Adhesive sealant or epoxy to glue heatsink with box ? (and keeping it waterproof)


Doing several faux drive assist with an external alu heatskink.
I aldready tried adhesive sealant (not 3M 5200 but CC 2000 HM, works well but not very clean after.

I tried also epoxy glue (see picture below), it seems waterproof (30m under water test), and very easy to use, what is the disadvantage using epoxy instead of adhesive sealant (many of you recommend 3M 5200, but quite expensive)


Epoxy on plastic is not the best adhesion, you might get some problems with the temperature cycling that will occur. 3m 5200 is a bit more flexible and will take this better.

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There are loads of different epoxies. Some specifically designed for different plastics, metals and composites. Some epoxies go past 250°C so heat really isn’t an issue. I used one of the jbweld products and pushed the heatsink past 100° and it didn’t affect it at all.

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It’s not the heat that’s the issue but the thermal expension and related stresses combined with a lower adhesion. Sure there are flexible epoxies, thermal epoxies and such but in general they are not the best for plastics.


These housings are polycarbonate which epoxy actually works very well on. In addition the thermal expansion will have no effect as one of the best methods for attaching heatsinks to chips is with thermal epoxy. I’d actually argue that based on the two materials involved, epoxy would be the better solution.

3m 5200 also has a max temp of 88°C which means it shouldn’t be used for heatsinks really.

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Now i don’t need to check my housing material since you know which housing i have!
Thanks @Jezza :pray: :smile:

Last I checked it was Nicolas that started the thread and asked the question… His housing is polycarbonate. My response to you was simply in connection to his housing. As for your housing, I have no clue which you are using…

I thought the question was a general one. My bad :wink:

Thanks for your answers, I haves three boxes, one with epoxy and two with sealant, time will now tell which one is the better :wink:


I’m using sikaflex 291 to bond a sandwich of aluminium flat bar to a black pelican case.
Probably only 10 sea trials but so far so good.

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Your example is not the best since OP’s question was regarding water tightness, the adhesive is for sealing the enclosure vs heatsink. I can’t see the CPU thermal interface being made of ABS, PC, ASA or other typical enclosure materials, that would be horrible for the cooling performance.

That example was regarding thermal expansion with epoxy aluminium interface…

I would bolt it to the box and use thermal paste make sure the heat conductivity is good.

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