At 02:32 PM 9/10/2009, [log in to unmask] wrote:
>Steve already knows this now that he's a "Pennsyltuckian" - The .44
>cartridge is not a semi-automatic round, rather it is a revolver round. It
>does not have the ejector geometry along the base of the cartridge for
>ejecting the sent casing to chamber the next round in an automatic.
>Set them straight Steve !
except for oddballs like the Desert Eagle that are designed for
rimmed cartridges (.357 Mag and .44 Mag).
>----- Original Message -----
>From: "Dwight Mattix" <[log in to unmask]>
>To: <[log in to unmask]>
>Sent: Thursday, September 10, 2009 2:52 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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