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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