Brad,
I don't know anyone that truly 'loves' the filling and capping process, but
I know plenty of folks that adore the additional freedom that the Type VII
via structure (see IPC-4761) provides for their complex circuit designs.
Admittedly, there was a time not too many years ago when CB-100 was 'the
only game in town'. That being said, few will disagree that it is a bear to
process.
If a given application doesn't require CB-100's conductivity, there are
non-conductive fill materials available today that exhibit a lower CTE,
higher Tg, and excellent Cu peel strength that are also relatively easy to
deposit and planarize in comparison to CB-100.
Stephen
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Brad Saunders
Sent: Thursday, September 07, 2006 11:18 AM
To: [log in to unmask]
Subject: Re: [TN] CB-100
Stephen,
I love PTH filling and copper capping. What did we ever do before There are
a good many materials to choose and not all are correct for all
configurations. The silver filled fillers when plannerized have an
outstanding copper peel strength. Both metal fillers and non metal fillers
need caution inside the PTH they are filling due to all of the CTE energies
essentially being transferred to Z axis, hence Tg is important. I would add
that voiding needs to be decreased or eliminated as under elevated and or
prolonged temps can be a source of root cause failure. Comes down to
ensuring that right fill material is used and a controlled process is
evoked. Lastly be certain aspect ratio of PTH before filling is properly
sized for fill material selected.
Brad
----- Original Message -----
From: Stephen Pierce<mailto:[log in to unmask]>
To: [log in to unmask]<mailto:[log in to unmask]>
Sent: Monday, August 14, 2006 2:57 PM
Subject: Re: [TN] CB-100
Ralph,
Without addressing CB-100 in particular, here are three important factors
to
consider when choosing a fill material for lead-free applications:
1) Z-axis CTE
2) Cu peel strength
3) Tg
Ideally, you want to minimize the CTE mismatch between the laminate and
the
fill material. Peel strength becomes key in order to prevent separation
between the Cu and epoxy resin if you will be plating directly to the
surface of the filled via. Generally speaking, a higher Tg is better.
Stephen
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ralph Richart
Sent: Saturday, August 12, 2006 7:03 AM
To: [log in to unmask]<mailto:[log in to unmask]>
Subject: [TN] CB-100
Does anybody have any background on silver filled vias and its suitability
for Lead Free Assembly? There are warnings in the literature about heat
excursions, and it seems that lead free assembly would make this worse. I
found only one email in the archives about delamination associated with
filled vias, but never found any answers as to wether the filled vias were
the cause, and/or what to do about it.
Any insights are appreciated.
thanks
Ralph
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