Heat Sink adhesive??

RobotWorkshop · 2011-03-30 20:15

I have a Propeller USB protoboard where the 5V regulator is getting a bit warmer than I'd like. When I went through my spare Heat sink drawer I found some small .5"x.5" heat sinks that were normally held on with adhesive. I'd like to glue one of these to the top of the 5V regulator on the board to help keep it cool.

Anyone have suggestions as to what adhesives would work well and help move the heat to the heat sink??

Robert

PJAllen · 2011-03-30 20:20

There are special adhesives made just for this,
but the commonly available JB-Weld has "metal bits" in it.

Phil Pilgrim (PhiPi) · 2011-03-30 20:24

I've used JB Weld for this purpose, and it works great.

-Phil

RobotWorkshop · 2011-03-30 20:25

Thanks to both of you for the suggestion!!! I have some JB weld that I've used in other projects and didn't even think about using it for the heat sink. I'll be able to install it this evening so it should be ready for tomorrow.

Robert

RobotWorkshop · 2011-03-31 07:02

Worked out perfectly! Now I just need to find a source for more of the heatsinks I used. I'm thinking about adding them to my Propeller Professional Development Board too.

Ttailspin · 2011-03-31 07:15

Since You are using JB weld, You could embed strips of Aluminum flashing and have a very custom heat sink..
Or, You could always glue a Penny on top..

Franklin · 2011-03-31 08:44

http://www.arcticsilver.com/arctic_silver_thermal_adhesive.htm

Tracy Allen · 2011-03-31 11:21

Here is a site with empirical data on using pennies as heat sinks in various arrangements. They did try epoxy as an adhesive, but didn't say what brand, probably not JB weld specifically.

I did use a penny once with JB weld. In a pinch. I was installing equipment in Mongolia, and an soic-8 VR was getting hot due to a higher load than originally planned. I was afraid the hotel (if you can call it that) manager would come in and freak out about the heat cure acceleration going on above the table lamp. I wonder if the penny really helped. In any case, it came loose after some time and it is a miracle it didn't fall and short something out. The circuit kept working though. The thing about epoxy and smooth surfaces is that it does not hold up well to extreme thermal cycling.

Phil Pilgrim (PhiPi) · 2011-03-31 11:31

As the article points out, not all pennies are created equal. In 1982 pennies went from being copper (which conducts heat well) to copper-clad zinc (which I'm not so sure about).

-Phil

Ttailspin · 2011-03-31 12:39

Well there You go, Quad Pennies... Much more thrifty then Your average Heat sink..
It's even more thrifty when You consider shipping charges. :thumb:

The Paper Clip has some merit.. Quad Paper clips... hmmm
The Secretary passes those out for free...:cool:

John Abshier · 2011-03-31 13:55

Sparkfun sells double sided thermal tape http://www.sparkfun.com/products/9771

from Aavid http://www.aavidthermalloy.com/products/options/theragrip.shtml

John Abshier

RobotWorkshop · 2011-03-31 14:13

I'm pretty happy with the way this turned out. The JB weld (and JB Quick) have help up great for other projects so I expect this should last a while too. Before attaching it I made sure to wipe down the surface of the regulator and also the heatsink to make sure there wasn'y any oils, etc on the surface. Picture shows the final result.

Now just a bit more wiring on my 2nd Propeller board and I can start getting everything together and focus on programming......

Robert

WBA Consulting · 2011-03-31 14:16

For gluing heatsinks to BGAs, our weapon of choice is Loctite Output 383 Thermally Conductive Adhesive. Not cheap ($22 for 25mL from RSHughes and $16 for 13mL of activator), but phenomenal performance.

RobotWorkshop · 2011-03-31 14:21

Hello Andrew,

This is the first time I've ever had to use a glue on heatsink and I used what I had on hand. It certainly seems to help. If I'm going to be doing more heat sinks like this I'll definitely look at getting some of the Loctite or Arctic Silver for gluing them on. May check into the tape as well.

Thanks to everyone for the suggestions!

Robert

HollyMinkowski · 2011-03-31 14:21

The penny falling off and shorting out the board would be bad.
Perhaps drill a hole in the penny and use a small bolt to secure
it to the regulator. A tiny dab of that white goo that is used on
PC processors could make heat transfer better.

A nickle might work even better?

I'm trying to think of some other small bits of metal that could
be commonly found around a house and be drilled and used as
a heat sink.... I wonder if a lid from a tin can could be folded
in such a way as to make a compact but efficient heat sink
for something larger, like a large power transistor maybe.

