Alloy Enterprises was showing of some interesting cold plates at Hot Chips this year. SemiAccurate liked the devices but was even more impressed with how they are made.
Cold plates are nothing new, either traditional water blocks or Direct Liquid Cooling (DLC)/immersion cooling have been around forever. Given the massive gain in energy use per device of late, the blocks themselves have evolved from simple water pipes to crazy complex AI generated internal passageways. We are now in the age of microchannels, gyroids, and other triply periodic minimal surfaces. If you don’t know what the latter two are, take a peek at the cold plate below. It is for a GPU and do note the pathways in the top are not linear, there are repeated versions on lower layers, each offset from the one above.
Complex passages in a GPU cold plate
Also note the edges, both the device itself and the channels. See those little steps? Those are key to how Alloy makes their devices and it is what makes them interesting and manufacturable at scale. They call it Stack Forging and it uses diffusing bonding to take a literal stack of metal and turn them into a single solid block with reportedly no voids or gaps. The process is both simple and complex, but it works.
Note the terracing of the edges
Take a thin metal plate, in Alloy’s case there is one specific aluminum and one copper alloy they use, and laser cut it to the desired shape. Repeat until you have the full cold plate in a few dozen independent horizontal layers. Treat the surfaces in a proprietary way, line them up, and them smack them with a big hammer. That last part is only a partial exaggeration, you hit it hard with a heavy weight or press, hence the forging part of Stack Forging. If done right you end up with a solid block of metal devoid of voids, tortured phraseology intended.
A few Alloy cold plates in aluminum and copper
Depending on how you cut the layers, likely lasers, you can do some very interesting things. Microchannels? Capilary tubes? Weird impossible to machine tubes like the ones above? Not a problem. All of the above? If you want. Basically you can use the flow optimization tools that have become common to design a structure, then actually make it. That last part is a problem with traditional machining methods but not for Stack Forging.
So in the end, Alloy has the ability to make nearly arbitrary forms with a simple(-ish) process that looks like it can scale. 3D printing can achieve better results with smoother walls but good luck scaling that in an economically viable way. You can probably get most of the way there with Stack Forging by picking the tubes you need really smooth and keeping them in the Z-axis for laser cutting and other clever design side techniques, but again, this method scales. It looks like Alloy has come up with a very useful process.S|A
