Modern PCB fabrication techniques and technologies are changing the way that the humble printed circuit board is delivered. Rigid-flex structures have components mounted on the outer layers of both the rigid and flex areas, with those flex-mounted components actually being mounted on layers that become inner layers within the rigid-areas. Embedded components are also mounted on internal layers. Changes such as these mean the original concept of a top-side component or a bottom-side component, is simply no longer adequate.

Mounting Components on any Layer

To support the changes in how components can be mounted, the PCB Printout Properties dialog and the Printout Properties dialog have been updated. They no longer refers to Top, Bottom or Double Sided components. With the release of Altium Designer 16, these dialogs now have Surface Mounted and Through-hole options. If a component includes both surface mount pads and through hole pads (or vias), then you enable both check-boxes.

In the old approach, where you selected the side of board, the software could use this setting to determine if the contents of the enable layers needed to be included in the top side assembly drawing, or the bottom side assembly drawing. With this simple system, it did not matter if the same mechanical layer was used in both a top side component and a bottom side component, because the side of board setting was the primary flag used to decide if the primitives within this component needed to be included on the printout.

Now that components can be mounted on any layer, a different approach must be used. In the new approach, the software classifies the component based on its pads, as either Surface Mount or Through-hole (if there is a multi-layer pad or via present). It will then include that component in the printout if it has any primitives on any of the layers included in that printout. The Through-hole checkbox is used by the software to check for components that appear on all signal layers - if it is on, then the multi-layer objects within the components are included on each signal layer that is in that printout.

A comparison of the changes to the PCB Printout Properties dialog from Altium Designer 15 to Altium Designer 16. Note that mechanical 7 is used in the top assy dwg, and mechanical 8 is used in the
bottom assy dwg, these layers are paired.

The Impact on how Mechanical Layers are Used

With this new approach, if a component has primitives on an enabled layer, then that data will be included in the printout. This changes how mechanical layers are used in components, as the software can no longer rely on a side-of-board flag to help work out if mechanical primitives should be included.

Now you must ensure that mechanical layers used for components are paired, so that an instance of a footprint used on the top side of the board, does not share a mechanical layer with an instance of that same footprint used on the bottom side of the board - if they do, then those primtives will appear in both the top-side and the bottom-side printouts. You achieve this using Altium Designer's Layer Pair feature.

The component footprint is still designed as before, as a top-side component. The mechanical layers are paired in the PCB editor as part of the board design process, in the View Configurations dialog. When you flip the component to the other side of the board, mechanical objects are automatically flipped from the original mechanical layer, onto the paired mechanical layer.

Assembly printouts are created from the enabled layers, in combination with the enabled component types.