Replacing Laptop Thermal Paste

My Lenovo Thinkpad T450s was experiencing high temperatures for quite a while so I finally decided to re-apply the thermal paste.

Choosing a thermal paste

I checked reviews for different brands. The important thing to consider is to use an electrically non-conductive paste so if the paste spills over the CPU die, it wouldn’t short-circuit any IC pins. Apparently one should also mind the production date. Based on what was available and price, I chose DeepCool Z5.

Applying the thermal paste

So I opened YouTube and watched a couple of videos for this procedure for my model of laptop.

An interesting question that rises here is the geometry of the applied paste. This video did a comparison and found out there is no practical difference between different geometries.

Here is the state of things once I opened up the heatsink

Then I cleaned the old paste using a piece of fabric and an antiseptic alcohol spray (a relic from the reign of COVID-19 😩)

Finally, I applied some paste in linear geometry. There was some excess paste on the tip of the Z5 syringe so I put it around the line. The right die is not thermally stressed but I also applied some on it anyway.

I put the heatsink back, slid it back and forth a bit so the paste would expand all over the die, then fixed the screws.

Stress testing

To test whether the procedure was done properly, I benchmarked the CPU using geekbench6 to put it under stress and recorded die temperatures before and after applying the paste.

Here is the fish-shell snippet to do this:

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while true;
    cat /sys/class/thermal/thermal_zone*/temp | paste -s -d ' ' | ts  '%s';
    sleep 1s;
end \
| tee before.csv

(and the same for after.csv)

Here is how I calculated the average temperature of core0:

awk '{ total += $2 } END { print total/(NR*1000) }' before.csv

which resulted in:

before: 85.5062 °C, after: 61.0385 °C

So a 24.46 °C drop, huh? Not bad 😀

Plotting CPU die temperatures

Then I plotted the temperature graphs of CPU die under geekbench6 load using feedgnuplot:

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paste before.csv after.csv \
    | awk -F ' ' '{print $2/1000,$7/1000}' \
    | feedgnuplot --lines \
        --set "ylabel 'CPU Temperature [°C]'" \
        --set "xlabel 'timestamp [sec]'" \
        --legend 0 "before" --legend 1 "after" \
        --set 'key bottom left' \
        --exit

Geekbench scores improved too:

Before: 1058 Single-Core Score, 1915 Multi-Core Score
After : 1075 Single-Core Score, 2027 Multi-Core Score

Conclusion

I’m happy with the results and wish I’d done it sooner.