IR is insane
in [Design]
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From: JosephKK on 23 Mar 2010 01:45 On Sun, 21 Mar 2010 17:42:34 -0500, "krw(a)att.bizzzzzzzzzzzz" <krw(a)att.bizzzzzzzzzzzz> wrote: >On Sun, 21 Mar 2010 10:43:02 -0700, "JosephKK"<quiettechblue(a)yahoo.com> wrote: > >>On Sat, 20 Mar 2010 18:09:39 -0500, "krw(a)att.bizzzzzzzzzzzz" <krw(a)att.bizzzzzzzzzzzz> wrote: >> >>>On Sat, 20 Mar 2010 12:12:14 -0700, Archimedes' Lever >>><OneBigLever(a)InfiniteSeries.Org> wrote: >>> >>>>On Sat, 20 Mar 2010 10:56:18 -0700, John Larkin >>>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>>> >>>>>Boiling liquid carries away far more heat than still or even flowing >>>>>liquid. Since IR cheats as hard as they can, we can assume they used >>>>>boiling liquid. I fact, they say so. >>>> >>>> >>>> Chilled fluorinert does not need to be boiling to have thermal >>>>efficiency. >>> >>>Wrong again, AlwaysWrong. How do you think Fluorinert works? By magic? >> >>While i have seen Flourinert cooling maybe half a dozen times, only once was >>it used in phase change mode. I mostly saw circulated chilled liquid baths. >>Works real good for temperature stabilizing standard resistors. > >*Every* time I've seen it used there was a phase change somewhere in the >process. There are a *lot* of cheaper and better alternatives if a lowish >temper phase change isn't needed. Fluorinert doesn't have a stellar specific >heat. At which point i have to ask, was it Flourinert or just some refrigerant. See: http://en.wikipedia.org/wiki/Fluorinert http://products3.3m.com/catalog/us/en001/oil_gas/specialty_materials/node_HX0DNRHXKWge/root_GST1T4S9TCgv/vroot_G1F6DNZDBVge/theme_us_oilgas_3_0/command_AbcPageHandler/output_html
From: JosephKK on 23 Mar 2010 02:13 On Mon, 22 Mar 2010 20:11:15 +0000 (UTC), don(a)manx.misty.com (Don Klipstein) wrote: >In article <410aq5pjiu4e0ig8j1s10hhfmohnu9o9n6(a)4ax.com>, John Larkin wrote: >>On 20 Mar 2010 14:15:15 GMT, Glen Walpert <nospam(a)null.void> wrote: >> >>>On Sat, 20 Mar 2010 07:24:54 +0000, Don Klipstein wrote: > >>>(In short, plenty including:) > >>>ISTR a previous thread where someone turned up a maximum current test >>>procedure where the device was submerged in a "phase change fluid" for >>>the peak current test. Not a fluid cooled heatsink; direct immersion of >>>the device. > >>><SNIP more along these lines to edit for space> > >>I haven't done the math on this, but I suspect the source lead would >>vaporize at 195 amps, much less 340. If it were immersed in a boiling >>liquid, it would probably be OK. I think that's how they test them. > > I got into a mood to try the math on this. > > Back to the datasheet, > >http://www.irf.com/product-info/datasheets/data/irfs3006pbf.pdf > > My eyeball-estimate of the length of the source lead, between the solder >joint and the bonding wire, is 8 mm, about half with a narrow portion >(datasheet says .51 by .38 mm minimum), and about half with a wide portion >(datasheet says 1.14 by .38 mm minimum). > > Wikipedia says the resistivity of copper at 20 C is 1.72E-8 ohm-meter, >which is 1.72E-5 ohm-mm. I would like a 75 C figure, which is 19.5% >higher, and that is 2.055E-5 ohm-mm. From here, I get .425 milliohm for >the narrow half and .19 milliohm for the wide half, for a total of .515 >milliohm. > > .000515 times square of 195 amps is 19.6 watts. That sounds >unreasonable to me. I seem to think that the narrow part of the source >lead will melt. > > Try for the wide half alone: .00019 ohm times square of 195 amps is 7.2 >watts. Repeat for 170 amps, and that is 5.5 watts. That sounds to me >able to be heatsunk from the source lead by soldering big fat wire to the >wide part of the source lead, but it also sounds to me sort of insane to >package such a big MOSFET with such requirements in such a small package. > > - Don Klipstein (don(a)misty.com) As if you have not caught on yet, the ratings are for big heat sink in a tank full of LN2 (liquid nitrogen). I doubt you need to review "infinite heat sink".
