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Subject:
From:
Larry Dzaugis <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Larry Dzaugis <[log in to unmask]>
Date:
Thu, 12 Dec 2013 16:40:20 -0600
Content-Type:
text/plain
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text/plain (151 lines)
Lutefisk, dried cod cured in lye.


On Thu, Dec 12, 2013 at 2:29 PM, Stadem, Richard D. <
[log in to unmask]> wrote:

> What fish?
>
> -----Original Message-----
> From: Whittaker, Dewey (EHCOE) [mailto:[log in to unmask]]
> Sent: Wednesday, December 11, 2013 9:29 AM
> To: TechNet E-Mail Forum; Stadem, Richard D.
> Subject: RE: [TN] Moisture Level Determination of PCB
>
> 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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