Hi Werner,

Your comments to Chris were Interesting and I agree for the most part, but I
have a question with regard to the comment about radial barrel compression
during elevated temperatures. It is my understanding that as the board expands
in X & Y that the hole will also increase in diameter. Due to the
disproportionate difference in CTE I would expect that the barrel would be in
tension and not in compression (a hoop stress). This phenomena has been
demonstrated in the Physics classroom on many ocassions with Ring and Ball
apparatus. It's good to see you responding to some of these interesting
problems showing up on Technet. So what do you think about this analysis?

Les Connally,
[log in to unmask]

>  From: [log in to unmask], on 8/22/97 5:48 PM:
>  Hi Chris,
>  If you get the ITRI Report 'PWB Hole-To-Land Misregistration: Causes and
>  Reliability, Project Final Report", you may be a little careful in applying
>  the conclusions. I am not saying that the conclusions are wrong, but that
>  based on the test performed, the conclusions may be a stretch. From a
>  reliability point-of-view of the PTH barrel-to-land interconnect, the most
>  severe loading occurs during excursions to soldering temperatures not
>  thermal
>  cycling, even from -65 to +125C. That is because the largest thermal
>  expansion of the epoxy that causes the radial barrel compression and land
>  rotations occurs only at temperatures above Tg.
>
>  Werner Engelmaier
>  Engelmaier Associates, Inc.
>  Electronic Packaging, Interconnection and Reliability Consulting
>  23 Gunther Street
>  Mendham, NJ  07945  USA
>  Phone & Fax: 973-543-2747
>  E-mail: [log in to unmask]
>
>