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November 2006

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Subject:
From:
"valerie St. Cyr" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Fri, 17 Nov 2006 10:59:59 -0500
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Dear TechNetters ...

Ah, I can now rest. I found the reference I was looking for. It is in
IPC-4104, and so the scope is more narrow. For HDI materials there is a
stated preference of TMA. See:

IPC-4104 Specification for High Density Interconnect (HDI) and Microvia
Materials page 14, section: 3.9.15 Glass Transition Temperature: "The
preferred method for determining Tg is TMA extension (see IPC-TMA-650
Method 2.4.24.5, method A or B)." And 3.9.1.6 CTE above and Below Tg: "The
preferred method for determining CTE is IPC-TM-650, Method 2.4.24.5 method
A or B."

Method 2.4.24.5 is: "Glass Transition Temperature and Thermal Expansion of
Materials Used in High Density Interconnection (HDI) and Microvias - TMA
Method."

So, what do they mean by "HDI"?  Reading the document, in boils down to
the thinner surface layers, equal to or less than .006" thick, used in
conjunction with microvias, "these vias are the central characteristic of
HDI".

I thought I would send this along to close the loop, in case anyone else
wants some independent industry "body of experts" to reference, in
addition to the many good and thorough papers on this topic.

Rgds, Valerie


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