What material are diode pins made from?

Discussion in 'General Electronics Chat' started by YoctoByte, Oct 27, 2015.

  1. YoctoByte

    Thread Starter New Member

    Oct 27, 2015
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    Hello,
    Today I noticed that normal diodes are not attracted by magnets. Almost all other components I have tested have iron pins (or nickel or something); LEDs, resistors, transistors, capacitors, except for diodes.
    I also noticed that the pins of several types of rectifiers (containing diodes) are also not made of iron. Zener diodes on the other hand do have iron pins.

    What is the reason the pins of diodes do not contain any magnetic material? And what material is it made from?
     
  2. alfacliff

    Well-Known Member

    Dec 13, 2013
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    rectifyers are designed to carry current, iron has a fairly high resistance., I have even seen some diodes with silver leads, silver conducts very well and solders well too. a lot are tinned copper.
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Usually tin plated copper, the gauge is usually slightly higher than comparable sized components due to the leads acting as heat sinks.
    Max.
     
  4. dl324

    Distinguished Member

    Mar 30, 2015
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    They started using silver when gold got expensive. I have some from the late 70's that I kept in semi-sealed containers and the silver has only tarnished slightly.
     
  5. YoctoByte

    Thread Starter New Member

    Oct 27, 2015
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    Thank you for your quick replies!
     
  6. ian field

    Distinguished Member

    Oct 27, 2012
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    Its farts that tarnish silver - hydrogen sulphide...............
     
  7. ian field

    Distinguished Member

    Oct 27, 2012
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    When I started out, a lot of IC manufacturers gold plated the pins.

    That fell out of favour because the gold migrated through the solder, I vaguely remember reading something about a microns-thick oxide layer under the gold plating. It was OK while the gold remained, but caused reliability issues years down the line.

    Although; AFAIK: gold plating is still very common on RF power devices.

    Solid gold pins would have been prohibitively expensive - and probably would've dissolved into the melted solder during assembly.
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
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    I did a quick check on some of the axial leaded rectifiers I have and all are tin plated copper.
    Which I sort of expected.
    Max.
     
  9. dl324

    Distinguished Member

    Mar 30, 2015
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    When I was an R&D Tech, I gold plated the boards for my prototypes when the designs were nearing finalization.
     
  10. recklessrog

    Member

    May 23, 2013
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    I can't remember why, but Rhodium was plated onto gold onto copper on some components used in the analogue engine control computers that went into the cold war secret development jets a company I worked for were designing.
    It may have been because of the elevated ppO2 that was in the pressurised environment.
     
  11. recklessrog

    Member

    May 23, 2013
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    On second thoughts, maybe it was the printed circuit boards that were Rhodium plated, may have been both though. It was a long time ago and my memory is not so clear.
     
  12. RichardO

    Well-Known Member

    May 4, 2013
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    I once worked on a project where the customer wanted Rhodium plating on edge connector fingers of a "paddle board". They thought the Rhodium would last longer than gold for repeated plugging and unplugging.

    After finding out that Rhodium plating was not a common process for PCB's, the decided that it was not that important. The price of stocking a plating tank was going to be $25,000 just to get started. This may have been a factor in their decision. ;)
     
  13. recklessrog

    Member

    May 23, 2013
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    That's very probably the reason why it was almost a capital punishment crime if a circuit board was damaged!!! Although of course, I don't think cost was a prime consideration in our case. I know the solder used had a very special composition, and if any was required for re-working, we were issued with a very small roll that was weighed before and after use and all work was meticulously logged.
     
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  14. mescab

    New Member

    Jul 17, 2015
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    Mainly silver, also using hydrogen sulphide.
     
  15. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Don't confuse the lead finish with lead material..
    Diode/resistor,etc.. "pins (leads)" are made from copper/copper alloys/dumet and are typically finished (plated) with tin, silver, or tin/lead plating..
    ROHS requirements have done away with lead now in lead plating.
     
  16. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    From memory, when 1N4xxx series first came out Mfg. claimed pure silver leads & the 1N4007's that I was using seemed to be so, 1972 ?, but in checking stock, 65 ea. 1n4XXX, all 1N4048's -iron, 1N4XXx, one silver, one iron, remainder Cu plated
     
  17. recklessrog

    Member

    May 23, 2013
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    Isn't the English language great! "I was LED by a LEAD, my feet felt as heavy as LEAD!
    Just to be really silly, say this out loud three times__One smart fellow, he felt smart!
    Why is "abbreviation" such a long word!!!
     
    Last edited: Oct 28, 2015
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