Had a similar problem many years ago, think it was related to the
microsection technique, but can't remember for sure. Send me a photo and
maybe it'll jog my memory.
Robert E. Welch
Process Specialist
Waytec Electronics Corp.
Phone 804-237-6391 ext. 138
Fax 804-237-3048
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Colin
> Sent: Friday, November 20, 1998 5:04 AM
> To: [log in to unmask]
> Subject: [TN] (FAB)Pad lift & Cracking
>
>
> Technetters,
>
> I have an issue with the Mil spec MIL PRF 55110 F, which states
> that if you
> see lifted lands in the microsection, that you then inspect the lot 100%
> visually for seperation at 4X mag. and if not seen then the boards should
> be acceptable.
>
> I have to requalify using the 10 layer multilayer pattern of the
> MIL spec.,
> but have not been able to do so due to minute cracking of the resin under
> the pad, at the resin/glass interface, seen only at microsection at 200X.
> It is not visible to the naked eye, or at 4 X. (I have a photo if
> required,
> but have not attached it here due to bandwidth. besides, I don't want
> spammed!- mail me if you need a copy please)but the requalification people
> are insistent that as it is pad lift, although only seen under
> microsection, it must fail. So when is pad lift not pad lift according to
> the specification, or vice versa ?????
>
> The PCB's are "as received", having only been HASL'd. Several "fixes" have
> been tried, including reduction of copper plate thickness in the holes,
> change of bonding prepregs from 1080 to 2113/2116 to reduce the resin
> content, electroless copper instead of direct plate, higher Tg materials
> instead of standard FR4, change of HASL temperature and dwell,
> ductility of
> copper etc. (not all at once of course)
>
> I am at a loss to explain this, especially on the requalification issue,
> and am sure that several other fabricators have experienced this
> issue before.
> What was the outcome, and what was the answer?
>
> Hope someone can shed some light.
>
> Colin William
>
> "Opinions expressed above, are just that, and are my own, and do not
> reflect those of my employer"
>
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