Mellanox ConnectX CX-4 / CX-6 Active Cooler

This is going to be a very niche model. I will be stoked to get one download.

On the other hand, it would have saved me at least a dozen hours if I didn't have to make this from scratch, so… enjoy.

I'm using this on both CX4 and CX6 cards. They run well over 70 degrees with just passive cooling in a tower case, but with this contraption on and fan at 30% (which makes it inaudible) my CX4 is at 56 degrees. The CX6 is less efficient and doesn't really bring new tricks to the table wile being significantly more expensive on the 2nd-hand market, so get a CX4 if you have the choice. They both have current driver support from the Mellanox repo with VFs and all, just “sudo apt install doca-all”.

Design goals:

• Make the cards run within thermal specs in a desktop case.
• Do not require more than 1 slot width. Technically you shouldn't have anything longer than HL on BOTH sides of the card so the fan can pull in air, but that shouldn't be a big ask.
• Be silent. Silent-ish. 

Note: I am using the cards with copper DACs. You might very well overheat things if you plug in a 10km 100G QSFP28 module. Even short-range ones will get very hot. 

Note 2: If your fan fails, you'll want to know and shut the system down immediately. Monitor the card's temps from a script (mget_temp), set up something through IPMI, whatever. In order to force air over the entire length of the heatsink, the cooler covers the whole thing and it will turn into an extremely effective heat trap without the fan running.

With that said, you'll need:

• Delta KFB0612HAFDB frameless centrifugal fan. Mouser and Digikey regularly stock these for around $12 in singles. 
• A way to connect the fan to your motherboard: the fan comes with 4 wires but no connector. Ideally you'd get the 4-pin Molex 2510 housing, the matching pins, and a crimping tool (e.g. Engineer PA-09) but you can also get creative.
• Three M2x2mm heat-set inserts to help affix the fan's arms to the base. I got mine from an assortment set on amazon, product code B0C2HGNYLX. (Lots of M2 inserts out there, yet couldn't find any that's only 2mm long except these.)
• 3 of: M2x4 screws to for the fan arms. E.g.  McMaster 92095A452.
• 4 of: M2x5 to M2x8 thread-forming screws, ideally for use with plastic. E.g. McMaster 99397A185.

I printed most of my coolers from PC for heat resistance and strength, but I have one of the first working prototypes from 6 months ago made from PETG that's still doing fine, so I guess anything PETG or better will do.

You'll be attaching the fan to the inside of the arms on the base through the fan's blades:
 

This is probably more annoying than it should be. Magnetizing the screwdriver helps a lot. Using a soft threadlocker on the screwdriver helps even more.

The base slides onto the card, grabbing the PCB's top edge and the heatsink's bottom. This is a tight fit on purpose.

Othar than that, assembly should be straightforward.