I had very good succes running ImAg. Shelf life was good and often was able
to solder 3 months after soldering 1st side. Some of the lots would get
waylayed. The vast majority ran though complete production in less than a
week.  Typical was double sided reflow, wave or saelective solder. All no
clean using low VOC flux. I would not have had the same success if I had to
wash them 2 or 3 times. Process used in automitive on infotainment, ABS and
safety sensors. WIP life was more of an issue with ImSn and had poor
results with low VOC flux, which resulted in running an alcholo based flux.
The factory was in rural MO. The air quality was very good in the area.

I do not know how ImAg would run in a polluted enviorment. Noticed trouble
running ImAg in a brand new factory in a Mexican industrial park. Never
resolved wether it was the new sheet rock or the the chicken farm down the
road.

The HIC's have been removed from most commerical production PCB's. Saved a
dime on a package. Ok for repetative current production. The requirment for
long shelf life due to supporting the product after production stopped was
poorly addressed. It is typically 8 years.

WI/MN has a fine bake out procedure this time of year. Just leave them open
on the shelf. Rh under 5% if no humidy added to shop and temp well below
zero. Nothing like watching the sparks fly pulling off the gloves with real
fur linings on a cold crisp day.




On Wed, Dec 11, 2013 at 9:28 AM, Whittaker, Dewey (EHCOE) <
[log in to unmask]> wrote:

> I (out of this world class; The PB, Class 3, 3/A Aerospace) do not allow
> any Lead-free Tin finishes and will never allow ImSn. Fresh raspberry
> croissants at the local Starbucks have a longer shelf life than ImSn. IMHO,
> if you must use them, keep them in the approved packaging (bags, etc.)with
> the HIC still showing acceptable and a CoC that they were dry (at or below
> the allowable percentage level of moisture) and solderable at time of
> delivery and stored in a controlled (monitored) atmosphere, until time of
> use. When they are pulled for use (out of package),  they should be held in
> a nitrogen environment until paste and reflow and or after paste and place
> if reflow is not immediate. A general rule is a 72 hour window prior to
> final reflow assembly. Any other handling/baking is like playing
> Wisconsin/Minnesota roulette (all the chambers are full, they don't want
> any loose lead rounds falling into the ice holes and endangering the fish).
> Dewey
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
> Sent: Wednesday, December 11, 2013 7:50 AM
> To: [log in to unmask]
> Subject: Re: [TN] Moisture Level Determination of PCB
>
> But you do not need to bake tin-finished CCAs, IPC-1601 also includes
> information on how to desiccate them at room temperature. While it may take
> a week or two, you can still ensure the board is sufficiently dry such that
> it can withstand normal leaded and lead-free mass reflow and wave solder
> processes without loss of solderability, delamination, CAF formation, and
> other moisture-related issues. That is the point I am trying to get across.
> And I consider both you and Grunde to be top-tier engineers.
>
> -----Original Message-----
> From: Steve Gregory [mailto:[log in to unmask]]
> Sent: Wednesday, December 11, 2013 8:00 AM
> To: [log in to unmask]; Stadem, Richard D.
> Subject: RE: [TN] Moisture Level Determination of PCB
>
> Hi Richard,
>
> I guess I'm not top-tier because I've never had any luck with tin finished
> boards. It's turned into a huge disaster every time I've baked them. So I
> just don't anymore...
>
> Steve
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
> Sent: Wednesday, December 11, 2013 6:32 AM
> To: [log in to unmask]
> Subject: Re: [TN] Moisture Level Determination of PCB
>
> If the guidelines within IPC-1601 are followed, there should be no grief,
> not even for PWB finishes other than ENIG and HASL.
> A top-tier process engineer understands how to set up the optimum baking
> time and temperature schedule for any given PWB size and type, such that
> you can remove at least 80% of the saturated moisture content by weight
> with no compromise to the PWB solderability, for any PWB, for any finish.
>
> Just because the boards are stored in sealed bags means very little.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Grunde Gjertsen
> Sent: Tuesday, December 10, 2013 5:23 PM
> To: [log in to unmask]
> Subject: Re: [TN] Moisture Level Determination of PCB
>
> Hi
>
> Without being too scientific about it.
>
> 1. For FR4 it is generally not that critical if storage and shop floor
> conditions is reasonably controlled and the boards are stored in sealed
> bags. J-STD-033 is not really relevant but if you can handle the logistics
> comfortably it seems like a good idea to me.
> Be very careful about baking out anything other than HASL and ENIG, all
> sorts of grief can follow.
> If what worries you are delamination and leadfree soldering the key is to
> choose a laminate that is suitable for the design, process and to some
> extent end user application. (Class 3) Anything polyimide/flex take much
> more care and bake out prior to soldering and for each thermal event
> according to manufacturers recommendations unless you can store the boards
> in a dry cabinet between. Do not trust the boards to be dry enough from the
> manufacturer.
>
> 2. Yes.
>
> Best regards
> Grunde
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of MaryJane Chism
> Sent: 10.desember 2013 18:32
> To: [log in to unmask]
> Subject: [TN] Moisture Level Determination of PCB
>
> Hi Group,
>
> I have a question concerning the moisture level of a printed circuit board.
>
> 1) Does a printed circuit board have an MSL level? We have been treating
> the printed circuit as an MSL Level 3.
> 2) Should we consider the wave solder as a thermal event even though the
> wave carriers shield all areas of the printed circuit board except the
> specific through hole areas. We currently do but should we?
>
> Any information you give will be helpful,
>
> Thanks,
>
> Mary Jane
>
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