Joe Gwinn <joegwinn@comcast.net> wrote:> On Wed, 21 Jun 2023 16:06:13 -0000 (UTC), Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote: >>> >> <snip> >>> >>> [2] I wonder if there are any strong non-conductive screws. It >>> wouldn't matter if they had zero clearance to the next board in the >>> crate. Nylon would be too wimpy to scrunch down my mosfets. >>> >>> >>> >> Amazon bought out Small Parts Inc some years back, and still sells things >> like Delrin screws, way cheaper than elsewhere. >> >> Dunno if it’s all NOS or if they’re still making them. > > .<http://dmp-ortho.com/products-catalog/acetal-screws/> > > Acetal is very slippery, so it may be difficult to prevent such a > screw from working loose. > > But acetal does not creep under steady load. > > Joe Gwinn >It also doesn’t get brittle when it dries out. -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
countersinking a TO247 mosfet
Started by ●June 19, 2023
Reply by ●June 21, 20232023-06-21
Reply by ●June 21, 20232023-06-21
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:> Joe Gwinn <joegwinn@comcast.net> wrote: >> On Wed, 21 Jun 2023 16:06:13 -0000 (UTC), Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>> John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote: >>>> >>> <snip> >>>> >>>> [2] I wonder if there are any strong non-conductive screws. It >>>> wouldn't matter if they had zero clearance to the next board in the >>>> crate. Nylon would be too wimpy to scrunch down my mosfets. >>>> >>>> >>>> >>> Amazon bought out Small Parts Inc some years back, and still sells things >>> like Delrin screws, way cheaper than elsewhere. >>> >>> Dunno if it’s all NOS or if they’re still making them. >> >> .<http://dmp-ortho.com/products-catalog/acetal-screws/> >> >> Acetal is very slippery, so it may be difficult to prevent such a >> screw from working loose. >> >> But acetal does not creep under steady load. >> >> Joe Gwinn >> > It also doesn’t get brittle when it dries out. >Plus Amazon sells them for a nickel or so, iirc. -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
Reply by ●June 21, 20232023-06-21
On Wednesday, June 21, 2023 at 7:44:24 AM UTC-7, John Larkin wrote:> On Wed, 21 Jun 2023 21:43:31 +1000, Chris Jones > <lugn...@spam.yahoo.com> wrote: > > >On 20/06/2023 1:49 am, John Larkin wrote:> [1] Don't you hate it when a cafe table has four legs and it tilts all > over the place and spills your coffee?If it's a circular table, rotate it until all four legs contact at the same time.> [2] I wonder if there are any strong non-conductive screws. It > wouldn't matter if they had zero clearance to the next board in the > crate. Nylon would be too wimpy to scrunch down my mosfets.Nah; what you want is to scale heat losses down as much as device sizes have been scaled down. The microfabricators have convinced you that the high power stuff SHOULD be small. Critters smaller than mice are generally cold-blooded because they can't maintain thermal gradients, because high power metabolisms don't work when small.
Reply by ●June 21, 20232023-06-21
On Wed, 21 Jun 2023 15:11:47 -0700 (PDT), whit3rd <whit3rd@gmail.com> wrote:>On Wednesday, June 21, 2023 at 7:44:24?AM UTC-7, John Larkin wrote: >> On Wed, 21 Jun 2023 21:43:31 +1000, Chris Jones >> <lugn...@spam.yahoo.com> wrote: >> >> >On 20/06/2023 1:49 am, John Larkin wrote: > >> [1] Don't you hate it when a cafe table has four legs and it tilts all >> over the place and spills your coffee? > >If it's a circular table, rotate it until all four legs contact at the same time.That obviously doesn't work all the time. If it did I'd have to eat someone else's food.> >> [2] I wonder if there are any strong non-conductive screws. It >> wouldn't matter if they had zero clearance to the next board in the >> crate. Nylon would be too wimpy to scrunch down my mosfets. > >Nah; what you want is to scale heat losses down as much as device sizes >have been scaled down. The microfabricators have convinced you that >the high power stuff SHOULD be small. Critters smaller than mice >are generally cold-blooded because they can't maintain thermal gradients, >because high power metabolisms don't work when small.Given that I'm designing a dummy load board, I don't want to save power. A 200 watt module will sell better than a 20 watt module.
