Potting compound for building a tank light

Enderman · 2018-10-14T18:40:10.000Z

Jack Kellar:

Enderman:

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.

Isn’t air a thermal insulator already?

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.

Jack_Kellar · 2018-10-14T18:45:57.000Z

Enderman:

Jack Kellar:

Enderman:

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.

Isn’t air a thermal insulator already?

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.

Enderman · 2018-10-14T19:57:24.000Z

Jack Kellar:

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.

texas_shooter · 2018-10-14T21:06:00.000Z

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.

Enderman · 2018-10-14T21:53:46.000Z

texas shooter:

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.

freefly · 2018-10-14T22:23:31.000Z

Enderman:

I know MG chemicals makes good solder pastes so I would assume they know their stuff on electronics assembly potting compounds too.
Amazon.com
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.

Tom_Tom · 2018-10-15T00:02:20.000Z

texas shooter:

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.

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.

Enderman · 2018-10-15T00:04:08.000Z

Tom Tom:

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, etc. thereby creating a repairable, inspect-able part, is expensive, in skilled labour costs.

Potting does literally those three things.
It is thermally conductive to help cool the electronics, it is waterproof, and it is a solid which strengthens all components against shock and vibration.
Of course there is some potting material which is not thermally conductive, which is why I recommended buying one which is.

You do not need a separate material for separate tasks, this is the year 2018 and humans have evolved a lot.

Tom_Tom · 2018-10-15T00:19:46.000Z

Enderman:

Potting does literally those three things.
It is thermally conductive to help cool the electronics, it is waterproof, and it is a solid which strengthens all components against shock and vibration.
Of course there is some potting material which is not thermally conductive, which is why I recommended buying one which is.

You do not need a separate material for separate tasks, this is the year 2018 and humans have evolved a lot.

Potting is a brutal thing to do to a circuit, unless you don’t care to ever look at it again. Just toss it if something goes wrong. It is generally a cheap solution for cheap things, that don’t justify any skilled workmanship.

As for “thermally conductive” compounds, once you study the numbers you may find that it just means “not as thermally insulating as the worst compounds, but still not great”

There is also a halfway-house using stuff like Raytech Magic Gel, which is not bad.

The OP is looking for ghetto ways of potting using locally available materials, at affordable local prices. I can’t really advise, because I’ve never been in that situation.

If the primary reason is for shock and vibration resistance, then yes, potting is the best idea.

Enderman · 2018-10-15T00:27:40.000Z

Tom Tom:

Potting is a brutal thing to do to a circuit, unless you don’t care to ever look at it again. Just toss it if something goes wrong. It is generally a cheap solution for cheap things, that don’t justify any skilled workmanship.

As for “thermally conductive” compounds, once you study the numbers you may find that it just means “not as thermally insulating as the worst compounds, but still not great”

There is also a halfway-house using stuff like Raytech Magic Gel, which is not bad.

The OP is looking for ghetto ways of potting using locally available materials, at affordable local prices. I can’t really advise, because I’ve never been in that situation.

If the primary reason is for shock and vibration resistance, then yes, potting is the best idea.

Potting is what you do when you want something to last as long as possible in the harshest of conditions.
Anyone who knows what potting is knows that if something dies you basically have to replace the whole circuit, that’s not a concern because electronics circuits last decades when designed correctly.
Also the point of potting is prevention.
That means you sacrifice repairability in order to make it last longer so that you don’t need to repair it.

2) Not all potting is permanent, some can be removed, as seen here inside my hellfighter:

3) thermally conductive depends on which one you use.
The one I linked earlier is close to 1W/mk which is many times higher than air.
It is not the same as a thermal paste which is 5-10W/mk but still good enough for preventing overheating of the PCB components.

Potting is good for waterproofing, cooling, AND shock resistance, assuming you buy one which is designed for all 3.
Not just shock resistance.
Please do some research.

KawiBoy1428 · 2018-10-15T00:49:57.000Z

I use Stycast when it’s in the shop, but I also use MG Chemicals. Both work excellent. You have to watch what you use, some thermal epoxy can be electrically conductive, I bricked a Convoy L6 once.

This is what I use from MG Chemicals

amazon.com

MG Chemicals 832TC-450ML Thermally Conductive Epoxy Encapsulating and Potting...

