Flexible heatsink - Page 1
Forum section: electronics / projects

author: trevwhite
author_rank: Frequent Contributor
timestamp: November 07, 2016, 05:26:07 pm
content: I need to heatsink a smt component but its not practical to attached a metal heatsink. Anyone know of some flexible paste or silicone type solution that molds to an area and acts as a very nice heatsink? MAybe something like heat transfer compound that actually sets?

author: ajb
author_rank: Super Contributor
timestamp: November 07, 2016, 06:05:30 pm
content: Do you need it to be flexible, or conformable?There are thermally conductive and electrically insulating epoxies, but I'm not aware of any that cure to a flexible state. Also, they're not cheap. Kona 870ft-lv-dp is one.Some time ago a sales rep assured me one of his lines could cross a Chemplex silicone heatsink paste we were using at a much lower cost. A couple days later he called and told me they were going to send us afive poundsample batch for free. That would be several years worth of compound for us, so it raised my eyebrows, but he assured me it was no trouble. What eventually showed up was...you know that white or blue sticky stuff you use to put posters up on walls? Well, imagine a five pound block of that. Maybe a little bit stiffer. It's completely and utterly unsuitable for our purposes--I guess it would take several tons of clamping force to get it down to a reasonable film thickness in our assemblies--but apparently thermally conductive blue-tack is a think you can get.Come to think of it, I never did hear from that rep again...Anyway, no compound or epoxy is going to have nearly the thermal conductivity of a slab of aluminum unless you get into something exotic, so whether or not it's even worth doing will depend a lot on the application and how much heat you need to remove.

author: Marco
author_rank: Super Contributor
timestamp: November 07, 2016, 06:06:58 pm
content: They are meant to bridge microns, not cm. You can't make a heat-spreader/sink out of resin. A via to the other side of the board will be much more conducive to heat.Maybe you could use oriented graphite sheets in some way?

author: trevwhite
author_rank: Frequent Contributor
timestamp: November 07, 2016, 07:15:15 pm
content: I do not need it to remain flexible. It can cure hard as long as it starts off flexible to mold to the profile of the components.I have vias through to the other side and the board is 0.8mm to ensure the via holes offer the least thermal resistance possible. I am exploring alternatives really and if there are things I can do to improve it. The IC package itself gets pretty warm. I am sure I have seen some flexible sheets that sit on ICs and act as a heatsink of sorts.

author: suicidaleggroll
author_rank: Super Contributor
timestamp: November 07, 2016, 07:35:22 pm
content: How about a thermal pad and a regular heatsink on the other side?eg:http://www.digikey.com/product-detail/en/t-global-technology/TG2030-25-25-5/1168-1557-ND/3042370They of course come in different sizes and thicknesses. They're relatively soft and will conform around small ICs and passives while making decent thermal contact with the area as a whole.

author: Ice-Tea
author_rank: Super Contributor
timestamp: November 07, 2016, 07:42:02 pm
content: I suppose this is what you are looking for?Those pads can be found from companies such as Bergquist, Thermaloy, T-Global,... but they are meant to even out height differences on the underground (be it a rough surface, or components or...), not as a heatsink. They serve as an intermediary to a heatsink.

author: nali
author_rank: Frequent Contributor
timestamp: November 07, 2016, 08:16:58 pm
content: Quote from: trevwhite on November 07, 2016, 05:26:07 pmAssuming you actually have some method to take the heat away, sounds like something like this?http://uk.rs-online.com/web/p/thermal-grease/3629698/It ain't cheap though!

author: trevwhite
author_rank: Frequent Contributor
timestamp: November 07, 2016, 08:43:43 pm
content: Well at the moment this stuff looks like the most likely to do somethinghttp://uk.farnell.com/t-global/t62-150-050-100g/graphite-sheet-0-5mm/dp/1372955

author: Ice-Tea
author_rank: Super Contributor
timestamp: November 07, 2016, 08:47:14 pm
content: Keep in mind that graphite is conductive. And not all that flexible.

author: trevwhite
author_rank: Frequent Contributor
timestamp: November 07, 2016, 08:53:05 pm
content: Conductive isnt good. Tut. I didnt read up on that stuff properly.

author: trevwhite
author_rank: Frequent Contributor
timestamp: November 07, 2016, 08:55:48 pm
content: I just wanted something to spread a bit of heat over a wider area. I know that is what a heatsink does but I was thinking there must be thermally conductive materials that can do say half the job of aluminium.

author: nali
author_rank: Frequent Contributor
timestamp: November 07, 2016, 09:03:18 pm
content: Quote from: trevwhite on November 07, 2016, 08:43:43 pmThat's not quite "a paste that will mold to an area" as per your OP. You'll need to give a bit more info e.g. what is the component package, is there an airflow, are you trying to interface to a heatsink or enclosure wall etc. ?

author: Ice-Tea
author_rank: Super Contributor
timestamp: November 07, 2016, 09:04:18 pm
content: Graphite, as you mentioned, but otherwise you're pretty much done around 20W/mK or so.

author: vinicius.jlantunes
author_rank: Regular Contributor
timestamp: November 07, 2016, 09:24:02 pm
content: Quote from: trevwhite on November 07, 2016, 08:53:05 pmwell, here is the description in that link:QuoteKinda counter intuitive indeed but well, they say it's not conductiveEDIT: well, then a couple phrases later they say:QuoteDoh!

author: trevwhite
author_rank: Frequent Contributor
timestamp: November 07, 2016, 10:37:56 pm
content: Well thanks for all the comments. Sounds like there really is no alternative material to metal.

author: Marco
author_rank: Super Contributor
timestamp: November 07, 2016, 10:45:12 pm
content: That stuff you link is something fundamentally different from the oriented graphite sheets BTW.Oriented graphite is a much better heat spreader.

author: trevwhite
author_rank: Frequent Contributor
timestamp: November 07, 2016, 11:06:52 pm
content: Any links to a uk supplier of Oriented graphite heat spreader stuff?

author: Marco
author_rank: Super Contributor
timestamp: November 07, 2016, 11:47:01 pm
content: http://nl.mouser.com/new/panasonic/panasonicthermalgraphite/

author: trevwhite
author_rank: Frequent Contributor
timestamp: November 08, 2016, 12:08:39 am
content: http://uk.farnell.com/panasonic-electronic-components/eyga091203m/pyrolyt-graphite-interface-sheet/dp/1800092It seems its £20 for a smallish piece of this. The stuff looks great but that price is a bit much really.