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Re: mounting a pot core

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On 2026-01-21 11:45, john larkin wrote:>
 > 
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
 >
 > My mechanical design guy is great, and pot cores are a PITA.
 >
 > This will be a transmission-line transformer, and I want all the
 > volt-seconds possible, so the pot core has to be big and barely fit in
 > the box. I've argued that zero vertical clearance is OK - let the top
 > cover and the PCB flex a bit - but mechanical people don't seem to
 > like that idea.

Yeah, putting the copper under much tension isn't a growth strategy. 
Stress due to bending is quadratic in the curvature, so a little bit is 
no problem, but how much is OK, I don't know.

IBM's famed Thermal Conduction Modules (TCMs) originally used sintered 
alumina/refractory metal bricks (dim memory says niobium) holding either 
100 or 121 flip chips.

They were brutally reliable--not a single field failure in 30 years--but 
had a dielectric constant of almost 10, so they were slow.

The packaging folks at Yorktown and East Fishkill came up with a faster 
technology based on copper metal and glass-ceramic bricks with an 
epsilon of 5.  That sped things up by 40%, which was a win as far as it 
went.  Trouble was, they were hopelessly unreliable.

In the original model, the metal had a lower CTE than the ceramic, so 
that once the brick cooled from red heat, the metal was always in 
compression, which prevented cracks from propagating.  However, copper 
has a higher CTE than glass ceramic, so that the copper was always in 
tension. That's for a good time, not a long time.

A pal of mine figured out a fix that my caveman side found very 
appealing: they dunked the hot substrates in oil, and the resulting 
thermal shock cracked all the copper loose from the glass, relieving the 
stress.  That got them back to nearly perfect reliability.

(Later they went to copper/polyimide, I think.)

 >
 > Someone suggested a bump in the top cover, like old muscle cars had
 > for carburetors.

Nowadays people just cut holes in the hood. ;)

Cheers

Phil Hobbs

-- 
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

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Thread

mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-21 08:45 -0800
  Re: mounting a pot core Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2026-01-21 12:28 -0500
  Re: mounting a pot core Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2026-01-21 12:28 -0500
    Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-21 10:11 -0800
  Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-22 04:49 +1100
    Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-21 10:18 -0800
      Re: mounting a pot core Jeroen Belleman <jeroen@nospam.please> - 2026-01-21 23:47 +0100
        Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-21 16:34 -0800
          Re: mounting a pot core Joe Gwinn <joegwinn@comcast.net> - 2026-01-21 19:48 -0500
            Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-21 17:06 -0800
            Re: mounting a pot core Jeroen Belleman <jeroen@nospam.please> - 2026-01-22 13:17 +0100
              Re: mounting a pot core Joe Gwinn <joegwinn@comcast.net> - 2026-01-22 12:47 -0500
                Re: mounting a pot core Joe Gwinn <joegwinn@comcast.net> - 2026-01-22 15:49 -0500
                Re: mounting a pot core Jeroen Belleman <jeroen@nospam.please> - 2026-01-22 23:49 +0100
          Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-22 17:57 +1100
            Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-22 08:31 -0800
              Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-23 15:57 +1100
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-23 06:24 -0800
                Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-24 03:35 +1100
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-23 08:40 -0800
                Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-24 17:01 +1100
          Re: mounting a pot core Jeroen Belleman <jeroen@nospam.please> - 2026-01-22 12:59 +0100
          Re: mounting a pot core legg <legg@nospam.magma.ca> - 2026-01-22 10:58 -0500
            Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-22 10:57 -0800
              Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-23 16:01 +1100
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-23 06:19 -0800
                Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-24 03:19 +1100
                Re: mounting a pot core liz@poppyrecords.invalid.invalid (Liz Tuddenham) - 2026-01-24 19:25 +0000
                Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-25 14:33 +1100
                Re: mounting a pot core liz@poppyrecords.invalid.invalid (Liz Tuddenham) - 2026-01-25 11:07 +0000
                Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-26 02:46 +1100
                Re: mounting a pot core legg <legg@nospam.magma.ca> - 2026-01-25 08:51 -0500
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-25 08:08 -0800
                Re: mounting a pot core legg <legg@nospam.magma.ca> - 2026-01-25 22:44 -0500
                Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-26 17:56 +1100
                Re: mounting a pot core legg <legg@nospam.magma.ca> - 2026-01-26 10:50 -0500
                Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-27 03:23 +1100
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-26 08:51 -0800
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-26 07:53 -0800
                Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-27 03:36 +1100
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-26 08:48 -0800
                Re: mounting a pot core Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2026-01-26 13:12 -0500
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-26 10:58 -0800
                Re: mounting a pot core Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2026-01-26 20:36 +0000
                Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-27 14:30 +1100
      Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-22 17:51 +1100
        Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-22 11:09 -0800
          Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-23 16:16 +1100
            Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-23 06:13 -0800
              Re: mounting a pot core Jeroen Belleman <jeroen@nospam.please> - 2026-01-23 16:07 +0100
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-23 08:22 -0800
                Re: mounting a pot core Jeroen Belleman <jeroen@nospam.please> - 2026-01-24 12:17 +0100
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-24 07:54 -0800
                Re: mounting a pot core Jeroen Belleman <jeroen@nospam.please> - 2026-01-25 13:04 +0100
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-25 07:33 -0800
                Re: mounting a pot core Jeroen Belleman <jeroen@nospam.please> - 2026-01-25 17:32 +0100
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-25 11:12 -0800
                Re: mounting a pot core JM <sunaecoNoChoppedPork@gmail.com> - 2026-01-25 19:44 +0000
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-25 13:07 -0800
                Re: mounting a pot core JM <sunaecoNoChoppedPork@gmail.com> - 2026-01-25 22:40 +0000
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-25 17:29 -0800
                Re: mounting a pot core JM <sunaecoNoChoppedPork@gmail.com> - 2026-01-25 19:40 +0000
              Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-24 03:39 +1100
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-23 10:09 -0800
                Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-24 16:49 +1100
  Re: mounting a pot core legg <legg@nospam.magma.ca> - 2026-01-22 10:46 -0500
    Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-22 11:16 -0800

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