Import Via Array Options

The Import Via Array Options page of the Import Wizard is opened when you click on the Specify advanced via array options checkbox in the Import Via Options page of the Import Wizard.

Since Sonnet can handle a wide range of layouts and processes, several controls were included to adjust the behavior of the simplification algorithm. The controls influence which vias should be considered an array and the resulting simplified via polygon shape. Based on extensive testing, default values were determined for these controls, however the user may override them when appropriate. The controls are detailed below.

Minimum vias in array: This control defines the minimum number of vias which can be considered part of the same array. The default value for this setting is five, so that only arrays with 5 or more vias will be considered for simplification.

Maximum distance to size ratio: This control defines the maximum spacing between vias which can be considered part of the same array. While the distance between vias is measured from the center lines of the individual vias, the control is a ratio of distance to via size. This distance cannot exceed the value of this ratio multiplied by the via size. The default setting is 6.0 and the larger the value, the more widespread the vias can be and still be grouped in the same array. Since individual via cross-sections can be of any shape, the square root of the via area is used as the via size.

Maximum size to size Ratio: This control defines the maximum allowable difference in via size to be considered part of the same array. The default value of this ratio is 1.5 and the larger the value, the greater the difference of via size is allowed within an array. Since individual via cross-sections can be of any shape, the square root of the via area is used as the via size. If you wish to limit your arrays to vias of the same exact size, set this control to 1.0.

Number of new via metals created: These three radio buttons control how many via metal types are created in your translated project in order to model your simplified array. Minimum will create the least number of via metal types but may be less accurate as a wider range of fill factors will be grouped together. Maximum will create the highest number of via metal types providing the most accurate answer since a via metal type is created for each unique fill factor. Automatic creates the via metal types based on an algorithm that balances the trade off between accuracy and the number of via metal types produced. This is the default setting.

Maximum Expansion Coefficient: This control helps define the size of the resulting simplified via by allowing it to be larger than the original via array perimeter (also referred to as the bounding box). The default value is 7.0, which allows the simplified via to expand outward by a factor of 7 times the largest via size in the array. The advantage in expanding the simplified via is that it can often be sized to match the polygons which the via attaches to. Having the via polygon edge and pad polygon edge in alignment can significantly reduce the subsection density in the region and thereby reduce the memory requirement of the model.

The algorithm looks outward from an imaginary rectangle (bounding box) drawn around the perimeter of the array. The distance checked out from the perimeter is the Max Expansion Distance. It is equal to the Max Expansion Coefficient times the largest sized existing via in the array. If a vertex from a pad polygon is encountered within this window, the expansion stops and this sets the simplified polygon edge. If no vertices are found in a particular direction, the edge of the simplified via rolls back to the existing via array perimeter. Please note that all metal levels are examined when looking for vertices within the maximum expansion distance.

 The default value is 7.0, which will often result in simplified vias significantly larger than the original array size. If you wish to limit the simplified via size to the original via array size, set this control to 0.

Merge planar polygons during simplify: In order to be considered an array, a group of vias must connect to a single polygon on the top and bottom of the group. This control allows the software to merge the polygon pads or traces prior to simplifying the vias. This results in larger arrays being recognized leading to the least number of simplified vias, thereby producing the most efficient model. This option is enabled by default.

Please note that the polygons are only temporarily merged for via simplification and will not be merged in the resulting Sonnet project unless the Merge planar polygons option was selected in the Import Advanced Options page.

Restore Defaults: Click on this button to restore all the settings in this page to their original state when the software was initially installed.

For a detailed discussion of Via Array Simplification, please see Via Simplification.

Next: Click on the Next button to continue the import process. The Import Results page is opened and the import is executed.