If you open the attached PCB you will see a group of pads connected by traces (all blue). All the pads are outlined by rectangles, and lines are then used to join all the rectangles that are connected by copper. The lines and rectangles are then trimmed to create an "island" that contains all the copper that is connected together. The attached image shows an example, and is part of the board shown on the last e-mail. Please note if you look carefully at the full board, there is an error where an island has a missing pink line, allowing it to connect to the ground plane.
This is only one layer of the PCB, the bottom layer in this case. The blue area is the copper on the layer as designed with the PCBlayout program. The black lines are where the copper would be removed if the board was etched at a PCB fab shop. The dark grey dots are pads that would have a hole drilled through the board for mounting a component or connecting a wire. The pink lines are the lines that will be cut by my CNC machine, removing the copper. I would follow up by drilling holes in the pads for component mounting. Note that the area labeled Island 1 has 3 pads connected by a copper trace. When the copper is cut on the pink lines, the three pads are isolated from the rest of the copper just as if it were cut on the black lines. I could have used the CNC to cut on all the black lines, but that would take more time and might not leave enough copper for the trace, perhaps causing it to lift from the board from the cutting forces. The region labeled Island 2 also contains 3 pads. The region labeled Isolated pad has only 1 pad, which has no connections on this layer. It may have a connection on the top layer (not shown), or it may be an unused pin on some component. The bulk of the blue area is ground plane, only part of it shown on this example. The ground plane connects all the pads on the board that are connected to ground.
The top layer of the board may also have a pattern connecting pads, or perhaps this is a single layer board. Note that if it is a double layer PCB, and if any pads connect to both top and bottom layers, the wire or component lead must be soldered to both sides of the board. Sometimes it is necessary to use a VIA to connect top and bottom layers, which would be done with a plated through hole if built by a PCB fab shop. Since I do not have plated through hole capability, I install a wire and solder it to both layers, unless it is a lead on a component that is not hidden underneath the component.
I generally like to use surface mount components for as much of the design as possible since there are less holes to drill. I usually hand solder the components onto the board since I do not have solder mask capability. To avoid future corrosion problems I generally use flux and solder coat the entire copper area of the board before adding components and wires. Of course you need to check all the cuts to make sure you do not have a solder bridge or copper whisker shorting adjacent islands before adding components.
It is always a good idea to consider how the board will be soldered when performing the PCB layout since it can be difficult or impossible to solder wires or leads to the pad if the pads are located under a component, so I try to design all my boards to use vias located outside the component for these connections. Sometimes vias can be located under a component, but a wire must be soldered to both layers before the component is placed on the board. If this does not make sense now, it will become more obvious when you actually build a few boards. It is also good to remember when laying out the board that metal cases on components may short to the bare metal underneath since there is no solder mask.
Note that I tend to leave as much copper as possible on the board, and only remove it where needed to isolate pads. This makes it much easier to machine the cuts, and if you are etching the board, it requires less etchant and less time to remove copper.
I hope this answers your questions.
Bob
