Obviously you're approaching the weak end of the spectrum.
Dewey
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
Sent: Thursday, September 10, 2009 11:32 AM
To: [log in to unmask]
Subject: Re: [TN] Need clever comments
Hmmm.....I needed CLEVER answers....he-he
and instead I get advice what gun to use to kill a little woman,
Freud would have a hard job to analyse these associations.
Guess he would give up and make this summary : ' Friday must be close'..
/Inge
----- Original Message -----
From: "Dwight Mattix" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, September 10, 2009 8:06 PM
Subject: Re: [TN] Need clever comments
> At 10:26 AM 9/10/2009, Randall L Bock wrote:
>>OH YEA... a nice run down a line of about 300 ship mates and a kiss on
the
>>Kings Ring will take care of the smell.
>
> Don't miss the Royal Baby or the maraschino cherry (I hope that's what
it
> was) in the Kings navel.
>
>
>>-----Original Message-----
>>From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
>>Sent: Thursday, September 10, 2009 12:59 PM
>>To: [log in to unmask]
>>Subject: Re: [TN] Need clever comments
>>
>>Comes from eating too many Krabby Patties! Send them back to
Failuretown
>>where they belong.
>>
>>-----Original Message-----
>>From: TechNet [mailto:[log in to unmask]] On Behalf Of Dwight Mattix
>>Sent: Thursday, September 10, 2009 11:04 AM
>>To: [log in to unmask]
>>Subject: Re: [TN] Need clever comments
>>
>>At 08:40 AM 9/10/2009, Inge wrote:
>> >Good idea, but presupposes that someone is not brainier than a
>>polliwog.Can
>> >that be?
>>
>>Only remedy for Pollywogs is a trip before King Neptunes court.
>>
>>We Shellbacks can tell when we are in the company of polliwogs. It's
>>apparent by the foul stench they emit.
>>
>>
>>
>> >/Inge
>> >
>> >----- Original Message -----
>> >From: "Steven Creswick" <[log in to unmask]>
>> >To: <[log in to unmask]>
>> >Sent: Thursday, September 10, 2009 5:21 PM
>> >Subject: Re: [TN] Need clever comments
>> >
>> >
>> > > Inge,
>> > >
>> > > Could the copper 'contamination' have been a transfer of copper
>>caused by
>> > > someone placing a non-masked board, with exposed copper, in
contact
>>with
>> > > the
>> > > surface of your board's solder mask?
>> > >
>> > > Maybe during shipment, etc.?
>> > >
>> > > Steve C
>> > >
>> > > -----Original Message-----
>> > > From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
>> > > Sent: Thursday, September 10, 2009 11:11 AM
>> > > To: [log in to unmask]
>> > > Subject: Re: [TN] Need clever comments
>> > >
>> > > Jack &Paul, FYI.
>> > >
>> > > Today I had a close look at the cross sections. What I found was
>>this:
>> > >
>> > > 1. The Tin plating was done AFTER solder mask (Jack was right)
>> > > 2. The solder mask was very uneven, thickness between 5um and 25
um.
>> > > 3. Despite the corrupted surface, the solder mask is homogenous,
no
>> > > vertical
>> > >
>> > > cracks found.
>> > > 4. The copper that I found earlier on top of the conductor, i.e.
on
>>the
>> > > solder mask, that copper had no connection with the conductor
>>copper.
>> > > Which
>> > >
>> > > means that these contaminations had NOT migrated through the
solder
>>mask.
>> > > 5. I can still not figure out from where the copper
contaminations
>>come.
>> > >
>> > > So, all that remains is the question about the copper
contaminations
>>tha
>> > > embedded in the very surface of the solder mask. I have to adjust
my
>> > > report
>> > > and resend it to our customer and the board maker.
>> > >
>> > > Thanks to your critisism, I can now redo the analys, starting
from
>>a more
>> > > correct standpoint.
>> > >
>> > > Your are great!
>> > >
>> > > /Inge
>> > >
>> > >
>> > >
>> > >
>> > > ----- Original Message -----
>> > > From: "Inge" <[log in to unmask]>
>> > > To: <[log in to unmask]>
>> > > Sent: Wednesday, September 09, 2009 8:09 PM
>> > > Subject: Re: [TN] Need clever comments
>> > >
>> > >
>> > >> Jack,
>> > >>
>> > >> SMOBC is the common industrial standard, as you pointed out,
>>however,
>> > >> there ARE some fabricators that apply the solder mask after
>>Tin/Lead-ing
>> > >> the copper traces. The later method has an obvioius
disadvantage,
>>see
>> > >> below quoted from an article written by US Environmental Agency:
>> > >>
>> > >> " This method predominates for several reasons. Copper is a
>>surface that
>> > >> lends itself to rigorous cleaning, which is essential for solder
>>mask
>> > >> adhesion. Tin-lead under solder mask will liquefy during
soldering
>>and
>> > >> may
>> > >
>> > >> cause the mask to blister and peel. The hot air solder leveling
>>process
>> > >> generally produces less waste water and introduces less lead
into
>>the
>> > >> waste water stream than tin-lead plating and reflow. Despite
these
>> > >> advantages, well-known disadvantages also exist. The shelf-life
of
>>hot
>> > >> air
>> > >
>> > >> solder leveled circuits is short and solder thicknesses on pads
and
>>hole
>> > >> barrels is notoriously difficult to control. For these reasons,
a
>>small
>> > >> minority of specifications continue to call for tin-lead plate
and
>>reflow
>> > >> or other alternati air solder leveling, nomenclature screening,
and
>> > >> finally, gold edge plating if necessary. "
>> > >>
>> > >> I think that is what happened to our boards....." cause the mask
to
>> > >> blister and peel"...
