Silk screen on exposed PCB pads? - Page 1
Forum section: electronics / projects

author: zapta
author_rank: Super Contributor
timestamp: March 07, 2015, 02:48:23 pm
content: I got a small batch of PCBs and noticed that the silk screen was printed also on top of exposed pads. I generated the gerbers in Eagle with the CAM file provided by the PCB vendor. Isn't the stop layer supposed to be subtracted from the silk screen somewhere along the process?The same PCB order from OSHPark (where I uploaded the Eagle file directly) didn't have that problem.

author: langwadt
author_rank: Super Contributor
timestamp: March 07, 2015, 03:14:26 pm
content: most times the manufacturer will remove silkscreen on pads, but some assume what you send is what you want

author: tszaboo
author_rank: Super Contributor
timestamp: March 07, 2015, 03:16:35 pm
content: I would send this picture to the manufacturer of the PCB with a letter that their services are no longer required.

author: nuno
author_rank: Frequent Contributor
timestamp: March 07, 2015, 03:18:22 pm
content: That's one of the things you have to ask. Some manufacturers remove it, others don't.

author: c4757p
author_rank: Super Contributor
timestamp: March 07, 2015, 03:22:18 pm
content: Quote from: NANDBlog on March 07, 2015, 03:16:35 pmFunny, I have the opposite opinion. They should manufacture exactly what you tell them to. If I send them silkscreen on pads, they should either make exactly what I sent, or ask me to confirm. Don't silently modify my files. It's part EAGLE's fault for the moronic silk-on-pads thing that most of their horrid library parts do, and part your fault for letting it through to the gerbers.

author: zapta
author_rank: Super Contributor
timestamp: March 07, 2015, 03:44:41 pm
content: Quote from: c4757p on March 07, 2015, 03:22:18 pm1. That's specific manufacturer does modify gerber files silently. For example, in another board, they changed a large QFN solder paste opening into a grid (which was fine with me).2. I tested the gerber files but always assumed that it's the PCB house job to clip the silkscreen as part of their normal process.I sent am email the the manufacturer. Will see if they consider it as an error or as their standard process.Does Eagle CAM has a way to clip one layer by another?

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: March 07, 2015, 04:57:45 pm
content: Quote from: NANDBlog on March 07, 2015, 03:16:35 pmThat's a bit extreme. Everyone has a first day on the job. I once had a 14 layer Rogers on FR-4 with blind and buried board " in the pipeline", it was super-critical to the company and I was calling the shop every day for updates.On the last day, a new operator loaded the bottom drills and forgot to mirror them so the laser drilled all the vias in the wrong spot. They were quite apologetic and even sent me the panel so I could see it... I still have it here.They then went overboard to get a new panel made.

author: JohnnyBerg
author_rank: Frequent Contributor
timestamp: March 07, 2015, 05:00:59 pm
content: I am with c4757p on this one.I must say that when I did something stupid I got a mail from the fab being asked if I really wanted it the way I send it.Happened with ITead, Elecrow and Makerstudio.

author: ConKbot
author_rank: Super Contributor
timestamp: March 07, 2015, 05:22:41 pm
content: Quote from: c4757p on March 07, 2015, 03:22:18 pmWow, shit libraries, time to throw them out and make your ownOr at least fix them, if youre so inclined and not worried about what other "oddities" there are. Full outlines are for the assembly layer, not the silkscreen.Is there a DRC option for silk to pad clearance in eagle? I know in Altium after I put parts down and do a bit of routing, before I tidy up component designators theres usually a few dozen to a few hundred silk to pad violations that I'm ignoring since I'm worrying about component placement and copper for the moment.

author: tszaboo
author_rank: Super Contributor
timestamp: March 07, 2015, 05:27:01 pm
content: Quote from: Alex Eisenhut on March 07, 2015, 04:57:45 pmYes, usually I'm more polite when doing business, but this is definitely a WTF mail. I mean you basically cannot use the boards, at least you cannot trust the solder joints to be reliable. Probably it is OK for blinking LEDs but I rarely do stuff like that. If this is their usual method of processing the gerbers, you dont want to produce anything there anyway.Anyway, once I had a board, which had concave 90 degrees rounded edges, all 6 of them. Like the rounded edges were mirrored by the milling machine. I sent the manufacturer a mail, they said, they never saw anything like that. Got the new boards two days later

