[Feature Request] Chip on Board Addon


#1

Dear Developers,

first of all I want to thank you for this nice software. I am all new to this but it was quite easy for me to get started. For me it was easier to grasp than EAGEL.

Currently I am learning KiCAD to be able to do chip on board (COB) PCBs. For COB I would need an extra feature to do wire bonds and to export bond coordinates.

I picture this like that. In case you have a n-up/p-down LED die. The footprint would be simple square for p on the copper layer (current standard). For n I would need to be able to add a special “pad” on a new layer that symbolizes the top of the die. This new layer must be able to hold several pads since some dies can be connected multiple times.
In pcbnew I would need to additional functions. One that allows me to place bonding areas on the PCB. This would look like a standard footprint but without needing a component on Eeschema. Since sometimes it is possible to bond a die from different directions I do not want to add the landing pad to the footprint. The lading pad needs to be free to place. The second function would be a way to place wirebonds. Wirebonds should be addable like tracks. The wirebonds are straight lines connecting a) any top pads to any other top pad or landing pad and b) any other two pads.
Here is how I picture a print out:
cob
The wirebonds should be handled like tracks so that all current checks still work.

Additional Features:

  • Specify thickness of bond wire
  • Check loop length
  • Check for max. current allowed for wire
  • Table with bonding coordinates

Is this something that is possible within KiCAD? I have a little programming knowledge with Qt and PHP. If I could help implementing this I certainly would.


#2

This here is a user forum. Developers do not really monitor it.
Feature request should go onto the launchpad bugtracker. https://bugs.launchpad.net/kicad


#3

This is interesting but difficult to understand. I looked into some explanations of COB. As far as I can see it’s just a normal component. The only difference being that the footprint pad locations aren’t necessarily fixed - but that can be true for any component. And KiCad allows moving pads independently when you select that option in the footprint properties. How the component is physically attached and how the wires are attached don’t belong to the board design IMO. It’s the same as with any component, say a leaded resistor. You can spread the leads and the footprint pads need to be moved. You can glue it into its place. You can replace the leads with wires or pieces of metal. It’s still a normal component with a symbol and a footprint.


#4

I did not see the option to be able to move pads. I need to check that out. Currently I just do different version of the same footprint if I want to bond in another direction.
But if I want to do a bridge with a wire bond, then the automatic checks will not work because KiCAD has no way to know that things are connected with a wire.


#5

Footprint properties -> Move and place -> Free

It doesn’t know it things are connected with a 0Ohm resistor, either, if you choose to use that. It’s not a job of the software.