Hot melt glue or something else? - Page 1
Forum section: electronics / projects

author: jeremy
author_rank: Super Contributor
timestamp: January 29, 2014, 11:46:56 am
content: Hi all,Sometimes when I am modifying a PCB I need to use some sort of adhesive to stop any wires flexing on the solder joint. I have in the past used ultra cheap hot melt glue sticks with an ultra cheap 15W glue gun and I am finding that the glue is often not runny enough to seep down past wires and onto the PCB and solidifies frustratingly quickly (a 20-30 second drying time would be perfect, I feel like I'm getting 5 seconds at best).Is there a better way to do this? Or am I just using the wrong/crappy equipment?Thanks.

author: DmitryL
author_rank: Regular Contributor
timestamp: January 29, 2014, 11:52:30 am
content: After applying a hot glue from your glue gun you can try give it a finishing touch with a hot air soldering station. Air temperature around 150 degrees C should be fine.It will melt it.

author: Frost
author_rank: Regular Contributor
timestamp: January 29, 2014, 12:00:23 pm
content: Quote from: jeremy on January 29, 2014, 11:46:56 amI use UV curing adhesives for this purposes.To start the curing process I use a UV LED torch like dentists do.

author: ConKbot
author_rank: Super Contributor
timestamp: January 29, 2014, 12:02:54 pm
content: It sounds like using a high temperature glue gun instead of a low temp glue gun (and different sticks as appropriate) would help the glue flow better before it sets. Mind your fingers as IIRC high temp glue guns and dispense at ~350F.You could also use acid free silicone (methoxy cure) or 5 minute epoxy. Do some testing to make sure your adhesive of choice sticks to the solder mask, as its a surprisingly resilient and hard to bond to at times, surface.

author: jeremy
author_rank: Super Contributor
timestamp: January 29, 2014, 12:14:06 pm
content: Quote from: Frost on January 29, 2014, 12:00:23 pmThis is quite interesting actually, can you recommend any product codes or Loctite/3M numbers?

author: HSPalm
author_rank: Regular Contributor
timestamp: January 29, 2014, 12:42:01 pm
content: There exists both low temp and high temp glue guns, do you know which type you have? I know parents ask for the low temp type in hobby stores because its more safe for kids.

author: robrenz
author_rank: Super Contributor
timestamp: January 29, 2014, 12:53:43 pm
content: Gel type super glues with a dabbed with super glue activator sprayed onto a Qtip works well and is much cheaper yet less convenient than the UV approach.

author: luky315
author_rank: Regular Contributor
timestamp: January 29, 2014, 01:17:06 pm
content: Hot Glue is hygroscopic. Don't use it near precision and/or stable circuits. I had a lot of problems with it.

author: HSPalm
author_rank: Regular Contributor
timestamp: January 29, 2014, 01:39:14 pm
content: Yup that's true. I know hot glue is used for tuning certain types of circular polarized antennas which can not be trimmed in length.

author: Frost
author_rank: Regular Contributor
timestamp: January 29, 2014, 01:41:06 pm
content: Quote from: jeremy on January 29, 2014, 12:14:06 pmYes, but I can't recommend anything you can buy in AustraliaI use Bondic, it's a product you get here at a certain hardware store.It's not really cheap and I am sure from Henkel or 3M youwill get more value for money, same thing with the super glueyou can buy at the hardware stores.But I only need small amounts to retain wires or SMD chipsfor hand soldering.But one tube last for years, instead of the supergluewhich is always dried out when I need it

author: nctnico
author_rank: Super Contributor
timestamp: January 29, 2014, 01:55:31 pm
content: I recommend using hot melt glue. It sticks well to other plastics yet it is relatively easy to remove without damage.

author: vikpc
author_rank: Newbie
timestamp: January 29, 2014, 02:18:34 pm
content: hi! i use thisfor fixing wires and some fast components fixing... it starts in 5-10sec... and not have power wires! very useful.

author: Rufus
author_rank: Super Contributor
timestamp: January 29, 2014, 03:43:15 pm
content: Quote from: luky315 on January 29, 2014, 01:17:06 pmSo I clip my insulation tester on a bit of hot melt glue stick which has been kicking around at the back of my bench for at least a couple of years - didn't even clean the surface. The gap between the croc clips was less than 10mm.The tester reads overload, greater than 1T ohm at 5kV.

author: SeanB
author_rank: Super Contributor
timestamp: January 29, 2014, 07:22:05 pm
content: Cook it and then leave in a humid place for a month then try again. Good luck getting more than 10M out of it.

author: pickle9000
author_rank: Super Contributor
timestamp: January 29, 2014, 07:48:54 pm
content: If you have a pcb preheater use that before applying the hot glue.If you want it be be ultra long lasting use a clear 100% silicone, takes overnight to set up but bonds really well to surfaces. To make the silicone more rigid I use place a small square of clear polycarbonate on the surface.

