Support for Apertures in the Altium Designer CAM Editor

PCB layers are created from photographic film that has been exposed to light. Apertures are the physical openings through which the light shines on the film. CAM data includes aperture definitions (size and shape), plus instructions about where to flash the light through apertures, and where to draw lines on the film by moving between locations with the light beam still on. Different pad sizes will be created by flashing different apertures on the film; thicker or thinner tracks will be drawn on the film by dragging the light beam across the film through larger or smaller apertures.

As technology evolves, physical apertures may drop out of the PCB manufacturing process altogether. Even now, many modern laser plotters transcend the need for physical lens apertures, simulating the corresponding shapes on the film with raster operations.

So far, these advances have not changed the way we talk about CAM images. Every CAM file requires an aperture list, regardless of whether these images will ever really be transferred to the film through physical apertures. Every new CAM document you create will contain a blank Aperture Table. This table is filled automatically when you import CAM data with embedded apertures, such as RS-274-X Gerber formats, or ODB++ data. If you're importing a format that does not embed apertures, such as Gerber's RS-274-D, you will need to include an aperture list as well.

Aperture Lists

Gerber formats are standardized, but aperture lists are not. Every CAM exporter has its own format for aperture keywords and specifiers, and this can make it difficult to import aperture lists. The CAM Editor eases this burden by providing dozens of aperture list wizards for the prevailing formats – as well as many legacy ones – that you may encounter. If any of these wizards need to be altered to fit the data you typically receive, or if you want to create a new wizard from scratch, you may do so by editing individual line formats.

When importing aperture lists, you can set the detection to automatic, which will search through all of the defined aperture wizards for one that will import your file without errors. The CAM Editor gives you complete access to all of these wizards, should you need to make any changes.

Aperture list wizards all have general settings and line format instructions. General settings include such information as where to start and stop reading aperture lines, what units and scale to use, and whether more than one aperture definition may exist on a single line.

Individual line formats are defined by tags and keywords for each shape. The CAM Editor contains an arsenal of intrinsic shapes, including all of those supported by the ODB++ format. Some shapes will have the same tags: diamonds, bullets, ellipses, rectangles, and oblongs are all defined by width and height. Others are more complicated and require additional parameters. When you are creating new or editing existing aperture wizards, you must match the tag sequence and format with those values that are provided in the aperture lists you want to import.

For example, the CAM Editor's own wizard begins each line format with the D code tag: <D>. Next, the shape is identified by its name, followed by its dimensions. A space in the Line Format between tags translates to the space between one character and the next, so it could correspond to a series of spaces or tab delimiters. The string tag <S> refers to any set of characters isolated by such spaces.

Failures to import an aperture list are reported. Although the list may continue to import, the best practice would be to identify the errors, update the wizard accordingly, then import the aperture list again.

The following table is a complete list of the tags recognized by the CAM Editor. The latter portion of this article provides examples of each shape supported by the editor and dimensions showing how these tags relate to each shape.

The Aperture Wizard dialog accessed by choosing the Tables » Aperture List Wizard command from the main menus is used to create a new aperture wizard template or edit an existing one. An aperture template is used by the CAMtastic Editor to recognize the apertures used in imported files and therefore build an accurate DCode list.

The dialog is divided into the following three tabs:

• Settings tab – use this tab to define a name and associated extension for the required template. Further options on this tab allow you to specify where to look for aperture definitions in a particular file, the units to be used, and whether to search for more than one aperture definition on each line of an imported file.

• Line Formats tab – use this tab to define all shapes and data sequences that the template will be able to recognize. In the Shape field, select the applicable shape from the drop-down list. In the Line Format field, enter the data sequence for the shape selected. For each shape specified, the Line Format must include the following:

  • An aperture position typecast (e.g. <A> or <D>).
  • A shape description (e.g. "ROUND", "RECTANGULAR", "OCTAGONAL", etc).
  • At least one size typecast (e.g. <W>idth, <H>eight, etc).

  The simplest way to create the Line Format for a particular shape is to paste the line of information for that shape from the aperture file into the Line Format field and then work through the line, replacing actual data with the appropriate typecast, selected from the typecast drop-down list (to the right of the Shape button).

  Use the Shape button to enter a shape template entry - "MyShape" - into the Line Format field. Simply change this to the name of the shape you require.
• Parse Errors tab – this tab is used to list any errors that are found in the information entered on the Settings or Line Formats tabs, when you attempt to save the template.

After defining the wizard template as required, click the Save button. If all information entered is free of errors, the template file will be created (<WizardName>.awr) and stored in the System\aptwiz folder of your software installation. If errors do exist, they will be listed on the Parse Errors tab of the dialog. Use the error information listed thereon to aid in resolving the errors, and then click the Save button again.

Aperture Table

The Aperture Table (displayed in the Edit Apertures dialog accessed by choosing the Tables » Apertures command from the main menus or using the Shift+A keyboard shortcut) has the task of listing all apertures currently defined for the current document in a single table. Each aperture has a DCode assigned to it. When drawing objects in the workspace for example, the DCode is used to specify the associated aperture used for drawing. Each aperture that is created must have a shape and size defined. Certain shapes can have further, special attributes assigned. Use the dialog to edit the definitions of existing apertures or create new ones.