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: March 07, 2015, 05:57:21 pm
content: Quote from: NANDBlog on March 07, 2015, 05:27:01 pmJust scrape off the silkscreen with a pocket knife. It's sharp enough to remove the brittle silkscreen, but too dull to seriously harm the board.Just scratch it off. You'll live. You're in Belgium, you can buy a Saison Dupont Vieille Provision! I can't!As for your corner, is that Allegro? It always had bizarre arc bugs in obscure cases, with exactly that kind of inverted arc, or weird S tangles.Allegro had problems when two identical objects of the same type/subclass are exactly on top of each other. Sometimes it stops the gerber process, sometimes it creates "not a number" arcs.You should always use DRCs to check for silkscreen on pads, Allegro can do that, at least in the higher licenses I used. You should also always verify your gerbers in another software completely, exactly for those ridiculous arc problems which don't show up in Allegro but show up in a gerber viewer. I find silkscreen to be generally useless anyhow, except for ass'y numbers and company names, there's no room on my boards anyways.

author: 8086
author_rank: Super Contributor
timestamp: March 07, 2015, 06:05:23 pm
content: Quote from: NANDBlog on March 07, 2015, 03:16:35 pm...because they did what they were asked to do? If your gerbers have silkscreen on pads,it's your fault.Assumptions lead to tears a lot of the time, if you don't want silkscreen on pads, don't put it on the goddamn pads!And in my view it isverybad form to make statements like the above when it's not their fault!

author: zapta
author_rank: Super Contributor
timestamp: March 07, 2015, 06:58:20 pm
content: Quote from: 8086 on March 07, 2015, 06:05:23 pmWhat do most good PCB houses do in this a case, ignore silently? call? clip?

author: JohnnyBerg
author_rank: Frequent Contributor
timestamp: March 07, 2015, 07:04:45 pm
content: Quote from: zapta on March 07, 2015, 06:58:20 pmMail! See reply #7

author: 8086
author_rank: Super Contributor
timestamp: March 07, 2015, 07:11:15 pm
content: Quote from: zapta on March 07, 2015, 06:58:20 pmI wouldn't know, I'm not silly enough to leave silkscreen on pads when I have PCBs manufactured.I expect any good manufacturer to make the PCBs according to the exact gerbers given, and if they are feeling particularly helpful, to query it. But I don't put the onus on them to make the query, since it's my job to design the PCB properly. It's only their job to make it.

author: wraper
author_rank: Unknown
timestamp: March 07, 2015, 07:20:05 pm
content: Good manufacturer will print silkscreen over soldermask layer only. Page 17 -http://www.eurocircuits.com/clientmedia/ecImage/pages/pcb-design-guidelines/eC-Design-Guidelines-ENGLISH-11-2014-V1.pdf

author: JuKu
author_rank: Frequent Contributor
timestamp: March 08, 2015, 10:24:37 am
content: Everyone made a mistake here: Eagle for not having a design rule check for this and have faulty libraries, you for sending out faulty data and the PCB factory for not noticing they are building unusable boards and asking for confirmation. Everyone is at fault, but imo, mostly Eagle.

author: Yansi
author_rank: Super Contributor
timestamp: March 08, 2015, 10:34:19 am
content: Or maybe the user of the eagle, if they do not know how to use or export silk layers correctly, huh?

author: Monkeh
author_rank: Super Contributor
timestamp: March 08, 2015, 10:38:39 am
content: Quote from: JuKu on March 08, 2015, 10:24:37 amEagle does have a design rule check for this.The tool is not to blame.

author: Psi
author_rank: Super Contributor
timestamp: March 08, 2015, 10:42:30 am
content: They should question something if unsure but never modify your files without confirming the change with you.

author: JuKu
author_rank: Frequent Contributor
timestamp: March 08, 2015, 01:37:33 pm
content: Quote from: Monkeh on March 08, 2015, 10:38:39 amThat was my point: It should have it.

author: Monkeh
author_rank: Super Contributor
timestamp: March 08, 2015, 01:51:43 pm
content: Quote from: JuKu on March 08, 2015, 01:37:33 pmIt does.

