Werner,

As I continue reading your message, I have not seen the post condition you
describe. How many instances have you and others seen and how do you relate
them to whatever thin core and prepreg materials selected for whatever layer
so compressed?

It all makes sense, but what's really going on here? Does this primarily
relate to "normal" MLB's say up to 60 layers on which I have worked or does
this more concern HDI type boards?

Earl

----- Original Message -----
From: "Werner Engelmaier" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, September 06, 2002 1:17 PM
Subject: Re: [TN] IPC-TM-650-2.6.8, Thermal stress, Plated Through Holes


> Hi Earl,
> ILS was previously referred to 'post-separation.'
> Actually, the forces are not exerted diagonally to the trace/pad to
conductor
> interface, but radially relative to the PTH barrel. This is the result of
the
> PTH barrel experiencing the same compression deformation as a submarine on
> diving; except, of course, that a submarine has its reinforcement ribs on
the
> inside and the PTH barrel on the outside [that's the functional and
> non-functional lands]. The traces resist the compressive movement of the
> barrel and failure can occur at the weakest of 3 links [ plating/flash
> interface, flash/foil interface, foil]. When the compressive deformation
is
> plastic for the copper barrel, hole separation occurs as the resin returns
to
> its former position on cooling.
>
> Werner
>
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