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Subject:
From:
Hernefjord Ingemar <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Hernefjord Ingemar <[log in to unmask]>
Date:
Fri, 11 Sep 2009 08:56:03 +0200
Content-Type:
text/plain
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text/plain (306 lines)
You mean #5, I suppose. It's part of the soldermask. All that you see in the center is soldermask.
Inge

 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Paul Edwards
Sent: fredag 11 september 2009 02:47
To: [log in to unmask]
Subject: Re: [TN] Need clever comments

Inge,

What is that 6um thick thing in #4?

Is that a piece of Cu on the SM?

Paul

Paul Edwards

Surface Art Engineering


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of stephengregory5849
Sent: Thursday, September 10, 2009 4:06 PM
To: [log in to unmask]
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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