Homebrew PCBs

>    Posted by: "Stefan Trethan" stefan_trethan@... stefan_trethan
 >   Date: Wed Aug 16, 2006 10:49 am (PDT)


>But now comes the nasty part - writing some atmel C software that 
>allows....

Stefan,

    Have you looked at the recent Elektor SMD oven article?  It has 
some clever temperature calibration routines. (and uses an Atmel 
processor which Elektor has for sale programmed)

    I bought an 800W oven for ?19 which gets to soldering temp in 5 to 
6 mins without extra insulation.  I also contemplated grafting a 
second pair of elephants  to increase the temp profile but don't think 
it will be necessary.  I'll definitely add insulation however.

    The control side of the oven is also rather small to fit a single 
PCB (the Elektor PCB is huge ;-) so I used Eagle to generate a new PCB 
in three parts ( input, power and CPU) which will allow it all to fit. 
I've sourced all the components but haven't built the controller yet. 
If you're interested, I can send you the files.  You can download the 
code from the Elektor website free.

    Philip.

On Thu, 17 Aug 2006 09:55:52 +0200, Philip Mac Cabe <Philip@...>  
wrote:

>
>     I bought an 800W oven for ?19 which gets to soldering temp in 5 to
> 6 mins without extra insulation.  I also contemplated grafting a
> second pair of elephants  to increase the temp profile but don't think
> it will be necessary.  I'll definitely add insulation however.


Isn't 6 minutes a bit long for SMD soldering? It would depend on where  
most of this time is spent, but with a lack of power it is usually the  
highest temperatures where the increase is slowest.


How do you plan to insulate it? Glass wool or rock wool or something?  
Seems like there is aluminum foil or something stuck to the insulation  
used in full-sized baking ovens. I would have a old broken one to take it,  
but i'm kinda afraid it might contain asbestos?

I may want to isolate at least the electronics compartment a little from  
the baking chamber.


ST

--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan" 
<stefan_trethan@...> wrote:
>
> Seems like there is aluminum foil or something stuck to the 
insulation  
> used in full-sized baking ovens. I would have a old broken one to 
take it,  
> but i'm kinda afraid it might contain asbestos?
> ST
>

Only a real old oven can contain asbestos. Something like 20 years.
Even in my country, before the Berline Wall fell in 1989, this 
material production was stopped. Of course, after no one knows how 
many workers died from lang cancer.


Adrian

--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan" 
<stefan_trethan@...> wrote:

> Seems like there is aluminum foil or something stuck to the 
insulation  
> used in full-sized baking ovens. I would have a old broken one to 
take it,  
> but i'm kinda afraid it might contain asbestos?
> ST
>

Only a real old oven can contain asbestos. Someting like 20 years, I 
supose.
Even in my country, before Berline Wall fell in 1989, this material 
production was stopped. Of course, after no one know how many workers 
died from lang cancer.

Adrian

On Thu, 17 Aug 2006 22:30:50 +0200, adicont2 <adicont2@...> wrote:

>
> Only a real old oven can contain asbestos. Something like 20 years.
> Even in my country, before the Berline Wall fell in 1989, this
> material production was stopped. Of course, after no one knows how
> many workers died from lang cancer.
> Adrian


Well, this oven i was thinking about has been sitting there for at least  
20 years, and i would assume it was in use a few years before getting in  
such a beaten-up shape...

I would assume glass wool or rock wool must be heat resistant, no?

ST

--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan" 
<stefan_trethan@...> wrote:
>
> Well, this oven i was thinking about has been sitting there for at 
least  
> 20 years, and i would assume it was in use a few years before 
getting in  
> such a beaten-up shape...
> I would assume glass wool or rock wool must be heat resistant, no?
> ST
>

Yes, glass wool is that you need. You can make a sandwich with glass 
wool and aluminium foil. The foil must be inside the heated room, 
between the heaters and glass wool to reflect the heat inside. This 
way you can increase heaters eficiency to a quite hi level.


Adrian

On Thu, 17 Aug 2006 23:31:36 +0200, Adrian <adicont2@...> wrote:

>
> Yes, glass wool is that you need. You can make a sandwich with glass
> wool and aluminium foil. The foil must be inside the heated room,
> between the heaters and glass wool to reflect the heat inside. This
> way you can increase heaters eficiency to a quite hi level.
> Adrian


But i thought the isolation goes around on the outside of the baking  
cavity? Like in the oven in the kitchen - it has the outside wrapped with  
some material that is covered by foil.

