Hi - is the thermometer the oven thermometer?  If so beware that it can=20
be way off; the toaster oven I use for reflow is supposedly a pretty=20
quality toaster oven for food, but its thermometer was wayyy off.  You=20
could have been really cooking the pcb, my first attempts were clearly=20
way too hot.

If you are in the USA consider getting a cheap thermocouple:
jameco.com 220741 (Mastech MAS838), $20 including the thermocouple.=20
Works great.

I'd recommend getting real solder paste and not going over about 210deg=20
C.  That should be fine for leaded solder.  With a syringe you can lay=20
down thin lines or dab little bits on each pad.

J



lee@baudalign.com wrote:
> Hi all, can't find any real info on this online so thought I'd ask you gu=
ys.
> The other day I tried my first "toaster oven" reflow, but instead of usin=
g
> solder paste I had first hit the pads with a soldering iron and standard
> 63/37 solder wire, then plonked the components on top, as per a previous
> "HASL reflow" thread.
> I just set the oven to 250C and was closely watching both the solder
> joints for signs of reflow and the oven thermometer I had in there.  I'm
> thinking the thermometer was slow to react, or not reading the same heat
> as the board was seeing, as around 220C (according to thermometer) the
> board started warping, then rapidly released the foul-smelling evil black
> goo.
>
> So a few Q's:
> - are the goo fumes poisonous?  The only reference I can find anywhere is
> from SparkFun, who say it's the glue used to laminate the FR4 / copper,
> and that it's really hard to get rid of the smell.  No mention of how
> dangerous it is though.  i got out of there quick-smart and closed the
> door, but took a few minutes to gather my wits and open garage doors and
> get the board outside.  I hadn't been expecting anything like that, so
> only had the nearby window wide open for ventilation.
>
> - any tips on where I stuffed up?  I'm still not sure if the solder had
> reflowed or not, it's hard to tell when the solder was shiny to begin wit=
h
> rather than the grey paste state, and though the components seem stuck
> down they don't particularly _look_ reflowed.
>
> - reckon I should just lay down a line of paste using a syringe next time=
?
>   Part of the board design needs a redesign, so it's not worth making a
> stencil;  I just want to test a few of the circuit sections that "should"
> be properly designed.
>
> - I think next time I'll do a pre-heat and a pre-soak, my initial
> temperature mapping seemed to indicate the heat-up of the oven from cold
> was reasonably close to a good reflow profile, but obviously it ain't?
> Oh, and I'll do it outside.
>
> The victim:
> http://img542.imageshack.us/img542/9649/f53k.jpg
>
> Lee
>
--=20
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