Thermal paste & pad comparison (MX4, Graphite thermal pads from IC and Panasonic)

Flashlight Modding and DIY Parts
1

I bought some Panasonic Graphite Thermal pad material from Arrow this week. I’ve had good experience with IC Graphite for LED testing, since they are reusable and require no cleaning unlike traditional thermal pastes.

Panasonic datasheet: https://industrial.panasonic.com/cdbs/www-data/pdf/AYA0000/AYA0000C50.pdf

Visually the Panasonic PGS is identical to the IC Graphite. The price however, is much lower per area. While the IC Graphite comes in 40x40mm pieces and costs $13 (15 € here), the Panasonic pad is 120x60mm with the same price tag of $13 with free DHL shipping from Arrow. It only took 4 days to arrive from the US. Currently the sheets are not in stock though.

Both sheets are 0.2mm thick, even though I’ve seen some sites specify the IC graphite as 0.1mm.

As I just got the Panasonic today, for this first test I just wanted to see if it performs as well as the IC one.

Testing was done on an Intel CPU heatsink with its fan run on 12V at all times. LED was the Lumileds Luxeon V with Led4Power copper MCPCB. The MCPCB was secured with screws.

I first turned the LED on at 1A and measured it immediately for output and other photometric data for a baseline. Then I cranked the current up to 6A for about 1.5 minutes and took measurements at a steady interval.

After testing it was obvious that the copper-copper contact between the MCPCB and the heatsink was very good, probably too good for this test. Even without any thermal interface material, the performance was almost on par with the TIMs. The surfaces are very even. The CPU heatsink has almost a mirror like finish.

However, it’s clear from the temperature graphs, that the temperature shoots up much more rapidly without any TIM. The temperature rises to 38-40°C with all the methods. All the TIMs perform identically. Output wasn’t significantly lower without TIM, but the lower forward voltage indicates worse heat path. If taken into account the higher power (considering the higher Vf) with the tests ran using TIM, the output differences are pretty much non-existent (less than a percent). Without a heatsink, the LED overheats almost immediately.

Temperature graphs measured from the MCPCB.

IC Graphite

Panasonic PGS Graphite

Arctic MX4 thermal paste

No thermal interface material (direct cu-cu contact)

No heatsink at all, just the MCPCB dangling in the air, reaches over 100°C in about 10 seconds.

There was practically no differences in tint (CCT and duv) either. The no TIM method had a tiniest bit of higher deltaCCT when comparing 1A and 6A.

No TIM: 4060K at 1A -> 4255K at 6A after 1.5 min
Panasonic graphite pad: 4055K at 1A -> 4222K at 6A after 1.5 min
IC graphite: 4066K at 1A -> 4240K at 6A after 1.5 minute
MX4 paste: 4051K at 1A -> 4226K at 6A after 1.5 min

I’ll continue later with some worse mounting methods and more uneven and scratched heatsinks. But from this, it’s clear that if there’s enough clamping power and the surfaces are even, you can get by with no TIM at all - at least with wattages around 20W.

2

I’d also like to test the Thermal Grizzly Carbonaut, but it’s not available yet.

It differs from the IC and Panasonic in that it’s very flexible, fabric like, while the IC is very brittle resembling paper.

3

Another round of testing with an uneven Chinese heatsink and using low and high clamping power. Loose connection was with the screws just holding the MCPCB put, but not really clamping it down. Tight was with the little screws as tight as was practical.

This time the results were more interesting with the No TIM being horrible. The normal thermal paste performed almost identically with low and high clamping power while the graphite pads shined when the MCPCB was clamped on tight. In that case they were actually outperforming the paste. This could be due to their ability to conduct heat very efficiently in the lateral direction (i.e. the small hotspot generated by the emitter was spread effectively to a larger area).

Ambient temperature was 27°C. Temperature number on the graphs are delta over ambient. I measured both the MCPCB and emitter separately.

No TIM with loose clamping. LED is red line, MCPCB is blue.

