Homebrew PCBs

On Jan 31, 2008 9:15 PM, eeks123 <eeks123@...> wrote:
> > I've found the opposite to be true.  I've done 5.5 x 3.5 boards on
> > that hotplate, moving it around the whole time, and nothing moved out
> > of place.

> it's logical if components are sticked to the board with solderpaste!
> i have no experience with this and thought they would move around..


Basically that is the idea, yes. But if you reflow with hot air
instead of an oven this doesn't always work perfectly. Some part
shapes tend to be pushed around by the air, like MELF diodes.
It also depends on the solderpaste used, some stays in shape when hot
and some melts and forms large puddles on which the components swim
around. Sadly the one i found which doesn't spoil too fast forms the
large puddles, but i figure better that than throwing out hard paste
all the time.
With an oven or hotplate it is better, because there is no air stream.
But you still need to observe some layout considerations for parts to
stay put. Always think surface tension. In the worst case you will
only have to rework a few parts, so that's not really a problem.


ST