Jim If any vendor delivered me circuits like those and then said they were acceptable, I would blacklist him illico prestissimo. Brian Jim Gilbert wrote: > Pete, > > I agree with your evaluation 100%. I also believe this is a debubbling > issue because I've seen it many times first hand. Some inks are more apt > to bubble than others. To resolve the issue with bubbles, hold times prior > to tack bake are a standard in the fabrication business (for those of us > who apply the ink with a screen). If hold times are creating production > problems then I suggest looking at other inks. Some inks will debubble > fast enough that virtually no hold time is required. > > Outside of the aesthetics, if the soldermask isn't voided then these boards > are still acceptable. > > Jim Gilbert > > -----Original Message----- > From: Peter Menuez [SMTP:[log in to unmask]] > Sent: Thursday, July 27, 2000 7:48 PM > To: [log in to unmask] > Subject: Re: [TN] "Bubbly Soldermask..." > > First of all the pictures you show look pretty bad and > I don't believe I would ever ship something like > these. However, I want to point out that these may not > be 'rejectable'. > > After coating LPI there is a hold time to allow the > mask to debubble. This debubble time varies on many > things but primarily on the thickness of the copper > trace. > > Think about the geometry of the trace. If the trace > was 1oz (.0014") the mask would cover fairly evenly > and there would be little or no mask build up at the > trace. At the trace thickness increases the trace > acts as a dam forcing the mask to build up along the > trace. This is exactly what you are showing in the > pictures. The fact that the mask is very thin (most > pigment removed) at the top of the trace is a good > indicator that there is high copper here.) > > The debubbling hold time is designed to allow the > volatiles (solvents) to escape the mask. What it > looks like in your picture is that the boards were not > debubbled long enough before they were tack cured. > What you have left are small dots where the solvent > was forced out of the mask leaving behind a puddle of > mask. > I have done a considerable amount of cross sectioning > on this anomaly and have yet to find a void in the > mask. > > I glanced over several of the emails responding to > your original question and suggest that > contamination, curing, moisture etc. are based on > peoples inexperience with LPI's. This is a classic > debubbling issue. > > I said in my opening statement that these boards may > not be rejectable. They are rejectable for the simple > reason that they are ugly but probably not rejectable > for performance issues. If you cross section these > puddles you will see that there is more mask present > (rather than less which would be the case with a > void). If you have more mask you have more insulation > and in fact your insulation performance would be > increased. Ok, this is pretty weak but... > > The area I would concentrated on with your supplier > are: a) control of the plating process and > b) if there is anything you could do to help them > control the plating (robber buss/thief area) > > pete menuez > [log in to unmask] > > --- Brian Ellis <[log in to unmask]> wrote: > > Steve > > > > This is incredible. Change your supplier as top > > priority :-) Seriously, as the others > > say, the "bubbles" are probably due to solvent/water > > entrapment in the track corners. > > However, I see another problem which may/may not be > > related. Am I correct in thinking > > that it has been hot and humid where you are, > > lately? If so, it would seem that there > > has been hygroscopic contamination left on the > > board. On your first photo, see the > > myriad white points between the tracks? This looks > > like vesication to me. The most > > common cause is hygroscopic contamination (ionic or > > non-ionic) which pumps atmospheric > > humidty across the mask layer (all polymers can > > allow humidity through). The osmotic > > pressure rises until it actually lifts the mask off > > the surface, locally, forming a > > vesicle or, if you like, a microblister (see my book > > for detailed explanation). This > > could possibly be the cause of your bubbles along > > the track edges, as well, although > > these seem rather gross: the photo I use to > > illustrate vesication also has bubbles > > along some of the track edges, but the vesication > > between the tracks is on a similar > > scale. Whatever, it is a totally unacceptable fault. > > > > Brian > > > > "Stephen R. Gregory" wrote: > > > > > Hi all! > > > > > > We just got some boards in at receiving inspection > > that have thousands of > > > little "bubbles" in the soldermask all over the > > boards...they seem to > > > concentrate all along the edges of the features of > > the board. You can see > > > pictures of it at: > > > > > > > > > http://www.driveway.com/share?sid=e25a88c4.8e904&name=Pictures > > > > > > One picture is bubblemask.jpg, the other is > > bubblemask2.jpg...what would > > > cause that? It's a LPI...don't know the brand > > name. I'm thinking that either > > > the boards weren't dry or cleaned well prior to > > soldermasking them. I'm > > > rejecting the boards of course... > > > > > > My freedrive is filling up fast with all the > > pictures of the "pretty boards" > > > that we get from our vendors!!! > > > > > > -Steve Gregory- > > > > > > > > > ############################################################## > > > TechNet Mail List provided as a free service by > > IPC using LISTSERV 1.8c > > > > > > ############################################################## > > > To subscribe/unsubscribe, send a message to > > [log in to unmask] with following text in > > > the body: > > > To subscribe: SUBSCRIBE TECHNET <your full name> > > > To unsubscribe: SIGNOFF TECHNET > > > > > > ############################################################## > > > Please visit IPC web site > > (http://www.ipc.org/html/forum.htm) for additional > > > information. > > > If you need assistance - contact Keach Sasamori at > > [log in to unmask] or > > > 847-509-9700 ext.5315 > > > > > > ############################################################## > > > > > ############################################################## > > TechNet Mail List provided as a free service by IPC > > using LISTSERV 1.8c > > > ############################################################## > > To subscribe/unsubscribe, send a message to > > [log in to unmask] with following text in > > the body: > > To subscribe: SUBSCRIBE TECHNET <your full name> > > To unsubscribe: SIGNOFF TECHNET > > > ############################################################## > > Please visit IPC web site > > (http://www.ipc.org/html/forum.htm) for additional > > information. > > If you need assistance - contact Keach Sasamori at > > [log in to unmask] or > > 847-509-9700 ext.5315 > > > ############################################################## > > __________________________________________________ > Do You Yahoo!? > Kick off your party with Yahoo! 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