From: Archimedes' Lever on 23 Mar 2010 10:06 On Mon, 22 Mar 2010 22:45:30 -0700, "JosephKK"<quiettechblue(a)yahoo.com> wrote: >On Sun, 21 Mar 2010 17:42:34 -0500, "krw(a)att.bizzzzzzzzzzzz" <krw(a)att.bizzzzzzzzzzzz> wrote: > >>On Sun, 21 Mar 2010 10:43:02 -0700, "JosephKK"<quiettechblue(a)yahoo.com> wrote: >> >>>On Sat, 20 Mar 2010 18:09:39 -0500, "krw(a)att.bizzzzzzzzzzzz" <krw(a)att.bizzzzzzzzzzzz> wrote: >>> >>>>On Sat, 20 Mar 2010 12:12:14 -0700, Archimedes' Lever >>>><OneBigLever(a)InfiniteSeries.Org> wrote: >>>> >>>>>On Sat, 20 Mar 2010 10:56:18 -0700, John Larkin >>>>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>>>> >>>>>>Boiling liquid carries away far more heat than still or even flowing >>>>>>liquid. Since IR cheats as hard as they can, we can assume they used >>>>>>boiling liquid. I fact, they say so. >>>>> >>>>> >>>>> Chilled fluorinert does not need to be boiling to have thermal >>>>>efficiency. >>>> >>>>Wrong again, AlwaysWrong. How do you think Fluorinert works? By magic? >>> >>>While i have seen Flourinert cooling maybe half a dozen times, only once was >>>it used in phase change mode. I mostly saw circulated chilled liquid baths. >>>Works real good for temperature stabilizing standard resistors. >> >>*Every* time I've seen it used there was a phase change somewhere in the >>process. There are a *lot* of cheaper and better alternatives if a lowish >>temper phase change isn't needed. Fluorinert doesn't have a stellar specific >>heat. > >At which point i have to ask, was it Flourinert or just some refrigerant. >See: > >http://en.wikipedia.org/wiki/Fluorinert > >http://products3.3m.com/catalog/us/en001/oil_gas/specialty_materials/node_HX0DNRHXKWge/root_GST1T4S9TCgv/vroot_G1F6DNZDBVge/theme_us_oilgas_3_0/command_AbcPageHandler/output_html The idiot was thinking of a CFC.
From: krw on 23 Mar 2010 20:29 On Tue, 23 Mar 2010 07:06:37 -0700, Archimedes' Lever <OneBigLever(a)InfiniteSeries.Org> wrote: >On Mon, 22 Mar 2010 22:45:30 -0700, "JosephKK"<quiettechblue(a)yahoo.com> >wrote: > >>On Sun, 21 Mar 2010 17:42:34 -0500, "krw(a)att.bizzzzzzzzzzzz" <krw(a)att.bizzzzzzzzzzzz> wrote: >> >>>On Sun, 21 Mar 2010 10:43:02 -0700, "JosephKK"<quiettechblue(a)yahoo.com> wrote: >>> >>>>On Sat, 20 Mar 2010 18:09:39 -0500, "krw(a)att.bizzzzzzzzzzzz" <krw(a)att.bizzzzzzzzzzzz> wrote: >>>> >>>>>On Sat, 20 Mar 2010 12:12:14 -0700, Archimedes' Lever >>>>><OneBigLever(a)InfiniteSeries.Org> wrote: >>>>> >>>>>>On Sat, 20 Mar 2010 10:56:18 -0700, John Larkin >>>>>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>>>>> >>>>>>>Boiling liquid carries away far more heat than still or even flowing >>>>>>>liquid. Since IR cheats as hard as they can, we can assume they used >>>>>>>boiling liquid. I fact, they say so. >>>>>> >>>>>> >>>>>> Chilled fluorinert does not need to be boiling to have thermal >>>>>>efficiency. >>>>> >>>>>Wrong again, AlwaysWrong. How do you think Fluorinert works? By magic? >>>> >>>>While i have seen Flourinert cooling maybe half a dozen times, only once was >>>>it used in phase change mode. I mostly saw circulated chilled liquid baths. >>>>Works real good for temperature stabilizing standard resistors. >>> >>>*Every* time I've seen it used there was a phase change somewhere in the >>>process. There are a *lot* of cheaper and better alternatives if a lowish >>>temper phase change isn't needed. Fluorinert doesn't have a stellar specific >>>heat. >> >>At which point i have to ask, was it Flourinert or just some refrigerant. >>See: >> >>http://en.wikipedia.org/wiki/Fluorinert >> >>http://products3.3m.com/catalog/us/en001/oil_gas/specialty_materials/node_HX0DNRHXKWge/root_GST1T4S9TCgv/vroot_G1F6DNZDBVge/theme_us_oilgas_3_0/command_AbcPageHandler/output_html > > > The idiot was thinking of a CFC. AlwaysWrong is *ALWAYS* wrong.
