Hot Melt Glue - An Insulator?  - Page 1
Forum section: electronics / beginners

author: bullet308
author_rank: Frequent Contributor
timestamp: June 19, 2012, 09:05:02 pm
content: Hi:Working on my first Manhattan-style project (a relatively elaborate micro controller-driven Geiger counter) and was wondering how hot melt glue did to secure the various circuit elements and keep them from shorting to one another, etc.Thanks:

author: SeanB
author_rank: Super Contributor
timestamp: June 19, 2012, 09:18:43 pm
content: It works initially, but absorbs moisture and becomes conductive after a while. It also softens with heat.

author: bullet308
author_rank: Frequent Contributor
timestamp: June 19, 2012, 10:03:47 pm
content: Okay, so I will avoid that. What would the recommended product be for this application?

author: johnmx
author_rank: Frequent Contributor
timestamp: June 19, 2012, 10:13:33 pm
content: Quote from: SeanB on June 19, 2012, 09:18:43 pmAre you sure about that?I have done it in some circuits for outdoors with no problems whatsoever.It’s really important to know that.

author: StubbornGreek
author_rank: Frequent Contributor
timestamp: June 19, 2012, 10:20:41 pm
content: Quote from: SeanB on June 19, 2012, 09:18:43 pmI'm not sure how that would work. Can you explain that a little further...thanks.

author: digsys
author_rank: Unknown
timestamp: June 19, 2012, 10:44:23 pm
content: I've used it to hold up "heavier" components, or stop flex on PCBs, often between all the pins, and in high power areas.I have 100s units still 100% fine now for 20+ yrs. Never had a breakdown / leakage. Lots in outside vehicles.I use it sometimes instead of silicon ! Occasional Megger tests on HV vehicles all look good.

author: Rufus
author_rank: Super Contributor
timestamp: June 19, 2012, 10:57:15 pm
content: Quote from: SeanB on June 19, 2012, 09:18:43 pmIt doesn't. Hot melt provides excellent water tight sealing, very good insulation, and I read low losses at high frequencies.I have a 10M resistor soldered between two bits of PVC insulated wire and covered in hot melt. It has been in a jar submerged in a saturated salt solution for at least 5 years and it still reads a little over 10M. I wrote the exact measured value and the date on the lid of the jar when I started the experiment but sunlight turned it invisible within a year. The lid is now covered in rust. I expect it to fall to bits in a year or two. I bet the resistor will still measure 10M.

author: bullet308
author_rank: Frequent Contributor
timestamp: June 20, 2012, 01:04:22 am
content: Well, okay, there seems to be a difference of opinion here... :-/I am inclined to think that hot melt will do at least for my own modest purposes.Most of the alternatives I can think of seem to offer a risk of corrosion or some unpleasant chemical reaction.

author: Psi
author_rank: Super Contributor
timestamp: June 20, 2012, 02:20:13 am
content: I also use it a lot on electronics and have never had any issues of it becoming conductive.Maybe there are a few different types of gluegun 'glue' that we're talking about here.Transparent vs White for example.Also, cheap sticks from china could have anything mixed in to save on cost.

author: gjh
author_rank: Contributor
timestamp: June 20, 2012, 04:11:28 am
content: Whao what a discussion... I use hotglue religiously just for a quick make sure its insulated if I doubt any metal to metal contact with components...

author: SeanB
author_rank: Super Contributor
timestamp: June 20, 2012, 04:52:55 am
content: Most of the older TV sets used hot melt to stick things down. Over years of running hot and with high voltage on bare copper under them they tend to change composition, and go brittle as the volatile components are evaporated out. The left over fillers absorb moisture from the air, and eventually the stiff mess gets a copper chloride colouring, and causes problems.It works for holding wires in a loom, and for sticking down insulated components, though there superglue is better for bodge mods, especially if you use a thickened one that has gap filling properties.

