Ampacity Q from newb...

Discussion in 'General Electronics Chat' started by 84_Carrera, Feb 3, 2009.

  1. 84_Carrera

    Thread Starter New Member

    Feb 3, 2009
    Hello all. I have to come up with a recommended maximum current carrying capacity for electrical leads in a microelectronic enclosure situation. The company I work for as an IT guy does the TO- & other / custom electronic enclosures for our customers to then populate - we make glass- & ceramic-to-metal seals in metal packages.

    One of technical datasheets they had me come up with years ago needs updating, as we've been told by some of our customers that our data's extremely conservative.

    Anyway, we traditionally deal with .018", .020", .025", .030", .040", .050", .060", .080", & .090" diameter leads, that are usually shorter than 1" long (some as long as 2", but VERY rare). Application can be open air, altitude to 80,000 feet, space applications, etc. Lead materials can be copper / glidcop, Kovar (iron-nickel-cobalt alloy / ASTM F-15), Alloy 52 (iron-nickel ASTM F-30), or a Cu core through an Alloy 52 wire (3:1 52 Alloy to Cu). NO insulation. Inside of packages can be nitrogen or other inert gas filled, population of the inside of the package can be anything - we won't know how crammed the package is. Our packs are open-cavity from say, .415" sq. x .150" high through 10"L x 3" wide x 1" high we'll say. The actual feedthru lead is the same regardless. Diameter of the glass or ceramic seal will vary. Temp rise can be significant, package materials can be braze / solder that reflows at lower temps, so we're looking at a maximum of 200° C package / environment temps.

    We're obviously not talking about running cable through household walls here.

    I've been looking at Fourier / Neher-McGrath, but I don't have enough info to really work with this, given my (pitiful) background.

    This is the old data I have (oops! Table didn't copy & paste...):

    [SIZE=-1]Material /

    [SIZE=-1]Pin Diameter [/SIZE][SIZE=-1](Inches)[/SIZE] / [SIZE=-1]Pin Diameter [/SIZE][SIZE=-1](Millimeters)[/SIZE] / [SIZE=-1]Max. Recommended Current (Amps)[/SIZE]

    [SIZE=-1]Kovar ASTM F-15 Alloy[/SIZE]
    [SIZE=-1].020 / [/SIZE][SIZE=-1]0.51 / 1/0A[/SIZE]
    [SIZE=-1].030 / [/SIZE][SIZE=-1]0.76 / [/SIZE][SIZE=-1]3.0A[/SIZE]
    [SIZE=-1].040 / [/SIZE][SIZE=-1]1.02 / [/SIZE][SIZE=-1]5.0A[/SIZE]
    [SIZE=-1].050 / [/SIZE][SIZE=-1]1.27 / [/SIZE][SIZE=-1]7.5A[/SIZE]
    [SIZE=-1].060 / [/SIZE][SIZE=-1]1.52 / [/SIZE][SIZE=-1]10.0A[/SIZE]
    [SIZE=-1].080 / [/SIZE][SIZE=-1]2.03 / [/SIZE][SIZE=-1]15.0A[/SIZE]
    [SIZE=-1].090 / [/SIZE][SIZE=-1]2.29 / [/SIZE][SIZE=-1]18.0A[/SIZE]

    [SIZE=-1]52 Alloy ASTM F-30 Alloy[/SIZE]
    [SIZE=-1].020 / [/SIZE][SIZE=-1]0.51 / [/SIZE][SIZE=-1]1.0A[/SIZE]
    [SIZE=-1].030 / [/SIZE][SIZE=-1]0.76 / [/SIZE][SIZE=-1]3.3A[/SIZE]
    [SIZE=-1].040 / [/SIZE][SIZE=-1]1.02 / [/SIZE][SIZE=-1]5.5A[/SIZE]
    [SIZE=-1].050 / [/SIZE][SIZE=-1]1.27 / [/SIZE][SIZE=-1]8.0A[/SIZE]
    [SIZE=-1].060 / [/SIZE][SIZE=-1]1.52 / [/SIZE][SIZE=-1]11.0A[/SIZE]
    [SIZE=-1].080 / [/SIZE][SIZE=-1]2.03 / [/SIZE][SIZE=-1]17.5A[/SIZE]
    [SIZE=-1].090 / [/SIZE][SIZE=-1]2.29 / [/SIZE][SIZE=-1]20.0A[/SIZE]

