Electronics > KiCad

Do I need to move to a 4 layer PCB

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newtekuser:
Long story short, I have a project using a PIC16F887, some darlington transistors ICs, a schmitt trigger IC and a 16x2 LCD. All ICs are in TQFP format, lots of pins are used and I am unable to route the traces between all connections (using Kicad6) using a 2 layer board.
There's always some trace, or more that overlaps another.

Do I need to move to a 4 layer layout, or is there something I'm missing in PCB design to make this happen?

Thanks!

ataradov:
Can you post pictures of what you have so far? Overlapping traces are fine as long as you still have place for vias. I don't see why PIC16 and a couple other ICs would need 4 layer board.

fourfathom:
You may not *need* a four-layer board, but (at least with JLCPCB) the cost difference is essentially zero.  I have a few boards that I was able to route on two layers, and they worked fine.  But I switched to four layers a few revisions back and got a much cleaner layout with good power and ground planes.  It may not have been necessary, but I'm much happier with the layout, electrically and aesthetically.  I used KiCad v6, and KiCad v7.

mariush:
I'd also like to see what you have so far.

Consider adding some 0 ohm resistors / jumper links to go across some top traces if needed, this way you wouldn't have to break the bottom ground layer or you could use both top and bottom for traces.
If the 16x2 LCD wiring causes issues maybe you could add a serial to parallel IC and have the microcontroller push 8bits through 2 traces. It's a few cents, may be cheaper than going to 4 layers.

wraper:
You only need 4 layers if you cannot route the thing on 2 or for signal integrity and EMI reasons if circuit has very fast signals. As of your description, sounds like it can be done on single layer with some jumpers.

--- Quote from: fourfathom on March 04, 2023, 05:12:49 am ---You may not *need* a four-layer board, but (at least with JLCPCB) the cost difference is essentially zero.

--- End quote ---
Only for small batch of tiny PCBs and only on special offer, so likely will change after some time.

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