Potting with hot glue? - Page 1
Forum section: electronics / beginners

author: kalel
author_rank: Frequent Contributor
timestamp: December 27, 2017, 03:48:48 pm
content: I'm curious as to whether hot glue can be used as a potting compound, in such applications where high temperature is not expected. This is just pure curiosity, I know that existing 2 component or other potting compounds made for the purpose would provide the best result for any standard applications.I know that viscosity could be an issue, that is, while it's falling down and cooling, it might not flow properly and cover everything. Is there a way to solve this? Flowing at somewhat higher temperature, some type of reflowing it, etc.Another issue is obviously temperature. Hot glue will melt at a certain temperature (e.g. if a short happens). Is it possible for the melted glue to cause an issue, e.g. become conductive? Although, at this point a short or other failure has already happened to cause the overheating.

author: Belrmar
author_rank: Regular Contributor
timestamp: December 27, 2017, 03:52:42 pm
content: it depends a lot on why would ou pot your electronics, if its for waterproofing it might be good enough but if you want to protect your trade secret from reverse enginieering its basically a piece of s****

author: kalel
author_rank: Frequent Contributor
timestamp: December 27, 2017, 03:55:43 pm
content: Quote from: Belrmar on December 27, 2017, 03:52:42 pmNo, definitely not protecting from reverse engineering (or obviously high temperatures) in my case. Just curious if it's usable.It's almost always easy to take off, smaller amounts of hot glue comes off really easily with alcohol, and large amount would need some heating.

author: wraper
author_rank: Unknown
timestamp: December 27, 2017, 04:09:22 pm
content: No it's not suitable. Won't last a year or two before starting coming off. In outdoor conditions will fail to protect during first winter.

author: kalel
author_rank: Frequent Contributor
timestamp: December 27, 2017, 04:23:30 pm
content: Quote from: wraper on December 27, 2017, 04:09:22 pmIt's a shame, it would have been I would guess the by far cheapest solution. But I wasn't exactly convinced that it would work well, that's why the question.

author: Ysjoelfir
author_rank: Frequent Contributor
timestamp: December 27, 2017, 05:50:26 pm
content: I guess it highly depends on the glue you use. I have used hot glue very often for sealing purposes and many other things. It always depends on the type of glue you habe - cheap glue doesnt work nearly as good as good but pricey glue. My personal experience is that the "sticky", softer gluesticks are better for sealing as the harder, more brittle ones, also, black gluesticks usually work better for sealing as "clear" ones. at least that is my experience.

author: TimNJ
author_rank: Super Contributor
timestamp: December 27, 2017, 07:23:32 pm
content: The hobby grade opaque white stuff won't do very good. That's generally regarded as low-temperature hot-melt glue. The "good stuff" is generally the high-melting point glues used in industrial applications.I use3M 3779 Hot Melt Adhesive. High strength, high temperature stability..I think that's a pretty popular one, but it's not cheap and you need a 5/8" applicator which only a few companies make, to my knowledge. I have a 3M Polygun, but it was still pretty expensive and I got it used on eBay.If you are interested, take a look at some of these offerings:https://surebonder.com/collections/electricalThey have pretty affordable applicators too.

author: KL27x
author_rank: Super Contributor
timestamp: December 27, 2017, 09:43:02 pm
content: There's a bit of absolutism in the answers.The reason for potting things varies. If it's to keep fragile connections and wires from breaking, it can work perfectly for that, for many years.QuoteIs there something that happens at low temp?For hundreds of thousands of years, humans used simple resources like tar, beeswax, and sap/rosins for reliably connecting and binding things, well before bone and fish glues were invented. These early glues have some similarities with hot glue. One of the most obvious ways to make hot glue more durable is to add fiber to it to help bind it together. To keep a joint adhered, one can keep pressure on the connection (by wrapping/binding with perhaps fibers+glue where possible). It is also sometimes possible, if/where it eventually fails by loss of adhesion, to use PVA glue (Elmers or wood glue) to glue the perfectly shaped hot glue interface back together.A couple ways I use hot glue for electronics:Small proto circuitry. So if I were to need a small circuit with say a few wires going in, and a few wires going out, I might take a thin piece of lamination (like thin FR-4 or even single-sided copper clad) and cut out 2 pieces that are large enough to totally cover the entire protoboard circuit. Shape them the way I want and route the wires how I want. Then cover the entire circuit in hot glue and slap the laminations over it on either side until glue oozes out the seams. Trim as needed.Strain relief and waterproofing of a cable going into a plastic/metal housing. What I will do is wrap a cord/string around the cable while adding hot glue. The string is under tension, so it absolutely can't slip over the cable sheathing. The hot glue glues the string to itself, so it absolutely can't lose tension. Once you have your bulge on the one side, the wire can't pull out. Glue it to the housing, then cord wrap the other side with more string and glue and a good glob of glue. Once this is on, it is not coming off without time and tools and directed deconstruction.

author: james_s
author_rank: Super Contributor
timestamp: December 27, 2017, 10:40:46 pm
content: If you want to protect your trade secret from reverse engineering then any form of potting is useless. I have reverse engineered a number of potted assemblies, the potting is a minor inconvenience at best. If anything the potting makes me all the more curious what's in there.

author: wraper
author_rank: Unknown
timestamp: December 27, 2017, 10:44:15 pm
content: Quote from: KL27x on December 27, 2017, 09:43:02 pmIt becomes hard and just comes off easily even without any mechanical impact. You could try it yourself, put a blob of hot melt on some surface, put it in the freezer. Then take out and try to remove it while cold. If it will still hold, repeat a few thermal cycles.