Hmm, you folks across the puddle have ezy auditors,
here we have to calibrate a program for EACH board,
as they have different rates of soak,
funny (slow) gradients on caps,
mighty shades on canned caps legs ,
etc.etc.etc.
Permanent oven sensors serve only purpose of assurance
that thing works, ages, fills up, etc.
monitor and maintenance aid = little to do with card itself.
"Calibrated" oven won't save you from a total flop Mike :
if you'd be a sub house getting out of the mill card to bake .
A lot of the componentry makes mockery of your calibration,
very fast very expensively,
wizards like Steve are absolutely essential in subs.
Basically you need the imagination of what COULD be outside of window,
with the card of the moment;
often you have one pass to play with .
There are no rules in the real world,
no matter how well we'll try to canonize it all; just think :
it's not the oven you need under process control.
Some can solder better with blowtorch than some with oven.
Hope Jim M reads this.
reminds me, for "repair/rework/mod/specials/etc. masters:
http://www.riogrande.com sells great needle fed flame throwers,
delightfully mini, designated mainly to gold work,
easily understood to solder of heavy heatsinkers (tranies, sinks,
coils,...),
just don't melt the copper
paul
-----Original Message-----
From: Stephen R. Gregory [mailto:[log in to unmask]]
Sent: Tuesday, 1 August 2000 11:04
To: [log in to unmask]
Subject: Re: [TN] Reflow Oven
In a message dated 7/31/00 7:43:51 PM EST, [log in to unmask]
writes:
<< We require our Reflow ovens to be calibrated and more importantly, to be
under process control.
Currently we use a thermal profiler to check the oven and use the profiler
to determine the profile for each type of board put through.
What is the best way to ensure that the oven will produce good results with
the minimum of fuss.
I understand that a our profiler which thermocouples are soldered to the
board, does give an indication what the PCB is subjected to.
The other method is to have thermocouples connected to the oven but it does
not give a true indication what is happening to the PCB,
Can anybody help.
Regards,
Mick >>
Hi Mick!
Ahhh, the ol' oven calibration thing! I've run into that before. I have a
ECD
M.O.L.E. (and that is calibrated regularly, rather than the daunting task of
calibrating each thermocouple in the oven). What I've done that satisfies
most people is to create a "calibration profile"...150-degrees C. across all
zones at a fixed belt speed (you can use whatever you want, I use 30-inches
per minute).
Then run my MOLE through the oven with the thermocouples hanging in the air
in a fixed position that is spread across the width of the conveyer to
create
a baseline plot.
I then run that same profile monthly and print out the graphic. You can
compare each plot from month to month and keep it on file to show that the
oven is staying consistent. Of course most ovens will tell you when
something
is outta' whack, but this usually satisfies most auditors....
-Steve Gregory-
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