Unintended plates holes | Caused by laser cutting? | JLCPCB - Page 1
Forum section: electronics / general

author: ju
author_rank: Newbie
timestamp: March 08, 2019, 12:00:34 am
content: Hi!This is not a question, but simply an interesting discovery I made.Maybe someone encountered similar things or are interested in a discussion.I ordered some PCBs from JLCPCB and a few days ago they arrived.After a quick inspection I discovered something interesting.The PCBs are daughterboards and had to include a clearance hole for a rotary encoder on the board below.I added a decent amount of pullback to the ground planes.But still, the holes got plated.I wondered a bit but then remembered something I discovered on JLC boards before.JLC seems to use laser cutting instead of milling for holes and probably slots as well. This can be seen at the hole edges, as they are burnt as laser cut edges are:When I remember correctly, to plate through holes intendedly PCB manufacturers use a conductive inc and cote the inside of the holes with it to be able to do electroplating as the next step.Now my PCBs make the impression that the carbonization by the laser may have encouraged copper deposition during the plating process.While writing this post I realise that this may become an issue if you are not careful enough during design stage and / or the pullback around holes it not big enough.Here is one of the holes partially plated, you can see a nice little nick in the platingI personally don't care, in my case it just makes the PCB look a bit more polished and beautifulCan you imagine cases in which this can become a serious issue?Do you agree with my analysis or do you have any other thoughts on this?Did you maybe experienced something similar with JLC or other, maybe high priced, manufacturers?Hope you find my first post somewhat interesting.Have a nice evening and an amazing weekend!Greetings from Berlin

author: Kean
author_rank: Unknown
timestamp: March 08, 2019, 12:26:00 am
content: Plated holes are drilled early in the process, while non-plated ones are usually drilled near the end. So normally you would provide different NC drill files for the plated and non-plated holes. Or if the hole is reasonably large (like your one is) then it can be milled and included in the milling or dimension layer.Usually the fab staff will notice the ground plane pullback and realise that certain holes are meant for mounting and should be non-plated, but if you really care you need to specify it.Looking at some non-plated holes on PCB's I received from JLC, I do see the same black finish you mention. I hadn't noticed that before, but it doesn't quite look like laser cut to me. Not sure.

author: ju
author_rank: Newbie
timestamp: March 08, 2019, 12:34:19 am
content: Well, I actually specified it as non-plated. It was defined on the same drill layer as all non-plated mounting holes I have.Also, half of the boards are completely non-plated as intended, so I don't think it's something I did wrong.Well, other PCBs I ordered from Eurocircuits or also from JLC longer ago had usual drilled holes. They looked the same as the boards edges. Also I once needed to open up one of the blackened holes by .2mm with a drill and the black surface was gone.So there must be something different in the process.I also wonder if the holes "huge" surface may have played a role together with the black stuff, whatever it may be in the end