Computer PCI card thermal adhesive failure- 'heat sink sink'? - Page 1
Forum section: electronics / general

author: cdev
author_rank: Super Contributor
timestamp: December 26, 2016, 04:34:46 am
content: Has anybody else had this problem?I'm glad I caught this in time. These heatsinks came from DX.com I think, so obviously, from China.They had thermal pads on them which allowed them to migrate over the space of maybe three months that its been in there.Its a video capture card. The (Conextant BT878A) chips get pretty hot, but not as hot as you would think from looking at this. The heatsinks are still stuck on there pretty well, it seems, but, as you can see, they have migrated.

author: Ampera
author_rank: Super Contributor
timestamp: December 26, 2016, 05:32:07 am
content: Quote from: cdev on December 26, 2016, 04:34:46 amWhy not use a proper thermal adhesive? Arctic Silver probably makes one. But be warned, once thermal glue is on there, the heatsinks will not come off.Ever.We still remember the guy who butchered his GPU by mistaking thermal adhesive for regular thermal compound.

author: SeanB
author_rank: Super Contributor
timestamp: December 26, 2016, 06:42:53 am
content: Pratley quickset steel works well enough on those heatsinks, after you sand both the base of the heatsink and the chip top with 220grit waterpaper to get a matt finish, and wipe the surfaces down with some thinners. A match head size bead of each component of the epoxy is all you need for each of those chips, it will never come off once cured, and the thermal resistance is pretty low. Done that on a lot of boards, using old motherboard south bridge and VRM heatsinks, and it works a lot better than the sticky pad they come with.

author: Halcyon
author_rank: Unknown
timestamp: December 26, 2016, 09:03:01 am
content: Yep, seen that happen in cheap and nasty devices. I remember ripping some off a device (can't remember what it was now, maybe a crappy set-top box or something) and it looked like the heat sinks were just stuck on with clear double-sided tape, not even a proper thermal pad.Quote from: TwoOfFive on December 26, 2016, 05:32:07 amArctic Silver is fine but there is also a lot of marketing wank behind it. I just use the Dow Corning stuff which is more than adequate. Arctic Silver is pretty easy to get off, it's far from a glue. The best thing I've found for removing heat sink compounds or glue residue left over from tape or labels is actually an Orange oil air freshener spray. They sell one in the supermarkets here in Australia for less than AUD$5 for 125ml and it's made of about 30% Orange oil (cold pressed from citrus peel) with the rest being alcohol. Finish the job off with a quick wipe of IPA to remove any residual oils and it'll look like new.

author: amyk
author_rank: Super Contributor
timestamp: December 26, 2016, 03:17:53 pm
content: There are holes for a heatsink retention clip, but the manufacturer was too cheap to use them.

author: Ampera
author_rank: Super Contributor
timestamp: December 26, 2016, 04:08:36 pm
content: Quote from: Halcyon on December 26, 2016, 09:03:01 amI said Arctic Silver MAKES a thermal adhesive, not that their flagship product, Arctic Silver 5 is an adhesive. That's just a standard interface material.

author: mac.6
author_rank: Regular Contributor
timestamp: December 26, 2016, 04:25:55 pm
content: Is there really a need for heatsink at all?As long as your case is decently ventilated there should be no issue...

author: SeanB
author_rank: Super Contributor
timestamp: December 26, 2016, 04:45:19 pm
content: Wrong style heatsink for those holes in any case, they would be a pin milled heatsink with a central channel, not those extruded ones.As to not using a heatsink you will have to arrange for airflow over those chips of around 100CFM to keep them cool if they are running hot. Without a heatsink I think those will unsolder themselves in short order with no case cooling fan present.

author: KhronX
author_rank: Frequent Contributor
timestamp: December 26, 2016, 05:13:59 pm
content: Conexant (originally Brooktree) Bt878 - weren't those the basis for a lot of TV-tuner cards, about a decade or more ago? I never knew those ran hot enough to warrant heatsinking in the first place.https://en.wikipedia.org/wiki/Brooktreehttp://www.ituner.com/spectra/Bt878.pdf

author: SeanB
author_rank: Super Contributor
timestamp: December 26, 2016, 05:24:00 pm
content: They run hot enough that reliability suffers if you do not heatsink them, and pretty much every one I saw had a scorch mark on the board around them. Had a few tuner cards with them that died after a while, so i added a heatsink to the survivors. The Pinnacle cards as well IIRC used them to capture video, and those ran flaming hot as well.

author: cdev
author_rank: Super Contributor
timestamp: December 26, 2016, 05:32:38 pm
content: My (no-name) BT878A card came without any heatsink but these kinds of cards last longer if they have them, so I added these.

author: rob77
author_rank: Super Contributor
timestamp: December 26, 2016, 05:33:25 pm
content: be very careful with epoxy thermal adhesives , many of them contain metal particles and are in fact conductive. if you spill a little over the legs of those quad flats, then most probably you can throw your card into the trash.i would rather just replace the sticky thermal pads on those heat-sinks and avoid permanent glue-down.

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 27, 2016, 07:45:28 am
content: JB Weld is cheap and plenty thermally conducting for low power chips like those. In my experience, it's not (electrically) conductive enough to cause problems if it gets on the pins. It has even been used on high power chips like a CPU with good results, although proper thermal epoxy will likely work better.http://www.overclockers.com/better-than-thermal-grease/

author: ConKbot
author_rank: Super Contributor
timestamp: December 28, 2016, 02:05:12 pm
content: +1 to jb weld. A thin layer of any adhesive is going to be way more conductive thermally than the plastic of an IC. High thermal conductivity isn't worth worrying about until you're getting into applications with a high heat flux (watt/cm^2) like processors or power LEDs not on a star/MCPCBJB weld isn't conductive unless you apply enough pressure to compress the metal fill in it. Ive bonded a die cast emi shield to a PCB and had <100mohm resistance between the two after clamping it pretty hard for 24h.