Solder Mask Delamination? - Page 1
Forum section: electronics / projects

author: hipmusicman
author_rank: Newbie
timestamp: June 03, 2020, 08:00:39 pm
content: Not sure if this is the right place for this but here it goes.We received some boards from the board-house with some various issues. One of which is possible delamination of the solder mask. Or at least that's what we think it is. I don't know what the IPC standard is for something like this partly because I'm not sure what it is and if it's bad or not. Our customer (whom this board will go to), is pretty picky about how their boards turn out. The simple thing we could do is just ask them if it's ok their boards have this but perhaps they don't know what it is and we would look pretty foolish if we asked them about it clueless ourselves. We are already in contact with the board-house on this matter.Beyond making ourselves look foolish as it is not knowing what this is, I turn to the community.-UPDATE: I've posted this a few other places and since then it has been brought to my attention the issue could be as follows: "The splotches are either from the artwork coming into contact with the tack-cured mask, or the mask is following the underlying copper surface."Any thoughts on this as well?

author: wraper
author_rank: Unknown
timestamp: June 03, 2020, 08:04:39 pm
content: It's simply rough surface IMHO.

author: ogden
author_rank: Super Contributor
timestamp: June 03, 2020, 08:48:39 pm
content: Quote from: wraper on June 03, 2020, 08:04:39 pm^^^^ this. No way it is "delamination" of the mask, most likely just screen printing artefact. In case your customer is complaining, you may remind that IPC does not require solder mask surface to be glossy, matte or whatever. IPC-SM-840D, 3.3.1 says that solder mask shall be uniform in appearance, without anomalies that would interfere with assembly or operation of the board.

author: hipmusicman
author_rank: Newbie
timestamp: June 03, 2020, 09:52:46 pm
content: That is an interesting point. However, the reason white solder mask is used is because the customer is using it as light diffusion. That being the case, if the light isn't being diffused properly, they could have the argument it doesn't perform as intended. IPC doesn't specifically state anything about the surface texture. HOWEVER, IPC be a guideline and not and outright rule, it is therefore up to the customer to decide how they want a board made. That being said, if was was never specified in detail how it should be made based on its intended use, then the argument is void.This isn't to cause tension in any way, but it does raise some useful questions and promotes better communication.Thank you guys so much for your help with this matter!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 03, 2020, 10:52:37 pm
content: If it needs a spec like "even diffusion of light", put it on the fab sheet!As for delamination, is it actually weak? Try scraping at it on your prototype? (You keep one prototype for lab use, right?)It just looks uneven to me, and a printing artifact is plausible.If it needs something that the fab can't provide (they may complain that they cannot provide compliance with such, relatively abstract, criteria), have you considered getting an overlay, sticker, paint, etc. to cover the area instead? It will add to the cost or assembly of course, because, well, of course it does, it's something additional that a PCB doesn't normally provide. Notify the customer and make sure they are okay with the change.Tim

author: bitter_mike
author_rank: Contributor
timestamp: June 03, 2020, 11:29:01 pm
content: No properly plated or laminated copper surface is that rough, so it is definitely not that.Depending on how the soldermask was applied here (screen printed or rolled on and exposed) it could be any number of defects. Having accidentally touched a not-fully-cured film once or twice, I like that explanation.Besides this question of its behavior with light, which is specific to your application and which I can't really speak to, the only thing I would be concerned about is adhesion. A good quick test is to apply some tape (scotch tape is fine), press it firmly down with your fingers so it makes good contact, and then quickly rip it off and see if you get any soldermask up with it. This, and variants of it, are actually ASTM tests where the tape is specified and so on. If there's nothing wrong with the adhesion, it's non-destructive.

author: hipmusicman
author_rank: Newbie
timestamp: June 04, 2020, 11:41:03 am
content: As a facility that does A LOT of prototyping (at least on our end aka first time through OUR machines), you would think we get prototypes of stuff. Seems odd that we don't but that's a whole other matter.We are getting 3 boards replaced due to a separate issue so I could try the tape trick out on one of those. I could even test via scratching. Scratching anything is usually my very last resort. Seems a lot of people around here (in my facility) like to pick at stuff that doesn't look normal and a lot of times it ends up causing more problems. But of course, these instances were on boards we intended to send to the customer. Again, a whole other matter.Thank you for the suggestions.

author: hipmusicman
author_rank: Newbie
timestamp: June 04, 2020, 02:23:19 pm
content: Just tried using tape and scraping and nothing is coming off so we should be all good!THANK YOU!!!