Thermal Paste vs thermal adhesive tested?

[dirthurts]

Hi guys,

So, I'm working on building a Pi zero as a small display with an ecology simulation running on it, and I want to keep it cool to prolong it's life.
I know that thermal paste is better than a pad to transfer heat, but how much?
I was looking for tests/benchmarks, and it would seem that no one has ever done this, that I can find.
Does anyone have any numbers that show how much of an improvement there actually is? Otherwise, I don't have enough data to justify a permanent bonded sink, but I would like the best passive cooling possible.

Thanks in advance!

[mrbwa1]

@dirthurts The general problem with thermal "pads" is that most cheaply available ones are basically just heat tolerant double-sided sticky rather than true heat transfer compounds.

Out of curiosity, have you tested your setup to see what kind of heat it generates bare? Usually Pis are okay unless they are really pushed hard in a completely closed up case. A bit of airflow is almost always sufficient to keep the die at reasonable temps. I haven't had temp issues with the Pi 1/2 type chips, so I would imagine a Pi 0 would be okay with a little airflow. (The Pi3 does seem to like to get quite hot though)

[dirthurts]

Thanks for the reply.

I've not tested it yet to see the temps as the program I'll be running isn't finished, but it will be running at least 8 hours a day, so I thought over time it could really build up. It will be mounted underneath a screen and I'm not 100% sure what the enclosure will be like, but it will likely be wooden and steel with little ventilation (I guess I could add a fan pretty easily).

I've had it (seemingly) throttle when playing SNES games in the past while testing, but it was only once so it could have been a simple coding issue.

[mrbwa1]

@dirthurts In most of my testing, I generally can't get a Pi to throttle unless it's trying to run Dreamcast or PSP games. I haven't tried a Pi 0 though, so can't say for sure. The Pi2 running at 1000MHz never really got over 60C. The Pi3 does run hotter depending on the platform though (running at 1350MHz OC).

Screens can put off some heat, so even a couple cross-ventilation holes would probably be a good idea. A fan probably isn't needed, but if it does get too hat for your taste, even a small amount of airflow does wonders.

SNES on the Pi 0/1 can have issues with SuperFX games. It's not thermal throttling but just a performance issue (may be better with newer releases of the emulators though).

My personal opinion is that people are probably overly worried about heat and and up adding more heat by using cheap heatsink kits with the thermal pads. Modern tablets and phones don't really have any cooling and survive for years (they sometimes have a heat spreader inside to keep from getting a really hot spot though (usually with a tiny amount of thermal paste).

[dirthurts]

@mrbwa1 I think I agree with what you're saying. It's probably a better idea to invest in better cooling for the display unit than the pi itself. I'll give it a go and see what happens.

I am still a bit curious as to the difference in performance between paste and a pad, as it seems no one has covered it before, but it's not likely a factor in this particular setup.

I think we're moving to the pi 3 anyway so we can use them in more activities later on, so I'll run some real world tests on mine and see what the temps do.

[caver01]

@dirthurts Your original post title asks about thermal paste vs. thermal adhesive. To me, these are very similar products--both are thick liquids. The paste typically remains liquid (though very sticky) and the adhesive goes on smooth but later hardens like a glue. Some of the answers above pertain to self-adhesive double-stick pads which is a third method. In another thread we had a mix of anecdotal contributions from folks with different solutions. What I took away from that discussion was:

1. Double-stick pads (tape?) is hit or miss. A quality product might work fine, but if you don't know what you are getting, you could actually be insulating instead, and that could make your heat problem worse.

2. CPU thermal compound/paste is probably the best interface between a CPU and sink. (i.e. Arctic Silver 5). Apply to clean parts, and use very sparingly. Friction and suction keep it held in place, but you can still knock or twist it off. It's better if something holds it down (but I have never had a problem with my heatsink on a Pi3 mounted upside-down).

3. Thermal adhesive may work fine, even if it isn't specifically designed nor documented by the manufacturer for CPUs. It has the advantage of being more secure.

4. Interface being equal, results vary depending on your heatsink. Most people reported that their Pi2 saw little improvement even with good sink+compound. The Pi3 runs hotter, and I noticed IMMEDIATE and SIGNIFICANT benefit from having a small heatsink attached. Mine was throttling after being on for extended periods, and always whenever I opened a newer game. Adding a small sink with thermal paste has completely eliminated my throttling.

5. Fans and giant sinks can take the cooling even further. (I use a small sink, and no fan on my Pi3 and I am very pleased).

I would say that for a Pi3, you definitely will benefit from even the smallest of heat sinks if properly attached (I would avoid the self-adhesive gamble).