>
> Have you done this yet? I've followed the EZ Bake list and it's not so
> simple. To get repeatable results, you need a time and temp controlled
> oven that can heat up and cool down quickly (which means convection)
> and programmed soak and bake cycles. The goal is to keep the board at
> solder melting temp as short as possible to avoid destroying
> components, while still getting 100% good soldered joints.
>
> Steve
>
No i haven't done it on tqfp, only smd transistors and one 8 pin...
I used a professional oven then.
I described it some time ago, it seems very simple to build.
you do not want to have the oven heating up, you put the board in the
heated oven.
It is simple, you make a slot in the side and put two metal rails in.
on this rails you put a carriage. (the surface of the carriage i used was
some
kind of fabric but i guess fine steel mash would work too)
then you put some handle on the carriage...
You need to have two zones, one preheat and one soldering.
The preheat zone is just inside the oven, but is shielded by a piece
of sheetmetal from the heating. the temperature is somewhere aronud 100 to
150 degree
there. (you can find precise temperature curves on the www and even in
datasheets).
there is is a relatiely long time, i think 30 seconds (but the curves show
that too).
then you push it wider in, in the actual heating chamber. there is is only
a short time.
then out again and ready.
The preheat is important for two things:
a) less difference in actual soldering --> shorter
b) the flux is melted and dried. if you put the past
from cold to soldering temp the flux will virtually explode, resulting in
tiny beads
of tin which can cause big trouble.
The oven i used was very expensive i think, but i know for sure it did not
use a second heater
in the preheat. I would maybe build a second heater because it is much
easier to set the
temperature then. the manufacturer spend surely a lot of time adjusting
the preheat zone,
which saved a lot of money in the production. but if you build only one
unit it costs nearly
nothing to make a second heater.
I do not read the ez_bake, do they have such ovens with a sliding carriage?
i would not attempt it different, it was so easy with that professional
oven and i
think it is possible to get the same results with homebrew.
I think to avoid trouble you simply need to heat the pcb quick, which means
you need a oven which is already on temperature.
The reason i have not yet built one is that the solder paste is so
expensive and
i do not have a applicator. (and i do not often use narrow grid smd ics)
ST