Lpc2000

Don Ingram wrote:

>
> >>>An oven would be nice to have though for larger boards and smaller
> >>>series. I have tried to find one with a fan in Sweden but not found a
> >>>suitable one yet. Instead I am thinking about rebuilding one and 
> putting
> >>>in quarts IR elements and control logic to get faster ramp up then it
> >>>has standard. As always time is my enemy... ;-)
>
>
> The other thing to look at is the heat distribution in the oven, it 
> might give
> you a surprise...
>
> Place a sheet of printer paper in the oven similar to your larger PCB 
> panels and
> do a bake run.  The pattern on the paper will give an indication of 
> the effect
> of the elements.
>
> Generally the area around the edges will be pretty cold and the middle 
> a bit
> uneven due to the lag in heating the sidewalls & generally losses to 
> ambient.
>
> Attach some alfoil ( shiny side inwards ) to the edges of the oven 
> rack so that
> there is a bit of a gap ( 5mm or so ) between the alfoil & the side 
> walls. Do
> this at the front as well leaving a portion as a window.
>
>   Cook another sheet of paper & you will be surprised at the much more 
> even
> heating pattern due to the decreased losses & the additional 
> reflection from the
> sidewalls.
>
> Sunbeam have a AUD$150 oven with convection which gives reasonable 
> results,
> alternatively their AUD$60 fanless unit doesn't do too bad either. We 
> used to
> use an ABB multi-step PID controller that had ramp/soak time cycles 
> attached to
> a thermocouple fitted to a strip of PCB left permanently in the oven 
> however
> since then we have moved to a commercial SMD oven.
>
> Cheers
>
> Don

Thanks Don,

what do commercial ovens use? IR Quartz elements?

My though was to remove the standard hearing elements in a standard oven 
and replace it with my own IR Quarts elements evenly space at the top to 
get a more even heat distribution and a faster ramp up. Not certain if a 
fan would be needed in a setup like this.

/Ake

-- 
 ---
Ake Hedman (YAP - Yet Another Programmer)
eurosource, Brattbergavagen 17, 820 50 LOS, Sweden
Phone: (46) 657 413430 Cellular: (46) 73 0533 146
Company home: http://www.eurosource.se      
Kryddor/Te/Kaffe: http://www.brattberg.com
Personal homepage: http://www.eurosource.se/akhe
Automated home: http://www.vscp.org



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