Heatsink contact

[jm_bmw]

Hi everyone,

 

I lapped my NH-D15 over a year ago. During the procedure I noticed how the IHS was concave and the heatsink convex. I decided to stop on the heatsink once I realized the sides were taking too long to come off and noticed the 2 mounting points there... that would probably clamp it down were I didn't sand (seems like it) this reduced 2~3C. I was "ok" with the results and never worried about it until recently cleaning for a repaste.

 

It seems the sides opposed to the mount points are not touching very well... now I am wondering if I should attemp to finish sanding the heatsink all the way down?

[Skiiwee29]

I would say no. You need to keep lapping the heatsink as you seem to have good pressure in the middle, but it lacks on the sides as evident by the gobs of paste there compared to the center area. 

[Cyracus]

I would lap until they're both level with even contact. If it's taking too long use a lower grit. Finish at 400-600 grit (something about micro scratches=increased surface area or something, didn't finish the ted talk)

[jm_bmw]

I did it yesterday using 1200 grit and finished with 2000 (leftovers I had here). To be honest contact seems the same, its taking more of the IHS now but seems to have lost that good grip in the middle. Temps are better besides all that!

[Falkentyne]

On 8/5/2021 at 9:24 AM, jm_bmw said:

Hi everyone,

 

I lapped my 9900KF IHS and also the NH-D15 over a year ago. During the procedure I noticed how the IHS was concave and the heatsink convex. I decided to stop on the heatsink once I realized the sides were taking too long to come off and noticed the 2 mounting points there... that would probably clamp it down were I didn't sand (seems like it) this reduced 2~3C. I was "ok" with the results and never worried about it until recently cleaning for a repaste.

 

Pictures of the sanding proccess and compound spread attached. My question is, does this look like a good contact? it seems the sides opposed to the mount points are not touching very well... so I am wondering if I should attemp to finish sanding the heatsink all the way? -temps are still not great for stock 4.7ghz all cores 1.26vcore (1.20 w vdrop), it gets to 82-85C gaming cpu heavy tittles and 94-97C on CBR23 10min test, it doesn't lower the clocks though.

From these pictures, it looks like you need to continue sanding the heatsink as you haven't fully removed the convexity.

As for the CPU, you need to be careful.  It does look okay in your picture but I'm still not completely sure.

 

When doing work like this, what you *really* really need is some Extreme Low fujifilm prescale (lower pressure rating than Ultra Low), then you can test for contact pressure without constantly having to scrape up and reapply the thermal paste.

 

That being said, Innovation Cooling sells retail packaged Ultra Low prescale as part of their contact and analysis paper kit, but they've been out of stock for awhile.  They were in stock two months ago on their ebay store.

 

https://www.innovationcooling.com/product/ic-contact-test-analysis-kit/

https://www.ebay.com/itm/264362353892

 

I would definitely consider testing with Extreme Low, rather than IC's Ultra Low, because whenever you remove Z-height and thus mounting pressure, Ultra Low's 28-85 PSI rating starts being a bit too much to get a good reading from, and EL's 7-28 PSI starts looking more attractive.

You can VERY politely ask sensorprod, which is fujifilm's USA reseller (they usually deal with businesses who buy huge rolls for like $600 a pop), for a test sample.  Be very polite and be willing to explain to them what you are using it for, and mention that you would be willing to send them your results for their own use (but you are a simple end user/gamer and aren't interested in professional analysis).  I've had three samples from them over the last three years (two Ultra Low prescale, one Extreme Low prescale).

 

https://www.sensorprod.com/samplerequest.php?Prescale

 

BTW I'm still not sure why you're doing all this sanding work on the IHS.  I delidded, applied LM and then re-sealed my 9900k, and all I did to the IHS was sand the undersides down about 0.2mm to compensate for the removal of the solder, and my core temp deltas dropped from 11C to 7C, and I never had any problems like this.  I even went with LM on the top of the IHS to NH-D15 which dropped temps a few C more than Kryonaut (total temp drop for LM on everything was about 12C).  Anyway in your case, finish with the heatsink, and then make sure the CPU IHS is fully flat.