    [SIZE=-1]52 Alloy, Cu Core[/SIZE]
    [SIZE=-1].020 / [/SIZE][SIZE=-1]0.51 / [/SIZE][SIZE=-1]3.0A[/SIZE]
    [SIZE=-1].030 / [/SIZE][SIZE=-1]0.76 / [/SIZE][SIZE=-1]9.0A[/SIZE]
    [SIZE=-1].040 / [/SIZE][SIZE=-1]1.02 / [/SIZE][SIZE=-1]15.0A[/SIZE]
    [SIZE=-1].050 / [/SIZE][SIZE=-1]1.27 / [/SIZE][SIZE=-1]24.0A[/SIZE]
    [SIZE=-1].060 / [/SIZE][SIZE=-1]1.52 / [/SIZE][SIZE=-1]35.0A[/SIZE]
    [SIZE=-1].080 / [/SIZE][SIZE=-1]2.03 / [/SIZE][SIZE=-1]52.0A[/SIZE]
    [SIZE=-1].090 [/SIZE][SIZE=-1]2.29 / [/SIZE][SIZE=-1]65.0A[/SIZE]

    [SIZE=-1]CDA101 / OFH Copper [/SIZE][SIZE=-1]or GlidCop[/SIZE]
    [SIZE=-1].020 / [/SIZE][SIZE=-1]0.51 / [/SIZE][SIZE=-1]4.0 - 10.0 [/SIZE][SIZE=-1](7.0)[/SIZE]
    [SIZE=-1].030 / [/SIZE][SIZE=-1]0.76 / [/SIZE][SIZE=-1]9.0 - 17.0 [/SIZE][SIZE=-1](15.0)[/SIZE]
    [SIZE=-1].040 / [/SIZE][SIZE=-1]1.02 / [/SIZE][SIZE=-1]16.0 - 27.0 [/SIZE][SIZE=-1](25.0)[/SIZE]
    [SIZE=-1].050 / [/SIZE][SIZE=-1]1.27 / [/SIZE][SIZE=-1]25.0 - 42.0 [/SIZE][SIZE=-1](36.0)[/SIZE]
    [SIZE=-1].060 / [/SIZE][SIZE=-1]1.52 / [/SIZE][SIZE=-1]36.0 - 60.0 [/SIZE][SIZE=-1](47.0)[/SIZE]
    [SIZE=-1].080 / [/SIZE][SIZE=-1]2.03 / [/SIZE][SIZE=-1]64.0 - 107.0 [/SIZE][SIZE=-1](73.0)[/SIZE]
    [SIZE=-1].090 / [/SIZE][SIZE=-1]2.29 / [/SIZE][SIZE=-1]81.0 - 135.0 [/SIZE][SIZE=-1](87.0)[/SIZE]

    Copper's data in parenthesis was a recommended target. Again, this is old data that was handed down to me by an old engineering guy who's long since retired & his sources are long unknown.

    Can anyone here help guide a non-EE guy along here? Thanks VERY much for your time, it's greatly appreciated. Happy to furnish additional info about the materials as needed, just need to know what you guys need... :)

    Last edited: Feb 3, 2009
  2. beenthere

    Retired Moderator

    Apr 20, 2004
  3. 84_Carrera

    Thread Starter New Member

    Feb 3, 2009

    I have a customer-furnished graph showing a bare copper wire, .040" dia., in one of our types of parts being brought up from ~ 22°C at 0A, to 65A at 100°C (75A at ~142°C), and the 52 Alloy / Cu Core wire, same dia. hitting around 28A at 100°C / 35A at ~165°C

    I have old notes from that engineer of ours along the following:

    .030" 52 Cu wire, 15A = 56°C; 20A = 84°C; 25A = 130°C - no other notes with that.

    As for material info, I have resistance of Kovar at 294 ohms / cir mil ft; 52 Alloy at 260 ohms / cir mil ft; 52 Alloy-Cu Core at 66 ohms / cir mil ft; copper at 10.37 ohms / cir mil ft; Glidcop at 11.2 ohms / cir mil ft, and for reference, Chromel A (NiChrome) at 648 ohms / cir mil ft

    I found fusing current for a 24AWG (.020") cu wire at 29.2A (vs. ~7A we published), so it looks like we're REALLY conservative if that's accurate.

    Any other material properties I need to provide? Thermal properties? I just don't know how to really calc this stuff out.

    Thanks folks.

    Edit: 0A is 22C, not 42C
    Last edited: Feb 4, 2009
  4. 84_Carrera

    Thread Starter New Member

    Feb 3, 2009
    Still looking for how to what info I need & how to calculate ampacity in these materials' wires, for say 100°C, 150°C & 200°C wire temps.