From: John Larkin on 23 Mar 2010 20:54
On Tue, 23 Mar 2010 19:29:32 -0500, "krw(a)att.bizzzzzzzzzzzz" <krw(a)att.bizzzzzzzzzzzz> wrote: >On Tue, 23 Mar 2010 07:06:37 -0700, Archimedes' Lever ><OneBigLever(a)InfiniteSeries.Org> wrote: > >>On Mon, 22 Mar 2010 22:45:30 -0700, "JosephKK"<quiettechblue(a)yahoo.com> >>wrote: >> >>>On Sun, 21 Mar 2010 17:42:34 -0500, "krw(a)att.bizzzzzzzzzzzz" <krw(a)att.bizzzzzzzzzzzz> wrote: >>> >>>>On Sun, 21 Mar 2010 10:43:02 -0700, "JosephKK"<quiettechblue(a)yahoo.com> wrote: >>>> >>>>>On Sat, 20 Mar 2010 18:09:39 -0500, "krw(a)att.bizzzzzzzzzzzz" <krw(a)att.bizzzzzzzzzzzz> wrote: >>>>> >>>>>>On Sat, 20 Mar 2010 12:12:14 -0700, Archimedes' Lever >>>>>><OneBigLever(a)InfiniteSeries.Org> wrote: >>>>>> >>>>>>>On Sat, 20 Mar 2010 10:56:18 -0700, John Larkin >>>>>>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>>>>>> >>>>>>>>Boiling liquid carries away far more heat than still or even flowing >>>>>>>>liquid. Since IR cheats as hard as they can, we can assume they used >>>>>>>>boiling liquid. I fact, they say so. >>>>>>> >>>>>>> >>>>>>> Chilled fluorinert does not need to be boiling to have thermal >>>>>>>efficiency. >>>>>> >>>>>>Wrong again, AlwaysWrong. How do you think Fluorinert works? By magic? >>>>> >>>>>While i have seen Flourinert cooling maybe half a dozen times, only once was >>>>>it used in phase change mode. I mostly saw circulated chilled liquid baths. >>>>>Works real good for temperature stabilizing standard resistors. >>>> >>>>*Every* time I've seen it used there was a phase change somewhere in the >>>>process. There are a *lot* of cheaper and better alternatives if a lowish >>>>temper phase change isn't needed. Fluorinert doesn't have a stellar specific >>>>heat. >>> >>>At which point i have to ask, was it Flourinert or just some refrigerant. >>>See: >>> >>>http://en.wikipedia.org/wiki/Fluorinert >>> >>>http://products3.3m.com/catalog/us/en001/oil_gas/specialty_materials/node_HX0DNRHXKWge/root_GST1T4S9TCgv/vroot_G1F6DNZDBVge/theme_us_oilgas_3_0/command_AbcPageHandler/output_html >> >> >> The idiot was thinking of a CFC. > >AlwaysWrong is *ALWAYS* wrong. You've gotta admire him for his dedication. John |