author: krish2487
author_rank: Frequent Contributor
timestamp: March 08, 2015, 02:25:09 pm
content: I had exactly the same problem with eagle and my fab company. It was anexpensivemistake.It happened during a production run. The baords were 2" x 4" 2 layer FR4, 6x2 panel, and2000 panels.Needless to say, my boss was not happy (to say the least). It was a wakeup call to pay attention to finer details.To answer your question, if it is a large batch, and if the fab is near your place and/or you can afford to send it to your fab and get it back,try to see if they agree to HASL finish the board again. That is what I did anyway. It did not fix all the pads but 99.9% of them were silkscreen free. It will nominally increase the solder coating on the boards, but not enough to cause any significant issues like pick and place alignment and reflow stuff.Needless to say, I threw out the stock libraries soon after and started a company repository of cad symbols that we use now.PS: I too agree with C4757p, it is not the fab fault. While many do the automatic deletion of silkscreen where pads are present, do not rely on it and get sloppy with stock libraries.

author: zapta
author_rank: Super Contributor
timestamp: March 08, 2015, 02:32:34 pm
content: Quote from: Monkeh on March 08, 2015, 01:51:43 pmOnly if the stop layer is displayed, right? I didn't get any DRC error.Anyway, I don't blame eagle. I assumed that clipping is part of the standard pcb manufacturing process.It would be nice though to be able to do the clipping when generating the gerbers.

author: Monkeh
author_rank: Super Contributor
timestamp: March 08, 2015, 02:34:21 pm
content: Quote from: zapta on March 08, 2015, 02:32:34 pmCorrect, Eagle only shows DRC violations on displayed layers.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 08, 2015, 03:10:40 pm
content: IME most PCB houses will punch out the silkscreen layer, typically using the resist layer, but always best not to allow the opportunity for errors by making sure your part defs avoid it.

author: zapta
author_rank: Super Contributor
timestamp: March 08, 2015, 03:54:56 pm
content: Quote from: mikeselectricstuff on March 08, 2015, 03:10:40 pmI fixed my footprints for future batches. Still waiting for an answer from Elecrow if this was a one time omission or is it their standard policy to ignore it silently.OSHPark does clip.

author: Ice-Tea
author_rank: Super Contributor
timestamp: March 08, 2015, 07:51:14 pm
content: All board houses that I have used (including some chinese ones) have clipped the silk but it's good to know this is not something to be taken for granted.To be honnest, even though they manufactured as described I would expect my boardhouse to give me a call when they plan to make something like that.

author: tszaboo
author_rank: Super Contributor
timestamp: March 08, 2015, 07:53:55 pm
content: Quote from: 8086 on March 07, 2015, 07:11:15 pmA good PCB house removes the silksceen from the pads. I know, because we oder from one and they explicitly say that they are going to do this, and I expect all manufacturers to do the same. There is no way you want silkscreen over a pad, even if you do you can jut mark it clearly that it should stay.The manufacturer's work is not blindly inputting your data into a machine, they need to process the data. This is clearly unacceptable. If we let them go stupider and stupider when making our orders, where does this stop? When they mill the legend into the PCB? Or when you find that they drilled through the fiducial you placed on the board, because it was placed on all layers for the alignment?

author: 8086
author_rank: Super Contributor
timestamp: March 08, 2015, 08:17:27 pm
content: Quote from: NANDBlog on March 08, 2015, 07:53:55 pmYou can expect whatever you like, it doesn't mean you'll get it. I don't think you have any reason to say that a PCB house that manufactured what you provide to them is a bad one. You make a mistake, and it's your own fault. Do you rely on someone else to wipe your bum, too? Why rely on someone else to fix your PCB design mistakes?They won't mill the legend into the PCB, because that layer won't be a milling layer, unless you provided it that way.They won't drill through the fiducial unless you have a drill hit in your gerbers in that location. Again, your fault.There's no reason for any PCB house to not simply manufacture what you provided, unless you know you are doing sloppy work and leave your own mistakes in the gerbers.My point is that it's extra nice when they point out your fuck-ups but you don't have the right to say they are a bad manufacturer just because they do as you told them. Well, you have the right, of course, but it wouldn't be fair to do so.

author: zapta
author_rank: Super Contributor
timestamp: March 08, 2015, 08:26:41 pm
content: Quote from: 8086 on March 08, 2015, 08:17:27 pmBecause they competitors will.

