RPI 3b and 3b+ chips needing heat sinks.....

[tentoes1962]

Hello so I am going to prove my noob-ness by asking which chips on the pi 3b and 3b+ should have heat sinks applied?

I bought a set of two, red-anodised aluminum ones at Fry’s and assumed:
1) while advertised as “raspberry pi 3b” heatsinks, it did not specify which ic’s were supposed to be cooled, so I just applied them to the big CPU chip and the other, smaller square one on the same side as the CPU, thinking there wasn’t enough room on the other side’s big processor chip to allow clearance in some encapsulating plastic cases for the pi, and

2) that only 2 heat sinks were all that were required for the entire board.

I know that the metal-cased CPU of the pi4 and 3b+ need metal fins (and active cooling often), but how necessary are they for both ? And where should they be attached?

[HawaiianPi]

The only part that may benefit from cooling is the SoC, which I assume is what you called "the big CPU chip" (actually a System on Chip).

I have a 3B that is cooled by a quiet, low CFM fan alone (no heatsink). In my experience, a fan alone works much better than a small heatsink alone, especially if inside a case. And speaking of cases, most of my 3B and 3B+ computers are in Flirc Gen2 aluminum alloy cases, which act as a huge heatsink to keep them cool without the noise or additional power requirements of fans (and without coating the system with dust).

That may sound a bit contradictory, but what's important is to keep the Pi below throttling temperature for best performance, and the Flirc case does that without the disadvantages of fans, while also protecting my Pi3 computers (and it looks cool, too).

[alphanumeric]

I've only ever put a heatsink on the SOC. The other ones in those kits, IMHO are more for looks than actual cooling benefits. As far as I know putting them on isn't going to hurt anything. So far I've been fine with passive cooling.
That may end with my new Pi 4B though. Its hitting 74c with light use. My case has good ventilation and I have a large heatsink on the SOC. Going to try cooling it with a small fan.

[ProDigit]

A heatsink always helps, even for things like the pi zero.
On the 3B+, I ran a larger than common heatsink, but under load, the CPU would still hit 60C, the stock throttle temperature of the pi3B+.
So I installed a heat sink the size of the Pi, inside a case, equipped with an LCD screen, and now it only reaches 60C after 2 minutes of 100% CPU utilization. A situation that's not very common for me.

But metal cases that cool the CPU, are your best bet for keeping it under throttle temperatures, next to active cooling.

The tiny heat sinks only work in open cases.

[alphanumeric]

Just be aware than full coverage metal cases will more than likely negatively affect your WIFI performance.

[wildfire]

Just be aware than full coverage metal cases will more than likely negatively affect your WIFI performance.

I know this ^^ has been posted a few times but 3 of my Pi's are in metal cases:

1 x 3b+ in a Flirc
1 x 3b+ in an Argon one (which also has active cooling)
1 x 4b4 in a Flirc

And have never had any issues with WiFi or BT, as noted above though YMMV.

My other 4b4 is in a coupe case with fan shim but the Flirc case keeps the other cooler with an identical setup.

[ProDigit]

Just be aware than full coverage metal cases will more than likely negatively affect your WIFI performance.

Thanks for the headsup!
Thankfully my Pi3B+ is the only one in a metal case, and runs off a LAN cable;
the Zero W doesn't need that kind of cooling.