>> > >>
>> > >> Another paper describes Tin under solder mask this way:
>> > >>
>> > >> " Facility F initially was concerned with the soldermask
breakdown
>>where
>> > >> the Tin leaches underneath the soldermask....etc"
>> > >>
>> > >> Quoted from EPA (United States Environmental Protection Agency.
>> > >>
>> > >> When I started the investigation (had just some hours to spend
>>before
>> > >> reporting the result!), I was fully convinced that these boards
>>were
>> > >> SMOBC, but our customer said they used tinning before
soldermask. I
>>have
>> > >> asked for a confirmation from the board fabricator, but got no
>>answer.
>> > >>
>> > >> Thanks for your comment, good critics.
>> > >>
>> > >> Inge
>> > >>
>> > >>
>> > >> ----- Original Message -----
>> > >> From: "Jack Olson" <[log in to unmask]>
>> > >> To: <[log in to unmask]>
>> > >> Sent: Wednesday, September 09, 2009 4:44 PM
>> > >> Subject: [TN] Need clever comments
>> > >>
>> > >>
>> > >>>I know I'm late to the game, but I can't resist asking this
>>question:
>> > >>>
>> > >>>>From my experience, the tin is applied AFTER soldermask, so
>> > >>> you have mask over bare copper, and tin over exposed copper.
>> > >>>
>> > >>> The tin in PHOTO2.JPG in the exposed area looks beautiful,
>> > >>> so isn't the question (ignoring the whiskers for the moment)
>> > >>> "How can bare copper erupt through the mask?"
>> > >>>
>> > >>> Unless I missed one of your previous posts, it seems to me that
>> > >>> any speculation about copper poking through the tin finish is
>> > >>> irrelevant. I'm only addressing Question 2 below, but you
>>mentioned
>> > >>> introducing a nickel barrier, and that will not be plated under
>>the mask
>> > >>> either, will it? only on exposed circuitry...
>> > >>>
>> > >>> just wondering,
>> > >>> Jack
>> > >>>
>> > >>>
>> > >>> -=-=-=-
>> > >>>
>> > >>> *Subject:* Need clever comments *From:* Hernefjord Ingemar <
>> > >>> [log in to unmask]> *Reply-To:* TechNet E-Mail
Forum
>><
>> > >>> [log in to unmask]>, Hernefjord Ingemar
>><[log in to unmask]>
>> > >>> *
>> > >>> Date:* Mon, 7 Sep 2009 13:21:54 +0200 *Content-Type:*
text/plain
>> > >>>
>> > >>>
>> > >>> Hi all, need some professional backup regarding MIL quality
>>boards.
>> > >>>
>> > >>> Objects: FR-4 Class III double-sided multi-layer boards,
populated
>> > >>> with SOICS, BGAs,and a lot of passive components.
>> > >>>
>> > >>> Observation 1 : the non soldered board have lots of Tin
whiskers
>>on
>> > >>> inside of the PTH barrel. My thought is this: if whiskers can
grow
>> > >>> long before the board is assembled, then ain't it likely that
even
>>CAF
>> > >>> can be generated? See photo 1.
>> > >>>
>> > >>> Observation 2: Copper has somehow penetrated the solder mask.
>>This
>> > >>> can be found everywhere along the conductor traces. You need a
>>very
>> > >>> good light microscope and a SEM to see it. See photo 2.
>> > >>>
>> > >>> Board data: Copper with 0.8 micrometer Immersion Tin. No nickel
>> > >>> barrier. Solder mask thickness not specified.
>> > >>>
>> > >>> Application: Typical MIL-883 environment
>> > >>>
>> > >>> Q1: What is your opinion about that thin Tin directly on
copper? I
>> > >>> dislike the concept. Copper is very mobile at high
temperatures,
>>and
>> > >>> combined with humidity, there can be leakage currents and
>>corrosion
>> > >>> issues. Even if the boards are CCd, there is a risk with copper
.
>> > >>>
>> > >>> Q2: I gave the advice to introduce a nickel barrier, but our
>>customer
>> > >>> claimed, that they can't because of pressfit connectors and
>>pressfit
>> > >>> test pins on the board. Furthermore, they had heard that one
>>cannot
>> > >>> have nickel platings when pressfitting, because the nickel will
>>crack
>> > >>> and oxidize and cause electrical disfunction. Is this your
opinion
>> > >>> too? Are there any relevant testing behind such statements?
>> > >>>
>> > >>> Thanks in advance
>> > >>>
>> > >>> Inge
>> > >>>
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