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March 2013

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Subject:
From:
Inge Hernefjord <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Inge Hernefjord <[log in to unmask]>
Date:
Sun, 3 Mar 2013 22:31:42 +0100
Content-Type:
text/plain
Parts/Attachments:
text/plain (70 lines)
Vladimir is right, make a SEM investigation to see if it really is
corrosion and not something else e.g. contaminated water or crystalized
solvent residues etc. And take some high resolution photos at varying
magnification.

I've been analyzing such things for years  and  I could guide you, as well
as Vladimir, but you'll certainly find assistance at some uni or
independent lab in your area. I am lazy, so instead of using own words, I
copied a page from a book, written by a guy in your country. I placed the
page in Dropbox/Reports../Analysis../Ramakrishnan. You have admission
already.

Good Luck

Inge


On 3 March 2013 00:29, Vladimir Igoshev <[log in to unmask]> wrote:

> It could be zillions of reasons and unless  proper FA is done you are
> NEVER  going to figure out what exactly caused the problem.
> ------Original Message------
> From: Ramakrishnan Saravanan
> Sender: TechNet
> To: [log in to unmask]
> ReplyTo: TechNet E-Mail Forum
> ReplyTo: Ramakrishnan Saravanan
> Subject: [TN] corrosion under Solder Mask
> Sent: Mar 2, 2013 18:13
>
> Dear all,
>
> We have received few MLBs from a contract supplier. The board was
> inspected and accepted for wiring. The assembly is for high reliability
> applications. We conformal coated, tested,thermal cycled and closed the
> package. We opened the package for some rework, we found corrosion under
> solder mask on some tracks.
>
> The corrosion is in the form of  blisters and localized. Center of the
> tracks or edge or localized and not covering the entire width of the tracks.
>
> What could be the reason for corrosion under solder mask ?. How to
> diagnosed for root cause analysis ? regards,
>
> R.Saravanan
>
>
> Regards,
>
> Vladimir
>
> SENTEC Testing Laboratory Inc.
> 11 Canadian Road, Unit 7.
> Scarborough, ON M1R 5G1
> Tel: (647) 495-8727
> Cell: (416) 899-1882
> www.sentec.ca
>
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