Attaching heat sinks - glue?

Hi,

I'm putting my Pololu Stepper Drivers to my RAMPS electronics. My kit came with double sided sticky pads to attach the heatsink onto the chips. But it doesn’t stick very well and I'm looking for an alternative.
Is there some 'heat sink' glue or similar that people use??

Thanks

Pete

I used this with success, you only need to put a really tiny pinhead sized droplet of it, and let dry a few hours.

[export.farnell.com]

The only drawback is that it's difficult to mix only the little quantity needed for a few heatsinks - you might waste some.

---

Most of my technical comments should be correct, but is THIS one ?
Anyway, as a rule of thumb, always double check what people write.

I've used superglue, it works quite well. It may even transfer heat better than the foam stickies since the interface is so thin. You could also mix up some epoxy with heatsink compound, about a 50-50 ratio.

---

Help improve the RepRap wiki! Just click "Edit" in the top-right corner of the page and start typing. Anyone can edit the wiki!

almost any glue, as long as it is thin should be okay. Remember that the heat you are able to dump through the top of an epoxy chip is pretty small. The added thermal resistance of a thin layer of almost any glue is going to be pretty minimal compared to the epoxy. This isn't like a CPU where you are dumping 100W. This is on the order of single watts.

If your board isn't mounted so the plane of the board is vertically oriented, just use thermal compound. By itself it should provide a modicum of adhesion for such tiny heat sinks. The benefit is that it DOES have a decent thermal transfer coefficient, unlike many traditional "adhesives".

When using superglue, the heatsinks fell off here after a few days. Standard superglue is rated to about 70 °C, A4983/A4988's thermal protection kicks in at 165 °C.

What I now use is screw locking glue ("Loctite"). Rated for 250 °C, hardens within a minute and even allows to remove the heatsink with moderate force, if needed. The only drawback is, it doesn't harden at room temperature, because the glueing surface is so small. Heating is very simple, though, just attach a motor and let it do a few movements.

---

Generation 7 Electronics	Teacup Firmware	RepRap DIY

Since the color designates the holding strength, what colored loctite are you using?

NewPerfection Wrote:
-------------------------------------------------------
> I've used superglue, it works quite well. It may
> even transfer heat better than the foam stickies
> since the interface is so thin. You could also
> mix up some epoxy with heatsink compound, about a
> 50-50 ratio.


You're doing it wrong ;-)
[www.arcticsilver.com]
[www.arcticsilver.com]

Edited 1 time(s). Last edit at 09/07/2012 07:17PM by Annirak.

Annirak Wrote:
-------------------------------------------------------
> You're doing it wrong ;-)
> [www.arcticsilver.com]
> adhesive.htm
> [www.arcticsilver.com]
> _adhesive.htm

Oh, I know that stuff exists. Most people don't have thermal adhesive, but more likely have both epoxy and thermal compound. I'm a cheapskate

---

Help improve the RepRap wiki! Just click "Edit" in the top-right corner of the page and start typing. Anyone can edit the wiki!

Quote

Since the color designates the holding strength, what colored loctite are you using?

The medium strength.

And don't forget to press the heatsink on until it stops swimming. Getting the glue layer as thin as possible is important.

---

Generation 7 Electronics	Teacup Firmware	RepRap DIY

NewPerfection Wrote:
-------------------------------------------------------
>
> Oh, I know that stuff exists. Most people don't
> have thermal adhesive, but more likely have both
> epoxy and thermal compound. I'm a cheapskate

That's fair, but the stuff isn't exactly expensive: about $13.

My criterion for this is that if enough thermal adhesive to mount all your stepper drivers with heatsinks costs less than replacing one, it's worthwhile. After all, what happens if your epoxy+thermal compound fails?

I bought a 60g tube of thermal adhesive from ebay for $2, it works wonderfully.

---

--

Charles S.
Software Engineer
Prusa Mendel I2, RAMPS 1.4, Marlin 1.0 R2, Pronterface, Slic3r

so... can I just mix thermal paste with crazy glue for a vertical mount or will it fall off ? and its half / half ?

Thermal Glue is the best option.

I used Arctic Cooling G-1. [www.arctic.ac]

It needs some time for the procedure but it worth it. It costs 7.5€ in Greece and it has enough glue for dozens of heat sinks.
The adhesives are contained in six containers, (three pairs), so you can use the one pair and give the other two to friends.

Quote

Thermal Glue is the best option.

... if you prefer marketing speech, yes. Anaerobic glue ("Loctite") works just as fine.

---

Generation 7 Electronics	Teacup Firmware	RepRap DIY

I been using superglue with heatsink long time ago, I would like to say it depends on how well you glue it, If you can press it well and make sure no dust in between and the surface is flat. you can get a good heat transfer.

I had tested to measure a 10 watt led (http://ac-rc.com/images/original_size/LED/SMD_10W_20000K.jpg) glued to aluminium plate.
the temperature difference between LED's aluminum base and aluminium plate is small/almost same value. The temperature is measured via Pro'sKit multimeters.

