Manual

7-36 Advanced Programming
Variable Valve Speed
Variable Valve Speed (VVS) is a new technology available with FmNT 4.5 and above that allows the
programming of multiple material flow rates per board without necessitating dual valves. Variable Valve
Speed has proven to significantly reduce cycle time by optimizing each dispense pass for an optimum line
speed without compromising quality or repeatability.
Many underfill and packaging applications require dispensing lines of various lengths and weights
resulting in multiple line densities. One such application is underfilling various size die on a single board
or module as shown in Figure 7-16 below.
Figure 7-16 Multi-Chip Module
Other applications include cavity fill patterns or even single chip modules with fillet passes.
Variable Valve Speed allows you to program with multiple flowrates, utilizing an optimum line speed for
each line, and substantially increase throughput. The ability to adjust the valve speed through the
software allows the programmer to achieve a target weight while maintaining the fastest possible dispense
speed for each unique line.
How it Works
A programmer creates a table of desired valve speeds and calibrates the flow rate for each of these speeds.
" NOTE The DP-3000 Positive Displacement Pump is independent of viscosity changes,
and therefore a daily calibration of the table would be unnecessary.
Once a calibration table is complete, the weight control lines/pots may be programmed. The software
allows you to input a “true” target weight for a weight control line. The associated line speeds are then
calculated and listed in a summary table. The programmer then selects a line speed that will deliver both
acceptable quality and optimal throughput.
In the example shown in Figure 7-17, the geometry and fill requirements of the seal pass would typically
limit the process to a flowrate of 30 mg/sec. A traditional dispense would result in a dispense time of 2.7
seconds (1.7 seconds for the fill and 1 second for the seal).