Has anyone done this? I need to get the mounting screw height down. I guess I'll have to try it.
countersinking a TO247 mosfet
Started by ●June 19, 2023
Reply by ●June 19, 20232023-06-19
mandag den 19. juni 2023 kl. 17.50.16 UTC+2 skrev John Larkin:> Has anyone done this? I need to get the mounting screw height down. > > I guess I'll have to try it.how low do you need? https://www.mcmaster.com/products/low-profile-head-socket-cap-screws/alloy-steel-ultra-low-profile-socket-head-screws/
Reply by ●June 19, 20232023-06-19
On Monday, June 19, 2023 at 11:50:16 AM UTC-4, John Larkin wrote:> Has anyone done this? I need to get the mounting screw height down. > > I guess I'll have to try it.Countersink it for a flat head. Head should end up flush with the package, can't beat that: https://www.homedepot.com/b/Hardware-Fasteners-Screws-Machine-Screws/Flat-Head/N-5yc1vZc27iZ1z18t94
Reply by ●June 19, 20232023-06-19
On Mon, 19 Jun 2023 08:57:14 -0700 (PDT), Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:>mandag den 19. juni 2023 kl. 17.50.16 UTC+2 skrev John Larkin: >> Has anyone done this? I need to get the mounting screw height down. >> >> I guess I'll have to try it. > >how low do you need? https://www.mcmaster.com/products/low-profile-head-socket-cap-screws/alloy-steel-ultra-low-profile-socket-head-screws/The heights are good, the prices aren't! A regular screw and a lockwasher cost me over 0.1", and I need less. With locktite, I can eliminate the lockwasher. A really thin custom AlN insulator will help a bit. Isolated TO-247s are expensive and hard to get. I could just epoxy the fets down, but that has downsides.
Reply by ●June 19, 20232023-06-19
On Mon, 19 Jun 2023 08:57:14 -0700 (PDT), Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:>mandag den 19. juni 2023 kl. 17.50.16 UTC+2 skrev John Larkin: >> Has anyone done this? I need to get the mounting screw height down. >> >> I guess I'll have to try it. > >how low do you need? https://www.mcmaster.com/products/low-profile-head-socket-cap-screws/alloy-steel-ultra-low-profile-socket-head-screws/You are really good at parts research. Please email me.
Reply by ●June 19, 20232023-06-19
mandag den 19. juni 2023 kl. 18.13.01 UTC+2 skrev John Larkin:> On Mon, 19 Jun 2023 08:57:14 -0700 (PDT), Lasse Langwadt Christensen > <lang...@fonz.dk> wrote: > > >mandag den 19. juni 2023 kl. 17.50.16 UTC+2 skrev John Larkin: > >> Has anyone done this? I need to get the mounting screw height down. > >> > >> I guess I'll have to try it. > > > >how low do you need? https://www.mcmaster.com/products/low-profile-head-socket-cap-screws/alloy-steel-ultra-low-profile-socket-head-screws/ > The heights are good, the prices aren't!yeh, but now you konw they exist and they can surely be found much cheaper, I guess you want something like #4-40, but M3 seems to be more common https://www.ebay.co.uk/itm/284167006281 https://ogsecure.co.uk/products/m3-ultra-thin-wafer-flat-head-low-profile-screws-bolt-allen-key-stainless-steel?variant=40403358318653
Reply by ●June 19, 20232023-06-19
mandag den 19. juni 2023 kl. 18.13.01 UTC+2 skrev John Larkin:> On Mon, 19 Jun 2023 08:57:14 -0700 (PDT), Lasse Langwadt Christensen > <lang...@fonz.dk> wrote: > > >mandag den 19. juni 2023 kl. 17.50.16 UTC+2 skrev John Larkin: > >> Has anyone done this? I need to get the mounting screw height down. > >> > >> I guess I'll have to try it. > > > >how low do you need? https://www.mcmaster.com/products/low-profile-head-socket-cap-screws/alloy-steel-ultra-low-profile-socket-head-screws/ > The heights are good, the prices aren't! > > A regular screw and a lockwasher cost me over 0.1", and I need less. > With locktite, I can eliminate the lockwasher. > > A really thin custom AlN insulator will help a bit. Isolated TO-247s > are expensive and hard to get. > > I could just epoxy the fets down, but that has downsides.maybe something like this? https://www.digikey.dk/da/products/detail/aavid-thermal-division-of-boyd-corporation/MAX08NG/1625322
Reply by ●June 19, 20232023-06-19
On 2023-06-19 11:49, John Larkin wrote:> Has anyone done this? I need to get the mounting screw height down. > > I guess I'll have to try it. >Be careful about overtorqueing it, because stretching the metal might conceivably cause the die to crack or delaminate. I'd definitely want to torture-test for that possibility. 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
Reply by ●June 19, 20232023-06-19
On Mon, 19 Jun 2023 10:32:14 -0700 (PDT), Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:>mandag den 19. juni 2023 kl. 18.13.01 UTC+2 skrev John Larkin: >> On Mon, 19 Jun 2023 08:57:14 -0700 (PDT), Lasse Langwadt Christensen >> <lang...@fonz.dk> wrote: >> >> >mandag den 19. juni 2023 kl. 17.50.16 UTC+2 skrev John Larkin: >> >> Has anyone done this? I need to get the mounting screw height down. >> >> >> >> I guess I'll have to try it. >> > >> >how low do you need? https://www.mcmaster.com/products/low-profile-head-socket-cap-screws/alloy-steel-ultra-low-profile-socket-head-screws/ >> The heights are good, the prices aren't! >> >> A regular screw and a lockwasher cost me over 0.1", and I need less. >> With locktite, I can eliminate the lockwasher. >> >> A really thin custom AlN insulator will help a bit. Isolated TO-247s >> are expensive and hard to get. >> >> I could just epoxy the fets down, but that has downsides. > >maybe something like this? https://www.digikey.dk/da/products/detail/aavid-thermal-division-of-boyd-corporation/MAX08NG/1625322I've done that https://www.dropbox.com/s/nmyb9pz0qpma2xa/Amp.jpg?dl=0 but it adds more height. I'll have boards in a card cage on 1.6" centers, and I'm stacking a CPU cooler/fan thing with giant mosfets. The screw heads could hit adjacent boards. I could go to TO220s, which need less screw height.
Reply by ●June 19, 20232023-06-19
On Mon, 19 Jun 2023 09:04:46 -0700 (PDT), Fred Bloggs <bloggs.fredbloggs.fred@gmail.com> wrote:>On Monday, June 19, 2023 at 11:50:16?AM UTC-4, John Larkin wrote: >> Has anyone done this? I need to get the mounting screw height down. >> >> I guess I'll have to try it. > >Countersink it for a flat head. Head should end up flush with the package, can't beat that: > >https://www.homedepot.com/b/Hardware-Fasteners-Screws-Machine-Screws/Flat-Head/N-5yc1vZc27iZ1z18t94That's the idea, as long as it doesn't destroy the silicon. We'd need carbide countersinks. That mosfet epoxy is hell on tools.