+1 for superglue here, if only because I always have some around, whereas heatsink glue I lose or it lives in a long lost esoteric-glue-drawer.

Traumflug Wrote:
-------------------------------------------------------
> ... if you prefer marketing speech, yes. Anaerobic
> glue ("Loctite") works just as fine.

I suppose that depends on what you mean by "just as fine."

Loctite 382 has a thermal conductivity of 0.1W/(mK).
Assuming a bond thickness of 0.05mm, and a bond area of 5x5mm (the area of the A4988) that gives a thermal resistance of 20 Kelvin/Watt.

Loctite 3875 thermal adhesive has a thermal conductivity of 1.75W/(mK)
Assuming a bond thickness of 0.05mm, and a bond area of 5x5mm (the area of the A4988) that gives a thermal resistance of 1.143 Kelvin/Watt.

Arctic Silver Premium Silver Thermal Adhesive (ASTA) has a thermal conductivity of 7.5W/(mK).
Assuming the same 0.05mm bond thickness and 5x5mm bond area, that gives a thermal resistance of 0.2667 Kelvin/Watt

Assuming the A4988 is at a 45-degree point, with 2A max that means that each channel is at 0.707 * 2A, giving 1.414*2A = 2.828A total current. This is flowing through a 430mOhm high-side fet and a 430mOhm low-side fet, for a total power of 2.43W.

The junction temperature increase caused purely by the thermal interface material for each of these options is:
Loctite 382: 2.43W * 20 K/W = 48.6 K
Loctite 3875: 2.43W * 1.143 K/W = 2.78 K
ASTA: 2.43W * 2.667 K/W = 0.647 K

Even if you don't believe Arctic Silver's marketing of 7.5W/mK, you should believe Loctite 3875 at 1.75W/mK.

While the rest of the cooling solution is important too, I hope you can see why "Anaerobic glue ("Loctite") works just as fine." is a bit misleading.

A second, important point is the thermal tolerance of the glue itself: Loctite 382 drops to 50% bond strength at 90C and 25% at 120C.

A more important point, however, is that heatsinking of exposed pad QFN packages should NEVER be done on top of the package. The thermal resistance of a QFN package (θjc) is in the range of 20-40 K/W, while the thermal resistance to the exposed pad is on the order of 2 K/W. The thermal resistance of a single 0.635mm via, filled with SnCuAg (SAC) solder, is:
1 / ((((pi * ((0.000635 m)^2)) / (.00157 m)) * (60 W)) / (m kelvin)) = 20.6562309 kelvin / W
A pattern of 9 of them, which is standard, works out to 2.295 kelvin / W

So, if you use loctite 3875 on the opposite side of the board to mount a heatsink, the thermal resistance to the heatsink is 2 + 2.295 + 1.143 = 5.438 K/W. If you heatsink the top-side of the A4988 with Loctite 382, which is what I believe you to be advocating, you have a thermal resistance to the heatsink of (20 ~ 40) + 20 = 40~60 K/W.

Considering that the quoted thermal resistance of the A4988 on 4-layer PCB is 32 K/W, gluing a heatsink to the top of it with superglue might actually increase the thermal resistance.

Edited 2 time(s). Last edit at 01/22/2013 03:29AM by Annirak.

Oh, for reference, everything I've found on cyanoacrylates in general indicates that 0.1W/mK is normal for all "super glue" type adhesives.

Annirak Wrote:

> A more important point, however, is that
> heatsinking of exposed pad QFN packages should
> NEVER be done on top of the package.

Exactly! (see attached)

3M thermal tape works but prefer thermal glue. Hardens in about 4 hours.

JB Weld old school slow dry my fix all. JB Weld has steel shavings in it and fast drys with heat. works well on raidators in cars it can take the heat. it can also conduct elctricity by adding grafite.

Edited 3 time(s). Last edit at 05/19/2015 12:09PM by davelions.

Hi guys. so I was looking into that arctic stuff. I have a lot of heatsinks I need to install am not sure if the thermal paste is adhesive. do I also need to buy thermal glue? or is the paste alone an adhesive?

Putting heatsinks on top of those chips is hardly worth the bother, because the plastic casing conducts heat badly. The chips are designed to be cooled via the thermal tab underneath and thence via the PCB. So the best way to run them cooler is to buy driver modules with a 4-layer PCB, such as the T3P3 Ice Blue ones, or use a fan to blow air over the driver PCBs

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Since this thread was resurrected from more than two years ago...

As dc42 wrote, these tiny heatsinks are practically useless. The proper way to cool down the driver chips and the MOSFETs on the RAMPS (or whatever other printer controller electronics you may be using) is to add forced air flow i.e. a small 12V DC fan blowing cool air directly over the RAMPS.

See here: [reprap.org]

Edited 1 time(s). Last edit at 08/01/2015 07:13AM by AndrewBCN.