My Hobbies - Circad Course - Lesson 9
Jumper wiring in board Routing

Parabola

Barra Colore


Imagine to have a pcb like the one beside, where the pads must be connected like is showed by the ratnest lines. There are no possibilities to turn around the pad externally, because the pcb cannot be bigger than showed and is also not possible to move the pad because the component mounted over the pcb have the pads at the distance showed in the image. The pcb only have one single layer, then, teorically, we can only directly wire the two central pads.

When it's not possible to completly unroute a single side pcb using only copper tracks placed into the layer Bottom Copper, the only solution is to use jumpers placed over the component layer. To create a jumper place two pads, with PP, near the track that must be crossed, then, using PL, connect the pads togheter with a Top Copper layer signal line. Then, the two jumper ends will be connected to the pads that, before, we are not able to get wired togheter, using a Bottom Copper layer signal line.

When you create a jumper, the jumper pads are electrically wired togheter only if you use signal track line. The signal track cannot be placed over the same layer of the track that we want to cross. In this case, in fact, we'll have a short circuit! It is not correct to make a jumper using a silk jumper line, because so there are no electrically connection between jumper pads.

In fact, using NS over a pad of the line above, we can see that the line is correctly wired.

When in a circuit there are some jumpers, sometimes, using NS over a track, or N+ on the entire circuit, Circad yellow hilights a specific pad, with the message "Signal is linked to unknown pins" over the status line. This happens because the components pads, and also all the pads automatically placed by Circad, have a name, showed into the netlist and that you can see with EP over a pad, but the manually placed pads don't have an initial name ("Pin name"), if you don't set it first.

So, every time you'll obtain a message like the above, you'll must assign at all the "anonymous" pads connected by the same signal line the name of the track, like GND, +VCC or $000003. To known the track name you must use EP over one of tracks pads.

Now, try to make a jumper in the TUTOR1.PCB pcb file, over the track that connect the CONN1 pin 3 at the Q1 emitter pin. Now, with DL delete track section parallel to Q1, then, with PP place two pads over the extremity of the deleted track. Now, with PL place a 40 mils thickness, Top Copper layer track, between the pads placed before.

Using NS over the track, or N+ to check the connection of the entire pcb, you'll see that the jumper track electrically connects CONN1 and Q1. If you obtain the messagge "Signal is linked to unknown pins" in the status line, use EP to modify the "Pin Name" field of the jumper pads, using the same name of the pad 3 of CONN1 or of the Q1 emitter pin (the names are the same because the pads are wired togheter). If you use a silk line to connect the jumper pads, like in the imagine beside, you'll obtain an error message like "Signal routing is not complete" and a ratnest line will be automatically placed between jumper pads. This means that the hilighted segment track is not electrically connected.



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