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Subject:	Re: Longitudinal PTH cracking
From:	Werner Engelmaier <[log in to unmask]>
Reply To:	TechNet E-Mail Forum.
Date:	Wed, 21 Oct 1998 20:20:47 EDT
Content-Type:	text/plain
Parts/Attachments:	text/plain (47 lines)

In a message dated 10/15/98 10:44:25, you wrote:
>     I have a thermal shock microsection of a multilayer PEC, FR4 with 20
>     æm min copper in the holes and an electroless nickel / gold finish.
>     There are longitudinal cracks evident in the PTH's. They are in the
>     nickel layer, I've never seen this before, at least not on PEC's. The
>     question is :
>     Should I be worried ??

Hi Chris,
This is a new one; I have never heard of your problem before.
I can only imagine that plating stresses in the plated nickel caused these
cracks—you should check on the plating conditions.
The loading of the PTV barrel walls will be radial and longitudinal during
soldering processes; the radial stresses may cause the existing cracks to
propagate.
This may get you into trouble if your layer-to-layer misregistration is large
enough for breakout to occur and thus the possibility of an electrical
discontinuity at some inner layer exists.

Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL  32174  USA
Phone: 904-437-8747, Fax: 904-437-8737
E-mail: [log in to unmask]

Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL  32174  USA
Phone: 904-437-8747, Fax: 904-437-8737
E-mail: [log in to unmask]

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