We also have been correcting fab processing for years that is the root cause. We find that SEM/EDS analysis doesn't give a good quantitative value to compare the process to. If you need SEM / support let us know.
Terry Munson's iPhone
On Mar 3, 2013, at 4:31 PM, Inge Hernefjord <[log in to unmask]> wrote:
> 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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