So, I was thinking about this. We used to have naked CPU cores back in the past and one of the reasons why everyone started doing IHS (Integrated Heat Spreader) wasn’t really to spread heat as much as to protect the CPU core from chipping on the edges when mounting and dismounting CPU coolers and not placing it absolutely flush caused higher pressure on edges of CPU core, chipping it as a result. I remember my AMD Athlon XP 2400+ having edges chipped a bit after many mountings of CPU coolers. It was still working, but it looked a bit ugly and such chipping can possibly ruin it.
The main problem doing this are thermals. Ideal method of removing heat from CPU is having heatsink attached to it directly with highest heat conductive thermal compound in between.
With IHS, you’re essentially making a sandwich of materials and bonding compounds that are far from optimal. Sure, IHS can be copper which has excellent thermal conductivity, but bonding compounds usually aren’t. Even gallium used in liquid metal compounds has like over 10x lower heat conductivity than copper. And soldering IHS to CPU can cause the solder compound to crack in rare cases as it’s constantly expanding and shrinking as CPU is heating up and cooling down rather rapidly.
So, Intel started using regular thermal “bonding” compound even under the IHS where it’s contacting CPU. Sure they saved hundreds of thousands of dollars, but they also made CPU’s with absolutely atrocious thermals. This isn’t really an issue with low end CPU’s that barely get warm under load, but 12 or 16 core CPU can’t possibly work well.
I got this idea while looking at the other segment, GPU’s. GPU’s still have core die fully exposed. Partially because heatsinks always come pre-installed by manufacturer and partially, because they do a small trick that I think could be borrowed by Intel and AMD for CPU’s. Sort of proposal of 2 designs quickly mocked in Paint 3D…
This one is borrowed directly from graphic cards. GPU’s have been using metal guard shrouds like this for ages and what these do is prevent placement of heatsink at an angle that is too high which is what causes the edge chipping. And given we can make chips at 7nm, I’m pretty sure they can manufacture whole CPU’s in such way that CPU core and metal guard shroud are perfectly flush, meaning shroud and CPU would be perfectly leveled on the package substrate. Shouldn’t be a problem even for multicore designs like Ryzen or EPYC. They would have to tighten up tolerances, but in the end, it would actually end up being easier than having to perfectly solder 4 or more individual chips to the IHS on top.
This second example was actually my initial “proposed” design, but I later figured out there would be issues with such design, mostly in terms of material used if solid and bending issues if hollow. Also, thermal compound would get stuck into thin crevice between guard and CPU as well as issues where liquid metal would potentially get inside and no way of cleaning it out. Filling the crevice with some sort of epoxy would complicate expansion of metals and core and I don’t think it would be a good solution.
So, I think the first one would work better, be able to protect the naked CPU core and be easy to maintain in terms of cleaning thermal compound.
I think heading in this direction is a necessity because we are increasing cores with each CPU release and having them under several layers of suboptimal heat conductive materials is a really bad design decision as thermals are getting worse and worse with every CPU release. “Heat spreader” should be a copper base of the CPU heatsink or water block, not an extra layer of copper between two layers of thermal compound which is just terrible.
Having fully exposed CPU gives you best way of removing heat and metal guard would prevent chipping of CPU die. Probably not 100%, but enough to allow several re-mounts of CPU without any damage.
I really hope AMD and Intel will consider heading in this direction because CPU’s in general look pretty terrible these days in terms of thermals…