author: 8086
author_rank: Super Contributor
timestamp: March 08, 2015, 08:28:35 pm
content: Quote from: zapta on March 08, 2015, 08:26:41 pmWell sure, that's a good thing. People can choose their supplier. But really, it doesn't excuse someone passing blame for their own mistake onto an innocent party. That's my beef here.

author: zapta
author_rank: Super Contributor
timestamp: March 08, 2015, 08:33:37 pm
content: Quote from: 8086 on March 08, 2015, 08:28:35 pmUnless if the clipping is a common practice among PCB vendors. At some point it even requires an explicit 'we don't clip'.

author: 8086
author_rank: Super Contributor
timestamp: March 08, 2015, 08:36:39 pm
content: Quote from: zapta on March 08, 2015, 08:33:37 pmI disagree. You can expect whatever you like based on what others are doing, but ultimately, if your gerbers areflawed, it's your own fault if the manufactured boards are exactly what you asked for. I'm talking about the blame game, if your gerbers have silk on pads, nobody is to blame but yourself, no matter how commonplace clipping might be!

author: zapta
author_rank: Super Contributor
timestamp: March 08, 2015, 08:49:47 pm
content: I do not blame the PCB house, I don't even know if this was a one time omission or their standard practice (still waiting for their email answer).However I can use this information to guage their willingness to go the extra mile. Especially if this condition is very easy for them to detect and fix as others do andthe order takes more than 30 days to be delivered.No, I do not blame them in the 'legal' sense of the word or demand anything from them.

author: Ice-Tea
author_rank: Super Contributor
timestamp: March 08, 2015, 09:17:59 pm
content: It has nothing to do with blame. But I don't want to send my boards to a place that looks at the gerbers, sees silk over pads and goes "yeah, that looks about right".I don't drive like an idiot because I have ESP, ABS and whatnot but I don't want a car without 'em...

author: Siwastaja
author_rank: Super Contributor
timestamp: March 09, 2015, 01:29:25 am
content: As this thread can show, this is a lose-lose situation for the manufacturer. If they edit the files to fix common mistakes, people complain (at least in theory). If they don't, people complain.I have read several guides about submitting gerbers to PCB manufacturers, with common errors listed. Silk screen on pads is often listed. So you clearly didn't do your homework, and the assumption that fixing this error in manufacturing would be a very standard thing to do, is clearly wrong.So if the blame game is needed, I'd suggest blaming your PCB design software at least a little bit. Even if it was a "user error", clearly the software isn't easy enough to use as you have missed some DRCs or gerber generation options that are not even manufacturer-specific. Good software supports the natural design flow and make things easy - but in the EDA world, we are too accustomed to the flow of managing the software, instead of software helping us. This happens at the scale that we just forget that these tools should be helpful first. This can be seen on this forum, too: people mess up their PCB designs all the time and it's always "user error" and the CAD is always "just fine" "if you know how to use it".

author: zapta
author_rank: Super Contributor
timestamp: March 09, 2015, 05:34:20 am
content: I got a response from the vendor (elecrow). They normally do clip the silkscreen (good!) and this was a one time mistake. They offer to refund or remanufactured. My faith in the PCB industry is restored. ;-)I have another batch that is supposed to arrive tomorrow by DHL (different design), will see if it was clipped.

author: Falcon69
author_rank: Super Contributor
timestamp: March 09, 2015, 06:26:17 am
content: That was Nice of them Zapta. I've been tempted to use Elecrow for some time now. For reasons like this, I just may. Even though it wasn't technically their fault, they are still willing to reproduce at no fee for you. Very Nice of them. I may just have to use them for my next order, when that time comes.SIDE NOTE:I've been a cabinetmaker for over 20 years. I do electronics on the side, still a beginner.I've often been told buy people two things...1. A good cabinetmaker knows how to fix his mistakes so they can't be noticed.2. A good cabinetmaker never makes mistakes.I find that number one is a better option. The reason is because I believe you can actually learn more from your mistakes, then never making the mistakes.I have often made things BETTER from fixing my mistakes, then they would have been if I had NEVER made that mistake to begin with. The end product turned out better.In your case Zapta (as proven from another post I read here earlier of a PCB fab house screwing up), You may just end up with a better product (or extra of that product) then you would have gotten if they never made the mistake (or in this case, YOU made the mistake and they just went with it.).I have also had a bad experience with a Fab house (their mistake, not mine) that was also fixed for free. Sure, I had to wait extra days (or two weeks) for the product to be remade and sent, but they did it without charge. Their response was that they had a new hire and with the holiday so close, they were rushing to get things out and were not watching what the new hire was doing. I understand, things happen.Jason

