Hi Everyone, I have designed my own 4 layer board in Eagle PCB and had it made by JLCPCB who I have used for quite some time. Strange thing is, I have a short circuit between my 5V net and my GND net on the board. I ordered some boards fully assembled and some blank and I have the fault with both lots. I have scanned and scanned through my schematic but cannot find anywhere that the two nets join. Obviously it isn't any of the components as it is like it on the bare boards as well. I have run the DRC and ERC tools in Eagle to check I didn't miss anything before ordering and that comes up fine. Does anyone have any ideas how I can work out where the issue is please? It is a small board so trying to use a multimeter to check the resistance isn't really working.
Do you have a Gerber viewer so you can see the short or maybe where things are "close".
It's possible that something went wrong with the fabrication process... Maybe a layer got shifted or rotated or something. I've seen fab-shorts on occasional boards but if it's the whole batch it's usually a design problem.
If you can't find anything you can start drilling-out power & ground vias and component holes on an unused board and you might locate the problem by drilling-out the thru-plating.
Hi,
my suggestion to find the spot where the short is is a little drastic but I think it has a chance of working.
Use a high current source and place it between +V and GND on your board.
The short circuit site will heat up a lot or even burn out.
It will likely damage a PCB.
Thank you so much for coming back to me so quickly, your replies have been very interesting and certainly routes I will take in the future. I actually stumbled on the underlying error myself. For some reason, even though I had run the ERC on eagle many times, I created a copy of my eagle files (so i could make changes) and once I had opened the "copy" and run the ERC it showed I hadn't set the rank correctly on two polygons, one 5V and one GND. And guess what, when you do this it merges them!