Rob,
First thing I would do is ask the supplier of the ink what they recommend
from an atmosphere point of view. They should be able to give you a
solderability vs atmospheric oxygen content, or a resistivity vs atmospheric
oxygen content during cure/sintering.
Since you are most likely speaking of a polymer ink and not a thick film
ink, the reflow oven will more than get you there from a temp standpoint.
Like Dave says, keeping O2 levels down will require attention to detail -
and nitrogen.
I once used a Sikama conduction reflow unit for reflow work on alumina
substrates. With extra internal baffles and nitrogen diffusers, and keeping
the entrance and exit gates as low as possible, I was able to consistently
get less than 10PPM oxygen in the reflow zone, and didn't have to break the
farm with nitrogen consumption.
The oxygen sampling unit is placed outside the oven and [in my case] with a
stainless steel sampling tube [tubes and valving] leading into the various
areas to be monitored. The unit works by pulling atmosphere OUT of the
sample area - usually with a small vacuum pump. I installed a sealed filter
upstream of the monitor so as not to corrupt the cell with flux, or whatever
organics were coming off. So starting at the outside it was Vac pump >
Measurement Unit > filter > high quality valve manifold > furnace interior -
with SS lines and your expensive semiconductor grade gas and vac fittings.
You must have the 1-10 PPM level measurement capability. Yes, it will cost
$
If, by chance you are using a thick film copper ink [not likely on a
laminate, but if you were], you need a controlled atmosphere thick film
furnace. Although low in temp compared to other thick film inks, you will
need the distance/time to get the organics out of the vehicle and allow the
glass to sinter.
Can you just ask the supplier to make up some samples for you? They should
have the ability to screen, and fire/cure in-house. If they don't - well,
just how good is this stuff going to be???
My two pence for the evening
Steve Creswick
Sr Associate - Balanced Enterprise Solutions
http://www.linkedin.com/in/stevencreswick
616 834 1883
From: Robert James <[log in to unmask]>
To: <[log in to unmask]>
Date: 03/01/2013 04:30 PM
Subject: [TN] how is "oxygen-free" defined and measured?
Sent by: TechNet <[log in to unmask]>
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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