I am currently pondering modifying my laptop's heatsink and am curious whether I stand to gain any benefit at all. The CPU and GPU (similar heatsink design) reach high temperatures (90°C +) under load and the exhaust air is warm, but far from hot. So far, I have tried several thermal compounds and did some experiments regarding the way the heatsinks are attached to CPU / GPU. Unfortunately, the exhaust air is still not hot which leads me to believe that the heatsink design could be improved.
For context: the laptop uses a usual heatsink design, where a copper plate sits on top of the CPU / GPU. This copper plate is connected to a few heatpipes which lead to the cooling fins. The heatpipes are mostly round and the fins as well as the plate are flat / rectangular. Right now, the heatpipes seem to be fixed to the fins and the plate on individual spots, what looks like spot-welding.
The current design looks something like this (plate is green, heatpipe is blue, spots with connection are black):
UPDATE: I have taken the laptop apart and taken a picture of the actual heatsink, it looks like this (green arrows show where there is some kind of connection). I did use compressed air to clean the space between the individual fins afterwards.
My reasoning is that all of the thermal conductance is achieved via those small dots where the heatpipes are connected to the other parts. As thermal conductivity relies on surface area, I was thinking about filling in the gaps to the side of the heatpipes. Hopefully, by doing so the heatsink is able to transfer heat more efficiently, leading to lower temperatures.
Unfortunately, there are very few materials or ideas that seem suitable. Under normal circumstances (e.g. heatsink application) I would rely on thermal paste - but this can't be used here as it requires pressure. While searching for some kind of epoxy or glue that is thermally conductive, I came up empty.
My best idea right now is to use Indium (can be bought easily, melts at a reasonably low temperature) for the gaps. However, as handling of molten metal (at ~156°C) is tricky, I would love to know whether my idea has any merit.
A draft of my idea is as follows:
Where green is the plate / fins, blue are the heatpipes and yellow (on the right side) are the filled in gaps.
Thank you very much for any insights or hints! (and sorry for probably mixing several terms, like conductivity and conductance)
UPDATE: I have since taken apart the laptop and tried to fill the gaps with solder. Neither Indium (melts at ~ 156°C) nor regular solder would work, as both did harden as expected but could easily be pushed off with a Q-tip. My assumption was that some kind of material on top of the surface is causing the solder to not stick - however, even when using a metal brush with a electric drill, I was not able to make the solder stick (neither on the aluminum nor the copper part). This might be due to the inidividual parts not being heated to the melting point of the solder, but trying to heating them with the soldering iron did not even make a sensible difference. Additionally, I am too careful to heat the complete assembly up all the way to the melting point of solder, if I risk that the few existing connections might break while doing so.
In the end, I did sand down my CPU's IHS to make it even flatter and have accepted that this seems to be the limit that I can hope to achieve with this device.
Mixing some kind of adhesive / glue with thermally conductive particles might be an option but this was an avenue that I did not pursue further due to lack of experience with this process.