Hi Gary,
Since IPC-TR-579 (dated Sep 1988), there certainly have been developments.
However, the basic findings hold today because they are basic
physics-of-failure conclusions.
In a message dated 02/27/2001 22:27:53, [log in to unmask] writes:
>Per the IPC-TR-579 ( dated Sep 1988 ), which was a round robin
>
>reliability evaluation of small diameter PTHs' in PWBs',
>
> The conclusions stated in section 2, items 5 & 6 were:
>
>
>
> Reliability decreases as the PTH diameter
>
>decreases.
>
> ( Hole sizes chosen for evaluation:
>
>.010", .0135", .016", .020" )
>
>
>
> PTH reliability decreases as the thickness
>
>of the PWB increases.
>
> ( Dielectrics chosen for evaluation:
>
>.030", .060", .090" )
>
>
>
>
>
> Two Questions:
>
>
>
>1. Since 1988, have processes &/or materials improved which would yield
better >results against the same test parameters, and if so, what industry
report would >demonstrate this ??
In plating, other than electroless copper, little has changed. However, we
now have dielectric PCB materials with significantly higher Tg's, which makes
a big difference.
>2. If these same testing parameters were applied to Buried Via
sub-composites, would >the results be the same, or would we find that the
encapsulated holes have a greater >survivability against the same testing
criteria ??
Buried vias have by tgheir very nature significantly shorther length than
PTHs--thus everything else being equal (which of course is not the case),
would have higher reliability. To my knowledge, no test program has been run
specifically for buried vias.
To get a more detailed understanding of the issues, you may want to attend my
workshop at IPC EXPO.
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], Website: www.engelmaier.com
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