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On my motorcycle, I have a voltage regulator similar to this one: voltage regulator image

Some times over long trips and especially in summer, it tends to get really hot even though it is located under the subframe, exposed to quite a lot of air flow.

Is it possible to modify its cooling fins by cutting groves perpendicular to the existing ones so that I increase the cooling effect? I understand that I risk damaging the transistor inside but I believe it is really visible how deep could one go without damaging it. Finally I plan on doing this on a milling machine but for the sake of it, could this be done with a hacksaw? EDIT: Also instead of grooves, could someone drill holes on the fins so as to increase the fins surface and heat dissipation?

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    As a first thought, cutting slots or drilling holes will reduce the fins mass and probably the fin surface area leading to reduced cooling. Finding a replacement heatsink with deeper fins and a larger surface area with a quality thermal transfer compound would be my suggestion.
    – Solar Mike
    Jul 18 '19 at 13:41
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    How hot is "really hot?" These type of electronic devices work perfectly well with the heat sink at 75C or even 100C. The internal components are typically specified as OK up to 125C. If you can touch the cooling fins without getting burned, it's not "really hot" yet!
    – alephzero
    Jul 18 '19 at 14:22
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One would expect that the fins are currently aligned with the airflow. Cutting holes or grooves perpendicular to the fins is not likely to improve the cooling by a large factor. Some turbulence can be expected by airflow over the holes or grooves, but it's likely to be offset by the lack of surface area caused by the removal of the material.

Consider instead to use thermal epoxy to attach additional heat sink material to the device, space permitting. Do not confuse thermal epoxy with thermal compound, as the former is an adhesive, while the latter is not. You may be able to find another heat sink with fins of similar spacing to salvage as additional surface area to the device.

I would suggest also providing a backup to the epoxy to provide retention if the epoxy releases its bond.

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  • On a computer cpu they use thermal compound, if thermal epoxy is better then why don't they use that?
    – Solar Mike
    Jul 18 '19 at 13:45
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    @SolarMike how to you upgrade a computer chip (or replace a failed one) if its stuck down with epoxy adhesive? On the other hand you don't need to ever replace an extension to a heat sink fin, and adhesive will fill up any geometric tolerances so you don't need high-torque nuts and bolts just to hold two bits of heatsink together with no tiny air gaps between them.
    – alephzero
    Jul 18 '19 at 14:26
  • @alephzero if it proves not to work well then being able to remove it and change the design may be useful. If it works fine then cleaning the thermal compound off and epoxying it permanently is easy. I would be looking at a larger heat sink in all 3 dimensions... Easy enouh to workout the improvement possible, heat sinks are rated in terms of power dissipated for a delta T for X area..
    – Solar Mike
    Jul 18 '19 at 14:29
  • You can't use thermal compound at all unless you make some "permanent" modifications to both heat sinks to clamp them tightly together. But this is all hypothetical, because the right thing to do is design the heat sink to give enough cooling. Most likely the makers already did that and the OP is worrying about nothing. As I said in another comment "really hot" means "if you touch it you burn your fingers" for this sort of device.
    – alephzero
    Jul 18 '19 at 14:35
  • @SolarMike "heat sinks are rated in terms of power dissipated for a delta T for X area" I know how heat sinks are rated, and that's a pretty garbled explanation. (I spent about 10 years of my life doing calculations on cooling jet engine turbine blades, which is a bit more complicated and demanding than cooling a simple electronic device like a voltage regulator).
    – alephzero
    Jul 18 '19 at 14:37
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Removing mass from the cooling fins will actually hurt the cooling ability of the cooling fins. There are three ways (I can think of) to help with the cooling of the fins:

  1. Increase the area and/or mass of the cooling fins. I think @fred_dot_u covers this in his answer.
  2. Increase the air flow going over the fins. This can be done by creating some small ducting or a redirect of the air to funnel it directly over the fins. If you have a wider mouth with a narrower body going over the fins, it will increase the speed of the air, which will help it cool better. This is a venturi effect, by forcing a given amount of air through an ever decreasing space. Something has to give, so the air will speed up as it goes through.
  3. Cooling them in some way other than with air. While a bit elaborate, you could build a small liquid cooler, which would attach directly to the fins (or even directly to the regulator itself) to provide extra cooling. Think of this solution like what you'd have on a liquid cooled computer solution. Water cools much better than air alone. In this solution, you'd be replacing the existing fins with more fins, which is akin to #2, but involves a bit more work.
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