Over etched PCB - Page 1
Forum section: electronics / general

author: SKPang
author_rank: Unknown
timestamp: February 02, 2019, 10:53:52 am
content: Just had a batch of PCBs back from a manufacturer and they looked over etched. The tracks are really thin compare to another build.Populated the board and tested it. It seems to be working fine.Do you think the board is acceptable ?

author: xdave
author_rank: Contributor
timestamp: February 02, 2019, 12:07:56 pm
content: It could be over etching, but production panels are normally etched with a series of known sized test lines (positive and negative) around the edge so the fabricator can check the etching against that reference. Unless there is no QC at all, over etched panels should not be processed further.Assuming the design data was the same for both of those, it looks more like the data was adjusted prior to processing. The drills used for the vias are different sizes in the new batch and that is not down to etching. (The registration is also horrible so personally I wouldn't use those if you are using them to carry any current. Maybe OK for bench prototyping but carries a risk for production.)Grab a good set of calipers and measure those traces and the gaps between them - do they meet both your design data and the specs of the producer? If they do then fine, get their design rules and you adjust your data to accommodate them in the future, but if they don't then you should reject them. (And if they didn't tell you they would change your data then find a new fabricator - it is not acceptable to make any change without getting designer approval.)

author: ataradov
author_rank: Super Contributor
timestamp: February 02, 2019, 07:36:44 pm
content: Manufactures may change the trace widths in CAM. It looks like the old board were adjusted and with the new ones they made it as is.What is in the gerber files? I bet it is thinner traces.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 02, 2019, 09:31:22 pm
content: What dimensions and tolerances did you specify on your drawing?If none, it must not matter...Tim

author: mrpackethead
author_rank: Super Contributor
timestamp: February 02, 2019, 10:16:41 pm
content: Those boards are not being manufactured to the same gerber files. The populated gerbers has open vias, the bottom one has tented vias for a start.

author: NorthGuy
author_rank: Super Contributor
timestamp: February 03, 2019, 01:44:35 am
content: Silk screen is thinner as well.

author: dekagon
author_rank: Contributor
timestamp: February 03, 2019, 10:02:54 am
content: Quote from: SKPang on February 02, 2019, 10:53:52 amthe two pictures using different resolutions...So it seems not really comparable I think.The second pic is with greater resolution so the tracks are showing greater as they may are...Gesendet von iPad mit Tapatalk

author: KL27x
author_rank: Super Contributor
timestamp: February 03, 2019, 09:19:31 pm
content: Are you the guy making and submitting the gerbers? Or are you using a middle man? I can imagine some quackier PCB services/manufacturers might untent vias for some reason. I believe just maybe PCB Express does this, but it has been 10 years. And they don't change your Gerber, since their software doesn't give you the Gerber in the first place.The change in trace width, I would not expect a PCB manufacturer to do that. If there was a potential problem, they usually just tell you what it is and wait for a new Gerber.I think it is possible the board was overetched, though. The board will come out with thinner traces but can be otherwise just fine. But this is pretty extreme.

author: ar__systems
author_rank: Frequent Contributor
timestamp: February 05, 2019, 04:16:12 pm
content: Overetched traces will never look this straight. The edges will be all fuzzy.The error here is on the part of the guy submitting the job. Perhaps they employed a different design rules or something.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: February 05, 2019, 06:18:00 pm
content: The populated board from image 0005 looks sort of normal to me, while the other img 007 has weird thick traces.

author: KL27x
author_rank: Super Contributor
timestamp: February 05, 2019, 09:13:18 pm
content: Quote from: ar__systems on February 05, 2019, 04:16:12 pmGood etchant can turn a 12/12 board into a 6/18 board with smooth edges. The inside sharp corners will be noticeably rounded, though. You have to do something drastic to get fuzzy edges to your traces. Like use muriatic acid and peroxide as an etchant.