My model, derived from IPC-TR-579, uses pi/4 * [(Tpwb + Dptv)^2 - (Dptv)^2]
as the area of influence of the epoxy on the PWB.  Tpwb is the PWB
thickness and Dptv is the drilled PTV diameter.
This is the area of a ring that battles against the PTV barrel's
cross-section in the stress equation.
It assumes a certain uniform heat penetration depth and [If I remember
correctly] doesn't model the extra heating gained by lots of innerlayer
copper pads (see Werner's post from 2/25/99).  Be careful if you're doing
transient analysis - perhaps you could calculate an 'epoxy/glass lumped
capacitance time constant' and base this penetration depth on the thermal
heating rate...

J.Felts

-----Original Message-----
From:   Michael Blattau [SMTP:[log in to unmask]]
Sent:   Monday, March 01, 1999 12:03 PM
To:     [log in to unmask]
Subject:        [TN] PTV/PTH model

What the most common thickness that is usually used for the resin rich
region surrounding a PTH (worst case/best case scenarios).  I'm working on
a 3-D Electro-Thermal FEA model.
Thanks,
Mike

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