mandag den 19. juni 2023 kl. 20.11.58 UTC+2 skrev John Larkin:> On Mon, 19 Jun 2023 09:04:46 -0700 (PDT), Fred Bloggs > <bloggs.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-5yc1vZc27iZ1z18t94 > That's the idea, as long as it doesn't destroy the silicon. > > We'd need carbide countersinks. That mosfet epoxy is hell on tools.might be better with a counter bore instead of a counter sink
countersinking a TO247 mosfet
Started by ●June 19, 2023
Reply by ●June 19, 20232023-06-19
Reply by ●June 19, 20232023-06-19
On Mon, 19 Jun 2023 11:27:39 -0700 (PDT), Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:>mandag den 19. juni 2023 kl. 20.11.58 UTC+2 skrev John Larkin: >> On Mon, 19 Jun 2023 09:04:46 -0700 (PDT), Fred Bloggs >> <bloggs.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-5yc1vZc27iZ1z18t94 >> That's the idea, as long as it doesn't destroy the silicon. >> >> We'd need carbide countersinks. That mosfet epoxy is hell on tools. > >might be better with a counter bore instead of a counter sinkYes, we could drop in a lockwasher.
Reply by ●June 19, 20232023-06-19
On Mon, 19 Jun 2023 08:49:52 -0700, John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:>Has anyone done this? I need to get the mounting screw height down. > >I guess I'll have to try it.I'm working from home today and I have a hand drill and a very rusty old countersink, a family heirloom. https://www.dropbox.com/scl/fi/y5s1bsc2omn341rnxkicq/TO247_countersunk_4-40.jpg?dl=0&rlkey=cqenr4ev8iic5zgujqor8cns1 This looks OK. The 4-40 screw should apply plenty of force and it centers the fet nicely. It would need locktite so thermal cycling doesn't loosen it up.
Reply by ●June 19, 20232023-06-19
On Mon, 19 Jun 2023 09:12:39 -0700, John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:>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.Stainless steel flat head hex socket screws with a 100-degree cone total angle are common, originally developed for use in airplanes. .<https://www.mcmaster.com/90729A166/> Suitable 100-degree carbide countersinks are also available. Joe Gwinn
Reply by ●June 19, 20232023-06-19
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? -- Cheers, Chris.
Reply by ●June 20, 20232023-06-20
On 6/19/23 18:57, Chris 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? > > -- > Cheers, > Chris.A copper rivet could work, but there are issues with installing: the nose of the rivet setting tool may want to mash something else nearby...
Reply by ●June 20, 20232023-06-20
On Monday, June 19, 2023 at 8:50:16 AM UTC-7, John Larkin wrote:> Has anyone done this? I need to get the mounting screw height down. > > I guess I'll have to try it.The hole is 3.5mm, so an M3 flat head cap screw with a countersinked washer would hold it down; here are 1.8mm thick offerings for M3 screws. Is 1.8mm too high? <https://www.mcmaster.com/products/countersunk-washers/> I'm not seeing any measure of the recess dimensions around the clear hole, though. The screw would be capable of touching the tab, which might not work for you.
Reply by ●June 20, 20232023-06-20
On 2023-06-19, John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:> Has anyone done this? I need to get the mounting screw height down.Sounds risky, the wedge shape of the screw head will be working against the glass-filled resin of the body. I don't think that stuff is very strong in tension.> I guess I'll have to try it.-- Jasen. 🇺🇦 Слава Україні
Reply by ●June 20, 20232023-06-20
On 2023-06-20, 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?blind rivets tend to cause mechanical shock when the stem snaps leading to early failures. Swage rivets - maybe that could work if you can find a way to set them without damaging the MOSFET. -- Jasen. 🇺🇦 Слава Україні
Reply by ●June 20, 20232023-06-20
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.