author: Psi
author_rank: Super Contributor
timestamp: June 20, 2012, 05:12:50 am
content: Insulating high voltages like that is quite different.I think most of us are talking about <230V

author: SgtRock
author_rank: Unknown
timestamp: June 20, 2012, 05:27:34 am
content: Greetings EEVBees:--I do not use Hot Melt because of its generally inferior holding properties. I have repaired a lot of problems where the Hot Melt let go after a year or two of use. I use JBWeld, Electronic Grade Silicone, and Super Glue. Some times I use the super glue to tack things down while the JBWeld or the Silicone sets up. This allows me to finish the repair and Bobs you uncle."I'm all in favor of the democratic principle that one idiot is as good as one genius, but I draw the line when someone takes the next step and concludes that two idiots are better than one genius."Leo Szilard 1898 - 1964Best RegardsClear EtherBest RegardsClear Ether

author: amyk
author_rank: Super Contributor
timestamp: June 20, 2012, 08:14:19 am
content: Quote from: Psi on June 20, 2012, 02:20:13 amA lot of cheap Chinese computer PSUs have lots of this component-holding glue in them which is white, and becomes brown, conductive, and brittle with heat over time (eventually causing failures.)

author: Psi
author_rank: Super Contributor
timestamp: June 20, 2012, 08:32:53 am
content: Quote from: amyk on June 20, 2012, 08:14:19 amThat's not ya typical hot glue.I think its silicon based.

author: Stephen Hill
author_rank: Regular Contributor
timestamp: June 20, 2012, 08:47:40 am
content: The wikipedia might be a good place for info:http://en.wikipedia.org/wiki/Hot-melt_adhesiveIt lists a wide range of different compounds for the hot glue. There is one which is specifically designed to be conductive, Polypyrrole.This might suggest that the others are insulators or very poor conductors.I guess the only real way to know is to test.CheersStephen

author: Kilroy
author_rank: Regular Contributor
timestamp: June 20, 2012, 12:53:31 pm
content: I guess I don't get the whole hot melt glue thing.Why make use of an adhesive you have to heat up when you can simply use an electronics grade silicone that flows freely over a wide temperature range yet can be be extremely heat tolerant and can be absolutely trusted to be totally non-conductive. And gets the job done every-single-time.Not to be a putz...but I mean really, does *anyone* actually own a glue gun that does not...- tip over with the least provocation- drip glue on their bench/circuits/and such- have an annoyingly cheap, inflexible line cord that virtually guarantees the gun will spend the greater part of it's time on it's side or sweeping stuff off the bench every time you go to use it- add yet another noxious smell to the shop you could well do without- look like something your grandmum would use to stick a plastic daisy on a straw hat

author: david77
author_rank: Frequent Contributor
timestamp: June 20, 2012, 01:17:39 pm
content: Hot melt glue has lots of uses, not just sticking things together.I've made moulds to cast special plugs and adapters, it's handy to fill crappy chinese cinch, DC or jack plugs to help the poor strain relief in them.I think it's a handy thing to have around.

author: T4P
author_rank: Super Contributor
timestamp: June 20, 2012, 01:22:56 pm
content: Quote from: Kilroy on June 20, 2012, 12:53:31 pmMine does tip, but it hasn't dripped glue in a long time, inflexible it is yesnoxious smell it hasn't

author: digsys
author_rank: Unknown
timestamp: June 20, 2012, 02:09:25 pm
content: I LOVE my glue gun. One day we're going to get married.

author: Kilroy
author_rank: Regular Contributor
timestamp: June 20, 2012, 02:58:41 pm
content: That's could leave you a little tender after the honey moon...

author: SeanB
author_rank: Super Contributor
timestamp: June 20, 2012, 04:10:07 pm
content: I buy the guns by the dozen, used at work for assembly and such. Cheap nasty thing with a short life, but the quality ones ( at 10 times the price) only last 4 times as long. They all leak, all fail due to the cord or heater shorting, and all die a slow death.Only good thing is I have a lot of plain kapton tape and a lot of short high heat wire around after stripping them.

author: T4P
author_rank: Super Contributor
timestamp: June 20, 2012, 04:12:23 pm
content: Quote from: SeanB on June 20, 2012, 04:10:07 pmThe first gun i had shorted to the body ...

