JLCPCB messing with my vias - Page 1
Forum section: electronics / general

author: Nogtail
author_rank: Regular Contributor
timestamp: June 09, 2025, 02:13:00 pm
content: I'm reviewing the production files for a board I ordered from JLCPCB and noticed they've expanded the copper around my vias. I understand this is done to compensate for the etching process. I've previously only seen it applied uniformly across the board, but in this case, the vias have been expanded significantly further than the rest of the copper.Usually, I wouldn't worry about this, as I try to design with plenty of margin. However, this board is quite compact, and I don't have as much margin to work with. My design uses 0.25mm spacing, and vias have a 0.5mm diameter and a 0.3mm hole size - twice the size of JLCPCB's minimum capabilities.In places where vias are close together, the expanded copper reduces spacing from 0.25mm down to 0.1mm. My original design is shown in blue, via holes in green, and JLCPCB's production file in red:I know the spacing should increase after etching, but I'm a bit concerned as other copper has not been expanded nearly as much.

author: thm_w
author_rank: Super Contributor
timestamp: June 09, 2025, 09:38:33 pm
content: Is the voltage high enough that you are worried that 0.1mm is not enough space?I get its irritating but I don't see what the issue is if they make this design.That or its just someone screwed up the hole expansion value and set it too big.This is regular 1oz board right?

author: Nogtail
author_rank: Regular Contributor
timestamp: June 10, 2025, 01:44:29 am
content: Quote from: thm_w on June 09, 2025, 09:38:33 pmIn some cases it might see PoE voltages (57V) which by my calculations needs around 0.18mm spacing. In the example I showed the voltage should be limited to 12V, but there are problems across the board. Assuming the vias are etched the same amount as other copper has been expanded (0.03mm) this leaves me with 0.16mm spacing on the finished board.Quote from: thm_w on June 09, 2025, 09:38:33 pm2oz outer layers and 1oz inner layers - it's got to handle around 10 amps and I didn't have the room for super wide traces. The outer layers have a much larger copper expansion, which I assume to compensate for etching 2oz copper. I can't think of any etching process that would need vias to be expanded further than the surrounding copper. Other plated through holes on the board aren't affected, just the vias.

author: thm_w
author_rank: Super Contributor
timestamp: June 10, 2025, 08:47:30 pm
content: Quote from: Nogtail on June 10, 2025, 01:44:29 amYeah that would explain the 2oz but not the vias as you say. I would ask them.Or if its a prototype just not care and see what you end up with.

author: Nogtail
author_rank: Regular Contributor
timestamp: June 10, 2025, 11:26:37 pm
content: I sent it back to the chef and they fixed it up. I'll take a look under the microscope once I get the boards to see how it ends up.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: June 11, 2025, 11:44:06 am
content: I'm not sure this is/was for etching compensation. Maybe it's for the drill tolerance and minimal annular ring width.Another option is to go for a 4 layer board. Those are more expensive, and this is not only for the extra copper, but in general multi layer PCB's are also made on more precise machines.

author: erikfriesen
author_rank: Newbie
timestamp: July 17, 2025, 11:52:01 am
content: Once you start looking at boards under a microscope you begin to realize how some of these pcb manufacturers are cutting corners. If they fiddle with your files they can run pcb’s in a lower resolution process. I think they expect you to want the cheapest process.