What is the white glue/goo/rubber that fixates high-rise capacitors called - Page 1
Forum section: electronics / repair

author: eplpwr
author_rank: Regular Contributor
timestamp: November 20, 2020, 07:17:41 pm
content: Hi!I'm in the process of replacing a number of capacitors on a PSU board (for a 2014 vintage Samsung 4K monitor). Many of the capacitors are fastened to the PCB with some kind of white stuff that is somewhat rubber-like - it is obvious that the stuff is there to steady the capacitors mechanically. It can easily be cut with a knife or removed piecemeal with a cutter, especially since my capacitor removal is desctructive.After finished cap replacement, I would like to add similar "goo-stuff" to make the capacitor fixing as robust as before, but I am totally unaware what "the white stuff" is called. Does anybody know what the stuff is, and also if there is a special process or tools needed when applying it?Regards,eplpwr

author: Yansi
author_rank: Super Contributor
timestamp: November 20, 2020, 07:27:02 pm
content: It is some form of a non-acidic silicone.

author: wraper
author_rank: Unknown
timestamp: November 20, 2020, 07:30:50 pm
content: Usually neutral RTV silicone adhesive rated for electronics. Sometimes 2 part adhesive might be used as well. You can buy it in western countries but it's expensive (EUR 25+ for 0.5L), usually comes in large tubes and has very limited expiry time.But you can get 45ml tubes from China for a few bucks delivered. There are several types with different properties and are named with 701-708 numbers. Once opened it's advisable to put it into moisture barrier bag with silica gel desiccant so it does not get spoiled during storage. For example 706 I got from China is better than 3 types from ACC silicones I tried in the past.https://aliexpress.com/item/1005001608574673.html

author: ambrosia heart
author_rank: Regular Contributor
timestamp: November 21, 2020, 02:06:09 am
content: Sorry, did not read your composition thoroughly.See photos. Read 1st photo words carefullybefore you buy.How about the quality of 704? one word: good.

author: eplpwr
author_rank: Regular Contributor
timestamp: November 27, 2020, 06:18:29 pm
content: Thanks for all the feedback, I've now ordered types 706 and 707 to try out.Best regards,eplpwr

author: Labrat101
author_rank: Unknown
timestamp: November 29, 2020, 08:54:55 pm
content: Don't use RTV or any thing similar .They use a mixture of rubber solution . The nearest you will find to day is Polymer rubber. 'Super 7 Fast Fix' dries to non Harding Polymer rubber and does not cause any damage .I have some were a book on how to make this . But I can't remember off hand where it is.Going back 50yrs .. we mixed puncher glue . ( bike repair kit stuff ) had a tube of liquid Rubber. We had a large tin in the workshop . but that was in the days when health & Safety was not an issue.The other ingredient I can't remember for the life of me what it was called .Acrylic 2 mix dries like glass and is not flexible.I use polymer Rubber works fine . And can buy it normally at any good builder supplier .Second option HOT Glue is nylon and works well . an stays flexible.Good Luck

author: The Soulman
author_rank: Super Contributor
timestamp: November 29, 2020, 09:02:40 pm
content: Quote from: Labrat101 on November 29, 2020, 08:54:55 pmI'm using hot glue for that as well, surfaces may need a wipe with some alcohol for it to stick tho.

author: Labrat101
author_rank: Unknown
timestamp: November 29, 2020, 09:16:13 pm
content: Quote from: The Soulman onTodayat 09:02:40 pm>Quote from: Labrat101 onTodayat 08:54:55 pmI'm using hot glue for that as well, surfaces may need a wipe with some alcohol for it to stick tho.Hot Glue I forgot to mention is not good in really hot spaces ..Polymer is better as it has a good heat transfer . and good High voltage resistance 10kv plusI have not used it on anything higher than that .

author: wraper
author_rank: Unknown
timestamp: November 29, 2020, 09:18:37 pm
content: Quote from: Labrat101 on November 29, 2020, 08:54:55 pmQuoteYeah, good luck with crap you suggested.

author: wraper
author_rank: Unknown
timestamp: November 29, 2020, 09:35:18 pm
content: Quote from: The Soulman on November 29, 2020, 09:02:40 pmDon't be surprised when you find it delaminated from surfaces after a few years or almost immediately when device was used at low temperatures.

author: Labrat101
author_rank: Unknown
timestamp: November 29, 2020, 09:39:07 pm
content: @ wraperQuoteI am not getting into an argument with you . But I am sorry you are wrongby making that comment . And there are many reports from Universities and document on this subject . Polymer pro's and cons and RTV 's .Not Hard feeling

author: wraper
author_rank: Unknown
timestamp: November 29, 2020, 09:43:25 pm
content: Quote from: Labrat101 on November 29, 2020, 09:39:07 pmSome random crap from hardware store of course is 'better' than RTV silicones specially marketed for electronics use and with specified dielectric parameters.

author: wraper
author_rank: Unknown
timestamp: November 29, 2020, 09:46:06 pm
content: If you don't believe that chinese selection table, here is a datasheet for western stuff:http://www.farnell.com/datasheets/1974040.pdfQuote

author: Labrat101
author_rank: Unknown
timestamp: November 29, 2020, 09:54:54 pm
content: Quote from: wraper onTodayat 09:43:25 pm>Quote from: Labrat101 onTodayat 09:39:07 pmSome random crap from hardware store of course is 'better' than RTV silicones specially marketed for electronics use and with specified dielectric parameters.And you believe that crap from ali express . 99% of that stuff is fake $1.66If you want to think that stuff is tested .. The Joke is on you .I would not trust that on 5 volts .... Ali china stuff NO. WAY

author: wraper
author_rank: Unknown
timestamp: November 29, 2020, 10:02:15 pm
content: Quote from: Labrat101 on November 29, 2020, 09:54:54 pmThose silicones are for Chinese internal market and are standardized types made by many manufacturers. Nothing wrong with them. Not to say you ignored datasheet I provided for western stuff. Also sorry, but I will trust Chinese neutral silicone (by it's nature non corrosive) rated for electronics, compared to some random stuff completely untested for anything electricity related. BTW I know by experience that hot glue does not last in any conditions.

author: Labrat101
author_rank: Unknown
timestamp: November 29, 2020, 10:15:43 pm
content: I did read the other list.And we did test that stuff .. it smells horrible when it burns .Plus it has a high PH and it is corrosive . No 2 tubes are the same. It also failed .. So if you like it .. enjoy it.

author: wraper
author_rank: Unknown
timestamp: November 29, 2020, 10:21:36 pm
content: Quote from: Labrat101 on November 29, 2020, 10:15:43 pmDunno what you tested but it seems you are completely ignorant about difference between acetoxy and neutral curing types. Silicones do not burn BTW, at worst they disintegrate at high temperature.