MG Chemicals 832TC-450ML Thermally Conductive Epoxy Encapsulating and Potting Compound, 15 oz Kit, Black: Epoxy Adhesives: Amazon.com: Industrial & Scientific

Macka17 · 2018-10-15T01:35:04.000Z

Why don’t you just send an email to a “good” name torch MFG.
and ask them what. if anything they use. (Tech Services dep’t.)
They can only tell you to piss orft.

Then we ALL may just learn something new.
Most I’ve seen have been either grey or black.

The old “tar” chips we used to get from road laying crews
we used for everything.
Melted, it stuck everything together. and free hey.
It was great to chew on too. very tangy.

Barkuti · 2018-10-15T01:41:43.000Z

Stars-922 may be a nice option: https://www.ebay.com/itm/HY410-STARS-922-Thermal-Compound-Sink-Silicone-CGPU-Silikon-Grease-Glue/163170389586

Takes a little while to harden, it depends on volume to area ratio. No volumetric shift. Once hardened remains slightly fexible but has adequate stiffness. I used this compound to stick an Omten 1288 inside an SK98 pogo switch retaining part whose slot is for bigger switches, like this one: http://kaidomain.com/S024498-DIY-LED-Flashlight-Reverse-Clicky-Switch-14_8mm-x-9_6mm-for-LED-Flashlight. After hardening took the pogo retainer out of my vise and could easily sand down the protruding plaster excesses. Worked like a charm.

Can be removed later with a bit of patience and some spirits help: alcohol, white spirit, gasoline, etc.

Worth a try imho.

Cheers :-)

tvizk · 2018-10-15T02:33:01.000Z

Macka17:

Why don’t you just send an email to a “good” name torch MFG.
and ask them what. if anything they use. (Tech Services dep’t.)
They can only tell you to piss orft.

Then we ALL may just learn something new.
Most I’ve seen have been either grey or black.

The old “tar” chips we used to get from road laying crews
we used for everything.
Melted, it stuck everything together. and free hey.
It was great to chew on too. very tangy.

Well, I do know PFlexPro uses Stycast (can’t recall product number) which isn’t available in small quantities.

Boaz · 2018-10-15T02:34:10.000Z

How about urathane that they use to put windsheilds in with ? Pretty tuff stuff

texas_shooter · 2018-10-15T04:26:37.000Z

Thanks for the input. I work in Texas with heat, rain, humidity and things that fly across parking lots. Big fan of the P60 from SolarForce with premium Pflexpro dropins. These could spend two days in the pool with out worry of water getting in or parts breaking. I’m moving into 20700 and 21700 lights for better run time and output. Those USB style charging port are the new weak points. I’m looking at the Mateminco TK01/Astrolux FT01 as a possible replacement along with the Wuben A21. I’ve got no illusions that they might not make the grade. I think potting will give them a better chance. Once again thanks for the help.

joechina · 2018-10-15T16:33:27.000Z

I think Dale used Sugru to secure things in the driver cavity.
It is a self curing silicon.

tvizk · 2018-12-20T15:14:49.000Z

So, I made another M1 with the exact same parts since I gave away the first one for the other guy to abuse. This time, I mixed some Fujik with some 8w/mk thermal paste and applied that onto the driver covering the components. On the solder joints, I just covered it entirely in Fujik. I’ll try to get some abuse footage to see how well it holds up when I have the time.

Jack_Kellar · 2018-12-20T15:20:07.000Z

tvizk:

So, I made another M1 with the exact same parts since I gave away the first one for the other guy to abuse. This time, I mixed some Fujik with some 8w/mk thermal paste and applied that onto the driver covering the components. On the solder joints, I just covered it entirely in Fujik. I’ll try to get some abuse footage to see how well it holds up when I have the time.

Nice, looking forward to it already :+1:

teacher · 2018-12-20T16:43:33.000Z

Jack Kellar:

tvizk:

So, I made another M1 with the exact same parts since I gave away the first one for the other guy to abuse. This time, I mixed some Fujik with some 8w/mk thermal paste and applied that onto the driver covering the components. On the solder joints, I just covered it entirely in Fujik. I’ll try to get some abuse footage to see how well it holds up when I have the time.

Nice, looking forward to it already :+1:

Yep, looking good.
I had no idea Duracell sold 18650’s.