Intel’s engineers have published a new research paper that defines how integrated heat spreaders (IHS) should be built to optimise for high-power chips. The aim is to move away from monolithic IHSs, which are starting to reach their limit, and towards simpler modular pieces that can be assembled to make better and more adaptable designs.
Current HPC chips utilise a metal heat spreader that sits on top of the main die to distribute heat evenly while transferring it to the cooler above via some sort of thermal interface. As CPUs and GPUs grow larger with each passing generation, however, traditional IHS manufacturing using stamping can no longer create the intricate shapes required for multi-chip processors, especially those exceeding 7,000mm². Though advanced methods such as CNC machining can provide the desired precision, this comes at the expense of speed and cost.
Intel’s clever solution aims to avoid this complexity altogether by splitting the IHS into multiple smaller pieces produced in bulk using standard stamping methods, and these can be simply assembled into the desired shape. The pieces will likely vary depending on the target chip, split into a main flat plate which contacts the heatsink/cold plate, plus multiple stiffener frames.
The paper claims this design can reduce overall package warpage by around 30% and the void ratio of the thermal interface material (TIM) by 25%, all while improving coplanarity – a measure of how flat and even the surface is – by roughly 7%. In other words, these IHSs should allow better contact with the cooler and thus better heat transfer. As a result, complex processors made using advanced packaging technologies like Foveros should run cooler, which provides more headroom to push performance further.
Considering the understory’s push for 3D-stacking solutions and heterogeneous compute modules, the IHS will play an important role in the chip’s performance. Each additional chiplet adds more heat that requires disposing of, so heat spreaders need to transfer that heat faster without creating hotspots or compromising package rigidity.
The researchers also hinted at potential future applications, which include high-conductivity metal thermal materials and even liquid-cooled heatsink modules, to keep upcoming high-power accelerators under control.
However, Intel isn’t the only one looking for new cooling methods to manage the growing heat output of modern chips. For instance, package-integrated vapour chambers (VC-IHS) are also serious candidates to replace traditional IHSs, thanks to their improved lateral heat-spreading capability, which will be important on large dies. LiquidJet cooling and Microsoft etched liquid channels are also high-complexity alternatives that take advantage of liquid’s higher heat conductivity.
That said, one doesn’t negate the other, as each chip will likely be coupled with just the right IHS/cooling system. When building massive compute and AI data centres, there is no room for wasteful designs; each part needs to be precisely made to complete its job – no more, no less.
