User guide

Beginning Programming 8-7
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.
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.
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.
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.
Retract Distance
This is a vertical distance that the dispensing head moves after the Backtrack Gap and
Backtrack Length dispensing commands have completed. Figure 8-2 shows the relationship
between Retract Distance, Backtrack Gap and Backtrack Length. The Retract Distance
must be within the Safe-Z Height defined in Initial Setup. The units are inches. Typically, 250
mils (0.250 inches) 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.