Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "Phil" <phil1960us@y...> wrote:
> I'm in the process of looking for a toaster oven to turn into a 
> reflow oven.  I've been looking in second-hand stores and most of 
> these are pretty junky.  I saw a convection toaster oven for like
$70 
> new at (I think) target.  Given that these essentially blow hot
air, 
> I thought it might be ideal for conversion and that it might be a 
> solution to the heat loss problem.  I think I'd need to install
some 
> sort of flow defuser to prevent moving of smaller, lighter parts.  
> Has anyone tried one?  
> 
> I might want to build a controller for it that would cycle the heat 
> (pre-heat, heat, cool down) in a controllen fashion.
> 
> --- In Homebrew_PCBs@yahoogroups.com, Markus Zingg <m.zingg@n...> 
> wrote:
> > 
> > I do have one of them here to play with, but I heard that the heat
> > disapears way too fast if you have to open the door to feed it. 
> Since
> > I intend to solder BGA's with it I figure I will have to modify it
> > quite a bit. Did not yet found the time to start this project,
but 
> the
> > day will come - I'm sure.
> > 
> > Markus


--- In Homebrew_PCBs@yahoogroups.com, Markus Zingg <m.zingg@n...>
wrote:
> >One of these days I will do multilayer. Biggest problem is having a
> >place to setup a PTH station. It will be a while before I have a
place
> >where I can do something like that. 
> >I do not use a "real" reflow oven, but my cheap little toaster oven
> >does a pretty good job of pretending to be one.:)
> 
> I do have one of them here to play with, but I heard that the heat
> disapears way too fast if you have to open the door to feed it.
Since
> I intend to solder BGA's with it I figure I will have to modify it
> quite a bit. Did not yet found the time to start this project, but
the
> day will come - I'm sure.
> 
> Markus

The process with my oven is to start cold. I put the board in, close
the door and turn the heat up to about 250F. I wait about two minutes
to provide a little of preheat time. I then turn the oven up to max
and in about 2 to 2 1/2 minutes the solder is melted. I then turn off
the oven, open the door and wait about 5 minutes for cooldown. 

I have not lost a board or a component yet, but there a few things to
keep in mind. Any tall components, like connectors, will cast a shadow
and slow down the reflow of the shaded components. So I leave things
like large connectors off. My oven has one heating element on top and
one on the bottom. So there is definitely uneven heating. The largest
board I have done so far is 2.5 by 3 inches. Based on how the relfow
went on that one, I think that is about the limit for this oven.  

My next board will probably be in the 3x5in size and for that one I
will invest in a convection oven to get more even heating.

I have attempted one BGA component which was an 8 pin 555 timer. The
problem I had was not with the oven, but the lack of a solder mask. So
the solder wicked along the traces and the component did not set
right. When I figure out what solder masking method I want to use, I
will give the BGA's a try again.