Frequently Asked Questions
Finding isolated poured copper
[ PCB Design / Poured Copper ]
After a copper pour, it is quite common for there to be areas of copper which are isolated from the main pour. Clearly this increases rather than reducing crosstalk, so a means of identifying and removing them is needed.
The Pour Copper command has the ability to remove these isolated 'islands' as it goes along, but it is possible that later changes to the routing might leave previously connected copper pieces as isolated.
The simplest method of finding isolated islands is in the dialogue when pour copper is selected In the 'Isolated Islands' section are two options, 'Remove' and 'Highlight'. Initially you should pour with 'highlight' selected. By studying the poured areas showing in a different colour, you can determine whether minor changes in tracking will provide a route for these to link to the main pour area. If an isolated area is large, but the signal is available on another layer, consider adding a via to provide a signal route. Where these options aren't possible, changes in tracking can minimise the size of the isolated area, bearing in mind the risk of introducing crosstalk between adjacent tracks. After making changes, clear and repour the copper to reassess the situation, only opting for the 'Remove' option when you are satisfied with the result.
Early versions of the program may not include the 'Isolated Islands' option. Where this is so, a different approach must be used. To demonstrate this, it is assumed that the copper pour is part of net 'Gnd', and that the islands will become part of net 'Temp'.
First, highlight the main part of the completed copper pour, then right click and select [Net], [Change Net]. Set the new net name to "Temp" net class 'Power'. Immediately return to [Net], [Change Net], and rename back to "Gnd", class 'Power' as before, but this time tick the box marked 'Change Name Of Subnet Only'. Now select [View], [Highlight Net], and type 'Temp' in the box. All the isolated islands will highlight ready for connection or deletion.