author: Rufus
author_rank: Super Contributor
timestamp: January 30, 2014, 12:30:59 am
content: Quote from: SeanB on January 29, 2014, 07:22:05 pmI left it in a submerged place for more than 7 years and get much more than 10M out of it :-https://www.eevblog.com/forum/projects/(tips)-strengthen-the-diyself-made-hook-probe%27s-join-using-hot-glue-gun/msg67507/#msg67507The lid has rusted and most of the water has now evaporated. The resistor today still measures 10.15M.

author: aargee
author_rank: Frequent Contributor
timestamp: January 30, 2014, 02:37:51 am
content: Funny, when i saw the title I instantly thought "invariably something else".Hot melt glue doesn't like Australian summer heat (I guess not a big problem for this application).The glue sticks are not of a consistent compound depending where you source it.I have had HV problems with Hot melt where the glues involved created internal HV carbon pathways, breaking down.Great for crafts and the "gaffa tape / fencing wire / baling twine" type MacGyver fix.Most wiring fix in lace type adhesives I've seen are a Cyanoacrylate with filler.

author: Rufus
author_rank: Super Contributor
timestamp: January 30, 2014, 02:55:11 am
content: Quote from: aargee on January 30, 2014, 02:37:51 amPart of the problem is there are many types of hot melt glue. My experience is with cheap standard temperature Polyolefin Copolymer sticks, white/translucent, feel slightly waxy.

author: BravoV
author_rank: Super Contributor
timestamp: January 30, 2014, 02:58:22 am
content: Quote from: Rufus on January 30, 2014, 12:30:59 amAh.. just remembered that old thread.Rufus, take a photo of that jar please, I guess it looksdisgusting... interesting.

author: Rufus
author_rank: Super Contributor
timestamp: January 30, 2014, 03:14:36 pm
content: Quote from: BravoV on January 30, 2014, 02:58:22 amFirst a picture of the insulation tester clips and bit of hot melt stick which measured > 1T ohm @ 5kV.Then top of the jar, the resistor in its hot melt coating, and the resistance measured across the wires.The jar started about half full of water with a couple of tablespoons of salt added, only in the last year or so did the water level start dropping significantly. The salt water does something to the hot melt, early on there were some debris in the water like the hot melt was shedding thin skin.

author: BravoV
author_rank: Super Contributor
timestamp: January 31, 2014, 12:27:29 am
content: 7 years in salt water with constant exposure of uv light from the sun + daily thermal cycle, quite impressive imo.Thanks Rufus , that post is now bookmarked for future reference.

author: JBeale
author_rank: Frequent Contributor
timestamp: January 31, 2014, 12:42:35 am
content: Quote from: luky315 on January 29, 2014, 01:17:06 pmThat may be specific only to some kinds of hot-melt glue.http://en.wikipedia.org/wiki/Hot-melt_adhesivelists 12 broad categories of base materials (EVA copolymers, Polyamides, Polyesters, Polyurethanes, Styrene copolymers, Polycarbonates, Fluoropolymers etc.) and 10 categories of additives. In some cases hygroscopic materials are intentionally added to allow microwave heating.

author: scientist
author_rank: Frequent Contributor
timestamp: January 31, 2014, 12:55:28 am
content: Use 20-minute epoxy and mix it correctly so it is stable, yet flexible. Hot glue will always disappoint.

author: LukeW
author_rank: Frequent Contributor
timestamp: January 31, 2014, 03:09:30 am
content: I'm not surprised there are HV issues with the hot melt glue. But I wouldn't use it for HV! It's great for general purpose applications at low voltages where it's not expected to fly men to the moon, and you want something cheap and convenient where using specialist glues or sealants is not financially justified though

author: sacherjj
author_rank: Frequent Contributor
timestamp: January 31, 2014, 04:49:01 am
content: Quote from: pickle9000 on January 29, 2014, 07:48:54 pmMake sure the silicon won't be corrosive. It needs to be neutral cure. Mose RTV Silicone will release acids. Make sure to look for neutral cure.Hot melt is only OK if you need it to last under a year. But you can use dabs of hot melt to hold a component so silicone can cure. Good silicone is a 20+ year solution.

author: jeremy
author_rank: Super Contributor
timestamp: January 31, 2014, 05:04:56 am
content: ok guys, just went out and bought a bosch hot glue gun with official bosch sticks (all the cheapies had a yellowy tinge, the bosch ones are definitely all semi-transparent PVC)Now works beautifully on soldermask!Thanks for the tips all. I am still very curious about UV epoxies however, can they be cured in a reasonable amount of time with a $5 UV torch from ebay?

author: scientist
author_rank: Frequent Contributor
timestamp: January 31, 2014, 06:09:00 pm
content: Getting the UV epoxies isn't worth it, just get a bottle of $5 20 minute epoxy and you're good to go. A good source is here:http://www.radicalrc.com/category/Epoxy-390

author: TerraHertz
author_rank: Super Contributor
timestamp: February 01, 2014, 09:27:26 am
content: Quote from: pickle9000 on January 29, 2014, 07:48:54 pmThis. If I'm hot gluing something where the glue doesn't penetrate/stick well from the gun, I preheat the objects with a hot air gun. THEN it works.

