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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