[sdiy] PCB heat simulations?

[David G Dixon]

If you are going to put holes in, you should put some small holes around the
hot component on the same board, and in the boards above and below, to
induce convection draughts. 

> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl 
> [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of 
> Mattias Rickardsson
> Sent: Wednesday, November 13, 2013 1:09 PM
> To: Ian Fritz
> Cc: synthdiy diy
> Subject: Re: [sdiy] PCB heat simulations?
> 
> On 13 November 2013 21:56, Ian Fritz <ijfritz at comcast.net> wrote:
> > Not exactly what you are asking, but you could make a 
> little chimney 
> > above your hot spot to move most of its heat away from the board.
> 
> That's one of the things I'm considering - not a chimney per 
> se, but a hole in another PCB placed above the hot component. 
> The question is if it helps much. If there is considerably 
> more convection upwards from the hot component, it will have 
> effect to place the hole there. If the heat & convection 
> forces are spread more evenly over the PCB area, it will have 
> less effect, and other hole positions will not be better either.
> 
> Those are some of the behaviours that it would be nice to get 
> a gut feeling for. :-)
> 
> Anyway, thanks also to Achim for some good advice!
> 
> /mr
> 
> 
> > At 03:08 AM 11/13/2013, Mattias Rickardsson wrote:
> >>
> >> Hi all,
> >>
> >> is there any good tool (or rules of thumb) when it comes to 
> >> understanding the passive cooling airflow around PCBs?
> >>
> >> If I have a horizontally mounted PCB with some components 
> that easily 
> >> reach far above ambient temperature, how can I know if there is a 
> >> convection going on above those components? If I knew 
> that, I could 
> >> choose to design the surrounding construction in a 
> suitable way for 
> >> the airflow - or if I knew that there is no convection I 
> could skip 
> >> those thoughts altogether and focus on other means of heat 
> transfer.
> >>
> >> I googled a bit but never found a simple visualisation 
> tool or other 
> >> simple rule of thumb of these *very* un-simple physical phenomena.
> >> Given how complicated they are, I expect that a few 
> advanced experts 
> >> are the only ones that can come close to understanding them, but 
> >> theory should have trickled down to some handy design 
> rules after all 
> >> these years. For instance, if one of my 1 cm * 1 cm 
> components are 50 
> >> degrees C and the rest of the PCB is at room temp, what 
> happens with 
> >> the air above it? What temperature difference (or power draw) is 
> >> typically needed to give convection?
> >>
> >> Any pointers are welcome! :-)
> >>
> >> /mr
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