Terms and Definitions
Before proceeding we should define terms and also state some underlying assumptions.
Droplet Diameter - The diameter of the ink droplet after it has hit the substrate and spread out. This value is used for two purposes: 1) to produce a simulation of droplet converage; 2) to offset the position of the droplet center so that the droplet falls completely inside of the line or pad to be imaged.
Nominal Pitch - The number of grid pixels used to space apart droplets. We call this nominal since the value only applies in the vertical and horizontal directions -- any other direction and there will be some difference. The minimum value = 3.
The grid is specified in dots per unit. For example if you are working in units of inches the grid is specified in DPI.Consider a system that operates at 5080 DPI which is equivalent to a 5 um grid. This means that one can "place" a droplet on a 5 um grid and only on those 5 um grid points. If one specifies a value of 3, then the droplets will be spaced approximately 15 um apart.
Additional Offset - the distance from the edge of a figure to the center of the droplet. By default we will offset the droplet position by 1/2 of its diameter so that no part of it “leaks” out. However there are forced tradeoffs between where one would like to place the droplet and where one can place the droplet.
In the image below we illustrate some of these values:
The magenta boundary represents the original CAD data of a line and a round pad
The green path represents the offset of 1/2 of the diameter of the droplet.
The distance between circles (center to center) represents the pitch.