No tags are common to all aperture shapes. Instead, the aperture table includes a Size (X:Y) column, which only sometimes corresponds to horizontal and vertical measurements. Those shapes, which only have one dimension, such as square and round shapes, and the Y value you enter in this table will be ignored and overwritten with the X value.

For all other shapes, the X value will be the horizontal or an otherwise dominant dimension, and the Y value will be the vertical or otherwise secondary value. For example, a Donut has two dimensions: inner and outer diameters. The X value will be the outer diameter since it constrains the inner diameter. Any additional tags will correspond to the fields in the Aperture Data dialog, which is available for complex shapes, such as Moire, by clicking within the associated Parameters column. Complex shapes may also access the Rotation (deg) drop-down, where you may select the desired rotation value.

Hovering the mouse over the Size or Parameters fields in the Aperture Table of the Edit Apertures dialog will display tooltip information, in which the values are associated with the corresponding tags for that particular shape, as shown.

Supported Aperture Shapes

The following is a list of the aperture shapes supported by the CAM Editor. For each shape, the associated tags used to define the properties of the shape are also shown.

Converting Drawn Pads to Flashed Apertures

To convert selected drawn pads to flashed apertures and have new apertures automatically created and assigned, depending on the object being represented, choose the Edit » Groups » Automatic command from the main menus. After launching the command, the cursor will change to a small square and you will enter conversion mode. The procedure involves the following sequence of actions:

1. Click on the drawn pads that you wish to convert to flashed pads, making them selected.
2. When all pads have been selected as required, right-click. The Draw Flash (Auto-Detect) dialog will appear. The dialog offers the following:
   • In the Shape/Dcode for New Flashes region of the dialog, you can choose to assign an existing Dcode to the selected pads, or create a new one. If you choose the Create New Dcode option, then the shape you choose in the Shape field will be applied to all pads in the selection, varying the size automatically in relation to the pad being represented. The CAMtastic Editor will detect the sizes required and automatically assign Dcodes for each new instance, starting from the first available (empty) Dcode.
   • If you choose the Use Dcode option, the same Dcode will be applied to all pads in the selection, regardless of their differences.
   • You can choose to have the resulting flashes drawn on the same layer, a new layer, or any one of the existing layers in the current document.
   • Various other conversion options are available from the dialog, including the ability to set a flash tolerance - when matching pads that are identical in the selection - and whether to keep old pads, or delete them completely.
3. After defining the options as required, clicking OK will perform the conversion and all pads in the selection will be replaced by the appropriate flashed apertures.
4. Continue converting other drawn pads to flashed apertures, or right-click, or press Esc, to exit.

To search and replace all matching instances of a selected drawn pad, with a user-defined flashed aperture, choose the Edit » Groups » Selective command from the main menus. After launching the command, the cursor will change to a small square and you will enter conversion mode. The procedure involves the following sequence of actions:

1. Click on the drawn pad that you wish to use in the conversion, making it selected.
2. With the template drawn pad selected, right-click. The Draw Flash (Selective) dialog will appear. The dialog offers the following:
   • In the Shape/Dcode for New Flashes region of the dialog, you can choose to assign an existing Dcode to be used, or create a new one. If you choose the Create New Dcode option, you will be able to specify both a shape and a size for the new aperture. The CAMtastic Editor will automatically assign this new aperture to the next available (empty) Dcode.
   • You can choose to have the resulting flashes drawn on the same layer, a new layer, or any one of the existing layers in the current document.
   • Various other conversion options are available from the dialog, including the ability to set a flash tolerance - when searching pads for a match with the initial selected pad - and whether to keep old pads, or delete them completely.
3. After defining the options as required, clicking OK will return you to the design space, and you will be prompted to select the entire area to be flashed. Simply drag a selection box around the whole design and then right-click once the area has become selected. The selected objects will be compared against the initial selected pad, and all matches found will be converted to the defined aperture.
4. Continue selectively converting other drawn pads to flashed apertures, or right-click, or press Esc, to exit.

Creating Custom Apertures

A new custom aperture can be created from one or more selected draw objects in the current document. To do so, choose the Edit » Groups » Draw to Custom Aperture command from the main menus. After launching the command, the cursor will change to a small square and you will enter custom aperture creation mode. The procedure involves the following sequence of actions:

1. Click on the draw objects to be included in the conversion, making them selected.
2. When all draw objects have been selected as required, right-click. The Enter Value dialog will appear, from where you can enter a name for the custom aperture.
3. After defining the name and clicking OK, the selected draw objects will be removed from the document and the resulting new custom aperture will be added to the Edit Apertures dialog (Tables » Apertures). The aperture will be assigned the next available (empty) Dcode, its shape will be set to Custom, and the name you specified for it will appear in the Parameters field.
4. Continue converting other selected objects into custom apertures, or right-click, or press Esc, to exit.

To convert a custom aperture object into its constituent base objects, choose the Edit » Explode » Custom Apertures command from the main menus. After launching the command, the cursor will change to a square and you will enter custom aperture explode mode. The procedure involves the following sequence of actions:

1. Select custom aperture objects to include in the explode. Simply position the cursor over a custom aperture object you wish to include in the selection and click. Clicking away from an object allows you to drag a selection area, for including multiple objects in the selection. Selection is cumulative.
2. Once all custom aperture objects are selected, right-click. The selected custom aperture objects will be converted to their constituent base objects.
3. Continue selecting further custom aperture objects to explode, or right-click, or press Esc, to exit custom aperture explode mode.