Graham: The peelable vinyl's are very stable after application and cure prior to soldering. Six months+ should not be a problem. The water soluble masks are a different story. The are hygroscopic by nature. If they are not properly stored the coating will begin to breakdown, soften and stick to adjacent surfaces. We normally don't hold water soluble boards longer than a month. However by using special slip sheets, packing and storage conditions we have held them up to a year, but I wouldn't recommend it for normal production. Regards Mike B. Fluke Corp. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Graham Collins Sent: Thursday, January 04, 2007 9:49 AM To: [log in to unmask] Subject: Re: [TN] (2)Temporary peelable solder masks Hi Mike! Thanks for the detail. Interesting. What sort of shelf life would you expect on a bare board with a vinyl mask on it? regards, Graham Collins Process Engineer, L-3 Communications Electronic Systems Inc. Halifax (902) 873-2000 ext 6215 >>> "Barmuta, Michael" <[log in to unmask]> 01/04/07 11:41AM >>> Graham: As an OEM that has built both bare boards and PCA's and used temporary soldermask resist (TSR) for 30+ years, let me address a couple of your questions. * Bare board fabricators do apply peelable TSR, however there is not a large demand for it. So finding a shop that offers it may be a little difficult. There are two main types of peelable TSR, latex based and vinyl based. Typically the fabricators apply the vinyl style. It is applied to the board with a squeegee by printing thru a screen imaged with the features open to where the mask is desired then baked to cure. It works well if applied correctly, cured correctly and the printed feature has the right design/shape. If done improperly it is a mess. Hard to remove, breaking into small pieces, very labor intensive for removal. * If using a water soluble TSR use an unfilled version. Some TSR manufacturers add fillers such as talc or silica to there products to enhance the printing or rheology characteristics. Unfortunately as you found out it tends to clog filters, wear nozzles/pumps, settle in low spots, etc. Unfilled TSR's do not have this problem there are 100% soluble. As I said above we have used TSR for 30+ years in our aqueous wash system and not had any problems with the equipment. Regards Michael Barmuta Staff Engineer Fluke Corp. Everett WA 425-446-6076 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Graham Collins Sent: Thursday, January 04, 2007 6:57 AM To: [log in to unmask] Subject: Re: [TN] Temporary peelable solder masks Similar to Steve, our military stuff always gets cleaned. But I did build some class 3 stuff with no-clean - mainframe equipment (commercial) - with a previous employer. Your bank wants class 3 product and very high reliability, but at least you can count on them to not use a hose to clean it off, and they keep the office air-conditioned. Given that at this employer we do contract manufacturing, the likelihood of convincing all customers to agree to no-clean flux is fairly slim and so it's difficult to justify looking at the qualification work. We also have the issue of supporting build over many years, which often forces buying "end of life" batches of parts - which become more difficult to solder over time, so a fairly active flux is required. If I'm understanding Nigel's question properly, I'd never heard of a PWB manufacturer pre-applying peelable solder mask - it's not something I've ever come across as an option. Does it work well? How does the PWB manufacturer apply it? We use the DIY version, we apply it just before wave soldering. We currently use the peelable stuff, we had used the water soluble but with some production volume increases we were finding it clogged up the filters in the cleaners too quickly. regards, Graham Collins Process Engineer, L-3 Communications Electronic Systems Inc. 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