PCB mounted to aluminum enclosure without standoffs

[me171722]

Hello,

I was wondering if anyone can think of a reason why this is a bad idea as I project that has a board that gets very hot and was thinking having more surface area between the board and case (heatsink) would be good.

I feel like I am missing something obvious but can't think of a reason why standoffs are needed assuming one side of the board is bare

Thanks

 

[3DDave]

It's commonly used with single-sided-boards. Some boards are backed with aluminum, making for a challenge to hand solder.

If there are high voltages involved you need to make sure not to electrocute users say from corrosion and moisture.

 

[me171722]

Thanks for letting me know its common as I didn't see any issue with it but struggled to find an example . The high voltage warning is appreciated as well

 

[Compositepro]

Unless you use a heat transfer paste you will still have an air gap. You also must deal with differential expansion.

 

[itsmoked]

Got a picture of the setup?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[IRstuff]

"very hot" means how many degrees temperature rise?

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[chicopee]

If soldering with aluminum is a challenge for hand solder per me171722, then use copper as backing material but I would have the copper block machined to have ribs instead of a solid block.

 

[drawoh]

me171722,

Standoffs are an excellent way to assure that your components leads do not touch the aluminium structure. This may not be an issue if your board is all surface mount and everything on the bottom is ground. If anything on the bottom is anything other than ground, you will have to cut the aluminium away to prevent shorts.

A nice advantage of standoffs is that you do not have to cut stuff away to prevent shorts, and you are left with a nice Faraday cage.

--
JHG

 

[CWB1]

I usually leave enclosure design for the EEs, but when I get sucked into it I prefer to mount boards along the outer edge with features molded or cast into the enclosure itself as a cost/labor savings and quality improvement. In most cases I've come across there's no downside nor are any significant constraints placed on board design.

 

[mighoser]

Use a thermal pad or gap pad.

https://www.henkel-adhesives.com/us/en/products/thermal-management-materials.html

________________________________________
Mitsubishi Chemical Advanced Materials

http://www.mcam.com