- Heat Sinks and the Raspberry Pi 4
- Is the Maker Movement on the Decline?
- How the Latest RPi Could Have Scored a Perfect Zero
- The Problem(s) with Neopixels
- The Problem with Overclocking and the SPI Bus
- Nice Video of Last Summer's KC Maker Faire
- Python Cheat Sheets
- Benchmarking the New Raspberry Pi 2
- Power and the Single Pi
- The Problem with HATs
- The Problem with Relays
- Geekspace Gwinnett Pi Jam
I was participating in a webinar recently and one of the attendees said that people are putting heatsinks on the wrong components on the RPi4 board. In particular, he said the biggest mistake they made was putting heatsinks on the metal RF cover over the Wifi radio components (that grey rectangle in the upper left corner of the board). Is that a mistake? First of all, this cover is designed to manage the RFI signals radiating from the chips inside and is not thermally attached to them. So, placing a metal heatsink on it provides no cooling advantages. And second, placing a big hunk of metal on the RF cover could affect the tuning and/or gain of the antenna designed into the PCB just to its left. So, it makes a lot of sense not to use a heat sink here.
But this got me thinking about the other heat generating components on the board and what makes sense for them. Inside the POWERplate package we include three heatsinks. These are shown in the documentation attached to the CPU (large square), the SDRAM (medium rectangle), and the PCIe-USB3 bridge chip (small square). The CPU on the RPi4 can get seriously hot and is an obvious candidate for a heatsink. Thermal testing that we have performed supports this approach. The RAM chip to its right is a plastic BGA package without any thermal features. It's difficult to determine from the datasheet if this device can benefit from a heatsink. But a quick search on Digikey turned up a number of heatsinks for plastic BGAs so I think the RAM chip could benefit with having one attached.
The last heatsink is shown on top of the PCIe to USB 3.0 bridge chip. After doing some research on the use of heatsinks on plastic packages, I found that chips with large "thermal pads" on the bottom do not benefit from them. If you look at the copper traces under this bridge chip on the bottom of your RPi4, you will see a small square riddled with tiny holes - this is the heatsink. So it appears that the small heatsink included with POWERplate really doesn't provide any benefit.
In summary:
- Don't put a heatsink on the WiFi RF cover
- Do put a heatsink on the CPU
- Do put a heatsink on the RAM chip
- There's no benefit to putting a heatsink on the USB 3.0 bridge IC.
Very cool thank you for your time
Raspberrypi.org has a great article on thermal management and what all they've done to improve the power usage of the Pi4 with various firmware updates. It includes thermal images of both the Pi3B+ and the Pi4 with the different firmwares and the only thing that almost needs a heatsink is the SOC. All their testing was done with no heatsinks installed. But the thing that did the most good was standing the RasPi on it's side so that convection cooling on both sides of the board could occur. Sitting flat on the table running their synthetic test it would start CPU throttling at 177 seconds in. On it's edge it would throttle just slightly at over 400 seconds. At idle it ran 2°C cooler. The only other place that could use a little help (and it would have to be tiny, maybe 6mmx6mm like they use on stepper motor drivers) would be the power management chip but seeing as the MxL7704 has a max peak temp of 260C and a max thermal juntion temp of 125C you could boil water on it and still be in spec.
So fresh air is much more important than heatsinks.
On-line, I saw a thermal image of the pi4B which shows the hottest chips. Four chips get hot. The three mentioned: CPU,ram and bridge and one not mentioned. The small one in the bottom left corner by the usbc connector. I have a fanless metal case from Amazon that has large cooling pillars to these four chips.
It runs 10C cooler than my original fanless case as it has larger surface area on the pillars and an increased surface area (via textured surface) on the case externally. ( Miuzie brand)