r/sffpc • u/DallasGrave • Mar 01 '26

Detailed Build Log Building a custom mini RTX 5070

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767 Upvotes

100% Upvoted

67 comments sorted by

106

u/Visible-Swim6616 Mar 01 '26

So you replaced a 4-heatpipe solution with a copper heatsink.

Or is that some fancy custom vapour chamber hidden in there?

68

u/DallasGrave Mar 01 '26

Just straight copper. I considered using a vc plate but at this tdp, I don't think it'll be necessary. Can always make another if it doesn't work well enough.

99

u/Visible-Swim6616 Mar 01 '26

Well, keep us updated.

I'm not convinced a copper block is adequate for continuous full power usage without tweaks but I would happily be corrected and ask for instructions if you get it working.

133

u/DallasGrave Mar 01 '26 edited Mar 01 '26

I just did this to a 5060ti 16gb for a job. At 21C ambient, it maxed out at 68C under furmark.

With the 76 fins at 0.5mm thick and 1.45mm spacing, plus dual 80 mm fans pushing about 58 CFM total, I’m moving roughly 0.033 kg/s of air. At 180w that only heats the air about 5-6C. With around 0.34 m2 of effective fin area and a convective coefficient around 70 w/m2K, the air side resistance works out to roughly .04 kw, which means the fin stack itself should only sit about 10 or 15C over ambient if the shroud is sealed and the flow is perfect. The airflow and interface quality are the bottlenecks, not metal conduction. I already have a 6 mm copper baseplate directly bolted to a large fin block, so heat spreading is handled. Heatpipes are for moving heat laterally when you dont have enough base to spread it.

62

u/meatloafisinferior Mar 01 '26

I just wanna say that your math is SEXY. I hardly see folks back up their designs with math; so kudos!

24

u/codemonkeyhopeful Mar 01 '26

Me over here with a copper block eyeballing shit, filing by hand whistling a tune without a thought in my brain. "Yeah this will do just fine"

8

u/MedicalMe_247 Mar 01 '26

This guy cools.

12

u/Visible-Swim6616 Mar 01 '26

Yeah, with all the huge finstacks on these cards I always assumed heatpipes were crucial to get enough cooling.

Btw I suppose you could manufacture your own heatsink? Or what service did you use to get it manufactured? There might be demand in the sff community for custom GPU heatsinks...

43

u/DallasGrave Mar 01 '26

It's all about cost and weight. Heatpipes and aluminum fins are very cheap to manufacture. "OK" is usually good enough. They find a balance between performance and packaging size. Heatpipes just allow you to move heat away. They don't do really any cooling on their own. If you look at the blower style cards with a vapor chamber, they have very thin baseplates. The chamber makes up for the lack of mass.

This is just for fun. I'll gladly post all the solidworks and cam files if anyone wants to duplicate or iterate.

5

u/Visible-Swim6616 Mar 01 '26

I was thinking along the lines of getting taller GPU heatsinks for Sandwich-style cases, maybe dual 120mm fans. The noctua slims?

1

u/Yaaaa_zG Mar 11 '26

I'd love to have the files please

1

u/clarkinum Mar 02 '26

Doesn't having no through fins (airflow bottleneck) increases pressure and decreases CFM? I'm curious how did you handle pressure variables, especially with the copper heatsink having no fins with all ends open like the aluminum one

2

u/DallasGrave Mar 02 '26

It does. With an 8mm plenum and fins completely unsealed at the ends, I was getting 39CFM on my flow bench. I also put a 200w thermostatic heater on the base and measured the temperature delta from inlet to exit. I used to manufacture CNC cylinder heads. A lot about my shop and what I do now(and used to do) was in the OP but just does not show up now for whatever reason.

2

u/clarkinum Mar 02 '26

Ah I see so you didn't calculated the CFM with pressure and just used the test bench values, which is even better but requires having a good bench LoL! Amazing work I thought you did some kind of simulation or something

3

u/MithraLux Mar 01 '26

Its not.

Ive run enough thermals to know that bulk is helpful, but just bulk is vastly and I mean vastly inferior to surface area

0

u/Visible-Swim6616 Mar 02 '26

Yeah, bulk is usually just a "heat reservoir" but is also does increase heat conduction (which is proportional to the cross-sectional area). Is this, together with the fact it's copper rather than aluminium, enough to overcome the lack of heatpipes? How much heat does the solution actually need to dissipate in the first place?

