Why is some solder harder to melt?

Discussion in 'General Electronics Chat' started by Gdrumm, Dec 23, 2014.

  1. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    I've been working on a drill recently, and I can't desolder the diode mounted in the trigger.

    My everyday solder melts easily with my iron, but this stuff is practically welded.
    I even tried my big gun (100 watt I think), and it wouldn't budge.

    Braising has a different color I think, but this stuff looks like solder, but it doesn't melt.

    Would that be a requirement for a 600 volt diode, because of the heat generated?
    It's mounted near plastic (so I don't think it's a heat issue)

    The trigger is in a 19.2 volts cordless hammer drill.

    Any insights welcome.
     
  2. #12

    Expert

    Nov 30, 2010
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    Silver solder looks just like lead solder when I do the job. Try to damage the surface with a sewing needle. If that doesn't work, it's not lead solder. If that does work, it's attached to something that is wicking the heat away from the soldering iron.
     
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  3. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    There are different alloys to solders, they're usually a mix of Selenium, Silver, Bismuth and Lead. Lead solder is becoming quite unpopular, although I think it'll be impossible to get rid of. Normally solder has a core of rosin and flux to make it easier to apply. As a rule of thumb, solders that have silver in them melt at a higher temperature, and the higher the lead content, the lower the melting temperature... It's quite possible that the solder in your drill has a high silver content, if it is not indeed welded. You might like to explore this list to learn more.
     
  4. Brevor

    Active Member

    Apr 9, 2011
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    On many battery operated power tools the components are spot welded to the terminals.
     
  5. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    I'm pretty sure I would recognize a spot weld, and this isn't one.
    It has a peak, like solder, but shiny.

    Question, can I remove the broken diode with dikes, then drill small holes in what remains, then solder in a replacement diode?

    In other words, will it work okay with my regular everyday electrical solder?

    Thanks for the link, and input.

    Happy New Year, I appreciate you guys.
    Gary
     
  6. ian field

    Distinguished Member

    Oct 27, 2012
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    You could try diluting it with lead based solder to create a lower MP alloy.

    Years ago you could get very low MP solder - but it contained cadmium which is very toxic.
     
  7. #12

    Expert

    Nov 30, 2010
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    What are your choices? Replace the part or call in a team of engineers to speculate about it. I suggest the first answer.

    Will it last? Try it and find out. One experimental result is worth a hundred educated guesses.
     
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  8. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    Yes, you certainly could... the original weld is a sturdy one most likely to resist fatigue resulting from vibration... with that in mind, you could solder and use another method to help it make a more robust union...
    Good thing is... this ain't no aircraft you're tweaking here... you can afford yourself the luxury of experiment and possible failure
     
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  9. takao21203

    Distinguished Member

    Apr 28, 2012
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    how about a picture
     
  10. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    DSC00136.JPG DSC00137.JPG
    Makes sense about the vibration issue.
    Here are two pictures of the switch.
    The old broken diode has been cut out with dikes.
    I expect the replacement diode to be here in a few days
    I will post back with results.

    Thanks for the feedback.
     
    Last edited: Dec 30, 2014
  11. takao21203

    Distinguished Member

    Apr 28, 2012
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    its a phone picture? Highly guess so.

    With my SONY digital camera I can make really crisp pictures. Often still way off reality, but more close to it.

    But I think I know that kind. Its hard soldered with high temperature. Did you wet the surroundings with tin?

    You could try to sandpaper or file it, maybe its brass or copper. Maybe its mixed with some other metals, most copper, but no longer solderable with tin/lead low temp solder.
     
  12. takao21203

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    and the right one rather looks like spot welded isnt there are small grove?
     
  13. takao21203

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    Apr 28, 2012
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    i had success sometimes when filing surfaces. but it also can occur the joint will be too brittle.

    For instance you can solder steel cans easily they're even tin coated as far as I know.
    Even if not- all sort of cans made from thin sheet metal (steel) can be soldered easily,
    if not, filing or sandpaper helps
     
  14. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    Sorry, the first picture posted should have been a thumbnail.
    Anyway, the pictures were taken with a Sony Handycam.

    Good suggestions about sanding or filing.
    I don't have any tin that I know of, and wouldn't know how to apply it to "wet the surroundings".

    I'll experiment a little further, since I have a few days before the part arrives.

    Thanks
     
  15. takao21203

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    Apr 28, 2012
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    its "jargon" for covering a metal surface with a solder film, which has a true intermetallic bond.

    Of course there are tins, and there's tin but thats that.

    I still only see small resolution pictures.
     
  16. takao21203

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    Apr 28, 2012
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    "crisp" means the focus is right, I often have to try repeatedly until I get it right.

    It helps to use flash as the shutter time is much smaller, no "jerking". If you dont use flash, the algorithm will try to correct the "jerking" but results are mostly average.

    Take a still with flash in the 2nd highest resolution- the highest also usually is slower to store the data.

    I went through a few digital cameras...
     
  17. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    Just Curious?
    Today, it's about 40 degrees ferinheight, and I am in the garage with my heater on, so the thermometer says it's 58 degrees in here.

    What kind of effect does that have?
    My iron won't even melt everyday solder right now.

    What's ideal for soldering conditions, temp, humidity, etc.?

    Guess I'll try it tomorrow at midday, or take it in the house while the wife is off getting her hair done.
     
  18. takao21203

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    Apr 28, 2012
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    after really looking at it, i'd say the blob is a hard soldered joint, and the connection on the right side is welded.
     
  19. takao21203

    Distinguished Member

    Apr 28, 2012
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    doesnt have any effect. scratching with a blade or screwdriver also helps if you dont have a file or sandpaper. but it might just be not solderable at all, certainly you cant loosen the connection with a soldering iron.

    I'm not an expert but I saw these kind of connections before. Its more suitable for automatic processing, thats one of the reasons why these use it (I think).
     
  20. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    Here are two more pics, with white background and better lighting.
    See how he wires look where atto the motor?
    All of the soldered joints had that appearance.
    DSC00138.JPG DSC00139.JPG

    It's still too blurry, sorry about that.

    Thanks again for all the input.
    Gary
     
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