Reply by ●June 21, 20232023-06-21
On Wed, 21 Jun 2023 17:24:09 -0000 (UTC), Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>Joe Gwinn <joegwinn@comcast.net> wrote: >> On Wed, 21 Jun 2023 16:06:13 -0000 (UTC), Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>> John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote: >>>> >>> <snip> >>>> >>>> [2] I wonder if there are any strong non-conductive screws. It >>>> wouldn't matter if they had zero clearance to the next board in the >>>> crate. Nylon would be too wimpy to scrunch down my mosfets. >>>> >>>> >>>> >>> Amazon bought out Small Parts Inc some years back, and still sells things >>> like Delrin screws, way cheaper than elsewhere. >>> >>> Dunno if it?s all NOS or if they?re still making them. >> >> .<http://dmp-ortho.com/products-catalog/acetal-screws/> >> >> Acetal is very slippery, so it may be difficult to prevent such a >> screw from working loose. >> >> But acetal does not creep under steady load. >> >> Joe Gwinn >> >It also doesn�t get brittle when it dries out.Yes. I use it a lot. One trick is to drill screw holes, but don't thread them. Simply screw the steel screw into the somewhat undersize hole in the acetal. Then the screw is not going to back out. Joe Gwinn
Reply by ●June 22, 20232023-06-22
On Wednesday, June 21, 2023 at 4:10:12 PM UTC-7, John Larkin wrote:> On Wed, 21 Jun 2023 15:11:47 -0700 (PDT), whit3rd <whi...@gmail.com> > wrote:> >> [1] Don't you hate it when a cafe table has four legs and it tilts all > >> over the place and spills your coffee? > > > >If it's a circular table, rotate it until all four legs contact at the same time. > That obviously doesn't work all the time.If the legs are the same length, but the floor is warped, it does.> If it did I'd have to eat someone else's food.I presume anyone who can budge a table can shift a chair.
Reply by ●June 22, 20232023-06-22
On Wed, 21 Jun 2023 20:34:07 -0700 (PDT), whit3rd <whit3rd@gmail.com> wrote:>On Wednesday, June 21, 2023 at 4:10:12?PM UTC-7, John Larkin wrote: >> On Wed, 21 Jun 2023 15:11:47 -0700 (PDT), whit3rd <whi...@gmail.com> >> wrote: > >> >> [1] Don't you hate it when a cafe table has four legs and it tilts all >> >> over the place and spills your coffee? >> > >> >If it's a circular table, rotate it until all four legs contact at the same time. >> That obviously doesn't work all the time. > >If the legs are the same length, but the floor is warped, it does.Most floors are pretty flat. The tables are usually the problem.
Reply by ●June 22, 20232023-06-22
On Tue, 20 Jun 2023 09:33:56 -0400, Joe Gwinn <joegwinn@comcast.net> wrote:>On Tue, 20 Jun 2023 03:46:47 -0700, John Larkin ><jlarkin@highlandSNIPMEtechnology.com> wrote: > >>On Mon, 19 Jun 2023 18:57:31 -0700 (PDT), Chris <chris.863@live.com> >>wrote: >> >>>On Tuesday, 20 June 2023 at 01:50:16 UTC+10, John Larkin wrote: >>>> Has anyone done this? I need to get the mounting screw height down. >>>> >>>> I guess I'll have to try it. >>> >>>Rivets? >> >>Rework would be difficult, and a rivet adds height too. >>The reason to not just epoxy the fets down would be the rework issue. >>And the mess, although there are some instant-set thermally conductive >>super-glue things. > >Aluminum solid rivets with a 100-degree cone angle are also available. >Set with an arbor press to avoid shock. > >.<https://www.mcmaster.com/96685A149/>An afterthought: Solid rivets expand when set, and it's not clear that the semiconductor package can handle the resulting radial stress. Joe Gwinn
Reply by ●June 22, 20232023-06-22
On Thu, 22 Jun 2023 10:52:57 -0400, Joe Gwinn <joegwinn@comcast.net> wrote:>On Tue, 20 Jun 2023 09:33:56 -0400, Joe Gwinn <joegwinn@comcast.net> >wrote: > >>On Tue, 20 Jun 2023 03:46:47 -0700, John Larkin >><jlarkin@highlandSNIPMEtechnology.com> wrote: >> >>>On Mon, 19 Jun 2023 18:57:31 -0700 (PDT), Chris <chris.863@live.com> >>>wrote: >>> >>>>On Tuesday, 20 June 2023 at 01:50:16 UTC+10, John Larkin wrote: >>>>> Has anyone done this? I need to get the mounting screw height down. >>>>> >>>>> I guess I'll have to try it. >>>> >>>>Rivets? >>> >>>Rework would be difficult, and a rivet adds height too. >>>The reason to not just epoxy the fets down would be the rework issue. >>>And the mess, although there are some instant-set thermally conductive >>>super-glue things. >> >>Aluminum solid rivets with a 100-degree cone angle are also available. >>Set with an arbor press to avoid shock. >> >>.<https://www.mcmaster.com/96685A149/> > >An afterthought: Solid rivets expand when set, and it's not clear >that the semiconductor package can handle the resulting radial stress. > >Joe GwinnI plan to blind tap four holes into the copper CPU cooler. There's not much thickness until the tap would hit fins. I don't know how a rivet would anchor into the cooler, and replacing a fet would be nasty.
Reply by ●June 22, 20232023-06-22
On Thursday, June 22, 2023 at 7:57:03 AM UTC-7, John Larkin wrote:> I plan to blind tap four holes into the copper CPU cooler. There's not > much thickness until the tap would hit fins. I don't know how a rivet > would anchor into the cooler, and replacing a fet would be nasty.Consider packaging the fets in a hockeypuck package, with controlled clamping force that doesn't have to be limited to an M3 screw... Like here... <https://electricalacademia.com/wp-content/uploads/2020/05/https-textflow-mheducation-com-figures-174307482-59.jpeg>
