To add an Import node, from the Home or Geometry toolbar, click Import (). In the Import section of the Settings window, set the type of file to import to ECAD file. You can also skip this step as the type of the selected file is automatically recognized by the code. Click Browse to locate the file to import, or enter the path to the file. Before clicking the Import button configure the layer thickness, since the GDS-II files do not include the necessary layer thickness and elevation information to construct a 3D geometry. Click the Refresh Data from File button () to reload the changes that were made in the PCB file, while keeping the chosen import options in the settings window.

For the length unit in the file μm is always displayed, since GDS-II files do not specify a unit. To use the displayed unit as the length unit for the geometry sequence select the Update geometry unit checkbox. The checkbox is selected by default if the Import node is added as the first node in the geometry sequence.

Data contained in GDS-II files is organized in hierarchical structure consisting of cells. Select a cell name from the Cell to import list to limit the import to the selected cell beneath the top cell in the hierarchy. Use the default choice in this list to import the top cell. By default all subcells below the selected cell are imported. To import only one subcell type, select the cell from the Filter by subcell list. The difference between selecting a cell and filtering the top cell by the same cell is that the latter alternative includes all instances of the selected cell, whereas the first case only includes the selected instance of the cell.

The import operation can import each layer into its own geometry object, or import each object from the layers in the file into its own geometry object. To determine which method to use select one of the available alternatives from the Grouping of geometries list:

With the Type of import setting the extrusion of layers can be switched on or off. The Full 3D option imports all layers with a thickness, as specified in the Layers to import table. With the Metal shell option layers are imported as one surface object per layer (with grouping By layer), or one surface object per imported object (with grouping No grouping).

Since layer stackup information is not included in GDS-II files, the layers are assigned a default zero thickness in the Layers to import table. These values can be edited before importing the GDS-II file.

Select the Manual control of elevations checkbox to position the layers in the z direction. When Manual control of elevations is not selected, the z positions of the layers are calculated automatically from the layer Thickness values.

Select the Show names from file checkbox to display the layer names as included in the GDS-II file. This is useful after assigning new layer names that are used in the COMSOL application.

If the datatype record is used in the file for grouping of objects on a layer you can select the Split by datatype checkbox to treat geometry objects of the same datatype as a separate layer. The parent layer is then split into as many separate layers as there are datatypes defined. For example, a layer that contains objects that are grouped into two datatypes will be split into two separate layers after selecting the checkbox. The name of the new layers is obtained by appending the datatype to the name of the parent layer.

The Layers to import table contains the following columns:

To save the layers table to a text file, click the Save to File button () under the table. To load layer table information from a text file, click the Load from File button () under the table. Only the editable data in the table is affected when loading from file. Layer data in the file that does not match the existing layers in the table is ignored. To reset the thickness and elevation values in the table to the last read data from the GDS file click the Reset Thickness and Elevation button (). To select the Import checkbox in the table for all layers click the Select All Metal and Dielectric Layers for Import button (). Click the Clear All Imports button () to clear all checkboxes in the Import column. To reload the layer information from the GDS file to the table click the Reload Layers button (). This is useful in case the GDS file has changed since the last time it was read, and includes additional layers. By clicking Reload Layers you can load the information for the new layers into the table, while keeping any edits you have done in the table for layers that are also found in the new file. Note that layers that are not found in the new file are removed from the table.

By default the Keep interior boundaries checkbox is cleared to instruct the import to remove all interior boundaries on the imported layers. This keeps the geometry complexity to a minimum and can also make the import more robust in some situations.

Recognition of arcs and straight lines can significantly reduce the complexity of imported layouts from GDS files. With the Recognize arcs set to Automatic, all polygon chains that represent arcs are identified and replaced with more efficient curve objects, and polygon segments that lie on a single straight line are recognized and joined into a single straight segment.

With Recognize arcs set to Manual, the following settings will help you fine tune the process of the merging of segments into a single circular arc:

In manual arc recognition mode, the Find straight lines checkbox controls whether to convert several polygon segments that lie on a straight line into a single straight segment. This option uses the number in the Minimum angle between segments field to determine if a group of segments lie on the same straight line.

Short polygon segments that are difficult to eliminate using arc recognition can usually be removed as described in the section Ignore Vertices in Layers.

Geometry repair is controlled via the Repair imported data checkbox and the Repair tolerance list. Change the Repair tolerance from Automatic to Relative to manually specify a tolerance in the Relative repair tolerance field. The geometry repair allows to repair incorrectly drawn objects, such as polygons with (small) gaps.

Select the Ignore vertices with continuous tangent checkbox (cleared by default), to remove, in each layer, vertices that connect two edges that have tangent directions making an angle less than the Continuous tangent tolerance.

Select the Eliminate short edges checkbox (cleared by default), to eliminate, by ignoring one or both of their adjacent vertices, edges that are shorter than the Maximum edge length.

If you want to make the resulting entities contribute to a cumulative selection, select a cumulative selection from the Contribute to list (the default, None, gives no contribution), or click the New button to create a new cumulative selection (see Cumulative Selections in the COMSOL Multiphysics Reference Manual).

Select the Resulting objects selection checkbox to create predefined selections (for all levels — objects, domains, boundaries, edges, and points — that are applicable) in subsequent nodes in the geometry sequence. To also make all or one of the types of resulting entities (domains, boundaries, edges, and points) that the resulting objects consist of available as selections in all applicable selection lists (in physics and materials settings, for example), choose an option from the Show in physics list: All levels, Domain selection, Boundary selection, Edge selection, or Point selection. The default is Domain selection, which is suitable for use with materials and physics defined in domains. For use with a boundary condition, for example, choose Boundary selection. These selections do not appear as separate selection nodes in the model tree. Select Off to not make any selection available outside of the geometry sequence.

Select the Layer selections checkbox to create predefined selections — for domains, boundaries, and objects — in subsequent nodes in the geometry sequence for each imported layer in the GDS file. To also make all of one of the resulting entities that the layers consist of available as selections in all applicable selection lists (in physics and materials settings, for example), choose an option from the Show in physics list: All levels, Domain selection, or Boundary selection. The default is All levels, which makes predefined selections available on all applicable levels, suitable for use with materials and physics defined in domains and boundaries. For use with a boundary condition, for example, choose Boundary selection. These selections do not appear as separate selection nodes in the model tree. Select Off to not make any selection available outside of the geometry sequence.

Select the Cell selections checkbox to create predefined selections — for domains and boundaries — in subsequent nodes in the geometry sequence for each imported cell in the GDS file. To also make all of one of the resulting entities that the cells consist of available as selections in all applicable selection lists (in physics and materials settings, for example), choose an option from the Show in physics list: All levels, Domain selection, or Boundary selection. The default is Domain selection, if available, which is suitable for use with materials and physics defined in domains. For use with a boundary condition, for example, choose Boundary selection. These selections do not appear as separate selection nodes in the model tree. Select Off to not make any selection available outside of the geometry sequence.