Hi Technet,

I've been thinking about what Mason said in regards to buried vias.
Intuitively, I would think that a thicker wall than normal would be stronger
and therefore more reliable.  However, some things aren't always intuitive.
Would thinner allow flexibility and thus better reliability?

Kind Regards

Ryan Grant
Advanced Technology Engineer
MCMS
(208) 898-1145
[log in to unmask]


> -----Original Message-----
> From: Mason Hu [SMTP:[log in to unmask]]
> Sent: Wednesday, February 28, 2001 2:48 PM
> To:   [log in to unmask]
> Subject:      Re: [TN] Small Hole PTH Reliability in PWB's
>
> Buried via will be different from PTH because it is typically filled with
> resin from the prepreg or some via fill material.
>
> Our finite element results suggest that there might be some increase in
> the
> strain in copper for buried via when filled with resin.  This is because
> resin has a low elastic modulus (does not help to bear stress) and a high
> CTE (help stretch the copper barrel even more).  We have observed failures
> in buried via, which prompted us to do this FEA study.
>
> Type II, HDI design has buried via from L2 to Ln-1.  The reliability of
> these vias should be looked into further.
>
> Regards,
>
> Mason
>
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