aluminum heatsink anodizing
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From: Eeyore on 19 Dec 2008 19:55 Rich Grise wrote: > On Fri, 19 Dec 2008 22:15:43 +0000, Eeyore wrote: > > Rich Grise wrote: > >> Eeyore wrote: > >> > John Larkin wrote: > >> >> > >> >> Hint: smart people machine the heat sink *before* they anodize it. > >> > > >> > Who said mine need any machining ? > >> > >> If it's extruded, it needs to be machined, especially if you're > >> intending to use the hard anodize as the insulator. > > > > Who said anything about extrusions ? > > Every sizeable heatsink I've ever seen has been extruded. What are > you doing, having them cast? Maybe machined from a solid block? Fabricated from sheet. Cheap, lightweight and very efficient. > Please, tell us more about these magic heatsinks that don't need > any heat grease/paste with your magical pads, of which you seem to > be the only happy user in existence. In the most recent instances no insulation is required, so thermapath is fine Graham
From: krw on 19 Dec 2008 19:55 In article <494C41A2.D1FB887A(a)hotmail.com>, rabbitsfriendsandrelations(a)hotmail.com says... > > > John Fields wrote: > > > Eeyore <rabbitsfriendsandrelations(a)hotmail.com> wrote: > > >Phil Allison wrote: > > >> "Adrian Tuddenham" > > >> > > > >> > A point not often appreciated is the possible heat gain when a heatsink > > >> > is operated in bright sunshine. A surface finish which is a poor > > >> > radiator/absorber of radiant heat will work better in those > > >> > circumstances. > > >> > > >> ** Only a complete dope would not find some way to shade the heatsink from > > >> direct sunlight on a hot day. > > > > > >There's no shortage of dopes. > > > > --- > > And you're the proof of the pudding. > > You're out of your depth. That's OK. You're out of your mind. -- Keith
From: Eeyore on 19 Dec 2008 19:57 John Larkin wrote: > Sil-pads suck for serious heat flows. To dump a couple of watts out of > an LM317, fine. For serious power, using sil-pads will force you to > use maybe twice as many power transistors as you'd need with better > materials, which is a pretty serious consideration. > > Based on my measurements, sil-pads never achieve the thetas that the > makers claim. Derating their numbers by 2:1 is prudent. I've had no trouble putting 50W through them with a delta T of ~ 10C in TO-3 measured by thermocouple. Not the grey ones of course. Graham
From: Eeyore on 19 Dec 2008 19:59 John Larkin wrote: > Eeyore <rabbitsfriendsandrelations(a)hotmail.com> wrote: > >John Larkin wrote: > > > >> No insulators at all of course... the heatsink is hot to the load. > > > >Isn't that just what I recommended ? > > Was it? For optimum cooling, of course ! > >> This is in a 17KW peak-output MRI gradient driver. > > > >And the dissipation in the devices is ? > > About 300 watts peak each. Cheat ! Average figure please ? Which you damn well know is the important one unless your pulses are several seconds long. Graham
From: Jim Thompson on 19 Dec 2008 20:04
On Sat, 20 Dec 2008 00:51:46 +0000, Eeyore <rabbitsfriendsandrelations(a)hotmail.com> wrote: > > >John Fields wrote: > >> Eeyore <rabbitsfriendsandrelations(a)hotmail.com> wrote: >> >Phil Allison wrote: >> >> "Adrian Tuddenham" >> >> > >> >> > A point not often appreciated is the possible heat gain when a heatsink >> >> > is operated in bright sunshine. A surface finish which is a poor >> >> > radiator/absorber of radiant heat will work better in those >> >> > circumstances. >> >> >> >> ** Only a complete dope would not find some way to shade the heatsink from >> >> direct sunlight on a hot day. >> > >> >There's no shortage of dopes. >> >> --- >> And you're the proof of the pudding. > >You're out of your depth. > >Graham Graham, I think you've lost your Reynolds number ?:-) ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine Sometimes I even put it in the food |