What's this black material stuck over my laptop's CPU chip?,  Is it necessary? - Page 1
Forum section: electronics / repair

author: Carman1991
author_rank: Newbie
timestamp: December 08, 2016, 06:29:41 pm
content: UPDATED: I did and attached a new image which its far clearer than the old (deleted) as you can see what is the material I am talking about.Hello,I'm new to this forum (I discovered it thanks to your YouTube channel and I love it) so I wanted to ask you a question to which I haven't found a clear answer on the the whole Internet.I was replacing a falty part in my Dell laptop and incidentally I took advantage of it to perform the proper maintenance. The thing is that while I was cleaning the old thermal grease of the processor (CPU), the black/gray adhesive covering the surrounding circuits of the chip's crystal. stopped as it was very deteriorated. I would like to replace it but I didn't find practically anything about it. I have already seen this stuff in several processors. It is an square adhesive with a texture similar to plastic and a bit of elastic (like an electrical tape), I imagine, will be thermal conductive and its adhesive withstands the high temperatures of the processor chip, no idea.I have done some research and supposedly it has the function of protecting the surrounding elements of the CPU's carrier (copper pads, caps...) avoiding possible shorts when it coming into contact with the heatsink, protects from moisture and also relieves a bit of the excessive pressure applied on that parts (I supposse that's the reason of its thickness).Questions:1) Do you know what's the name of this material is? Would something happen if I did not use it on the chip? (I have seen chips similar than mine that looks like they don't use it.)I attach you a image (homemade picture montage) of a processor with and without that stuff on it2) Could I use kapton tape to perform the same function (on both CPU and GPU)?. I don't think so because is thinner and it isn't thermal conductive and I think kapton is electrical conductive.Thank you in advance!

author: helius
author_rank: Super Contributor
timestamp: December 08, 2016, 06:52:28 pm
content: These are Sil-Pads or another equivalent brand thermally conductive insulators. They are used because they take less labor to install than grease, and provide more electrical insulation. In the past, metallic foils were also used. The performance is worse than using grease by itself with properly lapped surfaces.However, if there is a reason that the heatsink and CPU can't be allowed to touch electrically, it may not be safe to use grease alone.

author: senso
author_rank: Frequent Contributor
timestamp: December 08, 2016, 06:57:03 pm
content: No, that is just plastic with a strong adesive, its there to protect the exposed pads and caps on the top of the cpu carrier.Use Artic MX-4 or Kryonaut, no no-name thermal paste..

author: wraper
author_rank: Unknown
timestamp: December 08, 2016, 07:03:35 pm
content: Just leave it there. It is not deteriorated. it is not even because the surface under it is not flat as there are ceramic capacitors scattered on top of that CPU.

author: tatus1969
author_rank: Super Contributor
timestamp: December 08, 2016, 07:35:38 pm
content: the silver thermal grease has some electrical conductivity, they use it to isolate possible excess material from conductive parts of the cpu.

author: Carman1991
author_rank: Newbie
timestamp: December 08, 2016, 07:36:54 pm
content: Firstly, thank you all for your answers.Quote from: helius on December 08, 2016, 06:52:28 pmIt makes a lot of sense but it's not a thermal pad (like the ones used in GPU chips in order to keep them cool and physically high). It's more like senso suggests....Quote from: senso on December 08, 2016, 06:57:03 pmTotally agree it is more like plastic tape (a bit of elastic if you pull it off). That's my concern, to not using it and get a short or similar problems with the pads and the heatsink but I think it wouldn't be a problem i don't use it (my bare CPU chip looks like the second pic). BTW, I am using Nocta-H1 over the CPU and GPU crystals...Quote from: wraper on December 08, 2016, 07:03:35 pmIt is really deteriorated believe me and it doesn't stick anymore; many years of maintenance you know... (the pic I attached it is not of my CPU because my Laptop is assembled right now so I dind't want to open it again at this moment and I wanted to show you how the material looks)The thing is before I created this thread I replace the motherboard (because the soldered GPU needed some rework but I bought a brand new (OEM) one from a trusted supplier and cheap). So I reused the CPU & the other components from my original one and replaced that material with kapton tape (without touching the crystal which has the grease over it), I clean the laptop with compressed air/Isopropyl and re-assembled it again and turn it on... all seems correct... 10 min later it turn itself off (no temperature problems neither on the GPU or CPU; 48C and 45C respectively. So Thought it could be that material... or the pressure applied by the heatsink... or probably the motherboard needs a BIOS update (because cames new from the factory). However, I had that doubt about the materrial too so asked

author: Carman1991
author_rank: Newbie
timestamp: December 08, 2016, 07:49:04 pm
content: Quote from: tatus1969 on December 08, 2016, 07:35:38 pmI agree. I think it's not recommend to use thermal grease over the surrounding area of the processors crystal for that very same reason. That why I thought it would be nice to use kapton for that propose (couple with the grease over the crystal) but then I discover that there is some kapton that are electrically conductive... I don't know if mine is... because its a chinese, no-branded one and I do not have a multimeter right here to make a test...It's a stupid question but I never come across with this problem before and I haven't found that material for sale either.. onlythispost in ifixit.And I suppose that I cannot use electrical normal black tape on it because it can't handle high temperatures... so I think I gonna buy/search some 3m tape that can handle high temperatures and be thermal conductive, electrically insulator and one-sided adhesive

author: tatus1969
author_rank: Super Contributor
timestamp: December 08, 2016, 08:47:28 pm
content: you can use white thermal grease. that is an electrical isolator afaik, but has slightly worse thermal characteristics.