Phil Pilgrim (PhiPi) · 2011-03-31 14:34

The local hardware store here carries small-size aluminum channel that works when cut to length and glued on. I've also used aluminum angle and aluminum bar stock. In general, surface area is more important than mass for shedding heat.

-Phil

User Name · 2011-04-01 13:16

Tracy Allen wrote: »

The thing about epoxy and smooth surfaces is that it does not hold up well to extreme thermal cycling.

For this reason, I gravitated to using silicone rubber (RTV) to afix transistor and regulator tabs to heatsinks. RTV is not as conductive as metal-filled epoxy, but my calculations show that for a layer about 0.001" thick, the difference in thermal conductivity is minor.

Joints that thin are relatively easy to obtain: First make sure the heatsink and tab are flat, smooth, and clean. Second, press the device firmly and work it around a bit to squeeze out every bit of RTV you can. Then bank up the excess against the sides of the tab (helping facilitate a suction cup effect).

No device I've ever mounted this way has fallen off. YMMV.

RobotWorkshop · 2011-04-01 13:21

I was reading the docs for the xgamestation XGS Micro Edition recently and they mount the Heatsink with RTV silicon. Maybe I'll try that on another board to see how it works for me.

Now that I have the Heat sink installed it seems to help and so far hasn't been that hot. With it installed I hope to avoid the 'Extreme' thermal cycling so it shouldn't be a problem on this board.

For anything that I'm building I usually use the TO-220 case parts so I just bolt on the Heat sink.

hinv · 2011-04-01 21:36

one advantage of the copper penny (pre 1982) on a regulator is you can bend it down and solder it to the edge of the regulator. It might b difficult to get it mounted flat on the surface of the regulator and bent down to solder to the tab at the same time, so maybe 2 pennies are in order.
What would conduct the heat even better would be a pre 1965 silver dime, but at $2.70+ each now, I wouldn't waste it on that.

Thanks for the JB weld tip. My Arctic Silver epoxy went hard after few years, but I have plenty of JBWeld arround.

Zap-o · 2011-04-01 21:55

HollyMinkowski wrote: »

I wonder if a lid from a tin can could be folded
in such a way as to make a compact but efficient heat sink
for something larger, like a large power transistor maybe.

I am defiantly keeping this in mind next time I need a light duty heat sink. This is some great outside the box thinking imo, the idea is simple and very doable without much cost at all.

P.S. I use super glue and so far no major problems.

Browser · 2011-04-01 22:04

i haz tuna can lidz u can haz for heetsinkz. jus ask phil to send themz.

-browz

Tracy Allen · 2011-04-04 12:06

Browser,
I didn't want your kind offer to pass unnoticed. Had you written on Apr. 1st, I might have thought you were fooling! Please ask Phil if how long (in his opinion) it takes for the fishy aroma to dissipate.

I had occasion to look up recommendations on using PCB copper area as a heat sink. The thermal spreading resistance is quite high for 1oz copper, so extending the area beyond a certain point gives diminishing returns. However, it is such a convenient option for surface mount parts.
ST AN1703 Guidelines for Using ST's Mosfet SMD Packages
Micrel AH-17 Designing P.C. Board Heat Sinks

Browser · 2011-04-04 13:15

wutz rong with fishy aroma? hot tranzister glood to tuna can lid makz hol room smel gud.

-browz

HollyMinkowski · 2011-04-04 23:30

I have a good idea for how to fold a can lid to create a nice compact
sink for a TO220 but I have no access to a vice just now to try it out.
Fold the lid in half, then fold again to get a flattened 1/4 circle, then fold
in a section from one corner just wide enough to drill a hole and attach
the TO220 device. Then bend out the can flaps like little wings and spread
the metal out at the top with a screwdriver blade to allow heat transfer
to the air. Should work.

I want to try this with a 7800 regulator and see if it can keep the
regulator cool enough to work at 1 - 1.5 amps

If anyone tries this please post a picture...and send in to Hack-A-Day
as a tip for the frugal :-)

HollyMinkowski · 2011-04-04 23:49

I just had a funny idea.

Looking at the post I noticed that all the posts above mine
were from moderators....a string of moderators with the little
green moderator tag.

Your mission is to photoshop an image that looks just like the
Moderator tag and add it to the top of your avatar image. It should look just
the same as the tag put up by the forum software but change the tag to
say something funny like.

[Troublemaker]
[Weak Minded]
[Spelling Cop]
[Busybody]
[@#$%^!]
[Genius]
[Troll]

LoL..... I'm a hopeless practical joker always thinking of something silly to do.

It would have been a great April fool prank for everyone to be a Moderator when
the Parallax staff looked at the board.... ha :-)

Heat Sink adhesive??

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