Need help spotting a PCB short - Page 1
Forum section: electronics / projects

author: thinkfat
author_rank: Unknown
timestamp: May 04, 2019, 07:50:08 pm
content: Hi,I've recently received some PCBs from manufacturing and they're all faulty, they have a solid short between the ground plane on the first inner layer and the 3.3V power plane on the second inner layer. The PCBs were made with KiCad and they pass DRC. I've attached the Gerber files and also the KiCad PCB file here, I'd be glad if you could help me find the problem with my design. The minimum track/clearance should be 6/6 mil. The PCBs were made by Aisler, I have used them before and I was always happy with the results.The KiCad PCB file has been renamed as .txt due to restrictions with file types, you can just rename it back to .kicad_pcb.Thanks,Matthias

author: langwadt
author_rank: Super Contributor
timestamp: May 04, 2019, 08:26:11 pm
content: Quote from: thinkfat on May 04, 2019, 07:50:08 pmattach a big powersupply and see where it gets hot

author: thinkfat
author_rank: Unknown
timestamp: May 04, 2019, 08:46:42 pm
content: Quote from: langwadt on May 04, 2019, 08:26:11 pmTried, 12V@5A, can't make it budge. The only place that gets warm is the immediate vicinity of the pads where I inject the power. I tried multiple locations. I don't have a thermal cam or freeze spray, so I'm spraying the board with IPA.

author: thinkfat
author_rank: Unknown
timestamp: May 04, 2019, 08:54:42 pm
content: Bah, nevermind. I found it. You won't be able to see it in the files I uploaded. I re-downloaded the PCB file directly from Aisler and it seems I had forgotten to re-fill the polygons after a rushed last-minute change. There's two GND vias that connect the 3.3V plane and the GND plane :-(I feel stupid. Proof of my failure attached.

author: jbb
author_rank: Super Contributor
timestamp: May 04, 2019, 09:13:47 pm
content: I know the feeling. Can you drill out the offending holes to break the shorts?It turns out that the PCB house will generate their flying probe e-test from your Gerbers, so a flaw in your Gerbers will be faithfully built and sent to you :-(

author: thinkfat
author_rank: Unknown
timestamp: May 04, 2019, 09:23:07 pm
content: Quote from: jbb on May 04, 2019, 09:13:47 pmNo, I don't have anything for drilling 0.4mm holes. It would also leave a some pads unconnected, unless I added some jumper wires...The thing is - had I actually sent Gerbers, this wouldn't have happened, since KiCad would re-pour the polygons before plotting. But no, I wanted the easy way and sent the PCB file to Aisler, which they happily processed, including the fault.

author: OM222O
author_rank: Frequent Contributor
timestamp: May 04, 2019, 10:14:26 pm
content: I know this might be a bit off topic, but you can also try EasyEDA + JLCPCB. the software is made by them, so it's optimized with their manufacturing setup. the prices are ridiculously low as well so if there are faults, you won't lose much, mainly the shipping cost

author: jmelson
author_rank: Super Contributor
timestamp: May 05, 2019, 12:35:17 am
content: Quote from: thinkfat on May 04, 2019, 09:23:07 pmI always send the Gerber files, ONLY. (I use Protel 99) But, what I do is generate the Gerber files, then READ them back in and view each layer. Hopefully, one would spot a missing pour or something that big while looking at the layers.Jon

author: thinkfat
author_rank: Unknown
timestamp: May 05, 2019, 05:29:19 am
content: Quote from: OM222O on May 04, 2019, 10:14:26 pmNo shilling for JLCPCB required, I use them frequently, I also used Easyeda in the past, but IMO KiCad is the better EDA package, and it's not web/cloud based. All design files are local and I can do my own publishing e.g. on Github.I chose Aisler for this little project because they're a European shop and that means less hassle with shipping and no taxes or customs duties. 3 boards 4 layer with ENIG finish were 28€ and shipping is free. The same PCBs on JLCPCB are 25€ but to have them delivered in a reasonable time frame I have to use DHL express shipping which adds another 16€. That puts me past the magical border above which I have to pay 19% import VAT on top. Also, DHL charges another, hefty fee for handlind taxes and duties. And if I don't let DHL do the handling, the PCBs will sit in a customs warehouse until authorities decide to contact me. Then I need to get the shipment released and DHL to do the final delivery. It's a big nuisance, not really worth it.

author: OwO
author_rank: Super Contributor
timestamp: May 05, 2019, 06:04:58 am
content: Only send gerbers for fabrication, and always check the gerbers with multiple viewers. I use the oshpark and easyeda gerber viewers.