ESTechnical Reflow Oven Controller Full Upgrade Kit for T962A
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The oven's cooling fan is used to provide a small amount of air movement inside the oven, this helps
the oven evenly heat the PCBs. The speed of the fan is important, too fast and the oven is being
actively cooled while trying to heat up, too slow and the PCB will be heated unevenly.
The fan is run at a fixed 'idle speed' during reflow to provide a small amount of air movement in the
oven. The fan should idle very slowly, to adjust the idle speed:
Navigate to
Fan settings
in the menu.
Press
OK
,
Idle Speed
will display on the screen.
Press
OK
to edit. (The default value for the fan idle speed in T962A / T962A+ is 35, for the T962
the default is 15.)
Test this idle speed by starting a reflow cycle, the fan should start up easily but not run so fast
as to cause the oven to be cooled dramatically during reflow.
It is very important this value is set high enough for the fan to start every time the cycle is
started (at low values, the fan will not be able to start spinning) but it is equally important not
to set this speed too high, otherwise the fan forces too much cool air into the oven and reduces
the efficiency of reflow soldering.
If the PCB temperature profile does not follow the programmed profile settings closely:
Set the
Fan idle speed
to a low value and ensure that the fan starts when a reflow cycle is
started.
Perform a test profile using a PCB with thermocouple and observe the resulting temperature
profile of the PCB.
Increase the
Fan idle speed
by 5-10 and repeat the test cycle without changing any profile
settings.
When the PCB temperature accurately tracks the programmed profile temperature, note the
Fan idle speed
value and ensure it is saved.
Profile tuning tips
To get the best from your reflow oven, it is advisable to perform a series of tests to determine the
settings required to properly reflow each design of board you work with. Boards of different masses
will behave differently and may require different soak duration, temperatures etc. to properly reflow
all solder joints on the board.
Refer to the data sheets for all the parts you use to determine the allowable reflow profile for the
design. Once the peak temperature of the most sensitive part is known, this must not be exceeded
anywhere on the board.
The board's temperature lags behind the heat of the heater tubes, the oven controller is not
controlling the board temperature directly, but the air temperature inside the oven via the
thermocouple mounted above the PCB. However, the surface of the PCB will absorb more energy than
the thermocouple directly due to the IR radiation, meaning that it is possible for the PCB temperature
to overshoot the air temperature in the oven.
The PCB temperature should always remain below or equal to the profile temperature set using the
controller; until cooling begins. If the soak duration is too long or the ramp rate too slow, the board
temperature will exceed the soak temperature before the soak stage of the profile is completed. This
will cause the temperature of the board to remain above the profile temperature that has been set,
resulting in the peak temperature being higher than required.
