Potting compound for building a tank light

I don’t know about any brands but I would recommend something that’s not just for waterproofing but also thermally conductive because there will be no air touching your components, so you need the potting compound to move heat away rather than insulate it.

No. I have Kafuter K-5024K and don’t recommend it because it separated into fractions, one white and thick and the other watery and translucent. I mix it up a bit before application and it works for me, but that’s not how it should work. I’ve seem many people recommend Fujik.

Isn’t air a thermal insulator already?

Oh dear, has it never occurred to you to search for “potting compound” ?

The proper stuff for the job.

Now, if you live in the UK, you can have almost anything available, in a couple of days, because we still do serious electronics here, and have a robust supply chain (for now).

E.g. https://uk.rs-online.com/web/c/adhesives-sealants-tapes/adhesives-glues/potting-compounds/

If you want to try to bodge things up with totally unsuitable “cheap” (not actually, when they fail) materials, maybe from a DIY warehouse, particularly any cheap silicones (more thermal insulator than conductor) that smell of vinegar and will corrode everything, eventually, well, you’ve got it wrong.

The thing is, that mixing up a batch of a good potting compound, even in a small sachet, is expensive, and you had better be prepared to use it wisely, which means more than just one hobby experiment. If this interests you, then you will need to do your own research, choose the materials that work for you, are available, and that you can afford (i.e. not only delivered in 1Kg tubs MOQ, like the professional ones).

Develop your own methods, experiment, don’t expect to get it right first time, or have your hand held.

Edit: did I also mention time and temperature ? Fundamental.

And it is mostly unnecessary, except for those of us who have an application for an assembly that can survive extreme G-force, repeatedly. Some do, and will pay for that assurance.

Pretty sure the OP wants to use his torch as a shotgun light, so extreme G-force survival is necessary for him.

I wouldn’t be asking if I actually found an answer. I live in SEA, which means it’s way harder to look for things like this and most of the time the only way is to ship from China since shipping from Euro or US is a pain. I’ve dug up all the old BLF posts as well about potting and non of them talk about making a light durable and most of them talk about heatsinking so I wanted to make sure.

Yes, I do know that real potting compounds are pricey, which is also one of the main reason why I’m asking as well.

Well, I would want to use it as a weapon light if it worked, so…

I live in SEA :question:
It would a little help, if you can tell us in which country do yo live.

In generall any epoxy glue without reinforcement particles should do the job.
I potted a lot uf switched buck/boost drivers with frequency up to 1.2MHz! without problems.

Today I buy epoxy for large jobs per kg, since its a fraction in price. (25 - 30 usd/kg)

SEA = SouthEast Australia?

True.
With Marine epoxy being slightly flexible in relation to rigid/crackable in extremes STD Epoxy blends.
We used to “stiffen” it up with Talcum powder to give it some body,
and just watered down with 50/50% thinners for soaking in before top layers.
(I had 2 x Timber yachts.)
Preserving carved Teak and Mahogany mainly.

I’ll have a think about this. What do you actually have available ? I have no idea about what is common in SEA ?

You need to be looking at either elastomer’s that set (electronic materials mostly).

Or rigid stuff like acrylic and epoxy resins with fillers (boat building). Which, I would not recommend as a starting point, if heavy recoil is involved.

Don’t touch the silicone RTVs unless they are really good ones. Dow Corning etc. Not tubes from the DIY warehouse.

Most of the hardware stores here carry mostly chinese stuff or stuff from the US (local Ace Hardware) which is not going to be cheap, obviously. So I just mostly depend on chinese sites like banggood, aliexpress and the others. I found some Arctic Alumina thermal adhesive locally but holy shit it costs USD$45 for 5g.

I just ordered some Fujik to try it out though so I’ll see how it goes when it’s here.

EDIT: Just for some context on why I keep saying it’s hard to find things here, I used to do some work that requires the material and hardware be imported from the US, which is the only place available. Heck, even painter’s tape is a god damn hassle to look for. Yea, painter’s tape. My local Ace Hardware sells that for USD$20.

Honestly, I’m not very confident in using epoxy or waterweld to pot the M1 that I’m going to build since I have a feeling it’s going to get pretty hot with the Luxeon MZ on a FET driver and also bypassed springs. Just worried I’ll insulate the thermal path. I can probably try that in another light I have to see how well it works though.

If you’re thinking about using a silicone-based material, put a little on a piece of cardboard and see if you can smell vinegar (also known as acetic acid). If you smell vinegar, don’t use it, it’ll corrode your electronics.

A lot of the cheap silicones produce acetic acid as a by-product when curing. That’s especially true for the ones you’ll see in a DIY store.

There are better silicones that produce non-corrosive by-products like alcohol or acetone, but you’d need to make sure they didn’t come in contact with anything that might be susceptible to degrading or dissolving in those solvents. Not usually a problem with electronic stuff, but just so you know.

I’ve never potted anything, so unfortunately I can’t recommend any particular potting material to use. I just wanted to add some detail on the silicone possibility.

It’s a fluid though so it cools by convection.
Air will keep components on a pcb much cooler than covering them with some non-conductive plastic or material.

I doubt convection is a thing when there’s so little air inside a waterproof M1, you can’t get a flow going and there are no real differences between one side of the minuscule air pocket and the other.

It doesn’t matter, simply the fact that the particles can move means that heat will be transferred to all the other metallic surfaces that the air is in contact with.
This is exactly why it is beneficial, because there is “no real difference between one side and the other”
If it was filled with a solid insulating material there would be a huge temperature gradient inside the light.
The goal of cooling is literally to reduce the temperature gradient so that there is no real temp difference, as you just said.

I was just about to post this question also. I need potting for three reasons.
1.) to help bleed heat out of the electronics.
2.) to water proof the electronics, especially those with some kind of USB port.
3.) strengthen the components like USB ports that are prone to breaking loose.

Any one know of a product that can do all three? I’m trying to get up to speed on newer work lights like Acebeam, Mateminco TK01, etc but port connections like to break off the boards and leak in water.

I know MG chemicals makes good solder pastes so I would assume they know their stuff on electronics assembly potting compounds too.
https://www.amazon.com/MG-Chemicals-Thermally-Conductive-Encapsulating/dp/B008UH4CRM
Reviews seem good.

+1

I’d stick with a good thermally-conductive epoxy encapsulant.
I think there are some good options available from Stycast (now owned by Henkel/Loctite) as well.

You are asking for three different things, which I think need three different materials.

1) Bleed heat out ? I don’t think any sort of encapsulation or potting will help much, more likely to insulate, you need to address the basics first.

2) Waterproof electronics ? This is exactly what conformal coating is for. I don’t understand why is is never mentioned here, it is compulsory for everything that I design.

3) Strengthen weak connectors ? Glue them up with suitable polyurethane or epoxy materials (no, not hot glue). Preferably polyurethane that can be easily cut away if the connector does eventually fail and needs to be replaced.

In summary, potting is not what you need. It’s purpose is primarily to strengthen the device against shock and vibration, secondarily to protect from humidity or other contamination, or, quite commonly, to render the device un-repairable (much more money to be made selling complete assemblies than encouraging simple component replacement) and to make reverse-engineering more difficult.

Which is why most potting compound is black, rather than naturally transparent.

Potting is also an easy consistent way to mass-produce cheap things that might benefit from it,or simply to make them un-repairable. Whereas precise glueing of key components, application of conformal coat, possibly with e.g. latex masking over connectors and test points etc. thereby creating a repairable, inspect-able part, is expensive, in skilled labour costs.