Hi Inge,
A little late in the day, but I have your pics posted. They are here:
http://stevezeva.homestead.com/1.jpg
http://stevezeva.homestead.com/2.jpg
http://stevezeva.homestead.com/3.jpg
http://stevezeva.homestead.com/4.jpg
http://stevezeva.homestead.com/5.jpg
Yep, MK-46's were what we carried, at the tail-end we were starting to carry
AGM-84 Harpoons which made us P-3's more of a target IMHO. Also, although
it's not a concealed and carry, what makes me comfortable and gives me a
warm and fuzzy is a Barrett Model 82A1. It's almost like a hand grenade, you
only need to get close with that...heh
Steve
----- Original Message -----
From: "Inge" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, September 10, 2009 12:24 PM
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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