Re: gEDA-user: Cheap 4 layer manufacturer?

[Randall Nortman <geda-lists@xxxxxxxxxxxxxxx>]

On Tue, Oct 11, 2005 at 10:12:02AM -0400, DJ Delorie wrote:
> 
> > The oven a 1500-watt Oster, and was $60 at Target.  It's got four
> > heating elements (two top, two bottom) and, as I mentioned, a
> 
> /me wonders if it's better to only heat the board from the bottom
> (i.e. move all the heating elements to the bottom).  For BGAs that
> would mean that the heat didn't have to go through the heat-sensitive
> BGA to get to the solder balls.

Not a good idea if you want to be able to do boards with components on
both sides.  When doing the second side, there will be components on
the bottom, and I think you would get them too hot by the time the top
got hot enough to melt the solder there.

I wonder -- do the real reflow ovens use bottom heat on the first side
and then switch to top heat when doing the second side?

Randall