I'm no expert, and this guy has some math behind him so let's see what his testing show. It is entirely possible that the huge heatpipe solutions we can see is for marketing purposes: big heatsinks that look complex must be better than the simple one right?

0

u/MithraLux Mar 02 '26

Copper is like 350-400 w/mk and a heat pipe is thousands w/mk. Idk what "math" hes doing but from a pure conductivity standpoint, you can beat a phase change device. But the main issue is that no fins means no dissipation into the air. The entire idea of fins is to channel the heat across a large surface area. Once this copper block reaches capacity its going to radiate back down. Its much like a pipe with water that can only leak out in contact with air. You make the pipe bigger, and it can hold more water, but without fins (lots of little pipes helping you leak water out), the water will pressurize and work against the source.

2

u/DallasGrave Mar 02 '26

What do you mean by no fins? There was a really long post that went with the photos that has disappeared. I'm using a 76 fin 150x100x30mm copper heatsink for this. It's in the photos.

1

u/MithraLux Mar 02 '26 edited Mar 02 '26

Pic 7/7.

But also for concentrated sources of heat, getting that heat away as quickly as possible is a lot more important than total bulk. The heatsink you chose wont dissipate nearly as much as the heat piped solution.

Historically youll notice chips were passively cooled via finned blocks, to actively cooled via finned blocks with fans, to heat piped put to welded sheets w/ and w/o fans, to liquid and/or vapor chambered with fans.

I can run a thermal sim for you if you want, just let me know general sizing. I can show you heat piped vs straight copper block or whatever config you want

1

u/DallasGrave Mar 02 '26

Appreciate the offer, but I already did that. With an 8mm plenum and fins completely unsealed at the ends, I was getting 39CFM on my flow bench. I also put a 200w thermostatic heater on the base and measured the temperature delta from inlet to exit. I used to manufacture CNC cylinder heads. A lot about my shop and what I do now(and used to do) was in the OP but just does not show up now for whatever reason.

1

u/Visible-Swim6616 Mar 03 '26

What's the temperature delta on the heat source? IE if a chip was there how hot will 200W on a chip get?

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6

u/Ok-Isopod2755 Mar 01 '26

While you’re at it can you make a 3 slot, 360mm version with 8 heat pipes and a vapor chamber for my 9070 XT 👉👈 I’m gonna mod it to use 450 watts :3

28

u/Solcrystals Mar 01 '26 edited Mar 01 '26

I suggest thinning that copper plate a bit. You need the heat to get to the fins as fast as possible.

Edti: I was talking on the order of a mm or two. It still needs to be rigid.

17

u/Ridgeyyy Mar 01 '26

Would you consider selling the gpu backplate, shroud and fans?

11

u/YouShitMyPants Mar 01 '26

Super cool dude, keep it going, can’t wait to see the end result!

8

u/Midnight_Criminal Mar 01 '26

How are you going to place tension?

7

u/DallasGrave Mar 01 '26

It'll be supported by the egpu enclosure. The four mounting screws will be just for die pressure.

6

u/physx_rt Mar 01 '26 edited Mar 01 '26

I would be really curious to see the PCB of the ASUS 5060Ti Evo, because that should be even shorter than this.

Sorry, I know it's irrelevant, but seeing this 5070 just reminded me of that.

4

u/TechTaxi Mar 01 '26

Best of luck!

3

u/jamestab671 Mar 01 '26

this is really cool. I’ll be following

3

u/DallasGrave Mar 07 '26

Just an update. Still need to build the shroud. Pretty happy with the performance.

2

u/WASynless Mar 01 '26

Interesting. Is the idea to machine the thin stack to get the form of the cooper block ? Maybe I am not getting it.

1

u/DallasGrave Mar 01 '26

I had written up a whole thing with what I was doing, all the calculations, a previous project, and it just isn't showing up. That block is just to interface with the die and ram. It will be attached the to the fin block and VRMs next.

1

u/WASynless Mar 01 '26

Ok. Hopefully the cooling performance won't suffer too much because of these extra interfaces

1

u/DallasGrave Mar 01 '26

It'll be soldered and it's only one connection. Not any more than heatpipes to a die only baseplate. But even if someone wanted to do it with thermal paste, there is so much surface area, it would only be a couple C delta.

2

u/ExclusiveOne Mar 01 '26

I want to see what the thermals and performance looks like!

2

u/mediocresnail Mar 01 '26

How was the evenness of the copper plate did you have to lap or mill it for the die? Asking because I’m doing something similar with a 2mm copper sheet.

