just a few thoughts - although you don't say it, if we assume that the
silver filled holes are on the sub panel (5-12), then the normal production
process would be to electroless, then pattern plate this core, followed by
via fill. This will cause problems with the via fill, as the correct
sequence should be electroless, half panel plate, silver via fill, deburr,
full cure, panel or pattern plate. The via fill should be completely plated
over before black oxide.
If the via fill is done on holes L1-16, and the hole size is 0.008" then
either you are being hit by the hole size (min size 0.006") or aspect ratio
(6:1), in achieving a complete fill of the via, and this could cause air
expansion to delaminate the product during reflow.
Dougal Stewart
email: [log in to unmask]
phone: +44 1896 822204
mob: +44 7984 629667
www.pwbsolutions.co.uk
----- Original Message -----
From: "Arbour, Michel" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, March 10, 2003 6:45 PM
Subject: [TN] Problem of delamination with a silver filled board
> Hello technet.
> This is our first design using silver filled via. We have used two
different
> PCB fab. A total of 7 lots have been done and the yield seen at our pcb
fab
> house has not improved (15%).
> The major problem we have is generalized delamination after reflow (not
> localized) that seems to happen around layers 4-5. Our pcb. Fab is
currently
> investigating on the causes. Until now , no satisfactory explanations has
> been given to us.
> * Have some of you been faced against the same problem (delamination
> On silver filled via).
> * Any possible Causes/solutions
> * Any theories on the most probable cause (design/process/material
> compatibility ...)
>
> At this time, product release has been delayed.
> Your help in this matter would be appreciated.
>
> Board specification
> Dimension : 6.5X9 inch board. 0.070" thickness
> Sub sequential buildup Layer 5 to 12 with a total of 16 layers.
> Silver epoxy filled via using dupont CB100 .
> Qty of 7000 silver filled Via of 0.008"
> Qty of 1000 silver filled Via of 0.010"
> The populated boards has a very high thermal mass: 8 BGA . current of 96
> Amps.
> Impedance controlled and Burried capacitance
> Line/Spacing : 0.003" / 0.005"
>
> Best regards
> Michel Arbour
> Kontron
> Tel. : 450-437-4661 ext. 2287
>
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