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TechNet E-Mail Forum <[log in to unmask]>, Inge <[log in to unmask]>
Date:
Thu, 10 Sep 2009 22:10:38 +0200
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bet you used TIB0203 100k logics those days, and less than 500 MHz
Inge

----- Original Message ----- 
From: "Stadem, Richard D." <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, September 10, 2009 9:46 PM
Subject: Re: [TN] Need clever comments


Funny you guys should mention that. When I started out as a digital
troubleshooting tech at Honeywell in 1978, I worked in Underseas Systems
on the Mod 2, Mk-46 Neartip, and Mk-50 Advanced Lightweight Torpedo
guidance and control systems. I did that for 10 years. Brings back a lot
of memories, so to speak.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Jerry Dengler
Sent: Thursday, September 10, 2009 2:23 PM
To: [log in to unmask]
Subject: Re: [TN] Need clever comments

Actually he is probably from the Mk-46 era .

Jerry

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
Sent: Thursday, September 10, 2009 3:21 PM
To: [log in to unmask]
Subject: Re: [TN] Need clever comments

 pfffff.....handguns is nothing for Steve. He is probably more
comfortable with MK-50 onboard a P-3.
/Inge



----- Original Message ----- 
From: "Dwight Mattix" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, September 10, 2009 8:52 PM
Subject: Re: [TN] Need clever comments


> At 10:45 AM 9/10/2009, Stadem, Richard D. wrote:
>>Or hanging around the Laundromat with his .44 automatic.
>
> .44 automatic?  I didn't take Steve for a Desert Eagle sort of guy.
>
>
>>-----Original Message-----
>>From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
>>Sent: Thursday, September 10, 2009 11:25 AM
>>To: [log in to unmask]
>>Subject: Re: [TN] Need clever comments
>>
>>I will post a handful SEM images to Steve, so you get an idea what
it's
>>all
>>about.
>>It may take a while, because he is probably on the market place to buy
>>curtains and  wallpaper
>>for his new appartment. Or jogging. Or having a drink on the balcony.
>>/Inge
>>
>>
>>----- Original Message -----
>>From: "Inge" <[log in to unmask]>
>>To: <[log in to unmask]>
>>Sent: Thursday, September 10, 2009 5:10 PM
>>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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