Instruction Manual

8-6 Beginning Programming
Pre-Move Delay Factor
Some fluids have a high viscosity which means that they do not dispense as quickly as lower viscosity
fluids. The Pre-Move Delay Factor increases the time that the dispensing head is parked with the valve
ON, prior to a programmed move. The delay at the beginning position insures that a full line is
dispensed. The units are seconds. Typically, 50 ms (0.050 sec) is sufficient for most underfill fluids.
Down Speed
The Down Speed is how fast the dispensing head lowers to dispense. Low viscosity fluids tend to drip
and you may want to set this parameter higher. The units are inches/second. Typically, 2 in/sec is
sufficient.
Down Acceleration
This is the parameter that controls how fast the dispensing head accelerates to the Down Speed. The units
are inches/second
2
. Typically, 300 in/sec
2
is sufficient.
Dispense Gap
The Dispense Gap is the distance between the needle tip and the substrate during dispensing operations.
This distance is one of the more common adjustments made to optimize dispensing programs. The units
are in inches. Typically 15 - 20 mils (0.015 - 0.020 in) is sufficient.
Speed
This refers to how fast the dispensing head moves during dispensing. This parameter is actually not used
for weight control lines, but basic lines where the speed of the dispensing head affects the amount of
fluid dispensed. The units are inches/second.
Shut-Off Distance
This parameter controls where dispensing is discontinued at the end of a move. Low viscosity fluids
require that you stop dispensing prior to the end of the move so that the fluid does not exceed the pattern
limits. The Shut-Off distance is the point where the valve stops dispensing before the end of the move.
The units are in inches. Typically, 30 mils (0.030 in) is sufficient.
Suckback
At the end of dispensing a line or a dot, the valve is reversed for the Suckback period to remove any
material from the tip of the needle. The Suckback value should be set according to fluid viscosity.
Generally, 10 ms (0.010 seconds) is sufficient.
Dwell
This parameter is similar to the Pre-Move Delay Factor, except that it is used at the end of a move. The
Dwell is how long the dispensing head stays at the final position of a move before retracting. This allows
residual fluid to detach from the needle tip before the dispensing head moves to the next location. The
units are seconds. Typically, 0 - 20 ms (0.020 sec) is sufficient.
Backtrack Gap
This is the vertical distance that the dispensing head moves up after completion of a move. At the end of
a move, the dispensing head raises the Backtrack Gap, then moves the Backtrack Length back over the
line that was just dispensed. This encourages congealed fluids to detach and distributes any excess fluid
back across the line. The units are inches. Backtrack Gap should be at least double the Dispense Gap.