No TIM with tight clamping

Panasonic PGS graphite pad with loose clamping

Panasonic PGS graphite pad with tight clamping

IC Graphite pad, loose clamping

IC Graphite pad, tight clamping

MX4 thermal paste, loose clamping

MX4 thermal paste, tight clamping

Output comparison with a 1A output for reference. First with loose clamping. MX4 is marginally better than the pads.

Identical results for the TIMs with the screws tightened

Similar story with the forward voltage. Higher heat equals lower voltage.

Loose clamping

Tight clamping

Conclusion: With less than optimal mating surfaces, if there’s not a lot of clamping power available, use thermal paste (although in practice graphite pads are similar in performance). If secure mounting with lots of clamping power is available, graphite pads are at least as good or even a bit better than paste. No TIM at all is significantly worse in both cases with an uneven heatsink (what a surprise).

4

Thanks for the comprehensive testing and the valuable data! I’ve planning to use such TIM pads for lights that are modded frequently to skip the annoying procedure of removing and reapplying the paste every time.

Could you maybe also test liquid metal thermal paste?

It might make sense to use an Osram White flat for testing.

5

Really have to keep Gallium away from Aluminum though, so in the right circumstance it’s useable but not in all cases. I’ve used it in special lights with good results, not sure really without all the fancy measuring equipment if it’s better or worse than just using a good paste. These days when I have a copper to copper interface I usually reflow the MCPCB to the pill…

6

Reflowing can be better actually if you use pure Indium as solder, but it makes repositioning/replacing the LED very labourous.

7

Thanks for the data, very interesting tests you have carried out!

8

One thing to note here is that Arctic MX4 is a very common thermal paste, but definitely not the best one on the market in terms of pure performance. Testing by pc reviewers has revealed that Thermal Grizzly Kryonaut is currently the highest performing one. When used with CPUs is typically achieves around 3°C less compared to cheap pastes. This might be important for someone trying to overdrive an Osram White Flat or similar.

9

Always important to cite this trailblazing article in the field of thermal paste comparisons:

http://www.dansdata.com/goop.htm

10

Here’s something a bit more recent:

TL;DR: it doesn’t matter. MX-4 is still the best for the price.

11

I so wish these comparison included some budget pastes…GD900 gets quite a few recommendations but it’s hard to find it in serious tests.

12

That's a great article!

Like I already said, a good paste might be interesting when using LEDs with the very highest power densities like the Osram White Flat. Otherwise, no. I've been using the same tube of Arctic Silver 5 for the past 10 years.

These Panasonic thermal pads here are really a much bigger change. No more cleaning!

13

Good info. I just ran out of my AS 5…

14

The problem with these high performance pastes, from my experience,is they dry out after 6-12months and then become obviously worse than even the cheap pastes.

All those tests show short term performance with fresh paste, but I'd really like to find good paste with long term performance, the one that doesn't have to be replaced with fresh paste each xx months.

15

I remember a certain forum recommending gelid gc extreme for that.

16

Do have any data/links on this? Which do you consider a cheap paste and which not?

17

I noticed MX-2 and AS5 become dry several months after application in both flashlight and PC. Flashlight OTP triggered at lower than usual body temperature - one of advantages of NTC on LED MCPCB, driver correctly detected OTP threshold level (65C), but because paste was dry body temperature was lower than it should've been.

PC - CPU lags etc., after inspecting paste was also completely dry, this does not happen with generic lower thermal conductivity oil based pastes.

18

Been googling past few days and Gelid truely wins in almost every review plus it won’t dry out in few months due to viscosity. Looks like i found the winner…for now
But a better option is Phobya 2, thermal epoxy though :wink:

19

Does anyone have experience with MasterGel Maker Nano-High? It’s been favorably reviewed, e.g. Cooler Master MasterGel Maker Nano Review | eTeknix and apparently doesn’t tend to dry up as quickly as other pastes.

20

I don’t know how this works, but there are many good rumors about Noctua NT-H2 thermal grease