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TechNet E-Mail Forum <[log in to unmask]>, Inge <[log in to unmask]>
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Fri, 11 Sep 2009 22:24:50 +0200
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10 nanometer Gold Argon sputtered at 0.05 mBar.
/Inge

----- Original Message ----- 
From: "Paul Edwards" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, September 11, 2009 9:53 PM
Subject: Re: [TN] Need clever comments


Inge,

Were the SEM samples in the photos coated with flash Au in sample prep or 
were the samples SEMed without coating?

Paul

Paul Edwards

Surface Art Engineering


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Hernefjord Ingemar
Sent: Friday, September 11, 2009 12:08 AM
To: [log in to unmask]
Subject: Re: [TN] Need clever comments

#4 the dark 'cake' in the middle is soldermask, the two bright objects are 
copper conductors, the rest is the FR-4 matrix
#5 all that you see in the center is soldermask, all the bright (over 
exposed)is copper

Inge



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dennis Fritz
Sent: fredag 11 september 2009 03:11
To: [log in to unmask]
Subject: Re: [TN] Need clever comments

Inge,



Do you have ANY explanation of the shape of the copper conductor in picture 
5?? I have no explanation, short of severe impact damage that will give the 
conductor shape.?? And, the laminate beneath the copper concuctor makes no 
sense - random fibers? damage from punching out a cross section rather than 
routing out the cross section?? A mystery to me.?



Denny Fritz


-----Original Message-----
From: stephengregory5849 <[log in to unmask]>
To: [log in to unmask]
Sent: Thu, Sep 10, 2009 7:05 pm
Subject: Re: [TN] Need clever comments



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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