author: SeanB
author_rank: Super Contributor
timestamp: June 20, 2012, 04:22:34 pm
content: That is why I buy all plastic ones........ Not even worth changing the plug on them, they just use a cheap n nasty Euro adaptor outlet adaptor. I just have to use the ones that were not recalled because they catch fire.

author: Kilroy
author_rank: Regular Contributor
timestamp: June 20, 2012, 04:35:27 pm
content: Quote from: DaveXRQ on June 20, 2012, 04:12:23 pmYou see...now that just ain't right.

author: RCMR
author_rank: Frequent Contributor
timestamp: June 21, 2012, 03:18:20 am
content: Hey, don't knock hot glue! It's a miracle of the modern age!

author: Psi
author_rank: Super Contributor
timestamp: June 21, 2012, 03:25:28 am
content: Quote from: Kilroy on June 20, 2012, 12:53:31 pmThe best thing about hot-glue is that it sets in seconds.It's also strong yet flexible so can be removed without too much trouble.And the glue sticks are really cheap.

author: Treknology
author_rank: Newbie
timestamp: March 27, 2013, 10:43:16 am
content: I ended up here looking for similar answers. I am a great user of hot-melt glue----it's fantastic for prototyping. However, I am looking for something that will cope with higher temperatures and cope with "high" DC voltages.I have an old isolator that goes between two serial devices to protect from lightning strike. Down the very middle of the board is a row of optical chips, and all the external pins (and solder pads) are covered in a silicone-like "glue" to stop the spark from jumping around the chips. The device itself is obviously sacrificial, but when modems were $600 or more each, definitely a worthwhile investment.It is a "glue" like this that I'm seeking. Hot melt is great for prototyping, but I find that over time it tends to let go in direct relation to the presence of Murphy's Law.

author: Alana
author_rank: Frequent Contributor
timestamp: March 27, 2013, 11:11:11 am
content: Quote from: Treknology on March 27, 2013, 10:43:16 amI agree.Hot glue over time looses adhesion to flat surfaces and fells off but if its used as a potting compound its quite nice. For example - my usual way to fix DC plugs on laptop is, after soldering to cover wires and back of the plug with hot glue and then put heatshrink around it and heat it to 180-200 deg with hotair. Glue melts inside heatshrink and fills all the gaps preventing accidental short circuts and if done properly entire plug resembles factory made one.

author: ConKbot
author_rank: Super Contributor
timestamp: March 27, 2013, 11:40:27 am
content: Guys, theres hot glue, and then there's hot glue. The cheap stuff in white sticks at the craft store is one thing, but once you get into "professional level" stuff, its a whole new ball game. Much like epoxy, its all about selecting the right stuff for the job. Dont expect 5 minute epoxy to be shock resistant and to adhere to something like a smooth aluminum surface. But if you get the right epoxy, its all good.IVe used 3M 3779, its heat resistant to 300F, melts at 325F (eutectic tin lead solder melts at 361! Good luck trying to get this stuff off a PCB with a hot air gun and not take components with it, or not take forever doing so) It sticks to stuff VERY well, is quite hard to get to peel off. Its quite firm, and you can just gouge it out easily with a tool. But its pricy. 11lb minimum order, $490 from mcmaster-carr.definitely out of the price range of a hobbyist, but if you need something you know is going to work and can justify the price on a work/professional level, its awesome. I was using it for potting some digital isolators that fit in a backshell of a connetor that we had put together that needed to be weather proof.

author: MacAttak
author_rank: Unknown
timestamp: March 28, 2013, 01:42:44 am
content: There is a wide range of quality in the stuff you get from a typical hobby store or your local hardware store. And most of the time the packaging doesn't even say what's actually in the sticks.Early next year you will be able to buy one of these though. Effectively a "hot glue pen" that works with ABS or PLA, which have a much higher softening temperature than normal hot glue, and the electrical properties are well-established:http://www.the3doodler.com/The main downside is that the plastic sets really quickly compared with hot glue. You only get a few seconds once it leaves the extrusion tip.They start shipping in a few months, but there is a huge backlog of orders they need to ship out before they will be selling through normal channels (at least until January/February next year).I am expecting to get one in October, and plan on using it to replace some of what I use hot glue for today.