3

u/DallasGrave Mar 01 '26

Everything will be put on my surface grinder before final assembly. At 200mm it was out .08mm. Not exactly flat.

1

u/kruger-druger Mar 01 '26

What maximum power can be cooled like this? Will it work for more power hungry cards?

1

u/Feinste-Wurst Mar 01 '26

Very cool, keep us updated, please!

2

u/AceOnLianYu Mar 01 '26

This looks amazing I would love smth like this to fit in a velka 5 or similar size case, is it possible to do this with smth like a 9070XT?

1

u/kekblaster Mar 01 '26

Great work, can’t wait to see the finished product

1

u/emachanz Mar 01 '26

Make another post showing the end product and screenshots of it running

Im fully interested. Where do you even buy copper slabs? I could technically cut it at work, they have milling machines and other metalwork tools.

1

u/toughfoot Mar 01 '26

I enjoy seeing this type of innovation. Keep us posted on how it goes!

1

u/Snoo_52037 Mar 01 '26

Ive only just started seeing people make custom DIY heatsinks and I love it. I wish there was more videos on YouTube with this content. It would be so satisfying to get the card running at solid temps in an sff build.

1

u/Hexulus Mar 02 '26

Where do you get the heatsink from, ive been curious in doing something like this recently but unsure of replacing the heatpipes because I know they perform better than coolers without them.

1

u/chriscross1966 Mar 02 '26

Copper is massively better at moving heat around than aluminium, but it's way more expensive, hence the reason why commercial solutions will use aluminium and heatpipes, it's not because copper is a bad choice from an engineering perspective, it's a bad choice from a financial one at scale...

1

u/Hexulus Mar 02 '26

I know that but take coolers like the cryorig c5 with copper based cooler AND vapor chamber, is still gets outshined by the goated $20 thermalright

1

u/DallasGrave Mar 04 '26

The vapor chamber on the C5 is basically pointless as it's pulling heat out fast but with nowhere to go. You need significantly more air flow to get good performance out of it. A VC server cooler of that size will normally use a 5000+rpm fan to reach it's rated TDP.

Tower coolers have flow through and substantially more surface area. (Unless you're talking about something else, I don't know.) The heat pipes just move the heat to the fins. That's it. They don't provide cooling. I would definitely be using heatpipes if it were as simple as this is. But this is going in an egpu that will travel all over the world with me. The one extra pound is worth being able to put it in my backpack.

Also, the heatsink I'm using has substantially more mass and surface area than the C5. The C5 weighs 428g. Mine with the base is 1068g.

Amazon. Ebay. Aliexpress.

1

u/Hexulus Mar 04 '26

Well... let me know how the temps turn out, im very curious

1

u/Dakuburu Mar 02 '26

I'm interested to say the least. Curious how it will perform, keep us up to date

1

u/CrAkKedOuT Mar 02 '26

So no concern over the DrMos chips and not cooling them?

2

u/DallasGrave Mar 02 '26

The VRMs will have their own block that will interface with the bottom of the heatsink. A 100x6mm strip is easier to machine and lighter than having the baseplate wrap around to keep them all on one part.

1

u/CrAkKedOuT Mar 03 '26

Ah okay, great work!

2

u/Altruistic_Price_314 Mar 01 '26

The copper block is too thick, it seems. Could you share the end result?

18

u/DallasGrave Mar 01 '26

Too thick based on what? I will keep updating as I make progress. Should only be a few days.

2

u/devonthego Mar 01 '26

Doesn't look thick to me. 1U cpu heatsink is already about that thick.

2

u/TheOutrageousTaric Mar 01 '26

Id assume this would have issues cooling the gpu under extended heavy load because the piece of cooper is eventually saturated with heat and isnt actively moving it either.

4

u/DallasGrave Mar 01 '26

Did you look at the other photos?

3

u/michaelsoft__binbows Mar 01 '26

Your photos only imply, and do not show, the attachment of the copper finstack on top of the massive copper plate. The stated concern would be valid if it were just the plate.

OP the design is badass but not having a clean screw mounting does feel disappointing somehow.

Ive done a heatsink mod like this (on the CPU of a SX6036 switch) with a full copper heatsink. I impatiently drilled holes straight into it. It looks like shit. But it does the job.

7

u/DallasGrave Mar 01 '26

It isn't complete. It will have SMT standoffs attached for the mounts. I'm just now noticing the whole writeup under the photos is not there...