Parag
Posts: 7
Joined: Sat May 08, 2021 5:14 am

Heat sink requirement for raspberry compute module 4

Tue May 11, 2021 12:31 pm

We are making our own carrier board with raspberry pi 4 compute module. We are enclosing it in a plastic box. The ambient temperature can go up to a 55 C and internal temperature goes up to 75 C.

How much heat can be dissipated by the SOC package assuming that the SOC is operated at the highest frequency with all its peripherals also operated at its highest frequency?

Would heat sink require in this case ? Where can the heat sink be source from?

aBUGSworstnightmare
Posts: 3898
Joined: Tue Jun 30, 2015 1:35 pm

Re: Heat sink requirement for raspberry compute module 4

Tue May 11, 2021 4:37 pm

There is a search function on this forum which can be put to good use...

viewtopic.php?f=98&t=298810&p=1797688&h ... 4#p1797688
viewtopic.php?f=29&t=309977
viewtopic.php?f=98&t=301830

Only to name a few related to CM4 heatsink.

Parag
Posts: 7
Joined: Sat May 08, 2021 5:14 am

Re: Heat sink requirement for raspberry compute module 4

Wed May 12, 2021 8:35 am

Thank you for your answer.

Please give me reply on my below query also.

How much heat can be dissipated by the SOC package assuming that the SOC is operated at the highest frequency with all its peripherals also operated at its highest frequency?

StonedEdge
Posts: 95
Joined: Wed Oct 28, 2020 11:42 am

Re: Heat sink requirement for raspberry compute module 4

Wed May 12, 2021 9:07 am

Parag wrote:
Wed May 12, 2021 8:35 am
Thank you for your answer.

Please give me reply on my below query also.

How much heat can be dissipated by the SOC package assuming that the SOC is operated at the highest frequency with all its peripherals also operated at its highest frequency?
As per section 3.2 in the datasheet:

"The CM4 dissipates less power than the Raspberry Pi 4, Model B. The CM4 also contains less metal in the PCB and
connectors and so it has less passive heat sinking than the Raspberry Pi 4, Model B. Therefore despite it consuming less
power it may run warmer than the Raspberry Pi 4, Model B.

The BCM2711 will reduce the clock rate to try and keep its internal temperature below 85°C. So in high ambient
temperatures it is possible that the clock will also be automatically throttled back. If the BCM2711 is unable to lower its
internal clocks enough to bring the temperature down its case temperature will rise above 85°C. It is important that
thermal solution chosen keeps the ambient temperature for the other silcon devices on the CM4 within the operating
temperature range"

To give you an idea, we plan on using a pretty thin fan and a heatsink like this in our CM4 project. It has a decent amount of surface area and is quite thin (we plan to machine fins into it) but we still expect it to be ample to keep it cool when overclocking.

Image
Image

aBUGSworstnightmare
Posts: 3898
Joined: Tue Jun 30, 2015 1:35 pm

Re: Heat sink requirement for raspberry compute module 4

Wed May 12, 2021 10:05 am

StonedEdge wrote:
Wed May 12, 2021 9:07 am
Parag wrote:
Wed May 12, 2021 8:35 am
Thank you for your answer.

Please give me reply on my below query also.

How much heat can be dissipated by the SOC package assuming that the SOC is operated at the highest frequency with all its peripherals also operated at its highest frequency?
As per section 3.2 in the datasheet:

"The CM4 dissipates less power than the Raspberry Pi 4, Model B. The CM4 also contains less metal in the PCB and
connectors and so it has less passive heat sinking than the Raspberry Pi 4, Model B. Therefore despite it consuming less
power it may run warmer than the Raspberry Pi 4, Model B.

The BCM2711 will reduce the clock rate to try and keep its internal temperature below 85°C. So in high ambient
temperatures it is possible that the clock will also be automatically throttled back. If the BCM2711 is unable to lower its
internal clocks enough to bring the temperature down its case temperature will rise above 85°C. It is important that
thermal solution chosen keeps the ambient temperature for the other silcon devices on the CM4 within the operating
temperature range"

To give you an idea, we plan on using a pretty thin fan and a heatsink like this in our CM4 project. It has a decent amount of surface area and is quite thin (we plan to machine fins into it) but we still expect it to be ample to keep it cool when overclocking.

Image
Image
looks nice that solution. Will you use TIM to fill the gap (Thermal Interface Material)?
Maybe I should give it a try and mill my own eatsink as well...

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