requires this refinishing ?

Graham

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Eeyore

controller

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Reply to
N Cook

But those are RoHS compliant.

More to the point, for removing laquer , not hard tin , from round surface. I just tried a Skarstan blade , singly, in its normal wooden handle and it scrapped the hard tin off some of the flat leads of the latest batch of TIP35C/36C power trannies that I bought. Down to the copper with no difficulty, I think I can ignore the tin-pest developinmg on the narrow edges as long as the main surface contact areas are functionally solderable.

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

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Reply to
N Cook

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This subject came back to bite me yet again today. There's a great part I wanted to use, but we'll have to refinish the pins first if I do, so I'll see if there's a different part I can use in this application. For the record, it's a high speed (not full speed) USB peripheral controller and the lead finish is 98/2 SnCu. I consulted with a few of the manufacturing people and one of the biggest problems with RoHS profiles is the solders aren't eutectic, so getting a proper bond is more difficult quite apart from the problem with tin whiskers.

Cheers

PeteS

Reply to
PeteS

Ok, it was just a thought. I was imagining the round pin of a T03 when I thought of that.

Do you mean tin pest or whiskers? I would have thought that the edges would be the worst place for whiskers to sprout from.

As for solderability, I would have thought that if the pins are exposed to a sufficient quantity of sufficiently hot SnPb solder for a sufficient time, then the tin would dissolve into the solder, like fine copper wire has an annoying tendency to do. If overheating of the semiconductor device is a risk, then perhaps it could be done in a couple of goes, allowing to cool in between. The resulting tin-rich solder could either be removed and replaced with fresh solder, or just diluted with more fresh solder.

I'm sure there would be plenty of people interested if you find a good technique for small-scale use.

Chris

Reply to
Chris Jones

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High temp mag wire... not the shitty for high temp uses "Nyleeze" does NOT burn off with the application of heat, and requires scraping to remove the insulation. Before Nyleeze, the requirement was the standard for decades.

Reply to
ChairmanOfTheBored

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With the sort of stuff I deal with, geometry-wise, tin whiskers have no relevance I would have thought. It is that film of tin , all lovely mirror shiney when new turning to grotty dusty grey (tin pest) , expanding in the process , and physically pushing the solder away from any conduction maybe only 2 years down the road. I am not sure just heating legs with solder would affect the integrity of that initial tin film without some sort of mechanical intrusion while hot and mixing.

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

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Reply to
N Cook

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