How to design heatsink and fan

[grlobe-trotter]

I've checked in on the fan listed on the Ashida BOM off and on for a while, and it hasn't been in stock. Because of this, I've started looking at other options for fans and I was hoping to get some guidance. What should I actually look for in a heatsink and fan for a portable Wii?

For the fan: I used "view similar" on Digikey and selected 5VDC, 3 CFM, and Tubeaxial. I assume voltage and CFM are the most important parameters to maintain. Is there any other piece I'm missing?

Regarding the heatsink: Is there a minimum heatsink footprint needed to properly dissipate heat from the trimmed Wii? I'm pretty much just trying to get one that matches the footprint of whatever fan I select.

Final question: I see a copper sheet being placed alongside the heatsinks and fans on portables. Where does that sit in the heat management? Is it necessary? Should it sit between the heatsink and and the fan?

These are the ones I'm looking at getting. I'm not building an Ashida, so I chose one that was a little smaller. The static pressure is lower, but I wasn't sure how much I really need to overcome...
Fan: MF25100V2-1000U-A99 Sunon Fans | Fans, Thermal Management | DigiKey
Heatsink: 625-25ABT4E Wakefield-Vette | Fans, Thermal Management | DigiKey

Links to any guides would be great. I'm kind of looking for some guiding principles so I can understand what these pieces need to accomplish. I'd like to settle on one so I can fit the dimensions of it into a 3D model.

 

[Stitches]

Depends on how compact you want to make the cooling solution. Most builds nowdays use some variation of a 35x35x10mm heatsink with a 35x35x10mm metal bodied blower fan. The metal body of the fan allows it to absorb and dissipate heat while blowing air through the heatsink. The heat from the CPU and GPU needs to be spread across the fan and the heatsink equally in order for the cooling to be efficient, so a 1-2mm copper plate is usually used in this case to create a unified cooling assembly. It's relatively important to ensure that the Wii doesn't get hot enough to warp your case or damage the fan, so the copper plate is very useful in this case. Note that you don't need the metal bodied fan, you can use any plastic one that fits in exchange for a small efficiency hit.

You'll need a thermal interface for this as well, mere press fitting isn't enough to transfer the heat effectively. If the heatsink you get doesn't come with a thermal pad stuck on, you can use a bit of regular PC thermal paste to connect the heatsink and fan to the plate, and then some blue 3M thermal pads to interface the Wii to the plate. Using pads for the Wii ensures that you can easily remove the mobo if needed. Personally I use thermal epoxy to bind the heatsinks and fans to the plates because it's permanent, and once set, the assembly is one rigid part and won't shift.

The Ashida deviates from this convention due to having a heap of extra space inside, and to make assembly easier. If you aren't making a giant case like the Ashida, the compact assembly is your tried and true option.