KiCAD: Connections are not the same in schematic and pcbNew

Question

This is a portion of my schematic:

Now, I try to create the traces in pcbNew.

Here is the portion of pcbNew:

In the schematic:

• C4 is connected to pin 1 of U1 and to pin 2 of U1
• C1 is connected to pin 5 of U1 and to pin 5 of U2

In pcbNew:

• C4 pin 1 is connected to pin 5 of U1 pin 2 is connected to pin 2 of U1
• C1 pin 1 is NOT connected, pin 2 is connected to pin 5 of U2

As you can see, pin 1 of both C1 and C4 are not the same in schematic, and pcbNew.

In the first iteration of my PCB (first PCB ever), I trusted the ratsnest, which I failed.

What is the process to create proper traces in pcbNew?

If you want, I can upload the schematic and PCB files.

Answer 1

The airwires only show the shortest possible connections for each net. If you look at U1, there is an airwire between pins 1 and 5 -- that is the shortest connection from OutA to +InB.

You can insert a dummy component (like a resistor) on the schematic in the path somewhere to split the nets, then place the dummy component next to C1 on the PCB, route the traces, then remove the dummy component again, or you can just draw the traces in the shape you want.

The airwires will tell you only if a connection is missing, not if the geography is not as desired. That would require proper net tie support, which will happen in a later version, probably V7.

Be sure to check that the number of unrouted connections is zero before sending off a PCB to production. Airwires can be really short and difficult to see, but the count (in the status bar) tells you if there are any.

Answer 2

Remember that the schematic only shows what should be connected, not how the actual connections will be routed.

Likewise the airwires in the PCB editor show the shortest path to make a required connection, not necessarily how the tracks will actually be routed.

On both schematic and PCB, C1, C2, C3, and C4 are alll connected in parallel - on the PCB, that parallel connection is made by the vertical red tracks. Since the capacitors are already connected by tracks, there are no airwires showing the connections between them.

The left side of the capacitors on the PCB corresponds to the top of the capacitors in the schematic, and has an airwire from C4 left to U1 pin 5. another airwire connects U1 pins 5 and 1 - these connection correspond to the schematic.

On the PCB, the right side of those four capacitors are connected to U1 pin 2, as shown on the schematic for the bottom of the capacitors.

The connections look correct to me.