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Subject:	Lambda for LTCC silver vias
From:	"Ingemar Hernefjord (EMW)" <[log in to unmask]>
Reply To:	TechNet E-Mail Forum.
Date:	Mon, 13 Nov 2000 12:02:39 +0100
Content-Type:	text/plain
Parts/Attachments:	text/plain (18 lines)

Again a non- Copper question, not even polymer, I dare say LTCC because so many netters are in that game also.
Silver vias in a MCM are stacked, some make it perfect, others zigzag and some maybe something else. Many users, like us, mount chip in cavities, using the vias for thermal purpose. Now, for calculation of chip temperature, it's crucial that one put in right values on the different materials for simulations of temperature gradients. And the paste manufacturer use to get some values from ideal lab sets. If you use these values, you may not get the reality into your calculations. Silver particles may not spread equally, there can be minor material separations within the via, the zig-zag plays some role and many other factors based on morphologic facts and processing of LTCC etc. I have heard from somebody (the problem is I have forgotten who) that you can't put in LTCC suppliers ideal lambda value in the equation, the value can spread considerably. Know IBM Fishkill and others have done lots of jobs here, but searching is like finding a nail in a haystack. So, dear netters, so!
mebody out there who can refer to a report or who has an idea about silver via lambda variations? You can see what masters I see you all as being!

By the way, thanks for re on PIN diode qs, Steve Creswick, we will make ANSYS simulation before pill mounting. Will let you know off line later.

Ingemar Hernefjord
Microwave Systems

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