Frequently Asked Questions
How do I decide how many layers I need to use in my design?
[ PCB Design / Design for Manufacture ]
When starting a PCB design you will need to decide how many layers the design should have. Sometimes the number of layers is pre-determined by outside factors, at other times you will need to decide yourself. There is no easy answer to this but experience will help you decide.
If the board is very small and very dense with surface mounted devices, then more layers may be required.
If the board is large and not very dense, less layers can be used.
In general, the fewer layers you have, the cheaper the board will be to manufacture but note that if EMC requirements are stringent, extra power plane layers may be required. For optimum EMC performance, these MUST be placed on adjacent layers which is why it's common to use paired inner layers for this.
For any design, you can add or remove layers once it has been started - this is an easy process, but only empty layers can be removed so any items present only on the unwanted layer will need to be deleted or moved to a different layer. Items such as pads or vias not specifically defined on the layer will not cause a problem. When a layer is empty, the cross at the left hand end of the entry in the 'Layers' table (see below) will disappear.
To change the design you must edit the layers. Here's how.
1) Go to the Settings menu and Design Technology.
2) From here, select the Layers tab.
3) Use the Add button to display the Add Layers dialog.
4) From here you can add all types of layers – Electrical, Non-electrical, Construction and Documentation.
5) To remove layers (providing they aren’t already used - you can't remove layers in use), select the layer then press the Delete button. If the layer has an X next to it, this indicates it is used and will require items removed. In rare cases there may not be anything on the layer, in which case you will need to check the tabs under [Settings], [Defaults] as it may be simply that it's locked by being specified as a default on one or more of the tabs.