author: krish2487
author_rank: Frequent Contributor
timestamp: March 09, 2015, 06:31:29 am
content: I tip my hat to you sir.Admitting to a mistake is the first step to doing a better job afterall.Quote from: Falcon69 onTodayat 05:26:17 PM

author: free_electron
author_rank: Super Contributor
timestamp: March 09, 2015, 12:13:16 pm
content: Silkscreen should normally be clipped during file intake as there is no reason for it to be on the pads.Silkscreen does not have the same electrical or mechanical properties like soldermask so it can't even be used as an electrical strengthener.That being said : if you use so called no-touch services , where files are processed without human intervention then stuff like this may not automatically happen.A decent pcb fab will carch this and email you if they should clip.That being said : it is very bad form to have silkscreen over pads in parts libraries. People that design such footprints should be slowly roasted and their remains sent through a coffee grinder ...

author: rs20
author_rank: Super Contributor
timestamp: March 09, 2015, 12:29:34 pm
content: Quote from: free_electron on March 09, 2015, 12:13:16 pmYou're assuming here that any exposed copper is a pad (obviously the OPs case, the silkscreen was on a pad, but now you're talking about automatically clipping all silkscreen from all exposed copper). What if I want to have only tiny slivers of solder mask to keep my solder on the pads, and have most of my copper bare for, oh I dunno, heatsinking or aesthetic purposes or something? In that case, it would make perfect sense to have the silkscreen on the bare coppernextto my pads. Sure it's a contrived example, but I'm in favour of the manufacturer making exactly what you send them for this sort of reason.QuoteI concur!QuoteI concur!

author: free_electron
author_rank: Super Contributor
timestamp: March 10, 2015, 01:58:28 am
content: Quote from: rs20 on March 09, 2015, 12:29:34 pmi'm not assuming anything. The gerber processor can detect what is a pad and what is not a pad. ( pads are defined as flashes in gerber , so you can detect them )Then there is also the problem that silkscreen ink sticks very well to soldermask but not very well to copper ( the formulation is different ).

author: zapta
author_rank: Super Contributor
timestamp: March 10, 2015, 02:07:13 am
content: The second batch arrived today and is clipped properly. The non clipping was a one time fluke. Life is good.

author: itdontgo
author_rank: Regular Contributor
timestamp: March 10, 2015, 09:28:14 am
content: I hate manufacturers touching my Gerber files. They should make it just as you send it whether they think it's right or wrong. End of discussion.

author: ruffy91
author_rank: Regular Contributor
timestamp: March 10, 2015, 10:16:40 am
content: Most manufacturers will Clip it to their rules because their rules say to not print silkscreen over exposed copper. If their design rules allow it they naturally won't clip it. And if their rules say no silkscreen over copper and they manufacture it with silkscreen over copper their preprocessing has failed. They should inform you about rule validations. They could even harm their machines when trying to manufacture something that doesn't conform to their rules (example: hole to hole clearance)

author: tszaboo
author_rank: Super Contributor
timestamp: March 10, 2015, 03:29:23 pm
content: Usually you get an assignment to design a board in T time, using the library your company created with work of years and years, by people who no longer work there and other people who dont give a toss about their work.You have three options when the library is that screwed up.1. You make the board in time, send it to the manufacturer who clips it, they do this, soldering the board is possible. Everyone is happy.2. You start correcting the library, praying that you didnt accidentally screwed up something and you dont finish the board in time.3. You start correcting the library in overtime, in your own free time, between projects, in lunchtime...Seriously, who needs it. This is not even close to the biggest issues we have during PCB design. I just love when I'm ready with the layout and there is 100+ DRC issues with silk to silk clearance and silkscreen over component pads. Gess what? I'm not going to worry about those problems, which will be corrected anyway by someone else during the order and spend my precious time doing this. The same way, I expect the manufacturers to do this for me.