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Guild: wafer.space Community
Channel: 🏗️ - Designing / cob / CoB PCB and die sizes
After: 04/30/2026 23:59
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[05/24/2026 10:55] mole99



[05/24/2026 10:55] mole99
Hi Andrew,

I'm still not sure what underlying problem you mean. What was the reason that you decided to rotate the 1x1 die on the CoB PCB? Is this still an issue, or can we just have the 1x1 die in an upright position?

I'm not exactly sure what your diagram is showing? These are the 1x1, 0p5x1 and 1x0p5 dies. The 1x0p5 die is rotated by 90° for easier bonding access I assume. What do the arrows mean? What do you mean by "fiducial", the wafer space logo? If you rotate the 1x0p5 die, the logo will end up in a different corner.

We could consider changing the template for the 1x0p5 die so that the height becomes the longer side in the GDS. This would mean that the wafer space logo could be in the top left corner in both the GDS and when the die is placed on the CoB PCB.

I agree that we should harmonize what we can between the different slots sizes. What are your plans with regards to matching the pinout?

PS: Looking at the CoB PCB for the 1x1 slot, pin 1 of the mezzanine connector seems to be in the top right corner rather than the top left. Why is that the case?


[05/24/2026 14:25] rebelmike
My feeling is that we probably don't want to rotate either of the half slots, as that would cause more inconsistency in the project template (and I don't think it is necessary to make the CoBs routable).

I think the non-power pins in the default templates should be harmonized so that by default there are the same number of pins of each type, in the same order, starting from the same spot.  For the quarter slot I'd reduce the number of biderectional to 32 but keep everything else the same (2 analog + 12 inputs).

Obviously you expect people to customise the pins, but if there was a clearly documented pinout of the 70-pin connector that matched the default template, and the template was consistent across the slots, it should reduce confusion.

It would be good to fix things so that the die didn't need to be rotated.  I suspect changing the project template to move power pin locations would be unpopular at this point, so my feeling is the best fix would be to change the CoB pinout.  That would obviously mean if a project was on both run 1 and run 2 it would need a motherboard respin.  Unless maybe the mezzanine pinout could stay the same except rotated 180 degrees, then you could just plug the run 2 CoBs in rotated 180 degrees compared to run 1 CoBs?


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