author: free_electron
author_rank: Super Contributor
timestamp: December 08, 2016, 09:04:01 pm
content: that is underfill epoxy to hold the silicon die on the substrate. part of the chip manufacturing process

author: Carman1991
author_rank: Newbie
timestamp: December 08, 2016, 10:10:06 pm
content: Quote from: tatus1969 on December 08, 2016, 08:47:28 pmI didn't know about the white thermal grease isulation; interesting data to take into account. I gonna keep diggin on this (looking for a tape solution) but it is good to know. I am thinking in not using any tape all because a lot of similar chips doesn't bring one and they hasn't any problem with... its a protection measure after all.Do you think the kapton tape solution is viable? but theoretically it's electrically conductive, no? and I suppose that it is not thermal conductive (i use only it for protecction against heat for my Ics when I am soldering).Quote from: free_electron on December 08, 2016, 09:04:01 pmThat's not underfill epoxy for sure. The underfill is the technique that apply epoxy to "seal", for instance, the chip's silicon die on the PCB's chip. Around the edges or on top of it (glop top). I am talking about the square plastic tape (it is a tape for sure) It pulled off itself and has an adhesive to stuck it to the PCB (and adhesive that holds the processors temperatures for sure).

author: Carman1991
author_rank: Newbie
timestamp: December 10, 2016, 04:38:00 pm
content: THREAD UPDATED!: I updated the image on the first post so you can see the material in a way far clearer than in the old one; it looks rigid but it isn't, itselasticlikePVC/plasticas an electrical tape.Quote from: Carman1991 on December 08, 2016, 06:29:41 pmI' am looking for a tape solution (but its was good to know that there is a thermal grease not electrically conductive).I suppose that tape's replacement must be: thermal conductive?, electrically insulator with a strong adhesive that holds the high temperatures of the procesor (and one-sided) or I could use Kapton tape? (I think it's electrically conductive, no? and thinner and probably doesn't help with heat dissipation....

author: amyk
author_rank: Super Contributor
timestamp: December 10, 2016, 05:40:15 pm
content: That is just to protect the caps and test pads on top of the die carrier, it's not really necessary for operation.

author: Carman1991
author_rank: Newbie
timestamp: December 10, 2016, 06:58:46 pm
content: Quote from: amyk on December 10, 2016, 05:40:15 pmThanks to all of you for your answers. That is what i was looking to hear.... and what I thought but I wanted to be sure.Quote from: blueskull on December 10, 2016, 05:47:12 pmIt's really good to heard that and very sad that there is no similar plastics for sale. So it's only for protection proposes and it is not thermal conductive (it makes sense as the real heat it's in the chip's die/crystal. In fact, the first time I assembled the laptop, I used kapton on the CPU (surrounding areas) in order to protect the copper pads and the caps over it but I was afraid to cause problems because I don't now if kapton is an electric insulator or conductive (I do not have a multimeter right here to test it)... Plus, mine it's a poor chinese quality no branded one...

author: Rasz
author_rank: Super Contributor
timestamp: December 11, 2016, 02:16:31 am
content: its there because those laptops are assembled by chinese children, its an easy way of protecting expensive part from accidental physical damage

author: senso
author_rank: Frequent Contributor
timestamp: December 12, 2016, 10:55:34 am
content: Dont worry too much about that.Noctua NT-H1 is also a good thermal paste.I usually just rip those stickers out, because there is always some old dried out thermal paste in then, and cleaning them is a chore, so I remove them, if the heatsink ever touchs what those stickers are covering either the cpu is now smashed or the whole laptop is smashed to dust to bend the heatsink that much.

author: Sceptre
author_rank: Regular Contributor
timestamp: January 21, 2017, 04:09:10 am
content: Quote from: Carman1991 on December 10, 2016, 06:58:46 pm3M Super 33+ Vinyl Tape is rated to 105C:http://solutions.3m.com/wps/portal/3M/en_US/EMDCI/Home/Products/ProductCatalog/~/Scotch-Super-33-Vinyl-Electrical-Tape?N=5432987+3294355633&rt=rudRegular polyimide (Kapton) has a volume resistivity of about 1 x 1017cm:http://www.dupont.com/content/dam/dupont/products-and-services/membranes-and-films/polyimde-films/documents/DEC-Kapton-summary-of-properties.pdfPolyimide is used as a dielectric in high-performance PCBsThere is a version of Kapton that is electrically conductive, though I suspect that it is not very common:http://www.dupont.com/products-and-services/membranes-films/polyimide-films/brands/kapton-polyimide-film/products/kapton-rs.htmlI agree that you may not want to trust your no-name Kapton tape.

author: Sceptre
author_rank: Regular Contributor
timestamp: January 21, 2017, 04:16:18 am
content: Quote from: Carman1991 on December 08, 2016, 07:49:04 pmWhile some silver thermal greases may be electrically conductive, Arctic Silver 5 is not. The manufacturer recommends avoiding contact with pins etc. due to its slight capacitive property:http://www.arcticsilver.com/as5.htm