To answer your question literally as asked.
I used to profile the ppm in reflow machines by putting a copper pipe on the
O2 meter which was on a trolley. The pipe was long enough to pass through
the reflow machine. You then position the trolley so the other end of the
pipe is sampling the entry to the machine and then push it in a bit and take
a reading and so on. This is a time consuming process as it takes a while
for the readings to stabilize each time. It can give accurate readings and
these might be different than the readings from the ovens own system which
may not have the sampling point at conveyor level.
Remember the Sod's Law of the Laboratory when doing this: Hot glass looks
the same as cold glass. (modified in this case to copper)
Commercially available Copper based thick film inks usually state O2 max
10ppm.
Resistivity goes up with O2 ppm as the copper oxidises. So how many ppm you
need to control to depends on the conductivity you require. 
A typical firing profile for these inks would peak around 900C and last
about 60 minutes. 
.
I would say this all is bit beyond your average reflow system so I imagine
that what you asked is not literally what you meant. 
I imagine you have some copper filled polymer ink and that will just need a
profile to cure the polymer which possibly could be within a larger reflow
oven's capability (or a box oven), probably the ppm requirement will be
similar. If you have some magic nano-particle based material, that might
give you a claimed much reduced temperature and other interesting
properties, good luck with that. 


Regards 
 
Mike Fenner 
Bonding Services & Products
M: +44 [0] 7810 526 317 
T: +44 [0] 1865 522 663



Hi Everyone,
I am trying to sinter some copper ink using a solder reflow oven.  To
prevent oxidation of the copper as the temperature is elevated, I'd like to
purge the system with nitrogen to displace the oxygen before the temp is
ramped (the oven allows me to do this).  I'm unsure, however, what the exact
requirement is - for 'oxygen-free' processes, what level of O2 is typically
allowed? How is it measured?  From what I've seen, there are basically two
types of O2 sensors - relatively inexpensive ones designed for determining
whether an atmosphere is breathable, or those with ppm accuracy.  The former
may not be sensitive enough, the latter are horribly expensive and not
particularly well suited to being placed inside a reflow oven.  What is
commonly used in the industry?  Any advice or recommendations would be
greatly appreciated.

regards,
Rob



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