author: lapm
author_rank: Frequent Contributor
timestamp: February 01, 2014, 05:55:20 pm
content: My personal experience on high temperature hot-glue is that its not very good. Its very very dependent on temperature its on. Try to mix some room temperature wires in it and its cools down fast below usable window.The little i have used two component epoxy, that's has worked much better. It actually heats up on hardening due chemical reactions.

author: sacherjj
author_rank: Frequent Contributor
timestamp: February 01, 2014, 06:12:27 pm
content: Quote from: jeremy on January 31, 2014, 05:04:56 amNot sure about curing with a $5 UV torch. Most UV is not an epoxy (i.e. not a 2 part), just a single liquid with a vary viscosity.For high temp hot melt, we have been using the 3M gun. It has 5 modules that are essentially various power resistors. 1 being largest resistance for lowest temp and 5 being direct short for highest temp.Hot melt is ALL about heat transfer. If you are hitting a surface that can transfer heat to a high thermal mass, you will freeze off the surface before it bonds. Preheating is a great idea in that sense. An example of this is 1/4" thick plate glass. Don't be skimpy with the glue. More glue is more heat.

author: SArepairman
author_rank: Frequent Contributor
timestamp: February 01, 2014, 06:21:35 pm
content: so does anyone have a electronics safe brand of hot glue?something known good that will have a nice high impedance.and how about a good brand of UV cure glue? Deal extreme has one but I am skeptical.

author: Frost
author_rank: Regular Contributor
timestamp: February 01, 2014, 06:31:51 pm
content: Quote from: SArepairman on February 01, 2014, 06:21:35 pmIn the US?http://www.masterbond.com/products/uv-curable-systems

author: SArepairman
author_rank: Frequent Contributor
timestamp: February 01, 2014, 06:57:35 pm
content: how about good quality glue sticks? btw do you know what a good retailer of that glue is? I don't like quotes.And when aargee mentioned in this thread cyanoacrylate being used with filler is used to hold wire down, what filler? I have milled fiber glass, I never thought to use it with super glue before.

author: sacherjj
author_rank: Frequent Contributor
timestamp: February 01, 2014, 08:12:18 pm
content: Quote from: SArepairman on February 01, 2014, 06:21:35 pmWe purchased a few types of 3M hot melt glue sold by Digikey. They are used for electronics potting. 3M 3748 worked well and is made for dropping on electronics. In black or creme:http://www.digikey.com/product-detail/en/3748-Q-BLACK/3M10542-ND/2699976We are using this gun, but I believe we got it somewhere for under $400. Or close to $400.http://www.digikey.com/product-detail/en/POLYGUN-EC%20JET%20MELT%20APPLI/3M6423-ND/1306100Note that unlike low heat hot melt, most higher heat guns are brand specific, and/or use bulk melters and pumps heated tubes, etc.We have used mostly Dymax branded UV adhesives. Ellsworth.com is a good place to look for adhesives. But we are not really trying to support or pot anything, we are making a gasket seal between glass and hard to bond plastics. If hot melt will work for you, it will be 1/2 price or less with brand name hot melt (like 3M) down to almost a magnitude cheaper with off brand hot melt. Dymax BlueWave lamp for curing is going to run near $4k. Might get cheaper with a conveyor through system. That is what we are looking at.Edit: Yeah, the Poly Gun on Amazon is $350:http://www.amazon.com/3M-Scotch-Weld-Hot-Melt-Applicator/dp/B001HON4C4/ref=sr_1_4?ie=UTF8&qid=1391285660&sr=8-4&keywords=3m+polygunThere are some cheaper 3M guns that handle the 5/8 x 8 in sticks, but I don't know how you set the heat on those. Make sure the heat matches the stick heat specs. With 3M that is 1-5 system. We got the 5 heat setting gun, because we needed to run a bunch of tests by hand, before we purchased our glue tank and hot melt application xy robot system.Looks like this one:http://www.amazon.com/3M-Scotch-Weld-Applicator-Quadrack-Converter/dp/B001AO27V0/ref=sr_1_1?ie=UTF8&qid=1391285660&sr=8-1&keywords=3m+polygunis $150. It says not to be used with the low temperature glue, so it is probably good for 4-5 setting sticks like the one mentioned above.

author: jeremy
author_rank: Super Contributor
timestamp: February 01, 2014, 11:07:54 pm
content: so it looks like all of the "electronics" hot glue is polyolefin based. Anyone got a good source for 11mm sticks of that?http://www.digikey.com/Web%20Export/Supplier%20Content/3M_19/PDF/3m-hotmelt-datasheet.pdfThe bosch ones I have are awesome, but they are PVC so no guarantees on the specs

author: jeremy
author_rank: Super Contributor
timestamp: February 01, 2014, 11:15:46 pm
content: also, may be of interest:http://shuttersparks.blogspot.com.au/2011/03/mystery-of-non-waterproof-hot-glue.html