High temperature soldering

Discussion in 'General Electronics Chat' started by Regected, Jul 15, 2010.

  1. Regected

    Thread Starter Active Member

    May 24, 2009
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    I'm a decent novice solderer, but I'm in a bit of a pickle. I have a project that has an operating temperature around 150C(300F), but I can't find any information about how to properly solder something to withstand such a high temp. Has anyone done this, and if so, can you give me any pointers?
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Do you mean the local ambient/environment is 150C? Good luck as you are exceeding the operating temperatures of most/probably all IC's.
    If this is a heater/nichrome element or something many times this is done with a mechanical crimp or brazing (very similar to soldering)
     
  4. Ghar

    Active Member

    Mar 8, 2010
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    Most transistors specify a maximum junction temperature (which is always higher than ambient) of around 150C ... military grade parts are only rated to operate at 125C.
     
  5. Regected

    Thread Starter Active Member

    May 24, 2009
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    Thank you for the helpful info.

    Many men with much more education than me have designed this device. It's a metering tool for down-hole oil well drilling. They have sourced all the parts required for the operating temperature and pressure. They have hired me as a soldering technician since they are just starting to enter the phase of an engineering prototype, and it's more cost effective for them to hire a technician than ordering the boards populated.

    I know I can do the soldering; I'm just worried that I don't know enough of this high of temp.
     
  6. BillB3857

    Senior Member

    Feb 28, 2009
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    The company I work for had a situation of connecting a 24 conductor cable to an Amphenol connector that was used in an industrial application where the environment potentially reached 450F. Our solution was to make the connections with 5% tin/ 95% lead solder. It was a bear making the connections, but so far, to our knowledge, none have failed.

    The following is from this site: http://www.logwell.com/tech/servtips/solder.html

    Traditional High Temperature Soldering
    Downhole electronics must frequently be able to withstand temperatures in excess of 150°C (~300°F). To keep the solder from melting and components from literally falling off circuit boards, high temperature alloy solders are necessary. The bad old high melting point (HMP) solders were composed of 5% tin / 95% lead (Sn05Pb95) with a melting range of 301-314°C (574-597°F) or 10% tin / 90% lead (Sn10Pb90) with a melting range of 268-302°C (514-576°F). A better HMP solder is now commonly used for high temperature downhole applications, an alloy of 5% tin / 93.5% lead / 1.5% silver (Sn05Pb93.5Ag1.5) with a melting range of 296-301°C (565-574°F). The eutectic alloy of tin, lead, and silver is 5% tin / 92.5% lead / 2.5% silver (Sn05Pb92.5Ag2.5) with a melting point of 280°C (536°F), a very high melting point for a eutectic solder.
     
  7. newbies_hobbyist

    Member

    Jun 4, 2010
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    Regected,

    With the use of RA (rosin activated) flux it will make your high temperature soldering become easy but make sure you clean it thoroughly do not leave any flux residue as the RA flux type is corrosive and conductive when it is heated. Take into consideration also the use of multicore soldering lead with SN05Pb93.5Ag1.5. The right size of soldering tip, time and temperature setting are also a big factor for better or perfect soldering.
     
  8. retched

    AAC Fanatic!

    Dec 5, 2009
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    Test. Test. Test.

    I have used 5/95 for a few high temp jobs, and it is a pain in the tukus to work with, dont breath the fumes....AT ALL...

    The high lead contend lends to a nice strong, flexible joint, that can handle some abuse.

    We were measuring fast moving, high temperature air, and good 'ol everyday solder just didnt hold up.

    We would find our thermocouple sensor about 100ft away before the test was done.

    After the switch to 5/95, it held fine.

    This was 400mph air currents at 400+ deg F (to about 530 deg f)

    It worked..(but tasted bad) ;)
     
  9. newbies_hobbyist

    Member

    Jun 4, 2010
    67
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  10. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
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    I was simply stating what my experience has shown.

    Brittle when cold and brittle when hot are two, WAY different things.

    The HMP will HOLD its shape longer when hotter than LMP.

    Tensile strength at room temperature and tensile strength at 500deg F is two completely diffrent sports. ;)
     
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