Can someone tell me what heat sink material this is - Page 1
Forum section: electronics / repair

author: Cicada
author_rank: Regular Contributor
timestamp: June 17, 2018, 01:06:34 pm
content: HelloI am repairing a PoE ethernet switch. The heat sink on the switching regulator for the PoE outputs fell off. The grey material is rock hard. Almost like a grinding stone to sharpen knife blades. I assume the aluminium heat sink fell of this grey thing stuck on the regulator. No other place where it could come from.Can someone tell me what kind of a heat sink mounting material this is and how should one fix it?1. Buy similar heat sink and grey thing and stick it on a gain? Don't know how I will get the grey thing of without breaking things.2. Buy some sort of glue (thermally conductive?) or sticky tape and just stick the heat sink on top of the grey block again?3. Put the heat sink on the grey block with heat conductive paste and hot snot glue it in place? That will impede the heat sink function but I can may just use a little bit of glue between the heat sink and the other black heat sink. Would prefer not to do this since I will have to buy the gear.Where do I source the grey thingy if I need to buy a new one. This regulator is supposed to supply 60 Watt.ThanksCicada

author: LateLesley
author_rank: Frequent Contributor
timestamp: June 17, 2018, 01:41:57 pm
content: It looks like it may be some form of double sided thermal pad, just like this -https://www.ebay.co.uk/itm/120mm-x-20mm-2mm-6-w-mk-THERMAL-HEATSINK-TRANSFER-PAD-DOUBLE-SIDED-TAPE/202259549498?hash=item2f179bcd3a:g:cYcAAOSwqVJap-gOSince it's a hot running component, you probably want a pad/tape with the highest thermal conductivity ( W/mk ) you can find.As to removing the old one, I can't find any advice. Maybe just try some heat (assuming you have a hot air station) at about 100-150°C, and see if it'll loosen the glue on the underside of it to remove it. Just remember to heat it gently, and bring the temp up slowly over a few minutes.

author: wraper
author_rank: Unknown
timestamp: June 17, 2018, 01:47:21 pm
content: QuoteNope, the grey thing is a ceramic heatsink by itself. Most likely it fell off from the IC on bottom of the picture.

author: wraper
author_rank: Unknown
timestamp: June 17, 2018, 01:53:48 pm
content: Quote from: Cicada on June 17, 2018, 01:06:34 pmI doubt it powers anything other than PCB itself. Voltage for PoE should come directly from PSU.

author: Twoflower
author_rank: Frequent Contributor
timestamp: June 17, 2018, 02:06:00 pm
content: Can you show us the whole board? Probably the heatsink has to be on the packet processor and not the regulator.

author: Cicada
author_rank: Regular Contributor
timestamp: June 17, 2018, 03:37:05 pm
content: Quote from: Twoflower on June 17, 2018, 02:06:00 pmI think your correct. It looks like the heat sink should be mounted on U1 IP178C LFhttp://www.icplus.com.tw/Data/Datasheet/IP178Cx-DS-R13-20080925.pdfThere is only a small sliver of glue on the IC that gives an indication that the heat sink was stuck on it.What glue should one use to fasten the heat sink again?Thanks a lot.

author: Cicada
author_rank: Regular Contributor
timestamp: June 17, 2018, 03:39:10 pm
content: Here is a photo of the whole board.The fan will have to be replaced. It is a bit noisy at start up.

author: Cicada
author_rank: Regular Contributor
timestamp: June 17, 2018, 03:42:13 pm
content: Quote from: wraper on June 17, 2018, 01:53:48 pmCeramic makes sense from the feel of it.And yes I was a bit hasty in my assumption that this regulator power the PoE ports. Its correct that the PSU powers the ports. 47.4V out from the PSU.

author: Twoflower
author_rank: Frequent Contributor
timestamp: June 17, 2018, 04:05:38 pm
content: Wrapper was the one who estimated the right position. I just wanted to be sure that there's no other place out of view :-)There are some heat sink tapes with both sides sticky available. Look at any decent online component shop. They usually offer may shapes and forms. Looking at the heatsink I don't think you need a high performance material as replacement.Before re-attaching the heatsink: Remove the old material.

author: SeanB
author_rank: Super Contributor
timestamp: June 17, 2018, 04:50:15 pm
content: I use a small amount of Pratley quickset steel to attach those, so long as the surfaces are clean, smooth and lightly sanded just before use with some 400 grit waterpaper, then wiped down with alcohol, the bond will be very strong. You only need a small amount, about a match head of the 2 components, mixed with a toothpick on some plastic scrap, and then applied in the middle of the Ic and then press the heatsink down firmly and leave for a half hour to gel.

author: LeonR
author_rank: Regular Contributor
timestamp: June 18, 2018, 09:58:19 pm
content: I'd clean that old thermal interface material from the heatsink and apply a new thermal adhesive (Arctic Silver makes a 2-compound epoxy-like one).

author: TERRA Operative
author_rank: Super Contributor
timestamp: June 19, 2018, 07:42:27 am
content: I vote Arctic Silver thermal epoxy, or JB weld to stick it back on.Lap the heat sink with some 1200 grit wet/dry sand paper on a piece of glass to clean off the old goop and make it nice and flat. Also, the silver particles in Arctic Silver are around the same size as 1200 grit apparently, so they'll interface nicely. A final cleanup of everything with isopropyl alcohol and you'll be set.Don't forget to gently clamp the heat sink too until the epoxy sets, just to make sure it sticks properly.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 19, 2018, 01:50:17 pm
content: Put some adhesive on the heatsink and stick it back down.Preferably something strong, thermally conductive, and maybe permanent (like epoxy).The ceramic piece probably is ceramic; unsure if it's a more conventional type (like actual porcelain ceramic), or a technical ceramic like silicon or aluminum nitride (or both).The heatsink doesn't seem to be doing much in any case. Very little heat comes out the top of a package like that -- the black plastic isn't very conductive, and all the heat is generated down by the tab. Probably they didn't need much, so definitely don't sweat about getting a good thermal connection (like lapping the freaking heatsink... go figure, some people are nuts).Tim

author: Bashstreet
author_rank: Frequent Contributor
timestamp: June 19, 2018, 05:22:08 pm
content: Quote from: TERRA Operative on June 19, 2018, 07:42:27 amCleaning is good idea but there is no need to try get it smooth by any means. In fact the imperfections only increase surface area and help the thermal transference.

author: Rasz
author_rank: Super Contributor
timestamp: June 19, 2018, 08:10:56 pm
content: This heatsink is there to dissipate 2-3W of thermal energy, so no need for anything fancy, even superglue will be fine.

author: Bashstreet
author_rank: Frequent Contributor
timestamp: June 20, 2018, 01:27:07 pm
content: Quote from: Rasz on June 19, 2018, 08:10:56 pmI would not suggest superglue as their characteristics can vary.Not that i have not used thermal paste and clued the corners of ic heatsinks with superclue...

author: Cicada
author_rank: Regular Contributor
timestamp: June 25, 2018, 08:16:01 pm
content: Thanks for all the suggestions. I think I will go with SeanB's solution. It is the easiest for me to source the Pratley Steel Quickset.The arctic silver would be nice but its a bit expensive for such a small once off job.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 25, 2018, 08:34:05 pm
content: For a low power chip like that one, I would suggest JB Weld.