RE: gEDA-user: Cheap 4 layer manufacturer?

["Mark Cianfaglione" <mark_cianfaglione@xxxxxxxxxxx>]

Real reflow lines do the first side with slightly higher melting
temperarture solder then flip the board and use a slightly lower temp solder
for the second side. The reflow ovens control the temperature VERY well
(+/-.5C) and the bottom side (the side not getting the components ) is
usually about 5C lower than what the top side is seeing. (top and bottom
being the side getting the parts at this moment and the other side
respectfully)

Mark

 

-----Original Message-----
From: owner-geda-user@xxxxxxxx [mailto:owner-geda-user@xxxxxxxx] On Behalf
Of Randall Nortman
Sent: October 11, 2005 9:39 AM
To: geda-user@xxxxxxxx
Subject: Re: gEDA-user: Cheap 4 layer manufacturer?

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