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TechNet E-Mail Forum <[log in to unmask]>, Inge <[log in to unmask]>
Date:
Mon, 26 Oct 2009 21:28:55 +0100
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Manuel, tengo que preguntar esto tambien: is the problematic package the 
largest one?
I think we can concentrate on number 1 below:  I have seen MANY bad tinned 
leads. At the time when the world used Tin/Lead, there were few issues with 
bad finish, but when the pure tinning was introduced, bad finish appeared 
frequently. The cause was nearly always. that they put the Tin directly on 
the ferro containing lead, without any preparing processes. I've seen tin on 
rusty leads. So, there may be two factors:
a. the bad package has more mass than the others, got insufficient heat.
b. the bad package has poor tin finish.
 these two together caused insufficient temperature and wetting, which 
explains the non-melted paste particles and the non fulfilled wetting. Is it 
possible to check the lead finish quality on a non mounted package? If you 
find nothing wrong with tin thickness or nothing wrong with the tin-to-lead 
adhesion, we will go on to  help you, of course. Where are the TN superiors 
today?
/Inge


----- Original Message ----- 
From: "Manuel Castro" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, October 26, 2009 8:57 PM
Subject: Re: [TN] Questions


Inge,

The total build was for 70 pieces and 6-7 boards (as in today) had this
defect. The defect was observed on the same component part number (8 per)
but on random locations (3 per board). The size of the panel was 196x292 mm.
with an array of 2. The surface finish of the boards was Immersion Silver
and the chemistry used LF_WS (Alpha W819). The component plating under
suspect is Tin. The rest of the components on the defective assemblies are
good.  The board is fully populated with (QFP's, FPIC, SOIC's, Ind, cap,
res, etc). Stencil thickness utilized on this assembly was 5 mils laser cut.





Best regards,

Manuel Castro Jr.
Senior Process Engineering Manager
Office: (408) 964-3044
Fax: (408) 964-3001




On Mon, Oct 26, 2009 at 1:53 AM, Hernefjord Ingemar <
[log in to unmask]> wrote:

>  Manuel,
>
> there are several things that seem anomalous:
> 1. Looks like Copper is exposed at the end of some leads. Gives the
> impression of poor lead finish.
> 2. The solder spheres are not fully melted at the outermost part of the
> solder pad. Due to short top temp zone exposure?
> 3. Some solder pads are not wetted 100% or have dewetted. Looks like bad
> finish.
> 4. The solder mask is very close to the solder pads. Maybe you get solder
> mask contaminations on the solder pads.
> 5. The leads seem to be lifted during the soldering process.
> 6. Youd can't see the whole solder joint. Is the innermost part of the
> solder joints as bad as the outermost ones?
> 7. The colour of the non-wetted ( or de-wetted )part of the solder pads
> tells me that the solder pad finish is bad.
>
> I've never seen so many divergences at one and the same positions. A first
> look gives the impression that the solder paste was bad, that the lead
> finish was bad, that the solder pad finish was bad and that the soldering
> process was incorrect. Of course that's not a correct analysis. Question 
> is
> which one is the bad guy. I suspect that not even the TN gurus can decide
> without knowing a little more. E.g. what soldering process was used? What
> solder paste? How do the other component's SJs look like? What's the size 
> of
> the board? What mass? What pre-clean process? What stencil thickness? Etc.
>
> If I do my best guessing, I vote for local poor solder pad finish. I will
> enjoy reading the correct analysis later from someone of the 
> heavyweighters
> in the game...
>
> /Inge
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of stephengregory5849
> Sent: måndag 26 oktober 2009 02:41
> To: [log in to unmask]
> Subject: Re: [TN] Questions
>
> Hi Manuel,
>
> I'm sorry I didn't get your pictures posted sooner, but I have them up 
> now,
> and I'm posting everything to the TechNet for you. Your pictures are here:
>
> http://stevezeva.homestead.com/1a.JPG
>
> http://stevezeva.homestead.com/2a.JPG
>
> http://stevezeva.homestead.com/3a.JPG
>
> http://stevezeva.homestead.com/5a.JPG
>
> I posted the pictures that looked the best to illustrate your problem, a
> couple of pictures were out of focus and it was hard to see the problem.
>
> Were the IC's the only component that had this problem? That pretty much
> eliminates the solderpaste if it was. It makes it harder to figure out 
> when
> you say that it was random and only on three boards. What was the lead 
> finsh
> on the IC's? I've had a few problems with lead-free (tin) plating, but 
> it's
> been with connectors.
>
> Steve
>  ----- Original Message -----
>  From: Manuel Castro
>  To: [log in to unmask] ; Werner Engelmaier
>  Sent: Friday, October 23, 2009 7:00 PM
>  Subject: Re: Questions
>
>
>  Steven,
>
>  Attached are the photos of the issues. We run this assembly through our
> SMT oven and got a few boards (3) with this phenomenon at some of the 
> leads
> on this FPIC. The IC was the same part number but the location was random 
> on
> all 3 boards. The chemistry utilize during this build was Lead Free NC.
>
>  How do I send the email to everyone at the TechNet forum?...
>
>
>  Thank you All...
>
>
>  Best regards,
>
>  Manuel Castro Jr.
>  Senior Process Engineering Manager
>  [log in to unmask]
>  Office: (408) 964-3044
>  Fax: (408) 964-3001
>
>
>
>
>
>  On Fri, Oct 23, 2009 at 1:14 PM, Werner Engelmaier <[log in to unmask]>
> wrote:
>
>
>
>    Hi Manuel,
>    Steven is the GOOD guy doing the posting on his website-he recently
> changed jobs, e-mails, etc.; so it might be best to ask him directly.
>    Werner
>
>
>
>    -----Original Message-----
>    From: Manuel Castro <[log in to unmask]>
>    To: [log in to unmask]
>    Sent: Fri, Oct 23, 2009 1:11 pm
>    Subject: Questions
>
>
>    Hi Werner,
>
>    I love to follow all TechNet forum but I still don't know where the
> picture get posted from everyone that has an issue. Can you kindly tell me
> what the link is. Do we need a password to access the pictures. Lastly, if 
> I
> have an issue where do I post the picture to share with the team or whom 
> do
> I sent it to?
>
>
>
>    Best regards,
>
>    Manuel Castro Jr.
>    Senior Process Engineering Manager
>    [log in to unmask]
>    Office: (408) 964-3044
>    Fax: (408) 964-3001
>
>
>
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INTENDED AS A SUBSTITUTE FOR A WRITING.  Notwithstanding the Uniform 
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hereinabove, this e-mail message its contents, and any attachments hereto 
are not intended to represent an offer or acceptance to enter into a 
contract and are not otherwise intended to bind the sender, Sanmina-SCI 
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