You knew it was going to happen in dew time.
Dewey
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: Wednesday, May 19, 2010 11:12 AM
To: [log in to unmask]
Subject: Re: [TN] My first RoHS circuit board!
I sense an unhealthy trend of the forum accessing my squirreled away
assets.
Doug Pauls
"Whittaker, Dewey (EHCOE)" <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
05/19/2010 12:14 PM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
"Whittaker, Dewey (EHCOE)" <[log in to unmask]>
To
[log in to unmask]
cc
Subject
Re: [TN] My first RoHS circuit board!
Good question: better answer; it depends (one more donation to DPMSF¹).
Back in the days when close still counted, a 72 hour window was a
reasonable target when using an IPC-4101/24 material with a higher rated
Tg. Baking, if you were lucky, was something your wife did.
There is a group of people working on this in the IPC-1601 meetings. Don't
trust HICs and the stated % of moisture. Question the methodology of
measurement, because the quality of your product hangs in the balance (I
couldn't resist or even mask the attempt).
In lieu of the above, one could always request or verify the coupons were
prepared and packaged the same as the PB (cleaned, baked, properly
packaged, stored together). Take some samples of the coupons and acclimate
in your factory environment for 12, 24, 36, 48, 72 hours etc. Precondition
them per IPC-TM-650, Method 2.6.27 (6 X 260ºC) and inspect to the Class 3
acceptability requirements of IPC-6012C. If all of them pass up to 72
hours, it would be reasonable, but not guarantied, to assume the PBs would
also be good. However, if the coupons failed, then the PBs should be baked
prior to production use.
Dewey
Note 1: Doug Pauls Memorial Slush Fund
________________________________
From: Jack Olson [mailto:[log in to unmask]]
Sent: Tuesday, May 18, 2010 8:16 PM
To: Whittaker, Dewey (EHCOE)
Cc: TechNet E-Mail Forum
Subject: Re: [TN] My first RoHS circuit board!
Yes, two lead-free profiles plus selective solder for some through-hole
comps,
but expected to survive over twenty years in fairly harsh conditions, lots
of
thermal cycling (-45C+125C)
thanks for soothing my nerves...
by the way, our boards are shipped in sealed packages with humidity
indicators,
but then could be open on the floor for up to a day before being soldered.
Is one
day enough time to re-absorb enough moisture to cause a problem with /126?
thanks again,
Jack
On Tue, May 18, 2010 at 4:41 PM, Whittaker, Dewey (EHCOE)
<[log in to unmask]> wrote:
Jack,
Just designing for RoHS compliance does not dictate the use of non-dicey
cured material. If you are designing a fully compliant, complex,
Lead-free design that will be exposed to a minimum of two lead-free
reflow profiles and one wave solder operation and expect it to work for
twenty plus years, then no dicey-cured FR4 shall apply. IPC-4101/126 and
/129 are phenolic cured materials which have demonstrated a robustness
that is up to the challenge.
Dewey
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Jack Olson
Sent: Tuesday, May 18, 2010 2:29 PM
To: [log in to unmask]
Subject: [TN] My first RoHS circuit board!
Well, we avoided it as long as we could, but now I have to design for
RoHS
compliance.
I'm basically following Werner's recommendations (which don't conflict
with
anyone else's as far as I know), but I'm confused about one aspect of
material:
Several sources have stated that its better to use "NON-DICEY" material,
but
none of the IPC-4101 slash sheets mention dicy or non-dicy (or
dicyandiamide).
If we are trying /126 material, do we still have to specify non-dicy?
thanks,
Jack
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