ST

And poking a little light hearted fun and Philips spell checker typo.

You've got to be carefull with a "pair of elephant" when they are over 
20 years old also. They can be very grumpy and no do as they are told!!!!

Clearly Philip intended to type a "pair of elements", but it did make me 
laugh!

Cheers,
David



Adrian wrote:

> --- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan" 
> <stefan_trethan@...> wrote:
>
>   
>> Seems like there is aluminum foil or something stuck to the 
>>     
> insulation  
>   
>> used in full-sized baking ovens. I would have a old broken one to 
>>     
> take it,  
>   
>> but i'm kinda afraid it might contain asbestos?
>> ST
>>
>>     
>
> Only a real old oven can contain asbestos. Someting like 20 years, I 
> supose.
> Even in my country, before Berline Wall fell in 1989, this material 
> production was stopped. Of course, after no one know how many workers 
> died from lang cancer.
>
> Adrian
>
>
>
>
>
>
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> Date: Thu, 17 Aug 2006 20:57:42 -0000
> Subject: [Homebrew_PCBs] Re: SMD Oven thoughts
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>
> --- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan" 
> <stefan_trethan@...> wrote:
>
>   
>> Seems like there is aluminum foil or something stuck to the 
>>     
> insulation  
>   
>> used in full-sized baking ovens. I would have a old broken one to 
>>     
> take it,  
>   
>> but i'm kinda afraid it might contain asbestos?
>> ST
>>
>>     
>
> Only a real old oven can contain asbestos. Someting like 20 years, I 
> supose.
> Even in my country, before Berline Wall fell in 1989, this material 
> production was stopped. Of course, after no one know how many workers 
> died from lang cancer.
>
> Adrian
>
>
>
>
>
>
> Be sure to visit the group home and check for new Links, Files, and Photos:
> http://groups.yahoo.com/group/Homebrew_PCBs
>
> If Files or Photos are running short of space, post them here:
> http://groups.yahoo.com/group/Homebrew_PCBs_Archives/ 
> Yahoo! Groups Links
>
>
>
>  
>
>
>
>  
>   
>   
>  -0-0-0- 
>

> David C wrote:
> And poking a little light hearted fun and
> Philips spell checker typo.  You've got to
> be carefull with a "pair of elephant" when
> they are over 20 years old also. They can
> be very grumpy and no do as they are
> told!!!!
> 
> Clearly Philip intended to type a "pair of
> elements", but it did make me laugh!

I went the other way and assumed he was going
to feed the elephants a lot of grass so they
could produce methane.  Then he could have
a "natural gas" powered reflow oven.

On Fri, 18 Aug 2006 00:31:15 +0200, David Cureton <yahoo@...>  
wrote:

> And poking a little light hearted fun and Philips spell checker typo.
> You've got to be carefull with a "pair of elephant" when they are over
> 20 years old also. They can be very grumpy and no do as they are told!!!!
> Clearly Philip intended to type a "pair of elements", but it did make me
> laugh!
> Cheers,
> David


Lol, i wondered about that too ;-)

BTW elephants can be pretty scary when they have this crazy time, will  
take apart people with no trouble at all.
Recently shown on NGC i think... So a grumpy elephant may not be very  
funny if you meet it...


ST

Stefan,

>Isn't 6 minutes a bit long...

    One common reflow profile calls for an initial gradual heat 
(approx 2C/sec) up to 125C, then a slow increase (about 1C/sec) up to 
175C, followed by rapid heating to soldering temp (220-250C) and a 
10-15 sec dwell for full reflow.  Altogether about 2.5 mins and then 
cooling down.  Co-incidentally, this sounds like it would be a good 
profile for baking the ink also ;-?

    I reckon with some insulation (there is none currently) it should 
be achievable OK.  Elektor recommend 100W+ per litre of oven.  Mine is 
800W and 4 litres so should comfortably exceed these requirements. 
Stripping out most of the internal metalwork will also help.

>How do you plan to insulate it?

    Some time ago while building a heat-treatment muffle, I bought a 
large roll of refractory insulation, rather like rock-wool but good 
for 1800C.  I still have lots left, so I'll be using some for this 
project.

>I may want to isolate at least the electronics...

    Definitely!

Regards,

Philip.