Nope, that would be me....8-)
My eagle takes 357, 44 and 50 caliber
John Burke
(408) 515 4992
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dwight Mattix
Sent: Thursday, September 10, 2009 11:52 AM
To: [log in to unmask]
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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