SOLDER REFLOW FURNACES
THE SERVOPRO MonoExact DF310E AND AquaXact 1688 WORK TOGETHER TO PROVIDE
A COMPLETE GAS AND MOISTURE ANALYSIS SOLUTION FOR FURNACE ENVIRONMENTS
TRACE MEASUREMENTS FOR
FURNACE ENVIRONMENTS
While the SERVOPRO MonoExact DF310E
digital oxygen analyzer can use both
Coulometric and Paramagnetic sensing
technology to measure O 2 , the relevant
technology for this process is Coulometric.
Coulometric process which sees O 2 in the
sample gas reduced at the cathode to
hydroxyl ions. Assisted by a potassium
hydroxide electrolyte, the ions migrate to
the anode, where they are oxidized back
to O 2 and vented out of the sensor.
Conventional electrochemical sensors
use a consumable lead anode and silver
cathode. The carbon/nickel composition
Using carbon and nickel electrodes which
remain unaffected by chemical change, the
non-depleting Coulometric sensor avoids
the problems associated with galvanic or
zirconium oxide sensors in a furnace.
of the Coulometric electrodes means they
are non-depleting. Neither electrode
undergoes chemical change, so excellent
measurement stability is achieved.
Coulometric sensing also provides a fast
response, giving an immediate indication
of any changes in O 2 , regardless of whether
that change is caused by an ambient air
leak or by incorrect N 2 inerting levels.
ACID GAS TOLERANCE
RAPID
RESPONSE
Unlike those sensor technologies, the
Coulometric sensor does not need
periodic replacement, nor does it produce
false low readings due to a loss of
measurement sensitivity or a reaction
with sample gas components.
It also offers an advantage over galvanic
sensors by not needing frequent calibrations.
The way the sensor works is by a simple
ALUMINUM OXIDE
The ability of the SERVOPRO MonoExact
DF310E and AquaXact 1688 to integrate
seamlessly for the combined analysis of
O 2 and moisture offers an ideal solution
for many applications, including metals
annealing, air separation, instrument air
production and glove box purging.
One specific application is solder furnace
monitoring, which requires careful,
responsive, and accurate control of oxygen
and moisture in the furnace environment.
In the past, printed circuit boards (PCBs)
were cleaned with chlorofluorocarbon
(CFC) based agents before soldering.
However, the use of CFCs has now
been largely eliminated because of
environmental concerns.
This means PCB manufacturers must
create an inert environment in the solder
furnace. To ensure consistent soldering
quality, it is necessary to monitor the
level of O 2 in the furnace.
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If high-quality solder joints are to be
assured, the nitrogen in the solder furnace
also needs to have a low moisture dew
point, typically below -50 o C.
Servomex’s MonoExact DF310E digital
oxygen analyzer uses Coulometric sensing
technology to measure ppm O 2 . This
Coulometric sensor needs only an annual
span adjustment, bi-annual addition of
replenishment solution, and no proactive
maintenance cell replacements, all of
which lowers the lifetime cost of ownership.
It also offers a five-year performance
guarantee not matched by any other
oxygen analyzer company.
Adding the AquaXact 1688 to the
MonoExact DF310E’s digital electronics
provides an ideal solution for the
exceptionally accurate monitoring of
both O 2 and moisture in one system.
Unlike conventional moisture sensors, the
AquaXact 1688 does not suffer from drift,
so the response curve remains the same
even after many months of operation at
an elevated temperature.
In solder furnaces, this combination of
technologies means excellent batch-to-
batch solder quality and significantly
reduced nitrogen consumption, with
no compatibility issues caused by using
sensors from different sources.
Aluminum Oxide sensors work by
measuring the capacitance between the
aluminum core and a gold film deposited
on top of the oxide layer. This varies with
the water vapor content contained in the
pores of the oxide layer.
Three fundamental structural
improvements in the oxide layer mean
that the AquaXact 1688 has industry-
leading sensitivity and stability.
Firstly, the Servomex sensors have a much
thinner oxide layer than comparable
devices, without compromising
transmitter strength. Since capacitance
is inversely proportional to the distance
between the capacitor’s plates, the
GAS SAMPLE
CARBON CATHODE
40H -
NON DEPLETING
PROPRIETARY ANODE
O 2
Coulometric
sensing
O 2 + 2H 2 O + 4e -
4OH - (cathode)
4OH -
O 2 + 2H 2 O + 4e - (anode)
thinner layer produces much higher
capacitance changes, reducing the impact
of drift due to undesirable factors. capacitance for a given change in dew
point is increased, providing more accurate
results, and a quicker response.
It also means water moves in and out of
the pores more quickly, producing a
faster response than conventional
Aluminum Oxide sensors. The pore geometry in conventional
sensors collapses slowly over time,
requiring frequent recalibration. The
AquaXact 1688’s pore geometry does not
change significantly, so it needs only an
annual calibration check when used in
clean, non-corrosive gases.
A better-defined barrier layer between
the aluminum and the aluminum oxide
reduces metal migration, which is one of
the major causes of aging drift in
conventional sensors. The response
curve for the AquaXact 1688 is unchanged
by several months of operation at a
high temperature.
The most significant improvement is the
unique, stable pore geometry of the
AquaXact 1688, which enhances the
entrapment of water molecules. By
holding more water, the change in
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Get the combined solution for your process today:
MonoExact DF310E: servomex.com/monoexactdf310e
AquaXact 1688: servomex.com/aquaxact1688
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